<SEC-DOCUMENT>0001193125-19-148119.txt : 20190515
<SEC-HEADER>0001193125-19-148119.hdr.sgml : 20190515
<ACCEPTANCE-DATETIME>20190515170213
ACCESSION NUMBER:		0001193125-19-148119
CONFORMED SUBMISSION TYPE:	10-Q
PUBLIC DOCUMENT COUNT:		95
CONFORMED PERIOD OF REPORT:	20190331
FILED AS OF DATE:		20190515
DATE AS OF CHANGE:		20190515

FILER:

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			X4 Pharmaceuticals, Inc
		CENTRAL INDEX KEY:			0001501697
		STANDARD INDUSTRIAL CLASSIFICATION:	BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
		IRS NUMBER:				273181608
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		10-Q
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-38295
		FILM NUMBER:		19829423

	BUSINESS ADDRESS:	
		STREET 1:		955 MASSACHUSETTS AVENUE
		STREET 2:		4TH FLOOR
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02139
		BUSINESS PHONE:		857-529-8300

	MAIL ADDRESS:	
		STREET 1:		955 MASSACHUSETTS AVENUE
		STREET 2:		4TH FLOOR
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02139

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Arsanis, Inc.
		DATE OF NAME CHANGE:	20100920
</SEC-HEADER>
<DOCUMENT>
<TYPE>10-Q
<SEQUENCE>1
<FILENAME>d726255d10q.htm
<DESCRIPTION>10-Q
<TEXT>
<HTML><HEAD>
<TITLE>10-Q</TITLE>
</HEAD>
 <BODY BGCOLOR="WHITE">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="line-height:1.0pt;margin-top:0pt;margin-bottom:0pt;border-bottom:1px solid #000000">&nbsp;</P>
<P STYLE="line-height:3.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000">&nbsp;</P> <P STYLE="margin-top:4pt; margin-bottom:0pt; font-size:18pt; font-family:Times New Roman" ALIGN="center"><B>UNITED STATES </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:18pt; font-family:Times New Roman" ALIGN="center"><B>SECURITIES AND EXCHANGE COMMISSION </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B>Washington, D.C. 20549 </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center>
<P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:18pt; font-family:Times New Roman" ALIGN="center"><B>FORM <FONT
STYLE="white-space:nowrap">10-Q</FONT> </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center>
<P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>(Mark One) </B></P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:12pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B></B>&#9746;<B></B><B></B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman; " ALIGN="left"><B>QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
</B></P></TD></TR></TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>For the quarterly period ended March&nbsp;31, 2019 </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>or </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:12pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B></B>&#9744;<B></B><B></B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman; " ALIGN="left"><B>TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
</B></P></TD></TR></TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>For the transition period from
<U>&nbsp;&nbsp;&nbsp;&nbsp;</U><U>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</U><U>&nbsp;&nbsp;&nbsp;&nbsp;</U><U>&nbsp;&nbsp;&nbsp;&nbsp;</U> to
<U>&nbsp;&nbsp;&nbsp;&nbsp;</U><U>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</U><U>&nbsp;&nbsp;&nbsp;&nbsp;</U><U>&nbsp;&nbsp;&nbsp;&nbsp;</U> </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>Commission File Number: <FONT STYLE="white-space:nowrap">001-38295</FONT> </B></P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center> <P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:24pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Exact name of registrant as specified in its charter) </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center>
<P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:8pt" ALIGN="center">


<TR>
<TD WIDTH="50%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="48%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" ALIGN="center"><B>Delaware</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><B><FONT STYLE="white-space:nowrap">27-3181608</FONT></B></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="top" ALIGN="center"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>(State or other jurisdiction of</B></P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>incorporation or organization)</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>(I.R.S. Employer</B></P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>Identification No.)</B></P></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" ALIGN="center"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>955 Massachusetts Avenue, 4th Floor</B></P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>Cambridge, Massachusetts</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center"><B>02139</B></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="top" ALIGN="center"><B>(Address of principal executive offices)</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><B>(Zip Code)</B></TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(857) <FONT STYLE="white-space:nowrap">529-8300</FONT> </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>(Registrant&#146;s telephone number, including area code) </B></P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center> <P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Securities registered pursuant to Section&nbsp;12(b) of the Act: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:8pt" ALIGN="center">


<TR>
<TD WIDTH="34%"></TD>
<TD VALIGN="bottom"></TD>
<TD WIDTH="32%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="32%"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom" NOWRAP ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>Title of each class</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>Trading Symbol(s)</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>Name of each exchange on which registered</B></P></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" ALIGN="center"><B>Common Stock</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><B>XFOR</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><B>The Nasdaq Capital Market</B></TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Indicate by check mark whether the registrant (1)&nbsp;has filed all reports required to be filed by Section&nbsp;13 or
15(d)&nbsp;of the Securities Exchange Act of 1934 during the preceding 12&nbsp;months (or for such shorter period that the registrant was required to file such reports), and (2)&nbsp;has been subject to such filing requirements for the past
90&nbsp;days.&nbsp;&nbsp;&nbsp;&nbsp;Yes&nbsp;&nbsp;&#9746;&nbsp;&nbsp;&nbsp;&nbsp;No&nbsp;&nbsp;&#9744; </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Indicate by check mark whether the registrant
has submitted electronically every Interactive Data File required to be submitted pursuant to Rule&nbsp;405 of Regulation <FONT STYLE="white-space:nowrap">S-T</FONT> (&#167; 232.405 of this chapter) during the preceding 12&nbsp;months (or for such
shorter period that the registrant was required to submit such files).&nbsp;&nbsp;&nbsp;&nbsp;Yes&nbsp;&nbsp;&#9746;&nbsp;&nbsp;&nbsp;&nbsp;No&nbsp;&nbsp;&#9744; </P> <P STYLE="margin-top:0pt;margin-bottom:0pt;page-break-before:always"></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a <FONT STYLE="white-space:nowrap">non-accelerated</FONT>
filer, a smaller reporting company, or an emerging growth company. See the definitions of &#147;large accelerated filer,&#148; &#147;accelerated filer,&#148; &#147;smaller reporting company,&#148; and &#147;emerging growth company&#148; in <FONT
STYLE="white-space:nowrap">Rule&nbsp;12b-2</FONT> of the Exchange Act. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="16%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="60%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="20%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="1%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom">Large&nbsp;accelerated&nbsp;filer</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&#9744;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">Accelerated&nbsp;filer</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&#9744;</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom"><FONT STYLE="white-space:nowrap">Non-accelerated</FONT> filer</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&#9746;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">Smaller&nbsp;reporting&nbsp;company</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&#9746;</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">Emerging&nbsp;growth&nbsp;company</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&#9746;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period
for complying with any new or revised financial accounting standards provided pursuant to Section&nbsp;13(a)&nbsp;of the Exchange Act.&nbsp;&nbsp;&#9746; </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Indicate by check mark whether the registrant is a shell company (as defined in Rule <FONT STYLE="white-space:nowrap">12b-2</FONT> of the Exchange
Act).&nbsp;&nbsp;&nbsp;&nbsp;Yes&nbsp;&nbsp;&#9744;&nbsp;&nbsp;&nbsp;&nbsp;No&nbsp;&nbsp;&#9746; </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As of May&nbsp;5, 2019, the registrant had 12,420,778
shares of common stock outstanding. </P> <P STYLE="font-size:10pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P> <P STYLE="line-height:1.0pt;margin-top:0pt;margin-bottom:0pt;border-bottom:1px solid #000000">&nbsp;</P>
<P STYLE="line-height:3.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000">&nbsp;</P>
</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><A NAME="toc"></A>X4 Pharmaceuticals, Inc. </B></P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="7%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="90%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3"><A HREF="#tx726255_1a">EXPLANATORY NOTE </A></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center">3</TD>
<TD NOWRAP VALIGN="top">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3"><A HREF="#tx726255_2">CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS</A></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center">3</TD>
<TD NOWRAP VALIGN="top">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="top"></TD>
<TD VALIGN="top"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><A HREF="#tx726255_1">PART I: FINANCIAL INFORMATION </A></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="top"></TD>
<TD VALIGN="top"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:2.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Item&nbsp;1.</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_3">FINANCIAL STATEMENTS</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">5</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_4">Condensed Consolidated Balance Sheets (unaudited) as of March&nbsp;
31, 2019 and December&nbsp;31, 2018</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">5</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_5">Condensed Consolidated Statements of Operations (unaudited) for the Three Months
 Ended March&nbsp;31, 2019 and 2018</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">6</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_6">Condensed Consolidated Statements of Comprehensive Loss (unaudited) for the Three
 Months Ended March&nbsp;31, 2019 and 2018</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">7</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_7">Condensed Consolidated Statements of Convertible Preferred Stock, Redeemable Common
Stock and Stockholders&#146; Equity (Deficit) (unaudited) for the Three Months Ended March&nbsp;31, 2019 and 2018</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">8</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_8">Condensed Consolidated Statements of Cash Flows (unaudited) for the Three Months
 Ended March&nbsp;31, 2019 and 2018</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">9</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_9">Notes to Condensed Consolidated Financial Statements
(unaudited)</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">10</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:2.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Item&nbsp;2.</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_10">MANAGEMENT&#146;S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF
 OPERATIONS</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">39</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:2.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Item&nbsp;3.</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_11">QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">53</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:2.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Item&nbsp;4.</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_12">CONTROLS AND PROCEDURES</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">53</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><A HREF="#tx726255_13">PART II: OTHER INFORMATION</A></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="top"></TD>
<TD VALIGN="top"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:2.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Item&nbsp;1.</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_14">LEGAL PROCEEDINGS</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">54</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:2.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Item&nbsp;1A.</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_15">RISK FACTORS</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">54</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:2.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Item&nbsp;2.</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_16">UNREGISTERED SALES OF EQUITY SECURITIES AND USE OF PROCEEDS</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">54</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:2.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Item&nbsp;3.</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_17">DEFAULTS UPON SENIOR SECURITIES</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">54</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:2.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Item&nbsp;4.</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_18">MINE SAFETY DISCLOSURES</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">54</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:2.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Item&nbsp;5.</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_19">OTHER INFORMATION</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">54</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:2.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Item&nbsp;6.</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_20">EXHIBITS</A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">55</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><A HREF="#tx726255_21">SIGNATURES </A></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">57</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
</TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">2 </P>

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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><A NAME="tx726255_1a"></A>EXPLANATORY NOTE </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On March&nbsp;13, 2019, X4 Pharmaceuticals, Inc. (formerly Arsanis, Inc), or the Company, completed its business combination in accordance with the terms of
the Agreement and Plan of Merger, dated as of November&nbsp;26, 2018, as amended on December&nbsp;20, 2018 and March&nbsp;8, 2019, or the Merger Agreement, by and among the Company, X4&nbsp;Therapeutics, Inc. (formerly X4&nbsp;Pharmaceuticals, Inc.)
and Artemis AC Corp., a Delaware corporation and a wholly owned subsidiary of the Company, or the Merger Sub, pursuant to which, among other matters, Merger Sub merged with and into X4&nbsp;Therapeutics, Inc., with X4&nbsp;Therapeutics, Inc.
continuing as a wholly owned subsidiary of the Company and the surviving corporation of the merger, or the Merger. Following the Merger, on March&nbsp;13, 2019, the Company effected a
<FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">1-for-6</FONT></FONT> reverse stock split of its common stock, or the Reverse Stock Split, and changed its name to &#147;X4 Pharmaceuticals, Inc.&#148; Following the completion of the
Merger, the business conducted by the Company became primarily the business conducted by X4&nbsp;Therapeutics, Inc., which is a clinical-stage biopharmaceutical company focused on the discovery, development and commercialization of novel
therapeutics for the treatment of rare diseases. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Unless otherwise noted, all references to common stock share and per share amounts in this Quarterly
Report on Form <FONT STYLE="white-space:nowrap">10-Q</FONT> have been retroactively adjusted to reflect the conversion of shares in the Merger based on an Exchange Ratio of 0.5702 and, the Reverse Stock Split. As used herein, the words &#147;the
Company,&#148; &#147;we,&#148; &#147;us,&#148; and &#147;our&#148; refer to, for periods following the Merger, X4&nbsp;Pharmaceuticals, Inc. (formerly Arsanis, Inc.), together with is direct and indirect subsidiaries, and for periods prior to the
Merger, X4&nbsp;Therapeutics, Inc. (formerly X4 Pharmaceuticals, Inc.), and its direct and indirect subsidiaries, as applicable. In addition, the word &#147;Arsanis&#148; refers to the Company prior to the completion of the Merger, and we sometimes
refer to X4 Therapeutics, Inc. as &#147;X4.&#148; </P> <P STYLE="margin-top:24pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><A NAME="tx726255_2"></A>CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS
</B></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">This quarterly report includes forward-looking statements within the meaning of Section&nbsp;27A of the Securities Act of 1933, as amended, which we
refer to as the Securities Act, and Section&nbsp;21E of the Securities Exchange Act of 1934, as amended, which we refer to as the Exchange Act, that relate to future events or to our future operations or financial performance.&nbsp;Any
forward-looking statement involves known and unknown risks, uncertainties and other factors that may cause our actual results, levels of activity, performance or achievements to differ materially from any future results, levels of activity,
performance or achievements expressed or implied by such forward-looking statement. Forward-looking statements include statements, other than statements of historical fact, about, among other things: </P>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the progress, scope, cost, duration or results of our development activities, nonclinical studies and clinical
trials of <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">mavorixafor&nbsp;(X4P-001),&nbsp;X4P-002&nbsp;and&nbsp;X4P-003&nbsp;or</FONT></FONT></FONT> any of our other product candidates or programs,
such as the target indication(s) for development, the size, design, population, conduct, cost, objective or endpoints of any clinical trial, or the timing for initiation or completion of or availability of results from any clinical trial (including
our planned trials for mavorixafor in WHIM syndrome, severe congenital neutropenia, or SCN, and Waldenstr&ouml;m macroglobulinemia, or WM), for submission or approval of any regulatory filing or for meeting with regulatory authorities;
</P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the potential benefits that may be derived from any of our product candidates; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the timing of and our ability to obtain and maintain regulatory approval of our existing product candidates, any
product candidates that we may develop, and any related restrictions, limitations, or warnings in the label of any approved product candidates; </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">our future operations, financial position, revenues, costs, expenses, uses of cash, capital requirements or our
need for additional financing; and </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">our strategies, prospects, plans, expectations or objectives. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Words such as, but not limited to, &#147;believe,&#148; &#147;expect,&#148; &#147;anticipate,&#148; &#147;estimate,&#148;
&#147;forecast,&#148; &#147;intend,&#148; &#147;may,&#148; &#147;plan,&#148; &#147;potential,&#148; &#147;predict,&#148; &#147;project,&#148; &#147;targets,&#148; &#147;likely,&#148; &#147;will,&#148; &#147;would,&#148; &#147;could,&#148;
&#147;should,&#148; &#147;continue,&#148; &#147;scheduled&#148; and similar expressions or phrases, or the negative of those expressions or phrases, are intended to identify forward-looking statements, although not all forward-looking statements
contain these identifying words. Although we believe that we have a reasonable basis for each forward-looking statement contained in this report, we caution you that these statements are based on our estimates or projections of the future that are
subject to known and unknown risks and uncertainties and other important factors that may cause our actual results, level of activity, performance, experience or achievements to differ materially from those expressed or implied by any
forward-looking statement. These risks, uncertainties and other factors are described in greater detail under the caption &#147;Risk Factors&#148; contained in our Annual Report on Form <FONT STYLE="white-space:nowrap">10-K</FONT> for the fiscal
year ended December&nbsp;31, 2018, as updated by our Current Report on Form <FONT STYLE="white-space:nowrap">8-K</FONT> filed on April&nbsp;11, 2019 and our subsequent filings under the Exchange Act, and in other filings that we make with the
Securities and Exchange Commission, or SEC. As a result of the risks and uncertainties, the results or events indicated by the forward-looking statements may not occur. We caution you not to place undue reliance on any forward-looking statement.
</P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">3 </P>

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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">In addition, any forward-looking statement in this quarterly report represents our views
only as of the date of this quarterly report and should not be relied upon as representing our views as of any subsequent date. We anticipate that subsequent events and developments may cause our views to change. Although we may elect to update
these forward-looking statements publicly at some point in the future, we specifically disclaim any obligation to do so, except as required by applicable law. Our forward-looking statements do not reflect the potential impact of any future
acquisitions, mergers, dispositions, joint ventures or investments we may make. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">4 </P>

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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><A NAME="tx726255_1"></A>PART I: FINANCIAL INFORMATION </B></P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="8%" VALIGN="top" ALIGN="left"><B><A NAME="tx726255_3"></A>Item&nbsp;1.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>FINANCIAL STATEMENTS </B></P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><A NAME="tx726255_4"></A>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>CONDENSED CONSOLIDATED BALANCE SHEETS </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(In thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="83%"></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>March&nbsp;31,</B><br><B>2019</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>December&nbsp;31,</B><br><B>2018</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><B>Assets</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Current assets:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Cash and cash equivalents</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">22,299</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">8,134</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Research and development incentive receivable</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,552</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Prepaid expenses and other current assets</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2,372</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,205</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total current assets</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">26,223</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">9,339</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Property and equipment, net</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">271</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">241</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Intangible assets</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4,900</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Goodwill</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">27,407</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">Right-of-use</FONT></FONT>
assets</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2,705</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Restricted cash</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">947</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">364</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Other assets</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">96</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total assets</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">62,549</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">9,944</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><B>Liabilities, Convertible Preferred Stock, Redeemable Common Stock and Stockholders&#146;
Equity&nbsp;(Deficit)</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Current liabilities:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Accounts payable</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">6,132</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">2,969</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Accrued expenses</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4,179</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">3,251</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Current portion of lease liability</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">841</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Current portion of long-term debt</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">5,298</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,687</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total current liabilities</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">16,450</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">7,907</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Preferred stock warrant liability</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4,947</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Long-term debt, including accretion, net of discount and current portion</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">13,365</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">8,145</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Deferred rent</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">417</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Lease liability</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">3,275</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Other liabilities</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">18</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">205</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total liabilities</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">33,108</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">21,621</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Commitments and contingencies (Note&nbsp;9)</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Convertible preferred stock (Series Seed, A and B), $0.001 par value; 10,000,000 and 59,413,523
shares authorized as of March&nbsp;31, 2019 and December&nbsp;31, 2018, respectively; 0 and 40,079,567 shares issued and outstanding as of March&nbsp;31, 2019 and December&nbsp;31, 2018, respectively</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">64,675</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Redeemable common stock, $0.001 par value; 0 and 107,364 shares issued and outstanding as of
March&nbsp;31, 2019 and December&nbsp;31, 2018, respectively</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">734</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Stockholders&#146; equity (deficit):</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Common stock, $0.001 par value. 33,333,333 and 11,070,776 shares authorized as of March&nbsp;31,
2019 and December&nbsp;31, 2018, respectively: 6,724,511 and 351,652 shares issued and outstanding as of March&nbsp;31, 2019 and December&nbsp;31, 2018, respectively</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">7</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Additional <FONT STYLE="white-space:nowrap">paid-in</FONT> capital</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">119,521</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2,151</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Accumulated other comprehensive income</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">23</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Accumulated deficit</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(90,110</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(79,237</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:7.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total stockholders&#146; equity (deficit)</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">29,441</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(77,086</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:7.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total liabilities, convertible preferred stock, redeemable common stock and stockholders&#146;
equity&nbsp;(deficit)</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">62,549</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">9,944</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><I>The accompanying unaudited notes are an integral part of these condensed consolidated financial statements.
</I></P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">5 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><A NAME="tx726255_5"></A>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(In thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="83%"></TD>
<TD VALIGN="bottom" WIDTH="3%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="3%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Three Months Ended<BR>March&nbsp;31,</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2019</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2018</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Operating expenses:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Research and development</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">5,655</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">4,744</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">General and administrative</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4,783</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,366</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total operating expenses</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">10,438</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">6,110</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Loss from operations</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(10,438</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(6,110</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Other income (expense):</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Interest income</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">69</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">69</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Interest expense</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(399</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(169</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Change in fair value of preferred stock warrant liability</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(288</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(592</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Change in fair value of derivative liability</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">183</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(565</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total other income (expense), net</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(435</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(1,257</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net loss</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(10,873</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(7,367</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Accruing dividends on Series A convertible preferred stock</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(592</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(740</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net loss attributable to common stockholders</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(11,465</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(8,107</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net loss per share attributable to common stockholders&#151;basic and diluted</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(6.67</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(17.70</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Weighted average common shares outstanding&#151;basic and diluted</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,717,808</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">457,971</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><I>The accompanying unaudited notes are an integral part of these condensed consolidated financial statements.
</I></P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">6 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><A NAME="tx726255_6"></A>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(In thousands) </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="85%"></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Three Months Ended<BR>March&nbsp;31,</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2019</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2018</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net loss</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(10,873</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(7,367</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Other comprehensive gain</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Currency translation adjustments</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">23</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total comprehensive loss</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(10,850</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(7,367</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><I>The accompanying unaudited notes are an integral part of these condensed consolidated financial statements
</I></P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">7 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><A NAME="tx726255_7"></A>X4 PHARMACEUTICALS, INC </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK, REDEEMABLE COMMON </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>STOCK AND STOCKHOLDERS&#146; EQUITY (DEFICIT) </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(In thousands, except share amounts) </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="67%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom"></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Series&nbsp;Seed, A and B</B><br><B>Convertible Preferred</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Redeemable</B><br><B>Common Stock</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Common Stock</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ROWSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Additional</B><br><B><FONT STYLE="white-space:nowrap">Paid-In</FONT></B><br><B>Capital</B></TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ROWSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>AOCI</B></TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ROWSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Accumulated</B><br><B>Deficit</B></TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ROWSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Total</B><br><B>Stockholders&#146;</B><br><B>(Deficit)&nbsp;Equity</B></TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Shares</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Amount</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Shares</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Amount</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Shares</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Amount</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><B>Balances at December&nbsp;31, 2018</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">40,079,567</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">64,675</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">107,364</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">734</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">351,652</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">2,151</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(79,237</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(77,086</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Conversion of redeemable common stock into common stock</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(107,364</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(734</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">107,364</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">733</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">734</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Conversion of convertible preferred shares into common stock</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(40,079,567</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(64,675</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">3,808,430</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">64,671</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">64,675</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Exchange of common stock in connection with Merger</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2,440,582</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">45,539</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">45,541</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Fair value of replacement equity awards</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">817</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">817</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Reclassification of warrant liability to permanent equity</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">5,235</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">5,235</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Exercise of stock options</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">16,483</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">113</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">113</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Stock-based compensation expense</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">262</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">262</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net loss</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">23</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(10,873</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(10,850</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><B>Balances at March&nbsp;31, 2019</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">6,724,511</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">7</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">119,521</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">23</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(90,110</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">29,441</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="43%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom"></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
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<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Series&nbsp;Seed, A and B</B><br><B>Convertible Preferred</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Redeemable</B><br><B>Common Stock</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Common Stock</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ROWSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Additional</B><br><B><FONT STYLE="white-space:nowrap">Paid-In</FONT></B><br><B>Capital</B></TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ROWSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>AOCI</B></TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ROWSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Accumulated</B><br><B>Deficit</B></TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ROWSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Total</B><br><B>Stockholders&#146;</B><br><B>(Deficit)</B></TD>
<TD VALIGN="bottom" ROWSPAN="2">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Shares</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Amount</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Shares</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Amount</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Shares</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Amount</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><B>Balances at December&nbsp;31, 2017</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">38,018,968</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">60,903</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">107,364</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">734</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">350,607</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">1,385</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(45,930</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(44,545</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Repurchase of Series Seed convertible preferred stock, net of issuance costs of&nbsp;$1</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(598,975</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(517</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(22</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(22</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Stock-based compensation expense</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">128</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">128</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net loss</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(7,367</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(7,367</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><B>Balances at March&nbsp;31, 2018</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">37,419,993</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">60,386</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">107,364</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">734</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">350,607</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">1,513</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(53,319</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(51,806</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><I>The accompanying unaudited notes are an integral part of these condensed consolidated financial statements.
</I></P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">8 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><A NAME="tx726255_8"></A>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(In thousands) </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="85%"></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Three Months Ended<BR>March&nbsp;31,</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2019</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2018</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><B>Cash flows from operating activities:</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net loss</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(10,873</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(7,367</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Adjustments to reconcile net loss to net cash used in operating activities:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Stock-based compensation expense</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">262</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">128</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Depreciation expense</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">20</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">26</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Non-cash lease expense</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">119</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><FONT STYLE="white-space:nowrap">Non-cash</FONT> interest expense</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">153</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">27</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Change in fair value of preferred stock warrant liability</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">288</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">592</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Change in fair value of derivative liability</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(183</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">565</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Changes in operating assets and liabilities:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Prepaid expenses and other current assets</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(595</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">170</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Accounts payable</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,332</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(563</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Accrued expenses</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(2,072</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">240</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Operating lease liabilities</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(201</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net cash used in operating activities</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(11,750</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(6,182</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><B>Cash flows from investing activities:</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Cash and restricted cash acquired in connection with the Merger</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">26,406</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net cash provided by investing activities</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">26,406</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><B>Cash flows from financing activities:</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Proceeds from exercise of stock options</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">113</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Repurchase of Series Seed convertible preferred stock</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(1,126</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Repayments of borrowings under loan and security agreement</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(500</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Payments of issuance costs of convertible preferred stock</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(34</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net cash provided by (used in) financing activities</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">113</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(1,660</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Effect of exchange rate changes on cash, cash equivalents and restricted cash</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(21</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><B>Net increase (decrease) in cash, cash equivalents and restricted cash</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">14,748</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(7,842</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Cash, cash equivalents and restricted cash at beginning of period</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">8,498</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">27,048</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Cash, cash equivalents and restricted cash at end of period</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">23,246</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">19,206</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><B>Supplemental disclosure of cash flow information:</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Cash paid for interest</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">243</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">146</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><B>Supplemental disclosure of <FONT STYLE="white-space:nowrap">non-cash</FONT> investing and
financing activities:</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Conversion of convertible preferred stock into common stock</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">64,675</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Conversion of redeemable common stock into common stock</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">734</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Conversion of convertible preferred stock warrants into common stock warrants</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">5,235</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom"><B>&nbsp;</B></TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right"><B>&#151;&nbsp;&nbsp;</B></TD>
<TD NOWRAP VALIGN="bottom"><B>&nbsp;</B></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Fair value of net assets acquired in Merger</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">46,358</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><I>The accompanying unaudited notes are an integral part of these condensed consolidated financial statements.
</I></P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">9 </P>

</DIV></Center>


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<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><A NAME="tx726255_9"></A>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>1.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>Nature of the Business and Basis of Presentation </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">X4 Pharmaceuticals, Inc. (formerly Arsanis, Inc.), together with its subsidiaries (the &#147;Company&#148;), is a clinical-stage biotechnology research and
development company focused on the development of novel therapeutics for the treatment of rare diseases. The Company is headquartered in Cambridge, Massachusetts. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by
competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with governmental regulations and the ability to secure additional capital to fund operations. Drug candidates currently
under development will require extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel, and infrastructure and extensive
compliance-reporting capabilities. Even if the Company&#146;s drug development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The accompanying condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United
States of America (&#147;GAAP&#148;) and include the accounts of the Company and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Merger with Arsanis </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On November&nbsp;26, 2018,
Arsanis, Inc., a publicly held Delaware corporation (&#147;Arsanis&#148;), Artemis AC Corp., a Delaware corporation and a wholly owned subsidiary of Arsanis (&#147;Merger Sub&#148;), and X4 Therapeutics, Inc. (&#147;X4&#148;) entered into an
Agreement and Plan of Merger, as amended on December&nbsp;20, 2018 and March&nbsp;8, 2019 (the &#147;Merger Agreement&#148;), pursuant to which the Merger Sub merged with and into X4, with X4 surviving the merger as a wholly owned subsidiary of
Arsanis. The transactions described in the foregoing sentence may be referred to in these condensed consolidated financial statements as &#147;the Merger.&#148; </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The transaction was accounted for as a reverse merger in accordance with GAAP. Under this method of accounting, X4 was deemed to be the accounting acquirer
for financial reporting purposes. This determination was primarily based on the facts that, immediately following the Merger: (i)&nbsp;the Company&#146;s stockholders own a substantial majority of the voting rights in the combined organization,
(ii)&nbsp;the Company designated a majority of the members of the initial board of directors of the combined organization and (iii)&nbsp;the Company&#146;s senior management hold all key positions in the senior management of the combined
organization. Accordingly, for accounting purposes, the business combination was treated as the equivalent of X4 issuing stock to acquire the net assets of Arsanis. As a result, as of the closing date of the Merger, the net assets of Arsanis were
recorded at their acquisition-date fair values in the financial statements of the Company and the reported operating results prior to the business combination will be those of the Company. In addition, transaction costs incurred by the Company in
connection with the business combination will be expensed as incurred. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On March&nbsp;13, 2019, Arsanis, X4 and Merger Sub completed the Merger pursuant
to the terms of the Merger Agreement. Pursuant to the terms of the Merger Agreement, each outstanding share of X4&#146;s common stock and preferred stock was exchanged for 0.5702 shares of Arsanis&#146;s common stock (the &#147;Exchange
Ratio&#148;). In addition, all outstanding options exercisable for common stock and warrants exercisable for convertible preferred stock of X4 became options and warrants exercisable for the same number of shares of common stock of Arsanis
multiplied by the Exchange Ratio. In connection with the Merger, X4 changed its name to X4 Therapeutics, Inc. Following the closing of the Merger, X4 Therapeutics, Inc. is a wholly owned subsidiary of the Company. which changed its name to X4
Pharmaceuticals, Inc. As used herein, the words &#147;the Company&#148; refers to, for periods following the Merger, X4 Pharmaceuticals, Inc. (formerly Arsanis, Inc.), together with is direct and indirect subsidiaries, and for periods prior to the
Merger, X4 Therapeutics, Inc. (formerly X4 Pharmaceuticals, Inc.), and its direct and indirect subsidiaries, as applicable. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Immediately following the
Merger, stockholders of X4 owned approximately 63.7% of the combined organization&#146;s outstanding common stock. On March&nbsp;14, 2019, the combined organization&#146;s common stock began trading on The Nasdaq Capital Market under the ticker
symbol &#147;XFOR.&#148; </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Reverse Stock Split </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On March&nbsp;13, 2019, immediately following the closing of the Merger, the Company effected a
<FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">6-for-1</FONT></FONT> reverse stock split of its common stock (the &#147;Reverse Stock Split&#148;). Accordingly, all share and per share amounts for all periods presented in the
accompanying condensed consolidated financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect the Reverse Stock Split. No fractional shares were issued in connection with the Reverse Stock Split. Unless
otherwise noted, all references to common stock share and per share amounts have also been adjusted to reflect the exchange ratio of 0.5702. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">10 </P>

</DIV></Center>


<p Style='page-break-before:always'>
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<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Going Concern Assessment </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In accordance with Accounting Standards Update (&#147;ASU&#148;) <FONT STYLE="white-space:nowrap">No.&nbsp;2014-15,</FONT><I> Disclosure of Uncertainties about
an Entity&#146;s Ability to Continue as a Going Concern (Subtopic <FONT STYLE="white-space:nowrap">205-40)</FONT></I> , the Company has evaluated whether there are certain conditions and events, considered in the aggregate, that raise substantial
doubt about the Company&#146;s ability to continue as a going concern within one year after the date that the consolidated financial statements are issued. As of May&nbsp;14, 2019, the issuance date of these condensed consolidated financial
statements, the Company expects that its cash and cash equivalents, including approximately $79&nbsp;million of net proceeds from the public sale of common stock, <FONT STYLE="white-space:nowrap">pre-funded</FONT> warrants and Class A warrants in
April 2019, will be sufficient to fund its forecasted operating expenses, capital expenditure requirements and debt service payments for at least the next twelve months from the issuance of these financial statements. The future viability of the
Company beyond that point is dependent on its ability to raise additional capital to finance its operations. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">If the Company is unable to obtain funding,
the Company will be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or <FONT STYLE="white-space:nowrap">pre-commercialization</FONT> efforts, which could adversely affect its
business prospects, or the Company may be unable to continue operations. Although management continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the
Company to fund continuing operations, if at all. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>2.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>Summary of Significant Accounting Policies </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Unaudited Interim Financial Statements </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The
condensed balance sheet at December&nbsp;31, 2018 was derived from audited financial statements but does not include all disclosures required by GAAP. The accompanying condensed consolidated financial statements are unaudited. The accompanying
unaudited interim consolidated financial statements have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (the &#147;SEC&#148;) for interim financial statements. Accordingly, certain
information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to
make the information presented not misleading. These unaudited condensed financial statements should be read in conjunction with the Company&#146;s&nbsp;audited financial statements and the notes thereto for the year ended December&nbsp;31, 2018. In
the opinion of management, all adjustments, consisting only of normal recurring adjustments as necessary, for the fair statement of the Company&#146;s condensed financial position, condensed results of its operations and cash flows have been made.
The results of operations for the three months ended March&nbsp;31, 2019 are not necessarily indicative of the results of operations that may be expected for the year ending December&nbsp;31, 2019. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Use of Estimates </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The preparation of the
Company&#146;s condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities
at the date of the consolidated financial statements, and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the
accrual of research and development expenses, the valuation of intangible assets acquired in business combinations, the valuations of common stock prior to the Merger, the valuation of stock options, preferred stock warrants (and the resulting
preferred stock warrant liability), derivative instruments (and the resulting derivative liability), and the preferred stock repurchase liability, and valuation of lease liabilities. The Company bases its estimates on historical experience, known
trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates when there are changes in circumstances, facts and experience. Changes in
estimates are recorded in the period in which they become known. Actual results could differ from those estimates. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Principles of Consolidation
</I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, including Arsanis
Biosciences GmbH, which is incorporated in Vienna, Austria (&#147;Arsanis GmbH&#148;), and X4 Therapeutics, Inc. All significant intercompany accounts and transactions have been eliminated. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Foreign Currency and Currency Translation </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Management has determined that the functional currency for the Company&#146;s wholly owned foreign subsidiary, Arsanis Biosciences GmbH, is the Euro.
Management&#146;s assessment considered the currency environment in which the entity operates, including inflows of </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">11 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">
cash from research and development incentive programs and outflows of cash for operating expenditure. Accordingly, the assets and liabilities of Arsanis Biosciences GmbH are translated from the
Euro into United States dollars at the exchange rate in effect on the balance sheet date and income and expenses are translated at the average exchange rate in effect during the period. Unrealized translation gains and losses are recorded as a
cumulative translation adjustment, which is included in the consolidated balance sheet as a component of accumulated other comprehensive income (loss). Adjustments that arise from exchange rate changes on transactions denominated in a currency other
than the Euro are included in other income (expense), net in the consolidated statements of operations as incurred. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Concentrations of Credit Risk
and Significant Suppliers </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash
and cash equivalents and research and development incentive receivables. The Company generally maintains cash balances in various operating accounts at financial institutions that management believes to be of high credit quality, in amounts that may
exceed federally insured limits. The Company has not experienced any losses related to its cash and cash equivalents. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company is dependent on
third-party manufacturers to supply products for research and development activities in its programs. The Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active
pharmaceutical ingredients and formulated drugs related to these programs. These programs could be adversely affected by a significant interruption in these manufacturing services or in the supply of active pharmaceutical ingredients and formulated
drugs. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Cash and Cash Equivalents </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company
considers all highly liquid investments with maturities of three months or less at the date of purchase to be cash equivalents. Cash equivalents consisted of money market funds as of March&nbsp;31, 2019 and December&nbsp;31, 2018. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Restricted Cash </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In connection with the
Company&#146;s lease agreement entered into January 2017 for its facility in Cambridge, Massachusetts, the Company maintains a letter of credit of $264 for the benefit of the landlord. As of March&nbsp;31, 2019 and December&nbsp;31, 2018, the
underlying cash balance securing this letter of credit was classified as restricted cash <FONT STYLE="white-space:nowrap">(non-current)</FONT> on its condensed consolidated balance sheets. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company also maintains letters of credit for the benefit of the landlords in connection with the Company&#146;s office, laboratory, parking and storage
space leases in Waltham, MA and Vienna, Austria and another letter of credit in connection with Company&#146;s corporate credit cards. As of March&nbsp;31, 2019, long term restricted cash consisted of letters of credit related to the Company&#146;s
leases of office, laboratory, parking and storage space lease in Vienna, Austria, of $283 and leased office space acquired from Arsanis located in Waltham, MA, which expires on December&nbsp;31, 2023, of approximately $250. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As of March&nbsp;31, 2019, the Company was also required to maintain a separate cash balance of $150 to collateralize corporate credit cards with a bank,
which was classified as restricted cash <FONT STYLE="white-space:nowrap">(non-current)</FONT> on its consolidated balance sheets. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Property and
Equipment </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is
recognized using the straight-line method over the estimated useful life of each asset, as follows: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="68%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="62%"></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Estimated&nbsp;Useful&nbsp;Life</B></TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Office furniture</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">3 years</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Computer equipment</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">3 years</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Software</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">3 years</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Laboratory equipment</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">3 to 10 years</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Leasehold improvements</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Shorter&nbsp;of&nbsp;lease&nbsp;term&nbsp;or&nbsp;10&nbsp;years</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Estimated useful lives are periodically assessed to determine if changes are appropriate. Maintenance and repairs are charged
to expense as incurred. When assets are retired or otherwise disposed of, the cost of these assets and related accumulated depreciation or amortization are eliminated from the consolidated balance sheet and any resulting gains or losses are included
in the consolidated statements of operations and comprehensive loss in the period of disposal. Costs for capital assets not yet placed into service are capitalized as
<FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">construction-in-progress</FONT></FONT> and depreciated once placed into service. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">12 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I><FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">Right-of-Use</FONT></FONT> Assets and
Leases </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Effective January&nbsp;1, 2019, the Company adopted Accounting Standards Codification (&#147;ASC&#148;), Topic 842, <I>Leases
</I>(&#147;ASC 842&#148;), using the modified retrospective approach through a cumulative-effect adjustment and utilizing the effective date as its date of initial application, with prior periods unchanged and presented in accordance with the
guidance in Topic 840, <I>Leases</I> (&#147;ASC 840&#148;). </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">At the inception of an arrangement, the Company determines whether the arrangement is or
contains a lease based on the unique facts and circumstances present. Leases with a <FONT STYLE="white-space:nowrap">non-cancellable</FONT> term greater than one year are recognized on the balance sheet as <FONT STYLE="white-space:nowrap"><FONT
STYLE="white-space:nowrap">right-of-use</FONT></FONT> assets, lease liabilities and long-term lease liabilities. The Company has elected not to recognize on the balance sheet leases with terms of one year or less. Options to renew a lease are not
included in the Company&#146;s initial lease term assessment unless there is reasonable certainty that the Company will renew. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Operating lease
liabilities and their corresponding <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">right-of-use</FONT></FONT> assets are recorded based on the present value of lease payments over the expected remaining lease term. However,
certain adjustments to the <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">right-of-use</FONT></FONT> operating asset may be required for items, such as incentives received. The interest rate implicit in lease contracts is
typically not readily determinable. As a result, the Company utilizes its incremental borrowing rates, which are the rates it incurs to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic
environment. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In accordance with the guidance in ASC 842, components of a lease are split into lease components and
<FONT STYLE="white-space:nowrap">non-lease</FONT> components. A policy election is available pursuant to which an entity may elect to not separate lease and <FONT STYLE="white-space:nowrap">non-lease</FONT> components. Rather, each lease component
and the related <FONT STYLE="white-space:nowrap">non-lease</FONT> components would be accounted for together as a single component. For new and amended leases beginning in 2019 and after, the Company has elected to account for the lease and <FONT
STYLE="white-space:nowrap">non-lease</FONT> components as a combined lease component for its office and laboratory building leases.<B><I> </I></B> </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Impairment of Long-Lived Assets </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Long-lived assets
consist of property and equipment. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that
the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in
the use of the assets. If an impairment review is performed to evaluate a long-lived asset group for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived
asset group to its carrying value. An impairment loss would be recognized in loss from operations when estimated undiscounted future cash flows expected to result from the use of an asset group are less than its carrying amount. The impairment loss
would be based on the excess of the carrying value of the impaired asset group over its fair value. To date, the Company has not recorded any impairment losses on long-lived assets. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Goodwill </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Business combinations are accounted for
under the acquisition method. The total purchase price of an acquisition is allocated to the underlying identifiable net assets, based on their respective estimated fair values as of the acquisition date. Determining the fair value of assets
acquired and liabilities assumed requires management&#146;s judgment and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash inflows and outflows, probabilities of success, discount
rates, and asset lives, among other items. Assets acquired and liabilities assumed are recorded at their estimated fair values. The excess of the purchase price over the estimated fair values of the net assets acquired is recorded as goodwill. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Goodwill is tested for impairment at the reporting unit level annually in the fourth quarter, or more frequently when events or changes in circumstances
indicate that the asset might be impaired. Examples of such events or circumstances include, but are not limited to, a significant adverse change in legal or business climate, an adverse regulatory action or unanticipated competition. The Company
has determined that it operates in a single operating segment and has a single reporting unit. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company assesses qualitative factors to determine
whether the existence of events or circumstances would indicate that it is more likely than not that the fair value of the reporting unit was less than its carrying amount. If after assessing the totality of events or circumstances, the Company were
to determine that it is more likely than not that the fair value of the reporting unit is less than its carrying amount, then the Company would perform a quantitative impairment test. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company compares the fair value of the reporting unit to its carrying value. If the fair value of the reporting unit exceeds the carrying value of the net
assets, goodwill is not impaired, and no further testing is required. If the fair value of the reporting unit is less than the carrying value, the Company measures the amount of impairment loss, if any, as the excess of the carrying value over the
fair value of the reporting unit. The Company has determined there were no indicators of goodwill impairment as of March&nbsp;31, 2019. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">13 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Intangible Assets </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company acquired certain <FONT STYLE="white-space:nowrap">in-process</FONT> research and development assets (&#147;IPR&amp;D&#148;), which are classified
as indefinite-lived intangible assets. Acquired IPR&amp;D represents the fair value assigned to research and development assets that the Company acquires and have not been completed at the acquisition date. The fair value of IPR&amp;D acquired in a
business combination is capitalized on the Company&#146;s consolidated balance sheets at the acquisition-date fair value and is determined by estimating the costs to develop the technology into commercially viable products, estimating the resulting
revenue from the projects, and discounting the projected net cash flows to present value. IPR&amp;D is not amortized, but rather is reviewed for impairment on an annual basis or more frequently if indicators of impairment are present, until the
project is completed or abandoned. If the Company determines that IPR&amp;D becomes impaired or is abandoned, the carrying value is written down to its fair value with the related impairment charge recognized in the Company&#146;s consolidated
statement of operations in the period in which the impairment occurs. Upon successful completion of each project and launch of the product, the Company will make a separate determination of the estimated useful life of the IPR&amp;D intangible asset
and the related amortization will be recorded as an expense prospectively over its estimated useful life. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The projected discounted cash flow models used
to estimate the Company&#146;s IPR&amp;D reflect significant assumptions regarding the estimates a market participant would make in order to evaluate a drug development asset, including the following: </P>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">Probability of successfully completing clinical trials and obtaining regulatory approval; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">Market size, market growth projections, and market share; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">Estimates regarding the timing of and the expected costs to advance the Company&#146;s clinical programs to
commercialization; </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">Estimates of future cash flows from potential product sales; and </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">A discount rate. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Additionally, to the extent the Company acquire other indefinite-lived intangible assets through its business combinations, these assets are reviewed for
impairment on an annual basis or more frequently if indicators of impairment are present. If the Company determines that the asset becomes impaired, the carrying value is written down to its fair value with the related impairment charge recognized
in its consolidated statements of operations in the period in which the impairment occurs. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Deferred Rent </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company&#146;s lease agreements include payment escalations and lease incentives (including a leasehold improvement tenant allowance). For periods prior to
January&nbsp;1, 2019, these payments were accrued or deferred as appropriate such that rent expense was recognized on a straight-line basis over the respective lease terms. Effective January&nbsp;1, 2019, upon the adoption of ASC 842,<I>
</I>deferred rent was reclassified as a reduction to the applicable <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">right-of-use</FONT></FONT> asset as further described in Note 8. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Fair Value Measurements </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Certain assets and
liabilities of the Company are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the
asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial
assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: </P>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">Level 1&#151;Quoted prices in active markets for identical assets or liabilities. </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">Level 2&#151;Observable inputs (other than Level&nbsp;1 quoted prices), such as quoted prices in active markets
for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">Level 3&#151;Unobservable inputs that are supported by little or no market activity that are significant to
determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Prior to the Merger, the Company&#146;s preferred stock warrant liability, derivative liability and preferred stock repurchase liability were carried at fair
value, determined according to Level&nbsp;3 inputs in the fair value hierarchy described above (See Note&nbsp;4). The Company&#146;s cash equivalents, consisting of money market funds invested in U.S. Treasury securities, are carried at fair value,
determined based on Level&nbsp;2 inputs in the fair value hierarchy described above (see Note 4). The carrying values of the Company&#146;s accounts payable and accrued expenses approximate their fair values due to the short-term nature of these
liabilities. The carrying value of the Company&#146;s outstanding loan and security agreement (the &#147;Hercules Loan Agreement&#148;) with Hercules Capital, Inc. (&#147;Hercules&#148;) approximates its fair value at March&nbsp;31, 2019 because the
debt bears interest at a variable market rate and the Company&#146;s credit risk has not materially </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">14 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">
changed since the inception of the agreement. The carrying value of the Company&#146;s loans under the funding agreements with &Ouml;sterreichische Forschungsf&ouml;rderungsgesellschaft mbH
(&#147;FFG&#148;) were recorded at fair value on the opening balance sheet of Arsanis as of the date of the Merger, and approximates the fair value of the loans at March&nbsp;31, 2019. (See Note&nbsp;3). </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Segment Information </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company manages its
operations as a single operating segment for the purposes of assessing performance and making operating decisions. The Company&#146;s focus is on the discovery, development and commercialization of novel therapeutics for the treatment of rare
diseases. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Revenue Recognition </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Effective
January&nbsp;1, 2018, the Company adopted ASC Topic 606, Revenue from Contracts with Customers (&#147;ASC 606&#148;), using the modified retrospective transition method. The modified retrospective method requires that the cumulative effect of
initially applying ASC 606 be recognized as an adjustment to the opening balance of retained earnings or accumulated deficit of the annual period that includes the date of initial application. The Company did not have any arrangements that were in
the scope of ASC 606 on January&nbsp;1, 2018 and thus there was no impact to the condensed consolidated financial statements as a result of the adoption. This standard applies to all contracts with customers, except for contracts that are within the
scope of other standards, such as collaboration arrangements and leases. Prior to completion of the Merger, Arsanis entered into a single <FONT STYLE="white-space:nowrap">out-licensing</FONT> agreement with Janssen Pharmaceuticals, Inc. (see Note
13) that was within the scope of ASC 606. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Research and Development Programs </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Proceeds under the research and development incentive program from the Austrian government are recognized as other income in an amount equal to the qualifying
expenses incurred in each period multiplied by the applicable reimbursement percentage. Incentive income recognized upon incurring qualifying expenses in advance of receipt of proceeds from research and development incentives is recorded in the
consolidated balance sheet as research and development incentive receivables. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Research and Development Costs </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Costs associated with internal research and development and external research and development services, including drug development and preclinical studies, are
expensed as incurred. Research and development expenses include costs for salaries, employee benefits, subcontractors, facility-related expenses, depreciation and amortization, stock-based compensation, third-party license fees, laboratory supplies,
and external costs of outside vendors engaged to conduct discovery, preclinical and clinical development activities and clinical trials as well as to manufacture clinical trial materials, and other costs. The Company recognizes external research and
development costs based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its service providers. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid
expenses. Such prepaid expenses are recognized as an expense when the goods have been delivered or the related services have been performed, or when it is no longer expected that the goods will be delivered or the services rendered. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Upfront payments, milestone payments and annual maintenance fees under license agreements are expensed in the period in which they are incurred. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Patent Costs </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">All patent-related costs incurred in
connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Debt Issuance Costs </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Debt issuance costs consist
of payments made to secure commitments under certain debt financing arrangements. These amounts are recognized as interest expense over the period of the financing arrangement using the effective interest method. If the financing arrangement is
canceled or forfeited, or if the utility of the arrangement to the Company is otherwise compromised, these costs are recognized as interest expense immediately. The Company&#146;s consolidated financial statements present debt issuance costs related
to a recognized debt liability as a direct reduction from the carrying amount of that debt liability. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Stock-Based Compensation </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company measures all stock-based awards granted to employees and directors based on the fair value on the date of the grant and recognizes compensation
expense for those awards, net of estimated forfeitures, over the requisite service period, which is generally the vesting period of the respective award. The Company issues stock-based awards with only service-based vesting conditions and records
the expense for these awards using the straight-line method. The Company has not issued any stock-based awards with performance-based vesting conditions. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">15 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Effective January&nbsp;1, 2019, the Company adopted ASU No.
<FONT STYLE="white-space:nowrap">2018-07,&nbsp;Compensation&#151;Stock</FONT> Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting&nbsp;(&#147;ASU <FONT STYLE="white-space:nowrap">2018-07&#148;),</FONT> which expands
the scope of Topic 718 to include share-based payment awards to nonemployees. As a result, stock-based awards granted to consultants and <FONT STYLE="white-space:nowrap">non-employees</FONT> are accounted for in the same manner as awards granted to
employees and directors as described above. The impact of adoption this new guidance did not have a material impact on the Company&#146;s consolidated financial statements. Prior to the adoption of ASU
<FONT STYLE="white-space:nowrap">2018-07,</FONT> for stock-based awards granted to <FONT STYLE="white-space:nowrap">non-employee</FONT> consultants, compensation expense was recognized over the period during which services were rendered by such <FONT
STYLE="white-space:nowrap">non-employee</FONT> consultants until completed. At the end of each financial reporting period prior to completion of the service, the fair value of these awards was remeasured using the then-current fair value of the
Company&#146;s common stock and updated assumption inputs in the Black-Scholes option-pricing model. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company classifies stock-based compensation
expense in its consolidated statement of operations and comprehensive loss in the same manner in which the award recipient&#146;s payroll costs are classified or in which the award recipient&#146;s service payments are classified. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company recognizes compensation expense for only the portion of awards that are expected to vest. In developing a forfeiture rate estimate, the Company
has considered its historical experience to estimate <FONT STYLE="white-space:nowrap">pre-vesting</FONT> forfeitures for service-based awards. The impact of a forfeiture rate adjustment will be recognized in full in the period of adjustment, and if
the actual forfeiture rate is materially different from the Company&#146;s estimate, the Company may be required to record adjustments to stock-based compensation expense in future periods. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. Prior to March&nbsp;13, 2019, the
Company had been a private company and lacked company-specific historical and implied volatility information for its stock. Therefore, the Company estimates its expected stock price volatility based on the historical volatility of publicly traded
peer companies and expects to continue to do so until it has adequate historical data regarding the volatility of its own traded stock price. The expected term of the Company&#146;s stock options has been determined utilizing the
&#147;simplified&#148; method for awards that qualify as &#147;plain-vanilla&#148; options. The expected term of stock options granted to <FONT STYLE="white-space:nowrap">non-employee</FONT> consultants is equal to the contractual term of the option
award. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on
the fact that the Company has never paid cash dividends on common stock and does not expect to pay any cash dividends in the foreseeable future. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Preferred Stock Warrant Liability </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Prior to the
Merger with Arsanis, the Company classified warrants for the purchase of shares of its convertible preferred stock (see Note&nbsp;10) as a liability on its consolidated balance sheets as these warrants are freestanding financial instruments that may
have required the Company to transfer assets upon exercise. The warrant liability, which consisted of warrants for the purchase of Series&nbsp;A and Series&nbsp;B convertible preferred stock, was initially recorded at fair value upon the date of
issuance of each warrant and is subsequently remeasured to fair value at each reporting date. Changes in the fair value of the warrant liability are recognized as a component of other income (expense), net in the consolidated statement of operations
and comprehensive loss. Concurrent with the closing of the Merger, all X4 preferred stock was converted to Arsanis common stock and the X4 preferred stock warrants converted to warrants for the purchase of Arsanis common stock. The Company assessed
the features of the warrants and determined that they qualify for classification as permanent equity. Accordingly, the Company remeasured the warrants to fair value upon the closing of the Merger and reclassified the resulting warrant liability to
additional <FONT STYLE="white-space:nowrap">paid-in</FONT> capital. (see Note&nbsp;10). </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Derivative Liability </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company&#146;s license agreement with Genzyme Corporation (&#147;Genzyme&#148;) (see Note&nbsp;13) contained a contingent payment obligation that required
the Company to make a cash payment to Genzyme upon a change of control event of the Company. The contingent payment obligation met the definition of a derivative instrument as the contingent payment obligation was not clearly and closely related to
its host instrument and was a cash-settled liability. Accordingly, the Company classified this derivative as a liability within other liabilities <FONT STYLE="white-space:nowrap">(non-current)</FONT> on its condensed consolidated balance sheet. The
derivative liability was initially recorded at fair value on the date of entering into the license agreement and was subsequently remeasured to fair value at each reporting date. Changes in the fair value of this derivative liability were recognized
as a component of other income (expense), net in the condensed consolidated statement of operations and comprehensive loss. The Merger with Arsanis (see Note 1) qualified as a change of control event, as defined in the license agreement, but
resulted in no payment being due to Genzyme under the license agreement. As a result, on March&nbsp;13, 2019, the closing date of the Merger with Arsanis, the derivative liability was remeasured to fair value, which was $0, and subsequent changes in
fair value will no longer be recognized in the consolidated statements of operations and comprehensive loss because the contingent payment obligation to Genzyme expired at that time. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">16 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In addition, the Company&#146;s Hercules loan (see Note&nbsp;7) contains a redemption feature that, upon an
event of default, provides Hercules the option to accelerate and demand repayment of the debt, including a prepayment premium. The redemption feature meets the definition of a derivative instrument as the repayment of the debt contains a substantial
premium, resulting in the redemption feature not being clearly and closely related to its host instrument. Accordingly, the Company classifies this derivative as a liability within other liabilities
<FONT STYLE="white-space:nowrap">(non-current)</FONT> on its condensed consolidated balance sheet. The derivative liability was initially recorded at fair value on the date of entering into the Hercules Loan Agreement and is subsequently remeasured
to fair value at each reporting date. Changes in the fair value of this derivative liability are recognized as a component of other income (expense), net in the condensed consolidated statement of operations and comprehensive loss. Changes in the
fair value of this derivative liability will continue to be recognized until all amounts outstanding under the Hercules Loan Agreement are repaid or until the Hercules Loan Agreement is terminated. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Comprehensive Loss </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Comprehensive loss includes
net loss as well as other changes in stockholders&#146; equity (deficit) that result from transactions and economic events other than those with stockholders. For the three months ended March&nbsp;31, 2019, comprehensive loss included $23 of foreign
currency translation gain adjustments. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Income Taxes </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the
expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company&#146;s tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial
statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The
Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the
deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering
prudent and feasible tax planning strategies. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by
applying a <FONT STYLE="white-space:nowrap">two-step</FONT> process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by
the taxing authorities. If the tax position is deemed <FONT STYLE="white-space:nowrap">more-likely-than-not</FONT> to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial
statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves,
or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Net Income (Loss) per Share
</I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company follows the <FONT STYLE="white-space:nowrap">two-class</FONT> method when computing net income (loss) per share as the Company has
issued shares that meet the definition of participating securities. The <FONT STYLE="white-space:nowrap">two-class</FONT> method determines net income (loss) per share for each class of common and participating securities according to dividends
declared or accumulated and participation rights in undistributed earnings. The <FONT STYLE="white-space:nowrap">two-class</FONT> method requires income available to common stockholders for the period to be allocated between common and participating
securities based upon their respective rights to receive dividends as if all income for the period had been distributed. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Basic net income (loss) per
share attributable to common stockholders is computed by dividing the net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding for the period. Diluted net income (loss) attributable to common
stockholders is computed by adjusting net income (loss) attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net income (loss) per share attributable to common
stockholders is computed by dividing the diluted net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding for the period, including potential dilutive common shares. For purpose of this
calculation, outstanding stock options, convertible preferred stock and warrants to purchase shares of convertible preferred stock are considered potential dilutive common shares. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company&#146;s convertible preferred stock contractually entitles the holders of such shares to participate in dividends but does not contractually
require the holders of such shares to participate in losses of the Company. Accordingly, in periods in which the Company reports a net loss attributable to common stockholders, such losses are not allocated to such participating securities. In
periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common
shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported a net loss attributable to common stockholders for the three months ended March&nbsp;31, 2019 and 2018. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">17 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Recently Adopted Accounting Pronouncements </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In February 2016, the FASB issued ASU <FONT STYLE="white-space:nowrap">No.&nbsp;2016-02</FONT><I>, Leases (Topic</I><I></I><I>&nbsp;842)</I> (&#147;ASU <FONT
STYLE="white-space:nowrap">2016-02&#148;</FONT> or &#147;ASC 842&#148;)), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new
standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine
whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease. A lessee is also required to record a
<FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">right-of-use</FONT></FONT> asset and a lease liability for all leases with a term of greater than 12&nbsp;months regardless of their classification. Leases with a term of 12 months or
less may be accounted for similar to prior guidance for operating leases. The Company adopted the new leasing standard as of the required effective date of January&nbsp;1, 2019 using a modified retrospective transition approach to be applied to
leases existing as of, or entered into after, January&nbsp;1, 2019. The adoption had no impact on accumulated deficit. The new lease standard provides a number of optional practical expedients in transition. The Company applied the package of
practical expedients to leases that commenced prior to the effective date, whereby it will elect to not reassess the following: (i)&nbsp;whether any expired or existing contracts contain leases; (ii)&nbsp;the lease classification for any expired or
existing leases; and (iii)&nbsp;initial direct costs for any existing leases. The Company also elected the short-term lease recognition exemption for all leases that qualify, where a
<FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">right-of-use</FONT></FONT> asset or lease liability will not be recognized for short-term leases. Upon the adoption of ASC 842, the Company recorded $2.5&nbsp;million of operating
lease liabilities and $2.0&nbsp;million of <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">right-of-use&nbsp;assets</FONT></FONT> on its consolidated balance. The adoption did not have a material impact on the Company&#146;s
statement of operations, statement of comprehensive loss or statement of cash flows. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In January 2017, the FASB issued ASU
<FONT STYLE="white-space:nowrap">No.&nbsp;2017-04,</FONT><I>&nbsp;Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.</I>&nbsp;The new standard simplifies the subsequent measurement of goodwill by eliminating
the second step of the goodwill impairment test. This ASU will be applied prospectively and is effective for annual or interim goodwill impairment tests in fiscal years beginning after December&nbsp;15, 2019 with early adoption permitted. The
Company has adopted this guidance on January&nbsp;1, 2019 and will apply it to its annual impairment test, and any interim impairment tests during the year ending December&nbsp;31, 2019. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In April 2017, the FASB issued ASU <FONT STYLE="white-space:nowrap">2017-08,</FONT><I>&nbsp;Receivables &#150; Nonrefundable Fees and Other Costs</I>
(&#147;Subtopic <FONT STYLE="white-space:nowrap">310-20&#148;).</FONT> The new standard amends the amortization period for certain purchased callable debt securities held at a premium by shortening the amortization period for the premium to the
earliest call date.&nbsp;Subtopic <FONT STYLE="white-space:nowrap">310-20</FONT> calls for a modified retrospective application under which&nbsp;a cumulative-effect adjustment will be made to retained earnings as of the beginning of the first
reporting period in which the guidance is adopted.&nbsp;The new standard will be effective beginning January&nbsp;1, 2019 and early adoption is permitted for public entities.&nbsp;The Company adopted this guidance, effective January&nbsp;1, 2019,
and its adoption had no impact on the Company&#146;s financial position, results of operations or cash flows. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In July 2017, the FASB issued ASU <FONT
STYLE="white-space:nowrap">No.&nbsp;2017-11,</FONT> <I>Earnings Per Share (Topic</I><I></I><I>&nbsp;260), Distinguishing Liabilities from Equity (Topic</I><I></I><I>&nbsp;480), Derivatives and Hedging (Topic</I><I></I><I>&nbsp;815)
(Part</I><I></I><I>&nbsp;I) Accounting for Certain Financial Instruments with Down Round Features (Part</I><I></I><I>&nbsp;II) Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and
Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception</I> (&#147;ASU <FONT STYLE="white-space:nowrap">2017-11&#148;).</FONT> Part&nbsp;I applies to entities that issue financial instruments such as warrants, convertible debt
or convertible preferred stock that contain down-round features. Part&nbsp;II replaces the indefinite deferral for certain mandatorily redeemable noncontrolling interests and mandatorily redeemable financial instruments of nonpublic entities
contained within ASC Topic&nbsp;480 with a scope exception and does not impact the accounting for these mandatorily redeemable instruments. For public entities, ASU <FONT STYLE="white-space:nowrap">2017-11</FONT> is effective for annual reporting
periods beginning after December&nbsp;15, 2018, including interim periods within those fiscal years. The Company adopted ASU <FONT STYLE="white-space:nowrap">2017-11</FONT> as of the required effective date of January&nbsp;1, 2019. The adoption of
ASU <FONT STYLE="white-space:nowrap">2017-11</FONT> had no impact on the Company&#146;s financial position, results of operations or cash flows. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In June
2018, the FASB issued ASU <FONT STYLE="white-space:nowrap">No.&nbsp;2018-07,</FONT> <I>Compensation&#151;Stock Compensation (Topic</I><I></I><I>&nbsp;718): Improvements to Nonemployee Share-Based Payment Accounting </I>(&#147;ASU <FONT
STYLE="white-space:nowrap">2018-07&#148;).</FONT> These amendments expand the scope of Topic&nbsp;718, Compensation&#151;Stock Compensation (which previously only included share-based payments to employees) to include share-based payments issued to <FONT
STYLE="white-space:nowrap">non-employees</FONT> for goods or services. Consequently, the accounting for share-based payments to <FONT STYLE="white-space:nowrap">non-employees</FONT> and employees will be substantially aligned. The ASU supersedes <FONT
STYLE="white-space:nowrap">Subtopic&nbsp;505-50,</FONT> Equity&#151;<I>Equity-Based Payments to <FONT STYLE="white-space:nowrap">Non-Employees</FONT></I>. The Company adopted ASU <FONT STYLE="white-space:nowrap">2018-07</FONT> on January&nbsp;1,
2019. The adoption of this standard had no impact on the Company&#146;s financial statements. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Recently Issued Accounting Pronouncements
</I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In August 2018, the FASB issued ASU <FONT STYLE="white-space:nowrap">No.&nbsp;2018-13,</FONT><I> Fair Value Measurement (Topic 820): Disclosure
Framework&#151;Changes to the Disclosure Requirements for Fair Value Measurement</I> (&#147;ASU <FONT STYLE="white-space:nowrap">2018-13&#148;),</FONT> which&nbsp;removes, adds and modifies certain disclosure requirements for fair value measurements
in Topic 820. The Company will no longer be required to disclose the amount of and reasons for transfers between Level&nbsp;1 and Level&nbsp;2 of the fair value hierarchy as well as the valuation processes of Level&nbsp;3 fair value
</P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">18 </P>

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<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">
measurements. However, the Company will be required to additionally disclose the changes in unrealized gains and losses included in other comprehensive income for recurring Level&nbsp;3 fair
value measurements and the range and weighted average of assumptions used to develop significant unobservable inputs for Level&nbsp;3 fair value measurements. ASU <FONT STYLE="white-space:nowrap">2018-13</FONT> is effective for fiscal years, and
interim periods within those fiscal years, beginning after December&nbsp;15, 2019. The amendments relating to additional disclosure requirements will be applied prospectively for only the most recent interim or annual period presented in the initial
year of adoption. All other amendments will be applied retrospectively to all periods presented upon their effective date. The Company is currently evaluating the impact that the adoption of ASU <FONT STYLE="white-space:nowrap">2018-13</FONT> will
have on its consolidated financial statements. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In August 2018, the FASB issued ASU
<FONT STYLE="white-space:nowrap">2018-15,</FONT><I>&nbsp;Intangibles-Goodwill and <FONT STYLE="white-space:nowrap">Other-Internal-Use</FONT> Software (Subtopic <FONT STYLE="white-space:nowrap">350-40):</FONT> Customer&#146;s Accounting for
Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, (&#147;ASU <FONT STYLE="white-space:nowrap">2018-15&#148;)</FONT></I>. The amendments in this update align the requirements for capitalizing implementation
costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain <FONT STYLE="white-space:nowrap">internal-use</FONT> software (and hosting arrangements that
include an <FONT STYLE="white-space:nowrap">internal-use</FONT> software license). The accounting for the service element of a hosting arrangement that is a service contract is not affected by the amendments in this update. The new standard will be
effective beginning January&nbsp;1, 2020 and early adoption is permitted. The amendments in this update should be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption.&nbsp;The Company is
currently evaluating the impact that the adoption of ASU <FONT STYLE="white-space:nowrap">2018-15</FONT> will have on its consolidated financial statements. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>3.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>Merger Accounting </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Based on the Exchange Ratio of 0.5702, immediately following the Merger, former Arsanis stockholders, Arsanis option holders and other persons holding
securities or other rights directly or indirectly convertible, exercisable or exchangeable for Arsanis common stock owned approximately 31.3% of the outstanding capital stock of the combined organization on a fully diluted basis, and former
X4&nbsp;stockholders, holders of options or warrants to acquire X4 capital stock and other persons holding securities and other rights directly or indirectly convertible, exercisable or exchangeable for X4 capital stock owned approximately 68.7% of
the outstanding capital stock of the combined organization on a fully diluted basis. At the closing of the Merger, all shares of X4 common stock and X4&nbsp;preferred stock then outstanding were exchanged for Arsanis common stock. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In addition, pursuant to the terms of the Merger Agreement, the Company, for accounting purposes, assumed all outstanding stock options to purchase shares of
Arsanis common stock at the closing of the Merger. At the closing of the Merger, such stock options became options to purchase an aggregate of 271,230 shares of the Company&#146;s common stock after giving effect to the Reverse Stock Split. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The total purchase price paid in the Merger has been allocated to the tangible and intangible assets acquired and liabilities assumed of Arsanis based on
their fair values as of the completion of the Merger, with the excess allocated to goodwill. The following summarizes the preliminary estimate of the purchase price paid in the Merger: </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="68%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="85%"></TD>
<TD VALIGN="bottom" WIDTH="9%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Number of shares of the combined organization owned by Arsanis stockholders&nbsp;(1)</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2,440,582</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Multiplied by the fair value per share of Arsanis common stock&nbsp;(2)</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">18.66</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Fair value of consideration issued it effect the Merger</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">45,541</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Fair value of replacement awards held by former employees, board of directors and consultants of
Arsanis that were vested as of the Merger.</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">817</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Purchase price:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">46,358</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="line-height:8.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000;width:10%">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">(1)</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">The number of shares of 2,440,582 represents the historical 14,643,737 shares of Arsanis common stock
outstanding immediately prior to the closing of the Merger, adjusted for the Reverse Stock Split. </P></TD></TR></TABLE>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">(2)</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">Based on the last reported sale price of Arsanis common stock on the Nasdaq Global Market on March&nbsp;13,
2019, the closing date of the Merger, and gives effect to the Reverse Stock Split. </P></TD></TR></TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">19 </P>

</DIV></Center>


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<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The following summarizes the allocation of the purchase price to the net tangible and intangible assets
acquired: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="68%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="85%"></TD>
<TD VALIGN="bottom" WIDTH="6%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Cash and cash equivalents and restricted cash</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">26,406</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Other current assets</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2,147</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Property and equipment, net</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">68</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">IPR&amp;D indefinite-lived intangible assets</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4,900</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Other assets, <FONT STYLE="white-space:nowrap">non-current</FONT></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">879</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Current liabilities</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(5,221</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Loans payable</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(8,713</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Other liabilities, <FONT STYLE="white-space:nowrap">non-current</FONT></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(1,515</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Goodwill</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">27,407</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Purchase price</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">&nbsp;&nbsp;&nbsp;&nbsp;46,358</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The goodwill of $27,407 is not tax deductible and represents the excess of the consideration paid over the fair value of
assets acquired and liabilities assumed. Goodwill is mainly attributable to the enhanced value of the combined company, as reflected in the increase in market value of the Arsanis common shares following the announcement of the Merger with X4. The
Company incurred costs directly related to the Merger of approximately $1&nbsp;million for the three months ended March&nbsp;31, 2019. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The preliminary
allocation of the purchase price for the Merger was based on estimates of the fair value of the net assets acquired and is subject to adjustment upon finalization of the valuation of the acquired intangible assets, property, plant and equipment, <FONT
STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">right-of-use</FONT></FONT> assets, lease obligations, fair value of debt and any related deferred taxes. Measurements of these items inherently require significant estimates and
assumptions. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The following supplemental unaudited pro forma information presents the Company&#146;s financial results as if the acquisition of Arsanis
had occurred on January&nbsp;1, 2018: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="76%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:8pt" ALIGN="center">


<TR>
<TD WIDTH="78%"></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Three Months Ended<BR>March&nbsp;31,</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2019</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2018</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center"><B>(unaudited)</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Revenue</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">0</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">0</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net loss</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(16,258</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(20,235</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The above unaudited pro forma information was determined based on the historical GAAP results of the Company and Arsanis. The
unaudited pro forma consolidated results are not necessarily indicative of what the Company&#146;s consolidated results of operations would have been if the acquisition was completed on January&nbsp;1, 2018. The unaudited pro forma consolidated net
loss includes pro forma adjustments primarily relating to the reclassification of transaction costs and severance payments directly related to the closing of the Merger of $2.7&nbsp;million from the three months ended March&nbsp;31, 2019 to the
three months ended March&nbsp;31, 2018. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>4.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>Fair Value of Financial Assets and Liabilities </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The following tables present information about the Company&#146;s financial assets and liabilities measured at fair value on a recurring basis and indicate the
level of the fair value hierarchy used to determine such fair values: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="92%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="60%"></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="14" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Fair Value Measurements as of March&nbsp;31, 2019 Using:</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;Level&nbsp;1&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;Level&nbsp;2&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;Level&nbsp;3&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Total&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Assets:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Cash equivalents&#151;money market funds</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">22,299</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">22,299</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">22,299</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">22,299</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Liabilities:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Preferred stock warrant liability</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Derivative liability</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">18</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">18</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">18</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">18</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">20 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="92%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="61%"></TD>
<TD VALIGN="bottom" WIDTH="6%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="6%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="6%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="6%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="14" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Fair Value Measurements as of December&nbsp;31, 2018 Using:</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;Level&nbsp;1&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;Level&nbsp;2&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;Level&nbsp;3&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Total&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Assets:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Cash equivalents&#151;money market fund</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">8,134</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">8,134</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">8,134</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">8,134</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Liabilities:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Preferred stock warrant liability</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">4,947</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">4,947</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Derivative liability</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">201</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">201</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">5,148</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">5,148</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As of March&nbsp;31, 2019 and December&nbsp;31, 2018, there were no transfers between Level&nbsp;1, Level&nbsp;2 and
Level&nbsp;3. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company&#146;s cash equivalents consisted of a money market fund invested in U.S. Treasury securities. The money market fund was valued
using inputs observable in active markets for similar securities, which represents a Level&nbsp;2 measurement in the fair value hierarchy. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Valuation of Preferred Stock Warrant Liabilities </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The preferred stock warrant liability in the table above consists of the fair values of (i)&nbsp;warrants to purchase shares of Series&nbsp;A convertible
preferred stock that were issued in 2015 and shares of Series&nbsp;B convertible preferred stock that were issued in 2017 and 2018 in connection with the Company&#146;s Series&nbsp;A and Series&nbsp;B convertible preferred stock financings,
respectively (see Notes&nbsp;10), (ii)&nbsp;warrants to purchase shares of Series&nbsp;A convertible preferred stock that were issued in 2016 in connection with the Company&#146;s entering into a loan and security agreement with Silicon Valley Bank
(see Note&nbsp;7) and (iii)&nbsp;warrants to purchase shares of Series&nbsp;B convertible preferred stock that were issued or were issuable in 2018 in connection with the Company&#146;s entering into the Hercules Loan Agreement (see Note&nbsp;7).
The liability associated with the warrants was recorded at fair value on the dates the warrants were issued and exercisable and was subsequently remeasured to fair value at each reporting date through December&nbsp;31, 2018. Upon the closing of the
Merger, all X4 preferred stock warrants were converted to warrants for Company&#146;s common stock and, as a result, the warrants were adjusted to fair value and reclassified to permanent equity. The aggregate fair value of the warrant liability was
determined based on significant inputs not observable in the market, which represents a Level&nbsp;3 measurement within the fair value hierarchy. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The
Company used various valuation methods, including the Monte Carlo method, the option-pricing method and the hybrid method (which is a combination of an option-pricing method and a probability-weighted expected return method), all of which
incorporate assumptions and estimates, to value the preferred stock warrants. Estimates and assumptions impacting the fair value measurement include the fair value per share of the underlying shares of the Company&#146;s Series&nbsp;A and
Series&nbsp;B convertible preferred stock, risk free interest rate, expected dividend yield, expected volatility of the price of the underlying preferred stock, and either the remaining contractual term of the warrants (except for warrants that
would be automatically exercised upon an initial public offering, in which case the remaining estimated term to automatic exercise was used). The most significant assumption in the Monte Carlo method, the option-pricing method and the hybrid method
impacting the fair value of the preferred stock warrants is the fair value of the Company&#146;s convertible preferred stock as of each remeasurement date. The Company determines the fair value per share of the underlying preferred stock by taking
into consideration the most recent sales of its convertible preferred stock, results obtained from third-party valuations and additional factors that are deemed relevant. As of December&nbsp;31, 2018, the fair value of the Series&nbsp;A convertible
preferred stock was $1.70&nbsp;per share the fair value of the Series&nbsp;B convertible preferred stock was $1.86&nbsp;per share. There were no warrants for the purchase of convertible preferred shares as of March&nbsp;31, 2019 as all such warrants
were converted to warrants for the purchase of common stock upon the Merger. The Company has been a private company prior to the Merger and lacks company-specific historical and implied volatility information of its stock. Therefore, it estimates
its expected stock volatility based on the historical volatility of publicly traded peer companies for a term equal to the estimated remaining term of the warrants. The risk-free interest rate is determined by reference to the U.S. Treasury yield
curve for time periods approximately equal to the estimated remaining term of the warrants. The Company estimated a 0% expected dividend yield based on the fact that the Company has never paid or declared dividends and does not intend to do so in
the foreseeable future. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Valuation of Derivative Liability </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The fair value of the derivative liability recognized in connection with the Company&#146;s July 2014 license agreement with Genzyme (see Note&nbsp;13) was
determined based on significant inputs not observable in the market, which represents a Level&nbsp;3 measurement within the fair value hierarchy. The fair value of this derivative liability is reported within other liabilities on the consolidated
balance </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">21 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">
sheets. The fair value of this derivative liability was estimated by the Company at each reporting date based, in part, on the results of third-party valuations, which were prepared using the
option-pricing method or the hybrid method, each of which considered as inputs the type, timing and probability of occurrence of a change of control event, the potential amount of the payment under potential exit scenarios, the fair value per share
of the underlying common stock and the risk-adjusted discount rate. As of December&nbsp;31, 2018, the fair value of this derivative liability was $183. The Merger with Arsanis (see Note 1) qualified as a change of control event, as defined in the
license agreement, but results in no payment being due to Genzyme under the license agreement. As a result, on March&nbsp;13, 2019, the closing date of the Merger with Arsanis, this derivative liability was remeasured to fair value, which was $0,
and subsequent changes in fair value will no longer be recognized in the consolidated statements of operations and comprehensive loss because the contingent payment obligation to Genzyme expired at that time. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The fair value of the derivative liability recognized in connection with the Hercules Loan Agreement (see Note&nbsp;7) was determined based on significant
inputs not observable in the market, which represents a Level&nbsp;3 measurement within the fair value hierarchy. The fair value of this derivative liability is reported within other liabilities on the consolidated balance sheets. The fair value of
this derivative liability was estimated by the Company at each reporting date based, in part, on the results of third-party valuations, which were prepared based on a discounted cash flow model that considered the timing and probability of
occurrence of a redemption upon an event of default, the potential amount of prepayment upon an event of default and the risk-adjusted discount rate. As of March&nbsp;31, 2019 and December&nbsp;31, 2018, the fair value of this derivative liability
was immaterial. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The following table provides a roll-forward of the aggregate fair values of the Company&#146;s warrant liability, derivative liability
and preferred stock repurchase liability, for which fair values are determined using Level&nbsp;3 inputs: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="76%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="74%"></TD>
<TD VALIGN="bottom" WIDTH="9%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="9%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Preferred&nbsp;Stock</B><br><B>Warrant</B><br><B>Liability</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Derivative</B><br><B>Liability</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Balance as of December&nbsp;31, 2018</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">4,947</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">201</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Change in fair value</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">288</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(183</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Conversion of convertible preferred stock warrant into common stock warrant in connection with
Merger</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(5,235</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Balance as of March&nbsp;31, 2019</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">$</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">18</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>5.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>Property and Equipment, Net </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Property and equipment, net consisted of the following: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="76%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="76%"></TD>
<TD VALIGN="bottom" WIDTH="7%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="7%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>March&nbsp;31,</B><br><B>2019</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>December&nbsp;31,</B><br><B>2018</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Leasehold improvements</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">&nbsp;&nbsp;&nbsp;&nbsp;299</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">&nbsp;&nbsp;&nbsp;&nbsp;299</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Furniture and fixtures</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">53</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">53</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Computer equipment</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">19</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">56</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Software</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">9</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">9</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Lab equipment</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">67</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">448</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">417</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Less: Accumulated depreciation and amortization</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(177</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(176</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">271</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">241</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Depreciation and amortization expense related to property and equipment was $20 and $26 for the three months ended
March&nbsp;31, 2019 and 2018, respectively. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">22 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>

<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>6.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>Accrued Expenses </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Accrued expenses consisted of the following: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="76%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="72%"></TD>
<TD VALIGN="bottom" WIDTH="8%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="8%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;March&nbsp;31,&nbsp;&nbsp;&nbsp;</B><br><B>2019</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>December&nbsp;31,</B><br><B>2018</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Accrued employee compensation and benefits</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">&nbsp;&nbsp;&nbsp;&nbsp;1,239</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">924</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Accrued external research and development expenses</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">819</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">754</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Accrued professional fees</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,850</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,324</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Deferred rent, current portion</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">93</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Other</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">271</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">156</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">4,179</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">3,251</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>7.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>Long-Term Debt </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Long-term debt consisted of the following: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="76%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="72%"></TD>
<TD VALIGN="bottom" WIDTH="8%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="8%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;March&nbsp;31,&nbsp;&nbsp;&nbsp;</B><br><B>2019</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>December&nbsp;31,</B><br><B>2018</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Principal amount of long-term debt</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">19,546</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">10,000</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Less: Current portion of long-term debt</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(5,298</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(1,687</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Long-term debt, net of current portion</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">14,248</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">8,313</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Debt discount, net of accretion</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(1,019</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(226</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Cumulative accretion of final payment due at maturity</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">136</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">58</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Long-term debt, including accretion, net of current portion</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">13,365</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">8,145</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>SVB Loan Agreement </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In October 2016, the Company entered into a loan and security agreement with Silicon Valley Bank (&#147;SVB&#148;), which the Company refers to as the SVB Loan
Agreement, pursuant to which SVB made certain term loans available to the Company. The SVB Loan Agreement provided for a term loan of up to $6,000, which was borrowed by the Company in June&nbsp;2017. Borrowings under the SVB Loan Agreement bore
interest at a variable rate equal to 5.5% plus the greater of (i)&nbsp;3.5% or (ii)&nbsp;The Wall Street Journal prime rate. In October 2018, in connection with entering into the Hercules Loan Agreement, the Company terminated the SVB Loan Agreement
and repaid all amounts due under the SVB Loan Agreement, including unpaid principal of $4,333, a final payment of $270, a prepayment premium of $87 and accrued interest of $23. The Company accounted for the repayment of amounts as an extinguishment
of the SVB Loan Agreement and recognized a loss on extinguishment of debt of $229 within other income (expense), net in the consolidated statement of operations and comprehensive loss. The loss on extinguishment of debt was calculated as the
difference between the reacquisition price of the borrowings under the SVB Loan Agreement of $4,713 and the carrying value of the debt under the SVB Loan Agreement of $4,484. As of October&nbsp;19, 2018, the date of repayment of all borrowings under
the SVB Loan&nbsp;Agreement, the interest rate applicable to borrowings under the SVB Loan Agreement was 10.75%. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Hercules Loan Agreement
</I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In October 2018, the Company entered into the Hercules Loan Agreement, which provided for aggregate borrowings of up to $13,000, consisting of
(i)&nbsp;a term loan of up to $8,000, which was available upon entering into the agreement, (ii)&nbsp;subject to specified financing conditions, an additional term loan of up to $2,000, available for borrowing from January&nbsp;1, 2019 to
March&nbsp;31, 2019, and (iii)&nbsp;subject to specified financing conditions and the receipt of the second tranche $2,000 term loan described above, an additional term loan of up to $3,000, available for borrowing until March&nbsp;31, 2019. In
October 2018, the Company borrowed $8,000 under the Hercules Loan Agreement. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In December 2018, the Company entered into the First Amendment to the
Hercules Loan Agreement (the &#147;First Amendment&#148;), which amended the available borrowing dates of the second tranche from between January&nbsp;1, 2019 and March&nbsp;31, 2019 to between December&nbsp;11, 2018 and December&nbsp;14, 2018 and
amended the term loan maturity date to November&nbsp;1, 2021. In December 2018, the Company borrowed the additional $2,000 provided under the Hercules Loan Agreement, as amended by the First Amendment. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In March&nbsp;2019, the conditions necessary for borrowing the remaining $3,000 under the Hercules Loan Agreement were not met and the borrowing capacity
expired at that time. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">23 </P>

</DIV></Center>


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<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Borrowings under the Hercules Loan Agreement bear interest at variable rates, with the first tranche bearing
interest at a variable rate equal to the greater of (i)&nbsp;9.5% or (ii)&nbsp;9.5% plus<I> The Wall Street Journal</I> prime rate minus 5.25%, the second tranche bearing interest at a variable rate, subject to completion of specified financing
conditions, equal to either (A)&nbsp;the greater of (i)&nbsp;9.5% or (ii)&nbsp;9.5% plus<I> The Wall Street Journal</I> prime rate minus 5.25% or (B)&nbsp;the greater of (i)&nbsp;8.75% or (ii)&nbsp;8.75% plus<I> The Wall Street Journal</I> prime
rate minus 5.25%, and the third tranche bearing interest at a variable rate equal to the greater of (i)&nbsp;8.75% or (ii)&nbsp;8.75% plus<I> The Wall Street Journal</I> prime rate minus 5.25%. In an event of default, as defined, and until such
event is no longer continuing, the interest rate applicable to borrowings under the Hercules Loan Agreement would be increased by 4.0%. As of March&nbsp;31, 2019 and December&nbsp;31, 2018, the interest rate applicable to borrowings under the
Hercules Loan Agreement was 9.80% and 9.75%. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Borrowings under the Hercules Loan Agreement are repayable in monthly interest-only payments through August
2019, or a later date upon achievement of specified conditions, and in equal monthly payments of principal and accrued interest from September 2019 until the maturity date of the loan, which is November 2021. At the Company&#146;s option, the
Company may prepay all, but not less than all, of the outstanding borrowings, subject to a prepayment premium of up to 2.0% of the principal amount outstanding as of the date of repayment. The Hercules Loan Agreement also provides for a final
payment, payable upon maturity or the repayment in full of all obligations under the agreement, of up to $953. An aggregate final payment of $794 payable in connection with the $8,000 term loan and the $2,000 term loan is being accreted to interest
expense to increase the carrying value of the debt over the term of the loan using the effective interest method. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In addition, the Hercules Loan
Agreement contains a redemption feature that, upon an event of default, provides Hercules the option to accelerate and demand repayment of the debt, including a prepayment premium. The Company concluded that the redemption feature meets the
definition of a derivative instrument as the repayment of the debt contains a substantial premium, resulting in the redemption feature not being clearly and closely related to the host instrument. The Company recorded the issuance-date fair value of
the derivative liability of $18 as a debt discount and as a derivative liability on its consolidated balance sheet. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Borrowings under the Hercules Loan
Agreement are collateralized by substantially all of the Company&#146;s personal property and other assets, including its intellectual property until a specified financing condition is met. Under the Hercules Loan Agreement, the Company has agreed
to affirmative and negative covenants to which the Company will remain subject until maturity or repayment in full. The covenants include maintaining a minimum liquidity amount of the lesser of (i)&nbsp;125% of outstanding borrowings under the
Hercules Loan Agreement and (ii)&nbsp;100% of the Company&#146;s cash and cash equivalents in an account in which Hercules has a first priority security interest as well as restrictions on the Company&#146;s ability to incur additional indebtedness,
pay dividends, encumber its intellectual property, or engage in certain fundamental business transactions, such as mergers or acquisitions of other businesses. Obligations under the Hercules Loan Agreement are subject to acceleration upon occurrence
of specified events of default, including payment default, insolvency and a material adverse change in the Company&#146;s business, operations or financial or other condition. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In connection with entering into the Hercules Loan Agreement in October 2018, the Company issued to Hercules warrants for the purchase of 210,638&nbsp;shares
of Series&nbsp;B convertible preferred stock at an exercise price of $1.88 per share. These warrants were immediately exercisable and expire in October 2028. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In connection with entering into the First Amendment in December 2018, the Company agreed to issue to Hercules warrants for the purchase of a specified number
of shares of convertible preferred stock or, if issued following the Merger with Arsanis, a specified number of shares of common stock of the combined organization, at an aggregate exercise price of $99. The warrants were to be issued at the
earliest of (i)&nbsp;June&nbsp;30, 2019, (ii)&nbsp;the earlier to occur of (a)&nbsp;the date the Company prepays the outstanding borrowings or (b)&nbsp;the date the outstanding borrowings become due and payable, or (iii)&nbsp;on or before the fifth
business day following the closing of or the announcement of the termination of the Company&#146;s Merger with Arsanis. The number of shares of convertible preferred stock issuable upon exercise of these warrants was determined to be 52,659 shares,
calculated by dividing $99 by the $1.88 price per share paid by investors that purchased shares of Series&nbsp;B convertible preferred stock in September 2018 (see Note&nbsp;11). On March&nbsp;18, 2019, as a result of the closing of the Merger with
Arsanis on March&nbsp;13, 2019, the Company issued to Hercules warrants for the purchase of 5,000 shares of common stock of the combined organization at an exercise price of $19.80 per share, each of which reflected the share Exchange Ratio of <FONT
STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">1-for-0.5702</FONT></FONT> applied in the Merger as well as the Reverse Stock Split effected by the combined organization on March&nbsp;13, 2019. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On October&nbsp;19, 2018 and December&nbsp;11, 2018, the dates the Company entered into the Hercules Loan Agreement and the First Amendment, respectively, the
Company recorded the aggregate initial fair value of the warrants of $132 as a preferred stock warrant liability, with a corresponding amount recorded as a debt discount on the Company&#146;s consolidated balance sheet. As of March&nbsp;13, 2019 and
December&nbsp;31, 2018, the fair value of the warrants was $326 and $282, respectively. Upon the closing of the Merger, the warrants were converted to warrants for common stock and are no longer adjusted to fair value. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">24 </P>

</DIV></Center>


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<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In connection with entering into the Hercules Loan Agreement and the First Amendment, the Company also paid
Hercules $92 of upfront fees, including facility, due diligence and legal fees associated with entering into the agreement, which were also recorded as a debt discount. The debt discount is reflected as a reduction of the carrying value of long-term
debt on the Company&#146;s consolidated balance sheet and is being amortized to interest expense over the term of the loan using the effective interest method. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company recognized aggregate interest expense under the Hercules Loan Agreement of $357 and $0 during three months ended March&nbsp;31, 2019 and 2018,
respectively, which included <FONT STYLE="white-space:nowrap">non-cash</FONT> interest expense of $113 related to the accretion of the debt discount and the final payment. As of March&nbsp;31, 2019 and December&nbsp;31, 2018, the unamortized debt
discount was $182 and $226, respectively. The Company&#146;s annual effective interest rate of the Hercules Loan Agreement as of March&nbsp;31, 2019 and December&nbsp;31, 2018 was approximately 14.2%, respectively. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">There were no principal payments due or paid under the Hercules Loan Agreement during the three months ended March&nbsp;31, 2019. Principal payments begin in
September 2019. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>FFG Loan Agreement </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Between
September 2011 and March 2017, Arsanis GmbH, a subsidiary of Arsanis, entered into a series of funding agreements with &Ouml;sterreichische Forschungsf&ouml;rderungsgesellschaft mbH (&#147;FFG&#148;) that provided for loans and grants to fund
qualifying research and development expenditures of Arsanis GmbH on a <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">project-by-project</FONT></FONT> basis, as approved by FFG. Amounts due under the FFG loans bear interest at
rates ranging from 0.75% to 2.0%&nbsp;per annum. As of March&nbsp;31, 2019, giving effect to the Settlement Agreement (as defined below), the loans matured at various dates between March&nbsp;31, 2019 and March 2021. Interest on amounts due under
the loans is payable semi-annually in arrears, with all principal and remaining accrued interest due upon maturity. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As of March&nbsp;31, 2019, the
outstanding principal amount under loans from FFG was $9,546, including $2,914 of current portion. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On March&nbsp;8, 2019, Arsanis, Merger Sub, X4 and
Arsanis GmbH, a wholly owned subsidiary of Arsanis, entered into the Settlement Agreement with FFG (the &#147;Settlement Agreement&#148;) in respect to allegations by FFG in February 2019 that Arsanis and Arsanis GmbH breached certain reporting,
performance and other obligations in connection with grants and loans made by FFG to Arsanis GmbH between September 2011 and March 2017 to fund qualifying research and development expenditures. Pursuant to the terms of the Settlement Agreement, in
exchange for FFG&#146;s waiver of all claims against Arsanis and Arsanis GmbH (except for its claims for repayment of the loans and regular interest but including its waiver of claims for repayment of grants and interest exceeding regular interest),
subject to compliance by Arsanis and Arsanis GmbH with the terms of the Settlement Agreement, Arsanis GmbH agreed to repay the outstanding loan principal (plus regular interest accrued thereon) on an accelerated payment schedule of three years
instead of five years, with the final accelerated installment due and payable on June&nbsp;30, 2021. The parties also agreed, among other things, that (i)&nbsp;the portion of such loans to be repaid in 2019 is $2,914 <I></I>on the first business day
following<I></I> March&nbsp;31, 2019 and (ii)&nbsp;until all of the loans have been repaid and subject to other terms specified in the Settlement Agreement, commencing April&nbsp;30, 2019, a minimum cash balance equal to 70% of the then-outstanding
principal amount of the loans will be maintained at Arsanis GmbH in an account held with an Austrian bank. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As of March&nbsp;31, 2019, future principal
payments and the final payment due under the Company&#146;s loan agreements were as follows: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="68%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="61%"></TD>
<TD VALIGN="bottom" WIDTH="5%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="5%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="5%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">Year Ending December&nbsp;31,</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Hercules</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>FFG</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Total</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">2019</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">1,345</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">2,914</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">4,259</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">2020</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4,305</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4,462</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">8,767</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">2021</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4,350</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2,170</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">6,520</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Long-term debt</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">&nbsp;&nbsp;&nbsp;&nbsp;10,000</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;9,546</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">19,546</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>8.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>Leases </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Effective January&nbsp;1, 2019, the Company adopted ASC 842 using the modified retrospective approach through a cumulative-effect adjustment and utilizing the
effective date as its date of initial application, with prior periods unchanged and presented in accordance with the previous lease accounting guidance. Upon adoption, the Company recorded <FONT STYLE="white-space:nowrap"><FONT
STYLE="white-space:nowrap">right-of-use</FONT></FONT> assets of $2,026 and lease liabilities of $2,538, of which $1,925 was classified as <FONT STYLE="white-space:nowrap">non-current</FONT> and $613 as current. The difference between the value of
the <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">right-of-use</FONT></FONT> asset and the lease liabilities relates to $512 of net deferred, accrued and prepaid rent that was reclassified against the <FONT
STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">right-of-use</FONT></FONT> asset upon adoption of ASC 842 on January&nbsp;1, 2019. The Company has lease agreements for its facilities in Cambridge, Massachusetts, which is the
Company&#146;s global headquarters, Vienna, Austria, which is the Company&#146;s research and development center, and Waltham, Massachusetts, which is the former headquarters of Arsanis. The Company plans to sublease its Waltham, Massachusetts
facility. There are no restrictions or financial covenants associated with any of the lease agreements. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">25 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Cambridge Lease </I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In August 2017, the Company entered into a lease agreement for office space of approximately thirteen thousand square feet in Cambridge, Massachusetts
(&#147;Cambridge Lease&#148;) which expires on July&nbsp;31, 2022. The Cambridge lease includes an annual rent escalation clause and the Company has the option to extend the lease for one period of five additional years. Base rent is approximately
$810 annually and the monthly rent expense is being recognized on a straight-line basis over the term of the lease. In addition to the base rent, the Company is also responsible for its share of operating expenses, electricity and real estate taxes,
in accordance with the terms of lease. These costs are classified as variable lease payments and are not included in the determination of the leases&#146; <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">right-of-use</FONT></FONT>
operating assets or lease operating liabilities. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Waltham Lease </I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On March&nbsp;13, 2019, as part of its Merger with Arsanis, the Company acquired an operating lease for approximately six thousand square feet of office space
in Waltham, Massachusetts (&#147;Waltham Lease&#148;). The Waltham lease, as amended, commenced on January&nbsp;1, 2019, and expires approximately 5 years from the commencement date. The base rent is approximately $459 annually. In addition to the
base rent, the Company is also responsible for its share of operating expenses, electricity and real estate taxes, in accordance with the terms of the Amended Lease Agreement. These costs are classified as variable lease payments and are not
included in the determination of the leases&#146; <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">right-of-use</FONT></FONT> assets or lease liabilities. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Vienna Lease </I></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On March&nbsp;13, 2019, as part of its
Merger with Arsanis, the Company acquired an operating lease for approximately four hundred square meters of laboratory and office space in Vienna, Austria, which commenced on March&nbsp;1, 2019, as amended, for a term of two years. The lease is
cancellable by the Company upon three month&#146;s notice with no penalty. The annual base rent is approximately $155. The Company has classified this lease as a short-term lease as it is not reasonably certain that the Company with not terminate
the lease within one year and, accordingly, has not recorded a <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">right-of-use</FONT></FONT> asset. Accordingly, rent expense is recorded on a straight-line basis as incurred over the
term of the lease. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As the Company&#146;s leases do not provide an implicit rate, the Company estimated the incremental borrowing rate in calculating the
present value of the lease payments. The Company utilizes its incremental borrowing rates, which are the rates incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment.
</P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The components of lease expense for the three months ended March&nbsp;31, 2019 were as follows: </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="68%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="72%"></TD>
<TD VALIGN="bottom" WIDTH="25%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom" NOWRAP><FONT STYLE="font-size:10pt"><B>Lease Cost</B></FONT></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>For&nbsp;the&nbsp;three&nbsp;months&nbsp;ended</B><br><B>March&nbsp;31, 2019</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Fixed operating lease cost</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right"> 187</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Short-term lease costs</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">8</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total lease expense</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right"> 195</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><B>Other information</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Cash paid for amounts included in the measurement of lease liabilities:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Operating cash flows from operating leases</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right"> 201</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Leased assets obtained in exchange for new operating lease liabilities&nbsp;(1)</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right"> 781</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Weighted-average remaining lease term&#151;operating leases</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">3.9&nbsp;years</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Weighted-average discount rate&#151;operating leases</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">9.0</TD>
<TD NOWRAP VALIGN="bottom">%&nbsp;</TD></TR>
</TABLE> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">(1)</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">Acquired in Merger with Arsanis </P></TD></TR></TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">26 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Maturities of lease liabilities due under these lease agreements as of March&nbsp;31, 2019 are as follows:
</P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="68%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="81%"></TD>
<TD VALIGN="bottom" WIDTH="14%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom" NOWRAP> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-bottom:1.00pt solid #000000; display:table-cell; font-size:8pt; font-family:Times New Roman; "><B>Maturity of lease liabilities</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Operating&nbsp;Leases</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">2019 (remainder of 2019)</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right"> 837</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">2020</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,281</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">2021</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,304</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">2022</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">970</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">2023</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">489</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Thereafter</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total lease payments</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4,880</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Less: interest</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(764</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total operating lease liabilities as of March&nbsp;31, 2019</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">4,116</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company adopted ASU <FONT STYLE="white-space:nowrap">2016-02</FONT> on January&nbsp;1, 2019 as noted above, and as
required, the following disclosure is provided for periods prior to adoption. Future annual minimum lease payments due under the Company&#146;s operating leases as of December&nbsp;31, 2018 were as follows: </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="68%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="81%"></TD>
<TD VALIGN="bottom" WIDTH="14%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom" NOWRAP> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-bottom:1.00pt solid #000000; display:table-cell; font-size:8pt; font-family:Times New Roman; "><B>Year Ending December&nbsp;31,</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Operating&nbsp;Leases</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">2019</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">810</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">2020</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">823</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">2021</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">835</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">2022</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">492</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">2,960</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>9.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>Commitment and Contingencies </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Sponsored Research Agreement Commitments </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In
April&nbsp;2017, the Company entered into a sponsored research agreement with a university that the Company refers to as the Sponsored Research Agreement, pursuant to which the Company and the university intend to conduct a research program related
to understanding the mechanisms of failed long-term adaptive immunity in WHIM patients. Under the terms of the Sponsored Research Agreement, the Company agreed to provide funding for the research program of up to $499 over a three-year period. The
Sponsored Research Agreement will remain in effect for three years, unless earlier terminated in the event that (i)&nbsp;either party materially breaches any representation, obligation or covenant and fails to remedy such breach within 30 days after
receipt of notice or (ii)&nbsp;the Principal Investigator, as defined in the agreement, is unable or unwilling to conduct the research or perform his or her obligations under the agreement, at which time the Company may terminate the agreement upon
30 days&#146; prior written notice to the university. The Company may terminate the agreement at any time upon at least 60 days&#146; prior written notice. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">During the three months ended March&nbsp;31, 2019 and 2018, the Company incurred $42, respectively, of research and development expenses related to its
payment obligations to the university under the Sponsored Research Agreement. As of March&nbsp;31, 2019, the Company had <FONT STYLE="white-space:nowrap">non-cancelable</FONT> purchase commitments under this agreement totaling $181, with $125
committed in 2019 and $56 committed in 2020. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Manufacturing Commitments </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As of March&nbsp;31, 2019, the Company entered into agreements with several contract manufacturing organizations to provide preclinical and clinical trial
materials. As of March&nbsp;31, 2019, and December&nbsp;31, 2018, the Company had <FONT STYLE="white-space:nowrap">non-cancelable</FONT> purchase commitments under these agreements totaling approximately $250, all committed in 2019. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Indemnification Agreements </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In the ordinary course
of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements
</P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">27 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">
or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and its
executive officers that will require the Company to, among other things, indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the
Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnification obligations. The Company is not currently aware of
any indemnification claims and has not accrued any liabilities related to such obligations in its consolidated financial statements as of March&nbsp;31, 2019 or December&nbsp;31, 2018. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>License Agreements </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Arsanis entered into an
agreement (the &#147;Adimab Option Agreement&#148;) in February 2017, which was acquired by the Company as a result of the Merger, under which the Company is obligated to make contingent and <FONT STYLE="white-space:nowrap">non-contingent</FONT>
payments should the Company exercise its option to obtain rights to certain RSV antibodies. If the Company chose to exercise its option, it would be obligated to pay Adimab an option fee of approximately $250 and make clinical and regulatory
milestone payments of up to approximately $25,000, as well as royalty payments on a <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">product-by-product</FONT></FONT> and <FONT STYLE="white-space:nowrap"><FONT
STYLE="white-space:nowrap">country-by-country</FONT></FONT> basis of a mid single-digit percentage based on net sales by the Company, its affiliates, licensees or sublicensees of products based on certain RSV antibodies during the applicable term
for such product in that country. The Company may choose to exercise its option under the terms of the Adimab Option Agreement at any time on or before August&nbsp;31, 2019. As of March&nbsp;31, 2019, the Company had not exercised its option under
the Adimab Option Agreement. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Legal Proceedings </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company is not a party to any litigation and does not have contingency reserves established for any litigation liabilities. At each reporting date, the
Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses as
incurred the costs related to such legal proceedings </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>10.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>Preferred and Common Stock Warrants </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As of March&nbsp;31, 2019, the Company&#146;s outstanding warrants to purchase shares of common stock consisted of the following: </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="80%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="60%"></TD>
<TD VALIGN="bottom" WIDTH="3%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="3%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="3%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="3%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom" NOWRAP> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-bottom:1.00pt solid #000000; display:table-cell; font-size:8pt; font-family:Times New Roman; "><B>Issuance Date</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Number&nbsp;of</B><br><B>Shares of</B><br><B>Common</B><br><B>Stock&nbsp;Issuable</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Exercise</B><br><B>Price</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Classification</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Expiration&nbsp;Date</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">August&nbsp;14, 2015</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">81,228</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">21.78</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Equity</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">August&nbsp;14,&nbsp;2020</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">August&nbsp;21, 2015</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">69,603</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">21.78</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Equity</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">August&nbsp;21, 2020</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">October&nbsp;25, 2016</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">5,155</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">19.78</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Equity</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">October&nbsp;24, 2026</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">November&nbsp;1, 2017</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">130,609</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">19.78</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Equity</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">October&nbsp;31,&nbsp;2020</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">November&nbsp;17, 2017</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">8,442</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">19.78</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Equity</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">November&nbsp;16, 2020</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">December&nbsp;4, 2017</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">5,661</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">19.78</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Equity</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">December&nbsp;3, 2020</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">December&nbsp;28, 2017</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">6,925</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">19.78</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Equity</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">December&nbsp;27, 2020</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">December&nbsp;28, 2017</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">115,916</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">19.78</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Equity</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">December&nbsp;28, 2027</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">September&nbsp;12, 2018</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">25,275</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">19.78</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Equity</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">September&nbsp;12,&nbsp;2021</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">September&nbsp;12, 2018</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">20,220</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">19.78</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Equity</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">September&nbsp;12, 2028</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">October&nbsp;19, 2018</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">20,016</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">19.78</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Equity</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">October&nbsp;19, 2028</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">December&nbsp;11, 2018</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">5,004</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">19.80</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Equity</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">October&nbsp;19, 2028</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">494,054</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
</TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">28 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As of December&nbsp;31, 2018, the Company&#146;s outstanding warrants to purchase shares of preferred stock
(which converted into warrants to purchase common stock upon close of the Merger) consisted of the following (not adjusted for the Reverse Stock Split or Exchange Ratio): </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="32%"></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom" COLSPAN="24" NOWRAP ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>December&nbsp;31, 2018</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:9pt">
<TD VALIGN="bottom" NOWRAP> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-bottom:1.00pt solid #000000; display:table-cell; font-size:9pt; font-family:Times New Roman; "><B>Warrant Name</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Issuance Date</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Number&nbsp;of</B><br><B>Shares of</B><br><B>Preferred</B><br><B>Stock&nbsp;Issuable</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Exercise</B><br><B>Price</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Exercisable</B><br><B>for</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Classification</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Expiration Date</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Series A warrants</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">August&nbsp;14, 2015</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">854,785</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">2.07</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Series&nbsp;A</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Liability</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">August&nbsp;14, 2020</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Series A warrants</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">August&nbsp;21, 2015</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">732,453</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">2.07</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Series A</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Liability</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">August&nbsp;21, 2020</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">SVB warrants</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">October&nbsp;25, 2016</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">54,256</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">1.88</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Series A</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Liability</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">October&nbsp;24, 2026</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Series B warrants</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">November&nbsp;1, 2017</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,374,435</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">1.88</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Series B</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Liability</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">October&nbsp;31, 2020</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Series B warrants</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">November&nbsp;17, 2017</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">88,845</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">1.88</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Series B</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Liability</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">November&nbsp;16, 2020</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Series B warrants</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">December&nbsp;4, 2017</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">59,576</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">1.88</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Series B</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Liability</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">December&nbsp;3, 2020</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Series B warrants</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">December&nbsp;28, 2017</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">72,875</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">1.88</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Series B</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Liability</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">December&nbsp;27, 2020</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Series B warrants</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">December&nbsp;28, 2017</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,219,815</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">1.88</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Series B</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Liability</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">December&nbsp;28, 2027</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Series B warrants</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">September&nbsp;12, 2018</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">265,957</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">1.88</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Series B</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Liability</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">September&nbsp;12,&nbsp;2021</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Series B warrants</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">September&nbsp;12,&nbsp;2018</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">212,765</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">1.88</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Series B</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Liability</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">September&nbsp;12, 2028</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Series B warrants</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">October&nbsp;19, 2018</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">210,638</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">1.88</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Series B</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">Liability</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">October&nbsp;19, 2028</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">5,146,400</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Prior to the Merger, the Company classified its preferred stock warrants as a liability on its consolidated balance sheet
because the warrants are freestanding financial instruments that may have required the Company to transfer assets upon exercise. The liability associated with each of these warrants was initially recorded at fair value upon the issuance date of each
warrant and is subsequently remeasured to fair value as a component of other income (expense), net in the consolidated statement of operations and comprehensive loss. Upon the closing of the Merger with Arsanis (see Note 1), pursuant to the Merger
Agreement, all of the outstanding X4 preferred stock was converted to Arsanis common stock and the X4 preferred stock warrants converted to warrants for the purchase of Arsanis common stock. The Company assessed the features of the warrants and
determined that they qualify for classification as permanent equity upon the closing of the Merger. Accordingly, the Company remeasured the warrants to fair value upon the closing of the Merger, which was $5,235 at March&nbsp;13, 2019, with $288 of
expense recorded during the three months ended March&nbsp;31, 2019. Upon the closing of the Merger, the warrant liability was reclassified to additional <FONT STYLE="white-space:nowrap">paid-in</FONT> capital.&nbsp;&nbsp;&nbsp;&nbsp; </P>
<P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>11.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>Common Stock, Redeemable Common Stock, and Convertible Preferred Stock (converted to Common Stock)
</B></P></TD></TR></TABLE> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Common Stock </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As of
March&nbsp;31, 2019 and December&nbsp;31, 2018, the Company&#146;s certificate of incorporation, as amended and restated, authorized the Company to issue 33,333,333 shares and 11,070,776, shares, respectively, of $0.001 par value common stock. The
voting, dividend and liquidation rights of the holders of the Company&#146;s common stock are subject to and qualified by the rights, powers and preferences of the holders of the preferred stock. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company&#146;s stockholders. Common stockholders are
entitled to receive dividends, as may be declared by the board of directors, if any. Through March&nbsp;31, 2019 and December&nbsp;31, 2018, no cash dividends had been declared or paid. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Redeemable Common Stock </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Pursuant to the
requirements of the July 2014 license agreement with Genzyme (see Note&nbsp;13), in August 2015, the Company issued to Genzyme for no additional consideration 107,371, as adjusted for the Reverse Stock Split and Exchange Ratio, shares of common
stock, which had an aggregate fair value of $734 on the date of issuance. Genzyme had the right to require the Company to repurchase all, but not less than all, of these shares of common stock at any time during the term of the license agreement for
a price of $0.01 per share. Because of this redemption feature, the shares of common stock issued to Genzyme were classified outside of stockholders&#146; deficit on the consolidated balance sheets. As a result of the Merger, these shares were
exchanged for common stock. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">29 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Convertible Preferred Stock (converted to Common Stock) </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company has issued Series Seed convertible preferred stock (the &#147;Series Seed preferred stock&#148;), Series&nbsp;A convertible preferred stock (the
&#147;Series&nbsp;A preferred stock&#148;) and Series&nbsp;B convertible preferred stock (the &#147;Series&nbsp;B preferred stock&#148;). As of March&nbsp;31, 2019 and December&nbsp;31, 2018, the Company&#146;s certificate of incorporation, as
amended and restated, authorized the Company to issue a total of 10,000,000 shares and 59,413,523 shares, respectively, of preferred stock, with a par value of $0.001 per share. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The holders of Preferred Stock have liquidation rights in the event of a deemed liquidation that, in certain situations, are not solely within the control of
the Company. Therefore, the Preferred Stock is classified outside of stockholders&#146; deficit on the consolidated balance sheet. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As of March&nbsp;31,
2019, there were no preferred stock outstanding. As of December&nbsp;31, 2018, the Preferred Stock consisted of the following: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="57%"></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="18" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>December&nbsp;31, 2018</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Preferred</B><br><B>Stock</B><br><B>Designated</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Preferred</B><br><B>Stock</B><br><B>Issued and</B><br><B>Outstanding</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Carrying</B><br><B>Value</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Liquidation</B><br><B>Preference</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Common<BR>Stock</B><br><B>Issuable<BR>Upon</B><br><B>Conversion(1)</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Series Seed preferred stock</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2,313,523</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,516,136</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">1,310</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">1,444</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">143,630</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Series A preferred stock</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">22,000,000</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">19,946,862</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">32,480</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">47,624</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,895,610</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Series B preferred stock</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">25,100,000</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">18,616,569</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">30,885</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">34,999</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,769,190</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">49,413,523</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">40,079,567</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">64,675</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">84,067</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">3,808,430</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">(1)</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">Adjusted to reflect Reverse Stock Split and Exchange Ratio. </P></TD></TR></TABLE>
<P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>12.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>Stock-Based Compensation </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Summary of Plans </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Upon completion of the Merger
with Arsanis on March&nbsp;13, 2019, X4&#146;s 2015 Employee, Director and Consultant Equity Incentive Plan, as amended (the &#147;2015 Plan&#148;), Arsanis&#146; 2017 Equity Incentive Plan (the &#147;2017 Plan&#148;) and Arsanis&#146; 2017 Employee
Stock Purchase Plan (the &#147;2017 ESPP&#148;) (collectively, the &#147;Plans&#148;) were assumed by the Company. These Plans are administered by the board of directors or, at the discretion of the board of directors, by a committee of the board of
directors. The exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, or its committee if so delegated, except that the exercise price per share of stock options may not be less than 100% of the
fair market value of the share of common stock on the date of grant and the term of the stock option may not be greater than ten years. Incentive stock options granted to employees and restricted stock awards granted to employees, officers, members
of the board of directors, advisors, and consultants of the Company typically vest over four years. <FONT STYLE="white-space:nowrap">Non-statutory</FONT> options granted to employees, officers, members of the board of directors, advisors, and
consultants of the Company typically vest over three or four years. Shares that are expired, terminated, surrendered or canceled under the Plans without having been fully exercised will be available for future awards. In addition, shares of common
stock that are tendered to the Company by a participant to exercise an award are added to the number of shares of common stock available for the grant of awards. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>2015 Employee, Director and Consultant Equity Incentive Plan </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In 2015, the board of directors and shareholders of X4 adopted the 2015 Plan, which provided for the Company to grant incentive stock options or nonqualified
stock options, restricted stock awards and other stock-based awards to employees, directors and consultants of the Company. Each stock option outstanding under the 2015 Plan at the effective time of the Merger was automatically converted into a
stock option exercisable for a number of shares of the Company&#146;s common stock calculated based on the Exchange Ratio and the exercise price per share of such outstanding stock option. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The total number of shares of common stock that may be issued under the 2015 Plan was 1,700,000 shares, adjusted for the reverse stock split as of
December&nbsp;31, 2018 and March&nbsp;31, 2019. Shares that are expired, forfeited, canceled or otherwise terminated without having been fully exercised will be available for future grant under the 2015 Plan. In addition, shares of common stock that
are tendered to the Company by a participant to exercise an award are added to the number of shares of common stock available for future grants. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">30 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>2017 Equity Incentive Plan </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In 2017, the board of directors and shareholders of Arsanis adopted the 2017 Plan which provided for the Company to grant incentive stock options, <FONT
STYLE="white-space:nowrap">non-qualified</FONT> options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. Incentive stock options may be granted only to the Company&#146;s employees, including
officers and directors who are also employees. Awards other than incentive stock options may be granted to employees, officers, members of the board of directors, advisors and consultants of the Company. The number of shares of common stock reserved
for issuance under this plan will automatically increase on January&nbsp;1 of each year, through January&nbsp;1, 2027, in an amount equal to the lowest of 1,025,490 shares of the Company&#146;s common stock, 4% of the number of shares of the
Company&#146;s common stock outstanding on January&nbsp;1 of each year and an amount determined by the Company&#146;s board of directors. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>2017
Employee Stock Purchase Plan </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In 2017, the board of directors and shareholders of Arsanis adopted the 2017 ESPP. The 2017 ESPP provides
participating employees with the opportunity to purchase shares of the Company&#146;s common stock at defined purchase prices over <FONT STYLE="white-space:nowrap">six-month</FONT> offering periods. For the three month period ended March&nbsp;31,
2019, no shares of common stock were issued under the 2017 ESPP. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Stock Option Valuation </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The fair value of stock option grants is estimated using the Black-Scholes option-pricing model. The Company has historically been a private company prior to
March&nbsp;13, 2019, and as a result, lacked company-specific historical and implied volatility information. The Company estimated expected stock volatility based on the historical volatility of a publicly traded set of peer companies and expects to
continue to do so until it has adequate historical data regarding the volatility of its own traded stock price. For options with service-based vesting conditions, the expected term of the Company&#146;s stock options has been determined utilizing
the &#147;simplified&#148; method for awards that qualify as &#147;plain-vanilla&#148; options. The expected term of stock options granted <FONT STYLE="white-space:nowrap">to&nbsp;non-employee&nbsp;consultants</FONT> is equal to the contractual term
of the option award. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield
is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The
following table presents, on a weighted average basis, the assumptions used in the Black-Scholes option-pricing model to determine the grant-date fair value of stock options granted to employees, directors and
<FONT STYLE="white-space:nowrap">non-</FONT> employees: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="76%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="80%"></TD>
<TD VALIGN="bottom" WIDTH="7%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="7%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Three Months Ended<BR>March&nbsp;31,</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;2019&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;2018&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Risk-free interest rate</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2.4</TD>
<TD NOWRAP VALIGN="bottom">%&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2.8</TD>
<TD NOWRAP VALIGN="bottom">%&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Expected term (in years)</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">5.90</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">5.94</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Expected volatility</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">90.6</TD>
<TD NOWRAP VALIGN="bottom">%&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">86.0</TD>
<TD NOWRAP VALIGN="bottom">%&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Expected dividend yield</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">0</TD>
<TD NOWRAP VALIGN="bottom">%&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">0</TD>
<TD NOWRAP VALIGN="bottom">%&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Stock Options </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The
following table summarizes the Company&#146;s stock option activity since December&nbsp;31, 2018: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="92%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="61%"></TD>
<TD VALIGN="bottom" WIDTH="5%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="5%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="5%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="5%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Number&nbsp;of</B><br><B>Shares</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Weighted</B><br><B>Average</B><br><B>Exercise</B><br><B>Price</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Weighted</B><br><B>Average</B><br><B>Contractual</B><br><B>Term&nbsp;(Years)</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Aggregate</B><br><B>Intrinsic</B><br><B>Value</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Outstanding as of December&nbsp;31, 2018</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">797,931</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">8.29</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">8.42</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">6,486</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Assumed as part of Merger with Arsanis</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">271,230</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">&nbsp;&nbsp;&nbsp;&nbsp;62.60</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Granted</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">136,913</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">17.22</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Exercised</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(16,483</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">6.85</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Forfeited</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(22,378</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">8.43</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Outstanding as of March&nbsp;31, 2019</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,167,213</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">21.97</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center">7.65</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">7,168</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Exercisable as of March&nbsp;31, 2019</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">556,774</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">30.13</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Vested and expected to vest as of March&nbsp;31, 2019</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">979,466</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">48.79</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
</TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">31 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The aggregate intrinsic value of options is calculated as the difference between the exercise price of the
stock options and the fair value of the Company&#146;s common stock for those options that had exercise prices lower than the fair value of the Company&#146;s common stock. The aggregate intrinsic value of stock options exercised during the three
months ended March&nbsp;31, 2019 was $123. The weighted average grant-date fair value per share of stock options granted during the three months ended March&nbsp;31, 2019 was $12.88. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Stock-Based Compensation </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Effective
January&nbsp;1, 2019, the Company adopted ASU <FONT STYLE="white-space:nowrap">2018-07</FONT> which required the Company to adjust compensation expense for the three months ended March&nbsp;31, 2019 for an immaterial amount for the unvested <FONT
STYLE="white-space:nowrap">non-employee</FONT> share options outstanding. The Company no longer remeasures the fair value of options granted to <FONT STYLE="white-space:nowrap">non-employees</FONT> at each reporting period end (see Note&nbsp;2).
</P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">During the three months ended March&nbsp;31, 2019, the Company granted options to purchase 136,913 shares of common stock. As of March&nbsp;31, 2019,
total unrecognized compensation expense related to unvested stock options award was $5,066, which is expected to be recognized over a weighted average period of 2.5&nbsp;years. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Stock-based compensation expense was classified in the consolidated statements of operations and comprehensive loss as follows: </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="76%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="80%"></TD>
<TD VALIGN="bottom" WIDTH="8%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="8%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Three Months Ended<BR>March&nbsp;31,</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;2019&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;2018&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Research and development expense</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">84</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">38</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">General and administrative expense</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">178</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">90</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total stock-based compensation</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">262</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">128</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>13.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>License, Collaboration, and Funding Agreements </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Genzyme Agreement </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In July&nbsp;2014, the Company
entered into a license agreement (the &#147;Genzyme Agreement&#148;) with Genzyme pursuant to which the Company was granted an exclusive license to certain patents and intellectual property owned or controlled by Genzyme related to the CXCR4
receptor to develop and commercialize products containing licensed compounds (including but not limited to <FONT STYLE="white-space:nowrap">X4P-001)</FONT> for all therapeutic, prophylactic and diagnostic uses, with the exception of autologous and
allogenic human stem cell therapy. Under the terms of the Genzyme Agreement, the Company is obligated to use commercially reasonable efforts to develop and commercialize licensed products for use in the field in the United States and at least one
other major market country. The Company has the right to grant sublicenses of the licensed rights that cover <FONT STYLE="white-space:nowrap">X4P-001</FONT> to third parties. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In exchange for these rights, in August 2014, the Company made an upfront payment of $50 to Genzyme. The Company accounted for the acquisition of technology
as an asset acquisition because it did not meet the definition of a business. The Company recorded the upfront payment as research and development expense in the consolidated statement of operations and comprehensive loss because the acquired
technology represented <FONT STYLE="white-space:nowrap">in-process</FONT> research and development and had no alternative future use. In August&nbsp;2015, as a result of the closing of the Company&#146;s Series A preferred stock financing, the
Company made an additional cash payment of $300 to Genzyme and issued to Genzyme 107,371 shares of its common stock, as adjusted for the 6 for 1 Reverse Stock Split and Exchange Ratio (see Note&nbsp;11), each as required by the Genzyme Agreement.
The $300 payment and the $734 fair value of the 107,371 shares of common stock issued to Genzyme were recorded as research and development expense in the consolidated statements of operations and comprehensive loss for the year ended
December&nbsp;31, 2015. Prior to the Merger with Arsanis, Genzyme has the right to require the Company to repurchase all, but not less than all, of these shares of common stock at any time during the term of the Genzyme Agreement for a price of
$0.01 per share. Due to this redemption feature, the shares of common stock issued to Genzyme were classified outside of stockholders&#146; deficit on the consolidated balance sheets as of December&nbsp;31, 2018. On March&nbsp;13, 2019, the closing
date of the Merger with Arsanis, these redeemable common shares were exchanged for common shares and, as a result, the fair value of the shares was reclassified to permanent equity. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Under the Genzyme Agreement, the Company is obligated to pay Genzyme milestone payments in the aggregate amount of up to $25,000, contingent upon the
achievement by the Company of certain late-stage regulatory and sales milestones with respect to </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">32 </P>

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<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">
licensed products. In addition, the Company may be required to make a <FONT STYLE="white-space:nowrap">one-time</FONT> milestone payment to Genzyme upon the consummation by the Company of a
change of control transaction, in an amount equal to 5.5% of the consideration paid to equity holders of the Company, other than Genzyme, in connection with such change of control transaction, after deducting outstanding debt obligations of the
Company and the aggregate cash investments made by equity holders into the Company prior to the closing of the change of control transaction. The Merger with Arsanis qualifies as a change of control transaction, as defined in the license agreement,
but results in no payment being due to Genzyme under the license agreement. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company concluded that this contingent payment obligation meets the
definition of a derivative instrument as the contingent payment obligation is not clearly and closely related to its host instrument and is a cash-settled liability (see Note&nbsp;2). Accordingly, the Company classifies this derivative as a
liability within other liabilities <FONT STYLE="white-space:nowrap">(non-current)</FONT> on its consolidated balance sheet (see Note&nbsp;2), and changes in the fair value of the derivative liability are recognized as a component of other income
(expense), net in the consolidated statement of operations and comprehensive loss (see Note&nbsp;4). On March&nbsp;13, 2019, the closing date of the Merger with Arsanis, this derivative liability was remeasured to fair value, which was $0, and
subsequent changes in fair value will no longer be recognized in the consolidated statements of operations and comprehensive loss because the contingent payment obligation expired at that time. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Under the Genzyme Agreement, the Company is obligated to pay Genzyme tiered royalties based on net sales of licensed products that the Company commercializes
under the agreement. The obligation to pay royalties for each licensed product expires on a <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">country-by-country</FONT></FONT> basis on the latest of (i)&nbsp;the expiration
of&nbsp;licensed patent rights that cover that licensed product in that country, (ii)&nbsp;the expiration of regulatory exclusivity in that country and (iii)&nbsp;ten years after the first commercial sale of such licensed product in that country.
Royalty rates are subject to reduction under the agreement in specified circumstances, including in any country if the Company is required to obtain a license from any third party to the extent the Company&#146;s patent rights might infringe the
third party&#146;s patent rights, if a licensed product is not covered by a valid claim in that country or if sales of generic products reach certain thresholds in that country. If the Company enters into a sublicense under the agreement, the
Company will be obligated to pay Genzyme a percentage of certain upfront fees, maintenance fees, milestone payments and royalty payments paid to the Company by the sublicensee. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Under the Genzyme Agreement, the Company will itself manufacture and supply, or enter into manufacturing or supply agreements with Genzyme or third parties to
manufacture and supply, clinical and commercial supplies of licensed compounds and each licensed product. During the three months ended March&nbsp;31, 2019 and 2018, the Company did not enter into any third-party manufacturing or supply agreements
in connection with the Genzyme Agreement. The Company is also responsible for all costs related to the filing, prosecution and maintenance of the licensed patent rights. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Genzyme Agreement will remain in effect until the expiration of the royalty term in all countries for all licensed products.&nbsp;The agreement may be
terminated by either party with at least 90&nbsp;days&#146; notice in the event of material breach by the other party that remains uncured for 90 days, by either party for insolvency or bankruptcy of the other party, immediately by Genzyme if the
Company challenges the licensed patents, or immediately by the Company if a material safety issue arises. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">During the three months ended March&nbsp;31,
2019 and 2018, the Company did not incur any payment obligations to Genzyme under the Genzyme Agreement. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Georgetown Agreement </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In December 2016, the Company entered into a license agreement (the &#147;Georgetown Agreement&#148;) with Georgetown University (&#147;Georgetown&#148;)
pursuant to which the Company obtained an exclusive, worldwide license to make, have made, use, sell, offer for sale and import of products covered by patent rights <FONT STYLE="white-space:nowrap">co-owned</FONT> by Georgetown. The rights licensed
to the Company are for all therapeutic, prophylactic and diagnostic uses in all disease indications in humans and animals. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Under the terms of the
Georgetown Agreement, the Company paid a <FONT STYLE="white-space:nowrap">one-time</FONT> only, upfront fee of $50 and the Company may be required to pay milestone payments of up to an aggregate of $800 related to commercial sales of a product. The
Company accounted for the acquisition of technology as an asset acquisition because it did not meet the definition of a business. The Company recorded the upfront payment as research and development expense in the consolidated statement of
operations and comprehensive loss because the acquired technology represented <FONT STYLE="white-space:nowrap">in-process</FONT> research and development and had no alternative future use. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Under the Georgetown Agreement, the Company is solely responsible for all development and commercialization activities and costs in its respective
territories. The Company is also responsible for all costs related to the filing, prosecution and maintenance of the licensed patent rights. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">33 </P>

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<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The term of the Georgetown Agreement will continue until the expiration of the last valid claim within the
patent rights covering the product. Georgetown may terminate the agreement in the event (i)&nbsp;the Company fails to pay any amount and fails to cure such failure within 30 days after receipt of notice, (ii)&nbsp;the Company defaults in its
obligation to obtain and maintain insurance and fails to remedy such breach within 45&nbsp;days after receipt of notice, or (iii)&nbsp;the Company declares insolvency or bankruptcy. The Company may terminate the agreement at any time upon at least
60&nbsp;days&#146; written notice. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">During the three months ended March&nbsp;31, 2019 and 2018, the Company did not incur any payment obligations to
Georgetown under the Georgetown Agreement and no milestone payments were made or due under the Georgetown Agreement. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Beth Israel Deaconess Medical
Center Agreement </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In December 2016, the Company entered into a license agreement (the &#147;BIDMC Agreement&#148;) with Beth Israel Deaconess
Medical Center (&#147;BIDMC&#148;), pursuant to which the Company obtained an exclusive, worldwide license to make, have made, use, sell, offer for sale and import of products covered by patent rights <FONT STYLE="white-space:nowrap">co-owned</FONT>
by BIDMC. The rights licensed to the Company are for all fields of use. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Under the terms of the BIDMC Agreement, the Company paid a <FONT
STYLE="white-space:nowrap">one-time</FONT> only, upfront fee of $20 and the Company is responsible for all future patent prosecution costs. The Company accounted for the acquisition of technology as an asset acquisition because it did not meet the
definition of a business. The Company recorded the upfront payment as research and development expense in the consolidated statement of operations and comprehensive loss because the acquired technology represented
<FONT STYLE="white-space:nowrap">in-process</FONT> research and development and had no alternative future use. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The term of the BIDMC Agreement will
continue until the expiration of the last valid claim within the patent rights covering the licensed products. BIDMC may terminate the agreement in the event (i)&nbsp;the Company fails to pay any amount and fails to cure such failure within 15 days
after receipt of notice, (ii)&nbsp;the Company is in material breach of any material provision of the agreement and fails to remedy such breach within 60 days after receipt of notice, or (iii)&nbsp;the Company declares insolvency or bankruptcy. We
may terminate the agreement at any time upon at least 90 days&#146; written notice. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company did not incur any payment obligations under the BIDMC
Agreement during the months ended March&nbsp;31, 2019 and 2018. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Adimab Option and License Agreement </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In February 2017, Arsanis entered into an option and license agreement with Adimab, a related party (the &#147;Adimab Option Agreement&#148;). Under the Adimab
Option Agreement, Adimab has provided to Arsanis certain proprietary antibodies against respiratory syncytial virus (&#147;RSV antibodies&#148;) for its evaluation during a specified option period and has granted Arsanis an exclusive, <FONT
STYLE="white-space:nowrap">non-sublicensable</FONT> license in a specified field under certain Adimab patent rights and <FONT STYLE="white-space:nowrap">know-how</FONT> during the option period. Under the Adimab Option Agreement, the Company has an
exclusive option, exercisable during the option period upon payment of an option fee to Adimab, to require Adimab to assign to the Company all rights in up to a specified number of RSV antibodies selected by the Company and certain patent rights
owned by Adimab that cover these antibodies, and to obtain from Adimab a <FONT STYLE="white-space:nowrap">non-exclusive</FONT> license in a specified field, with the right to grant sublicenses, under certain other patent rights and <FONT
STYLE="white-space:nowrap">know-how</FONT> owned by Adimab. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">If the Company exercises its option under the Adimab Option Agreement, the Company is
required to use commercially reasonable efforts to develop and commercialize at least one product based on a licensed RSV antibody in major markets and is obligated to pay Adimab an option fee of $0.3&nbsp;million and make future milestone payments
upon the achievement of specified clinical and regulatory milestones in the aggregate amount of up to $24.4&nbsp;million. The Company is obligated to pay Adimab royalties at a mid single-digit percentage of net sales of products based on the initial
RSV antibodies (including modified or derivative forms of those antibodies created by or for the Company) by the Company or any of its affiliates, licensees or sublicensees, regardless of whether these products practice any of the assigned or
licensed patents or <FONT STYLE="white-space:nowrap">know-how.</FONT> If the Company materially breaches these diligence obligations, Adimab will have the right to terminate the Adimab Option Agreement. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company has no payment obligations under the Adimab Option Agreement with respect to sales of products based on licensed RSV antibodies to the extent they
are sold at cost in developing countries under the February 2017 Gates Foundation grant agreement, as amended and restated in August 2018, and the August 2018 Gates Foundation grant agreement (which are described in further detail below). However,
if such products are sold in developing countries for an amount that exceeds cost, then the amount of such excess will be subject to the royalty payment obligations described in the preceding paragraph. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">34 </P>

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<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">If the Company does not exercise its option, the Adimab Option Agreement will expire on the Company&#146;s
achievement of specified preclinical milestones under the grant agreements with the Gates Foundation, but in any event no later than <FONT STYLE="white-space:nowrap">mid-2019.</FONT> If the Company does exercise its option, the Adimab Option
Agreement will expire on the <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">last-to-expire</FONT></FONT> royalty term (defined, on a
<FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">product-by-product</FONT></FONT> and <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">country-by-country</FONT></FONT> basis, as the period ending on the later of
twelve years after the first commercial sale of such product in such country and the expiration of the last of a specified set of patents and patent applications covering such product in such country) for any and all products for which the Company
is obligated to pay Adimab royalties under the Adimab Option Agreement. The Company has the right to terminate the Adimab Option Agreement for any reason by providing Adimab with a specified amount of prior written notice. Adimab has the right to
terminate the Adimab Option Agreement if the Company materially breaches the agreement and fails to cure such breach within a specified cure period, including for the Company&#146;s failure to use commercially reasonable efforts to develop and
commercialize at least one product based on a licensed RSV antibody in major markets. If Adimab terminates the Adimab Option Agreement for the Company&#146;s breach, if the Company terminates the agreement for convenience or if the agreement expires
before the Company exercises its option, then the Company must return or destroy certain <FONT STYLE="white-space:nowrap">know-how,</FONT> including all initial RSV antibodies, and all modified or derivative forms of those antibodies, in its
possession other than those for which the Company has made all payments required under the Adimab Option Agreement, assign certain patents covering certain RSV antibodies to Adimab, grant Adimab a
<FONT STYLE="white-space:nowrap">non-exclusive,</FONT> royalty-free license under certain other patents, and grant Adimab a time-limited right of first negotiation to obtain an exclusive license to certain patents and
<FONT STYLE="white-space:nowrap">know-how</FONT> and the transfer and assignment of certain regulatory filings and approvals and other related assets related to products based on licensed RSV antibodies. Certain of the Company&#146;s payment
obligations relating to specified products and patents arising from the agreement survive expiration or termination of the agreement. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">During the three
months ended March&nbsp;31, 2019, the Company recognized no research and development expense in connection with the Adimab Option Agreement. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Adimab
Collaboration Agreement </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In May 2011, Arsanis entered into a collaboration agreement with Adimab, LLC (&#147;Adimab&#148;) and together with
certain applicable option exercise letters the Company has sent to Adimab, the &#147;Adimab Collaboration Agreement&#148;). Under the Adimab Collaboration Agreement, the Company and Adimab were required to use reasonable efforts to conduct certain
research, which was funded by the Company, to discover and optimize antibodies directed against targets selected by the Company. With respect to each target that was the subject of the research, the Company had an exclusive option to obtain, with
respect to a specified number of antibodies directed against such target and discovered or optimized by Adimab, (i)&nbsp;ownership of certain patent rights relating to such antibodies and (ii)&nbsp;exclusive and
<FONT STYLE="white-space:nowrap">non-exclusive</FONT> licenses in a specified field, with the right to grant sublicenses, under certain patent rights and <FONT STYLE="white-space:nowrap">know-how.</FONT> </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Under the Adimab Collaboration Agreement, for each target for which the Company has exercised an option, the Company is required to use commercially
reasonable efforts to develop and commercialize at least one product in major markets. If the Company does not fulfill these diligence obligations, Adimab may consider it a material breach, allowing Adimab to terminate the Adimab Collaboration
Agreement with respect to such target and all associated products. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company is obligated to pay Adimab royalties at a mid single-digit percentage of
net sales made by the Company or its affiliates of products based on antibodies for which the Company exercised its option, or products that use or are based on any antibody discovered or optimized under the agreement, any derivative or modified
version of any such antibody, or any sequence information as to any such antibody. In addition, if the Company sells or licenses to any third party, or otherwise grants rights to any third party to, any of the products for which the Company is
obligated to pay Adimab royalties, either alone or as part of a package including specified patents not directed to these antibodies, the Company is obligated to pay Adimab either (i)&nbsp;the same royalties on net sales of such products by such
third party or (ii)&nbsp;a percentage, ranging from the low double digits to a maximum of less than 30%, of the payments the Company receives from such third parties that are attributable to such grant of rights. In April 2017, the Company entered
into a letter agreement with the Gates Foundation, pursuant to which the Company licensed to the Gates Foundation certain rights under its ASN100&nbsp;program. The Company has no payment obligations under the Adimab Collaboration Agreement with
respect to sales of certain antibody products if they are sold at cost in developing countries under its letter agreement with the Gates Foundation. However, if such products are sold in developing countries for an amount that exceeds cost, then the
amount of such excess over cost will be subject to the royalty payment obligations described above. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">If the Company (or one of its affiliates with rights
under the agreement) undergoes a change in control and, at the time of such change in control, the Company has not sold or licensed to third parties all of its rights in antibodies for which the Company is obligated to pay Adimab royalties under the
agreement, then the Company is obligated to either (i)&nbsp;pay Adimab a percentage, in the mid double digits, of the payments it receives from that change in control that are reasonably attributable to those rights and certain patents arising
</P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">35 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">
from the collaboration or (ii)&nbsp;require the Company&#146;s acquirer and all of its future third-party collaborators to pay to Adimab the royalties at a mid single-digit percentage of net
sales based on those rights. If the Company grants rights to a third party under certain patents that are not directed to the antibodies for which the Company is obligated to pay Adimab royalties (as described above), the Company is also obligated
to pay Adimab, in place of royalties or a percentage of payments received from the third party, a lump sum in the high six digits. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Adimab
Collaboration Agreement will expire on a <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">country-by-country</FONT></FONT> basis twelve years after the first commercial sale in such country of the last product for which the Company
is obligated to pay Adimab royalties in such country under the Adimab Collaboration Agreement. The Company has the right to terminate the Adimab Collaboration Agreement for any reason by providing Adimab with a specified amount of prior written
notice. Adimab has the right to terminate the Adimab Collaboration Agreement if the Company materially breaches the agreement and fails to cure such breach within a specified cure period, including for its failure to use commercially reasonable
efforts to develop and commercialize at least one product directed at a target for which the Company has exercised an option in major markets. If Adimab terminates the Adimab Collaboration Agreement for the Company&#146;s breach, or if the Company
terminates the agreement for convenience, then the Company must transfer or license to Adimab certain rights and assets relating to targets and antibodies for which the Company has exercised its option. Adimab is then obligated to make payments to
the Company with respect to these targets and antibodies that are similar to the payments the Company is required to make to Adimab during the term of the agreement. Certain of the Company&#146;s payment obligations relating to specified products
and patents arising from the agreement survive expiration or termination of the agreement. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">During the three months ended March&nbsp;31, 2019, the Company
did not recognize any research and development under the Adimab Collaboration Agreement. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Gates Foundation Grant Agreements </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In February 2017, Arsanis entered into a grant agreement with the Gates Foundation (&#147;Grant Agreement&#148;), under which the Gates Foundation agreed to
provide the Company up to approximately $9,300 to conduct preclinical development of monoclonal antibodies for the prevention of RSV infection in newborns (the &#147;RSV project&#148;). </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In connection with this Grant Agreement, the Company has granted to the Gates Foundation a <FONT STYLE="white-space:nowrap">non-exclusive,</FONT> perpetual,
royalty-free, fully paid up, sublicensable license to make, use, sell, offer to sell, import, distribute, copy, modify, create derivative works, publicly perform and display the funded developments and, to the extent incorporated into a funded
development or required to use a funded development, any other technology created outside of the RSV project that was used as part of the RSV project, for the benefit of people in developing countries. This license survives any expiration or
termination of the grant agreement. The Grant Agreement expires on October&nbsp;31, 2019. The Gates Foundation can modify, suspend or discontinue any payment under the grant agreement, or terminate the grant agreement, if it is not reasonably
satisfied with the Company&#146;s progress on the RSV project; if there are significant changes to the Company&#146;s leadership or other factors that the Gates Foundation reasonably believes may threaten the RSV project&#146;s success; if the
Company undergoes a change in control; if there is a change in the Company&#146;s tax status; if the RSV project is no longer aligned with the Gates Foundation&#146;s programmatic strategy; or if the Company fails to comply with the grant agreement.
Any grant funds that have not been used for, or committed to, the RSV project upon the expiration or termination of the grant agreement must be returned to the Gates Foundation or otherwise used as directed by the Gates Foundation.<I> </I>In August
2018, Arsanis entered into an amended and restated grant agreement which replaced the February 2017 grant agreement in its entirety. The amended and restated grant agreement includes amendments to conform to current Gates Foundation audit,
reporting, and other administrative requirements, as well as to make the perpetual Gates Foundation license grant described below irrevocable. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">During the
three months ended March&nbsp;31, 2019, the Company did not incur qualifying expenses under the letter agreement with the Gates Foundation. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Research and Development Incentive Program </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The
Company participates in a research and development incentive program provided by the Austrian government whereby the Company is entitled to reimbursement by the Austrian government for a percentage of qualifying research and development expenses
incurred by the Company&#146;s subsidiary in Austria. Under the program, the reimbursement rate for qualifying research and development expenses incurred by the Company through its subsidiary in Austria is 14% for the current year . </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company recognizes incentive income from Austrian research and development incentives when qualifying expenses have been incurred, there is reasonable
assurance that the payment will be received, and the consideration can be reliably measured. Management has assessed the Company&#146;s research and development activities and expenditures to determine which activities and expenditures are likely to
be eligible under the research and development incentive program described above. At each reporting date, management estimates the reimbursable incentive income available to the Company based on available information at the time. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">36 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As of March&nbsp;31, 2019, the Company recorded receivables for amounts due under the program of
$1.6&nbsp;million, which amounts were included in grant and incentive receivables in the consolidated balance sheet. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Janssen License and Option
Agreement </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On December&nbsp;12, 2018, Arsanis entered into a patent license and option agreement with Janssen Pharmaceuticals, Inc.
(&#147;Janssen&#148;), (the &#147;Janssen License and Option Agreement&#148;). Pursuant to the Janssen License and Option Agreement, Arsanis granted to Janssen (i)&nbsp;a <FONT STYLE="white-space:nowrap">non-exclusive</FONT> license to specified
patents in Arsanis&#146;s portfolio related to the ASN200 E. coli program, and (ii)&nbsp;an option for Janssen to acquire these patents in the future if specified conditions are met. Janssen agreed to pay Arsanis $3.5&nbsp;million within 15 business
days after the December&nbsp;12, 2018 effective date of the Janssen License and Option Agreement, in addition to a future $0.5&nbsp;million payment in the event Janssen exercises its option to acquire the relevant patents. Arsanis received the
$3.5&nbsp;million payment from Janssen in December 2018 and recognized this amount as revenue. Such revenue is not reflected in the consolidated financial statements of the Company as it occurred prior to the Merger. Janssen&#146;s option to the
relevant patents will be recognized as revenue in full in the period in which the option exercise occurs. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>14.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>Income Taxes </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company did not record a federal or state income tax benefit for its losses for the three months ended March&nbsp;31, 2019 and 2018 due to the conclusion
that a full valuation allowance is required against the Company&#146;s deferred tax assets. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>15.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>Net Loss per Share </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Basic and diluted net loss per share attributable to common stockholders was calculated as follow: </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="76%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="75%"></TD>
<TD VALIGN="bottom" WIDTH="6%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="6%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Three Months Ended<BR>March&nbsp;31,</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;2019&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;2018&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Numerator:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net loss</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(10,873</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(7,367</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Accruing dividends on Series A convertible preferred stock</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(592</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(740</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net loss attributable to common stockholders</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(11,465</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(8,107</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Denominator:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Weighted average common shares outstanding&#151;basic and diluted</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,717,808</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">457,971</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net loss per share attributable to common stockholders&#151;basic and diluted</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(6.67</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(17.70</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company has included 107,371 shares of redeemable common stock in its computation of basic and diluted weighted average
common shares outstanding for the three months ended March&nbsp;31, 2019 and 2018 as this class of stock participates in losses similarly to other common stockholders. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company&#146;s potentially dilutive securities included outstanding stock options, convertible preferred stock, and warrants to purchase shares of
convertible preferred stock for the three month period ended March&nbsp;31, 2018 and included outstanding stock options and warrants to purchase common stock for the three month period ended March&nbsp;31, 2019. These potentially dilutive securities
have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share, and thus they are considered &#147;anti-dilutive.&#148; Therefore, the weighted average number of common shares
outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end and
adjusted for the Exchange Ratio and Reverse Stock Split, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect: </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">37 </P>

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<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Amounts in thousands, except share and per share amounts) </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Unaudited) </B></P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="76%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="76%"></TD>
<TD VALIGN="bottom" WIDTH="3%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="3%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Three Months Ended<BR>March&nbsp;31,</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;2019&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>&nbsp;&nbsp;&nbsp;&nbsp;2018&nbsp;&nbsp;&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Options to purchase common stock</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,037,089</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">538,429</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Convertible preferred stock (as converted to common stock)</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">3,556,147</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Warrants to purchase common stock (presented on an
<FONT STYLE="white-space:nowrap">as-converted,</FONT> as exchanged, split-adjusted basis.</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">493,927</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">423,416</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,531,016</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4,517,992</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>16.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>Subsequent Events </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On April&nbsp;12, 2019, the Company entered into an underwriting agreement with Cowen and Company, LLC and Stifel, Nicolaus&nbsp;&amp; Company, Incorporated,
as representatives of the several underwriters named therein pursuant to which it sold 5,670,000 shares of common stock and, in lieu of common stock, <FONT STYLE="white-space:nowrap">pre-funded</FONT> warrants to purchase 2,130,000 shares of common
stock, and accompanying Class&nbsp;A warrants to purchase 3,900,000 shares of its common stock, at a price to the public of $11.00 per share and accompanying Class&nbsp;A warrants (or $10.999 per <FONT STYLE="white-space:nowrap">pre-funded</FONT>
warrant and accompanying Class&nbsp;A warrants). The Class&nbsp;A warrants have an exercise price of $13.20, will expire five years from the date of issuance, and are immediately exercisable with certain restrictions. The gross proceeds from the
offering were $85.8&nbsp;million before deducting underwriting discounts and estimated offering expenses. The offering closed on April&nbsp;16, 2019. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">38 </P>

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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="8%" VALIGN="top" ALIGN="left"><B><A NAME="tx726255_10"></A>Item&nbsp;2.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>MANAGEMENT&#146;S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS
</B></P></TD></TR></TABLE> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>You should read the following discussion and analysis of our financial condition and results of operations together with our
consolidated financial statements and the related notes included elsewhere in this Quarterly Report on Form <FONT STYLE="white-space:nowrap">10-Q.</FONT> Some of the information contained in this discussion and analysis or set forth elsewhere in
this Quarterly Report on Form <FONT STYLE="white-space:nowrap">10-Q,</FONT> including information with respect to our plans and strategy for our business and related financing, includes forward-looking statements that involve risks, uncertainties
and assumptions. Our actual results, performance or experience could differ materially from what is indicated by any forward-looking statement due to various important factors, risks and uncertainties, including, but not limited to, those set forth
under &#147;Cautionary Note Regarding Forward-Looking Statements&#148; included elsewhere in this Quarterly Report on Form <FONT STYLE="white-space:nowrap">10-Q</FONT> or under &#147;Risk Factors&#148; in Item 1A of Part I of our Annual Report on
Form <FONT STYLE="white-space:nowrap">10-K</FONT> for the fiscal year ended December&nbsp;31, 2018, as updated by our Current Report on Form <FONT STYLE="white-space:nowrap">8-K</FONT> filed on April&nbsp;11, 2019 and our subsequent filings under
the Exchange Act. </I></P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Overview </B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">We are a
clinical-stage biopharmaceutical company focused on the discovery, development and commercialization of novel therapeutics for the treatment of rare diseases. Our pipeline is comprised of potentially <FONT STYLE="white-space:nowrap"><FONT
STYLE="white-space:nowrap">first-in-class,</FONT></FONT> oral, small molecule antagonists of chemokine receptor CXCR4, which have the potential to treat a broad range of rare diseases, including primary immunodeficiencies, or PIs, and certain types
of cancer. CXCR4 is stimulated by its only chemokine ligand, CXCL12, and plays a key role in enabling the trafficking of immune cells and effectively monitoring the function of the immune system, or immunosurveillance. Overstimulation of the
CXCL12/CXCR4 pathway leads to inhibition of the immune response, or immunosuppression. Our lead product candidate, mavorixafor <FONT STYLE="white-space:nowrap">(X4P-001),</FONT> has completed a Phase 2 clinical trial in patients with Warts,
Hypogammaglobulinemia, Infections, and Myelokathexis, or WHIM, syndrome, which is a PI. We plan to initiate a Phase 3 pivotal clinical trial of mavorixafor for the treatment of patients with WHIM syndrome in the second quarter of 2019 and report <FONT
STYLE="white-space:nowrap">top-line</FONT> data from this trial in 2021. Beyond WHIM syndrome, we plan to initiate a Phase 1 clinical trial of mavorixafor in another PI, severe congenital neutropenia, or SCN, and a Phase 1/2 clinical trial of
mavorixafor in Waldenstr&ouml;m macroglobulinemia, or WM, in 2019. We expect to report data from the SCN trial in the middle of 2020 and data from the WM trial in the second half of 2020. We were founded and are led by a team with extensive product
development and commercialization expertise, including several former members of the Genzyme leadership team, and we are located in Cambridge, Massachusetts. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Recent Developments </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Reverse Merger </I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On March&nbsp;13, 2019, X4 Pharmaceuticals, Inc., formerly Arsanis, Inc. (the &#147;Company&#148;), completed a business combination with X4 Therapeutics,
Inc., formerly X4 Pharmaceuticals, Inc. (&#147;X4&#148;), in accordance with the terms of the Agreement and Plan of Merger, dated as of November&nbsp;26, 2018, as amended on December&nbsp;20, 2018 and March&nbsp;8, 2019 (the &#147;Merger
Agreement&#148;), by and among the Company, X4 and Artemis AC Corp., a Delaware corporation and a wholly owned subsidiary of the Company (&#147;Merger Sub&#148;), pursuant to which, among other matters, Merger Sub merged with and into X4 with X4
continuing as a wholly owned subsidiary of the Company and the surviving corporation of the merger (the &#147;Merger&#148;). Following the completion of the Merger on March&nbsp;13, 2019, the the Company effected a <FONT STYLE="white-space:nowrap"><FONT
STYLE="white-space:nowrap">1-for-6</FONT></FONT> reverse stock split of its common stock (the &#147;Reverse Stock Split&#148;) and changed its name to &#147;X4 Pharmaceuticals, Inc.&#148; Following the completion of the Merger, the business
conducted by the combined organization became primarily the business conducted by X4. Unless noted otherwise, all references to common stock share and per share amounts reflect the Reverse Stock Split. As used herein, the words &#147;the
Company,&#148; &#147;we,&#148; &#147;us,&#148; and &#147;our&#148; refer to, for periods following the Merger, X4 Pharmaceuticals, Inc. (formerly Arsanis, Inc.), together with is direct and indirect subsidiaries, and for periods prior to the Merger,
X4 Therapeutics, Inc. (formerly X4 Pharmaceuticals, Inc.), and its direct and indirect subsidiaries, as applicable. In addition, the word &#147;Arsanis&#148; refers to the Company prior to the completion of the Merger. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Under the terms of the Merger Agreement, at the closing of the Merger, the Company issued an aggregate of approximately 25.7&nbsp;million shares of its common
stock to X4 stockholders, based on a common stock exchange ratio of 0.5702 shares of the Company&#146;s common stock for each share of X4&#146;s common stock outstanding immediately prior to the Merger and a preferred stock exchange ratio of 0.5702
shares of the Company&#146;s common stock for each share of X4 preferred stock outstanding prior to the Merger, in each case before taking into account of the Reverse Stock Split (each such exchange ratio, the &#147;Exchange Ratio&#148;). The
Company also assumed all of the outstanding and unexercised stock options and warrants to purchase shares of X4 capital stock, with the number of shares subject to such options or warrants representing the right to purchase a number of shares of the
Company&#146;s common stock equal to 0.5702 multiplied by the number of shares of X4 capital stock previously represented by such options or warrants, before taking into account the Reverse Stock Split. The exercise prices of such options and
warrants were also appropriately adjusted to reflect the Exchange Ratio of 0.5702, before taking into account the Reverse Stock Split. As a result of the Reverse Stock Split, the number of shares subject to such options and warrants and the exercise
prices of such options and warrants were further adjusted by decreasing the number of shares subject to such options and warrants and increasing the exercise price of such options and warrants on a <FONT STYLE="white-space:nowrap"><FONT
STYLE="white-space:nowrap">1-for-6</FONT></FONT> </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">39 </P>

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<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">
Reverse Stock Split basis. The assumed options continue to be governed by the terms of the X4 Therapeutics, Inc. 2015 Employee, Director and Consultant Equity Incentive Plan, as amended, under
which the options were originally granted (the &#147;X4 Therapeutics Plan&#148;). Upon the closing of the Merger, X4 Pharmaceuticals, Inc. also assumed the X4 Therapeutics Plan. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Immediately following the Merger and the Reverse Stock Split, there were approximately 6.7&nbsp;million shares of the X4 Pharmaceuticals, Inc. common stock
outstanding, and the former X4 Therapeutics, Inc. stockholders owned approximately 4.3&nbsp;million shares, or 63.7% of the combined organization&#146;s common stock outstanding. In addition, immediately following the Merger and the Reverse Stock
Split, the former X4 Pharmaceuticals, Inc. optionholders held options to purchase approximately 0.8&nbsp;million shares of the combined organization&#146;s common stock and the former X4 Pharmaceuticals, Inc. warrantholders held warrants to purchase
approximately 0.5&nbsp;million shares of the combined organization&#146;s common stock. Approximately 24.3% of our common stock outstanding immediately after the Merger is held by stockholders subject to
<FONT STYLE="white-space:nowrap">lock-up</FONT> restrictions, pursuant to which such stockholders have agreed, except in limited circumstances, not to sell or transfer, or engage in swap or similar transactions with respect to, shares of the
combined organization&#146;s common stock, including, as applicable, shares received in the Merger and issuable upon exercise of certain warrants and options, for a period of 180 days following the closing of the Merger. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The business combination has been accounted for as a &#147;reverse merger&#148; in accordance with GAAP. Under this method of accounting,
X4&nbsp;Therapeutics, Inc. is deemed to be the accounting acquirer for financial reporting purposes. This determination was primarily based on the facts that, immediately following the Merger: (i)&nbsp;the stockholders of X4 own a substantial
majority of the voting rights in the combined organization, (ii)&nbsp;X4 designated a majority of the members of the initial board of directors of the combined organization and (iii)&nbsp;X4&#146;s senior management hold all key positions in the
senior management of the combined organization. Accordingly, for accounting purposes, the business combination has been treated as the equivalent of X4 issuing stock to acquire the net assets of Arsanis. As a result, as of the closing date of the
Merger, the net assets of Arsanis have been recorded at their acquisition-date fair values in the financial statements of the combined entity and the reported operating results prior to the business combination will be those of X4. Subsequent to the
closing of the Merger, the reported operating results will reflect those of the combined organization. In addition, transaction costs incurred by X4 in connection with the business combination have been expensed as incurred. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Our common stock remained listed on the Nasdaq Stock Market, with trading having commenced on a post-Reverse Stock Split basis and under the new name as of
March&nbsp;14, 2019. The trading symbol also changed on that date from &#147;ASNS&#148; to &#147;XFOR.&#148; </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Equity Financing </I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On April&nbsp;16, 2019, we sold 5,670,000 shares of common stock and, in lieu of common stock, <FONT STYLE="white-space:nowrap">pre-funded</FONT> warrants to
purchase 2,130,000 shares of common stock, and accompanying Class&nbsp;A warrants to purchase 3,900,000 shares of our common stock at a price to the public of $11.00 per share and accompanying Class&nbsp;A warrants (or $10.999 per <FONT
STYLE="white-space:nowrap">pre-funded</FONT> warrant and accompanying Class&nbsp;A warrants).&nbsp;The Class&nbsp;A warrants have an exercise price of $13.20, will expire five years from the date of issuance, and are immediately exercisable with
certain restrictions. The gross proceeds from the offering were $85.8&nbsp;million before deducting underwriting discounts and estimated offering expenses. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Operating History </I></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Since our inception in 2012, we have
devoted substantially all of our efforts and financial resources to organizing and staffing the company, business planning, raising capital, acquiring or discovering product candidates and securing related intellectual property rights and conducting
discovery, research and development activities for our product candidates. We do not have any products approved for sale and have not generated any revenue from product sales. Through December&nbsp;31, 2018, we have funded our operations primarily
with proceeds from sales of preferred stock and proceeds from the issuance of convertible debt and borrowings under loan and security agreements. Through December&nbsp;31, 2018, we had received net proceeds of $73.7&nbsp;million from sales of our
preferred stock (including proceeds from convertible debt, which converted into preferred stock) and gross proceeds of $16.0&nbsp;million from borrowings under loan and security agreements, net of amounts used to repay prior loan and security
agreements. During the three months ended March&nbsp;31, 2019 as a result of our Merger with Arsanis, we acquired $25.8&nbsp;million of cash and short-term marketable securities of Arsanis. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">We have incurred significant operating losses since inception. Our ability to generate product revenue sufficient to achieve profitability will depend heavily
on the successful development and eventual commercialization of one or more of our current or future product candidates. Our net losses were $10.9&nbsp;million and $6.2&nbsp;million for the three months ended March&nbsp;31, 2019 and 2018,
respectively. As of March&nbsp;31, 2019, we had an accumulated deficit of $90.1&nbsp;million. We expect to continue to incur significant expenses and increasing operating losses for at least the next several years. We expect that our expenses and
capital requirements will increase substantially in connection with our ongoing activities, particularly if and as we: </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">conduct additional clinical trials for our product candidates; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">continue to discover and develop additional product candidates; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">acquire or <FONT STYLE="white-space:nowrap">in-license</FONT> other product candidates and
technologies;</P></TD></TR></TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">40 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>

<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">maintain, expand and protect our intellectual property portfolio; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">hire additional clinical, scientific and commercial personnel; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">establish a commercial manufacturing source and secure supply chain capacity sufficient to provide commercial
quantities of any product candidates for which we may obtain regulatory approval; </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">seek regulatory approvals for any product candidates that successfully complete clinical trials;
</P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">establish a sales, marketing and distribution infrastructure to commercialize any products for which we may
obtain regulatory approval; and </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">add operational, financial and management information systems and personnel, including personnel to support our
product development and planned future commercialization efforts, as well as to support our efforts as a public reporting company. </P></TD></TR></TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">We
will not generate revenue from product sales unless and until we successfully complete clinical development and obtain regulatory approval for our product candidates. If we obtain regulatory approval for any of our product candidates and do not
enter into a commercialization partnership, we expect to incur significant expenses related to developing our internal commercialization capability to support product sales, marketing and distribution. Further, we expect to incur additional costs
associated with operating as a public company. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As a result, we will need substantial additional funding to support our continuing operations and pursue
our growth strategy. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through the sale of equity, debt financings or other capital sources, which may include collaborations with
other companies or other strategic transactions. We may not be able to raise additional funds or enter into such other agreements or arrangements when needed on favorable terms, or at all. If we fail to raise capital or enter into such agreements as
and when needed, we may have to significantly delay, reduce or eliminate the development and commercialization of one or more of our product candidates or delay our pursuit of potential <FONT STYLE="white-space:nowrap">in-licenses</FONT> or
acquisitions. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Because of the numerous risks and uncertainties associated with product development, we are unable to predict the timing or amount of
increased expenses or when or if we will be able to achieve or maintain profitability. Even if we are able to generate product sales, we may not become profitable. If we fail to become profitable or are unable to sustain profitability on a
continuing basis, then we may be unable to continue our operations at planned levels and be forced to reduce or terminate our operations. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">We expect that
our existing cash and cash equivalents of $22.3&nbsp;million as of March&nbsp;31, 2019, together with the $78.9&nbsp;million of net proceeds from our equity financing in April 2019, will be sufficient to fund our operating expenses, capital
expenditure requirements and debt service payments for at least the next 12 months. See &#147;<I> &#151;Liquidity and Capital Resources</I>.&#148;&nbsp;&nbsp;&nbsp;&nbsp;We will need to raise additional capital to finance our operations, which
cannot be assured. See Note 1 of our consolidated financial statements included elsewhere in this Quarterly Report on Form <FONT STYLE="white-space:nowrap">10-Q</FONT> for additional information on our assessment. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Components of Results of Operations </B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Revenue
</I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">To date, we have not generated any revenue from product sales and do not expect to generate any revenue from the sale of products in the
foreseeable future. If our development efforts for our product candidates are successful and result in regulatory approval, we may generate revenue in the future from product sales. We cannot predict if, when, or to what extent we will generate
revenue from the commercialization and sale of our product candidates. We may never succeed in obtaining regulatory approval for any of our product candidates. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Operating Expenses </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Research and Development
Expenses </I></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Research and development expenses consist primarily of costs incurred in connection with the discovery and development of our product
candidates. We expense research and development costs as incurred. These expenses include: </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">employee-related expenses, including salaries, related benefits and stock-based compensation expense, for
employees engaged in research and development functions; </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">expenses incurred in connection with the preclinical and clinical development of our product candidates,
including under agreements with third parties, such as consultants and contract research organizations, or CROs; </P></TD></TR></TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">41 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>

<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the cost of manufacturing drug products for use in our preclinical studies and clinical trials, including under
agreements with third parties, such as consultants and contract manufacturing organizations, or CMOs; </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">facilities, depreciation and other expenses, which include direct or allocated expenses for rent and maintenance
of facilities and insurance; </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">costs related to compliance with regulatory requirements; and </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">payments made under third-party licensing agreements. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">We recognize external development costs based on an evaluation of the progress to completion of specific tasks using information provided to us by our service
providers. This process involves reviewing open contracts and purchase orders, communicating with our personnel to identify services that have been performed on our behalf, and estimating the level of service performed and the associated cost
incurred for the service when we have not yet been invoiced or otherwise notified of actual costs. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are recorded as
prepaid expenses. Such amounts are recognized as an expense when the goods have been delivered or the services have been performed, or when it is no longer expected that the goods will be delivered or the services rendered. Upfront payments,
milestone payments and annual maintenance fees under license agreements are expensed in the period in which they are incurred. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Our direct research and
development expenses are tracked by product candidate and consist primarily of external costs, such as fees paid to outside consultants, CROs, CMOs and research laboratories in connection with our preclinical development, process development,
manufacturing and clinical development activities. Our direct research and development expenses by product candidate also include fees incurred under third-party license agreements. We do not allocate employee costs and costs associated with our
discovery efforts, laboratory supplies and facilities, including depreciation or other indirect costs, to specific product candidates because these costs are deployed across multiple programs and, as such, are not separately classified. We use
internal resources primarily to conduct our research and discovery as well as for managing our preclinical development, process development, manufacturing and clinical development activities. These employees work across multiple programs and,
therefore, we do not track our costs by product candidate. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The table below summarizes our research and development expenses incurred by product
candidate: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="76%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="82%"></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Three&nbsp;Months&nbsp;Ended</B><br><B>March&nbsp;31,</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2019</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2018</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Mavorixafor</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">2,851</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">3,010</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><FONT STYLE="white-space:nowrap">X4P-002</FONT></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">84</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><FONT STYLE="white-space:nowrap">X4P-003</FONT></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">8</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Unallocated research and development expenses</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2,712</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,734</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total research and development expenses</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">5,655</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">4,744</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Research and development activities are central to our business model. Product candidates in later stages of clinical
development generally have higher development costs than those in earlier stages of clinical development, primarily due to the increased size and duration of later-stage clinical trials. As a result, we expect that our research and development
expenses will increase substantially over the next several years as we plan to initiate a Phase 3 pivotal clinical trial of mavorixafor for the treatment of patients with WHIM syndrome in the second quarter of 2019 and to initiate a Phase 1 clinical
trial of mavorixafor in SCN and a Phase 1/2 clinical trial of mavorixafor in WM in 2019. In addition, we expect research and development expenses to increase related to conducting preclinical development and pursuing initial clinical stages of our
product candidates <FONT STYLE="white-space:nowrap">X4P-002</FONT> and <FONT STYLE="white-space:nowrap">X4P-003.</FONT> </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The successful development and
commercialization of our product candidates is highly uncertain. At this time, we cannot reasonably estimate or know the nature, timing and costs of the efforts that will be necessary to complete the preclinical and clinical development of any of
our product candidates. This is due to the numerous risks and uncertainties associated with product development and commercialization, including the following: </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the timing and progress of preclinical and clinical development activities; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the number and scope of preclinical and clinical programs that we decide to pursue; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">our ability to maintain our current research and development programs and to establish new ones;
</P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">establishing an appropriate safety profile with Investigational New Drug, or IND,-enabling studies;
</P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">successful patient enrollment in, and the initiation and completion of, clinical trials; </P></TD></TR></TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">42 </P>

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<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>

<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the receipt of regulatory approvals from applicable regulatory authorities; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the successful completion of clinical trials with safety, tolerability and efficacy profiles that are
satisfactory to the U.S Food and Drug Administration, or FDA, or any comparable foreign regulatory authority; </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the timing, receipt and terms of any marketing approvals from applicable regulatory authorities;
</P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">our ability to establish new licensing or collaboration arrangements; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">establishing agreements with third-party manufacturers for clinical supply for our clinical trials and commercial
manufacturing, if any of our product candidates is approved; </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">development and timely delivery of clinical-grade and commercial-grade drug formulations that can be used in our
clinical trials and for commercial launch; </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">obtaining, maintaining, defending and enforcing patent claims and other intellectual property rights;
</P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">launching commercial sales of our product candidates, if approved, whether alone or in collaboration with others;
and </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">maintaining a continued acceptable safety profile of the product candidates following approval.
</P></TD></TR></TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">A change in the outcome of any of these variables with respect to the development of our product candidates could significantly change
the costs and timing associated with the development of that product candidate. We may never succeed in obtaining regulatory approval for any of our product candidates. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>General and Administrative Expenses </I></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">General and
administrative expenses consist primarily of salaries and related costs, including stock-based compensation, for personnel in executive, finance and administrative functions. General and administrative expenses also include direct and allocated
facility-related costs as well as professional fees for legal, patent, consulting, investor and public relations, accounting, and audit services. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">We
anticipate that our general and administrative expenses will increase in the future as we increase our headcount to support our continued research activities and development of our product candidates. We also anticipate that we will incur increased
accounting, audit, legal, regulatory, compliance and director and officer insurance costs as well as investor and public relations expenses associated with being a public company. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Other Income (Expense), Net </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Interest Income
</I></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Interest income consists of interest earned on our cash equivalents, which consist of money market funds. Our interest income has not been significant
due to low interest rates earned on invested balances. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Interest Expense </I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">For the three months ended March&nbsp;31, 2019, interest expense primarily consists of interest on outstanding borrowings under our Hercules Loan Agreement,
which was entered into with Hercules Capital, Inc., or Hercules, in October 2018. Interest expense in the current period also includes interest on loans acquired from Arsanis (see discussion of the FFG loan agreement in &#147;Liquidity and Capital
Resources&#148;). For the three months ended March&nbsp;31, 2018, interest expense consisted of interest on outstanding borrowing under the 2016 loan and security agreement with Silicon Valley Bank, or SVB, which we refer to as the SVB Loan
Agreement, as well as amortization of debt issuance costs and accretion of a final payment payable upon the maturity or the repayment in full of all obligations under the SVB Loan Agreement. In October 2018, in connection with entering into the
Hercules Loan Agreement, all amounts due under the SVB Loan Agreement, including unpaid principal of $4.3&nbsp;million and a final payment $0.3&nbsp;million, were repaid with proceeds from the Hercules Loan Agreement, and the SVB Loan Agreement was
terminated. We expect that our interest expense will increase in 2019 as compared to 2018 in connection with our Hercules Loan Agreement, under which we borrowed $8.0&nbsp;million in October 2018 and an additional $2.0&nbsp;million in December 2018,
and as a result of the FFG loan agreement, under which borrowings were $9.5&nbsp;million as of March&nbsp;31, 2019. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Change in Fair Value of Preferred
Stock Warrant Liability </I></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In connection with our Series A and Series B preferred stock financings in 2015, 2017 and 2018, and entering into the SVB Loan
Agreement in 2016 and in connection with entering into the Hercules Loan Agreement in October 2018, we issued warrants to purchase shares of our preferred stock. Due to the liquidation requirements of these preferred shares, we classified these
warrants as a liability on our consolidated balance sheet, which was remeasured to fair value at each reporting date with changes in the fair value reported as a component of other income (expense), net in our consolidated statements of operations
and comprehensive loss. Upon the closing of the Merger on March&nbsp;13, 2019, all of our outstanding preferred stock warrants become exercisable for Arsanis common </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">43 </P>

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<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">
stock; accordingly, the liability as of March&nbsp;13, 2019 for these warrants was remeasured to fair value and reclassified to additional <FONT STYLE="white-space:nowrap">paid-in</FONT> capital.
As a result, following the closing of the Merger, we will no longer recognize changes in the fair value of the warrant liability as other income (expense), net in our consolidated statements of operations and comprehensive loss. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Change in Fair Value of Derivative Liability </I></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Our license
agreement with Genzyme, a Sanofi company, contains a contingent payment obligation that requires that we make a payment to Genzyme upon a change of control event. The contingent payment obligation meets the definition of a derivative instrument. We
classify this derivative as a liability on our consolidated balance sheet that we remeasure to fair value at each reporting date, and we recognize changes in the fair value of the derivative liability as a component of other income (expense), net in
our consolidated statement of operations and comprehensive loss. We will continue to recognize changes in the fair value of the derivative liability until a change of control event occurs or until the license agreement is terminated. The Merger with
Arsanis qualifies as a change of control event, as defined in the license agreement. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Loss on Preferred Stock Repurchase Liability </I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In October 2017, we entered into a stock repurchase agreement with a holder of Series Seed preferred stock for the repurchase of shares of Series Seed
preferred stock. We concluded that the arrangement was a freestanding financial instrument that was required to be recorded as a liability at fair value. Upon entering into the repurchase agreement, we recorded a preferred stock repurchase liability
on our consolidated balance sheet of $587 for the fair value of the financial instrument and recognized a corresponding expense as a component of other income (expense), net in our consolidated statements of operations and comprehensive loss. We
subsequently remeasured the repurchase liability to fair value at each reporting date through the settlement date of the repurchase agreement in January 2018 and recognized changes in the fair value of the preferred stock repurchase liability as a
component of other income (expense), net in our consolidated statements of operations and comprehensive loss for the three months ended March&nbsp;31, 2018. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Income Taxes </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Since our inception, we have not
recorded any income tax benefit for the net losses we have incurred in each year or for our earned research and development tax credits, as we believe, based upon the weight of available evidence, that it is more likely than not that all of our net
operating loss carryforwards and tax credits will not be realized. Accordingly, we have recorded a full valuation allowance against our net deferred tax assets at each balance sheet date. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Results of Operations </B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Comparison of the Three
Months Ended March&nbsp;31, 2019 and 2018 </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The following table summarizes our results of operations for the three months ended March&nbsp;31, 2019
and 2018: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="84%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="72%"></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Three Months Ended</B><br><B>March&nbsp;31,</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD COLSPAN="2" VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2019</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2018</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Change</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="10" ALIGN="center"><B>(in thousands)</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Operating expenses:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Research and development</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">5,655</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">4,744</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">911</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">General and administrative</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4,783</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">1,366</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">3,417</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total operating expenses</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">10,438</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">6,110</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4,328</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Loss from operations</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(10,438</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(6,110</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(4,328</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Other income (expense):</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Interest income</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">69</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">69</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Interest expense</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(399</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(169</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(230</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Change in fair value of preferred stock warrant and derivative liabilities</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(105</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(1,157</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,052</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total other income (expense), net</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(435</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(1,257</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">822</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net loss</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(10,873</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(7,367</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(3,506</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">44 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Research and Development Expenses </I></P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="84%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="76%"></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Three&nbsp;Months&nbsp;Ended</B><br><B>March&nbsp;31,</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD COLSPAN="2" VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2019</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2018</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Change</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="10" ALIGN="center"><B>(in thousands)</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Direct research and development expenses by product candidate:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Mavorixafor <FONT STYLE="white-space:nowrap">(X4P-001)</FONT></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">2,851</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">3,010</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(159</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><FONT STYLE="white-space:nowrap">X4P-002</FONT></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">84</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">84</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"><FONT STYLE="white-space:nowrap">X4P-003</FONT></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">8</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">8</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Unallocated research and development expenses:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Personnel related (including stock-based compensation)</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2,200</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,034</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">1,166</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Other</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">512</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">699</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(187</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:5.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Total research and development expenses</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">5,655</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">4,744</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">911</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Research and development expenses were $5.7&nbsp;million for the three months ended March&nbsp;31, 2019, compared to
$4.7&nbsp;million for the three months ended March&nbsp;31, 2018. The increase of $1.0&nbsp;million was primarily due to an increase of $1.0&nbsp;million in unallocated research and development costs, primarily associated with personnel and other
costs associated with the research and development site in Vienna, Austria, acquired in the Merger and an increase of $0.2&nbsp;million in direct expenses of our mavorixafor development program, partially offset by a net decrease of
$0.2&nbsp;million in external costs related to our product candidates. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Direct expenses of our mavorixafor product candidate decreased by
$0.2&nbsp;million in the three months ended March&nbsp;31, 2019, compared to the three months ended March&nbsp;31, 2018. The decrease was primarily due to a decrease in costs associated with product manufacturing and clinical trials as the WHIM
Phase&nbsp;2 and Phase&nbsp;1/2 for the treatment of patients with clear cell renal cell carcinoma, or ccRCC, wind down. We expect that our research and development expenses for mavorixafor will increase substantially over the next several years as
we plan to initiate a Phase 3 pivotal clinical trial of mavorixafor for the treatment of patients with WHIM syndrome in the second quarter of 2019 and to initiate a Phase 1 clinical trial of mavorixafor in SCN and a Phase 1/2 clinical trial of
mavorixafor in WM in 2019. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Direct expenses of our <FONT STYLE="white-space:nowrap">X4P-002</FONT> product candidate increased $0.1&nbsp;million in three
months ended March&nbsp;31, 2019, compared to the three months ended March&nbsp;31, 2018. We had no direct costs related to the <FONT STYLE="white-space:nowrap">X4P-002</FONT> product candidate during the three months ended March&nbsp;31, 2018 as we
paused the development of <FONT STYLE="white-space:nowrap">X4P-002</FONT> in favor of focusing our resources on the development of our mavorixafor product candidate. We expect that our research and development expenses for <FONT
STYLE="white-space:nowrap">X4P-002</FONT> will increase over the next several years as we resume work on <FONT STYLE="white-space:nowrap">X4P-002&#146;s</FONT> preclinical development and initial clinical stage activities. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Unallocated research and development expenses were $2.7&nbsp;million for the three months ended March&nbsp;31, 2019, compared to $1.7&nbsp;million for the
three months ended March&nbsp;31, 2018. The increase of $1.0&nbsp;million was primarily due to an increase of $1.2&nbsp;million in personnel-related costs due to the hiring of additional personnel in our research and development function, partially
offset by a net decrease of $0.2&nbsp;million in external costs related to our product candidates. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>General and Administrative Expenses </I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">General and administrative expenses were $4.8&nbsp;million for the three months ended March&nbsp;31, 2019, compared to $1.4&nbsp;million for the three months
ended March&nbsp;31, 2018. The increase of $3.4&nbsp;million was primarily due to a $1.9&nbsp;million increase in professional fees and a $1.4&nbsp;million increase in personnel-related costs. Professional fees increased due to higher audit, legal
and market research expenses particularly related to the merger, as well as legal costs incurred in connection with maintaining and registering worldwide patents and costs associated with our ongoing business operations. Personnel-related costs for
the three months ended March&nbsp;31, 2019 and 2018 included stock-based compensation of $0.3&nbsp;million and $0.1&nbsp;million, respectively. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">45 </P>

</DIV></Center>


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<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Other Income (Expense), Net </I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Other income (expense), net was $0.4&nbsp;million of expense during the three months ended March&nbsp;31, 2019, compared to $1.3&nbsp;million of expense for
the three months ended March&nbsp;31, 2018. The decrease in other expense, net was primarily due to a $1.1 million decrease in the net expense generated from the change in the fair value of our preferred stock warrant and derivative liabilities in
the three months ended March&nbsp;31, 2019, partially offset by a $0.2&nbsp;million increase in interest expense. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Liquidity and Capital Resources
</B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Since our inception, we have not generated revenue from any sources, including from product sales, and have incurred significant operating losses and
negative cash flows from our operations. We have funded our operations to date primarily with proceeds from sales of common stock and warrants, sales of preferred stock, proceeds from the issuance of convertible debt and borrowings under loan and
security agreements. Through March&nbsp;31, 2019, we have received net proceeds of $73.7&nbsp;million from sales of our preferred stock, including proceeds from convertible debt, which converted into preferred stock, and gross proceeds of
$6.0&nbsp;million from borrowings under the SVB Loan Agreement. In 2018, we received gross proceeds of $10.0&nbsp;million from borrowings under the Hercules Loan Agreement and repaid all amounts due under the SVB Loan Agreement. In March 2019, we
completed the Merger with Arsanis and acquired $26.4&nbsp;million of cash, cash equivalents and restricted cash owned by Arsanis. On April 16, 2019, we raised $78.9&nbsp;million, after deducting underwriting discounts and estimated offering costs,
through the sale of 5,670,000 shares of common stock and, in lieu of common stock, <FONT STYLE="white-space:nowrap">pre-funded</FONT> warrants to purchase 2,130,000 shares of common stock, and accompanying Class&nbsp;A warrants to purchase 3,900,000
shares of our common stock at a price to the public of $11.00 per share and accompanying Class&nbsp;A warrants (or $10.999 per <FONT STYLE="white-space:nowrap">pre-funded</FONT> warrant and accompanying Class&nbsp;A warrants). </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Cash Flows </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The following table summarizes our
sources and uses of cash for each of the periods presented: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="76%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="79%"></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="4%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Three Months Ended</B><br><B>March&nbsp;31,</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2019</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>2018</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="6" ALIGN="center"><B>(in thousands)</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net cash used in operating activities</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(11,750</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(6,182</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net cash provided by investing activities</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">26,406</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net cash provided by (used in) financing activities</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">113</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(1,660</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Impact of foreign exchange on cash and restricted cash</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">(21</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD NOWRAP VALIGN="bottom" ALIGN="right">&#151;&nbsp;&nbsp;</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
<TR BGCOLOR="#cceeff" STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Net increase (decrease) in cash, cash equivalents and restricted cash</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">14,748</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">$</TD>
<TD VALIGN="bottom" ALIGN="right">(7,842</TD>
<TD NOWRAP VALIGN="bottom">)&nbsp;</TD></TR>
<TR STYLE="font-size:1px; ">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD VALIGN="bottom"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">&nbsp;</P></TD>
<TD>&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Operating Activities </I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">During the three months ended March&nbsp;31, 2019, net cash used in operating activities was $11.8&nbsp;million of cash, resulting from our net loss of
$10.9&nbsp;million, and net cash used in changes in our operating assets and liabilities of $1.5&nbsp;million, partially offset by noncash expenses of $0.6&nbsp;million. Net cash used in changes in our operating assets and liabilities for the three
months ended March&nbsp;31, 2019 consisted of a $0.6&nbsp;million increase in prepaid expenses and other current assets, a $2.0&nbsp;million decrease in accrued expenses, and a $0.2&nbsp;million decrease in lease liabilities, partially offset by a
$1.3&nbsp;million increase in accounts payable. The increase in prepaid expenses and other current assets was primarily due to increases in prepaid insurance amounts. The decrease in accrued expenses was primarily due to payments of employee bonuses
and payments to vendors related to professional fees and services. The increase in accounts payable was primarily due to the timing of vendor invoicing and payments. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">During the three months ended March&nbsp;31, 2018, operating activities used $6.2&nbsp;million of cash resulting from our net loss of $7.4&nbsp;million, and
net cash used in changes in our operating assets and liabilities of $0.2&nbsp;million, offset by <FONT STYLE="white-space:nowrap">non-cash</FONT> expenses of $1.3&nbsp;million. Net cash used in changes in our operating assets and liabilities for the
three months ended March&nbsp;31, 2018 consisted of a $0.6&nbsp;million decrease in accounts payable and a $0.2&nbsp;million decrease in lease liabilities, partially offset by a $0.2&nbsp;million decrease in prepaid expenses and other current assets
and a $0.3&nbsp;million increase in accrued expenses. The decrease in accounts payable was primarily due to timing of vendor invoicing and payments. The decrease in lease liabilities was primarily due to lease payments related to the Cambridge
office lease. The decrease in prepaid expenses and other current assets was primarily due to the expensing of prepaid amounts paid to CROs for preclinical development and clinical trial activities. The increase in accrued expenses was primarily due
to higher professional fees and increases in research and development activities and costs. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">46 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Investing Activities </I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">During the three months ended March&nbsp;31, 2019, net cash provided by investing activities consisted primarily of $26.4&nbsp;million of cash and restricted
cash acquired in connection with the Merger. There was no net cash provided by investing activities during the three months ended March&nbsp;31, 2018. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Financing Activities </I></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">During the three months ended
March&nbsp;31, 2019, net cash provided by financing activities was $0.1&nbsp;million, consisting primarily of the exercise of stock options. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">During the
three months ended March&nbsp;31, 2018, net cash used in financing activities was $1.7&nbsp;million, consisting primarily of $1.1&nbsp;million in the repurchase of Series Seed convertible preferred stock, principal repayments of $0.5&nbsp;million
under the SVB Loan Agreement, and $0.1&nbsp;million in payments of issuance costs related to convertible preferred stock. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Loan and Security
Agreements </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Loan and Security Agreement with Silicon Valley Bank </I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In October 2016, we entered into the SVB Loan Agreement, which provided for aggregate maximum borrowings of up to $10.0&nbsp;million, consisting of a term loan
of up to $6.0&nbsp;million, which we borrowed in June&nbsp;2017, and, subject to specified conditions, an additional term loan of up to $4.0&nbsp;million available for borrowing until December&nbsp;31, 2017. In October 2018, in connection with
entering into the Hercules Loan Agreement as described below, we terminated the SVB Loan Agreement and repaid all amounts due under the SVB Loan Agreement, including unpaid principal of $4.3&nbsp;million, a final payment of $0.3&nbsp;million, a
prepayment premium of $87&nbsp;thousand and accrued interest of $23&nbsp;thousand. We accounted for the repayment of amounts as an extinguishment of the SVB Loan Agreement and recognized a loss on extinguishment of debt of $0.2&nbsp;million within
other income (expense), net in the consolidated statement of operations and comprehensive loss. The loss on extinguishment of debt was calculated as the difference between the reacquisition price of the borrowings under the SVB Loan Agreement of
$4.7&nbsp;million and the carrying value of the debt under the SVB Loan Agreement of $4.5&nbsp;million. Our annual effective interest rate of the SVB Loan Agreement was approximately 11.8% the period from January&nbsp;1, 2018 through the date of
repayment of all borrowings under the SVB Loan Agreement. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>Loan and Security Agreement with Hercules Capital, Inc. </I></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In October 2018, we entered into the Hercules Loan Agreement, which provided for aggregate borrowings of up to $13.0&nbsp;million, consisting of (i)&nbsp;a
term loan of up to $8.0&nbsp;million, which was available upon entering into the agreement, (ii)&nbsp;subject to specified financing conditions, an additional term loan of up to $2.0&nbsp;million, available for borrowing from January&nbsp;1, 2019 to
March&nbsp;31, 2019, and (iii)&nbsp;subject to specified financing conditions and the receipt of the second tranche $2.0&nbsp;million term loan described above, an additional term loan of up to $3.0&nbsp;million, available for borrowing until
March&nbsp;31, 2019. In October 2018, we borrowed $8.0&nbsp;million under the Hercules Loan Agreement. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In December 2018, we entered into the First
Amendment to the Hercules Loan Agreement (the &#147;First Amendment&#148;), which amended the available borrowing dates of the second tranche from between January&nbsp;1, 2019 and March&nbsp;31, 2019 to between December&nbsp;11, 2018 and
December&nbsp;14, 2018 and amended the term loan maturity date to November&nbsp;1, 2021. In December 2018, we borrowed the additional $2.0&nbsp;million provided under the Hercules Loan Agreement, as amended by the First Amendment. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In March&nbsp;2019, the conditions necessary for borrowing the remaining $3.0&nbsp;million under the Hercules Loan Agreement were not met and the borrowing
capacity expired at that time. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Borrowings under the Hercules Loan Agreement bear interest at variable rates, with the first tranche bearing interest at a
variable rate equal to the greater of (i)&nbsp;9.5% or (ii)&nbsp;9.5% plus<I> The Wall Street Journal</I> prime rate minus 5.25%, the second tranche bearing interest at a variable rate, subject to completion of specified financing conditions, equal
to either (A)&nbsp;the greater of (i)&nbsp;9.5% or (ii)&nbsp;9.5% plus<I> The Wall Street Journal</I> prime rate minus 5.25% or (B)&nbsp;the greater of (i)&nbsp;8.75% or (ii)&nbsp;8.75% plus<I> The Wall Street Journal</I> prime rate minus 5.25%, and
the third tranche bearing interest at a variable rate equal to the greater of (i)&nbsp;8.75% or (ii)&nbsp;8.75% plus<I> The Wall Street Journal</I> prime rate minus 5.25%. In an event of default, as defined, and until such event is no longer
continuing, the interest rate applicable to borrowings under the Hercules Loan Agreement would be increased by 4.0%. As of March&nbsp;31, 2019 and December&nbsp;31, 2018, the interest rate applicable to borrowings under the Hercules Loan Agreement
was 9.75%. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Borrowings under the Hercules Loan Agreement are repayable in monthly interest-only payments through August 2019, or a later date upon
achievement of specified conditions, and in equal monthly payments of principal and accrued interest from September 2019 until the maturity date of the loan, which is either, (i)&nbsp;if the second tranche is not borrowed, November 2021 or,
(ii)&nbsp;if the second tranche is </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">47 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">
borrowed, May 2022. At our option, we may prepay all, but not less than all, of the outstanding borrowings, subject to a prepayment premium of up to 2.0% of the principal amount outstanding as of
the date of repayment. The Hercules Loan Agreement also provides for a final payment, payable upon maturity or the repayment in full of all obligations under the agreement, of up to $953. An aggregate final payment of $794 payable in connection with
the $8,000 term loan and the $2,000 term loan is being accreted to interest expense to increase the carrying value of the debt over the term of the loan using the effective interest method. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In addition, the Hercules Loan Agreement contains a redemption feature that, upon an event of default, provides Hercules the option to accelerate and demand
repayment of the debt, including a prepayment premium. We concluded that the redemption feature meets the definition of a derivative instrument as the repayment of the debt contains a substantial premium, resulting in the redemption feature not
being clearly and closely related to the host instrument. We recorded the issuance-date fair value of the derivative liability of $18 as a debt discount and as a derivative liability on our consolidated balance sheet. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Borrowings under the Hercules Loan Agreement are collateralized by substantially all of our personal property and other assets, including our intellectual
property until a specified financing condition is met. Under the Hercules Loan Agreement, we have agreed to affirmative and negative covenants to which we will remain subject until maturity or repayment in full. The covenants include maintaining a
minimum liquidity amount of the lesser of (i)&nbsp;125% of outstanding borrowings under the Hercules Loan Agreement and (ii)&nbsp;100% of our cash and cash equivalents in an account in which Hercules has a first priority security interest as well as
restrictions on our ability to incur additional indebtedness, pay dividends, encumber our intellectual property, or engage in certain fundamental business transactions, such as mergers or acquisitions of other businesses. Obligations under the
Hercules Loan Agreement are subject to acceleration upon occurrence of specified events of default, including payment default, insolvency and a material adverse change in our business, operations or financial or other condition. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In connection with entering into the Hercules Loan Agreement in October 2018, we issued to Hercules warrants for the purchase of 210,638&nbsp;shares of
Series&nbsp;B convertible preferred stock at an exercise price of $1.88 per share. These warrants were immediately exercisable and expire in October 2028. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In connection with entering into the First Amendment in December 2018, we agreed to issue to Hercules warrants for the purchase of a specified number of
shares of convertible preferred stock or, if issued following the Merger with Arsanis, a specified number of shares of common stock of the combined organization, at an aggregate exercise price of $99,000. The warrants were to be issued at the
earliest of (i)&nbsp;June&nbsp;30, 2019, (ii)&nbsp;the earlier to occur of (a)&nbsp;the date we prepay the outstanding borrowings or (b)&nbsp;the date the outstanding borrowings become due and payable, or (iii)&nbsp;on or before the fifth business
day following the closing of or the announcement of the termination of our merger with Arsanis. The number of shares of convertible preferred stock issuable upon exercise of these warrants was determined to be 52,659 shares, calculated by dividing
$99,000 by the $1.88 price per share paid by investors that purchased shares of Series&nbsp;B convertible preferred stock in September 2018. On March&nbsp;18, 2019, as a result of the closing of the Merger with Arsanis on March&nbsp;13, 2019, we
issued to Hercules warrants for the purchase of 5,000 shares of common stock of the combined organization at an exercise price of $19.80 per share, each of which reflected the share Exchange Ratio of <FONT STYLE="white-space:nowrap"><FONT
STYLE="white-space:nowrap">1-for-0.5702</FONT></FONT> applied in the Merger as well as the <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">6-for-1</FONT></FONT> reverse stock split effected by the combined organization on
March&nbsp;13, 2019. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On October&nbsp;19, 2018 and December&nbsp;11, 2018, the dates we entered into the Hercules Loan Agreement and the First Amendment,
respectively, we recorded the aggregate initial fair value of the warrants of $0.1&nbsp;million as a preferred stock warrant liability, with a corresponding amount recorded as a debt discount on our consolidated balance sheet. As of March&nbsp;13,
2019, the fair value of the warrants was $0.3&nbsp;million. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In connection with entering into the Hercules Loan Agreement and the First Amendment, we also
paid Hercules $92,000 of upfront fees, including facility, due diligence and legal fees associated with entering into the agreement, which were also recorded as a debt discount. The debt discount is reflected as a reduction of the carrying value of
long-term debt on our consolidated balance sheet and is being amortized to interest expense over the term of the loan using the effective interest method. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">We recognized aggregate interest expense under the Hercules Loan Agreement of $0.3&nbsp;million and $0 during three months ended March&nbsp;31, 2019 and 2018,
respectively, which included <FONT STYLE="white-space:nowrap">non-cash</FONT> interest expense of $0.1&nbsp;million related to the accretion of the debt discount and the final payment. As of March&nbsp;31, 2019, and December&nbsp;31, 2018, the
unamortized debt discount was $0.2&nbsp;million and $0.2&nbsp;million, respectively. The annual effective interest rate of the Hercules Loan Agreement as of March&nbsp;31, 2019 and December&nbsp;31, 2018 was approximately 14.2%, respectively. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>FFG Borrowings </B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Between September 2011 and March 2017,
Arsanis GmbH, a subsidiary of Arsanis, entered into a series of funding agreements with &Ouml;sterreichische Forschungsf&ouml;rderungsgesellschaft mbH, or FFG, that provided for loans and grants to fund qualifying research and development
expenditures of Arsanis GmbH on a <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">project-by-project</FONT></FONT> basis, as approved by FFG. As of March&nbsp;31, 2019, the outstanding principal amount under loans from FFG was
$9.5&nbsp;million, including $2.9&nbsp;million of current portion. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">48 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On February&nbsp;4, 2019, Arsanis GmbH, received letters from counsel to FFG alleging that we breached
reporting, performance and other obligations in connection with the grants and loans made by FFG to Arsanis GmbH between September 2011 and March 2017 to fund qualifying research and development expenditures. The letters demanded the immediate
repayment of all such subsidies. On March&nbsp;8, 2019, Arsanis announced that it had entered into a settlement agreement, or the Settlement Agreement, with FFG in respect of these allegations and demands for repayment. Pursuant to the terms of the
Settlement Agreement, in exchange for FFG&#146;s waiver of all claims against Arsanis and Arsanis GmbH except for its claims for repayment of the loans and regular interest, including its waiver of claims for repayment of grants and interest
exceeding regular interest, subject to compliance by us and Arsanis GmbH with the terms of the Settlement Agreement, Arsanis GmbH has agreed to repay the outstanding loan principal (plus regular interest accrued thereon) on an accelerated payment
schedule of three years instead of the original five years, with the final accelerated installment due and payable on June&nbsp;30, 2021. The Settlement Agreement also contains certain other restrictive covenants, including a requirement to
maintain, as of April&nbsp;30, 2019, a minimum cash balance equal to 70% of the then-outstanding principal amount of the loans at Arsanis GmbH in an account held with an Austrian bank, until all of the loans have been repaid and subject to other
terms specified in the Settlement Agreement. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Amounts due under the FFG loans bear interest at varying fixed rates ranging from 0.75% to 2.0% per annum.
Interest is payable semi-annually in arrears, with all accrued interest and principal due upon maturity. After giving effect to the Settlement Agreement, the FFG loans mature at varying dates between March 2019 and June 2021. The FFG loans are not
secured by any of our assets. We may be required to return all or a portion of the FFG loans and/or grants if we do not comply with the terms of the related FFG funding agreements and related guidelines, including specified requirements as to
continued operations with respect to certain locations and funded projects, or if we fail to comply with the terms of the Settlement Agreement. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Funding Requirements </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">We expect our expenses to
increase substantially in connection with our ongoing activities, particularly as we advance the preclinical activities and clinical trials of our product candidates in development. In addition, following the closing of the Merger, we expect to
incur additional costs associated with operating as a public company. The timing and amount of our operating expenditures will depend largely on: </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the scope, number, initiation, progress, timing, costs, design, duration, any potential delays, and results of
clinical trials and nonclinical studies for our current or future product candidates, particularly our Phase 3 pivotal clinical trial of mavorixafor for the treatment of patients with WHIM syndrome, our Phase 1 clinical trial of mavorixafor in SCN
and our Phase 1/2 clinical trial of mavorixafor in WM, [<I>and our Phase 1/2 for the treatment of ccRCC</I>] </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the clinical development plans we establish for these product candidates; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
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<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the number and characteristics of product candidates and programs that we develop or may <FONT
STYLE="white-space:nowrap">in-license;</FONT> </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the outcome, timing and cost of regulatory reviews, approvals or other actions to meet regulatory requirements
established by the FDA and comparable foreign regulatory authorities, including the potential for the FDA or comparable foreign regulatory authorities to require that we perform more studies for our product candidates than those that we currently
expect; </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
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<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">our ability to obtain marketing approval for our product candidates; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the cost of filing, prosecuting, defending and enforcing our patent claims and other intellectual property rights
covering our product candidates, including any such patent claims and intellectual property rights that we have licensed from Genzyme pursuant to the terms of our license agreement with Genzyme; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">our ability to maintain, expand and defend the scope of our intellectual property portfolio, including the cost
of defending intellectual property disputes, including patent infringement actions brought by third parties against us or our product candidates; </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the cost and timing of completion of commercial-scale outsourced manufacturing activities with respect to our
product candidates; </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">our ability to establish and maintain licensing, collaboration or similar arrangements on favorable terms and
whether and to what extent we retain development or commercialization responsibilities under any new licensing, collaboration or similar arrangement; </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the cost of establishing sales, marketing and distribution capabilities for any product candidates for which we
may receive regulatory approval in regions where we choose to commercialize our products on our own; </P></TD></TR></TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">49 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>

<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
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<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the success of any other business, product or technology that we acquire or in which we invest;
</P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
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<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the costs of acquiring, licensing or investing in businesses, product candidates and technologies;
</P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
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<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">our need and ability to hire additional management and scientific and medical personnel; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
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<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the costs to operate as a public company in the United States, including the need to implement additional
financial and reporting systems and other internal systems and infrastructure for our business; </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
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<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">market acceptance of our product candidates, to the extent any are approved for commercial sale; and
</P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">the effect of competing technological and market developments. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">We expect that our existing cash and cash equivalents, including $78.9&nbsp;million of net proceeds from our April 2019 public offering and the cash acquired
from Arsanis will be sufficient to fund our operating expenses, capital expenditure requirements and debt service payments for at least the next 12 months. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Until such time, if ever, as we can generate substantial product revenue, we expect to finance our cash needs through a combination of equity offerings, debt
financings, collaborations, strategic alliances, and marketing, distribution or licensing arrangements with third parties. In January 2019, Arsanis filed a universal shelf registration statement on Form <FONT STYLE="white-space:nowrap">S-3</FONT>
with the SEC, which was declared effective in February 2019, and pursuant to which Arsanis registered for sale up to $150&nbsp;million of any combination of our common stock, preferred stock, debt securities, warrants and/or units from time to time
and at prices and on terms that we may determine. Subsequently, in April 2019, we sold 5,670,000 shares of common stock and, in lieu of common stock, <FONT STYLE="white-space:nowrap">pre-funded</FONT> warrants to purchase 2,130,000 shares of common
stock, and accompanying Class&nbsp;A warrants to purchase 3,900,000 shares of our common stock at a price to the public of $11.00 per share and accompanying Class&nbsp;A warrants (or $10.999 per <FONT STYLE="white-space:nowrap">pre-funded</FONT>
warrant and accompanying Class&nbsp;A warrants) under this shelf registration statement for gross proceeds of approximately $85.8&nbsp;million. As of May&nbsp;1, 2019, approximately $64.2&nbsp;million of securities remain available for issuance
under the shelf registration statement. To the extent that we raise additional capital through the sale of equity or convertible debt securities, the ownership interest of our stockholders may be materially diluted, and the terms of such securities
could include liquidation or other preferences that adversely affect the rights of our stockholders. Debt financing and preferred equity financing, if available, may involve agreements that include restrictive covenants that limit our ability to
take specified actions, such as incurring additional debt, making capital expenditures or declaring dividends. If we raise funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we
may have to relinquish valuable rights to our technologies, future revenue streams, research programs or product candidates or grant licenses on terms that may not be favorable to us. If we are unable to raise additional funds through equity or debt
financings or other arrangements when needed, we may be required to delay, reduce or eliminate our product development or future commercialization efforts, or grant rights to develop and market product candidates that we would otherwise prefer to
develop and market ourselves. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Critical Accounting Policies and Significant Judgments and Estimates </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Our consolidated financial statements are prepared in accordance with generally accepted accounting principles in the United States. The preparation of our
consolidated financial statements and related disclosures requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, costs and expenses, and the disclosure of contingent assets and liabilities in our
financial statements. We base our estimates on historical experience, known trends and events and various other factors that we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the
carrying values of assets and liabilities that are not readily apparent from other sources. We evaluate our estimates and assumptions on an ongoing basis. Our actual results may differ from these estimates under different assumptions or conditions.
</P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">While our significant accounting policies are described in more detail in Note&nbsp;2 to our consolidated financial statements included elsewhere in this
quarterly report, we believe that the following accounting policies are those most critical to the judgments and estimates used in the preparation of our consolidated financial statements. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">50 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Accrued Research and Development Expenses </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As part of the process of preparing our consolidated financial statements, we are required to estimate our accrued research and development expenses. This
process involves reviewing open contracts and purchase orders, communicating with our applicable personnel to identify services that have been performed on our behalf and estimating the level of service performed and the associated cost incurred for
the service when we have not yet been invoiced or otherwise notified of actual costs. The majority of our service providers invoice us in arrears for services performed, on a <FONT STYLE="white-space:nowrap">pre-determined</FONT> schedule or when
contractual milestones are met; however, some require advance payments. We make estimates of our accrued expenses as of each balance sheet date in the consolidated financial statements based on facts and circumstances known to them at that time. We
periodically confirm the accuracy of these estimates with the service providers and makes adjustments, if necessary. Examples of estimated accrued research and development expenses include fees paid to: </P>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">vendors in connection with preclinical development activities; </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">CROs and investigative sites in connection with preclinical studies and clinical trials; and
</P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="5%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P ALIGN="left" STYLE=" margin-top:0pt ; margin-bottom:0pt; font-family:Times New Roman; font-size:10pt">CMOs in connection with the production of preclinical and clinical trial materials. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">We base the expense recorded related to external research and development on our estimates of the services received and efforts expended pursuant to quotes
and contracts with multiple CMOs and CROs that supply, conduct and manage preclinical studies and clinical trials on our behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in
uneven payment flows. There may be instances in which payments made to our vendors will exceed the level of services provided and result in a prepayment of the expense. Payments under some of these contracts depend on factors such as the successful
enrollment of patients and the completion of clinical trial milestones. In accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the
performance of services or the level of effort varies from the estimate, we adjust the accrual or the amount of prepaid expenses accordingly. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Although we
do not expect our estimates to be materially different from amounts actually incurred, our understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in
reporting amounts that are too high or too low in any particular period. To date, there have not been any material adjustments to our prior estimates of accrued research and development expenses. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Stock-Based Compensation </I></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Historically, we
measured all stock-based awards granted to employees and directors based on the fair value on the date of the grant and recognize compensation expense for those awards, net of estimated forfeitures, over the requisite service period, which is
generally the vesting period of the respective award. We issue stock-based awards with only service-based vesting conditions and record the expense for these awards using the straight-line method. We have not issued any stock-based awards with
performance-based vesting conditions. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">For stock-based awards granted to <FONT STYLE="white-space:nowrap">non-employee</FONT> consultants, compensation
expense is recognized over the period during which services are rendered by such <FONT STYLE="white-space:nowrap">non-employee</FONT> consultants until completed. At the end of each financial reporting period prior to completion of the service, the
fair value of these awards is remeasured using the then-current fair value of our common stock and updated assumption inputs in the Black-Scholes option-pricing model. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model, which uses as inputs the fair value
of our common stock and assumptions we make for the volatility of our common stock, the expected term of the stock options, the risk-free interest rate for a period that approximates the expected term of our stock options and their expected dividend
yield. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Prior to the closing of the Merger and the listing of our common stock on the Nasdaq Capital Market, our board of directors historically
determined, as of the date of each option grant, with input from our management, the assistance of a third-party valuation specialist and the guidance outlined in the American Institute of Certified Public Accountants&#146; Accounting and Valuation
Guide, Valuation of Privately-Held-Company Equity Securities Issued as Compensation, the estimated fair value of our common stock on the date of grant based on a number of objectives and subjective factors </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Since&nbsp;the Merger and the listing of our common stock on the Nasdaq Capital Market, we have relied on the market price of our common stock to determine
the fair value on the date of grant for purposes of determining our stock-based compensation expense. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">51 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The assumptions underlying these valuations represent the best estimates of our management, which involve
inherent uncertainties and the application of our judgment. As a result, if factors or expected outcomes change and we use significantly different assumptions or estimates, the resulting share-based compensation expense could be materially
different. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Valuation of Preferred Stock Warrant Liability </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In connection with our preferred stock financings in 2015, 2017, and 2018, and entering into the SVB Loan Agreement in 2016, we issued warrants to purchase
shares of our preferred stock. We classify these warrants as liabilities on our consolidated balance sheets because these warrants are freestanding financial instruments that may require us to transfer assets upon exercise. The warrant liability was
initially recorded at fair value upon the date of issuance of each warrant and is subsequently remeasured to fair value at each reporting date. Changes in the fair value of the warrant liability are recognized as a component of other income
(expense), net in our consolidated statements of operations and comprehensive loss. Upon the closing of the Merger on March&nbsp;13, 2019, all of our outstanding preferred stock warrants become exercisable for Arsanis common stock; accordingly, the
liability as of March&nbsp;13, 2019 for these warrants was remeasured to fair value and reclassified to additional <FONT STYLE="white-space:nowrap">paid-in</FONT> capital. As a result, following the closing of the Merger, we no longer recognize
changes in the fair value of the warrant liability as other income (expense), net in our consolidated statement of operations and comprehensive loss. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">To
value the preferred stock warrants, we used various valuation methods, including the Monte Carlo method, the option-pricing method and the hybrid method, all of which incorporate assumptions and estimates, We assess these assumptions and estimates
on a quarterly basis as additional information impacting the assumptions is obtained. Estimates and assumptions impacting the fair value measurement include the fair value per share of the underlying shares of our Series A and Series B preferred
stock, risk-free interest rate, expected dividend yield, expected volatility of the price of the underlying preferred stock, and the remaining contractual term of the warrants (except for the warrants that would be automatically exercised upon an
initial public offering, in which case the remaining estimated term to automatic exercise was used). The most significant assumption in the Monte Carlo method, the option-pricing method and the hybrid method impacting the fair value of the preferred
stock warrants is the fair value of our preferred stock as of each remeasurement date. We determine the fair value per share of the underlying preferred stock by taking into consideration the most recent sales of our preferred stock, results
obtained from third-party valuations and additional factors that are deemed relevant. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Upon the closing of the Merger, pursuant to the Merger Agreement,
all of our outstanding preferred stock warrants have become exercisable for Arsanis common stock; accordingly, the fair value of the warrant liability for these warrants at that time will be reclassified to additional
<FONT STYLE="white-space:nowrap">paid-in</FONT> capital. As a result, following the closing of the Merger, we will no longer recognize changes in the fair value of the warrant liability as other income (expense), net in our consolidated statement of
operations and comprehensive loss. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Valuation of Derivative Liability </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Our license agreement with Genzyme contains a contingent payment obligation that requires that we make a cash payment to Genzyme upon a change of control
event. The contingent payment obligation meets the definition of a derivative instrument as the contingent payment obligation is not clearly and closely related to our host instrument and is a cash-settled liability. Accordingly, we classify this
derivative as a liability on our consolidated balance sheet. The derivative liability was initially recorded at fair value on the date of entering into the license agreement and is subsequently remeasured to fair value at each reporting date.
Changes in the fair value of the derivative liability are recognized as a component of other income (expense), net in our consolidated statement of operations and comprehensive loss. The Merger qualifies as a change of control event, as defined in
the license agreement, but results in no payment being due to Genzyme under the license agreement. On March&nbsp;13, 2019, the closing date of the Merger with Arsanis, this derivative liability was remeasured to fair value, which was $0, and
subsequent changes in fair value will no longer be recognized in the consolidated statements of operations and comprehensive loss because the contingent payment obligation expired at that time. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The fair value of the derivative liability was estimated at each reporting date based, in part, on the results of third-party valuations, which were prepared
using the option-pricing method or the hybrid method, each of which considered as inputs the type, timing and probability of the occurrence of a change of control event, the potential amount of the payment under potential exit scenarios, the fair
value per share of the underlying common stock and the risk-adjusted discount rate. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">52 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><I>Valuation of Preferred Stock Repurchase Liability </I></B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">In October 2017, we entered into a stock repurchase agreement with a holder of Series Seed preferred stock for the repurchase of shares of Series Seed
preferred stock. We classified this repurchase agreement as a liability on our consolidated balance sheet as the repurchase agreement was a freestanding financial instrument that required us to transfer assets upon settlement. The preferred stock
repurchase liability was initially recorded at fair value on the date of entering into the repurchase agreement and was subsequently remeasured to fair value at each reporting date and upon the settlement date until the settlement of the repurchase
agreement, which occurred in January 2018. Changes in the fair value of the preferred stock repurchase liability were recognized as a component of other income (expense), net in our consolidated statement of operations and comprehensive loss. The
fair value of the preferred stock repurchase liability was estimated by multiplying (i)&nbsp;the 598,975 shares of Series Seed preferred stock that we agreed to repurchase by (ii)&nbsp;the difference between the agreed repurchase price of $1.88 per
share and the fair value per share of the Series Seed preferred stock, which result approximated the fair value of the preferred stock repurchase liability given the short duration of the contract. We determined the fair value per share of the
Series Seed preferred stock by taking into consideration the most recent sales of our preferred stock, results obtained from third-party valuations and additional factors that were deemed relevant. In January 2018, the Series Seed preferred stock
repurchase agreement was settled through our repurchase of the shares. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Emerging Growth Company Status </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">We are an &#147;emerging growth company,&#148; or EGC, as defined in the Jumpstart Our Business Startups Act of 2012, or the JOBS Act, We will remain an EGC
until the earlier of (1)&nbsp;the last day of the fiscal year following the fifth anniversary of the completion of Arsanis&#146; initial public offering (December 31, 2022), (2) the last day of the fiscal year in which we have total annual gross
revenue of at least $1.07&nbsp;billion, (3)&nbsp;the last day of the fiscal year in which we are deemed to be a &#147;large accelerated filer&#148; as defined in <FONT STYLE="white-space:nowrap">Rule&nbsp;12b-2</FONT> under the Exchange Act, which
would occur if the market value of our common stock held by <FONT STYLE="white-space:nowrap">non-affiliates</FONT> exceeded $700.0&nbsp;million as of the last business day of the second fiscal quarter of such fiscal year or (4)&nbsp;the date on
which we have issued more than $1.0&nbsp;billion in <FONT STYLE="white-space:nowrap">non-convertible</FONT> debt securities during the prior three-year period. The JOBS Act permit an EGC to take advantage of an extended transition period to comply
with new or revised accounting standards applicable to public companies until those standards would otherwise apply to private companies. We have irrevocably elected to &#147;opt out&#148; of this provision and, as a result, we will comply with new
or revised accounting standards when they are required to be adopted by public companies that are not emerging growth companies. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><FONT
STYLE="white-space:nowrap">Off-Balance</FONT> Sheet Arrangements </B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">We did not have during the periods presented, and we do not currently have, any <FONT
STYLE="white-space:nowrap">off-balance</FONT> sheet arrangements, as defined in the rules and regulations of the SEC. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Recently Issued Accounting
Pronouncements </B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">A description of recently issued accounting pronouncements that may potentially impact our financial position and results of operations
is disclosed in Note&nbsp;2 to our consolidated financial statements included elsewhere in this quarterly report on Form <FONT STYLE="white-space:nowrap">10-Q.</FONT> </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="8%" VALIGN="top" ALIGN="left"><B><A NAME="tx726255_11"></A>Item&nbsp;3.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Not required for smaller reporting companies. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="8%" VALIGN="top" ALIGN="left"><B><A NAME="tx726255_12"></A>Item&nbsp;4.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>CONTROLS AND PROCEDURES </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Evaluation of Disclosure Controls and Procedures </B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Our
principal executive officer and principal financial officer, after evaluating the effectiveness of our disclosure controls and procedures (as defined in Exchange Act Rules <FONT STYLE="white-space:nowrap">13a-15(e)</FONT> and <FONT
STYLE="white-space:nowrap">15d-15(e))</FONT> as of the end of the period covered by this <FONT STYLE="white-space:nowrap">Form&nbsp;10-Q,</FONT> have concluded that, based on such evaluation, our disclosure controls and procedures were effective to
ensure that information required to be disclosed by us in the reports that we file or submit under the Exchange Act is recorded, processed, summarized and reported within the time periods specified in the SEC&#146;s rules and forms, and is
accumulated and communicated to our management, including our principal executive and principal financial officers, or persons performing similar functions, as appropriate, to allow timely decisions regarding required disclosure. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Changes in Internal Controls </B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">During the three months
ended March&nbsp;31, 2019, we implemented certain internal controls as a result of our adoption of the new lease standard on January&nbsp;1, 2019 as well as internal controls related to the business combination. There were no other changes in our
internal control over financial reporting (as defined in Rules&nbsp;13a&#150;15(f) and 15d&#150;15(f) under the Exchange Act) that occurred during the three months ended March&nbsp;31, 2019 that have materially affected, or are reasonably likely to
materially affect, our internal control over financial reporting. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">53 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><A NAME="tx726255_13"></A>PART II: OTHER INFORMATION </B></P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
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<TD WIDTH="8%" VALIGN="top" ALIGN="left"><B><A NAME="tx726255_14"></A>Item&nbsp;1.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>LEGAL PROCEEDINGS </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">We are not currently a party to any material legal proceedings. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="8%" VALIGN="top" ALIGN="left"><B><A NAME="tx726255_15"></A>Item&nbsp;1A.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>RISK FACTORS </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">There have been no material changes to the risk factors described in our Annual Report on Form <FONT STYLE="white-space:nowrap">10-K</FONT> for the year ended
December&nbsp;31, 2018 filed with the SEC on March&nbsp;11, 2019, as updated by the risk factors described in our Current Report on Form <FONT STYLE="white-space:nowrap">8-K,</FONT> filed with the SEC on April&nbsp;11, 2019.<B> </B> </P>
<P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="8%" VALIGN="top" ALIGN="left"><B><A NAME="tx726255_16"></A>Item&nbsp;2.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>UNREGISTERED SALES OF EQUITY SECURITIES AND USE OF PROCEEDS </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Unregistered Sales of Equity Securities </B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Pursuant to our
loan and security agreement, dated as of October&nbsp;19, 2018, with Hercules Capital, Inc., or Hercules, we issued a warrant to purchase 5,000 shares of our common stock to Hercules having an exercise price of $19.80 per share, subject to
adjustment as a result of any stock splits, stock dividends or similar transactions. These warrants were issued in reliance on the exemption from registration provided under Section&nbsp;4(a)(2) of the Securities Act. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Issuer Purchases of Equity Securities </B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">We did not
repurchase any of our equity securities during the quarter ended March&nbsp;31, 2019. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Use of Proceeds from Registered Securities </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On November&nbsp;20, 2017, Arsanis closed its initial public offering, in which Arsanis issued and sold 666,667&nbsp;shares of common stock at a public
offering price of $60.00&nbsp;per share, and issued an additional 100,000&nbsp;shares of common stock at a price of $60.00&nbsp;per share pursuant to the exercise of the underwriters&#146; over-allotment option. The aggregate gross proceeds to
Arsanis from the initial public offering, inclusive of the over-allotment exercise, were $46.0&nbsp;million. All of the shares of common stock issued and sold in the initial public offering were registered under the Securities Act of 1933, as
amended, pursuant to a registration statement on Form&nbsp;S-1 (Registration No.&nbsp;333-221050), which was declared effective by the SEC on November&nbsp;15, 2017. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The aggregate net proceeds to Arsanis from the public offering, inclusive of the over-allotment exercise, were approximately $39.5&nbsp;million, after
deducting underwriting discounts and commissions and offering expenses payable by Arsanis of approximately $6.5&nbsp;million. No offering expenses were paid directly or indirectly to any of Arsanis&#146;s directors or officers (or their associates)
or persons owning 10% or more of any class of our equity securities or to any other affiliates. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">As of March&nbsp;31, 2019, we have used all of the net
proceeds from the initial public offering to advance product candidates through clinical trial programs and for working capital and general corporate purposes. There have been no material changes in the planned use of proceeds from the initial
public offering as described in Arsanis&#146;s final prospectus filed with the SEC on November&nbsp;17, 2017 pursuant to Rule&nbsp;424(b). </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="8%" VALIGN="top" ALIGN="left"><B><A NAME="tx726255_17"></A>Item&nbsp;3.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>DEFAULTS UPON SENIOR SECURITIES </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Not applicable. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="8%" VALIGN="top" ALIGN="left"><B><A NAME="tx726255_18"></A>Item&nbsp;4.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>MINE SAFETY DISCLOSURES </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Not applicable. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="8%" VALIGN="top" ALIGN="left"><B><A NAME="tx726255_19"></A>Item&nbsp;5.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>OTHER INFORMATION </B></P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Not applicable. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">54 </P>

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<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>

<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="8%" VALIGN="top" ALIGN="left"><B><A NAME="tx726255_20"></A>Item&nbsp;6.</B></TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><B>EXHIBITS </B></P></TD></TR></TABLE> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


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<TD></TD></TR>
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<TD VALIGN="bottom" NOWRAP ALIGN="center"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>Exhibit</B></P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1.00pt solid #000000; display:table-cell; font-size:8pt; font-family:Times New Roman; " ALIGN="center"><B>&nbsp;&nbsp;&nbsp;&nbsp;No.&nbsp;&nbsp;&nbsp;&nbsp;</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-bottom:1.00pt solid #000000; display:table-cell; font-size:8pt; font-family:Times New Roman; " ALIGN="center"><B>Exhibit Description</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Filed</B><br><B>&nbsp;&nbsp;Herewith&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Incorporated&nbsp;by</B><br><B>Reference&nbsp;herein</B><br><B>from Form or</B><br><B>Schedule</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Filing&nbsp;Date</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>SEC</B><br><B>File/Reg.</B><br><B>Number</B></TD></TR>


<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;&nbsp;&nbsp;2.1</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519069279/d721507dex21.htm">Second Amendment to Agreement and Plan of Merger, dated March&nbsp;
8, 2019, by and among the Company, Artemis AC Corp. and X4 Therapeutics, Inc. (formerly X4&nbsp;Pharmaceutical, Inc.). </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;2.1)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">3/8/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;&nbsp;&nbsp;3.1</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312517348213/d495338dex31.htm">Restated Certificate of Incorporation of the Company. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;3.1)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">11/20/2017</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;&nbsp;&nbsp;3.2</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex31.htm">Certificate of Amendment (Reverse Stock Split) to the Restated Certificate of Incorporation of the Company. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;3.1)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">3/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;&nbsp;&nbsp;3.3</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex32.htm">Certificate of Amendment (Name Change) to the Restated Certificate of Incorporation of the Company. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;3.2)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">3/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;&nbsp;&nbsp;4.1</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex41.htm">Form of Common Stock Certificate. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;4.1)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">3/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
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<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;&nbsp;&nbsp;4.2</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex42.htm">Form of Warrant to Purchase Series A Preferred Stock of X4&nbsp;
Therapeutics, Inc. (formerly X4 Pharmaceuticals, Inc.) issued to Silicon Valley Bank and Life Science Loans, LLC. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;4.2)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">3/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;&nbsp;&nbsp;4.3</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex43.htm">Form of Warrant to Purchase Series A Preferred Stock of X4&nbsp;
Therapeutics, Inc. (formerly X4 Pharmaceuticals, Inc.) issued to Maxim Partners LLC. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;4.3)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">3/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;&nbsp;&nbsp;4.4</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex44.htm">Form of Warrant to Purchase Series B Preferred Stock of X4 Therapeutics, Inc. (formerly X4 Pharmaceuticals, Inc.). </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;4.4)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">3/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;&nbsp;&nbsp;4.5</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="d726255dex45.htm">Amended and Restated Warrant Agreement, dated as of March&nbsp;29, 2019, by and between the Company and Hercules Capital, Inc. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">X</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;&nbsp;&nbsp;4.6</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="d726255dex46.htm">Warrant Agreement, dated as of March&nbsp;18, 2019, by and between the Company and Hercules Capital, Inc. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">X</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.1.1*</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex1011.htm">2015 Employee, Director and Consultant Equity Incentive Plan, as amended. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;10.1.1)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">3/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.1.2*</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519095792/d711669dex1012.htm">Form of Stock Option Agreement under the 2015 Employee, Director and Consultant Equity Incentive Plan, as amended. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K/A</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;10.1.2)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">4/3/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.2*</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex102.htm">Director Compensation Policy. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;10.2)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">3/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.3*</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex103.htm">Amended and Restated Executive Employment Agreement, dated as of March&nbsp;13, 2019, by and between the Company and Paula Ragan, Ph.D.
</A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;10.3)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">3/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.4*</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex104.htm">Amended and Restated Executive Employment Agreement, dated as of March&nbsp;13, 2019, by and between the Company and Adam S. Mostafa.
</A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;10.4)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">3/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.5&plusmn;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex105.htm">License Agreement, dated as of July&nbsp;
10, 2014, by and between X4 Therapeutics, Inc. (formerly X4 Pharmaceuticals, LLC) and Genzyme Corp., a Sanofi company. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K/A</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;10.5)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">5/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.6&plusmn;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex106.htm">Amendment No.&nbsp;1 to License Agreement, dated as of October&nbsp;23, 2014, by and between X4 Therapeutics, Inc. (formerly X4&nbsp;
Pharmaceuticals, Inc.) and Genzyme Corporation, a Sanofi company. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K/A</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;10.6)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">5/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR></TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">55 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">
<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD></TD>
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<TD WIDTH="58%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
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<TD></TD>
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<TD></TD>
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<TD></TD></TR>

<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom" NOWRAP ALIGN="center"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>Exhibit</B></P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1.00pt solid #000000; display:table-cell; font-size:8pt; font-family:Times New Roman; " ALIGN="center"><B>&nbsp;&nbsp;&nbsp;&nbsp;No.&nbsp;&nbsp;&nbsp;&nbsp;</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-bottom:1.00pt solid #000000; display:table-cell; font-size:8pt; font-family:Times New Roman; " ALIGN="center"><B>Exhibit Description</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Filed</B><br><B>&nbsp;&nbsp;Herewith&nbsp;&nbsp;</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Incorporated&nbsp;by</B><br><B>Reference&nbsp;herein</B><br><B>from Form or</B><br><B>Schedule</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>Filing&nbsp;Date</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center" STYLE="border-bottom:1.00pt solid #000000"><B>SEC</B><br><B>File/Reg.</B><br><B>Number</B></TD></TR>


<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.7&plusmn;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex107.htm">License Agreement, dated as of December&nbsp;
13, 2016, by and between X4 Therapeutics, Inc. (formerly X4 Pharmaceuticals, Inc.) and Georgetown University. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K/A</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit 10.7)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">5/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.8&plusmn;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex108.htm">Exclusive License Agreement, dated as of December&nbsp;23, 2016, by and between X4&nbsp;
Therapeutics, Inc. (formerly X4 Pharmaceuticals, Inc.) and Beth Israel Deaconess Medical Center. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K/A</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;10.8)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">5/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.9</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex109.htm">Loan and Security Agreement, dated as of October&nbsp;19, 2018, by and between X4&nbsp;
Therapeutics, Inc. (formerly X4 Pharmaceuticals, Inc.) and Hercules Capital, Inc. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;10.9)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">3/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.10</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex1010.htm">Amendment No.&nbsp;1 to Loan and Security Agreement, dated as of December&nbsp;
11, 2018, by and between X4 Therapeutics, Inc. (formerly X4&nbsp;Pharmaceuticals, Inc.) and Hercules Capital, Inc. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;10.10)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">3/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.11</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex10111.htm">Lease, dated as of January&nbsp;
20, 2017, by and between X4 Therapeutics, Inc. (formerly X4 Pharmaceuticals, Inc.) and Brickman 955 Massachusetts LLC. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;10.11)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">3/13/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.12</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519103832/d733375dex101.htm">Settlement Agreement, dated as of March&nbsp;
8, 2019, by and among X4 Pharmaceuticals, Inc. (formerly Arsanis, Inc.), Artemis AC Corp., X4 Therapeutics, Inc. (formerly X4 Pharmaceuticals, Inc.), Arsanis Biosciences GmbH and &Ouml;sterreichische Forschungsf&ouml;rderungsgesellschaft GmbH.
</A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;10.1)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">4/11/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>10.13</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="http://www.sec.gov/Archives/edgar/data/1501697/000119312519061101/d704032dex101.htm">Lease Termination Agreement, dated February&nbsp;26, 2019, by and between Arsanis Biosciences GmbH and W&uuml;stenrot Marxbox GmbH&nbsp;
&amp; Co. OG (as <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">successor-in-interest</FONT></FONT> to Marxbox Bauprojekt GmbH&nbsp;&amp; Co. OG), as amended (English translation). </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">8-K</FONT><BR> <P STYLE="margin-bottom:1pt; margin-top:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">(Exhibit&nbsp;10.1)</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">3/1/2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center"><FONT STYLE="white-space:nowrap">001-38295</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.14*</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="d726255dex1014.htm">Form of Restricted Stock Agreement under the 2017 Equity Incentive Plan. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">X</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.15*</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="d726255dex1015.htm">Form of Nonstatutory Stock Option Agreement (Director Grants) under the 2017 Equity Incentive Plan. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">X</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.16*</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="d726255dex1016.htm">Form of Nonstatutory Stock Option Agreement under the 2017 Equity Incentive Plan. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">X</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;10.17*</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="d726255dex1017.htm">Form of Incentive Stock Option Agreement under the 2017 Equity Incentive Plan. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">X</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;31.1</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="d726255dex311.htm">Certification of the Registrant&#146;s Principal Executive Officer pursuant to Section<U></U>&nbsp;302 of the Sarbanes-Oxley Act of 2002. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">X</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;31.2</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="d726255dex312.htm">Certification of the Registrant&#146;s Principal Financial Officer pursuant to Section<U></U>&nbsp;302 of the Sarbanes-Oxley Act of 2002. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">X</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;32.1</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top"><A HREF="d726255dex321.htm">Certification of Principal Executive Officer and Principal Financial Officer pursuant to Section<U></U>&nbsp;906 of the Sarbanes-Oxley Act of 2002. </A></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">X</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>101</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">The following materials from the Registrant&#146;s Quarterly Report on <FONT STYLE="white-space:nowrap">Form&nbsp;10-Q</FONT> for the quarter ended March&nbsp;31, 2019, formatted in XBRL (eXtensible Business Reporting Language): (i)
Condensed Consolidated Balance Sheets (unaudited) as of March&nbsp;31, 2019 and December&nbsp;31, 2018, (ii)&nbsp;Condensed Consolidated Statements of Operations (unaudited) for the Three Months Ended March&nbsp;31, 2019 and 2018,
(iii)&nbsp;Condensed Consolidated Statements of Comprehensive Loss (unaudited) for the Three Months Ended March&nbsp;31, 2019 and 2018, (iv)&nbsp;Condensed Consolidated Statements of Convertible Preferred Stock, Redeemable Common Stock and
Stockholders&#146; Equity (Deficit) (unaudited) for the Three Months Ended March&nbsp;31, 2019 and 2018, and (v)&nbsp;Condensed Consolidated Statements of Cash Flows (unaudited) for the Three Months Ended March&nbsp;31, 2019 and 2018.</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" NOWRAP ALIGN="center">X</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD></TR>
</TABLE> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">*</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">Management contract or compensatory plans or arrangements. </P></TD></TR></TABLE>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">&plusmn;</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">Certain confidential portions of this Exhibit were omitted by means of marking such portions with brackets
(&#147;[***]&#148;) because the identified confidential portions (i)&nbsp;are not material and (ii)&nbsp;would be competitively harmful if publicly disclosed. </P></TD></TR></TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">56 </P>

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<h5 align="left"><a href="#toc">Table of Contents</a></h5>


<Center><DIV STYLE="width:8.5in" align="left">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>X4 PHARMACEUTICALS, INC. </B></P>
<p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><A NAME="tx726255_21"></A>SIGNATURES </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned
thereunto duly authorized. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt">


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<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3"><B>X4 PHARMACEUTICALS, INC.</B></TD></TR>
<TR STYLE="font-size:1pt">
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<TD VALIGN="top">Date: May&nbsp;15, 2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">/s/ Paula Ragan, Ph.D.</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Paula Ragan, Ph.D.</P> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">President, Chief Executive
Officer and Secretary</P></TD></TR>
</TABLE> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt">


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<TD VALIGN="top">Date: May&nbsp;15, 2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">/s/ Adam S. Mostafa</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
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<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Adam S. Mostafa</P> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">Chief Financial Officer and
Treasurer</P></TD></TR>
</TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">57 </P>

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<DOCUMENT>
<TYPE>EX-4.5
<SEQUENCE>2
<FILENAME>d726255dex45.htm
<DESCRIPTION>EX-4.5
<TEXT>
<HTML><HEAD>
<TITLE>EX-4.5</TITLE>
</HEAD>
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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>Exhibit 4.5 </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">THIS WARRANT, AND THE SECURITIES ISSUABLE UPON THE EXERCISE OF THIS WARRANT, HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE
&#147;ACT&#148;), OR ANY STATE SECURITIES LAWS. THEY MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED, OR HYPOTHECATED IN THE ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT RELATED THERETO OR AN OPINION OF COUNSEL (WHICH MAY BE COMPANY COUNSEL) REASONABLY
SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED UNDER THE ACT, OR ANY APPLICABLE STATE SECURITIES LAWS. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">AMENDED AND
RESTATED </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">WARRANT AGREEMENT </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">To Purchase Shares of Common Stock of </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">X4 PHARMACEUTICALS, INC. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">Dated
as of March&nbsp;29, 2019 (the &#147;<U>Effective Date</U>&#148;) </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">WHEREAS, X4 Therapeutics, Inc., formerly known as X4 Pharmaceuticals, Inc., a Delaware
corporation (the &#147;<U>X4 Therapeutics</U>&#148;) previously entered into a Loan and Security Agreement, dated October&nbsp;19, 2018 (as amended, the &#147;<U>Loan Agreement</U>&#148;) with Hercules Capital, Inc., a Maryland corporation, in its
capacity as administrative and collateral agent, and Hercules Capital, Inc. (the &#147;<U>Warrantholder</U>&#148;) and the other lender parties thereto; </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">WHEREAS, X4 Therapeutics is a wholly owned subsidiary of X4 Pharmaceuticals, Inc., a Delaware corporation, formerly known as Arsanis, Inc.; </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">WHERAS, on October&nbsp;19, 2018, X4 Therapeutics issued to Warrantholder a warrant to purchase shares of X4 Therapeutics valued at $396,000 (as modified, the
&#147;<U>Original Tranche 1 Warrant</U>&#148;); </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">WHEREAS, pursuant to a Warrant Modification Agreement dated as of December&nbsp;11, 2018, the Original
Tranche 1 Warrant was modified to exercisable for shares of Arsanis Common Stock, as defined, therein. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">WHEREAS, the parties desire to amend and restate
the Original Warrant; </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">NOW, THEREFORE, in consideration of the mutual covenants and agreements contained herein, the Company (as defined below) and the
Warrantholder hereby amend and restate the Original Tranche 1 Warrant and agree as follows: </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 1. </B>GRANT OF THE RIGHT TO
PURCHASE COMMON STOCK. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">For value received, the Company hereby grants to the Warrantholder, and the Warrantholder is entitled, upon the terms and subject
to the conditions hereinafter set forth, to subscribe for and purchase, from the Company, an aggregate number of fully paid and <FONT STYLE="white-space:nowrap">non-assessable</FONT> shares of the Common Stock equal to the quotient derived by
dividing (a)&nbsp;the Warrant Coverage (as defined below) by (b)&nbsp;the Exercise Price (defined below). The Exercise Price of such shares is subject to adjustment as provided in Section&nbsp;8. As used herein, the following terms shall have the
following meanings: </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Act</U>&#148; means the Securities Act of 1933, as amended. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Charter</U>&#148; means the Company&#146;s Articles of Incorporation, Certificate of Incorporation or other constitutional document,
as may be amended from time to time. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Common Stock</U>&#148; means the Company&#146;s common stock, $0.001 par value per share;
</P> <P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Company</U>&#148; means X4 Pharmaceuticals, Inc., formerly known as Arsanis, Inc., a Delaware corporation, and any successor or
surviving entity that assumes the obligations of the Company under this Agreement pursuant to Section&nbsp;8(a). </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Exercise
Price</U>&#148; means $19.80 per share, subject to adjustment pursuant to Section&nbsp;8; </P> <P STYLE="font-size:18pt; margin-top:0pt; margin-bottom:0pt">&nbsp;</P>
</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">


<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Merger Event</U>&#148; means (i)&nbsp;any sale, lease, exclusive license or other
transfer of all or substantially all assets of the Company; (ii)any merger or consolidation involving the Company in which the Company is not the surviving entity, or in which the outstanding shares of the Company&#146;s capital stock are otherwise
converted into or exchanged for shares of capital stock, other securities or property of another entity; or (iii)&nbsp;any sale by holders of the outstanding voting equity securities of the Company in a single transaction or series of related
transactions of shares constituting a majority of the outstanding combined voting power of the Company; </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Purchase Price</U>&#148;
means, with respect to any exercise of this Agreement, an amount equal to the Exercise Price as of the relevant time multiplied by the number of shares of Common Stock requested to be exercised under this Agreement pursuant to such exercise; </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>SEC</U>&#148; means the United States Securities and Exchange Commission; and </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Warrant Coverage</U>&#148; means $396,000. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 2. </B>TERM OF THE AGREEMENT. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Except as otherwise provided for herein, the term of this Agreement and the right to purchase Common Stock as granted herein (the &#147;<U>Warrant</U>&#148;)
shall commence on the Effective Date and shall be exercisable for a period ending upon the earlier to occur of (i)&nbsp;October&nbsp;19, 2028 or (ii)&nbsp;termination pursuant to the terms hereunder. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 3. </B>EXERCISE OF THE PURCHASE RIGHTS. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(a) <U>Exercise</U>. The purchase rights set forth in this Agreement are exercisable by the Warrantholder, in whole or in part, at any time, or
from time to time, prior to the expiration of the term set forth in Section&nbsp;2, by tendering to the Company at its principal office a notice of exercise in the form attached hereto as <U>Exhibit I</U> (the &#147;<U>Notice of Exercise</U>&#148;),
duly completed and executed. Promptly upon receipt of the Notice of Exercise and the payment of the Purchase Price in accordance with the terms set forth below, and in no event later than three (3)&nbsp;days thereafter, the Company or its transfer
agent shall either (i)&nbsp;issue to the Warrantholder a certificate for the number of shares of Common Stock purchased or (ii)&nbsp;credit the same via book entry to the Warrantholder, and the Company shall execute the acknowledgment of exercise in
the form attached hereto as <U>Exhibit II</U> (the &#147;<U>Acknowledgment of Exercise</U>&#148;) indicating the number of shares which remain subject to future purchases, if any. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Purchase Price may be paid at the Warrantholder&#146;s election either (i)&nbsp;by cash or check, or (ii)&nbsp;by surrender of all or a portion of the
Warrant for shares of Common Stock to be exercised under this Agreement and, if applicable, an amended Agreement representing the remaining number of shares purchasable hereunder, as determined below (&#147;<U>Net Issuance</U>&#148;). If the
Warrantholder elects the Net Issuance method, the Company will issue Common Stock in accordance with the following formula: </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:13%; text-indent:4%; font-size:10pt; font-family:Times New Roman">X = <U><FONT STYLE="white-space:nowrap">Y(A-B)</FONT></U> </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:13%; text-indent:4%; font-size:10pt; font-family:Times New Roman">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;A </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Where:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;X =&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;the number of shares of
Common Stock to be issued to the Warrantholder. </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="10%">&nbsp;</TD>
<TD WIDTH="6%" VALIGN="top" ALIGN="left">Y&nbsp;=</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">the number of shares of Common Stock requested to be exercised under this Agreement. </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="10%">&nbsp;</TD>
<TD WIDTH="6%" VALIGN="top" ALIGN="left">A&nbsp;=</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">the fair market value of one (1)&nbsp;share of Common Stock at the time of exercise of such shares of Common
Stock. </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="10%">&nbsp;</TD>
<TD WIDTH="6%" VALIGN="top" ALIGN="left">B&nbsp;=</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">the then effective Exercise Price. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">For purposes of the above calculation, current fair market value of Common Stock shall mean with respect to each share of Common Stock: </P>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="13%">&nbsp;</TD>
<TD WIDTH="4%" VALIGN="top" ALIGN="left">(i)</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">Reserved. </P></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="13%">&nbsp;</TD>
<TD WIDTH="4%" VALIGN="top" ALIGN="left">(ii)</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"></P></TD></TR></TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">2 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:13%; text-indent:4%; font-size:10pt; font-family:Times New Roman">(A) if the Common Stock is traded on a securities exchange, the fair market
value shall be deemed to be the prior day closing price before the day the current fair market value of the securities is being determined; or </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:13%; text-indent:4%; font-size:10pt; font-family:Times New Roman">(B) if the Common Stock is traded
<FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">over-the-counter,</FONT></FONT> the fair market value shall be deemed to be the prior day closing bid and asked price quoted on the Nasdaq system (or similar system) before the day
the current fair market value of the securities is being determined; </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:8%; text-indent:4%; font-size:10pt; font-family:Times New Roman">(iii) if at any time the Common Stock is not listed
on any securities exchange or quoted in the Nasdaq National Market or the <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">over-the-counter</FONT></FONT> market, the current fair market value of Common Stock shall be the highest
price per share which the Company could obtain from a willing buyer (not a current employee or director) for shares of Common Stock sold by the Company, from authorized but unissued shares, as determined in good faith by its Board of Directors,
unless the Company shall become subject to a Merger Event, in which case the fair market value of Common Stock shall be deemed to be the per share value received by the holders of the Company&#146;s Common Stock on a common equivalent basis pursuant
to such Merger Event. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Upon partial exercise by either cash or Net Issuance, the Company shall promptly issue an amended warrant agreement representing
the remaining number of shares purchasable hereunder. All other terms and conditions of such amended Agreement shall be identical to those contained herein, including, but not limited to the Effective Date hereof. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(b) <U>Exercise Prior to Expiration</U>. To the extent this Agreement is not previously exercised as to all shares of Common Stock subject
hereto, and if the then current fair market value of one share of the Common Stock is greater than the Exercise Price then in effect, this Agreement shall be deemed automatically exercised pursuant to Section&nbsp;3(a) (even if not surrendered)
immediately before its expiration. For purposes of such automatic exercise, the fair market value of one share of the Common Stock upon such expiration shall be determined pursuant to Section&nbsp;3(a). To the extent this Agreement or any portion
thereof is deemed automatically exercised pursuant to this Section&nbsp;3(b), the Company agrees to promptly notify the Warrantholder of the number of shares of Common Stock, if any, the Warrantholder is to receive by reason of such automatic
exercise, and to issue or cause its transfer agent to issue a certificate or a book entry credit to the Warrantholder evidencing such shares. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 4. </B>RESERVATION OF SHARES. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">During
the term of this Agreement, the Company will at all times have authorized and reserved a sufficient number of shares of its Common Stock to provide for the exercise of the rights to purchase Common Stock as provided for herein. If at any time during
the term hereof the number of authorized but unissued shares of Common Stock shall not be sufficient to permit exercise of this Warrant in full, the Company will use its commercially reasonable efforts to take such corporate action as may, in the
opinion of its counsel, be necessary to increase its authorized but unissued shares of Common Stock to such number of shares as shall be sufficient for such purposes. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 5. </B>NO FRACTIONAL SHARES OR SCRIP. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">No fractional shares or scrip representing fractional shares shall be issued upon the exercise of this Agreement, but in lieu of such fractional shares the
Company shall make a cash payment therefor upon the basis of the then fair market value of one share of Common Stock. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 6.
</B>NO RIGHTS AS SHAREHOLDER/STOCKHOLDER. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">This Agreement does not entitle the Warrantholder to any voting rights or other rights as a
shareholder/stockholder of the Company prior to the exercise of this Agreement. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">3 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 7. </B>WARRANTHOLDER REGISTRY. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company shall maintain a registry showing the name and address of the registered holder of this Agreement. The Warrantholder&#146;s initial address, for
purposes of such registry, is set forth in Section&nbsp;12(g). The Warrantholder may change such address by giving written notice of such changed address to the Company. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 8. </B>ADJUSTMENT RIGHTS. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The
Exercise Price and the number of shares of Common Stock purchasable hereunder are subject to adjustment, as follows: </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(a) <U>Merger
Event</U>. If at any time there shall be a Merger Event, this Warrant shall, on and after the closing thereof, automatically and without further action on the part of any party or other person, represent the right to receive the consideration
(including, without limitation, cash, securities or other property (collectively, &#147;<U>Reference Property</U>&#148;)) payable on or in respect of all shares of Common Stock that are issuable hereunder as of immediately prior to the closing of
such Merger Event less the Purchase Price for all such shares of Common Stock, and such Merger Event consideration shall be paid to Warrantholder as and when it is paid to the holders of the outstanding shares of Common Stock and this Warrant shall
thereupon automatically terminate. Appropriate adjustment (as determined in good faith by the Company&#146;s Board of Directors and reasonably acceptable to the Warrantholder) shall be made in the application of the provisions of this Agreement with
respect to the rights and interests of the Warrantholder after the Merger Event to the end that the provisions of this Agreement (including adjustments of the Exercise Price, and adjustments to ensure that the provisions of this Section&nbsp;8 shall
thereafter be applicable, as nearly as possible, to the purchase rights under this Agreement in relation to any Reference Property thereafter acquirable upon exercise of such purchase rights) shall continue to be applicable in their entirety, and to
the greatest extent possible. To the extent this Warrant or any portion thereof is deemed automatically exercised pursuant to this Section&nbsp;8(a), the Company agrees to promptly notify the Warrantholder of the Reference Property, if any, the
Warrantholder is to receive by reason of such automatic exercise. Notwithstanding anything to the contrary in this Warrant, if the aggregate fair market value of the Reference Property payable under this Section&nbsp;8(a) is less than the aggregate
Exercise Price of this Warrant, then this Warrant shall automatically terminate immediately prior to the closing of such Merger Event without and Reference Property or other consideration being paid to the Warrantholder. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(b) <U>Reclassification of Shares</U>. Except for Merger Events subject to Sections 8(a), if the Company at any time shall, by combination,
reclassification, exchange or subdivision of securities or otherwise, change any of the securities as to which purchase rights under this Agreement exist into the same or a different number of securities of any other class or classes, this Agreement
shall thereafter represent the right to acquire such number and kind of securities as would have been issuable as the result of such change with respect to the securities which were subject to the purchase rights under this Agreement immediately
prior to such combination, reclassification, exchange, subdivision or other change. The provisions of this Section&nbsp;8(b) shall similarly apply to any successive combination, reclassification, exchange, subdivision or other change. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(c) <U>Subdivision or Combination of Shares</U>. If the Company at any time shall combine or subdivide its Common Stock, (i)&nbsp;in the case
of a subdivision, the Exercise Price shall be proportionately decreased and the number of shares of Common Stock issuable hereunder shall be proportionately increased, or (ii)&nbsp;in the case of a combination, the Exercise Price shall be
proportionately increased and the number of shares of Common Stock issuable hereunder shall be proportionately decreased. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(d)
<U>Dividends</U>. If the Company at any time while this Agreement is outstanding and unexpired shall: </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:8%; text-indent:4%; font-size:10pt; font-family:Times New Roman">(i) pay a dividend
with respect to the Common Stock payable in Common Stock, then the Exercise Price shall be adjusted, from and after the date of determination of stockholders entitled to receive such dividend or distribution, to that price determined by multiplying
the Exercise Price in effect immediately prior to such date of </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">4 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:8%; font-size:10pt; font-family:Times New Roman">
determination by a fraction (A)&nbsp;the numerator of which shall be the total number of shares of Common Stock outstanding immediately prior to such dividend or distribution, and (B)&nbsp;the
denominator of which shall be the total number of shares of Common Stock outstanding immediately after such dividend or distribution; or </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:8%; text-indent:4%; font-size:10pt; font-family:Times New Roman">(ii) make any other dividend or distribution with respect to Common Stock, except any dividend or distribution specifically
provided for in any other clause of this Section&nbsp;8, then, in each such case, provision shall be made by the Company such that the Warrantholder shall receive upon exercise or conversion of this Warrant a proportionate share of any such dividend
or distribution as though it were the holder of the Common Stock as of the record date fixed for the determination of the stockholders of the Company entitled to receive such dividend or distribution. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(e) <U>Notice of Adjustments</U>. If: (i)&nbsp;the Company shall declare any dividend or distribution upon its stock, whether in stock, cash,
property or other securities; (ii)&nbsp;there shall be any Merger Event; or (iii)&nbsp;there shall be any voluntary dissolution, liquidation or winding up of the Company; then, in connection with each such event, the Company shall send to the
Warrantholder: (A)&nbsp;at least thirty (30)&nbsp;days&#146; prior written notice of the date on which the books of the Company shall close or a record shall be taken for such dividend, distribution, subscription rights (specifying the date on which
the holders of Common Stock shall be entitled thereto) or for determining rights to vote in respect of such Merger Event, dissolution, liquidation or winding up; and (B)&nbsp;in the case of any such Merger Event, dissolution, liquidation or winding
up, at least thirty (30)&nbsp;days&#146; prior written notice of the date when the same shall take place (and specifying the date on which the holders of Common Stock shall be entitled to exchange their Common Stock for securities or other property
deliverable upon such Merger Event, dissolution, liquidation or winding up). </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Each such written notice shall set forth, in reasonable detail, (i)&nbsp;the
event requiring the notice, and (ii)&nbsp;if any adjustment is required to be made, (A)&nbsp;the amount of such adjustment, (B)&nbsp;the method by which such adjustment was calculated, (C)&nbsp;the adjusted Exercise Price (if the Exercise Price has
been adjusted), and (D)&nbsp;the number of shares subject to purchase hereunder after giving effect to such adjustment, and shall be given in accordance with Section&nbsp;12(g). </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(f) <U>Timely Notice</U>. Failure to timely provide such notice required by Section&nbsp;8(f) above shall entitle the Warrantholder to retain
the benefit of the applicable notice period notwithstanding anything to the contrary contained in any insufficient notice received by the Warrantholder. For purposes of this Section&nbsp;8(e), and notwithstanding anything to the contrary in
Section&nbsp;12(g), the notice period shall begin on the date the Warrantholder actually receives a written notice containing all the information required to be provided in such Section&nbsp;12(g). </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 9. </B>REPRESENTATIONS, WARRANTIES AND COVENANTS OF THE COMPANY. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(a) <U>Reservation of Common Stock</U>. The Common Stock issuable upon exercise of the Warrantholder&#146;s rights has been duly and validly
reserved and, when issued in accordance with the provisions of this Agreement, will be validly issued, fully paid and <FONT STYLE="white-space:nowrap">non-assessable,</FONT> and will be free of any taxes, liens, charges or encumbrances of any nature
whatsoever; <U>provided</U>, that the Common Stock issuable pursuant to this Agreement may be subject to restrictions on transfer under state and/or federal securities laws. The Company has made available to the Warrantholder true, correct and
complete copies of its Charter and current bylaws. The issuance of certificates for shares of Common Stock upon exercise of this Agreement shall be made without charge to the Warrantholder for any issuance tax in respect thereof, or other cost
incurred by the Company in connection with such exercise and the related issuance of shares of Common Stock; <U>provided</U>, that the Company shall not be required to pay any tax which may be payable in respect of any transfer and the issuance and
delivery of any certificate in a name other than that of the Warrantholder. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">5 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(b) <U>Due Authority</U>. The execution and delivery by the Company of this Agreement and
the performance of all obligations of the Company hereunder, including the issuance to the Warrantholder of the right to acquire the shares of Common Stock have been duly authorized by all necessary corporate action on the part of the Company. This
Agreement: (i)&nbsp;does not violate the Charter or the Company&#146;s current bylaws; (ii)&nbsp;does not contravene any law or governmental rule, regulation or order applicable to the Company; and (iii)&nbsp;does not and will not contravene any
provision of, or constitute a default under, any indenture, mortgage, contract or other instrument to which the Company is a party or by which it is bound. This Agreement constitutes a legal, valid and binding agreement of the Company, enforceable
in accordance with its terms. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(c) <U>Consents and Approvals</U>. No consent or approval of, giving of notice to, registration with, or
taking of any other action in respect of any state, federal or other governmental authority or agency is required with respect to the execution, delivery and performance by the Company of its obligations under this Agreement, except for the filing
of notices pursuant to Regulation D under the Act and any filing required by applicable state securities law, which filings will be effective by the time required thereby. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(d) <U>Exempt Transaction</U>. Subject to the accuracy of the Warrantholder&#146;s representations in Section&nbsp;10, the issuance of the
Common Stock upon exercise of this Agreement will constitute a transaction exempt from (i)&nbsp;the registration requirements of Section&nbsp;5 of the Act, in reliance upon Section&nbsp;4(2) thereof, and (ii)&nbsp;the qualification requirements of
the applicable state securities laws. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(e) <U>Compliance with Rule 144</U>. The Company shall, at all times prior to the earlier to occur
of (i)&nbsp;the date of sale or other disposition by Warrantholder of this Warrant or all shares of Common Stock issued on exercise of this Warrant, or (ii)&nbsp;the expiration or earlier termination of this Warrant if the Warrant has not been
exercised in full or in part on such date, use all commercially reasonable efforts to timely file all reports required under the Exchange Act and otherwise timely take all actions necessary to permit the Warrantholder to sell or otherwise dispose of
this Warrant and the shares of Common Stock issued on exercise hereof pursuant to Rule 144 promulgated under the Act (&#147;Rule 144&#148;), provided that the foregoing shall not apply in the event of a Merger Event following which the successor or
surviving entity is not subject to the reporting requirements of the Exchange Act. If the Warrantholder proposes to sell Common Stock issuable upon the exercise of this Agreement in compliance with Rule 144 promulgated by the SEC, then, upon the
Warrantholder&#146;s written request to the Company, the Company shall furnish to the Warrantholder, within ten days after receipt of such request, a written statement confirming the Company&#146;s compliance with the filing requirements of the SEC
as set forth in such Rule, as such Rule may be amended from time to time. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 10. </B>REPRESENTATIONS AND COVENANTS OF THE
WARRANTHOLDER. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">This Agreement has been entered into by the Company in reliance upon the following representations and covenants of the Warrantholder: </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(a) <U>Investment Purpose</U>. The right to acquire Common Stock is being acquired for investment and not with a view to the sale or
distribution of any part thereof, and the Warrantholder has no present intention of selling or engaging in any public distribution of such rights or the Common Stock except pursuant to an effective registration statement or an exemption from the
registration requirements of the Act. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(b) <U>Private Issue</U>. The Warrantholder understands (i)&nbsp;that the Common Stock issuable upon
exercise of this Agreement is not registered under the Act or qualified under applicable state securities laws on the ground that the issuance contemplated by this Agreement will be exempt from the registration and qualifications requirements
thereof, and (ii)&nbsp;that the Company&#146;s reliance on such exemption is predicated on the representations set forth in this Section&nbsp;10. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">6 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(c) <U>Financial Risk</U>. The Warrantholder has such knowledge and experience in financial
and business matters as to be capable of evaluating the merits and risks of its investment, and has the ability to bear the economic risks of its investment. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(d) <U>Accredited Investor</U>. The Warrantholder is an &#147;accredited investor&#148; within the meaning of the Securities and Exchange Rule
501 of Regulation D, as presently in effect. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 11. </B>TRANSFERS. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Subject to compliance with applicable federal and state securities laws, this Agreement and all rights hereunder are transferable, in whole or in part, without
charge to the holder hereof (except for transfer taxes) upon surrender of this Agreement properly endorsed. Each taker and holder of this Agreement, by taking or holding the same, consents and agrees that this Agreement, when endorsed in blank,
shall be deemed negotiable, and that the holder hereof, when this Agreement shall have been so endorsed and its transfer recorded on the Company&#146;s books, shall be treated by the Company and all other persons dealing with this Agreement as the
absolute owner hereof for any purpose and as the person entitled to exercise the rights represented by this Agreement. The transfer of this Agreement shall be recorded on the books of the Company upon receipt by the Company of a notice of transfer
in the form attached hereto as Exhibit III (the &#147;<U>Transfer Notice</U>&#148;), at its principal offices and the payment to the Company of all transfer taxes and other governmental charges imposed on such transfer. Until the Company receives
such Transfer Notice, the Company may treat the registered owner hereof as the owner for all purposes. Notwithstanding anything herein to the contrary, the Company shall not require an opinion of counsel in connection with any sale, assignment or
other transfer by the Warrantholder of this Warrant (or any portion hereof or any interest herein) or of any shares of Common Stock issued upon any exercise hereof to an affiliate (as defined in Regulation D) of the Warrantholder, provided that such
affiliate is an &#147;accredited investor&#148; as defined in Regulation D. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 12. </B>MISCELLANEOUS. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(a) <U>Effective Date</U>. The provisions of this Agreement shall be construed and shall be given effect in all respects as if it had been
executed and delivered by the Company on the date hereof. This Agreement shall be binding upon any successors or assigns of the Company. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(b) <U>Remedies</U>. In the event of any default hereunder, the <FONT STYLE="white-space:nowrap">non-defaulting</FONT> party may proceed to
protect and enforce its rights either by suit in equity and/or by action at law, including but not limited to an action for damages as a result of any such default, and/or an action for specific performance for any default where the Warrantholder
will not have an adequate remedy at law and where damages will not be readily ascertainable. The Company expressly agrees that it shall not oppose an application by the Warrantholder or any other person entitled to the benefit of this Agreement
requiring specific performance of any or all provisions hereof or enjoining the Company from continuing to commit any such breach of this Agreement. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(c) <U>No Impairment of Rights</U>. The Company will not, by amendment of its Charter or through any other means, avoid or seek to avoid the
observance or performance of any of the terms of this Agreement, but will at all times in good faith assist in the carrying out of all such terms and in the taking of all such actions as may be necessary or appropriate in order to protect the rights
of the Warrantholder against impairment. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(d) <U>Additional Documents</U>. The Company shall supply documentation reasonably necessary to
evaluate whether to exercise this Warrant, including without limitation, (i)&nbsp;any merger/purchase/asset sale agreement and related documents and estimated payout allocations to each of the respective shareholders, warrant and option holders in
connection with a Merger Event, (ii)&nbsp;the most recent capitalization tables, and (iii)&nbsp;the most recent Charter, in the case of information provided pursuant to clauses (i)&nbsp;and (ii) above, subject to the Warrantholder having
confidentiality obligations with respect thereto reasonably acceptable to the Company. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">7 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(e) <U>Attorney&#146;s Fees</U>. In any litigation, arbitration or court proceeding between
the Company and the Warrantholder relating hereto, the prevailing party shall be entitled to attorneys&#146; fees and expenses and all costs of proceedings incurred in enforcing this Agreement. For the purposes of this Section&nbsp;12(e),
attorneys&#146; fees shall include without limitation fees incurred in connection with the following: (i)&nbsp;contempt proceedings; (ii)&nbsp;discovery; (iii) any motion, proceeding or other activity of any kind in connection with an insolvency
proceeding; (iv)&nbsp;garnishment, levy, and debtor and third party examinations; and (v)&nbsp;post-judgment motions and proceedings of any kind, including without limitation any activity taken to collect or enforce any judgment. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(f) <U>Severability</U>. In the event any one or more of the provisions of this Agreement shall for any reason be held invalid, illegal or
unenforceable, the remaining provisions of this Agreement shall be unimpaired, and the invalid, illegal or unenforceable provision shall be replaced by a mutually acceptable valid, legal and enforceable provision, which comes closest to the
intention of the parties underlying the invalid, illegal or unenforceable provision. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(g) <U>Notices</U>. Except as otherwise provided
herein, any notice, demand, request, consent, approval, declaration, service of process or other communication that is required, contemplated, or permitted under this Agreement or with respect to the subject matter hereof shall be in writing, and
shall be deemed to have been validly served, given, delivered, and received upon the earlier of: (i)&nbsp;the day of transmission by facsimile or hand delivery if transmission or delivery occurs on a business day at or before 5:00 pm in the time
zone of the recipient, or, if transmission or delivery occurs on a <FONT STYLE="white-space:nowrap">non-business</FONT> day or after such time, the first business day thereafter, or the first business day after deposit with an overnight express
service or overnight mail delivery service; or (ii)&nbsp;the third (3<SUP STYLE="font-size:85%; vertical-align:top">rd</SUP>) calendar day after deposit in the United States mails, with proper first class postage prepaid, and shall be addressed to
the party to be notified as follows: </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">If to the Warrantholder: </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">HERCULES CAPITAL, INC. </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Legal
Department </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Attention: Chief Legal Officer and Bryan Jadot </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">400 Hamilton Avenue, Suite 310 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Palo Alto, CA 94301 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Email:
legal@herculestech.com; bjadot@htgc.com </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Telephone:
<FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">650-289-3060</FONT></FONT> </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">(i)</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">If to the Company: </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">X4 Pharmaceuticals, Inc. </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Attention: Adam Mostafa and Brian Bowersox </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">955 Massachusetts Avenue, 4th Floor </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Boston, MA 02139 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Email:
adam.mostafa@x4pharma.com and brian.bowersox@x4pharma.com </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Telephone:
<FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">617-542-6000</FONT></FONT> </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">or to such other address as each party may designate for
itself by like notice. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(h) <U>Entire Agreement; Amendments</U>. This Agreement constitutes the entire agreement and understanding of the
parties hereto in respect of the subject matter hereof, and supersedes and replaces in their entirety any prior proposals, term sheets, letters, negotiations or other documents or agreements, whether written or oral, with respect to the subject
matter hereof (including the Warrantholder&#146;s proposal letter dated September&nbsp;13, 2018 and the Original Tranche 1 Warrant). None of the terms of this Agreement may be amended except by an instrument executed by each of the parties hereto.
</P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(i) <U>Headings</U>. The various headings in this Agreement are inserted for convenience only and shall not affect the meaning or
interpretation of this Agreement or any provisions hereof. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">8 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(j) <U>No Strict Construction</U>. The parties hereto have participated jointly in the
negotiation and drafting of this Agreement. In the event an ambiguity or question of intent or interpretation arises, this Agreement shall be construed as if drafted jointly by the parties hereto and no presumption or burden of proof shall arise
favoring or disfavoring any party by virtue of the authorship of any provisions of this Agreement. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(k) <U>No Waiver</U>. No omission or
delay by the Warrantholder at any time to enforce any right or remedy reserved to it, or to require performance of any of the terms, covenants or provisions hereof by the Company at any time designated, shall be a waiver of any such right or remedy
to which the Warrantholder is entitled, nor shall it in any way affect the right of the Warrantholder to enforce such provisions thereafter. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(l) <U>Survival</U>. All agreements, representations and warranties contained in this Agreement or in any document delivered pursuant hereto
shall be for the benefit of the Warrantholder and shall survive the execution and delivery of this Agreement and the expiration or other termination of this Agreement. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(m) <U>Governing Law</U>. This Agreement has been negotiated and delivered to Warrantholder in the State of California, and shall have been
accepted by the Warrantholder in the State of California. Delivery of Common Stock to the Warrantholder by the Company under this Agreement is due in the State of California. This Agreement shall be governed by, and construed and enforced in
accordance with, the laws of the State of Delaware, excluding conflict of laws principles that would cause the application of laws of any other jurisdiction. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(n) <U>Consent to Jurisdiction and Venue</U>. All judicial proceedings arising in or under or related to this Agreement may be brought in any
state or federal court of competent jurisdiction located in the State of California. By execution and delivery of this Agreement, each party hereto generally and unconditionally: (i)&nbsp;consents to personal jurisdiction in Santa Clara County,
State of California; (ii)&nbsp;waives any objection as to jurisdiction or venue in Santa Clara County, State of California; (c)&nbsp;agrees not to assert any defense based on lack of jurisdiction or venue in the aforesaid courts; and
(iii)&nbsp;irrevocably agrees to be bound by any judgment rendered thereby in connection with this Agreement. Service of process on any party hereto in any action arising out of or relating to this Agreement shall be effective if given in accordance
with the requirements for notice set forth in Section&nbsp;12(g), and shall be deemed effective and received as set forth in Section&nbsp;12(g). Nothing herein shall affect the right to serve process in any other manner permitted by law or shall
limit the right of either party to bring proceedings in the courts of any other jurisdiction. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(o) <U>Mutual Waiver of Jury Trial</U>.
Because disputes arising in connection with complex financial transactions are most quickly and economically resolved by an experienced and expert person and the parties wish applicable state and federal laws to apply (rather than arbitration
rules), the parties desire that their disputes be resolved by a judge applying such applicable laws. EACH OF THE COMPANY AND THE WARRANTHOLDER SPECIFICALLY WAIVES ANY RIGHT IT MAY HAVE TO TRIAL BY JURY OF ANY CAUSE OF ACTION, CLAIM, CROSS-CLAIM,
COUNTERCLAIM, THIRD PARTY CLAIM OR ANY OTHER CLAIM (COLLECTIVELY, &#147;CLAIMS&#148;) ASSERTED BY THE COMPANY AGAINST THE WARRANTHOLDER OR ITS ASSIGNEE OR BY THE WARRANTHOLDER OR ITS ASSIGNEE AGAINST THE COMPANY. This waiver extends to all such
Claims, including Claims that involve Persons other than the Company and the Warrantholder; Claims that arise out of or are in any way connected to the relationship between the Company and the Warrantholder; and any Claims for damages, breach of
contract, specific performance, or any equitable or legal relief of any kind, arising out of this Agreement. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(p) <U>Judicial
Reference</U>. If the waiver of jury trial set forth above is ineffective or unenforceable, the parties agree that all Claims shall be resolved by reference to a private judge sitting without a jury, pursuant to Code of Civil Procedure
Section&nbsp;638, before a mutually acceptable referee or, if the parties cannot agree, a referee selected by the Presiding Judge of Santa Clara County, California. Such proceeding shall be conducted in Santa Clara County, California, with Delaware
rules of evidence and discovery applicable to such proceeding. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">9 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(q) <U>Prejudgment Relief</U>. In the event Claims are to be resolved by arbitration, either
party may seek from a court of competent jurisdiction identified in Section&nbsp;12(n), any prejudgment order, writ or other relief and have such prejudgment order, writ or other relief enforced to the fullest extent permitted by law notwithstanding
that all Claims are otherwise subject to resolution by judicial reference. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(r) <U>Counterparts</U>. This Agreement and any amendments,
waivers, consents or supplements hereto may be executed in any number of counterparts, and by different parties hereto in separate counterparts, each of which when so delivered shall be deemed an original, but all of which counterparts shall
constitute but one and the same instrument. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">[Remainder of Page Intentionally Left Blank] </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">10 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be executed by its officers thereunto
duly authorized as of the Effective Date. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="47%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="4%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="47%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; text-indent:2.00em; font-size:10pt; font-family:Times New Roman">COMPANY:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3">X4 PHARMACEUTICALS, INC.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">/s/ Adam Mostafa</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Name:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Adam Mostafa</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Title:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Chief Financial Officer</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="4"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; text-indent:2.00em; font-size:10pt; font-family:Times New Roman">WARRANTHOLDER:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3">HERCULES CAPITAL, INC.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">/s/ Jennifer Choe</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Name:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Jennifer Choe</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Title:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Assistant General Counsel</TD></TR>
</TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">11 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">EXHIBIT I </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">NOTICE OF EXERCISE </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">To:</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">X4 PHARMACEUTICALS, INC. </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">(1)</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">The undersigned Warrantholder hereby elects to purchase [_______] shares of the Common Stock of X4
Pharmaceuticals, Inc., pursuant to the terms of the Warrant Agreement, dated as of March&nbsp;29, 2019 (the &#147;Agreement&#148;) between X4 Pharmaceuticals, Inc. and the Warrantholder, and [CASH PAYMENT: tenders herewith payment of the Purchase
Price in full, together with all applicable transfer taxes, if any.] [NET ISSUANCE: elects pursuant to Section&nbsp;3(a) of the Agreement to effect a Net Issuance.] </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">(2)</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">Please issue a certificate or certificates representing said shares of Common Stock in the name of the
undersigned or in such other name as is specified below. </P></TD></TR></TABLE> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


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<TD WIDTH="47%"></TD>
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<TD WIDTH="4%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="47%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3"> <P STYLE="line-height:3.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">(Name)</P></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="4"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3"> <P STYLE="line-height:3.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">(Address)</P></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="4"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">WARRANTHOLDER:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3">HERCULES CAPITAL, INC.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Name:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Title:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Date:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
</TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">12 </P>

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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">EXHIBIT II </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">ACKNOWLEDGMENT OF EXERCISE </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The undersigned
[&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;], hereby acknowledges receipt of the &#147;Notice of Exercise&#148; from Hercules Capital, Inc., to purchase
[&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;] shares of the Common Stock of X4 Pharmaceuticals, Inc., pursuant to the terms of the Warrant Agreement by and between X4 Pharmaceuticals, Inc. and Hercules Capital, Inc. dated as of March&nbsp;29,
2019 (the &#147;Agreement&#148;), and further acknowledges that [&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;] shares remain subject to purchase under the terms of the Agreement. </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="47%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="47%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; text-indent:2.00em; font-size:10pt; font-family:Times New Roman">COMPANY:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3">X4 PHARMACEUTICALS, INC.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Title:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Date:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
</TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">13 </P>

</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">


<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">EXHIBIT III </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">TRANSFER NOTICE </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">(To transfer or assign the
foregoing Agreement execute this form and supply required information. Do not use this form to purchase shares.) </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">FOR VALUE RECEIVED, the foregoing
Agreement and all rights evidenced thereby are hereby transferred and assigned to </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<P STYLE="line-height:8.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000;width:52%">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">(Please Print) </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">whose address is<U>
</U><U>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</U> </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P> <P STYLE="line-height:8.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000;width:52%">&nbsp;</P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="48%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="4%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="46%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Dated:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR></TABLE>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="48%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="14%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="36%"></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>

<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Holder&#146;s&nbsp;Signature:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Holder&#146;s Address:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Signature
Guaranteed:&nbsp;<U>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</U> </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">NOTE:&nbsp;The signature to this Transfer
Notice must correspond with the name as it appears on the face of the Agreement, without alteration or enlargement or any change whatever. Officers of corporations and those acting in a fiduciary or other representative capacity should file proper
evidence of authority to assign the foregoing Agreement. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">14 </P>

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<DOCUMENT>
<TYPE>EX-4.6
<SEQUENCE>3
<FILENAME>d726255dex46.htm
<DESCRIPTION>EX-4.6
<TEXT>
<HTML><HEAD>
<TITLE>EX-4.6</TITLE>
</HEAD>
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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>Exhibit 4.6 </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">THIS WARRANT, AND THE SECURITIES ISSUABLE UPON THE EXERCISE OF THIS WARRANT, HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE
&#147;ACT&#148;), OR ANY STATE SECURITIES LAWS. THEY MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED, OR HYPOTHECATED IN THE ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT RELATED THERETO OR AN OPINION OF COUNSEL (WHICH MAY BE COMPANY COUNSEL) REASONABLY
SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED UNDER THE ACT, OR ANY APPLICABLE STATE SECURITIES LAWS. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">WARRANT
AGREEMENT </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">To Purchase Shares of Common Stock of </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">X4 PHARMACEUTICALS, INC. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">Dated
as of March&nbsp;18, 2019 (the &#147;<U>Effective Date</U>&#148;) </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">WHEREAS, X4 Therapeutics, Inc., formerly known as X4 Pharmaceuticals, Inc., a Delaware
corporation (the &#147;<U>X4 Therapeutics</U>&#148;) previously entered into a Loan and Security Agreement, dated October&nbsp;19, 2018 (as amended, the &#147;<U>Loan Agreement</U>&#148;) with Hercules Capital, Inc., a Maryland corporation, in its
capacity as administrative and collateral agent, and Hercules Capital, Inc. (the &#147;<U>Warrantholder</U>&#148;) and the other lender parties thereto; </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">WHEREAS, X4 Therapeutics is a wholly owned subsidiary of X4 Pharmaceuticals, Inc., a Delaware corporation, formerly known as Arsanis, Inc.; </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">WHEREAS, the parties desire to enter into this warrant agreement (this &#147;<U>Agreement</U>&#148;) to pursuant to the terms of the Loan Agreement; </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">NOW, THEREFORE, in consideration of the mutual covenants and agreements contained herein, the Company (as defined below) and the Warrantholder agree as
follows: </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 1. </B>GRANT OF THE RIGHT TO PURCHASE COMMON STOCK. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">For value received, the Company hereby grants to the Warrantholder, and the Warrantholder is entitled, upon the terms and subject to the conditions hereinafter
set forth, to subscribe for and purchase, from the Company, an aggregate number of fully paid and <FONT STYLE="white-space:nowrap">non-assessable</FONT> shares of the Common Stock equal to the quotient derived by dividing (a)&nbsp;the Warrant
Coverage (as defined below) by (b)&nbsp;the Exercise Price (defined below). The Exercise Price of such shares is subject to adjustment as provided in Section&nbsp;8. As used herein, the following terms shall have the following meanings: </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Act</U>&#148; means the Securities Act of 1933, as amended. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Charter</U>&#148; means the Company&#146;s Articles of Incorporation, Certificate of Incorporation or other constitutional document,
as may be amended from time to time. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Common Stock</U>&#148; means the Company&#146;s common stock, $0.001 par value per share;
</P> <P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Company</U>&#148; means X4 Pharmaceuticals, Inc., formerly known as Arsanis, Inc., a Delaware corporation, and any successor or
surviving entity that assumes the obligations of the Company under this Agreement pursuant to Section&nbsp;8(a). </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Exercise
Price</U>&#148; means $19.80 per share, subject to adjustment pursuant to Section&nbsp;8; </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Merger Event</U>&#148; means
(i)&nbsp;any sale, lease, exclusive license or other transfer of all or substantially all assets of the Company; (ii)any merger or consolidation involving the Company in which the Company is not the surviving entity, or in which the outstanding
shares of the Company&#146;s capital stock are otherwise converted into or exchanged for shares of capital stock, other securities or property of another entity; or (iii)&nbsp;any sale by holders of the outstanding voting equity securities of the
Company in a single transaction or series of related transactions of shares constituting a majority of the outstanding combined voting power of the Company; </P>
</DIV></Center>


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<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">


<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Purchase Price</U>&#148; means, with respect to any exercise of this Agreement, an
amount equal to the Exercise Price as of the relevant time multiplied by the number of shares of Common Stock requested to be exercised under this Agreement pursuant to such exercise; </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>SEC</U>&#148; means the United States Securities and Exchange Commission; and </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman">&#147;<U>Warrant Coverage</U>&#148; means $99,000. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 2. </B>TERM OF THE AGREEMENT. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Except
as otherwise provided for herein, the term of this Agreement and the right to purchase Common Stock as granted herein (the &#147;<U>Warrant</U>&#148;) shall commence on the Effective Date and shall be exercisable for a period ending upon the earlier
to occur of (i)&nbsp;ten (10) years after the Effective Date or (ii)&nbsp;termination pursuant to the terms hereunder. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 3.
</B>EXERCISE OF THE PURCHASE RIGHTS. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(a) <U>Exercise</U>. The purchase rights set forth in this Agreement are exercisable by the
Warrantholder, in whole or in part, at any time, or from time to time, prior to the expiration of the term set forth in Section&nbsp;2, by tendering to the Company at its principal office a notice of exercise in the form attached hereto as
<U>Exhibit I</U> (the &#147;<U>Notice of Exercise</U>&#148;), duly completed and executed. Promptly upon receipt of the Notice of Exercise and the payment of the Purchase Price in accordance with the terms set forth below, and in no event later than
three (3)&nbsp;days thereafter, the Company or its transfer agent shall either (i)&nbsp;issue to the Warrantholder a certificate for the number of shares of Common Stock purchased or (ii)&nbsp;credit the same via book entry to the Warrantholder, and
the Company shall execute the acknowledgment of exercise in the form attached hereto as <U>Exhibit II</U> (the &#147;<U>Acknowledgment of Exercise</U>&#148;) indicating the number of shares which remain subject to future purchases, if any. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Purchase Price may be paid at the Warrantholder&#146;s election either (i)&nbsp;by cash or check, or (ii)&nbsp;by surrender of all or a portion of the
Warrant for shares of Common Stock to be exercised under this Agreement and, if applicable, an amended Agreement representing the remaining number of shares purchasable hereunder, as determined below (&#147;<U>Net Issuance</U>&#148;). If the
Warrantholder elects the Net Issuance method, the Company will issue Common Stock in accordance with the following formula: </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:13%; text-indent:4%; font-size:10pt; font-family:Times New Roman">X = <U><FONT STYLE="white-space:nowrap">Y(A-B)</FONT></U> </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:13%; text-indent:4%; font-size:10pt; font-family:Times New Roman">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;A </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD WIDTH="9%"></TD>
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<TD WIDTH="4%"></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD WIDTH="83%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">Where:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">X&nbsp;=&nbsp;&nbsp;&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">the number of shares of Common Stock to be issued to the Warrantholder.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Y&nbsp;=</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">the number of shares of Common Stock requested to be exercised under this Agreement.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">A&nbsp;=</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">the fair market value of one (1)&nbsp;share of Common Stock at the time of exercise of such shares of Common Stock.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">B&nbsp;=</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">the then effective Exercise Price.</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">For purposes of the above calculation, current fair market value of Common Stock shall mean with respect to each share of
Common Stock: </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:8%; text-indent:4%; font-size:10pt; font-family:Times New Roman">(i) Reserved. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:8%; text-indent:4%; font-size:10pt; font-family:Times New Roman">(ii) </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:13%; text-indent:4%; font-size:10pt; font-family:Times New Roman">(A) if the Common Stock is traded on a securities exchange, the fair market value shall be deemed to be the prior day closing
price before the day the current fair market value of the securities is being determined; or </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:13%; text-indent:4%; font-size:10pt; font-family:Times New Roman">(B) if the Common Stock is
traded <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">over-the-counter,</FONT></FONT> the fair market value shall be deemed to be the prior day closing bid and asked price quoted on the Nasdaq system (or similar system) before the
day the current fair market value of the securities is being determined; </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">2 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:8%; text-indent:4%; font-size:10pt; font-family:Times New Roman">(iii) if at any time the Common Stock is not listed on any securities
exchange or quoted in the Nasdaq National Market or the <FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">over-the-counter</FONT></FONT> market, the current fair market value of Common Stock shall be the highest price per share which
the Company could obtain from a willing buyer (not a current employee or director) for shares of Common Stock sold by the Company, from authorized but unissued shares, as determined in good faith by its Board of Directors, unless the Company shall
become subject to a Merger Event, in which case the fair market value of Common Stock shall be deemed to be the per share value received by the holders of the Company&#146;s Common Stock on a common equivalent basis pursuant to such Merger Event.
</P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Upon partial exercise by either cash or Net Issuance, the Company shall promptly issue an amended warrant agreement representing the remaining number of
shares purchasable hereunder. All other terms and conditions of such amended Agreement shall be identical to those contained herein, including, but not limited to the Effective Date hereof. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(b) <U>Exercise Prior to Expiration</U>. To the extent this Agreement is not previously exercised as to all shares of Common Stock subject
hereto, and if the then current fair market value of one share of the Common Stock is greater than the Exercise Price then in effect, this Agreement shall be deemed automatically exercised pursuant to Section&nbsp;3(a) (even if not surrendered)
immediately before its expiration. For purposes of such automatic exercise, the fair market value of one share of the Common Stock upon such expiration shall be determined pursuant to Section&nbsp;3(a). To the extent this Agreement or any portion
thereof is deemed automatically exercised pursuant to this Section&nbsp;3(b), the Company agrees to promptly notify the Warrantholder of the number of shares of Common Stock, if any, the Warrantholder is to receive by reason of such automatic
exercise, and to issue or cause its transfer agent to issue a certificate or a book entry credit to the Warrantholder evidencing such shares. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 4. </B>RESERVATION OF SHARES. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">During
the term of this Agreement, the Company will at all times have authorized and reserved a sufficient number of shares of its Common Stock to provide for the exercise of the rights to purchase Common Stock as provided for herein. If at any time during
the term hereof the number of authorized but unissued shares of Common Stock shall not be sufficient to permit exercise of this Warrant in full, the Company will use its commercially reasonable efforts to take such corporate action as may, in the
opinion of its counsel, be necessary to increase its authorized but unissued shares of Common Stock to such number of shares as shall be sufficient for such purposes. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 5. </B>NO FRACTIONAL SHARES OR SCRIP. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">No fractional shares or scrip representing fractional shares shall be issued upon the exercise of this Agreement, but in lieu of such fractional shares the
Company shall make a cash payment therefor upon the basis of the then fair market value of one share of Common Stock. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 6.
</B>NO RIGHTS AS SHAREHOLDER/STOCKHOLDER. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">This Agreement does not entitle the Warrantholder to any voting rights or other rights as a
shareholder/stockholder of the Company prior to the exercise of this Agreement. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 7. </B>WARRANTHOLDER REGISTRY. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company shall maintain a registry showing the name and address of the registered holder of this Agreement. The Warrantholder&#146;s initial address, for
purposes of such registry, is set forth in Section&nbsp;12(g). The Warrantholder may change such address by giving written notice of such changed address to the Company. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">3 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 8. </B>ADJUSTMENT RIGHTS. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Exercise Price and the number of shares of Common Stock purchasable hereunder are subject to adjustment, as follows: </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(a) <U>Merger Event</U>. If at any time there shall be a Merger Event, this Warrant shall, on and after the closing thereof, automatically and
without further action on the part of any party or other person, represent the right to receive the consideration (including, without limitation, cash, securities or other property (collectively, &#147;<U>Reference Property</U>&#148;)) payable on or
in respect of all shares of Common Stock that are issuable hereunder as of immediately prior to the closing of such Merger Event less the Purchase Price for all such shares of Common Stock, and such Merger Event consideration shall be paid to
Warrantholder as and when it is paid to the holders of the outstanding shares of Common Stock and this Warrant shall thereupon automatically terminate. Appropriate adjustment (as determined in good faith by the Company&#146;s Board of Directors and
reasonably acceptable to the Warrantholder) shall be made in the application of the provisions of this Agreement with respect to the rights and interests of the Warrantholder after the Merger Event to the end that the provisions of this Agreement
(including adjustments of the Exercise Price, and adjustments to ensure that the provisions of this Section&nbsp;8 shall thereafter be applicable, as nearly as possible, to the purchase rights under this Agreement in relation to any Reference
Property thereafter acquirable upon exercise of such purchase rights) shall continue to be applicable in their entirety, and to the greatest extent possible. To the extent this Warrant or any portion thereof is deemed automatically exercised
pursuant to this Section&nbsp;8(a), the Company agrees to promptly notify the Warrantholder of the Reference Property, if any, the Warrantholder is to receive by reason of such automatic exercise. Notwithstanding anything to the contrary in this
Warrant, if the aggregate fair market value of the Reference Property payable under this Section&nbsp;8(a) is less than the aggregate Exercise Price of this Warrant, then this Warrant shall automatically terminate immediately prior to the closing of
such Merger Event without and Reference Property or other consideration being paid to the Warrantholder. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(b) <U>Reclassification of
Shares</U>. Except for Merger Events subject to Sections 8(a), if the Company at any time shall, by combination, reclassification, exchange or subdivision of securities or otherwise, change any of the securities as to which purchase rights under
this Agreement exist into the same or a different number of securities of any other class or classes, this Agreement shall thereafter represent the right to acquire such number and kind of securities as would have been issuable as the result of such
change with respect to the securities which were subject to the purchase rights under this Agreement immediately prior to such combination, reclassification, exchange, subdivision or other change. The provisions of this Section&nbsp;8(b) shall
similarly apply to any successive combination, reclassification, exchange, subdivision or other change. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(c) <U>Subdivision or Combination
of Shares</U>. If the Company at any time shall combine or subdivide its Common Stock, (i)&nbsp;in the case of a subdivision, the Exercise Price shall be proportionately decreased and the number of shares of Common Stock issuable hereunder shall be
proportionately increased, or (ii)&nbsp;in the case of a combination, the Exercise Price shall be proportionately increased and the number of shares of Common Stock issuable hereunder shall be proportionately decreased. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(d) <U>Dividends</U>. If the Company at any time while this Agreement is outstanding and unexpired shall: </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; margin-left:8%; text-indent:4%; font-size:10pt; font-family:Times New Roman">(i) pay a dividend with respect to the Common Stock payable in Common Stock, then the Exercise Price shall be adjusted, from
and after the date of determination of stockholders entitled to receive such dividend or distribution, to that price determined by multiplying the Exercise Price in effect immediately prior to such date of determination by a fraction (A)&nbsp;the
numerator of which shall be the total number of shares of Common Stock outstanding immediately prior to such dividend or distribution, and (B)&nbsp;the denominator of which shall be the total number of shares of Common Stock outstanding immediately
after such dividend or distribution; or </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">4 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:8%; text-indent:4%; font-size:10pt; font-family:Times New Roman">(ii) make any other dividend or distribution with respect to Common Stock,
except any dividend or distribution specifically provided for in any other clause of this Section&nbsp;8, then, in each such case, provision shall be made by the Company such that the Warrantholder shall receive upon exercise or conversion of this
Warrant a proportionate share of any such dividend or distribution as though it were the holder of the Common Stock as of the record date fixed for the determination of the stockholders of the Company entitled to receive such dividend or
distribution. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(e) <U>Notice of Adjustments</U>. If: (i)&nbsp;the Company shall declare any dividend or distribution upon its stock,
whether in stock, cash, property or other securities; (ii)&nbsp;there shall be any Merger Event; or (iii)&nbsp;there shall be any voluntary dissolution, liquidation or winding up of the Company; then, in connection with each such event, the Company
shall send to the Warrantholder: (A)&nbsp;at least thirty (30)&nbsp;days&#146; prior written notice of the date on which the books of the Company shall close or a record shall be taken for such dividend, distribution, subscription rights (specifying
the date on which the holders of Common Stock shall be entitled thereto) or for determining rights to vote in respect of such Merger Event, dissolution, liquidation or winding up; and (B)&nbsp;in the case of any such Merger Event, dissolution,
liquidation or winding up, at least thirty (30)&nbsp;days&#146; prior written notice of the date when the same shall take place (and specifying the date on which the holders of Common Stock shall be entitled to exchange their Common Stock for
securities or other property deliverable upon such Merger Event, dissolution, liquidation or winding up). </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Each such written notice shall set forth, in
reasonable detail, (i)&nbsp;the event requiring the notice, and (ii)&nbsp;if any adjustment is required to be made, (A)&nbsp;the amount of such adjustment, (B)&nbsp;the method by which such adjustment was calculated, (C)&nbsp;the adjusted Exercise
Price (if the Exercise Price has been adjusted), and (D)&nbsp;the number of shares subject to purchase hereunder after giving effect to such adjustment, and shall be given in accordance with Section&nbsp;12(g). </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(f) <U>Timely Notice</U>. Failure to timely provide such notice required by Section&nbsp;8(f) above shall entitle the Warrantholder to retain
the benefit of the applicable notice period notwithstanding anything to the contrary contained in any insufficient notice received by the Warrantholder. For purposes of this Section&nbsp;8(e), and notwithstanding anything to the contrary in
Section&nbsp;12(g), the notice period shall begin on the date the Warrantholder actually receives a written notice containing all the information required to be provided in such Section&nbsp;12(g). </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 9. </B>REPRESENTATIONS, WARRANTIES AND COVENANTS OF THE COMPANY. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(a) <U>Reservation of Common Stock</U>. The Common Stock issuable upon exercise of the Warrantholder&#146;s rights has been duly and validly
reserved and, when issued in accordance with the provisions of this Agreement, will be validly issued, fully paid and <FONT STYLE="white-space:nowrap">non-assessable,</FONT> and will be free of any taxes, liens, charges or encumbrances of any nature
whatsoever; <U>provided</U>, that the Common Stock issuable pursuant to this Agreement may be subject to restrictions on transfer under state and/or federal securities laws. The Company has made available to the Warrantholder true, correct and
complete copies of its Charter and current bylaws. The issuance of certificates for shares of Common Stock upon exercise of this Agreement shall be made without charge to the Warrantholder for any issuance tax in respect thereof, or other cost
incurred by the Company in connection with such exercise and the related issuance of shares of Common Stock; <U>provided</U>, that the Company shall not be required to pay any tax which may be payable in respect of any transfer and the issuance and
delivery of any certificate in a name other than that of the Warrantholder. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(b) <U>Due Authority</U>. The execution and delivery by the
Company of this Agreement and the performance of all obligations of the Company hereunder, including the issuance to the Warrantholder of the right to acquire the shares of Common Stock have been duly authorized by all necessary corporate action on
the part of the Company. This Agreement: (i)&nbsp;does not violate the Charter or the Company&#146;s current bylaws; (ii)&nbsp;does not contravene any law or governmental rule, regulation or order applicable to the Company; and (iii)&nbsp;does not
and will not contravene any provision of, or constitute a </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">5 </P>

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default under, any indenture, mortgage, contract or other instrument to which the Company is a party or by which it is bound. This Agreement constitutes a legal, valid and binding agreement of
the Company, enforceable in accordance with its terms. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(c) <U>Consents and Approvals</U>. No consent or approval of, giving of notice to,
registration with, or taking of any other action in respect of any state, federal or other governmental authority or agency is required with respect to the execution, delivery and performance by the Company of its obligations under this Agreement,
except for the filing of notices pursuant to Regulation D under the Act and any filing required by applicable state securities law, which filings will be effective by the time required thereby. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(d) <U>Exempt Transaction</U>. Subject to the accuracy of the Warrantholder&#146;s representations in Section&nbsp;10, the issuance of the
Common Stock upon exercise of this Agreement will constitute a transaction exempt from (i)&nbsp;the registration requirements of Section&nbsp;5 of the Act, in reliance upon Section&nbsp;4(2) thereof, and (ii)&nbsp;the qualification requirements of
the applicable state securities laws. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(e) <U>Compliance with Rule 144</U>. The Company shall, at all times prior to the earlier to occur
of (i)&nbsp;the date of sale or other disposition by Warrantholder of this Warrant or all shares of Common Stock issued on exercise of this Warrant, or (ii)&nbsp;the expiration or earlier termination of this Warrant if the Warrant has not been
exercised in full or in part on such date, use all commercially reasonable efforts to timely file all reports required under the Exchange Act and otherwise timely take all actions necessary to permit the Warrantholder to sell or otherwise dispose of
this Warrant and the shares of Common Stock issued on exercise hereof pursuant to Rule 144 promulgated under the Act (&#147;Rule 144&#148;), provided that the foregoing shall not apply in the event of a Merger Event following which the successor or
surviving entity is not subject to the reporting requirements of the Exchange Act. If the Warrantholder proposes to sell Common Stock issuable upon the exercise of this Agreement in compliance with Rule 144 promulgated by the SEC, then, upon the
Warrantholder&#146;s written request to the Company, the Company shall furnish to the Warrantholder, within ten days after receipt of such request, a written statement confirming the Company&#146;s compliance with the filing requirements of the SEC
as set forth in such Rule, as such Rule may be amended from time to time. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 10. </B>REPRESENTATIONS AND COVENANTS OF THE
WARRANTHOLDER. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">This Agreement has been entered into by the Company in reliance upon the following representations and covenants of the Warrantholder: </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(a) <U>Investment Purpose</U>. The right to acquire Common Stock is being acquired for investment and not with a view to the sale or
distribution of any part thereof, and the Warrantholder has no present intention of selling or engaging in any public distribution of such rights or the Common Stock except pursuant to an effective registration statement or an exemption from the
registration requirements of the Act. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(b) <U>Private Issue</U>. The Warrantholder understands (i)&nbsp;that the Common Stock issuable upon
exercise of this Agreement is not registered under the Act or qualified under applicable state securities laws on the ground that the issuance contemplated by this Agreement will be exempt from the registration and qualifications requirements
thereof, and (ii)&nbsp;that the Company&#146;s reliance on such exemption is predicated on the representations set forth in this Section&nbsp;10. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(c) <U>Financial Risk</U>. The Warrantholder has such knowledge and experience in financial and business matters as to be capable of evaluating
the merits and risks of its investment, and has the ability to bear the economic risks of its investment. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(d) <U>Accredited Investor</U>.
The Warrantholder is an &#147;accredited investor&#148; within the meaning of the Securities and Exchange Rule 501 of Regulation D, as presently in effect. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">6 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 11. </B>TRANSFERS. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Subject to compliance with applicable federal and state securities laws, this Agreement and all rights hereunder are transferable, in whole or in part, without
charge to the holder hereof (except for transfer taxes) upon surrender of this Agreement properly endorsed. Each taker and holder of this Agreement, by taking or holding the same, consents and agrees that this Agreement, when endorsed in blank,
shall be deemed negotiable, and that the holder hereof, when this Agreement shall have been so endorsed and its transfer recorded on the Company&#146;s books, shall be treated by the Company and all other persons dealing with this Agreement as the
absolute owner hereof for any purpose and as the person entitled to exercise the rights represented by this Agreement. The transfer of this Agreement shall be recorded on the books of the Company upon receipt by the Company of a notice of transfer
in the form attached hereto as Exhibit III (the &#147;<U>Transfer Notice</U>&#148;), at its principal offices and the payment to the Company of all transfer taxes and other governmental charges imposed on such transfer. Until the Company receives
such Transfer Notice, the Company may treat the registered owner hereof as the owner for all purposes. Notwithstanding anything herein to the contrary, the Company shall not require an opinion of counsel in connection with any sale, assignment or
other transfer by the Warrantholder of this Warrant (or any portion hereof or any interest herein) or of any shares of Common Stock issued upon any exercise hereof to an affiliate (as defined in Regulation D) of the Warrantholder, provided that such
affiliate is an &#147;accredited investor&#148; as defined in Regulation D. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>SECTION 12. </B>MISCELLANEOUS. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(a) <U>Effective Date</U>. The provisions of this Agreement shall be construed and shall be given effect in all respects as if it had been
executed and delivered by the Company on the date hereof. This Agreement shall be binding upon any successors or assigns of the Company. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(b) <U>Remedies</U>. In the event of any default hereunder, the <FONT STYLE="white-space:nowrap">non-defaulting</FONT> party may proceed to
protect and enforce its rights either by suit in equity and/or by action at law, including but not limited to an action for damages as a result of any such default, and/or an action for specific performance for any default where the Warrantholder
will not have an adequate remedy at law and where damages will not be readily ascertainable. The Company expressly agrees that it shall not oppose an application by the Warrantholder or any other person entitled to the benefit of this Agreement
requiring specific performance of any or all provisions hereof or enjoining the Company from continuing to commit any such breach of this Agreement. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(c) <U>No Impairment of Rights</U>. The Company will not, by amendment of its Charter or through any other means, avoid or seek to avoid the
observance or performance of any of the terms of this Agreement, but will at all times in good faith assist in the carrying out of all such terms and in the taking of all such actions as may be necessary or appropriate in order to protect the rights
of the Warrantholder against impairment. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(d) <U>Additional Documents</U>. The Company shall supply documentation reasonably necessary to
evaluate whether to exercise this Warrant, including without limitation, (i)&nbsp;any merger/purchase/asset sale agreement and related documents and estimated payout allocations to each of the respective shareholders, warrant and option holders in
connection with a Merger Event, (ii)&nbsp;the most recent capitalization tables, and (iii)&nbsp;the most recent Charter, in the case of information provided pursuant to clauses (i)&nbsp;and (ii) above, subject to the Warrantholder having
confidentiality obligations with respect thereto reasonably acceptable to the Company. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(e) <U>Attorney&#146;s Fees</U>. In any litigation,
arbitration or court proceeding between the Company and the Warrantholder relating hereto, the prevailing party shall be entitled to attorneys&#146; fees and expenses and all costs of proceedings incurred in enforcing this Agreement. For the
purposes of this Section&nbsp;12(e), attorneys&#146; fees shall include without limitation fees incurred in connection with the following: (i)&nbsp;contempt proceedings; (ii)&nbsp;discovery; (iii) any motion, proceeding or other activity of any kind
in connection with an insolvency proceeding; (iv)&nbsp;garnishment, levy, and debtor and third party examinations; and (v)&nbsp;post-judgment motions and proceedings of any kind, including without limitation any activity taken to collect or enforce
any judgment. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">7 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(f) <U>Severability</U>. In the event any one or more of the provisions of this Agreement
shall for any reason be held invalid, illegal or unenforceable, the remaining provisions of this Agreement shall be unimpaired, and the invalid, illegal or unenforceable provision shall be replaced by a mutually acceptable valid, legal and
enforceable provision, which comes closest to the intention of the parties underlying the invalid, illegal or unenforceable provision. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(g)
<U>Notices</U>. Except as otherwise provided herein, any notice, demand, request, consent, approval, declaration, service of process or other communication that is required, contemplated, or permitted under this Agreement or with respect to the
subject matter hereof shall be in writing, and shall be deemed to have been validly served, given, delivered, and received upon the earlier of: (i)&nbsp;the day of transmission by facsimile or hand delivery if transmission or delivery occurs on a
business day at or before 5:00 pm in the time zone of the recipient, or, if transmission or delivery occurs on a <FONT STYLE="white-space:nowrap">non-business</FONT> day or after such time, the first business day thereafter, or the first business
day after deposit with an overnight express service or overnight mail delivery service; or (ii)&nbsp;the third (3<SUP STYLE="font-size:85%; vertical-align:top">rd</SUP>) calendar day after deposit in the United States mails, with proper first class
postage prepaid, and shall be addressed to the party to be notified as follows: </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">If to the Warrantholder: </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">HERCULES CAPITAL, INC. </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Legal
Department </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Attention: Chief Legal Officer and Bryan Jadot </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">400 Hamilton Avenue, Suite 310 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Palo Alto, CA 94301 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Email:
legal@herculestech.com; bjadot@htgc.com </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Telephone:
<FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">650-289-3060</FONT></FONT> </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">(i)</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">If to the Company: </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">X4 Pharmaceuticals, Inc. </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Attention: Adam Mostafa and Brian Bowersox </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">955 Massachusetts Avenue, 4th Floor </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Boston, MA 02139 </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Email:
adam.mostafa@x4pharma.com and brian.bowersox@x4pharma.com </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">Telephone:
<FONT STYLE="white-space:nowrap"><FONT STYLE="white-space:nowrap">617-542-6000</FONT></FONT> </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">or to such other address as each party may designate for
itself by like notice. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(h) <U>Entire Agreement; Amendments</U>. This Agreement constitutes the entire agreement and understanding of the
parties hereto in respect of the subject matter hereof, and supersedes and replaces in their entirety any prior proposals, term sheets, letters, negotiations or other documents or agreements, whether written or oral, with respect to the subject
matter hereof (including the Warrantholder&#146;s proposal letter dated September&nbsp;13, 2018). None of the terms of this Agreement may be amended except by an instrument executed by each of the parties hereto. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(i) <U>Headings</U>. The various headings in this Agreement are inserted for convenience only and shall not affect the meaning or
interpretation of this Agreement or any provisions hereof. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(j) <U>No Strict Construction</U>. The parties hereto have participated jointly
in the negotiation and drafting of this Agreement. In the event an ambiguity or question of intent or interpretation arises, this Agreement shall be construed as if drafted jointly by the parties hereto and no presumption or burden of proof shall
arise favoring or disfavoring any party by virtue of the authorship of any provisions of this Agreement. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">8 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(k) <U>No Waiver</U>. No omission or delay by the Warrantholder at any time to enforce any
right or remedy reserved to it, or to require performance of any of the terms, covenants or provisions hereof by the Company at any time designated, shall be a waiver of any such right or remedy to which the Warrantholder is entitled, nor shall it
in any way affect the right of the Warrantholder to enforce such provisions thereafter. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(l) <U>Survival</U>. All agreements,
representations and warranties contained in this Agreement or in any document delivered pursuant hereto shall be for the benefit of the Warrantholder and shall survive the execution and delivery of this Agreement and the expiration or other
termination of this Agreement. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(m) <U>Governing Law</U>. This Agreement has been negotiated and delivered to Warrantholder in the State of
California, and shall have been accepted by the Warrantholder in the State of California. Delivery of Common Stock to the Warrantholder by the Company under this Agreement is due in the State of California. This Agreement shall be governed by, and
construed and enforced in accordance with, the laws of the State of Delaware, excluding conflict of laws principles that would cause the application of laws of any other jurisdiction. </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(n) <U>Consent to Jurisdiction and Venue</U>. All judicial proceedings arising in or under or related to this Agreement may be brought in any
state or federal court of competent jurisdiction located in the State of California. By execution and delivery of this Agreement, each party hereto generally and unconditionally: (i)&nbsp;consents to personal jurisdiction in Santa Clara County,
State of California; (ii)&nbsp;waives any objection as to jurisdiction or venue in Santa Clara County, State of California; (c)&nbsp;agrees not to assert any defense based on lack of jurisdiction or venue in the aforesaid courts; and
(iii)&nbsp;irrevocably agrees to be bound by any judgment rendered thereby in connection with this Agreement. Service of process on any party hereto in any action arising out of or relating to this Agreement shall be effective if given in accordance
with the requirements for notice set forth in Section&nbsp;12(g), and shall be deemed effective and received as set forth in Section&nbsp;12(g). Nothing herein shall affect the right to serve process in any other manner permitted by law or shall
limit the right of either party to bring proceedings in the courts of any other jurisdiction. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(o) <U>Mutual Waiver of Jury Trial</U>.
Because disputes arising in connection with complex financial transactions are most quickly and economically resolved by an experienced and expert person and the parties wish applicable state and federal laws to apply (rather than arbitration
rules), the parties desire that their disputes be resolved by a judge applying such applicable laws. EACH OF THE COMPANY AND THE WARRANTHOLDER SPECIFICALLY WAIVES ANY RIGHT IT MAY HAVE TO TRIAL BY JURY OF ANY CAUSE OF ACTION, CLAIM, CROSS-CLAIM,
COUNTERCLAIM, THIRD PARTY CLAIM OR ANY OTHER CLAIM (COLLECTIVELY, &#147;CLAIMS&#148;) ASSERTED BY THE COMPANY AGAINST THE WARRANTHOLDER OR ITS ASSIGNEE OR BY THE WARRANTHOLDER OR ITS ASSIGNEE AGAINST THE COMPANY. This waiver extends to all such
Claims, including Claims that involve Persons other than the Company and the Warrantholder; Claims that arise out of or are in any way connected to the relationship between the Company and the Warrantholder; and any Claims for damages, breach of
contract, specific performance, or any equitable or legal relief of any kind, arising out of this Agreement. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(p) <U>Judicial
Reference</U>. If the waiver of jury trial set forth above is ineffective or unenforceable, the parties agree that all Claims shall be resolved by reference to a private judge sitting without a jury, pursuant to Code of Civil Procedure
Section&nbsp;638, before a mutually acceptable referee or, if the parties cannot agree, a referee selected by the Presiding Judge of Santa Clara County, California. Such proceeding shall be conducted in Santa Clara County, California, with Delaware
rules of evidence and discovery applicable to such proceeding. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">9 </P>

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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(q) <U>Prejudgment Relief</U>. In the event Claims are to be resolved by arbitration, either
party may seek from a court of competent jurisdiction identified in Section&nbsp;12(n), any prejudgment order, writ or other relief and have such prejudgment order, writ or other relief enforced to the fullest extent permitted by law notwithstanding
that all Claims are otherwise subject to resolution by judicial reference. </P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:8%; font-size:10pt; font-family:Times New Roman">(r) <U>Counterparts</U>. This Agreement and any amendments,
waivers, consents or supplements hereto may be executed in any number of counterparts, and by different parties hereto in separate counterparts, each of which when so delivered shall be deemed an original, but all of which counterparts shall
constitute but one and the same instrument. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">[Remainder of Page Intentionally Left Blank] </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">10 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be executed by its officers thereunto
duly authorized as of the Effective Date. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
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<TD WIDTH="4%"></TD>
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<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; text-indent:2.00em; font-size:10pt; font-family:Times New Roman">COMPANY:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3">X4 PHARMACEUTICALS, INC.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">/s/ Adam Mostafa</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Name:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Adam Mostafa</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Title:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Chief Financial Officer</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="4"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; text-indent:2.00em; font-size:10pt; font-family:Times New Roman">WARRANTHOLDER:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3">HERCULES CAPITAL, INC.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">/s/ Jennifer Choe</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Name:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Jennifer Choe</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Title:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Assistant General Counsel</TD></TR>
</TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">11 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">EXHIBIT I </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">NOTICE OF EXERCISE </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">To:</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">X4 PHARMACEUTICALS, INC. </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">(1)</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">The undersigned Warrantholder hereby elects to purchase [&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;]
shares of the Common Stock of X4 Pharmaceuticals, Inc., pursuant to the terms of the Warrant Agreement, dated as of March&nbsp;18, 2019 (the &#147;Agreement&#148;) between X4 Pharmaceuticals, Inc. and the Warrantholder, and [CASH PAYMENT: tenders
herewith payment of the Purchase Price in full, together with all applicable transfer taxes, if any.] [NET ISSUANCE: elects pursuant to Section&nbsp;3(a) of the Agreement to effect a Net Issuance.] </P></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">(2)</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">Please issue a certificate or certificates representing said shares of Common Stock in the name of the
undersigned or in such other name as is specified below. </P></TD></TR></TABLE> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


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<TD VALIGN="bottom" WIDTH="1%"></TD>
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<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3"> <P STYLE="line-height:3.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000">&nbsp;</P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">(Name)</P></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="4"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3"> <P STYLE="line-height:3.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000">&nbsp;</P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">(Address)</P></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="4"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">WARRANTHOLDER:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3">HERCULES CAPITAL, INC.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Name:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Title:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Date:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
</TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">12 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">EXHIBIT II </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">ACKNOWLEDGMENT OF EXERCISE </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The undersigned
[&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;], hereby acknowledges receipt of the &#147;Notice of Exercise&#148; from Hercules Capital, Inc., to purchase
[&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;] shares of the Common Stock of X4 Pharmaceuticals, Inc., pursuant to the terms of the Warrant Agreement by and between X4 Pharmaceuticals, Inc. and Hercules Capital, Inc. dated as of March&nbsp;18,
2019 (the &#147;Agreement&#148;), and further acknowledges that [&nbsp;&nbsp;&nbsp;&nbsp;] shares remain subject to purchase under the terms of the Agreement. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; text-indent:2.00em; font-size:10pt; font-family:Times New Roman">COMPANY:</P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3">X4 PHARMACEUTICALS, INC.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="13"></TD>
<TD HEIGHT="13" COLSPAN="2"></TD>
<TD HEIGHT="13" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Title:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Date:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
</TABLE>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">13 </P>

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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">EXHIBIT III </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">TRANSFER NOTICE </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">(To transfer or assign the
foregoing Agreement execute this form and supply required information. Do not use this form to purchase shares.) </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">FOR VALUE RECEIVED, the foregoing
Agreement and all rights evidenced thereby are hereby transferred and assigned to </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<P STYLE="line-height:8.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000;width:52%">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">(Please Print) </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">whose address is<U>
</U><U>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</U> </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P> <P STYLE="line-height:8.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000;width:52%">&nbsp;</P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Dated:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR></TABLE>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


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<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="14%"></TD>
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<TD WIDTH="36%"></TD></TR>
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<TD HEIGHT="8"></TD>
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<TD HEIGHT="8" COLSPAN="2"></TD></TR>

<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Holder&#146;s&nbsp;Signature:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
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<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Holder&#146;s Address:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Signature
Guaranteed:&nbsp;<U>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</U> </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">NOTE:&nbsp;The signature to this Transfer
Notice must correspond with the name as it appears on the face of the Agreement, without alteration or enlargement or any change whatever. Officers of corporations and those acting in a fiduciary or other representative capacity should file proper
evidence of authority to assign the foregoing Agreement. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">14 </P>

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<TYPE>EX-10.14
<SEQUENCE>4
<FILENAME>d726255dex1014.htm
<DESCRIPTION>EX-10.14
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<TITLE>EX-10.14</TITLE>
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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>Exhibit 10.14 </B></P>
<P STYLE="margin-top:24pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>FORM FOR ARSANIS, INC. 2017 EQUITY INCENTIVE PLAN </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>(MARCH 2019) </B></P> <P STYLE="margin-top:24pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">X4
PHARMACEUTICALS, INC. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><U>RESTRICTED STOCK AGREEMENT </U></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">X4 Pharmaceuticals, Inc. (the &#147;<U>Company</U>&#148;) has selected you to receive the following restricted stock award pursuant to its
2017 Equity Incentive Plan (the Arsanis, Inc. 2017 Equity Incentive Plan). The terms and conditions attached hereto are also a part hereof. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><U>Notice of Grant </U></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="49%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="48%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">
<P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Name of recipient (the &#147;<U>Recipient</U>&#148;):</P></TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-TOP:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Grant
Date:</P></TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Number of
shares of the restricted common stock awarded:</P></TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">Vesting
Start Date:</P></TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
</TABLE> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Vesting Schedule: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


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<TD WIDTH="49%"></TD>
<TD VALIGN="bottom" WIDTH="3%"></TD>
<TD WIDTH="47%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">[First Anniversary of Vesting Start Date]</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-TOP:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt">[25%]</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">[Last day of each month following the First Anniversary of the Vesting Start Date thereafter]</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt">[2.0833%]</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3" STYLE="BORDER-LEFT:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt; padding-right:2pt">All vesting is dependent on the Recipient remaining employed by the Company, as
provided herein.</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3" STYLE="BORDER-LEFT:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt; padding-right:2pt">
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">[Notwithstanding the foregoing, 100% of the unvested portion of the Restricted Shares shall vest upon the termination of the Recipient&#146;s employment by the
Company without Cause upon or at any time within 12&nbsp;months following a Change of Control.</P> <P STYLE="font-size:12pt; margin-top:0pt; margin-bottom:0pt">&nbsp;</P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">For purposes of this Agreement, a &#147;<U>Change of Control</U>&#148; shall mean the occurrence of any of the following events: (i)&nbsp;any
&#147;Person&#148; (as such term is used in Sections&nbsp;13(d) and 14(d) of the Exchange Act) becomes the &#147;Beneficial Owner&#148; (as defined in <FONT STYLE="white-space:nowrap">Rule&nbsp;13d-3</FONT> under the Exchange Act), directly or
indirectly, of securities of the Company representing fifty percent (50%) or more of the total voting power represented by the Company&#146;s then outstanding voting securities (excluding for this purpose any such voting securities held by the
Company, or any affiliate, parent or subsidiary of the Company, or by any employee benefit plan of the Company) pursuant to a transaction or a series of related transactions which the Board does not approve; or (ii)&nbsp;(A) A merger or
consolidation of the Company whether or not approved by the Board, other than a merger or consolidation which would result in the voting securities of the Company outstanding immediately prior thereto continuing to represent (either by remaining
outstanding or by being converted into voting securities of the surviving entity or the parent of such entity) at least fifty percent (50%) of the total voting power represented by the voting securities of the Company or such surviving entity or
parent of such entity, as the case may be, outstanding immediately after such merger or consolidation; or (B)&nbsp;the sale or disposition by the Company of all or substantially all of the Company&#146;s assets.</P>
<P STYLE="font-size:12pt; margin-top:0pt; margin-bottom:0pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">For purposes of this Agreement, if the Recipient is subject to an individual employment
agreement with the Company or eligible to participate in a Company severance plan or arrangement, in any case which agreement, plan or arrangement contains a definition of &#147;cause&#148; for termination of employment, &#147;<U>Cause</U>&#148;
shall have the meaning ascribed to such term in such agreement, plan or arrangement, otherwise, &#147;<U>Cause</U>&#148; shall mean, with respect to the Recipient (a)&nbsp;dishonesty with respect to the Company or any affiliate,
(b)&nbsp;insubordination, substantial malfeasance or <FONT STYLE="white-space:nowrap">non-feasance</FONT> of duty, (c)&nbsp;unauthorized disclosure of confidential information, (d)&nbsp;breach by the recipient of any provision of any employment,
consulting, advisory, nondisclosure, <FONT STYLE="white-space:nowrap">non-competition</FONT> or similar agreement between the Recipient and the Company or any affiliate, and (e)&nbsp;conduct substantially prejudicial to the business of the Company
or any affiliate, with the determination of the administrator of the Plan as to the existence of Cause will be conclusive on the Recipient and the Company. The Recipient&#146;s employment shall be considered to have been terminated for Cause if the
Company determines, within 30&nbsp;days after the Recipient&#146;s resignation, that termination for Cause was warranted.]</P></TD></TR>
</TABLE>
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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Please confirm your acceptance of this restricted stock award and of the terms and
conditions of this Agreement by signing a copy of this Agreement where indicated below. </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><DIV ALIGN="right">
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="40%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt">


<TR>
<TD WIDTH="6%"></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD WIDTH="92%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3">X4 PHARMACEUTICALS, INC.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Name of Officer</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Title:</TD></TR>
</TABLE></DIV> <P STYLE="font-size:24pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TR>
<TD WIDTH="100%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">Accepted and Agreed:</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000"> &nbsp;<P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:3pt">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom">Signature of Recipient</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000"> &nbsp;<P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:3pt">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom">Street Address</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000"> &nbsp;<P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:3pt">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom">City/State/Zip Code</TD></TR>
</TABLE>
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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">X4 PHARMACEUTICALS, INC. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">Restricted Stock Agreement </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><U>Incorporated Terms and Conditions </U></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The terms and conditions of the award of shares of restricted common stock of the Company (the &#147;<U>Restricted Shares</U>&#148;) made to
the Recipient, as set forth in the Notice of Grant that forms part of this agreement (the &#147;<U>Notice of Grant</U>&#148;), are as follows: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">1.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Issuance of Restricted Shares</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(a) The Restricted Shares are issued to the Recipient, effective as of the Grant Date set forth in the Notice of Grant, in consideration of
services rendered and to be rendered by the Recipient to the Company. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(b) The Restricted Shares will initially be issued by the Company
in book entry form only, in the name of the Recipient. Following the vesting of any Restricted Shares pursuant to Section&nbsp;2 below, the Company shall, if requested by the Recipient, issue and deliver to the Recipient a certificate representing
the vested Restricted Shares. The Recipient agrees that the Restricted Shares shall be subject to the forfeiture provisions set forth in Section&nbsp;3 of this Agreement and the restrictions on transfer set forth in Section&nbsp;4 of this Agreement.
</P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">2.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Vesting</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Unless otherwise provided in this Agreement in the Arsanis, Inc. 2017 Equity Incentive Plan (the &#147;<U>Plan</U>&#148;) or in another
agreement between the Recipient and the Company, the Restricted Shares shall vest in accordance with the vesting schedule set forth in the Notice of Grant. Any fractional number of Restricted Shares resulting from the application of the vesting
schedule shall be rounded down to the nearest whole number of Restricted Shares. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">3.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Forfeiture of Unvested Restricted Shares Upon Employment Termination</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">In the event that the Recipient ceases to be employed by the Company for any reason or no reason, with or without cause, all of the Restricted
Shares that are unvested as of the time of such employment termination shall be forfeited immediately and automatically to the Company, without the payment of any consideration to the Recipient, effective as of such termination of employment. The
Recipient shall have no further rights with respect to any Restricted Shares that are so forfeited. If the Recipient is employed by a subsidiary of the Company, any references in this Agreement to employment with the Company shall instead be deemed
to refer to employment with such subsidiary. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">4.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Restrictions on Transfer</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Except as set forth in the Plan, the Recipient shall not sell, assign, transfer, pledge, hypothecate or otherwise dispose of, by operation of
law or otherwise (collectively &#147;<U>transfer</U>&#148;) any Restricted Shares, or any interest therein, until such Restricted Shares have vested. The Company shall not be required (i)&nbsp;to transfer on its books any of the Restricted Shares
which have been transferred in violation of any of the provisions of this Agreement or the Plan or (ii)&nbsp;to treat as owner of such Restricted Shares or to pay dividends to any transferee to whom such Restricted Shares have been transferred in
violation of any of the provisions of this Agreement or the Plan. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">5.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Restrictive Legends</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The book entry account reflecting the issuance of the Restricted Shares in the name of the Recipient shall bear a legend or other notation upon
substantially the following terms: </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">&#147;These shares of stock are subject to forfeiture provisions and restrictions on transfer set
forth in a certain Restricted Stock Agreement between the corporation and the registered owner of these shares (or his or her predecessor in interest), and such Agreement is available for inspection without charge at the office of the Secretary of
the corporation.&#148; </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">1 </P>

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<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">6.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Rights as a Shareholder</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Except as otherwise provided in this Agreement, for so long as the Recipient is the registered owner of the Restricted Shares, the Recipient
shall have all rights as a shareholder with respect to the Restricted Shares, whether vested or unvested, including, without limitation, rights to vote the Restricted Shares and act in respect of the Restricted Shares at any meeting of shareholders;
provided that, as provided in the Plan, the payment of dividends on unvested Restricted Shares shall be deferred until the vesting of such shares. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">7.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Provisions of the Plan</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This Agreement is subject to the provisions of the Plan, a copy of which is furnished to the Recipient with this Agreement. </P>
<P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">8.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Tax Matters</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(a) <U>Acknowledgments; Section</U><U></U><U>&nbsp;83(b) Election</U>. The Recipient acknowledges that he or she is responsible for obtaining
the advice of the Recipient&#146;s own tax advisors with respect to the acquisition of the Restricted Shares and the Recipient is relying solely on such advisors and not on any statements or representations of the Company or any of its agents with
respect to the tax consequences relating to the Restricted Shares. The Recipient understands that the Recipient (and not the Company) shall be responsible for the Recipient&#146;s tax liability that may arise in connection with the acquisition,
vesting and/or disposition of the Restricted Shares. The Recipient acknowledges that he or she has been informed of the availability of making an election under Section&nbsp;83(b) of the Internal Revenue Code, as amended (a
&#147;<U>Section</U><U></U><U>&nbsp;83(b) Election</U>&#148;) with respect to the issuance of the Restricted Shares. The Recipient agrees to promptly deliver written notice to the Company in the event the Recipient makes a Section&nbsp;83(b)
Election with respect to the Restricted Shares. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(b) <U>Withholding</U>. The Recipient acknowledges and agrees that the Company has the
right to deduct from payments of any kind otherwise due to the Recipient any federal, state, local or other taxes of any kind required by law to be withheld with respect to the issuance or vesting of the Restricted Shares. </P>
<P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">9.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Miscellaneous</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(a) <U>No Right to Continued Employment</U>. The Recipient acknowledges and agrees that, notwithstanding the fact that the vesting of the
Restricted Shares is contingent upon his or her continued employment by the Company, this Agreement does not constitute an express or implied promise of continued employment or confer upon the Recipient any rights with respect to continued
employment by the Company. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(b) <U>Governing Law</U>. This Agreement shall be construed, interpreted and enforced in accordance with the
internal laws of the State of Delaware without regard to any applicable conflicts of laws provisions. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(c) <U>Recipient&#146;s
Acknowledgments</U>. The Recipient acknowledges that he or she has read this Agreement, has received and read the Plan, and understands the terms and conditions of this Agreement and the Plan. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">2 </P>

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<DESCRIPTION>EX-10.15
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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>Exhibit 10.15 </B></P>
<P STYLE="margin-top:24pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>FORM FOR ARSANIS, INC. 2017 EQUITY INCENTIVE PLAN </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>(MARCH 2019) </B></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">X4
PHARMACEUTICALS, INC. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><U><FONT STYLE="white-space:nowrap">NON-QUALIFIED</FONT> OPTION AGREEMENT (DIRECTOR GRANTS) </U></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">X4 Pharmaceuticals, Inc. (the &#147;<U>Company</U>&#148;) hereby grants the following stock option pursuant to its 2017 Equity Incentive Plan
(the Arsanis, Inc. 2017 Equity Incentive Plan). The terms and conditions attached hereto are also a part hereof. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><U>Notice of Grant
</U></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


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<TD WIDTH="48%"></TD></TR>


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<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Name of optionee (the &#147;<U>Participant</U>&#148;):</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-TOP:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Grant Date:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Number of shares of the Company&#146;s Common Stock subject to this option (&#147;<U>Shares</U>&#148;):</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Option exercise price per Share:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Number, if any, of Shares that vest immediately on the grant date:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Shares that are subject to vesting schedule:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Vesting Start Date:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Final Exercise Date:</P>
<P STYLE="font-size:12pt; margin-top:0pt; margin-bottom:1pt">&nbsp;</P></TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Vesting Schedule: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD WIDTH="48%"></TD></TR>


<TR STYLE="font-size:1px; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-TOP:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3" STYLE="BORDER-LEFT:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt; padding-right:2pt">All vesting is dependent on the Participant remaining an Eligible Participant,
as provided herein.</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3" STYLE="BORDER-LEFT:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt; padding-right:2pt">
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">[Notwithstanding the foregoing, 100% of the unvested portion of this option shall vest upon a Change of Control.</P>
<P STYLE="font-size:12pt; margin-top:0pt; margin-bottom:0pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">For purposes of this option, a &#147;<U>Change of Control</U>&#148; shall mean the
occurrence of any of the following events: (i)&nbsp;any &#147;Person&#148; (as such term is used in Sections 13(d) and 14(d) of the Exchange Act) becomes the &#147;Beneficial Owner&#148; (as defined in Rule
<FONT STYLE="white-space:nowrap">13d-3</FONT> under the Exchange Act), directly or indirectly, of securities of the Company representing fifty percent (50%) or more of the total voting power represented by the Company&#146;s then outstanding voting
securities (excluding for this purpose any such voting securities held by the Company, or any affiliate, parent or subsidiary of the Company, or by any employee benefit plan of the Company) pursuant to a transaction or a series of related
transactions which the Board does not approve; or (ii)&nbsp;(A) A merger or consolidation of the Company whether or not approved by the Board, other than a merger or consolidation which would result in the voting securities of the Company
outstanding immediately prior thereto continuing to represent (either by remaining outstanding or by being converted into voting securities of the surviving entity or the parent of such entity) at least fifty percent (50%) of the total voting power
represented by the voting securities of the Company or such surviving entity or parent of such entity, as the case may be, outstanding immediately after such merger or consolidation; or (B)&nbsp;the sale or disposition by the Company of all or
substantially all of the Company&#146;s assets.]</P></TD></TR>
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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This option satisfies in full all commitments that the Company has to the Participant with
respect to the issuance of stock, stock options or other equity securities. </P> <P STYLE="font-size:96pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD VALIGN="bottom">&nbsp;</TD>
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<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3">X4 PHARMACEUTICALS, INC.</TD></TR>
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<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">Signature of Participant</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Name of Officer</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
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<TD VALIGN="bottom">&nbsp;</TD>
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<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Title:</TD></TR>
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<TD HEIGHT="16" COLSPAN="2"></TD>
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<TR STYLE="font-size:1px; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
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<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">Street Address</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD></TR>
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<TD HEIGHT="16"></TD>
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<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">City/State/Zip Code</P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD></TR>
</TABLE>
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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">X4 PHARMACEUTICALS, INC. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><FONT STYLE="white-space:nowrap">Non-Qualified</FONT> Option Agreement </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><U>Incorporated Terms and Conditions </U></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">1.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Grant of Option</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This agreement evidences the grant by the Company, on the grant date (the &#147;<U>Grant Date</U>&#148;) set forth in the Notice of Grant that
forms part of this agreement (the &#147;<U>Notice of Grant</U>&#148;), to the Participant of an option to purchase, in whole or in part, on the terms provided herein and in the Arsanis, Inc. 2017 Equity Incentive Plan (the &#147;<U>Plan</U>&#148;),
the number of Shares set forth in the Notice of Grant of common stock, $0.001 par value per share, of the Company (&#147;<U>Common Stock</U>&#148;), at the exercise price per Share set forth in the Notice of Grant. Unless earlier terminated, this
option shall expire at 5:00 p.m., Eastern time, on the Final Exercise Date set forth in the Notice of Grant (the &#147;<U>Final Exercise Date</U>&#148;). </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">It is intended that the option evidenced by this agreement shall not be an incentive stock option as defined in Section&nbsp;422 of the
Internal Revenue Code of 1986, as amended, and any regulations promulgated thereunder (the &#147;<U>Code</U>&#148;). Except as otherwise indicated by the context, the term &#147;<U>Participant</U>&#148;, as used in this option, shall be deemed to
include any person who acquires the right to exercise this option validly under its terms. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">2.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Vesting Schedule</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This option will become exercisable (&#147;<U>vest</U>&#148;) in accordance with the vesting schedule set forth in the Notice of Grant. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The right of exercise shall be cumulative so that to the extent the option is not exercised in any period to the maximum extent permissible it
shall continue to be exercisable, in whole or in part, with respect to all Shares for which it is vested until the earlier of the Final Exercise Date or the termination of this option under Section&nbsp;3 hereof or the Plan. </P>
<P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">3.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Exercise of Option</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(a) <U>Form of Exercise</U>. Each election to exercise this option shall be in writing, in the form of the Stock Option Exercise Notice
attached as <U>Annex&nbsp;A</U>, signed by the Participant, and received by the Company at its principal office, accompanied by this agreement, or in such other form (which may be electronic) as is approved by the Company, together with payment in
full in the manner provided in the Plan. The Participant may purchase less than the number of shares covered hereby, provided that no partial exercise of this option may be for any fractional share. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(b) <U>Continuous Relationship with the Company Required</U>. Except as otherwise provided in this Section&nbsp;3, this option may not be
exercised unless the Participant, at the time he or she exercises this option, is, and has been at all times since the Grant Date, an employee, director or officer of, or consultant or advisor to, the Company or any other entity the employees,
officers, directors, consultants, or advisors of which are eligible to receive option grants under the Plan (an &#147;<U>Eligible Participant</U>&#148;). </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(c) <U>Termination of Relationship with the Company</U>. If the Participant ceases to be an Eligible Participant for any reason, then, except
as provided in paragraphs (d)&nbsp;and (e) below, the right to exercise this option shall terminate three months after such cessation (but in no event after the Final Exercise Date), <U>provided</U> <U>that</U> this option shall be exercisable only
to the extent that the Participant was entitled to exercise this option on the date of such cessation. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Notwithstanding the foregoing, if
the Participant, prior to the Final Exercise Date, violates the restrictive covenants (including, without limitation, the <FONT STYLE="white-space:nowrap">non-competition,</FONT> <FONT STYLE="white-space:nowrap">non-solicitation,</FONT> or
confidentiality provisions) of any employment contract, the <FONT STYLE="white-space:nowrap">Non-Competition,</FONT> <FONT STYLE="white-space:nowrap">Non-Solicitation,</FONT> Confidentiality and Assignment of Inventions agreement to which the
Participant is a party, if any, or any other agreement between the Participant and the Company, the right to exercise this option shall terminate immediately upon such violation. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">1 </P>

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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(d) <U>Exercise Period Upon Death or Disability</U>. If the Participant dies or becomes
disabled (within the meaning of Section&nbsp;22(e)(3) of the Code) prior to the Final Exercise Date while he or she is an Eligible Participant and the Company has not terminated such relationship for &#147;cause&#148; as specified in paragraph
(e)&nbsp;below, this option shall be exercisable, within the period of one year following the date of death or disability of the Participant, by the Participant (or in the case of death by an authorized transferee), <U>provided</U> <U>that </U>this
option shall be exercisable only to the extent that this option was exercisable by the Participant on the date of his or her death or disability, and further provided that this option shall not be exercisable after the Final Exercise Date. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(e) <U>Termination for Cause</U>. If, prior to the Final Exercise Date, the Participant&#146;s employment or other relationship with the
Company is terminated by the Company for Cause (as defined below), the right to exercise this option shall terminate immediately upon the effective date of such termination of employment or other relationship. If, prior to the Final Exercise Date,
the Participant is given notice by the Company of the termination of his or her employment or other relationship by the Company for Cause, and the effective date of such termination is subsequent to the date of delivery of such notice, the right to
exercise this option shall be suspended from the time of the delivery of such notice until the earlier of (i)&nbsp;such time as it is determined or otherwise agreed that the Participant&#146;s employment or other relationship shall not be terminated
for Cause as provided in such notice or (ii)&nbsp;the effective date of such termination (in which case the right to exercise this option shall, pursuant to the preceding sentence, terminate upon the effective date of such termination). If the
Participant is subject to an individual employment or other services agreement with the Company or eligible to participate in a Company severance plan or arrangement, in any case which agreement, plan or arrangement contains a definition of
&#147;cause&#148; for termination of employment or such other relationship, &#147;<U>Cause</U>&#148; shall have the meaning ascribed to such term in such agreement, plan or arrangement. Otherwise, &#147;<U>Cause</U>&#148; shall mean, with respect to
the Participant (a)&nbsp;dishonesty with respect to the Company or any affiliate, (b)&nbsp;insubordination, substantial malfeasance or <FONT STYLE="white-space:nowrap">non-feasance</FONT> of duty, (c)&nbsp;unauthorized disclosure of confidential
information, (d)&nbsp;breach by the Participant of any provision of any employment, consulting, advisory, nondisclosure, <FONT STYLE="white-space:nowrap">non-competition</FONT> or similar agreement between the Participant and the Company or any
affiliate, and (e)&nbsp;conduct substantially prejudicial to the business of the Company or any affiliate. The determination of the administrator of the Plan as to the existence of Cause will be conclusive on the Participant and the Company. The
Participant&#146;s employment or other relationship shall be considered to have been terminated for Cause if the Company determines, within 30 days after the Participant&#146;s resignation, that termination for Cause was warranted. </P>
<P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">4.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Withholding</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">No Shares will be issued pursuant to the exercise of this option unless and until the Participant pays to the Company, or makes provision
satisfactory to the Company for payment of, any federal, state or local withholding taxes required by law to be withheld in respect of this option. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">5.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Transfer Restrictions; Clawback</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(a) This option may not be sold, assigned, transferred, pledged or otherwise encumbered by the Participant, either voluntarily or by operation
of law, except by will or the laws of descent and distribution, and, during the lifetime of the Participant, this option shall be exercisable only by the Participant. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(b) In accepting this option, the Participant agrees to be bound by any clawback policy that the Company may adopt in the future. </P>
<P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">6.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Provisions of the Plan</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This option is subject to the provisions of the Plan (including the provisions relating to amendments to the Plan), a copy of which is
furnished to the Participant with this option. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">2 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><U>ANNEX&nbsp;A </U></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">X4 PHARMACEUTICALS, INC. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><U>Stock Option Exercise Notice </U></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">X4
Pharmaceuticals, Inc. </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">955&nbsp;Massachusetts Avenue, 4th&nbsp;Floor </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Cambridge, MA 02139 </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Dear Sir or Madam: </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">I, (the &#147;<U>Participant</U>&#148;), hereby irrevocably exercise the right to purchase ___________ shares of the Common Stock, $0.001 par value per share
(the &#147;<U>Shares</U>&#148;), of X4 Pharmaceuticals, Inc. (the &#147;<U>Company</U>&#148;) at $__________ per share pursuant to the Company&#146;s 2017 Equity Incentive Plan (the Arsanis, Inc. 2017 Equity Incentive Plan) and a stock option
agreement with the Company dated __________ (the &#147;<U>Option Agreement</U>&#148;). Enclosed herewith is a payment of $__________, the aggregate purchase price for the Shares. The certificate for the Shares should be registered in my name as it
appears below or, if so indicated below, jointly in my name and the name of the person designated below, with right of survivorship. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD VALIGN="top">Dated:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="top"><FONT STYLE="font-size:10pt">Signature</FONT></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">Print&nbsp;Name:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="24"></TD>
<TD HEIGHT="24" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">Address:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
</TABLE>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="40%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt">


<TR>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="99%"></TD></TR>


<TR STYLE="font-size:1pt">
<TD HEIGHT="24"></TD>
<TD HEIGHT="24" COLSPAN="2"></TD></TR>
<TR STYLE="font-size:1px; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom" STYLE=" BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000">&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Name and address of persons in whose name the Shares are to be jointly registered (if applicable): </P>
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<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="font-size:1px; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom" STYLE=" BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000">&nbsp;</TD></TR>
</TABLE>
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<DOCUMENT>
<TYPE>EX-10.16
<SEQUENCE>6
<FILENAME>d726255dex1016.htm
<DESCRIPTION>EX-10.16
<TEXT>
<HTML><HEAD>
<TITLE>EX-10.16</TITLE>
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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>Exhibit 10.16 </B></P>
<P STYLE="margin-top:24pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>FORM FOR ARSANIS, INC. 2017 EQUITY INCENTIVE PLAN </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>(MARCH 2019) </B></P> <P STYLE="margin-top:24pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">X4
PHARMACEUTICALS, INC. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><U><FONT STYLE="white-space:nowrap">NON-QUALIFIED</FONT> OPTION AGREEMENT </U></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">X4 Pharmaceuticals, Inc. (the &#147;<U>Company</U>&#148;) hereby grants the following stock option pursuant to its 2017 Equity Incentive Plan
(the Arsanis, Inc. 2017 Equity Incentive Plan). The terms and conditions attached hereto are also a part hereof. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><U>Notice of Grant
</U></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD WIDTH="48%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Name of optionee (the &#147;<U>Participant</U>&#148;):</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-TOP:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Grant Date:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Number of shares of the Company&#146;s Common</P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">Stock subject to this option (&#147;<U>Shares</U>&#148;):</P></TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Option exercise price per Share:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Number, if any, of Shares that vest immediately on the grant date:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Shares that are subject to vesting schedule:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Vesting Start Date:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Final Exercise Date:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">&nbsp;&nbsp;Vesting Schedule: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="49%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="48%"></TD></TR>


<TR STYLE="font-size:1px; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-TOP:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3" STYLE="BORDER-LEFT:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt; padding-right:2pt">All vesting is dependent on the Participant remaining an Eligible Participant as
provided herein.</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3" STYLE="BORDER-LEFT:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt; padding-right:2pt">
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">[Notwithstanding the foregoing, 100% of the unvested portion of this option shall vest upon the termination of the Participant&#146;s employment or other
relationship with the Company by the Company without Cause upon or at any time within 12 months following a Change of Control.</P> <P STYLE="font-size:12pt; margin-top:0pt; margin-bottom:0pt">&nbsp;</P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">For purposes of this option, a &#147;<U>Change of Control</U>&#148; shall mean the occurrence of any of the following events: (i)&nbsp;any &#147;Person&#148;
(as such term is used in Sections 13(d) and 14(d) of the Exchange Act) becomes the &#147;Beneficial Owner&#148; (as defined in Rule <FONT STYLE="white-space:nowrap">13d-3</FONT> under the Exchange Act), directly or indirectly, of securities of the
Company representing fifty percent (50%) or more of the total voting power represented by the Company&#146;s then outstanding voting securities (excluding for this purpose any such voting securities held by the Company, or any affiliate, parent or
subsidiary of the Company, or by any employee benefit plan of the Company) pursuant to a transaction or a series of related transactions which the Board does not approve; or (ii)&nbsp;(A) A merger or consolidation of the Company whether or not
approved by the Board, other than a merger or consolidation which would result in the voting securities of the Company outstanding immediately prior thereto continuing to represent (either by remaining outstanding or by being converted into voting
securities of the surviving entity or the parent of such entity) at least fifty percent (50%) of the total voting power represented by the voting securities of the Company or such surviving entity or parent of such entity, as the case may be,
outstanding immediately after such merger or consolidation; or (B)&nbsp;the sale or disposition by the Company of all or substantially all of the Company&#146;s assets.]</P>
<P STYLE="font-size:3pt; margin-top:0pt; margin-bottom:1pt">&nbsp;</P></TD></TR>
</TABLE>
</DIV></Center>


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<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">


<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This option satisfies in full all commitments that the Company has to the Participant with
respect to the issuance of stock, stock options or other equity securities. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="45%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="5%"></TD>
<TD VALIGN="bottom"></TD>
<TD WIDTH="2%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="45%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="3">X4 PHARMACEUTICALS, INC.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="32"></TD>
<TD HEIGHT="32" COLSPAN="2"></TD>
<TD HEIGHT="32" COLSPAN="2"></TD>
<TD HEIGHT="32" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom" STYLE="BORDER-BOTTOM:1px solid #000000"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">By:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom" STYLE="BORDER-BOTTOM:1px solid #000000"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom">Signature of Participant</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Name of Officer</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Title:</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="font-size:1px; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom" STYLE="BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">Street Address</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="font-size:1px; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">City/State/Zip Code</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD></TR>
</TABLE>
</DIV></Center>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">


<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">X4 PHARMACEUTICALS, INC. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><FONT STYLE="white-space:nowrap">Non-Qualified</FONT> Option Agreement </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><U>Incorporated Terms and Conditions </U></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">1.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Grant of Option</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This agreement evidences the grant by the Company, on the grant date (the &#147;<U>Grant Date</U>&#148;) set forth in the Notice of Grant that
forms part of this agreement (the &#147;<U>Notice of Grant</U>&#148;), to the Participant of an option to purchase, in whole or in part, on the terms provided herein and in the Arsanis, Inc. 2017 Equity Incentive Plan (the &#147;<U>Plan</U>&#148;),
the number of Shares set forth in the Notice of Grant of common stock, $0.001par value per share, of the Company (&#147;<U>Common Stock</U>&#148;), at the exercise price per Share set forth in the Notice of Grant. Unless earlier terminated, this
option shall expire at 5:00 p.m., Eastern time, on the Final Exercise Date set forth in the Notice of Grant (the &#147;<U>Final Exercise Date</U>&#148;). </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">It is intended that the option evidenced by this agreement shall not be an incentive stock option as defined in Section&nbsp;422 of the
Internal Revenue Code of 1986, as amended, and any regulations promulgated thereunder (the &#147;<U>Code</U>&#148;). Except as otherwise indicated by the context, the term &#147;<U>Participant</U>&#148;, as used in this option, shall be deemed to
include any person who acquires the right to exercise this option validly under its terms. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">2.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Vesting Schedule</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This option will become exercisable (&#147;<U>vest</U>&#148;) in accordance with the vesting schedule set forth in the Notice of Grant. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The right of exercise shall be cumulative so that to the extent the option is not exercised in any period to the maximum extent permissible it
shall continue to be exercisable, in whole or in part, with respect to all Shares for which it is vested until the earlier of the Final Exercise Date or the termination of this option under Section&nbsp;3 hereof or the Plan. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">3.&nbsp;&nbsp;&nbsp;&nbsp;<U>Exercise of Option</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(a) <U>Form of Exercise</U>. Each election to exercise this option shall be in writing, in the form of the Stock Option Exercise Notice
attached as <U>Annex A</U>, signed by the Participant, and received by the Company at its principal office, accompanied by this agreement, or in such other form (which may be electronic) as is approved by the Company, together with payment in full
in the manner provided in the Plan. The Participant may purchase less than the number of shares covered hereby, provided that no partial exercise of this option may be for any fractional share. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(b) <U>Continuous Relationship with the Company Required</U>. Except as otherwise provided in this Section&nbsp;3, this option may not be
exercised unless the Participant, at the time he or she exercises this option, is, and has been at all times since the Grant Date, an employee, director or officer of, or consultant or advisor to, the Company or any other entity the employees,
officers, directors, consultants, or advisors of which are eligible to receive option grants under the Plan (an &#147;<U>Eligible Participant</U>&#148;). </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(c) <U>Termination of Relationship with the Company</U>. If the Participant ceases to be an Eligible Participant for any reason, then, except
as provided in paragraphs (d)&nbsp;and (e) below, the right to exercise this option shall terminate three months after such cessation (but in no event after the Final Exercise Date), <U>provided</U> <U>that</U> this option shall be exercisable only
to the extent that the Participant was entitled to exercise this option on the date of such cessation. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Notwithstanding the foregoing, if
the Participant, prior to the Final Exercise Date, violates the restrictive covenants (including, without limitation, the <FONT STYLE="white-space:nowrap">non-competition,</FONT> <FONT STYLE="white-space:nowrap">non-solicitation,</FONT> or
confidentiality provisions) of any employment contract, the <FONT STYLE="white-space:nowrap">Non-Competition,</FONT> <FONT STYLE="white-space:nowrap">Non-Solicitation,</FONT> Confidentiality and Assignment of Inventions agreement to which the
Participant is a party, if any, or any other agreement between the Participant and the Company, the right to exercise this option shall terminate immediately upon such violation. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">1 </P>

</DIV></Center>


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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(d) <U>Exercise Period Upon Death or Disability</U>. If the Participant dies or becomes
disabled (within the meaning of Section&nbsp;22(e)(3) of the Code) prior to the Final Exercise Date while he or she is an Eligible Participant and the Company has not terminated such relationship for &#147;cause&#148; as specified in paragraph
(e)&nbsp;below, this option shall be exercisable, within the period of one year following the date of death or disability of the Participant, by the Participant (or in the case of death by an authorized transferee), <U>provided</U> <U>that </U>this
option shall be exercisable only to the extent that this option was exercisable by the Participant on the date of his or her death or disability, and further provided that this option shall not be exercisable after the Final Exercise Date. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(e) <U>Termination for Cause</U>. If, prior to the Final Exercise Date, the Participant&#146;s employment or other relationship with the
Company is terminated by the Company for Cause (as defined below), the right to exercise this option shall terminate immediately upon the effective date of such termination of employment or other relationship. If, prior to the Final Exercise Date,
the Participant is given notice by the Company of the termination of his or her employment or other relationship by the Company for Cause, and the effective date of such termination is subsequent to the date of delivery of such notice, the right to
exercise this option shall be suspended from the time of the delivery of such notice until the earlier of (i)&nbsp;such time as it is determined or otherwise agreed that the Participant&#146;s employment or other relationship shall not be terminated
for Cause as provided in such notice or (ii)&nbsp;the effective date of such termination (in which case the right to exercise this option shall, pursuant to the preceding sentence, terminate upon the effective date of such termination). If the
Participant is subject to an individual employment or other services agreement with the Company or eligible to participate in a Company severance plan or arrangement, in any case which agreement, plan or arrangement contains a definition of
&#147;cause&#148; for termination of employment or such other relationship, &#147;<U>Cause</U>&#148; shall have the meaning ascribed to such term in such agreement, plan or arrangement. Otherwise, &#147;<U>Cause</U>&#148; shall mean, with respect to
the Participant (a)&nbsp;dishonesty with respect to the Company or any affiliate, (b)&nbsp;insubordination, substantial malfeasance or <FONT STYLE="white-space:nowrap">non-feasance</FONT> of duty, (c)&nbsp;unauthorized disclosure of confidential
information, (d)&nbsp;breach by the Participant of any provision of any employment, consulting, advisory, nondisclosure, <FONT STYLE="white-space:nowrap">non-competition</FONT> or similar agreement between the Participant and the Company or any
affiliate, and (e)&nbsp;conduct substantially prejudicial to the business of the Company or any affiliate. The determination of the administrator of the Plan as to the existence of Cause will be conclusive on the Participant and the Company. The
Participant&#146;s employment or other relationship shall be considered to have been terminated for Cause if the Company determines, within 30 days after the Participant&#146;s resignation, that termination for Cause was warranted. </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">4.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Withholding</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">No Shares will be issued pursuant to the exercise of this option unless and until the Participant pays to the Company, or makes provision
satisfactory to the Company for payment of, any federal, state or local withholding taxes required by law to be withheld in respect of this option. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">5.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Transfer Restrictions; Clawback</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(a) This option may not be sold, assigned, transferred, pledged or otherwise encumbered by the Participant, either voluntarily or by operation
of law, except by will or the laws of descent and distribution, and, during the lifetime of the Participant, this option shall be exercisable only by the Participant. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(b) In accepting this option, the Participant agrees to be bound by any clawback policy that the Company may adopt in the future. </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">6.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Provisions of the Plan</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This option is subject to the provisions of the Plan (including the provisions relating to amendments to the Plan), a copy of which is
furnished to the Participant with this option. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">2 </P>

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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><U>ANNEX A </U></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">X4 PHARMACEUTICALS, INC. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><U>Stock Option Exercise Notice </U></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">X4
Pharmaceuticals, Inc. </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">955 Massachusetts Avenue, 4th Floor </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Cambridge, MA 02139 </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Dear Sir or Madam: </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">I, (the &#147;<U>Participant</U>&#148;), hereby irrevocably exercise the right to purchase
<U>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</U> shares of the Common Stock, $0.001 par value per share (the
&#147;<U>Shares</U>&#148;), of X4 Pharmaceuticals, Inc. (the &#147;<U>Company</U>&#148;) at $<U>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</U> per
share pursuant to the Company&#146;s 2017 Equity Incentive Plan (the Arsanis, Inc. 2017 Equity Incentive Plan) and a stock option agreement with the Company dated
<U>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</U> (the &#147;<U>Option Agreement</U>&#148;). Enclosed herewith is a payment
of $<U>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</U>, the aggregate purchase price for the Shares. The certificate for the Shares should be
registered in my name as it appears below or, if so indicated below, jointly in my name and the name of the person designated below, with right of survivorship. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD VALIGN="top">Dated:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
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<TD VALIGN="top" COLSPAN="3"><FONT STYLE="font-size:10pt">Signature</FONT></TD></TR>
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<TD VALIGN="top" COLSPAN="3"><FONT STYLE="font-size:10pt">Print Name:</FONT></TD></TR>
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<TD HEIGHT="16" COLSPAN="2"></TD></TR>
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<TD VALIGN="top">Address:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
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<TD HEIGHT="16" COLSPAN="3"></TD></TR>
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<TD COLSPAN="3" VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000">&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Name and address of persons in whose name the Shares are to be jointly registered (if applicable): </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TYPE>EX-10.17
<SEQUENCE>7
<FILENAME>d726255dex1017.htm
<DESCRIPTION>EX-10.17
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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>Exhibit 10.17 </B></P>
<P STYLE="margin-top:24pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>FORM FOR ARSANIS, INC. 2017 EQUITY INCENTIVE PLAN </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>(MARCH 2019) </B></P> <P STYLE="margin-top:24pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">X4
PHARMACEUTICALS, INC. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><U>INCENTIVE STOCK OPTION AGREEMENT </U></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">X4 Pharmaceuticals, Inc. (the &#147;<U>Company</U>&#148;) hereby grants the following stock option pursuant to its 2017 Equity Incentive Plan
(the Arsanis, Inc. 2017 Equity Incentive Plan). The terms and conditions attached hereto are also a part hereof. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><U>Notice of Grant
</U></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


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<TD WIDTH="49%"></TD>
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<TD WIDTH="48%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Name of optionee (the &#147;<U>Participant</U>&#148;):</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-TOP:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Grant Date:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Number of shares of the Company&#146;s Common</P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">Stock subject to this option (&#147;<U>Shares</U>&#148;):</P></TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Option exercise price per
Share:<SUP STYLE="font-size:85%; vertical-align:top">1</SUP><SUP STYLE="font-size:85%; vertical-align:top">/</SUP></TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Number, if any, of Shares that vest immediately on the grant date:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Shares that are subject to vesting schedule:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Vesting Start Date:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">Final Exercise Date: <SUP STYLE="font-size:85%; vertical-align:top">2</SUP><SUP STYLE="font-size:85%; vertical-align:top">/</SUP></TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">&nbsp;&nbsp;Vesting Schedule: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="49%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="48%"></TD></TR>


<TR STYLE="font-size:1px; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-TOP:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-TOP:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt">&nbsp;</TD></TR>
<TR STYLE="font-size:1px; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt">&nbsp;</TD>
<TD VALIGN="bottom" STYLE=" BORDER-LEFT:1px solid #000000; BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-right:2pt">&nbsp;</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3" STYLE="BORDER-LEFT:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt; padding-right:2pt">All vesting is dependent on the Participant remaining an Eligible Participant as
provided herein.</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3" STYLE="BORDER-LEFT:1px solid #000000; BORDER-RIGHT:1px solid #000000; BORDER-BOTTOM:1px solid #000000; padding-left:8pt; padding-right:2pt">
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">[Notwithstanding the foregoing, 100% of the unvested portion of this option shall vest upon the termination of the Participant&#146;s employment by the Company
without Cause upon or at any time within 12 months following a Change of Control.</P> <P STYLE="font-size:12pt; margin-top:0pt; margin-bottom:0pt">&nbsp;</P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">For purposes of this option, a &#147;<U>Change of Control</U>&#148; shall mean the occurrence of any of the following events: (i)&nbsp;any &#147;Person&#148;
(as such term is used in Sections 13(d) and 14(d) of the Exchange Act) becomes the &#147;Beneficial Owner&#148; (as defined in Rule <FONT STYLE="white-space:nowrap">13d-3</FONT> under the Exchange Act), directly or indirectly, of securities of the
Company representing fifty percent (50%) or more of the total voting power represented by the Company&#146;s then outstanding voting securities (excluding for this purpose any such voting securities held by the Company, or any affiliate, parent or
subsidiary of the Company, or by any employee benefit plan of the Company) pursuant to a transaction or a series of related transactions which the Board does not approve; or (ii)&nbsp;(A) A merger or consolidation of the Company whether or not
approved by the Board, other than a merger or consolidation which would result in the voting securities of the Company outstanding immediately prior thereto continuing to represent (either by remaining outstanding or by being converted into voting
securities of the surviving entity or the parent of such entity) at least fifty percent (50%) of the total voting power represented by the voting securities of the Company or such surviving entity or parent of such entity, as the case may be,
outstanding immediately after such merger or consolidation; or (B)&nbsp;the sale or disposition by the Company of all or substantially all of the Company&#146;s assets.]</P>
<P STYLE="font-size:3pt; margin-top:0pt; margin-bottom:1pt">&nbsp;</P></TD></TR>
</TABLE> <P STYLE="line-height:8.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000;width:10%">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><SUP STYLE="font-size:85%; vertical-align:top">1/</SUP>&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">This must be at least 100% of the Grant Date Fair Market Value (as defined in the Plan) of the Common Stock on
the date of grant (or 110% in the case of a Participant that owns more than 10% of the total combined voting power of all classes of stock of the Company or its parent or subsidiary (a &#147;<U>10% Shareholder</U>&#148;)) for the option to 2 qualify
as an incentive stock option (an &#147;ISO&#148;) under Section&nbsp;422 of the Code. </P></TD></TR></TABLE>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><SUP STYLE="font-size:85%; vertical-align:top">2/</SUP>&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left">The Final Exercise Date must be no more than 10 years (5 years in the case of a 10% Shareholder) from the date
of grant for the option to qualify as an ISO. The correct approach to calculate the final exercise date is to use the day immediately prior to the date ten years out from the date of the stock option award grant (5 years in the case of a 10%
stockholder). For example, an award granted to someone on August&nbsp;1, 2017 would expire on July&nbsp;31, 2027 (not on August&nbsp;1, 2027). </P></TD></TR></TABLE>
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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This option satisfies in full all commitments that the Company has to the Participant with
respect to the issuance of stock, stock options or other equity securities. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


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<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="5%"></TD>
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<TD WIDTH="2%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="45%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="3">X4 PHARMACEUTICALS, INC.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="32"></TD>
<TD HEIGHT="32" COLSPAN="2"></TD>
<TD HEIGHT="32" COLSPAN="2"></TD>
<TD HEIGHT="32" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom" STYLE="BORDER-BOTTOM:1px solid #000000"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">By:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="bottom" STYLE="BORDER-BOTTOM:1px solid #000000"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom">Signature of Participant</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Name of Officer</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Title:</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
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<TD VALIGN="top">City/State/Zip Code</TD>
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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">X4 PHARMACEUTICALS, INC. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">Incentive Stock Option Agreement </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><U>Incorporated Terms and Conditions </U></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">1.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Grant of Option</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This agreement evidences the grant by the Company, on the grant date (the &#147;<U>Grant Date</U>&#148;) set forth in the Notice of Grant that
forms part of this agreement (the &#147;<U>Notice of Grant</U>&#148;), to the Participant of an option to purchase, in whole or in part, on the terms provided herein and in the Arsanis, Inc. 2017 Equity Incentive Plan (the &#147;<U>Plan</U>&#148;),
the number of Shares set forth in the Notice of Grant of common stock, $0.001 par value per share, of the Company (&#147;<U>Common Stock</U>&#148;), at the exercise price per Share set forth in the Notice of Grant. Unless earlier terminated, this
option shall expire at 5:00 p.m., Eastern time, on the Final Exercise Date set forth in the Notice of Grant (the &#147;<U>Final Exercise Date</U>&#148;). </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">It is intended that the option evidenced by this agreement shall be an incentive stock option as defined in Section&nbsp;422 of the Internal
Revenue Code of 1986, as amended, and any regulations promulgated thereunder (the &#147;<U>Code</U>&#148;) to the maximum extent permitted by law. Except as otherwise indicated by the context, the term &#147;<U>Participant</U>&#148;, as used in this
option, shall be deemed to include any person who acquires the right to exercise this option validly under its terms. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">2.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Vesting Schedule</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This option will become exercisable (&#147;<U>vest</U>&#148;) in accordance with the vesting schedule set forth in the Notice of Grant. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The right of exercise shall be cumulative so that to the extent the option is not exercised in any period to the maximum extent permissible it
shall continue to be exercisable, in whole or in part, with respect to all Shares for which it is vested until the earlier of the Final Exercise Date or the termination of this option under Section&nbsp;3 hereof or the Plan. </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">3.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Exercise of Option</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(a) <U>Form of Exercise</U>. Each election to exercise this option shall be in writing, in the form of the Stock Option Exercise Notice
attached as <U>Annex A</U>, signed by the Participant, and received by the Company at its principal office, accompanied by this agreement, or in such other form (which may be electronic) as is approved by the Company, together with payment in full
in the manner provided in the Plan. The Participant may purchase less than the number of shares covered hereby, provided that no partial exercise of this option may be for any fractional share. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(b) <U>Continuous Relationship with the Company Required</U>. Except as otherwise provided in this Section&nbsp;3, this option may not be
exercised unless the Participant, at the time he or she exercises this option, is, and has been at all times since the Grant Date, an employee, director or officer of, or consultant or advisor to, the Company or any other entity the employees,
officers, directors, consultants, or advisors of which are eligible to receive option grants under the Plan (an &#147;<U>Eligible Participant</U>&#148;). </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(c) <U>Termination of Relationship with the Company</U>. If the Participant ceases to be an Eligible Participant for any reason, then, except
as provided in paragraphs (d)&nbsp;and (e) below, the right to exercise this option shall terminate three months after such cessation (but in no event after the Final Exercise Date), <U>provided</U> <U>that</U> this option shall be exercisable only
to the extent that the Participant was entitled to exercise this option on the date of such cessation. Notwithstanding the foregoing, if the Participant, prior to the Final Exercise Date, violates the restrictive covenants (including, without
limitation, the <FONT STYLE="white-space:nowrap">non-competition,</FONT> <FONT STYLE="white-space:nowrap">non-solicitation,</FONT> or confidentiality provisions) of any employment contract, the
<FONT STYLE="white-space:nowrap">Non-Competition,</FONT> <FONT STYLE="white-space:nowrap">Non-Solicitation,</FONT> Confidentiality and Assignment of Inventions agreement to which the Participant is a party, if any, or any other agreement between the
Participant and the Company, the right to exercise this option shall terminate immediately upon such violation. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">1 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(d) <U>Exercise Period Upon Death or Disability</U>. If the Participant dies or becomes
disabled (within the meaning of Section&nbsp;22(e)(3) of the Code) prior to the Final Exercise Date while he or she is an Eligible Participant and the Company has not terminated such relationship for &#147;cause&#148; as specified in paragraph
(e)&nbsp;below, this option shall be exercisable, within the period of one year following the date of death or disability of the Participant, by the Participant (or in the case of death by an authorized transferee), <U>provided</U> <U>that</U> this
option shall be exercisable only to the extent that this option was exercisable by the Participant on the date of his or her death or disability, and further provided that this option shall not be exercisable after the Final Exercise Date. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(e) <U>Termination for Cause</U>. If, prior to the Final Exercise Date, the Participant&#146;s employment is terminated by the Company for
Cause (as defined in below), the right to exercise this option shall terminate immediately upon the effective date of such termination of employment. If, prior to the Final Exercise Date, the Participant is given notice by the Company of the
termination of his or her employment by the Company for Cause, and the effective date of such employment termination is subsequent to the date of delivery of such notice, the right to exercise this option shall be suspended from the time of the
delivery of such notice until the earlier of (i)&nbsp;such time as it is determined or otherwise agreed that the Participant&#146;s employment shall not be terminated for Cause as provided in such notice or (ii)&nbsp;the effective date of such
termination of employment (in which case the right to exercise this option shall, pursuant to the preceding sentence, terminate upon the effective date of such termination of employment). If the Participant is subject to an individual employment
agreement with the Company or eligible to participate in a Company severance plan or arrangement, in any case which agreement, plan or arrangement contains a definition of &#147;cause&#148; for termination of employment, &#147;<U>Cause</U>&#148;
shall have the meaning ascribed to such term in such agreement, plan or arrangement. Otherwise, &#147;<U>Cause</U>&#148; shall mean, with respect to the Participant (a)&nbsp;dishonesty with respect to the Company or any affiliate,
(b)&nbsp;insubordination, substantial malfeasance or <FONT STYLE="white-space:nowrap">non-feasance</FONT> of duty, (c)&nbsp;unauthorized disclosure of confidential information, (d)&nbsp;breach by the Participant of any provision of any employment,
consulting, advisory, nondisclosure, <FONT STYLE="white-space:nowrap">non-competition</FONT> or similar agreement between the Participant and the Company or any affiliate, and (e)&nbsp;conduct substantially prejudicial to the business of the Company
or any affiliate. The determination of the administrator of the Plan as to the existence of Cause will be conclusive on the Participant and the Company. The Participant&#146;s employment shall be considered to have been terminated for Cause if the
Company determines, within 30 days after the Participant&#146;s resignation, that termination for Cause was warranted. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">4.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Tax Matters</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(a) <U>Withholding</U>. No Shares will be issued pursuant to the exercise of this option unless and until the Participant pays to the Company,
or makes provision satisfactory to the Company for payment of, any federal, state or local withholding taxes required by law to be withheld in respect of this option. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(b) <U>Disqualifying Disposition</U>. If the Participant disposes of Shares acquired upon exercise of this option within two years from the
Grant Date or one year after such Shares were acquired pursuant to exercise of this option, the Participant shall notify the Company in writing of such disposition. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">5.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Transfer Restrictions; Clawback</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(a) This option may not be sold, assigned, transferred, pledged or otherwise encumbered by the Participant, either voluntarily or by operation
of law, except by will or the laws of descent and distribution, and, during the lifetime of the Participant, this option shall be exercisable only by the Participant. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(b) In accepting this option, the Participant agrees to be bound by any clawback policy that the Company may adopt in the future. </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">6.</TD>
<TD ALIGN="left" VALIGN="top"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman; " ALIGN="left"><U>Provisions of the Plan</U>. </P></TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This option is subject to the provisions of the Plan (including the provisions relating to amendments to the Plan), a copy of which is
furnished to the Participant with this option. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">2 </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><U>ANNEX A </U></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">X4 PHARMACEUTICALS, INC. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><U>Stock Option Exercise Notice </U></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">X4
Pharmaceuticals, Inc. </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">955 Massachusetts Avenue, 4th Floor </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Cambridge, MA 02139 </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Dear Sir or Madam: </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">I, (the &#147;<U>Participant</U>&#148;), hereby irrevocably exercise the right to purchase
<U>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</U> shares of the Common Stock, $0.001 par value per share (the
&#147;<U>Shares</U>&#148;), of X4 Pharmaceuticals, Inc. (the &#147;<U>Company</U>&#148;) at
$<U>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</U> per share pursuant to the Company&#146;s 2017 Equity Incentive Plan (the
Arsanis, Inc. 2017 Equity Incentive Plan) and a stock option agreement with the Company dated
<U>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</U> (the &#147;<U>Option Agreement</U>&#148;). Enclosed herewith is a payment
of $<U>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</U>, the aggregate purchase price for the Shares. The certificate for the
Shares should be registered in my name as it appears below or, if so indicated below, jointly in my name and the name of the person designated below, with right of survivorship. </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD VALIGN="top">Dated:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
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<TD VALIGN="top" COLSPAN="3"><FONT STYLE="font-size:10pt">Signature</FONT></TD></TR>
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<TD VALIGN="top" COLSPAN="3"><FONT STYLE="font-size:10pt">Print Name:</FONT></TD></TR>
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<TD HEIGHT="16" COLSPAN="2"></TD></TR>
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<TD VALIGN="top">Address:</TD>
<TD VALIGN="bottom" STYLE=" BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000"><FONT SIZE="1">&nbsp;</FONT></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16" COLSPAN="3"></TD></TR>
<TR STYLE="font-size:1px; font-family:Times New Roman; font-size:10pt">
<TD COLSPAN="3" VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000">&nbsp;</TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Name and address of persons in whose name the Shares are to be jointly registered (if applicable): </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TYPE>EX-31.1
<SEQUENCE>8
<FILENAME>d726255dex311.htm
<DESCRIPTION>EX-31.1
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<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>Exhibit 31.1 </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">CERTIFICATIONS UNDER SECTION 302 </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">I, Paula
Ragan, Ph.D., certify that: </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">1. I have reviewed this quarterly report on Form <FONT STYLE="white-space:nowrap">10-Q</FONT> of X4
Pharmaceuticals, Inc.; </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a
material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report; </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material
respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report; </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">4. The registrant&#146;s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures
(as defined in Exchange Act Rules <FONT STYLE="white-space:nowrap">13a-15(e)</FONT> and <FONT STYLE="white-space:nowrap">15d-15(e))</FONT> and internal control over financial reporting (as defined in Exchange Act Rules
<FONT STYLE="white-space:nowrap">13a-15(f)</FONT> and <FONT STYLE="white-space:nowrap">15d-15(f))</FONT> for the registrant and have: </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">a)
Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is
made known to us by others within those entities, particularly during the period in which this report is being prepared; </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">b) Designed such
internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of
financial statements for external purposes in accordance with generally accepted accounting principles; </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">c) Evaluated the effectiveness of
the registrant&#146;s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and
</P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">d) Disclosed in this report any change in the registrant&#146;s internal control over financial reporting that occurred during the
registrant&#146;s most recent fiscal quarter (the registrant&#146;s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant&#146;s internal control over
financial reporting; and </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">5. The registrant&#146;s other certifying officer(s) and I have disclosed, based on our most recent evaluation
of internal control over financial reporting, to the registrant&#146;s auditors and the audit committee of the registrant&#146;s board of directors (or persons performing the equivalent functions): </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are
reasonably likely to adversely affect the registrant&#146;s ability to record, process, summarize and report financial information; and </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant&#146;s
internal control over financial reporting. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Date: May&nbsp;15, 2019 </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="40%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt">


<TR>
<TD WIDTH="100%"></TD></TR>


<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000">/s/ Paula Ragan, Ph.D.</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom">Paula Ragan, Ph.D.</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">President, Chief Executive Officer and Secretary</P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">(principal executive officer)</P></TD></TR>
</TABLE>
</DIV></Center>

</BODY></HTML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-31.2
<SEQUENCE>9
<FILENAME>d726255dex312.htm
<DESCRIPTION>EX-31.2
<TEXT>
<HTML><HEAD>
<TITLE>EX-31.2</TITLE>
</HEAD>
 <BODY BGCOLOR="WHITE">


<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>Exhibit 31.2 </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">CERTIFICATIONS UNDER SECTION 302 </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">I, Adam S.
Mostafa, certify that: </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">1. I have reviewed this quarterly report on Form <FONT STYLE="white-space:nowrap">10-Q</FONT> of X4
Pharmaceuticals, Inc.; </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a
material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report; </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material
respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report; </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">4. The registrant&#146;s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures
(as defined in Exchange Act Rules <FONT STYLE="white-space:nowrap">13a-15(e)</FONT> and <FONT STYLE="white-space:nowrap">15d-15(e))</FONT> and internal control over financial reporting (as defined in Exchange Act Rules
<FONT STYLE="white-space:nowrap">13a-15(f)</FONT> and <FONT STYLE="white-space:nowrap">15d-15(f))</FONT> for the registrant and have: </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">a)
Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is
made known to us by others within those entities, particularly during the period in which this report is being prepared; </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">b) Designed such
internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of
financial statements for external purposes in accordance with generally accepted accounting principles; </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">c) Evaluated the effectiveness of
the registrant&#146;s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and
</P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">d) Disclosed in this report any change in the registrant&#146;s internal control over financial reporting that occurred during the
registrant&#146;s most recent fiscal quarter (the registrant&#146;s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant&#146;s internal control over
financial reporting; and </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">5. The registrant&#146;s other certifying officer(s) and I have disclosed, based on our most recent evaluation
of internal control over financial reporting, to the registrant&#146;s auditors and the audit committee of the registrant&#146;s board of directors (or persons performing the equivalent functions): </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are
reasonably likely to adversely affect the registrant&#146;s ability to record, process, summarize and report financial information; and </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant&#146;s
internal control over financial reporting. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Date: May&nbsp;15, 2019 </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="40%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt">


<TR>
<TD WIDTH="100%"></TD></TR>


<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000">/s/ Adam S. Mostafa</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom">Adam S. Mostafa</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="bottom"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Chief Financial Officer and Treasurer</P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">(principal financial officer and principal accounting officer)</P></TD></TR>
</TABLE>
</DIV></Center>

</BODY></HTML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-32.1
<SEQUENCE>10
<FILENAME>d726255dex321.htm
<DESCRIPTION>EX-32.1
<TEXT>
<HTML><HEAD>
<TITLE>EX-32.1</TITLE>
</HEAD>
 <BODY BGCOLOR="WHITE">


<Center><DIV STYLE="width:8.5in" align="left">
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>Exhibit 32.1 </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">CERTIFICATIONS UNDER SECTION 906 </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Pursuant to section 906 of the Sarbanes-Oxley Act of 2002 (subsections (a)&nbsp;and (b)&nbsp;of section 1350, chapter 63 of title 18, United
States Code), each of the undersigned officers of X4 Pharmaceuticals, Inc., a Delaware corporation (the &#147;Company&#148;), does hereby certify, to such officer&#146;s knowledge, that: </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Quarterly Report for the quarter ended March&nbsp;31, 2019 (the &#147;Form <FONT STYLE="white-space:nowrap">10-Q&#148;)</FONT> of the
Company fully complies with the requirements of Section&nbsp;13(a) or 15(d) of the Securities Exchange Act of 1934, as amended, and the information contained in the Form <FONT STYLE="white-space:nowrap">10-Q</FONT> fairly presents, in all material
respects, the financial condition and results of operations of the Company. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt">


<TR>
<TD WIDTH="47%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="4%"></TD>
<TD VALIGN="bottom"></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="46%"></TD></TR>


<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Dated:&nbsp;May 15, 2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom" STYLE=" BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000">/s/ Paula Ragan, Ph.D.</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Paula Ragan, Ph.D.</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">President, Chief Executive Officer and Secretary</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">(principal executive officer)</TD></TR>
</TABLE> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt">


<TR>
<TD WIDTH="47%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="4%"></TD>
<TD VALIGN="bottom"></TD>
<TD></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="46%"></TD></TR>


<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Dated:&nbsp;May 15, 2019</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom" STYLE=" BORDER-BOTTOM:1px solid #000000">&nbsp;</TD>
<TD VALIGN="top" STYLE="BORDER-BOTTOM:1px solid #000000">/s/ Adam S. Mostafa</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top">Adam S. Mostafa</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Chief Financial Officer and Treasurer</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">(principal financial officer and principal accounting officer)</TD></TR>
</TABLE>
</DIV></Center>

</BODY></HTML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-101.INS
<SEQUENCE>11
<FILENAME>xfor-20190331.xml
<DESCRIPTION>XBRL INSTANCE DOCUMENT
<TEXT>
<XBRL>
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  <xfor:AgreementCommencementDate contextRef="eol_PE837744--1910-Q0004_STD_1_20190313_0_3073336x3532984" id="id_13073811_6E98D47D-081E-4E76-B806-E13B294BDA8C_1001_1">2019-03-01</xfor:AgreementCommencementDate>
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  <us-gaap:DebtInstrumentBasisSpreadOnVariableRate1 contextRef="eol_PE837744--1910-Q0004_STD_31_20161031_0_3066061x3566848_3078512x3075282" decimals="3" id="id_13073811_C7D16AE8-5583-4D8D-9279-281A030F52F7_2002_2" unitRef="pure">0.035</us-gaap:DebtInstrumentBasisSpreadOnVariableRate1>
  <xfor:CommonStockReservedForIssuanceDescription contextRef="eol_PE837744--1910-Q0004_STD_31_20170131_0_3076363x3384951" id="id_13073811_8C6C6674-E7F1-40B5-B2C5-5A61500530E0_1001_0">The number of shares of common stock reserved for issuance under  this plan will automatically increase on January 1 of each year, through  January 1, 2027, in an amount equal to the lowest of 1,025,490 shares of the  Company's common stock, 4% of the number of shares of the Company's common stock  outstanding on January 1 of each year and an amount determined by the Company's  board of directors.</xfor:CommonStockReservedForIssuanceDescription>
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 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;&lt;b&gt;1.&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;&lt;b&gt;Nature of the Business and Basis of
 Presentation&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 X4 Pharmaceuticals, Inc. (formerly Arsanis, Inc.), together with
 its subsidiaries (the &amp;#x201C;Company&amp;#x201D;), is a clinical-stage
 biotechnology research and development company focused on the
 development of novel therapeutics for the treatment of rare
 diseases. The Company is headquartered in Cambridge,
 Massachusetts.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company is subject to risks and uncertainties common to
 early-stage companies in the biotechnology industry, including, but
 not limited to, development by competitors of new technological
 innovations, dependence on key personnel, protection of proprietary
 technology, compliance with governmental regulations and the
 ability to secure additional capital to fund operations. Drug
 candidates currently under development will require extensive
 preclinical and clinical testing and regulatory approval prior to
 commercialization. These efforts require significant amounts of
 additional capital, adequate personnel, and infrastructure and
 extensive compliance-reporting capabilities. Even if the
 Company&amp;#x2019;s drug development efforts are successful, it is
 uncertain when, if ever, the Company will realize significant
 revenue from product sales.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The accompanying condensed consolidated financial statements have
 been prepared in accordance with accounting principles generally
 accepted in the United States of America (&amp;#x201C;GAAP&amp;#x201D;) and
 include the accounts of the Company and its wholly owned
 subsidiaries. All intercompany accounts and transactions have been
 eliminated in consolidation.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Merger with Arsanis&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 On November&amp;#xA0;26, 2018, Arsanis, Inc., a publicly held Delaware
 corporation (&amp;#x201C;Arsanis&amp;#x201D;), Artemis AC Corp., a Delaware
 corporation and a wholly owned subsidiary of Arsanis (&amp;#x201C;Merger
 Sub&amp;#x201D;), and X4 Therapeutics, Inc. (&amp;#x201C;X4&amp;#x201D;) entered
 into an Agreement and Plan of Merger, as amended on
 December&amp;#xA0;20, 2018 and March&amp;#xA0;8, 2019 (the &amp;#x201C;Merger
 Agreement&amp;#x201D;), pursuant to which the Merger Sub merged with and
 into X4, with X4 surviving the merger as a wholly owned subsidiary
 of Arsanis. The transactions described in the foregoing sentence
 may be referred to in these condensed consolidated financial
 statements as &amp;#x201C;the Merger.&amp;#x201D;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The transaction was accounted for as a reverse merger in accordance
 with GAAP. Under this method of accounting, X4 was deemed to be the
 accounting acquirer for financial reporting purposes. This
 determination was primarily based on the facts that, immediately
 following the Merger: (i)&amp;#xA0;the Company&amp;#x2019;s stockholders own
 a substantial majority of the voting rights in the combined
 organization, (ii)&amp;#xA0;the Company designated a majority of the
 members of the initial board of directors of the combined
 organization and (iii)&amp;#xA0;the Company&amp;#x2019;s senior management
 hold all key positions in the senior management of the combined
 organization. Accordingly, for accounting purposes, the business
 combination was treated as the equivalent of X4 issuing stock to
 acquire the net assets of Arsanis. As a result, as of the closing
 date of the Merger, the net assets of Arsanis were recorded at
 their acquisition-date fair values in the financial statements of
 the Company and the reported operating results prior to the
 business combination will be those of the Company. In addition,
 transaction costs incurred by the Company in connection with the
 business combination will be expensed as incurred.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 On March&amp;#xA0;13, 2019, Arsanis, X4 and Merger Sub completed the
 Merger pursuant to the terms of the Merger Agreement. Pursuant to
 the terms of the Merger Agreement, each outstanding share of
 X4&amp;#x2019;s common stock and preferred stock was exchanged for
 0.5702 shares of Arsanis&amp;#x2019;s common stock (the &amp;#x201C;Exchange
 Ratio&amp;#x201D;). In addition, all outstanding options exercisable for
 common stock and warrants exercisable for convertible preferred
 stock of X4 became options and warrants exercisable for the same
 number of shares of common stock of Arsanis multiplied by the
 Exchange Ratio. In connection with the Merger, X4 changed its name
 to X4 Therapeutics, Inc. Following the closing of the Merger, X4
 Therapeutics, Inc. is a wholly owned subsidiary of the Company.
 which changed its name to X4 Pharmaceuticals, Inc. As used herein,
 the words &amp;#x201C;the Company&amp;#x201D; refers to, for periods
 following the Merger, X4 Pharmaceuticals, Inc. (formerly Arsanis,
 Inc.), together with is direct and indirect subsidiaries, and for
 periods prior to the Merger, X4 Therapeutics, Inc. (formerly X4
 Pharmaceuticals, Inc.), and its direct and indirect subsidiaries,
 as applicable.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Immediately following the Merger, stockholders of X4 owned
 approximately 63.7% of the combined organization&amp;#x2019;s
 outstanding common stock. On March&amp;#xA0;14, 2019, the combined
 organization&amp;#x2019;s common stock began trading on The Nasdaq
 Capital Market under the ticker symbol &amp;#x201C;XFOR.&amp;#x201D;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Reverse Stock Split&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 On March&amp;#xA0;13, 2019, immediately following the closing of the
 Merger, the Company effected a &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;6-for-1&lt;/font&gt;&lt;/font&gt; reverse stock split of
 its common stock (the &amp;#x201C;Reverse Stock Split&amp;#x201D;).
 Accordingly, all share and per share amounts for all periods
 presented in the accompanying condensed consolidated financial
 statements and notes thereto have been adjusted retroactively,
 where applicable, to reflect the Reverse Stock Split. No fractional
 shares were issued in connection with the Reverse Stock Split.
 Unless otherwise noted, all references to common stock share and
 per share amounts have also been adjusted to reflect the exchange
 ratio of 0.5702.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 18px"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt"&gt;
 &lt;b&gt;&lt;i&gt;Going Concern Assessment&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 In accordance with Accounting Standards Update (&amp;#x201C;ASU&amp;#x201D;)
 &lt;font style="WHITE-SPACE: nowrap"&gt;No.&amp;#xA0;2014-15,&lt;/font&gt;
 &lt;i&gt;Disclosure of Uncertainties about an Entity&amp;#x2019;s Ability to
 Continue as a Going Concern (Subtopic &lt;font style="WHITE-SPACE: nowrap"&gt;205-40)&lt;/font&gt;&lt;/i&gt; , the Company has
 evaluated whether there are certain conditions and events,
 considered in the aggregate, that raise substantial doubt about the
 Company&amp;#x2019;s ability to continue as a going concern within one
 year after the date that the consolidated financial statements are
 issued. As of May&amp;#xA0;14, 2019, the issuance date of these
 condensed consolidated financial statements, the Company expects
 that its cash and cash equivalents, including approximately
 $79&amp;#xA0;million of net proceeds from the public sale of common
 stock, &lt;font style="WHITE-SPACE: nowrap"&gt;pre-funded&lt;/font&gt; warrants
 and Class A warrants in April 2019, will be sufficient to fund its
 forecasted operating expenses, capital expenditure requirements and
 debt service payments for at least the next twelve months from the
 issuance of these financial statements. The future viability of the
 Company beyond that point is dependent on its ability to raise
 additional capital to finance its operations.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 If the Company is unable to obtain funding, the Company will be
 forced to delay, reduce or eliminate some or all of its research
 and development programs, product portfolio expansion or
 &lt;font style="WHITE-SPACE: nowrap"&gt;pre-commercialization&lt;/font&gt;
 efforts, which could adversely affect its business prospects, or
 the Company may be unable to continue operations. Although
 management continues to pursue these plans, there is no assurance
 that the Company will be successful in obtaining sufficient funding
 on terms acceptable to the Company to fund continuing operations,
 if at all.&lt;/p&gt;


 &lt;/div&gt;</us-gaap:BusinessDescriptionAndBasisOfPresentationTextBlock>
  <us-gaap:BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="INF" id="id_13073811_44122F24-C6B2-4B50-A879-793D0E18D5E0_1_0" unitRef="shares">2440582</us-gaap:BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued>
  <us-gaap:BusinessAcquisitionsProFormaNetIncomeLoss contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_FA59C7C3-41CE-40D3-B082-A081C38793F6_1_1" unitRef="iso4217_USD">-16258000</us-gaap:BusinessAcquisitionsProFormaNetIncomeLoss>
  <us-gaap:BusinessCombinationAcquisitionRelatedCosts contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-6" id="id_13073811_3EFE5F1B-B690-449C-97CA-0BF7DA7C75E6_1_1" unitRef="iso4217_USD">1000000</us-gaap:BusinessCombinationAcquisitionRelatedCosts>
  <us-gaap:BasisOfAccountingPolicyPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_57305698-D281-47B6-9222-23E4DB55240E_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Unaudited Interim Financial Statements&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The condensed balance sheet at December&amp;#xA0;31, 2018 was derived
 from audited financial statements but does not include all
 disclosures required by GAAP. The accompanying condensed
 consolidated financial statements are unaudited. The accompanying
 unaudited interim consolidated financial statements have been
 prepared by the Company pursuant to the rules and regulations of
 the Securities and Exchange Commission (the &amp;#x201C;SEC&amp;#x201D;) for
 interim financial statements. Accordingly, certain information and
 footnote disclosures normally included in financial statements
 prepared in accordance with GAAP have been condensed or omitted
 pursuant to such rules and regulations. However, the Company
 believes that the disclosures are adequate to make the information
 presented not misleading. These unaudited condensed financial
 statements should be read in conjunction with the
 Company&amp;#x2019;s&amp;#xA0;audited financial statements and the notes
 thereto for the year ended December&amp;#xA0;31, 2018. In the opinion
 of management, all adjustments, consisting only of normal recurring
 adjustments as necessary, for the fair statement of the
 Company&amp;#x2019;s condensed financial position, condensed results of
 its operations and cash flows have been made. The results of
 operations for the three months ended March&amp;#xA0;31, 2019 are not
 necessarily indicative of the results of operations that may be
 expected for the year ending December&amp;#xA0;31, 2019.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:BasisOfAccountingPolicyPolicyTextBlock>
  <us-gaap:BusinessAcquisitionProFormaInformationTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_D78EF124-5A8F-4E93-B3D5-952F9256DF2D_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The following supplemental unaudited pro forma information presents
 the Company&amp;#x2019;s financial results as if the acquisition of
 Arsanis had occurred on January&amp;#xA0;1, 2018:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="78%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="4%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="4%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="6" align="center"&gt;&lt;b&gt;Three Months Ended&lt;br /&gt;
 March&amp;#xA0;31,&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;2019&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;2018&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" colspan="6" align="center"&gt;
 &lt;b&gt;(unaudited)&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Revenue&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;0&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;0&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Net loss&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(16,258&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(20,235&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;/div&gt;</us-gaap:BusinessAcquisitionProFormaInformationTextBlock>
  <us-gaap:BusinessCombinationDisclosureTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_662B77D9-727D-4FEE-BEAD-72F4FB29E932_1_0">&lt;div&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;&lt;b&gt;3.&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;&lt;b&gt;Merger Accounting&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Based on the Exchange Ratio of 0.5702, immediately following the
 Merger, former Arsanis stockholders, Arsanis option holders and
 other persons holding securities or other rights directly or
 indirectly convertible, exercisable or exchangeable for Arsanis
 common stock owned approximately 31.3% of the outstanding capital
 stock of the combined organization on a fully diluted basis, and
 former X4&amp;#xA0;stockholders, holders of options or warrants to
 acquire X4 capital stock and other persons holding securities and
 other rights directly or indirectly convertible, exercisable or
 exchangeable for X4 capital stock owned approximately 68.7% of the
 outstanding capital stock of the combined organization on a fully
 diluted basis. At the closing of the Merger, all shares of X4
 common stock and X4&amp;#xA0;preferred stock then outstanding were
 exchanged for Arsanis common stock.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In addition, pursuant to the terms of the Merger Agreement, the
 Company, for accounting purposes, assumed all outstanding stock
 options to purchase shares of Arsanis common stock at the closing
 of the Merger. At the closing of the Merger, such stock options
 became options to purchase an aggregate of 271,230 shares of the
 Company&amp;#x2019;s common stock after giving effect to the Reverse
 Stock Split.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The total purchase price paid in the Merger has been allocated to
 the tangible and intangible assets acquired and liabilities assumed
 of Arsanis based on their fair values as of the completion of the
 Merger, with the excess allocated to goodwill. The following
 summarizes the preliminary estimate of the purchase price paid in
 the Merger:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="85%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="9%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Number of shares of the combined organization owned by Arsanis
 stockholders&amp;#xA0;(1)&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2,440,582&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Multiplied by the fair value per share of Arsanis common
 stock&amp;#xA0;(2)&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;18.66&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Fair value of consideration issued it effect the Merger&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;45,541&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Fair value of replacement awards held by former employees, board of
 directors and consultants of Arsanis that were vested as of the
 Merger.&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;817&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Purchase price:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;46,358&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 2pt; FONT-SIZE: medium; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WIDTH: 124px; WHITE-SPACE: normal; WORD-SPACING: 0px; BORDER-BOTTOM: rgb(0,0,0) 1px solid; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; LINE-HEIGHT: 8pt; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;(1)&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;The number of shares of 2,440,582 represents the
 historical 14,643,737 shares of Arsanis common stock outstanding
 immediately prior to the closing of the Merger, adjusted for the
 Reverse Stock Split.&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;(2)&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;Based on the last reported sale price of Arsanis
 common stock on the Nasdaq Global Market on March&amp;#xA0;13, 2019,
 the closing date of the Merger, and gives effect to the Reverse
 Stock Split.&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The following summarizes the allocation of the purchase price to
 the net tangible and intangible assets acquired:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="85%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="6%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Cash and cash equivalents and restricted cash&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;26,406&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Other current assets&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2,147&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Property and equipment, net&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;68&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 IPR&amp;amp;D indefinite-lived intangible assets&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,900&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Other assets,&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-current&lt;/font&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;879&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Current liabilities&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(5,221&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Loans payable&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(8,713&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Other liabilities,&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-current&lt;/font&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(1,515&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Goodwill&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;27,407&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Purchase price&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;
 &amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;46,358&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The goodwill of $27,407 is not tax deductible and represents the
 excess of the consideration paid over the fair value of assets
 acquired and liabilities assumed.&amp;#xA0;Goodwill is mainly
 attributable to the enhanced value of the combined company, as
 reflected in the increase in market value of the Arsanis common
 shares following the announcement of the Merger with X4. The
 Company incurred costs directly related to the Merger of
 approximately $1&amp;#xA0;million for the three months ended
 March&amp;#xA0;31, 2019.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The preliminary allocation of the purchase price for the Merger was
 based on estimates of the fair value of the net assets acquired and
 is subject to adjustment upon finalization of the valuation of the
 acquired intangible assets, property, plant and
 equipment,&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt;&amp;#xA0;assets,
 lease obligations, fair value of debt and any related deferred
 taxes. Measurements of these items inherently require significant
 estimates and assumptions.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The following supplemental unaudited pro forma information presents
 the Company&amp;#x2019;s financial results as if the acquisition of
 Arsanis had occurred on January&amp;#xA0;1, 2018:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="78%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="4%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="4%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="6" align="center"&gt;&lt;b&gt;Three Months Ended&lt;br /&gt;
 March&amp;#xA0;31,&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;2019&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;2018&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" colspan="6" align="center"&gt;
 &lt;b&gt;(unaudited)&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Revenue&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;0&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;0&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Net loss&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(16,258&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(20,235&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The above unaudited pro forma information was determined based on
 the historical GAAP results of the Company and Arsanis. The
 unaudited pro forma consolidated results are not necessarily
 indicative of what the Company&amp;#x2019;s consolidated results of
 operations would have been if the acquisition was completed on
 January&amp;#xA0;1, 2018. The unaudited pro forma consolidated net loss
 includes pro forma adjustments primarily relating to the
 reclassification of transaction costs and severance payments
 directly related to the closing of the Merger of $2.7&amp;#xA0;million
 from the three months ended March&amp;#xA0;31, 2019 to the three months
 ended March&amp;#xA0;31, 2018.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:BusinessCombinationDisclosureTextBlock>
  <us-gaap:CashAndCashEquivalentsPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_A745EAA4-E0BA-4D08-809A-15D00EEC2F90_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Cash and Cash Equivalents&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company considers all highly liquid investments with maturities
 of three months or less at the date of purchase to be cash
 equivalents. Cash equivalents consisted of money market funds as of
 March&amp;#xA0;31, 2019 and December&amp;#xA0;31, 2018.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:CashAndCashEquivalentsPolicyTextBlock>
  <us-gaap:CashAndCashEquivalentsRestrictedCashAndCashEquivalentsPolicy contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_1D79CEBF-C26B-4B71-843E-DFF78D17637B_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Restricted Cash&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 In connection with the Company&amp;#x2019;s lease agreement entered into
 January 2017 for its facility in Cambridge, Massachusetts, the
 Company maintains a letter of credit of $264 for the benefit of the
 landlord. As of March&amp;#xA0;31, 2019 and December&amp;#xA0;31, 2018, the
 underlying cash balance securing this letter of credit was
 classified as restricted cash &lt;font style="WHITE-SPACE: nowrap"&gt;(non-current)&lt;/font&gt; on its condensed
 consolidated balance sheets.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company also maintains letters of credit for the benefit of the
 landlords in connection with the Company&amp;#x2019;s office,
 laboratory, parking and storage space leases in Waltham, MA and
 Vienna, Austria and another letter of credit in connection with
 Company&amp;#x2019;s corporate credit cards. As of March&amp;#xA0;31, 2019,
 long term restricted cash consisted of letters of credit related to
 the Company&amp;#x2019;s leases of office, laboratory, parking and
 storage space lease in Vienna, Austria, of $283 and leased office
 space acquired from Arsanis located in Waltham, MA, which expires
 on December&amp;#xA0;31, 2023, of approximately $250.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 As of March&amp;#xA0;31, 2019, the Company was also required to
 maintain a separate cash balance of $150 to collateralize corporate
 credit cards with a bank, which was classified as restricted cash
 &lt;font style="WHITE-SPACE: nowrap"&gt;(non-current)&lt;/font&gt; on its
 consolidated balance sheets.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:CashAndCashEquivalentsRestrictedCashAndCashEquivalentsPolicy>
  <us-gaap:CollaborativeArrangementDisclosureTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_C3DD5739-91D7-4CCE-A453-885462544D2C_1_0">&lt;div&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;&lt;b&gt;13.&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;&lt;b&gt;License, Collaboration, and Funding
 Agreements&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 &lt;b&gt;&lt;i&gt;Genzyme Agreement&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 In July&amp;#xA0;2014, the Company entered into a license agreement
 (the &amp;#x201C;Genzyme Agreement&amp;#x201D;) with Genzyme pursuant to
 which the Company was granted an exclusive license to certain
 patents and intellectual property owned or controlled by Genzyme
 related to the CXCR4 receptor to develop and commercialize products
 containing licensed compounds (including but not limited to
 &lt;font style="WHITE-SPACE: nowrap"&gt;X4P-001)&lt;/font&gt; for all
 therapeutic, prophylactic and diagnostic uses, with the exception
 of autologous and allogenic human stem cell therapy. Under the
 terms of the Genzyme Agreement, the Company is obligated to use
 commercially reasonable efforts to develop and commercialize
 licensed products for use in the field in the United States and at
 least one other major market country. The Company has the right to
 grant sublicenses of the licensed rights that cover &lt;font style="WHITE-SPACE: nowrap"&gt;X4P-001&lt;/font&gt; to third parties.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 In exchange for these rights, in August 2014, the Company made an
 upfront payment of $50 to Genzyme. The Company accounted for the
 acquisition of technology as an asset acquisition because it did
 not meet the definition of a business. The Company recorded the
 upfront payment as research and development expense in the
 consolidated statement of operations and comprehensive loss because
 the acquired technology represented &lt;font style="WHITE-SPACE: nowrap"&gt;in-process&lt;/font&gt; research and development
 and had no alternative future use. In August&amp;#xA0;2015, as a result
 of the closing of the Company&amp;#x2019;s Series A preferred stock
 financing, the Company made an additional cash payment of $300 to
 Genzyme and issued to Genzyme 107,371 shares of its common stock,
 as adjusted for the 6 for 1 Reverse Stock Split and Exchange Ratio
 (see Note&amp;#xA0;11), each as required by the Genzyme Agreement. The
 $300 payment and the $734 fair value of the 107,371 shares of
 common stock issued to Genzyme were recorded as research and
 development expense in the consolidated statements of operations
 and comprehensive loss for the year ended December&amp;#xA0;31, 2015.
 Prior to the Merger with Arsanis, Genzyme has the right to require
 the Company to repurchase all, but not less than all, of these
 shares of common stock at any time during the term of the Genzyme
 Agreement for a price of $0.01 per share. Due to this redemption
 feature, the shares of common stock issued to Genzyme were
 classified outside of stockholders&amp;#x2019; deficit on the
 consolidated balance sheets as of December&amp;#xA0;31, 2018. On
 March&amp;#xA0;13, 2019, the closing date of the Merger with Arsanis,
 these redeemable common shares were exchanged for common shares
 and, as a result, the fair value of the shares was reclassified to
 permanent equity.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Under the Genzyme Agreement, the Company is obligated to pay
 Genzyme milestone payments in the aggregate amount of up to
 $25,000, contingent upon the achievement by the Company of certain
 late-stage regulatory and sales milestones with respect to licensed
 products. In addition, the Company may be required to make a
 &lt;font style="WHITE-SPACE: nowrap"&gt;one-time&lt;/font&gt; milestone payment
 to Genzyme upon the consummation by the Company of a change of
 control transaction, in an amount equal to 5.5% of the
 consideration paid to equity holders of the Company, other than
 Genzyme, in connection with such change of control transaction,
 after deducting outstanding debt obligations of the Company and the
 aggregate cash investments made by equity holders into the Company
 prior to the closing of the change of control transaction. The
 Merger with Arsanis qualifies as a change of control transaction,
 as defined in the license agreement, but results in no payment
 being due to Genzyme under the license agreement.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company concluded that this contingent payment obligation meets
 the definition of a derivative instrument as the contingent payment
 obligation is not clearly and closely related to its host
 instrument and is a cash-settled liability (see Note&amp;#xA0;2).
 Accordingly, the Company classifies this derivative as a liability
 within other liabilities &lt;font style="WHITE-SPACE: nowrap"&gt;(non-current)&lt;/font&gt; on its consolidated
 balance sheet (see Note&amp;#xA0;2), and changes in the fair value of
 the derivative liability are recognized as a component of other
 income (expense), net in the consolidated statement of operations
 and comprehensive loss (see Note&amp;#xA0;4). On March&amp;#xA0;13, 2019,
 the closing date of the Merger with Arsanis, this derivative
 liability was remeasured to fair value, which was $0, and
 subsequent changes in fair value will no longer be recognized in
 the consolidated statements of operations and comprehensive loss
 because the contingent payment obligation expired at that time.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Under the Genzyme Agreement, the Company is obligated to pay
 Genzyme tiered royalties based on net sales of licensed products
 that the Company commercializes under the agreement. The obligation
 to pay royalties for each licensed product expires on a
 &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;country-by-country&lt;/font&gt;&lt;/font&gt; basis on the
 latest of (i)&amp;#xA0;the expiration of&amp;#xA0;licensed patent rights
 that cover that licensed product in that country, (ii)&amp;#xA0;the
 expiration of regulatory exclusivity in that country and
 (iii)&amp;#xA0;ten years after the first commercial sale of such
 licensed product in that country. Royalty rates are subject to
 reduction under the agreement in specified circumstances, including
 in any country if the Company is required to obtain a license from
 any third party to the extent the Company&amp;#x2019;s patent rights
 might infringe the third party&amp;#x2019;s patent rights, if a licensed
 product is not covered by a valid claim in that country or if sales
 of generic products reach certain thresholds in that country. If
 the Company enters into a sublicense under the agreement, the
 Company will be obligated to pay Genzyme a percentage of certain
 upfront fees, maintenance fees, milestone payments and royalty
 payments paid to the Company by the sublicensee.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Under the Genzyme Agreement, the Company will itself manufacture
 and supply, or enter into manufacturing or supply agreements with
 Genzyme or third parties to manufacture and supply, clinical and
 commercial supplies of licensed compounds and each licensed
 product. During the three months ended March&amp;#xA0;31, 2019 and
 2018, the Company did not enter into any third-party manufacturing
 or supply agreements in connection with the Genzyme Agreement. The
 Company is also responsible for all costs related to the filing,
 prosecution and maintenance of the licensed patent rights.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Genzyme Agreement will remain in effect until the expiration of
 the royalty term in all countries for all licensed
 products.&amp;#xA0;The agreement may be terminated by either party with
 at least 90&amp;#xA0;days&amp;#x2019; notice in the event of material breach
 by the other party that remains uncured for 90 days, by either
 party for insolvency or bankruptcy of the other party, immediately
 by Genzyme if the Company challenges the licensed patents, or
 immediately by the Company if a material safety issue arises.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 During the three months ended March&amp;#xA0;31, 2019 and 2018, the
 Company did not incur any payment obligations to Genzyme under the
 Genzyme Agreement.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Georgetown Agreement&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 In December 2016, the Company entered into a license agreement (the
 &amp;#x201C;Georgetown Agreement&amp;#x201D;) with Georgetown University
 (&amp;#x201C;Georgetown&amp;#x201D;) pursuant to which the Company obtained
 an exclusive, worldwide license to make, have made, use, sell,
 offer for sale and import of products covered by patent rights
 &lt;font style="WHITE-SPACE: nowrap"&gt;co-owned&lt;/font&gt; by Georgetown.
 The rights licensed to the Company are for all therapeutic,
 prophylactic and diagnostic uses in all disease indications in
 humans and animals.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Under the terms of the Georgetown Agreement, the Company paid a
 &lt;font style="WHITE-SPACE: nowrap"&gt;one-time&lt;/font&gt; only, upfront fee
 of $50 and the Company may be required to pay milestone payments of
 up to an aggregate of $800 related to commercial sales of a
 product. The Company accounted for the acquisition of technology as
 an asset acquisition because it did not meet the definition of a
 business. The Company recorded the upfront payment as research and
 development expense in the consolidated statement of operations and
 comprehensive loss because the acquired technology represented
 &lt;font style="WHITE-SPACE: nowrap"&gt;in-process&lt;/font&gt; research and
 development and had no alternative future use.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Under the Georgetown Agreement, the Company is solely responsible
 for all development and commercialization activities and costs in
 its respective territories. The Company is also responsible for all
 costs related to the filing, prosecution and maintenance of the
 licensed patent rights.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 12px"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt"&gt;
 The term of the Georgetown Agreement will continue until the
 expiration of the last valid claim within the patent rights
 covering the product. Georgetown may terminate the agreement in the
 event (i)&amp;#xA0;the Company fails to pay any amount and fails to
 cure such failure within 30 days after receipt of notice,
 (ii)&amp;#xA0;the Company defaults in its obligation to obtain and
 maintain insurance and fails to remedy such breach within
 45&amp;#xA0;days after receipt of notice, or (iii)&amp;#xA0;the Company
 declares insolvency or bankruptcy. The Company may terminate the
 agreement at any time upon at least 60&amp;#xA0;days&amp;#x2019; written
 notice.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 During the three months ended March&amp;#xA0;31, 2019 and 2018, the
 Company did not incur any payment obligations to Georgetown under
 the Georgetown Agreement and no milestone payments were made or due
 under the Georgetown Agreement.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Beth Israel Deaconess Medical Center Agreement&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 In December 2016, the Company entered into a license agreement (the
 &amp;#x201C;BIDMC Agreement&amp;#x201D;) with Beth Israel Deaconess Medical
 Center (&amp;#x201C;BIDMC&amp;#x201D;), pursuant to which the Company
 obtained an exclusive, worldwide license to make, have made, use,
 sell, offer for sale and import of products covered by patent
 rights &lt;font style="WHITE-SPACE: nowrap"&gt;co-owned&lt;/font&gt; by BIDMC.
 The rights licensed to the Company are for all fields of use.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Under the terms of the BIDMC Agreement, the Company paid a
 &lt;font style="WHITE-SPACE: nowrap"&gt;one-time&lt;/font&gt; only, upfront fee
 of $20 and the Company is responsible for all future patent
 prosecution costs. The Company accounted for the acquisition of
 technology as an asset acquisition because it did not meet the
 definition of a business. The Company recorded the upfront payment
 as research and development expense in the consolidated statement
 of operations and comprehensive loss because the acquired
 technology represented &lt;font style="WHITE-SPACE: nowrap"&gt;in-process&lt;/font&gt; research and development
 and had no alternative future use.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The term of the BIDMC Agreement will continue until the expiration
 of the last valid claim within the patent rights covering the
 licensed products. BIDMC may terminate the agreement in the event
 (i)&amp;#xA0;the Company fails to pay any amount and fails to cure such
 failure within 15 days after receipt of notice, (ii)&amp;#xA0;the
 Company is in material breach of any material provision of the
 agreement and fails to remedy such breach within 60 days after
 receipt of notice, or (iii)&amp;#xA0;the Company declares insolvency or
 bankruptcy. We may terminate the agreement at any time upon at
 least 90 days&amp;#x2019; written notice.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company did not incur any payment obligations under the BIDMC
 Agreement during the months ended March&amp;#xA0;31, 2019 and 2018.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Adimab Option and License Agreement&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 In February 2017, Arsanis entered into an option and license
 agreement with Adimab, a related party (the &amp;#x201C;Adimab Option
 Agreement&amp;#x201D;). Under the Adimab Option Agreement, Adimab has
 provided to Arsanis certain proprietary antibodies against
 respiratory syncytial virus (&amp;#x201C;RSV antibodies&amp;#x201D;) for its
 evaluation during a specified option period and has granted Arsanis
 an exclusive, &lt;font style="WHITE-SPACE: nowrap"&gt;non-sublicensable&lt;/font&gt; license in a
 specified field under certain Adimab patent rights and &lt;font style="WHITE-SPACE: nowrap"&gt;know-how&lt;/font&gt; during the option period.
 Under the Adimab Option Agreement, the Company has an exclusive
 option, exercisable during the option period upon payment of an
 option fee to Adimab, to require Adimab to assign to the Company
 all rights in up to a specified number of RSV antibodies selected
 by the Company and certain patent rights owned by Adimab that cover
 these antibodies, and to obtain from Adimab a &lt;font style="WHITE-SPACE: nowrap"&gt;non-exclusive&lt;/font&gt; license in a specified
 field, with the right to grant sublicenses, under certain other
 patent rights and &lt;font style="WHITE-SPACE: nowrap"&gt;know-how&lt;/font&gt;
 owned by Adimab.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 If the Company exercises its option under the Adimab Option
 Agreement, the Company is required to use commercially reasonable
 efforts to develop and commercialize at least one product based on
 a licensed RSV antibody in major markets and is obligated to pay
 Adimab an option fee of $0.3&amp;#xA0;million and make future milestone
 payments upon the achievement of specified clinical and regulatory
 milestones in the aggregate amount of up to $24.4&amp;#xA0;million. The
 Company is obligated to pay Adimab royalties at a mid single-digit
 percentage of net sales of products based on the initial RSV
 antibodies (including modified or derivative forms of those
 antibodies created by or for the Company) by the Company or any of
 its affiliates, licensees or sublicensees, regardless of whether
 these products practice any of the assigned or licensed patents or
 &lt;font style="WHITE-SPACE: nowrap"&gt;know-how.&lt;/font&gt; If the Company
 materially breaches these diligence obligations, Adimab will have
 the right to terminate the Adimab Option Agreement.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company has no payment obligations under the Adimab Option
 Agreement with respect to sales of products based on licensed RSV
 antibodies to the extent they are sold at cost in developing
 countries under the February 2017 Gates Foundation grant agreement,
 as amended and restated in August 2018, and the August 2018 Gates
 Foundation grant agreement (which are described in further detail
 below). However, if such products are sold in developing countries
 for an amount that exceeds cost, then the amount of such excess
 will be subject to the royalty payment obligations described in the
 preceding paragraph.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 12px"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt"&gt;
 If the Company does not exercise its option, the Adimab Option
 Agreement will expire on the Company&amp;#x2019;s achievement of
 specified preclinical milestones under the grant agreements with
 the Gates Foundation, but in any event no later than &lt;font style="WHITE-SPACE: nowrap"&gt;mid-2019.&lt;/font&gt; If the Company does exercise
 its option, the Adimab Option Agreement will expire on the
 &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;last-to-expire&lt;/font&gt;&lt;/font&gt; royalty term
 (defined, on a &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;product-by-product&lt;/font&gt;&lt;/font&gt; and
 &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;country-by-country&lt;/font&gt;&lt;/font&gt; basis, as
 the period ending on the later of twelve years after the first
 commercial sale of such product in such country and the expiration
 of the last of a specified set of patents and patent applications
 covering such product in such country) for any and all products for
 which the Company is obligated to pay Adimab royalties under the
 Adimab Option Agreement. The Company has the right to terminate the
 Adimab Option Agreement for any reason by providing Adimab with a
 specified amount of prior written notice. Adimab has the right to
 terminate the Adimab Option Agreement if the Company materially
 breaches the agreement and fails to cure such breach within a
 specified cure period, including for the Company&amp;#x2019;s failure to
 use commercially reasonable efforts to develop and commercialize at
 least one product based on a licensed RSV antibody in major
 markets. If Adimab terminates the Adimab Option Agreement for the
 Company&amp;#x2019;s breach, if the Company terminates the agreement for
 convenience or if the agreement expires before the Company
 exercises its option, then the Company must return or destroy
 certain &lt;font style="WHITE-SPACE: nowrap"&gt;know-how,&lt;/font&gt;
 including all initial RSV antibodies, and all modified or
 derivative forms of those antibodies, in its possession other than
 those for which the Company has made all payments required under
 the Adimab Option Agreement, assign certain patents covering
 certain RSV antibodies to Adimab, grant Adimab a &lt;font style="WHITE-SPACE: nowrap"&gt;non-exclusive,&lt;/font&gt; royalty-free license
 under certain other patents, and grant Adimab a time-limited right
 of first negotiation to obtain an exclusive license to certain
 patents and &lt;font style="WHITE-SPACE: nowrap"&gt;know-how&lt;/font&gt; and
 the transfer and assignment of certain regulatory filings and
 approvals and other related assets related to products based on
 licensed RSV antibodies. Certain of the Company&amp;#x2019;s payment
 obligations relating to specified products and patents arising from
 the agreement survive expiration or termination of the
 agreement.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 During the three months ended March&amp;#xA0;31, 2019, the Company
 recognized no research and development expense in connection with
 the Adimab Option Agreement.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Adimab Collaboration Agreement&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 In May 2011, Arsanis entered into a collaboration agreement with
 Adimab, LLC (&amp;#x201C;Adimab&amp;#x201D;) and together with certain
 applicable option exercise letters the Company has sent to Adimab,
 the &amp;#x201C;Adimab Collaboration Agreement&amp;#x201D;). Under the Adimab
 Collaboration Agreement, the Company and Adimab were required to
 use reasonable efforts to conduct certain research, which was
 funded by the Company, to discover and optimize antibodies directed
 against targets selected by the Company. With respect to each
 target that was the subject of the research, the Company had an
 exclusive option to obtain, with respect to a specified number of
 antibodies directed against such target and discovered or optimized
 by Adimab, (i)&amp;#xA0;ownership of certain patent rights relating to
 such antibodies and (ii)&amp;#xA0;exclusive and &lt;font style="WHITE-SPACE: nowrap"&gt;non-exclusive&lt;/font&gt; licenses in a specified
 field, with the right to grant sublicenses, under certain patent
 rights and &lt;font style="WHITE-SPACE: nowrap"&gt;know-how.&lt;/font&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Under the Adimab Collaboration Agreement, for each target for which
 the Company has exercised an option, the Company is required to use
 commercially reasonable efforts to develop and commercialize at
 least one product in major markets. If the Company does not fulfill
 these diligence obligations, Adimab may consider it a material
 breach, allowing Adimab to terminate the Adimab Collaboration
 Agreement with respect to such target and all associated
 products.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company is obligated to pay Adimab royalties at a mid
 single-digit percentage of net sales made by the Company or its
 affiliates of products based on antibodies for which the Company
 exercised its option, or products that use or are based on any
 antibody discovered or optimized under the agreement, any
 derivative or modified version of any such antibody, or any
 sequence information as to any such antibody. In addition, if the
 Company sells or licenses to any third party, or otherwise grants
 rights to any third party to, any of the products for which the
 Company is obligated to pay Adimab royalties, either alone or as
 part of a package including specified patents not directed to these
 antibodies, the Company is obligated to pay Adimab either
 (i)&amp;#xA0;the same royalties on net sales of such products by such
 third party or (ii)&amp;#xA0;a percentage, ranging from the low double
 digits to a maximum of less than 30%, of the payments the Company
 receives from such third parties that are attributable to such
 grant of rights. In April 2017, the Company entered into a letter
 agreement with the Gates Foundation, pursuant to which the Company
 licensed to the Gates Foundation certain rights under its
 ASN100&amp;#xA0;program. The Company has no payment obligations under
 the Adimab Collaboration Agreement with respect to sales of certain
 antibody products if they are sold at cost in developing countries
 under its letter agreement with the Gates Foundation. However, if
 such products are sold in developing countries for an amount that
 exceeds cost, then the amount of such excess over cost will be
 subject to the royalty payment obligations described above.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 If the Company (or one of its affiliates with rights under the
 agreement) undergoes a change in control and, at the time of such
 change in control, the Company has not sold or licensed to third
 parties all of its rights in antibodies for which the Company is
 obligated to pay Adimab royalties under the agreement, then the
 Company is obligated to either (i)&amp;#xA0;pay Adimab a percentage, in
 the mid double digits, of the payments it receives from that change
 in control that are reasonably attributable to those rights and
 certain patents arising from the collaboration or (ii)&amp;#xA0;require
 the Company&amp;#x2019;s acquirer and all of its future third-party
 collaborators to pay to Adimab the royalties at a mid single-digit
 percentage of net sales based on those rights. If the Company
 grants rights to a third party under certain patents that are not
 directed to the antibodies for which the Company is obligated to
 pay Adimab royalties (as described above), the Company is also
 obligated to pay Adimab, in place of royalties or a percentage of
 payments received from the third party, a lump sum in the high six
 digits.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Adimab Collaboration Agreement will expire on a &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;country-by-country&lt;/font&gt;&lt;/font&gt; basis twelve
 years after the first commercial sale in such country of the last
 product for which the Company is obligated to pay Adimab royalties
 in such country under the Adimab Collaboration Agreement. The
 Company has the right to terminate the Adimab Collaboration
 Agreement for any reason by providing Adimab with a specified
 amount of prior written notice. Adimab has the right to terminate
 the Adimab Collaboration Agreement if the Company materially
 breaches the agreement and fails to cure such breach within a
 specified cure period, including for its failure to use
 commercially reasonable efforts to develop and commercialize at
 least one product directed at a target for which the Company has
 exercised an option in major markets. If Adimab terminates the
 Adimab Collaboration Agreement for the Company&amp;#x2019;s breach, or
 if the Company terminates the agreement for convenience, then the
 Company must transfer or license to Adimab certain rights and
 assets relating to targets and antibodies for which the Company has
 exercised its option. Adimab is then obligated to make payments to
 the Company with respect to these targets and antibodies that are
 similar to the payments the Company is required to make to Adimab
 during the term of the agreement. Certain of the Company&amp;#x2019;s
 payment obligations relating to specified products and patents
 arising from the agreement survive expiration or termination of the
 agreement.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 During the three months ended March&amp;#xA0;31, 2019, the Company did
 not recognize any research and development under the Adimab
 Collaboration Agreement.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Gates Foundation Grant Agreements&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 In February 2017, Arsanis entered into a grant agreement with the
 Gates Foundation (&amp;#x201C;Grant Agreement&amp;#x201D;), under which the
 Gates Foundation agreed to provide the Company up to approximately
 $9,300 to conduct preclinical development of monoclonal antibodies
 for the prevention of RSV infection in newborns (the &amp;#x201C;RSV
 project&amp;#x201D;).&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 In connection with this Grant Agreement, the Company has granted to
 the Gates Foundation a &lt;font style="WHITE-SPACE: nowrap"&gt;non-exclusive,&lt;/font&gt; perpetual,
 royalty-free, fully paid up, sublicensable license to make, use,
 sell, offer to sell, import, distribute, copy, modify, create
 derivative works, publicly perform and display the funded
 developments and, to the extent incorporated into a funded
 development or required to use a funded development, any other
 technology created outside of the RSV project that was used as part
 of the RSV project, for the benefit of people in developing
 countries. This license survives any expiration or termination of
 the grant agreement. The Grant Agreement expires on
 October&amp;#xA0;31, 2019. The Gates Foundation can modify, suspend or
 discontinue any payment under the grant agreement, or terminate the
 grant agreement, if it is not reasonably satisfied with the
 Company&amp;#x2019;s progress on the RSV project; if there are
 significant changes to the Company&amp;#x2019;s leadership or other
 factors that the Gates Foundation reasonably believes may threaten
 the RSV project&amp;#x2019;s success; if the Company undergoes a change
 in control; if there is a change in the Company&amp;#x2019;s tax status;
 if the RSV project is no longer aligned with the Gates
 Foundation&amp;#x2019;s programmatic strategy; or if the Company fails
 to comply with the grant agreement. Any grant funds that have not
 been used for, or committed to, the RSV project upon the expiration
 or termination of the grant agreement must be returned to the Gates
 Foundation or otherwise used as directed by the Gates Foundation.
 In August 2018, Arsanis entered into an amended and restated grant
 agreement which replaced the February 2017 grant agreement in its
 entirety. The amended and restated grant agreement includes
 amendments to conform to current Gates Foundation audit, reporting,
 and other administrative requirements, as well as to make the
 perpetual Gates Foundation license grant described below
 irrevocable.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 During the three months ended March&amp;#xA0;31, 2019, the Company did
 not incur qualifying expenses under the letter agreement with the
 Gates Foundation.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Research and Development Incentive Program&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company participates in a research and development incentive
 program provided by the Austrian government whereby the Company is
 entitled to reimbursement by the Austrian government for a
 percentage of qualifying research and development expenses incurred
 by the Company&amp;#x2019;s subsidiary in Austria. Under the program,
 the reimbursement rate for qualifying research and development
 expenses incurred by the Company through its subsidiary in Austria
 is 14% for the current year .&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company recognizes incentive income from Austrian research and
 development incentives when qualifying expenses have been incurred,
 there is reasonable assurance that the payment will be received,
 and the consideration can be reliably measured. Management has
 assessed the Company&amp;#x2019;s research and development activities
 and expenditures to determine which activities and expenditures are
 likely to be eligible under the research and development incentive
 program described above. At each reporting date, management
 estimates the reimbursable incentive income available to the
 Company based on available information at the time.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 12px"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt"&gt;
 As of March&amp;#xA0;31, 2019, the Company recorded receivables for
 amounts due under the program of $1.6&amp;#xA0;million, which amounts
 were included in grant and incentive receivables in the
 consolidated balance sheet.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Janssen License and Option Agreement&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 On December&amp;#xA0;12, 2018, Arsanis entered into a patent license
 and option agreement with Janssen Pharmaceuticals, Inc.
 (&amp;#x201C;Janssen&amp;#x201D;), (the &amp;#x201C;Janssen License and Option
 Agreement&amp;#x201D;). Pursuant to the Janssen License and Option
 Agreement, Arsanis granted to Janssen (i)&amp;#xA0;a &lt;font style="WHITE-SPACE: nowrap"&gt;non-exclusive&lt;/font&gt; license to specified
 patents in Arsanis&amp;#x2019;s portfolio related to the ASN200 E. coli
 program, and (ii)&amp;#xA0;an option for Janssen to acquire these
 patents in the future if specified conditions are met. Janssen
 agreed to pay Arsanis $3.5&amp;#xA0;million within 15 business days
 after the December&amp;#xA0;12, 2018 effective date of the Janssen
 License and Option Agreement, in addition to a future
 $0.5&amp;#xA0;million payment in the event Janssen exercises its option
 to acquire the relevant patents. Arsanis received the
 $3.5&amp;#xA0;million payment from Janssen in December 2018 and
 recognized this amount as revenue. Such revenue is not reflected in
 the consolidated financial statements of the Company as it occurred
 prior to the Merger. Janssen&amp;#x2019;s option to the relevant patents
 will be recognized as revenue in full in the period in which the
 option exercise occurs.&lt;/p&gt;


 &lt;/div&gt;</us-gaap:CollaborativeArrangementDisclosureTextBlock>
  <us-gaap:CommitmentsAndContingenciesDisclosureTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_7B9B9433-F776-4060-A7C2-0A79F0CF2F28_1_0">&lt;div&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;&lt;b&gt;9.&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;&lt;b&gt;Commitment and Contingencies&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Sponsored Research Agreement Commitments&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In April&amp;#xA0;2017, the Company entered into a sponsored research
 agreement with a university that the Company refers to as the
 Sponsored Research Agreement, pursuant to which the Company and the
 university intend to conduct a research program related to
 understanding the mechanisms of failed long-term adaptive immunity
 in WHIM patients. Under the terms of the Sponsored Research
 Agreement, the Company agreed to provide funding for the research
 program of up to $499 over a three-year period. The Sponsored
 Research Agreement will remain in effect for three years, unless
 earlier terminated in the event that (i)&amp;#xA0;either party
 materially breaches any representation, obligation or covenant and
 fails to remedy such breach within 30 days after receipt of notice
 or (ii)&amp;#xA0;the Principal Investigator, as defined in the
 agreement, is unable or unwilling to conduct the research or
 perform his or her obligations under the agreement, at which time
 the Company may terminate the agreement upon 30 days&amp;#x2019; prior
 written notice to the university. The Company may terminate the
 agreement at any time upon at least 60 days&amp;#x2019; prior written
 notice.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 During the three months ended March&amp;#xA0;31, 2019 and 2018, the
 Company incurred $42, respectively, of research and development
 expenses related to its payment obligations to the university under
 the Sponsored Research Agreement. As of March&amp;#xA0;31, 2019, the
 Company had&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-cancelable&lt;/font&gt;&amp;#xA0;purchase
 commitments under this agreement totaling $181, with $125 committed
 in 2019 and $56 committed in 2020.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Manufacturing Commitments&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 As of March&amp;#xA0;31, 2019, the Company entered into agreements with
 several contract manufacturing organizations to provide preclinical
 and clinical trial materials. As of March&amp;#xA0;31, 2019, and
 December&amp;#xA0;31, 2018, the Company
 had&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-cancelable&lt;/font&gt;&amp;#xA0;purchase
 commitments under these agreements totaling approximately $250, all
 committed in 2019.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Indemnification Agreements&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In the ordinary course of business, the Company may provide
 indemnification of varying scope and terms to vendors, lessors,
 business partners and other parties with respect to certain matters
 including, but not limited to, losses arising out of breach of such
 agreements or from intellectual property infringement claims made
 by third parties. In addition, the Company has entered into
 indemnification agreements with members of its board of directors
 and its executive officers that will require the Company to, among
 other things, indemnify them against certain liabilities that may
 arise by reason of their status or service as directors or
 officers. The maximum potential amount of future payments the
 Company could be required to make under these indemnification
 agreements is, in many cases, unlimited. To date, the Company has
 not incurred any material costs as a result of such indemnification
 obligations. The Company is not currently aware of any
 indemnification claims and has not accrued any liabilities related
 to such obligations in its consolidated financial statements as of
 March&amp;#xA0;31, 2019 or December&amp;#xA0;31, 2018.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;License Agreements&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Arsanis entered into an agreement (the &amp;#x201C;Adimab Option
 Agreement&amp;#x201D;) in February 2017, which was acquired by the
 Company as a result of the Merger, under which the Company is
 obligated to make contingent and&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-contingent&lt;/font&gt;&amp;#xA0;payments
 should the Company exercise its option to obtain rights to certain
 RSV antibodies. If the Company chose to exercise its option, it
 would be obligated to pay Adimab an option fee of approximately
 $250 and make clinical and regulatory milestone payments of up to
 approximately $25,000, as well as royalty payments on
 a&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;product-by-product&lt;/font&gt;&lt;/font&gt;&amp;#xA0;and&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;country-by-country&lt;/font&gt;&lt;/font&gt;&amp;#xA0;basis
 of a mid single-digit percentage based on net sales by the Company,
 its affiliates, licensees or sublicensees of products based on
 certain RSV antibodies during the applicable term for such product
 in that country. The Company may choose to exercise its option
 under the terms of the Adimab Option Agreement at any time on or
 before August&amp;#xA0;31, 2019. As of March&amp;#xA0;31, 2019, the Company
 had not exercised its option under the Adimab Option Agreement.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Legal Proceedings&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The Company is not a party to any litigation and does not have
 contingency reserves established for any litigation liabilities. At
 each reporting date, the Company evaluates whether or not a
 potential loss amount or a potential range of loss is probable and
 reasonably estimable under the provisions of the authoritative
 guidance that addresses accounting for contingencies. The Company
 expenses as incurred the costs related to such legal
 proceedings&lt;/p&gt;
 &lt;/div&gt;</us-gaap:CommitmentsAndContingenciesDisclosureTextBlock>
  <us-gaap:CommonStockVotingRights contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_1AB6290E-7443-4606-BB16-B76C5E212DFB_1_0">Each share of common stock entitles the holder to one vote on all matters  submitted to a vote of the Company's stockholders. The holders of common stock,  voting exclusively and as a separate class, are entitled to elect one director  of the Company.</us-gaap:CommonStockVotingRights>
  <us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_25" unitRef="iso4217_USD">14748000</us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect>
  <us-gaap:ComprehensiveIncomeNetOfTax contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_AF788C25-DA69-4060-97BB-D7B7447FD5A4_5008_1100014" unitRef="iso4217_USD">-10850000</us-gaap:ComprehensiveIncomeNetOfTax>
  <us-gaap:ComprehensiveIncomePolicyPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_06C89066-C2B4-4489-B859-ACAB9B31C2E6_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Comprehensive Loss&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Comprehensive loss includes net loss as well as other changes in
 stockholders&amp;#x2019; equity (deficit) that result from transactions
 and economic events other than those with stockholders. For the
 three months ended March&amp;#xA0;31, 2019, comprehensive loss included
 $23 of foreign currency translation gain adjustments.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:ComprehensiveIncomePolicyPolicyTextBlock>
  <us-gaap:ConsolidationPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_CC63B3FF-E4CF-4358-924A-B79F7EE70BDE_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Principles of Consolidation&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The condensed consolidated financial statements include the
 accounts of the Company and its wholly owned subsidiaries,
 including Arsanis Biosciences GmbH, which is incorporated in
 Vienna, Austria (&amp;#x201C;Arsanis GmbH&amp;#x201D;), and X4 Therapeutics,
 Inc. All significant intercompany accounts and transactions have
 been eliminated.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:ConsolidationPolicyTextBlock>
  <us-gaap:CurrentFederalTaxExpenseBenefit contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_18762938-FB7B-4080-9FE8-709219EE20EB_1_0" unitRef="iso4217_USD">0</us-gaap:CurrentFederalTaxExpenseBenefit>
  <us-gaap:CurrentStateAndLocalTaxExpenseBenefit contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_18762938-FB7B-4080-9FE8-709219EE20EB_1_1" unitRef="iso4217_USD">0</us-gaap:CurrentStateAndLocalTaxExpenseBenefit>
  <dei:CurrentFiscalYearEndDate contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_A7F8FC82-9EF2-433E-A4E3-49D3C0BA9AB7_1_3">--12-31</dei:CurrentFiscalYearEndDate>
  <us-gaap:DebtPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_1CD375D3-AC77-4339-9B60-B1CDC138D884_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Debt Issuance Costs&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Debt issuance costs consist of payments made to secure commitments
 under certain debt financing arrangements. These amounts are
 recognized as interest expense over the period of the financing
 arrangement using the effective interest method. If the financing
 arrangement is canceled or forfeited, or if the utility of the
 arrangement to the Company is otherwise compromised, these costs
 are recognized as interest expense immediately. The Company&amp;#x2019;s
 consolidated financial statements present debt issuance costs
 related to a recognized debt liability as a direct reduction from
 the carrying amount of that debt liability.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:DebtPolicyTextBlock>
  <us-gaap:DerivativeGainLossOnDerivativeNet contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_8" unitRef="iso4217_USD">183000</us-gaap:DerivativeGainLossOnDerivativeNet>
  <us-gaap:DepreciationDepletionAndAmortization contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_4" unitRef="iso4217_USD">20000</us-gaap:DepreciationDepletionAndAmortization>
  <us-gaap:DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_F645D2E3-6949-4020-B04F-F55E90610E0E_1_0">&lt;div&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;&lt;b&gt;12.&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;&lt;b&gt;Stock-Based Compensation&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Summary of Plans&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Upon completion of the Merger with Arsanis on March&amp;#xA0;13, 2019,
 X4&amp;#x2019;s 2015 Employee, Director and Consultant Equity Incentive
 Plan, as amended (the &amp;#x201C;2015 Plan&amp;#x201D;), Arsanis&amp;#x2019; 2017
 Equity Incentive Plan (the &amp;#x201C;2017 Plan&amp;#x201D;) and
 Arsanis&amp;#x2019; 2017 Employee Stock Purchase Plan (the &amp;#x201C;2017
 ESPP&amp;#x201D;) (collectively, the &amp;#x201C;Plans&amp;#x201D;) were assumed
 by the Company. These Plans are administered by the board of
 directors or, at the discretion of the board of directors, by a
 committee of the board of directors. The exercise prices, vesting
 and other restrictions are determined at the discretion of the
 board of directors, or its committee if so delegated, except that
 the exercise price per share of stock options may not be less than
 100% of the fair market value of the share of common stock on the
 date of grant and the term of the stock option may not be greater
 than ten years. Incentive stock options granted to employees and
 restricted stock awards granted to employees, officers, members of
 the board of directors, advisors, and consultants of the Company
 typically vest over four years.&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;Non-statutory&lt;/font&gt;&amp;#xA0;options
 granted to employees, officers, members of the board of directors,
 advisors, and consultants of the Company typically vest over three
 or four years. Shares that are expired, terminated, surrendered or
 canceled under the Plans without having been fully exercised will
 be available for future awards. In addition, shares of common stock
 that are tendered to the Company by a participant to exercise an
 award are added to the number of shares of common stock available
 for the grant of awards.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;2015 Employee, Director and Consultant Equity Incentive
 Plan&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In 2015, the board of directors and shareholders of X4 adopted the
 2015 Plan, which provided for the Company to grant incentive stock
 options or nonqualified stock options, restricted stock awards and
 other stock-based awards to employees, directors and consultants of
 the Company. Each stock option outstanding under the 2015 Plan at
 the effective time of the Merger was automatically converted into a
 stock option exercisable for a number of shares of the
 Company&amp;#x2019;s common stock calculated based on the Exchange Ratio
 and the exercise price per share of such outstanding stock
 option.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The total number of shares of common stock that may be issued under
 the 2015 Plan was 1,700,000 shares, adjusted for the reverse stock
 split as of December&amp;#xA0;31, 2018 and March&amp;#xA0;31, 2019. Shares
 that are expired, forfeited, canceled or otherwise terminated
 without having been fully exercised will be available for future
 grant under the 2015 Plan. In addition, shares of common stock that
 are tendered to the Company by a participant to exercise an award
 are added to the number of shares of common stock available for
 future grants.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;2017 Equity Incentive Plan&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In 2017, the board of directors and shareholders of Arsanis adopted
 the 2017 Plan which provided for the Company to grant incentive
 stock options,&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-qualified&lt;/font&gt;&amp;#xA0;options,
 stock appreciation rights, restricted stock awards, restricted
 stock units and other stock-based awards. Incentive stock options
 may be granted only to the Company&amp;#x2019;s employees, including
 officers and directors who are also employees. Awards other than
 incentive stock options may be granted to employees, officers,
 members of the board of directors, advisors and consultants of the
 Company. The number of shares of common stock reserved for issuance
 under this plan will automatically increase on January&amp;#xA0;1 of
 each year, through January&amp;#xA0;1, 2027, in an amount equal to the
 lowest of 1,025,490 shares of the Company&amp;#x2019;s common stock, 4%
 of the number of shares of the Company&amp;#x2019;s common stock
 outstanding on January&amp;#xA0;1 of each year and an amount determined
 by the Company&amp;#x2019;s board of directors.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;2017 Employee Stock Purchase Plan&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In 2017, the board of directors and shareholders of Arsanis adopted
 the 2017 ESPP. The 2017 ESPP provides participating employees with
 the opportunity to purchase shares of the Company&amp;#x2019;s common
 stock at defined purchase prices
 over&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;six-month&lt;/font&gt;&amp;#xA0;offering
 periods. For the three month period ended March&amp;#xA0;31, 2019, no
 shares of common stock were issued under the 2017 ESPP.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Stock Option Valuation&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The fair value of stock option grants is estimated using the
 Black-Scholes option-pricing model. The Company has historically
 been a private company prior to March&amp;#xA0;13, 2019, and as a
 result, lacked company-specific historical and implied volatility
 information. The Company estimated expected stock volatility based
 on the historical volatility of a publicly traded set of peer
 companies and expects to continue to do so until it has adequate
 historical data regarding the volatility of its own traded stock
 price. For options with service-based vesting conditions, the
 expected term of the Company&amp;#x2019;s stock options has been
 determined utilizing the &amp;#x201C;simplified&amp;#x201D; method for awards
 that qualify as &amp;#x201C;plain-vanilla&amp;#x201D; options. The expected
 term of stock options granted&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;to&amp;#xA0;non-employee&amp;#xA0;consultants&lt;/font&gt;&amp;#xA0;is
 equal to the contractual term of the option award. The risk-free
 interest rate is determined by reference to the U.S. Treasury yield
 curve in effect at the time of grant of the award for time periods
 approximately equal to the expected term of the award. Expected
 dividend yield is based on the fact that the Company has never paid
 cash dividends and does not expect to pay any cash dividends in the
 foreseeable future.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The following table presents, on a weighted average basis, the
 assumptions used in the Black-Scholes option-pricing model to
 determine the grant-date fair value of stock options granted to
 employees, directors and&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-&lt;/font&gt;&amp;#xA0;employees:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="80%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="7%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="7%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="6" align="center"&gt;&lt;b&gt;Three Months Ended&lt;br /&gt;
 March&amp;#xA0;31,&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2019&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2018&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Risk-free interest rate&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2.4&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;%&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2.8&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;%&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Expected term (in years)&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5.90&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5.94&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Expected volatility&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;90.6&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;%&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;86.0&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;%&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Expected dividend yield&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;0&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;%&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;0&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;%&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Stock Options&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The following table summarizes the Company&amp;#x2019;s stock option
 activity since December&amp;#xA0;31, 2018:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="92%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="61%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="5%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="5%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="5%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="5%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Number&amp;#xA0;of&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Shares&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Weighted&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Average&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Exercise&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Price&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Weighted&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Average&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Contractual&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Term&amp;#xA0;(Years)&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Aggregate&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Intrinsic&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Value&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Outstanding as of December&amp;#xA0;31, 2018&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;797,931&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8.29&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;8.42&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;6,486&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Assumed as part of Merger with Arsanis&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;271,230&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;
 &amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;62.60&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Granted&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;136,913&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;17.22&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Exercised&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(16,483&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;6.85&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Forfeited&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(22,378&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8.43&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Outstanding as of March&amp;#xA0;31, 2019&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,167,213&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;21.97&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;7.65&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;7,168&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Exercisable as of March&amp;#xA0;31, 2019&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;556,774&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;30.13&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Vested and expected to vest as of March&amp;#xA0;31, 2019&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;979,466&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;48.79&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The aggregate intrinsic value of options is calculated as the
 difference between the exercise price of the stock options and the
 fair value of the Company&amp;#x2019;s common stock for those options
 that had exercise prices lower than the fair value of the
 Company&amp;#x2019;s common stock. The aggregate intrinsic value of
 stock options exercised during the three months ended
 March&amp;#xA0;31, 2019 was $123. The weighted average grant-date fair
 value per share of stock options granted during the three months
 ended March&amp;#xA0;31, 2019 was $12.88.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Stock-Based Compensation&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Effective January&amp;#xA0;1, 2019, the Company adopted
 ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2018-07&lt;/font&gt;&amp;#xA0;which
 required the Company to adjust compensation expense for the three
 months ended March&amp;#xA0;31, 2019 for an immaterial amount for the
 unvested&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-employee&lt;/font&gt;&amp;#xA0;share
 options outstanding. The Company no longer remeasures the fair
 value of options granted to&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-employees&lt;/font&gt;&amp;#xA0;at
 each reporting period end (see Note&amp;#xA0;2).&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 During the three months ended March&amp;#xA0;31, 2019, the Company
 granted options to purchase 136,913 shares of common stock. As of
 March&amp;#xA0;31, 2019, total unrecognized compensation expense
 related to unvested stock options award was $5,066, which is
 expected to be recognized over a weighted average period of
 2.5&amp;#xA0;years.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Stock-based compensation expense was classified in the consolidated
 statements of operations and comprehensive loss as follows:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="80%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="8%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="8%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="6" align="center"&gt;&lt;b&gt;Three Months Ended&lt;br /&gt;
 March&amp;#xA0;31,&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2019&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2018&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Research and development expense&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;84&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;38&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 General and administrative expense&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;178&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;90&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Total stock-based compensation&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;262&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;128&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 18pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/div&gt;</us-gaap:DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock>
  <dei:DocumentFiscalPeriodFocus contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_470EE7E7-439B-4FBC-A723-4B5D29736791_1_4">Q1</dei:DocumentFiscalPeriodFocus>
  <dei:DocumentFiscalYearFocus contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_470EE7E7-439B-4FBC-A723-4B5D29736791_1_3">2019</dei:DocumentFiscalYearFocus>
  <dei:DocumentType contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_470EE7E7-439B-4FBC-A723-4B5D29736791_1_0">10-Q</dei:DocumentType>
  <us-gaap:DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_B1F6E9BB-9A14-4BAA-81DD-4E2A813EDBD9_1_0">&lt;div&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;&lt;b&gt;10.&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;&lt;b&gt;Preferred and Common Stock Warrants&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 As of March&amp;#xA0;31, 2019, the Company&amp;#x2019;s outstanding warrants
 to purchase shares of common stock consisted of the following:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="80%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="60%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="3%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="3%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="3%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="3%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; BORDER-BOTTOM: rgb(0,0,0) 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell"&gt;
 &lt;b&gt;Issuance Date&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Number&amp;#xA0;of&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Shares of&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Common&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Stock&amp;#xA0;Issuable&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Exercise&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Price&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Classification&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Expiration&amp;#xA0;Date&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 August&amp;#xA0;14, 2015&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;81,228&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;21.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;August&amp;#xA0;14,&amp;#xA0;2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 August&amp;#xA0;21, 2015&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;69,603&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;21.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;August&amp;#xA0;21, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 October&amp;#xA0;25, 2016&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5,155&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;24, 2026&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 November&amp;#xA0;1, 2017&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;130,609&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;31,&amp;#xA0;2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 November&amp;#xA0;17, 2017&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,442&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;November&amp;#xA0;16, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 December&amp;#xA0;4, 2017&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5,661&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;3, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 December&amp;#xA0;28, 2017&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;6,925&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;27, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 December&amp;#xA0;28, 2017&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;115,916&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;28, 2027&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 September&amp;#xA0;12, 2018&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;25,275&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;September&amp;#xA0;12,&amp;#xA0;2021&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 September&amp;#xA0;12, 2018&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;20,220&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;September&amp;#xA0;12, 2028&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 October&amp;#xA0;19, 2018&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;20,016&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;19, 2028&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 December&amp;#xA0;11, 2018&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5,004&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.80&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;19, 2028&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;494,054&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 As of December&amp;#xA0;31, 2018, the Company&amp;#x2019;s outstanding
 warrants to purchase shares of preferred stock (which converted
 into warrants to purchase common stock upon close of the Merger)
 consisted of the following (not adjusted for the Reverse Stock
 Split or Exchange Ratio):&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="32%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="24" nowrap="nowrap" align="center"&gt;
 &lt;p style="MARGIN-BOTTOM: 1pt; FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="center"&gt;&lt;b&gt;December&amp;#xA0;31, 2018&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 9pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 9pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; BORDER-BOTTOM: rgb(0,0,0) 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell"&gt;
 &lt;b&gt;Warrant Name&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Issuance Date&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Number&amp;#xA0;of&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Shares of&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Preferred&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Stock&amp;#xA0;Issuable&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Exercise&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Price&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Exercisable&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;for&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Classification&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Expiration Date&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series A warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;August&amp;#xA0;14, 2015&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;854,785&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2.07&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series&amp;#xA0;A&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;August&amp;#xA0;14, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series A warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;August&amp;#xA0;21, 2015&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;732,453&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2.07&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series A&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;August&amp;#xA0;21, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 SVB warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;25, 2016&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;54,256&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series A&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;24, 2026&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;November&amp;#xA0;1, 2017&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,374,435&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;31, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;November&amp;#xA0;17, 2017&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;88,845&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;November&amp;#xA0;16, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;4, 2017&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;59,576&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;3, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;28, 2017&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;72,875&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;27, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;28, 2017&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,219,815&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;28, 2027&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;September&amp;#xA0;12, 2018&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;265,957&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;September&amp;#xA0;12,&amp;#xA0;2021&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;September&amp;#xA0;12,&amp;#xA0;2018&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;212,765&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;September&amp;#xA0;12, 2028&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;19, 2018&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;210,638&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;19, 2028&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5,146,400&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Prior to the Merger, the Company classified its preferred stock
 warrants as a liability on its consolidated balance sheet because
 the warrants are freestanding financial instruments that may have
 required the Company to transfer assets upon exercise. The
 liability associated with each of these warrants was initially
 recorded at fair value upon the issuance date of each warrant and
 is subsequently remeasured to fair value as a component of other
 income (expense), net in the consolidated statement of operations
 and comprehensive loss. Upon the closing of the Merger with Arsanis
 (see Note 1), pursuant to the Merger Agreement, all of the
 outstanding X4 preferred stock was converted to Arsanis common
 stock and the X4 preferred stock warrants converted to warrants for
 the purchase of Arsanis common stock. The Company assessed the
 features of the warrants and determined that they qualify for
 classification as permanent equity upon the closing of the Merger.
 Accordingly, the Company remeasured the warrants to fair value upon
 the closing of the Merger, which was $5,235 at March&amp;#xA0;13, 2019,
 with $288 of expense recorded during the three months ended
 March&amp;#xA0;31, 2019. Upon the closing of the Merger, the warrant
 liability was reclassified to
 additional&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;paid-in&lt;/font&gt;&amp;#xA0;capital.&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/p&gt;
 &lt;/div&gt;</us-gaap:DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock>
  <us-gaap:DerivativesPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_467C5F28-2840-4DD1-A705-DAFA62AE4E98_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Derivative Liability&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company&amp;#x2019;s license agreement with Genzyme Corporation
 (&amp;#x201C;Genzyme&amp;#x201D;) (see Note&amp;#xA0;13) contained a contingent
 payment obligation that required the Company to make a cash payment
 to Genzyme upon a change of control event of the Company. The
 contingent payment obligation met the definition of a derivative
 instrument as the contingent payment obligation was not clearly and
 closely related to its host instrument and was a cash-settled
 liability. Accordingly, the Company classified this derivative as a
 liability within other liabilities &lt;font style="WHITE-SPACE: nowrap"&gt;(non-current)&lt;/font&gt; on its condensed
 consolidated balance sheet. The derivative liability was initially
 recorded at fair value on the date of entering into the license
 agreement and was subsequently remeasured to fair value at each
 reporting date. Changes in the fair value of this derivative
 liability were recognized as a component of other income (expense),
 net in the condensed consolidated statement of operations and
 comprehensive loss. The Merger with Arsanis (see Note 1) qualified
 as a change of control event, as defined in the license agreement,
 but resulted in no payment being due to Genzyme under the license
 agreement. As a result, on March&amp;#xA0;13, 2019, the closing date of
 the Merger with Arsanis, the derivative liability was remeasured to
 fair value, which was $0, and subsequent changes in fair value will
 no longer be recognized in the consolidated statements of
 operations and comprehensive loss because the contingent payment
 obligation to Genzyme expired at that time.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 12px"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt"&gt;
 In addition, the Company&amp;#x2019;s Hercules loan (see Note&amp;#xA0;7)
 contains a redemption feature that, upon an event of default,
 provides Hercules the option to accelerate and demand repayment of
 the debt, including a prepayment premium. The redemption feature
 meets the definition of a derivative instrument as the repayment of
 the debt contains a substantial premium, resulting in the
 redemption feature not being clearly and closely related to its
 host instrument. Accordingly, the Company classifies this
 derivative as a liability within other liabilities &lt;font style="WHITE-SPACE: nowrap"&gt;(non-current)&lt;/font&gt; on its condensed
 consolidated balance sheet. The derivative liability was initially
 recorded at fair value on the date of entering into the Hercules
 Loan Agreement and is subsequently remeasured to fair value at each
 reporting date. Changes in the fair value of this derivative
 liability are recognized as a component of other income (expense),
 net in the condensed consolidated statement of operations and
 comprehensive loss. Changes in the fair value of this derivative
 liability will continue to be recognized until all amounts
 outstanding under the Hercules Loan Agreement are repaid or until
 the Hercules Loan Agreement is terminated.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:DerivativesPolicyTextBlock>
  <us-gaap:EarningsPerShareBasicAndDiluted contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="2" id="id_13073811_29777C2D-E0DB-433D-BA39-674C4E97CEBC_1_14" unitRef="iso4217_USD_per_shares">-6.67</us-gaap:EarningsPerShareBasicAndDiluted>
  <us-gaap:EarningsPerShareTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_0674FE8D-158C-4E34-A6D8-10D440569640_1_0">&lt;div&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;&lt;b&gt;15.&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;&lt;b&gt;Net Loss per Share&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Basic and diluted net loss per share attributable to common
 stockholders was calculated as follow:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="75%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="6%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="6%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="6" align="center"&gt;&lt;b&gt;Three Months Ended&lt;br /&gt;
 March&amp;#xA0;31,&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2019&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2018&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Numerator:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 5em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Net loss&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(10,873&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(7,367&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 5em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Accruing dividends on Series A convertible preferred stock&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(592&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(740&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 5em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Net loss attributable to common stockholders&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(11,465&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(8,107&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Denominator:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Weighted average common shares outstanding&amp;#x2014;basic and
 diluted&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,717,808&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;457,971&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Net loss per share attributable to common stockholders&amp;#x2014;basic
 and diluted&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(6.67&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(17.70&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The Company has included 107,371 shares of redeemable common stock
 in its computation of basic and diluted weighted average common
 shares outstanding for the three months ended March&amp;#xA0;31, 2019
 and 2018 as this class of stock participates in losses similarly to
 other common stockholders.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The Company&amp;#x2019;s potentially dilutive securities included
 outstanding stock options, convertible preferred stock, and
 warrants to purchase shares of convertible preferred stock for the
 three month period ended March&amp;#xA0;31, 2018 and included
 outstanding stock options and warrants to purchase common stock for
 the three month period ended March&amp;#xA0;31, 2019. These potentially
 dilutive securities have been excluded from the computation of
 diluted net loss per share as the effect would be to reduce the net
 loss per share, and thus they are considered
 &amp;#x201C;anti-dilutive.&amp;#x201D; Therefore, the weighted average number
 of common shares outstanding used to calculate both basic and
 diluted net loss per share attributable to common stockholders is
 the same. The Company excluded the following potential common
 shares, presented based on amounts outstanding at each period end
 and adjusted for the Exchange Ratio and Reverse Stock Split, from
 the computation of diluted net loss per share attributable to
 common stockholders for the periods indicated because including
 them would have had an anti-dilutive effect:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="76%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="3%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="3%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="6" align="center"&gt;&lt;b&gt;Three Months Ended&lt;br /&gt;
 March&amp;#xA0;31,&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2019&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2018&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Options to purchase common stock&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,037,089&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;538,429&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Convertible preferred stock (as converted to common stock)&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;3,556,147&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Warrants to purchase common stock (presented on
 an&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;as-converted,&lt;/font&gt;&amp;#xA0;as
 exchanged, split-adjusted basis.&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;493,927&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;423,416&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,531,016&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,517,992&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 18pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/div&gt;</us-gaap:EarningsPerShareTextBlock>
  <us-gaap:EarningsPerSharePolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_22AA276E-CF4A-4196-A5D7-0FB4C67A513E_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Net Income (Loss) per Share&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company follows the &lt;font style="WHITE-SPACE: nowrap"&gt;two-class&lt;/font&gt; method when computing net
 income (loss) per share as the Company has issued shares that meet
 the definition of participating securities. The &lt;font style="WHITE-SPACE: nowrap"&gt;two-class&lt;/font&gt; method determines net income
 (loss) per share for each class of common and participating
 securities according to dividends declared or accumulated and
 participation rights in undistributed earnings. The &lt;font style="WHITE-SPACE: nowrap"&gt;two-class&lt;/font&gt; method requires income
 available to common stockholders for the period to be allocated
 between common and participating securities based upon their
 respective rights to receive dividends as if all income for the
 period had been distributed.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Basic net income (loss) per share attributable to common
 stockholders is computed by dividing the net income (loss)
 attributable to common stockholders by the weighted average number
 of common shares outstanding for the period. Diluted net income
 (loss) attributable to common stockholders is computed by adjusting
 net income (loss) attributable to common stockholders to reallocate
 undistributed earnings based on the potential impact of dilutive
 securities. Diluted net income (loss) per share attributable to
 common stockholders is computed by dividing the diluted net income
 (loss) attributable to common stockholders by the weighted average
 number of common shares outstanding for the period, including
 potential dilutive common shares. For purpose of this calculation,
 outstanding stock options, convertible preferred stock and warrants
 to purchase shares of convertible preferred stock are considered
 potential dilutive common shares.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company&amp;#x2019;s convertible preferred stock contractually
 entitles the holders of such shares to participate in dividends but
 does not contractually require the holders of such shares to
 participate in losses of the Company. Accordingly, in periods in
 which the Company reports a net loss attributable to common
 stockholders, such losses are not allocated to such participating
 securities. In periods in which the Company reports a net loss
 attributable to common stockholders, diluted net loss per share
 attributable to common stockholders is the same as basic net loss
 per share attributable to common stockholders, since dilutive
 common shares are not assumed to have been issued if their effect
 is anti-dilutive. The Company reported a net loss attributable to
 common stockholders for the three months ended March&amp;#xA0;31, 2019
 and 2018.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:EarningsPerSharePolicyTextBlock>
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  <dei:EntitySmallBusiness contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_A7F8FC82-9EF2-433E-A4E3-49D3C0BA9AB7_1_5">true</dei:EntitySmallBusiness>
  <us-gaap:FairValueDisclosuresTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_F7CD5474-1557-4081-9043-E36F3D2463BE_1_0">&lt;div&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;&lt;b&gt;4.&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;&lt;b&gt;Fair Value of Financial Assets and
 Liabilities&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The following tables present information about the Company&amp;#x2019;s
 financial assets and liabilities measured at fair value on a
 recurring basis and indicate the level of the fair value hierarchy
 used to determine such fair values:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="92%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="60%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="4%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="4%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="4%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="4%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="14" align="center"&gt;&lt;b&gt;Fair Value Measurements as of
 March&amp;#xA0;31, 2019 Using:&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Level&amp;#xA0;1&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Level&amp;#xA0;2&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Level&amp;#xA0;3&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Total&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Assets:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Cash equivalents&amp;#x2014;money market funds&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;22,299&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;22,299&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;22,299&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;22,299&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Liabilities:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Preferred stock warrant liability&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Derivative liability&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;18&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;18&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;18&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;18&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="92%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="61%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="6%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="6%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="6%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="6%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="14" align="center"&gt;&lt;b&gt;Fair Value Measurements as of
 December&amp;#xA0;31, 2018 Using:&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Level&amp;#xA0;1&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Level&amp;#xA0;2&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Level&amp;#xA0;3&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Total&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Assets:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Cash equivalents&amp;#x2014;money market fund&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,134&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,134&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,134&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,134&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Liabilities:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Preferred stock warrant liability&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,947&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,947&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Derivative liability&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;201&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;201&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5,148&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5,148&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 As of March&amp;#xA0;31, 2019 and December&amp;#xA0;31, 2018, there were no
 transfers between Level&amp;#xA0;1, Level&amp;#xA0;2 and Level&amp;#xA0;3.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The Company&amp;#x2019;s cash equivalents consisted of a money market
 fund invested in U.S. Treasury securities. The money market fund
 was valued using inputs observable in active markets for similar
 securities, which represents a Level&amp;#xA0;2 measurement in the fair
 value hierarchy.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Valuation of Preferred Stock Warrant Liabilities&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The preferred stock warrant liability in the table above consists
 of the fair values of (i)&amp;#xA0;warrants to purchase shares of
 Series&amp;#xA0;A convertible preferred stock that were issued in 2015
 and shares of Series&amp;#xA0;B convertible preferred stock that were
 issued in 2017 and 2018 in connection with the Company&amp;#x2019;s
 Series&amp;#xA0;A and Series&amp;#xA0;B convertible preferred stock
 financings, respectively (see Notes&amp;#xA0;10), (ii)&amp;#xA0;warrants to
 purchase shares of Series&amp;#xA0;A convertible preferred stock that
 were issued in 2016 in connection with the Company&amp;#x2019;s entering
 into a loan and security agreement with Silicon Valley Bank (see
 Note&amp;#xA0;7) and (iii)&amp;#xA0;warrants to purchase shares of
 Series&amp;#xA0;B convertible preferred stock that were issued or were
 issuable in 2018 in connection with the Company&amp;#x2019;s entering
 into the Hercules Loan Agreement (see Note&amp;#xA0;7). The liability
 associated with the warrants was recorded at fair value on the
 dates the warrants were issued and exercisable and was subsequently
 remeasured to fair value at each reporting date through
 December&amp;#xA0;31, 2018. Upon the closing of the Merger, all X4
 preferred stock warrants were converted to warrants for
 Company&amp;#x2019;s common stock and, as a result, the warrants were
 adjusted to fair value and reclassified to permanent equity. The
 aggregate fair value of the warrant liability was determined based
 on significant inputs not observable in the market, which
 represents a Level&amp;#xA0;3 measurement within the fair value
 hierarchy.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The Company used various valuation methods, including the Monte
 Carlo method, the option-pricing method and the hybrid method
 (which is a combination of an option-pricing method and a
 probability-weighted expected return method), all of which
 incorporate assumptions and estimates, to value the preferred stock
 warrants. Estimates and assumptions impacting the fair value
 measurement include the fair value per share of the underlying
 shares of the Company&amp;#x2019;s Series&amp;#xA0;A and Series&amp;#xA0;B
 convertible preferred stock, risk free interest rate, expected
 dividend yield, expected volatility of the price of the underlying
 preferred stock, and either the remaining contractual term of the
 warrants (except for warrants that would be automatically exercised
 upon an initial public offering, in which case the remaining
 estimated term to automatic exercise was used). The most
 significant assumption in the Monte Carlo method, the
 option-pricing method and the hybrid method impacting the fair
 value of the preferred stock warrants is the fair value of the
 Company&amp;#x2019;s convertible preferred stock as of each
 remeasurement date. The Company determines the fair value per share
 of the underlying preferred stock by taking into consideration the
 most recent sales of its convertible preferred stock, results
 obtained from third-party valuations and additional factors that
 are deemed relevant. As of December&amp;#xA0;31, 2018, the fair value
 of the Series&amp;#xA0;A convertible preferred stock was $1.70&amp;#xA0;per
 share the fair value of the Series&amp;#xA0;B convertible preferred
 stock was $1.86&amp;#xA0;per share. There were no warrants for the
 purchase of convertible preferred shares as of March&amp;#xA0;31, 2019
 as all such warrants were converted to warrants for the purchase of
 common stock upon the Merger. The Company has been a private
 company prior to the Merger and lacks company-specific historical
 and implied volatility information of its stock. Therefore, it
 estimates its expected stock volatility based on the historical
 volatility of publicly traded peer companies for a term equal to
 the estimated remaining term of the warrants. The risk-free
 interest rate is determined by reference to the U.S. Treasury yield
 curve for time periods approximately equal to the estimated
 remaining term of the warrants. The Company estimated a 0% expected
 dividend yield based on the fact that the Company has never paid or
 declared dividends and does not intend to do so in the foreseeable
 future.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Valuation of Derivative Liability&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The fair value of the derivative liability recognized in connection
 with the Company&amp;#x2019;s July 2014 license agreement with Genzyme
 (see Note&amp;#xA0;13) was determined based on significant inputs not
 observable in the market, which represents a Level&amp;#xA0;3
 measurement within the fair value hierarchy. The fair value of this
 derivative liability is reported within other liabilities on the
 consolidated balance sheets. The fair value of this derivative
 liability was estimated by the Company at each reporting date
 based, in part, on the results of third-party valuations, which
 were prepared using the option-pricing method or the hybrid method,
 each of which considered as inputs the type, timing and probability
 of occurrence of a change of control event, the potential amount of
 the payment under potential exit scenarios, the fair value per
 share of the underlying common stock and the risk-adjusted discount
 rate. As of December&amp;#xA0;31, 2018, the fair value of this
 derivative liability was $183. The Merger with Arsanis (see Note 1)
 qualified as a change of control event, as defined in the license
 agreement, but results in no payment being due to Genzyme under the
 license agreement. As a result, on March&amp;#xA0;13, 2019, the closing
 date of the Merger with Arsanis, this derivative liability was
 remeasured to fair value, which was $0, and subsequent changes in
 fair value will no longer be recognized in the consolidated
 statements of operations and comprehensive loss because the
 contingent payment obligation to Genzyme expired at that time.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The fair value of the derivative liability recognized in connection
 with the Hercules Loan Agreement (see Note&amp;#xA0;7) was determined
 based on significant inputs not observable in the market, which
 represents a Level&amp;#xA0;3 measurement within the fair value
 hierarchy. The fair value of this derivative liability is reported
 within other liabilities on the consolidated balance sheets. The
 fair value of this derivative liability was estimated by the
 Company at each reporting date based, in part, on the results of
 third-party valuations, which were prepared based on a discounted
 cash flow model that considered the timing and probability of
 occurrence of a redemption upon an event of default, the potential
 amount of prepayment upon an event of default and the risk-adjusted
 discount rate. As of March&amp;#xA0;31, 2019 and December&amp;#xA0;31,
 2018, the fair value of this derivative liability was
 immaterial.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The following table provides a roll-forward of the aggregate fair
 values of the Company&amp;#x2019;s warrant liability, derivative
 liability and preferred stock repurchase liability, for which fair
 values are determined using Level&amp;#xA0;3 inputs:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="74%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="9%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="9%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Preferred&amp;#xA0;Stock&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Warrant&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Liability&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Derivative&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Liability&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Balance as of December&amp;#xA0;31, 2018&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,947&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;201&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Change in fair value&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;288&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(183&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Conversion of convertible preferred stock warrant into common stock
 warrant in connection with Merger&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(5,235&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Balance as of March&amp;#xA0;31, 2019&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;18&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 18pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/div&gt;</us-gaap:FairValueDisclosuresTextBlock>
  <us-gaap:DividendsCommonStock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="0" id="id_13073811_1AB6290E-7443-4606-BB16-B76C5E212DFB_1_2" unitRef="iso4217_USD">0</us-gaap:DividendsCommonStock>
  <dei:DocumentPeriodEndDate contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_470EE7E7-439B-4FBC-A723-4B5D29736791_1_2">2019-03-31</dei:DocumentPeriodEndDate>
  <dei:EntityEmergingGrowthCompany contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_A7F8FC82-9EF2-433E-A4E3-49D3C0BA9AB7_1_6">true</dei:EntityEmergingGrowthCompany>
  <dei:EntityExTransitionPeriod contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_A7F8FC82-9EF2-433E-A4E3-49D3C0BA9AB7_1_7">true</dei:EntityExTransitionPeriod>
  <dei:EntityFilerCategory contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_A7F8FC82-9EF2-433E-A4E3-49D3C0BA9AB7_1_4">Non-accelerated Filer</dei:EntityFilerCategory>
  <us-gaap:FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_3EA4F176-9776-41B7-BF24-4EF6EB7FAC2E_1_0">&lt;div&gt;
 &lt;p style="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"&gt;
 The following table provides a roll-forward of the aggregate fair
 values of the Company&amp;#x2019;s warrant liability, derivative
 liability and preferred stock repurchase liability, for which fair
 values are determined using Level&amp;#xA0;3 inputs:&lt;/p&gt;
 &lt;p style="font-size:12pt;margin-top:0pt;margin-bottom:0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table cellspacing="0" cellpadding="0" width="76%" border="0" style="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" align="center"&gt;
 &lt;tr&gt;
 &lt;td width="74%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="9%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="9%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" colspan="2" align="center" style="border-bottom:1.00pt solid #000000"&gt;
 &lt;b&gt;Preferred&amp;#xA0;Stock&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Warrant&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Liability&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" colspan="2" align="center" style="border-bottom:1.00pt solid #000000"&gt;&lt;b&gt;Derivative&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Liability&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr bgcolor="#CCEEFF" style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt"&gt;
 &lt;td valign="top"&gt;
 &lt;p style=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"&gt;
 Balance as of December&amp;#xA0;31, 2018&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,947&lt;/td&gt;
 &lt;td nowrap="nowrap" valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;201&lt;/td&gt;
 &lt;td nowrap="nowrap" valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt"&gt;
 &lt;td valign="top"&gt;
 &lt;p style=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"&gt;
 Change in fair value&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;288&lt;/td&gt;
 &lt;td nowrap="nowrap" valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(183&lt;/td&gt;
 &lt;td nowrap="nowrap" valign="bottom"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr bgcolor="#CCEEFF" style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt"&gt;
 &lt;td valign="top"&gt;
 &lt;p style=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"&gt;
 Conversion of convertible preferred stock warrant into common stock
 warrant in connection with Merger&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(5,235&lt;/td&gt;
 &lt;td nowrap="nowrap" valign="bottom"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td nowrap="nowrap" valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td nowrap="nowrap" valign="bottom" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td nowrap="nowrap" valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="font-size:1px;"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt"&gt;
 &lt;td valign="top"&gt;
 &lt;p style=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman"&gt;
 Balance as of March&amp;#xA0;31, 2019&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td nowrap="nowrap" valign="bottom"&gt;$&lt;/td&gt;
 &lt;td nowrap="nowrap" valign="bottom" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td nowrap="nowrap" valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;18&lt;/td&gt;
 &lt;td nowrap="nowrap" valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="font-size:1px;"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;/div&gt;</us-gaap:FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock>
  <us-gaap:FairValueAdjustmentOfWarrants contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_29777C2D-E0DB-433D-BA39-674C4E97CEBC_1_8" unitRef="iso4217_USD">288000</us-gaap:FairValueAdjustmentOfWarrants>
  <us-gaap:FairValueAssetsMeasuredOnRecurringBasisTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_147D9B47-17EA-4969-BF96-2BB94A263733_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The following tables present information about the Company&amp;#x2019;s
 financial assets and liabilities measured at fair value on a
 recurring basis and indicate the level of the fair value hierarchy
 used to determine such fair values:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="92%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="60%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="4%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="4%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="4%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="4%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="14" align="center"&gt;&lt;b&gt;Fair Value Measurements as of
 March&amp;#xA0;31, 2019 Using:&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Level&amp;#xA0;1&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Level&amp;#xA0;2&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Level&amp;#xA0;3&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Total&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Assets:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Cash equivalents&amp;#x2014;money market funds&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;22,299&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;22,299&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;22,299&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;22,299&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Liabilities:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Preferred stock warrant liability&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Derivative liability&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;18&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;18&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;18&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;18&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="92%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="61%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="6%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="6%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="6%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="6%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="14" align="center"&gt;&lt;b&gt;Fair Value Measurements as of
 December&amp;#xA0;31, 2018 Using:&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Level&amp;#xA0;1&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Level&amp;#xA0;2&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Level&amp;#xA0;3&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;Total&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Assets:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Cash equivalents&amp;#x2014;money market fund&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,134&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,134&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,134&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,134&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Liabilities:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Preferred stock warrant liability&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,947&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,947&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Derivative liability&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;201&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;201&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5,148&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5,148&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;br class="Apple-interchange-newline" /&gt;&lt;/div&gt;</us-gaap:FairValueAssetsMeasuredOnRecurringBasisTextBlock>
  <us-gaap:FairValueMeasurementPolicyPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_4A6FBE76-415C-4AF4-B576-4C658A4DA9E6_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Fair Value Measurements&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Certain assets and liabilities of the Company are carried at fair
 value under GAAP. Fair value is defined as the exchange price that
 would be received for an asset or paid to transfer a liability (an
 exit price) in the principal or most advantageous market for the
 asset or liability in an orderly transaction between market
 participants on the measurement date. Valuation techniques used to
 measure fair value must maximize the use of observable inputs and
 minimize the use of unobservable inputs. Financial assets and
 liabilities carried at fair value are to be classified and
 disclosed in one of the following three levels of the fair value
 hierarchy, of which the first two are considered observable and the
 last is considered unobservable:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;Level 1&amp;#x2014;Quoted prices in active markets for
 identical assets or liabilities.&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;Level 2&amp;#x2014;Observable inputs (other than
 Level&amp;#xA0;1 quoted prices), such as quoted prices in active
 markets for similar assets or liabilities, quoted prices in markets
 that are not active for identical or similar assets or liabilities,
 or other inputs that are observable or can be corroborated by
 observable market data.&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;Level 3&amp;#x2014;Unobservable inputs that are supported
 by little or no market activity that are significant to determining
 the fair value of the assets or liabilities, including pricing
 models, discounted cash flow methodologies and similar
 techniques.&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Prior to the Merger, the Company&amp;#x2019;s preferred stock warrant
 liability, derivative liability and preferred stock repurchase
 liability were carried at fair value, determined according to
 Level&amp;#xA0;3 inputs in the fair value hierarchy described above
 (See Note&amp;#xA0;4). The Company&amp;#x2019;s cash equivalents, consisting
 of money market funds invested in U.S. Treasury securities, are
 carried at fair value, determined based on Level&amp;#xA0;2 inputs in
 the fair value hierarchy described above (see Note 4). The carrying
 values of the Company&amp;#x2019;s accounts payable and accrued expenses
 approximate their fair values due to the short-term nature of these
 liabilities. The carrying value of the Company&amp;#x2019;s outstanding
 loan and security agreement (the &amp;#x201C;Hercules Loan
 Agreement&amp;#x201D;) with Hercules Capital, Inc.
 (&amp;#x201C;Hercules&amp;#x201D;) approximates its fair value at
 March&amp;#xA0;31, 2019 because the debt bears interest at a variable
 market rate and the Company&amp;#x2019;s credit risk has not materially
 changed since the inception of the agreement. The carrying value of
 the Company&amp;#x2019;s loans under the funding agreements with
 &amp;#xD6;sterreichische Forschungsf&amp;#xF6;rderungsgesellschaft mbH
 (&amp;#x201C;FFG&amp;#x201D;) were recorded at fair value on the opening
 balance sheet of Arsanis as of the date of the Merger, and
 approximates the fair value of the loans at March&amp;#xA0;31, 2019.
 (See Note&amp;#xA0;3).&lt;/p&gt;
 &lt;/div&gt;</us-gaap:FairValueMeasurementPolicyPolicyTextBlock>
  <us-gaap:FairValueOptionChangesInFairValueGainLoss1 contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_982572EB-3106-47D8-8A45-438E1833C2AC_2_1" unitRef="iso4217_USD">288000</us-gaap:FairValueOptionChangesInFairValueGainLoss1>
  <us-gaap:ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_E0EE4790-F1BE-425E-B3E9-54D7742BD6F8_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Foreign Currency and Currency Translation&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Management has determined that the functional currency for the
 Company&amp;#x2019;s wholly owned foreign subsidiary, Arsanis
 Biosciences GmbH, is the Euro. Management&amp;#x2019;s assessment
 considered the currency environment in which the entity operates,
 including inflows of cash from research and development incentive
 programs and outflows of cash for operating expenditure.
 Accordingly, the assets and liabilities of Arsanis Biosciences GmbH
 are translated from the Euro into United States dollars at the
 exchange rate in effect on the balance sheet date and income and
 expenses are translated at the average exchange rate in effect
 during the period. Unrealized translation gains and losses are
 recorded as a cumulative translation adjustment, which is included
 in the consolidated balance sheet as a component of accumulated
 other comprehensive income (loss). Adjustments that arise from
 exchange rate changes on transactions denominated in a currency
 other than the Euro are included in other income (expense), net in
 the consolidated statements of operations as incurred.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock>
  <us-gaap:GoodwillAndIntangibleAssetsGoodwillPolicy contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_22145A3B-93B1-4A64-93AD-10584FD3C2C8_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Goodwill&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Business combinations are accounted for under the acquisition
 method. The total purchase price of an acquisition is allocated to
 the underlying identifiable net assets, based on their respective
 estimated fair values as of the acquisition date. Determining the
 fair value of assets acquired and liabilities assumed requires
 management&amp;#x2019;s judgment and often involves the use of
 significant estimates and assumptions, including assumptions with
 respect to future cash inflows and outflows, probabilities of
 success, discount rates, and asset lives, among other items. Assets
 acquired and liabilities assumed are recorded at their estimated
 fair values. The excess of the purchase price over the estimated
 fair values of the net assets acquired is recorded as goodwill.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Goodwill is tested for impairment at the reporting unit level
 annually in the fourth quarter, or more frequently when events or
 changes in circumstances indicate that the asset might be impaired.
 Examples of such events or circumstances include, but are not
 limited to, a significant adverse change in legal or business
 climate, an adverse regulatory action or unanticipated competition.
 The Company has determined that it operates in a single operating
 segment and has a single reporting unit.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company assesses qualitative factors to determine whether the
 existence of events or circumstances would indicate that it is more
 likely than not that the fair value of the reporting unit was less
 than its carrying amount. If after assessing the totality of events
 or circumstances, the Company were to determine that it is more
 likely than not that the fair value of the reporting unit is less
 than its carrying amount, then the Company would perform a
 quantitative impairment test.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company compares the fair value of the reporting unit to its
 carrying value. If the fair value of the reporting unit exceeds the
 carrying value of the net assets, goodwill is not impaired, and no
 further testing is required. If the fair value of the reporting
 unit is less than the carrying value, the Company measures the
 amount of impairment loss, if any, as the excess of the carrying
 value over the fair value of the reporting unit. The Company has
 determined there were no indicators of goodwill impairment as of
 March&amp;#xA0;31, 2019.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:GoodwillAndIntangibleAssetsGoodwillPolicy>
  <us-gaap:GeneralAndAdministrativeExpense contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_29777C2D-E0DB-433D-BA39-674C4E97CEBC_1_2" unitRef="iso4217_USD">4783000</us-gaap:GeneralAndAdministrativeExpense>
  <us-gaap:IncreaseDecreaseInAccountsPayable contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_11" unitRef="iso4217_USD">1332000</us-gaap:IncreaseDecreaseInAccountsPayable>
  <us-gaap:IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_10" unitRef="iso4217_USD">595000</us-gaap:IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets>
  <us-gaap:IncomeTaxDisclosureTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_20D6D57F-57BA-4C48-8520-F3D789AD7944_1_0">&lt;div&gt;
 &lt;table style="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" border="0" cellpadding="0" cellspacing="0" width="100%"&gt;
 &lt;tr style="page-break-inside:avoid"&gt;
 &lt;td width="4%" valign="top" align="left"&gt;&lt;b&gt;14.&lt;/b&gt;&lt;/td&gt;
 &lt;td align="left" valign="top"&gt;
 &lt;p style="margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman;" align="left"&gt;&lt;b&gt;Income Taxes&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"&gt;
 The Company did not record a federal or state income tax benefit
 for its losses for the three months ended March&amp;#xA0;31, 2019 and
 2018 due to the conclusion that a full valuation allowance is
 required against the Company&amp;#x2019;s deferred tax assets.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:IncomeTaxDisclosureTextBlock>
  <us-gaap:ImpairmentOrDisposalOfLongLivedAssetsPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_FBD6AB9D-BC79-430B-84ED-43EE80FDC501_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Impairment of Long-Lived Assets&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Long-lived assets consist of property and equipment. Long-lived
 assets to be held and used are tested for recoverability whenever
 events or changes in business circumstances indicate that the
 carrying amount of the assets may not be fully recoverable. Factors
 that the Company considers in deciding when to perform an
 impairment review include significant underperformance of the
 business in relation to expectations, significant negative industry
 or economic trends and significant changes or planned changes in
 the use of the assets. If an impairment review is performed to
 evaluate a long-lived asset group for recoverability, the Company
 compares forecasts of undiscounted cash flows expected to result
 from the use and eventual disposition of the long-lived asset group
 to its carrying value. An impairment loss would be recognized in
 loss from operations when estimated undiscounted future cash flows
 expected to result from the use of an asset group are less than its
 carrying amount. The impairment loss would be based on the excess
 of the carrying value of the impaired asset group over its fair
 value. To date, the Company has not recorded any impairment losses
 on long-lived assets.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:ImpairmentOrDisposalOfLongLivedAssetsPolicyTextBlock>
  <us-gaap:IncomeTaxPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_EBF57B20-5FF8-42C1-AE9F-F861402A6D59_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Income Taxes&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company accounts for income taxes using the asset and liability
 method, which requires the recognition of deferred tax assets and
 liabilities for the expected future tax consequences of events that
 have been recognized in the consolidated financial statements or in
 the Company&amp;#x2019;s tax returns. Deferred tax assets and
 liabilities are determined based on the difference between the
 financial statement and tax basis of assets and liabilities using
 enacted tax rates in effect for the year in which the differences
 are expected to reverse. Changes in deferred tax assets and
 liabilities are recorded in the provision for income taxes. The
 Company assesses the likelihood that its deferred tax assets will
 be recovered from future taxable income and, to the extent it
 believes, based upon the weight of available evidence, that it is
 more likely than not that all or a portion of the deferred tax
 assets will not be realized, a valuation allowance is established
 through a charge to income tax expense. Potential for recovery of
 deferred tax assets is evaluated by estimating the future taxable
 profits expected and considering prudent and feasible tax planning
 strategies.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company accounts for uncertainty in income taxes recognized in
 the consolidated financial statements by applying a &lt;font style="WHITE-SPACE: nowrap"&gt;two-step&lt;/font&gt; process to determine the
 amount of tax benefit to be recognized. First, the tax position
 must be evaluated to determine the likelihood that it will be
 sustained upon external examination by the taxing authorities. If
 the tax position is deemed &lt;font style="WHITE-SPACE: nowrap"&gt;more-likely-than-not&lt;/font&gt; to be sustained,
 the tax position is then assessed to determine the amount of
 benefit to recognize in the consolidated financial statements. The
 amount of the benefit that may be recognized is the largest amount
 that has a greater than 50% likelihood of being realized upon
 ultimate settlement. The provision for income taxes includes the
 effects of any resulting tax reserves, or unrecognized tax
 benefits, that are considered appropriate as well as the related
 net interest and penalties.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:IncomeTaxPolicyTextBlock>
  <us-gaap:IncreaseDecreaseInAccruedLiabilities contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_12" unitRef="iso4217_USD">-2072000</us-gaap:IncreaseDecreaseInAccruedLiabilities>
  <us-gaap:IntangibleAssetsFiniteLivedPolicyCostsIncurredToRenewOrExtend contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_02BF473D-E4E6-4F16-A6AD-ADC214A7318A_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Patent Costs&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 All patent-related costs incurred in connection with filing and
 prosecuting patent applications are expensed as incurred due to the
 uncertainty about the recovery of the expenditure. Amounts incurred
 are classified as general and administrative expenses.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:IntangibleAssetsFiniteLivedPolicyCostsIncurredToRenewOrExtend>
  <us-gaap:InterestExpense contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_29777C2D-E0DB-433D-BA39-674C4E97CEBC_1_7" unitRef="iso4217_USD">399000</us-gaap:InterestExpense>
  <us-gaap:InterestPaidNet contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_29" unitRef="iso4217_USD">243000</us-gaap:InterestPaidNet>
  <us-gaap:LesseeOperatingLeaseLiabilityMaturityTableTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_0FF94048-5C60-4AFE-B836-49AD5D3CED44_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Maturities of lease liabilities due under these lease agreements as
 of March&amp;#xA0;31, 2019 are as follows:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="81%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="14%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; BORDER-BOTTOM: rgb(0,0,0) 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell"&gt;
 &lt;b&gt;Maturity of lease liabilities&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Operating&amp;#xA0;Leases&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2019 (remainder of 2019)&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;837&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2020&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,281&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2021&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,304&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2022&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;970&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2023&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;489&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Thereafter&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Total lease payments&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,880&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Less: interest&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(764&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Total operating lease liabilities as of March&amp;#xA0;31, 2019&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,116&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;br class="Apple-interchange-newline" /&gt;&lt;/div&gt;</us-gaap:LesseeOperatingLeaseLiabilityMaturityTableTextBlock>
  <us-gaap:InvestmentIncomeInterest contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_29777C2D-E0DB-433D-BA39-674C4E97CEBC_1_6" unitRef="iso4217_USD">69000</us-gaap:InvestmentIncomeInterest>
  <us-gaap:LeasesOfLesseeDisclosureTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_F87B26AA-CDF1-4A4B-BE36-3ABD34732C15_1_0">&lt;div&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;&lt;b&gt;8.&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;&lt;b&gt;Leases&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Effective January&amp;#xA0;1, 2019, the Company adopted ASC 842 using
 the modified retrospective approach through a cumulative-effect
 adjustment and utilizing the effective date as its date of initial
 application, with prior periods unchanged and presented in
 accordance with the previous lease accounting guidance. Upon
 adoption, the Company recorded&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt;&amp;#xA0;assets
 of $2,026 and lease liabilities of $2,538, of which $1,925 was
 classified as&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-current&lt;/font&gt;&amp;#xA0;and $613
 as current. The difference between the value of
 the&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt;&amp;#xA0;asset
 and the lease liabilities relates to $512 of net deferred, accrued
 and prepaid rent that was reclassified against
 the&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt;&amp;#xA0;asset
 upon adoption of ASC 842 on January&amp;#xA0;1, 2019. The Company has
 lease agreements for its facilities in Cambridge, Massachusetts,
 which is the Company&amp;#x2019;s global headquarters, Vienna, Austria,
 which is the Company&amp;#x2019;s research and development center, and
 Waltham, Massachusetts, which is the former headquarters of
 Arsanis. The Company plans to sublease its Waltham, Massachusetts
 facility. There are no restrictions or financial covenants
 associated with any of the lease agreements.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;i&gt;Cambridge Lease&lt;/i&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In August 2017, the Company entered into a lease agreement for
 office space of approximately thirteen thousand square feet in
 Cambridge, Massachusetts (&amp;#x201C;Cambridge Lease&amp;#x201D;) which
 expires on July&amp;#xA0;31, 2022. The Cambridge lease includes an
 annual rent escalation clause and the Company has the option to
 extend the lease for one period of five additional years. Base rent
 is approximately $810 annually and the monthly rent expense is
 being recognized on a straight-line basis over the term of the
 lease. In addition to the base rent, the Company is also
 responsible for its share of operating expenses, electricity and
 real estate taxes, in accordance with the terms of lease. These
 costs are classified as variable lease payments and are not
 included in the determination of the
 leases&amp;#x2019;&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt;&amp;#xA0;operating
 assets or lease operating liabilities.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;i&gt;Waltham Lease&lt;/i&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 On March&amp;#xA0;13, 2019, as part of its Merger with Arsanis, the
 Company acquired an operating lease for approximately six thousand
 square feet of office space in Waltham, Massachusetts
 (&amp;#x201C;Waltham Lease&amp;#x201D;). The Waltham lease, as amended,
 commenced on January&amp;#xA0;1, 2019, and expires approximately 5
 years from the commencement date. The base rent is approximately
 $459 annually. In addition to the base rent, the Company is also
 responsible for its share of operating expenses, electricity and
 real estate taxes, in accordance with the terms of the Amended
 Lease Agreement. These costs are classified as variable lease
 payments and are not included in the determination of the
 leases&amp;#x2019;&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt;&amp;#xA0;assets
 or lease liabilities.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;i&gt;Vienna Lease&lt;/i&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 On March&amp;#xA0;13, 2019, as part of its Merger with Arsanis, the
 Company acquired an operating lease for approximately four hundred
 square meters of laboratory and office space in Vienna, Austria,
 which commenced on March&amp;#xA0;1, 2019, as amended, for a term of
 two years. The lease is cancellable by the Company upon three
 month&amp;#x2019;s notice with no penalty. The annual base rent is
 approximately $155. The Company has classified this lease as a
 short-term lease as it is not reasonably certain that the Company
 with not terminate the lease within one year and, accordingly, has
 not recorded a&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt;&amp;#xA0;asset.
 Accordingly, rent expense is recorded on a straight-line basis as
 incurred over the term of the lease.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 As the Company&amp;#x2019;s leases do not provide an implicit rate, the
 Company estimated the incremental borrowing rate in calculating the
 present value of the lease payments. The Company utilizes its
 incremental borrowing rates, which are the rates incurred to borrow
 on a collateralized basis over a similar term an amount equal to
 the lease payments in a similar economic environment.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The components of lease expense for the three months ended
 March&amp;#xA0;31, 2019 were as follows:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="72%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="25%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&lt;font style="FONT-SIZE: 10pt"&gt;&lt;b&gt;Lease Cost&lt;/b&gt;&lt;/font&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;For&amp;#xA0;the&amp;#xA0;three&amp;#xA0;months&amp;#xA0;ended&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;March&amp;#xA0;31, 2019&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Fixed operating lease cost&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;187&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Short-term lease costs&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Total lease expense&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;195&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 &lt;b&gt;Other information&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Cash paid for amounts included in the measurement of lease
 liabilities:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 5em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Operating cash flows from operating leases&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;201&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Leased assets obtained in exchange for new operating lease
 liabilities&amp;#xA0;(1)&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;781&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Weighted-average remaining lease term&amp;#x2014;operating leases&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;3.9&amp;#xA0;years&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Weighted-average discount rate&amp;#x2014;operating leases&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;9.0&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;%&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;(1)&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;Acquired in Merger with Arsanis&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Maturities of lease liabilities due under these lease agreements as
 of March&amp;#xA0;31, 2019 are as follows:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="81%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="14%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; BORDER-BOTTOM: rgb(0,0,0) 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell"&gt;
 &lt;b&gt;Maturity of lease liabilities&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Operating&amp;#xA0;Leases&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2019 (remainder of 2019)&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;837&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2020&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,281&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2021&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,304&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2022&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;970&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2023&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;489&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Thereafter&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Total lease payments&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,880&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Less: interest&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(764&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Total operating lease liabilities as of March&amp;#xA0;31, 2019&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,116&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The Company adopted ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2016-02&lt;/font&gt;&amp;#xA0;on
 January&amp;#xA0;1, 2019 as noted above, and as required, the following
 disclosure is provided for periods prior to adoption. Future annual
 minimum lease payments due under the Company&amp;#x2019;s operating
 leases as of December&amp;#xA0;31, 2018 were as follows:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="81%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="14%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; BORDER-BOTTOM: rgb(0,0,0) 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell"&gt;
 &lt;b&gt;Year Ending December&amp;#xA0;31,&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Operating&amp;#xA0;Leases&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2019&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;810&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2020&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;823&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2021&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;835&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2022&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;492&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Total&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2,960&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;br class="Apple-interchange-newline" /&gt;

 &lt;/div&gt;</us-gaap:LeasesOfLesseeDisclosureTextBlock>
  <us-gaap:LeaseCost contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_B25143D0-B17D-4DC9-8A68-2788822ABB32_1_2" unitRef="iso4217_USD">195000</us-gaap:LeaseCost>
  <us-gaap:LeaseCostTableTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_426CDC3B-833A-43FA-934F-38FE3920DD8E_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The components of lease expense for the three months ended
 March&amp;#xA0;31, 2019 were as follows:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="72%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="25%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&lt;font style="FONT-SIZE: 10pt"&gt;&lt;b&gt;Lease Cost&lt;/b&gt;&lt;/font&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;For&amp;#xA0;the&amp;#xA0;three&amp;#xA0;months&amp;#xA0;ended&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;March&amp;#xA0;31, 2019&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Fixed operating lease cost&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;187&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Short-term lease costs&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Total lease expense&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;195&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 &lt;b&gt;Other information&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Cash paid for amounts included in the measurement of lease
 liabilities:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 5em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Operating cash flows from operating leases&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;201&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Leased assets obtained in exchange for new operating lease
 liabilities&amp;#xA0;(1)&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;781&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Weighted-average remaining lease term&amp;#x2014;operating leases&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;3.9&amp;#xA0;years&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Weighted-average discount rate&amp;#x2014;operating leases&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;9.0&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;%&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;(1)&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;Acquired in Merger with Arsanis&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;/div&gt;</us-gaap:LeaseCostTableTextBlock>
  <us-gaap:LongTermDebtTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_9EE45AD5-0E67-4098-A86B-9D446A5E9E50_1_0">&lt;div&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;&lt;b&gt;7.&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;&lt;b&gt;Long-Term Debt&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Long-term debt consisted of the following:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="72%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="8%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="8%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;March&amp;#xA0;31,&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;2019&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;December&amp;#xA0;31,&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;2018&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Principal amount of long-term debt&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19,546&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;10,000&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Less: Current portion of long-term debt&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(5,298&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(1,687&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Long-term debt, net of current portion&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;14,248&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,313&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Debt discount, net of accretion&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(1,019&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(226&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Cumulative accretion of final payment due at maturity&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;136&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;58&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Long-term debt, including accretion, net of current portion&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;13,365&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,145&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;SVB Loan Agreement&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In October 2016, the Company entered into a loan and security
 agreement with Silicon Valley Bank (&amp;#x201C;SVB&amp;#x201D;), which the
 Company refers to as the SVB Loan Agreement, pursuant to which SVB
 made certain term loans available to the Company. The SVB Loan
 Agreement provided for a term loan of up to $6,000, which was
 borrowed by the Company in June&amp;#xA0;2017. Borrowings under the SVB
 Loan Agreement bore interest at a variable rate equal to 5.5% plus
 the greater of (i)&amp;#xA0;3.5% or (ii)&amp;#xA0;The Wall Street Journal
 prime rate. In October 2018, in connection with entering into the
 Hercules Loan Agreement, the Company terminated the SVB Loan
 Agreement and repaid all amounts due under the SVB Loan Agreement,
 including unpaid principal of $4,333, a final payment of $270, a
 prepayment premium of $87 and accrued interest of $23. The Company
 accounted for the repayment of amounts as an extinguishment of the
 SVB Loan Agreement and recognized a loss on extinguishment of debt
 of $229 within other income (expense), net in the consolidated
 statement of operations and comprehensive loss. The loss on
 extinguishment of debt was calculated as the difference between the
 reacquisition price of the borrowings under the SVB Loan Agreement
 of $4,713 and the carrying value of the debt under the SVB Loan
 Agreement of $4,484. As of October&amp;#xA0;19, 2018, the date of
 repayment of all borrowings under the SVB Loan&amp;#xA0;Agreement, the
 interest rate applicable to borrowings under the SVB Loan Agreement
 was 10.75%.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Hercules Loan Agreement&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In October 2018, the Company entered into the Hercules Loan
 Agreement, which provided for aggregate borrowings of up to
 $13,000, consisting of (i)&amp;#xA0;a term loan of up to $8,000, which
 was available upon entering into the agreement, (ii)&amp;#xA0;subject
 to specified financing conditions, an additional term loan of up to
 $2,000, available for borrowing from January&amp;#xA0;1, 2019 to
 March&amp;#xA0;31, 2019, and (iii)&amp;#xA0;subject to specified financing
 conditions and the receipt of the second tranche $2,000 term loan
 described above, an additional term loan of up to $3,000, available
 for borrowing until March&amp;#xA0;31, 2019. In October 2018, the
 Company borrowed $8,000 under the Hercules Loan Agreement.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In December 2018, the Company entered into the First Amendment to
 the Hercules Loan Agreement (the &amp;#x201C;First Amendment&amp;#x201D;),
 which amended the available borrowing dates of the second tranche
 from between January&amp;#xA0;1, 2019 and March&amp;#xA0;31, 2019 to
 between December&amp;#xA0;11, 2018 and December&amp;#xA0;14, 2018 and
 amended the term loan maturity date to November&amp;#xA0;1, 2021. In
 December 2018, the Company borrowed the additional $2,000 provided
 under the Hercules Loan Agreement, as amended by the First
 Amendment.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In March&amp;#xA0;2019, the conditions necessary for borrowing the
 remaining $3,000 under the Hercules Loan Agreement were not met and
 the borrowing capacity expired at that time.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Borrowings under the Hercules Loan Agreement bear interest at
 variable rates, with the first tranche bearing interest at a
 variable rate equal to the greater of (i)&amp;#xA0;9.5% or
 (ii)&amp;#xA0;9.5% plus&lt;i&gt;&amp;#xA0;The Wall Street
 Journal&lt;/i&gt;&amp;#xA0;prime rate minus 5.25%, the second
 tranche bearing interest at a variable rate, subject to completion
 of specified financing conditions, equal to either (A)&amp;#xA0;the
 greater of (i)&amp;#xA0;9.5% or (ii)&amp;#xA0;9.5%
 plus&lt;i&gt;&amp;#xA0;The Wall Street
 Journal&lt;/i&gt;&amp;#xA0;prime rate minus 5.25% or
 (B)&amp;#xA0;the greater of (i)&amp;#xA0;8.75% or (ii)&amp;#xA0;8.75%
 plus&lt;i&gt;&amp;#xA0;The Wall Street
 Journal&lt;/i&gt;&amp;#xA0;prime rate minus 5.25%, and the third
 tranche bearing interest at a variable rate equal to the greater of
 (i)&amp;#xA0;8.75% or (ii)&amp;#xA0;8.75% plus&lt;i&gt;&amp;#xA0;The
 Wall Street Journal&lt;/i&gt;&amp;#xA0;prime rate minus 5.25%.
 In an event of default, as defined, and until such event is no
 longer continuing, the interest rate applicable to borrowings under
 the Hercules Loan Agreement would be increased by 4.0%. As of
 March&amp;#xA0;31, 2019 and December&amp;#xA0;31, 2018, the interest rate
 applicable to borrowings under the Hercules Loan Agreement was
 9.80% and 9.75%.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Borrowings under the Hercules Loan Agreement are repayable in
 monthly interest-only payments through August 2019, or a later date
 upon achievement of specified conditions, and in equal monthly
 payments of principal and accrued interest from September 2019
 until the maturity date of the loan, which is November 2021. At the
 Company&amp;#x2019;s option, the Company may prepay all, but not less
 than all, of the outstanding borrowings, subject to a prepayment
 premium of up to 2.0% of the principal amount outstanding as of the
 date of repayment. The Hercules Loan Agreement also provides for a
 final payment, payable upon maturity or the repayment in full of
 all obligations under the agreement, of up to $953. An aggregate
 final payment of $794 payable in connection with the $8,000 term
 loan and the $2,000 term loan is being accreted to interest expense
 to increase the carrying value of the debt over the term of the
 loan using the effective interest method.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In addition, the Hercules Loan Agreement contains a redemption
 feature that, upon an event of default, provides Hercules the
 option to accelerate and demand repayment of the debt, including a
 prepayment premium. The Company concluded that the redemption
 feature meets the definition of a derivative instrument as the
 repayment of the debt contains a substantial premium, resulting in
 the redemption feature not being clearly and closely related to the
 host instrument. The Company recorded the issuance-date fair value
 of the derivative liability of $18 as a debt discount and as a
 derivative liability on its consolidated balance sheet.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Borrowings under the Hercules Loan Agreement are collateralized by
 substantially all of the Company&amp;#x2019;s personal property and
 other assets, including its intellectual property until a specified
 financing condition is met. Under the Hercules Loan Agreement, the
 Company has agreed to affirmative and negative covenants to which
 the Company will remain subject until maturity or repayment in
 full. The covenants include maintaining a minimum liquidity amount
 of the lesser of (i)&amp;#xA0;125% of outstanding borrowings under the
 Hercules Loan Agreement and (ii)&amp;#xA0;100% of the Company&amp;#x2019;s
 cash and cash equivalents in an account in which Hercules has a
 first priority security interest as well as restrictions on the
 Company&amp;#x2019;s ability to incur additional indebtedness, pay
 dividends, encumber its intellectual property, or engage in certain
 fundamental business transactions, such as mergers or acquisitions
 of other businesses. Obligations under the Hercules Loan Agreement
 are subject to acceleration upon occurrence of specified events of
 default, including payment default, insolvency and a material
 adverse change in the Company&amp;#x2019;s business, operations or
 financial or other condition.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In connection with entering into the Hercules Loan Agreement in
 October 2018, the Company issued to Hercules warrants for the
 purchase of 210,638&amp;#xA0;shares of Series&amp;#xA0;B convertible
 preferred stock at an exercise price of $1.88 per share. These
 warrants were immediately exercisable and expire in October
 2028.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In connection with entering into the First Amendment in December
 2018, the Company agreed to issue to Hercules warrants for the
 purchase of a specified number of shares of convertible preferred
 stock or, if issued following the Merger with Arsanis, a specified
 number of shares of common stock of the combined organization, at
 an aggregate exercise price of $99. The warrants were to be issued
 at the earliest of (i)&amp;#xA0;June&amp;#xA0;30, 2019, (ii)&amp;#xA0;the
 earlier to occur of (a)&amp;#xA0;the date the Company prepays the
 outstanding borrowings or (b)&amp;#xA0;the date the outstanding
 borrowings become due and payable, or (iii)&amp;#xA0;on or before the
 fifth business day following the closing of or the announcement of
 the termination of the Company&amp;#x2019;s Merger with Arsanis. The
 number of shares of convertible preferred stock issuable upon
 exercise of these warrants was determined to be 52,659 shares,
 calculated by dividing $99 by the $1.88 price per share paid by
 investors that purchased shares of Series&amp;#xA0;B convertible
 preferred stock in September 2018 (see Note&amp;#xA0;11). On
 March&amp;#xA0;18, 2019, as a result of the closing of the Merger with
 Arsanis on March&amp;#xA0;13, 2019, the Company issued to Hercules
 warrants for the purchase of 5,000 shares of common stock of the
 combined organization at an exercise price of $19.80 per share,
 each of which reflected the share Exchange Ratio
 of&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;1-for-0.5702&lt;/font&gt;&lt;/font&gt;&amp;#xA0;applied
 in the Merger as well as the Reverse Stock Split effected by the
 combined organization on March&amp;#xA0;13, 2019.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 On October&amp;#xA0;19, 2018 and December&amp;#xA0;11, 2018, the dates the
 Company entered into the Hercules Loan Agreement and the First
 Amendment, respectively, the Company recorded the aggregate initial
 fair value of the warrants of $132 as a preferred stock warrant
 liability, with a corresponding amount recorded as a debt discount
 on the Company&amp;#x2019;s consolidated balance sheet. As of
 March&amp;#xA0;13, 2019 and December&amp;#xA0;31, 2018, the fair value of
 the warrants was $326 and $282, respectively. Upon the closing of
 the Merger, the warrants were converted to warrants for common
 stock and are no longer adjusted to fair value.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In connection with entering into the Hercules Loan Agreement and
 the First Amendment, the Company also paid Hercules $92 of upfront
 fees, including facility, due diligence and legal fees associated
 with entering into the agreement, which were also recorded as a
 debt discount. The debt discount is reflected as a reduction of the
 carrying value of long-term debt on the Company&amp;#x2019;s
 consolidated balance sheet and is being amortized to interest
 expense over the term of the loan using the effective interest
 method.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The Company recognized aggregate interest expense under the
 Hercules Loan Agreement of $357 and $0 during three months ended
 March&amp;#xA0;31, 2019 and 2018, respectively, which
 included&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-cash&lt;/font&gt;&amp;#xA0;interest
 expense of $113 related to the accretion of the debt discount and
 the final payment. As of March&amp;#xA0;31, 2019 and December&amp;#xA0;31,
 2018, the unamortized debt discount was $182 and $226,
 respectively. The Company&amp;#x2019;s annual effective interest rate of
 the Hercules Loan Agreement as of March&amp;#xA0;31, 2019 and
 December&amp;#xA0;31, 2018 was approximately 14.2%, respectively.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 There were no principal payments due or paid under the Hercules
 Loan Agreement during the three months ended March&amp;#xA0;31, 2019.
 Principal payments begin in September 2019.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;FFG Loan Agreement&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Between September 2011 and March 2017, Arsanis GmbH, a subsidiary
 of Arsanis, entered into a series of funding agreements with
 &amp;#xD6;sterreichische Forschungsf&amp;#xF6;rderungsgesellschaft mbH
 (&amp;#x201C;FFG&amp;#x201D;) that provided for loans and grants to fund
 qualifying research and development expenditures of Arsanis GmbH on
 a&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;project-by-project&lt;/font&gt;&lt;/font&gt;&amp;#xA0;basis,
 as approved by FFG. Amounts due under the FFG loans bear interest
 at rates ranging from 0.75% to 2.0%&amp;#xA0;per annum. As of
 March&amp;#xA0;31, 2019, giving effect to the Settlement Agreement (as
 defined below), the loans matured at various dates between
 March&amp;#xA0;31, 2019 and March 2021. Interest on amounts due under
 the loans is payable semi-annually in arrears, with all principal
 and remaining accrued interest due upon maturity.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 As of March&amp;#xA0;31, 2019, the outstanding principal amount under
 loans from FFG was $9,546, including $2,914 of current portion.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 On March&amp;#xA0;8, 2019, Arsanis, Merger Sub, X4 and Arsanis GmbH, a
 wholly owned subsidiary of Arsanis, entered into the Settlement
 Agreement with FFG (the &amp;#x201C;Settlement Agreement&amp;#x201D;) in
 respect to allegations by FFG in February 2019 that Arsanis and
 Arsanis GmbH breached certain reporting, performance and other
 obligations in connection with grants and loans made by FFG to
 Arsanis GmbH between September 2011 and March 2017 to fund
 qualifying research and development expenditures. Pursuant to the
 terms of the Settlement Agreement, in exchange for FFG&amp;#x2019;s
 waiver of all claims against Arsanis and Arsanis GmbH (except for
 its claims for repayment of the loans and regular interest but
 including its waiver of claims for repayment of grants and interest
 exceeding regular interest), subject to compliance by Arsanis and
 Arsanis GmbH with the terms of the Settlement Agreement, Arsanis
 GmbH agreed to repay the outstanding loan principal (plus regular
 interest accrued thereon) on an accelerated payment schedule of
 three years instead of five years, with the final accelerated
 installment due and payable on June&amp;#xA0;30, 2021. The parties also
 agreed, among other things, that (i)&amp;#xA0;the portion of such loans
 to be repaid in 2019 is $2,914&amp;#xA0;on the first
 business day following&amp;#xA0;March&amp;#xA0;31, 2019 and
 (ii)&amp;#xA0;until all of the loans have been repaid and subject to
 other terms specified in the Settlement Agreement, commencing
 April&amp;#xA0;30, 2019, a minimum cash balance equal to 70% of the
 then-outstanding principal amount of the loans will be maintained
 at Arsanis GmbH in an account held with an Austrian bank.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 As of March&amp;#xA0;31, 2019, future principal payments and the final
 payment due under the Company&amp;#x2019;s loan agreements were as
 follows:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="61%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="5%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="5%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="5%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;Year Ending December&amp;#xA0;31,&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Hercules&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;FFG&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Total&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2019&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,345&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2,914&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,259&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2020&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,305&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,462&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,767&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2021&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,350&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2,170&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;6,520&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Long-term debt&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;
 &amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;10,000&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;
 &amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;9,546&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19,546&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
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 &lt;tr style="FONT-SIZE: 1px"&gt;
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 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
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 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
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 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
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 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
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  <us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_29777C2D-E0DB-433D-BA39-674C4E97CEBC_1_13" unitRef="iso4217_USD">-11465000</us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic>
  <us-gaap:NewAccountingPronouncementsPolicyPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_319E7FB9-A2DC-4860-9B63-F78FD85DC841_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Recently Adopted Accounting Pronouncements&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In February 2016, the FASB issued
 ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;No.&amp;#xA0;2016-02&lt;/font&gt;&lt;i&gt;,
 Leases
 (Topic&lt;/i&gt;&lt;i&gt;&amp;#xA0;842)&lt;/i&gt;&amp;#xA0;(&amp;#x201C;ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2016-02&amp;#x201D;&lt;/font&gt;&amp;#xA0;or
 &amp;#x201C;ASC 842&amp;#x201D;)), which sets out the principles for the
 recognition, measurement, presentation and disclosure of leases for
 both parties to a contract (i.e., lessees and lessors). The new
 standard requires lessees to apply a dual approach, classifying
 leases as either finance or operating leases based on the principle
 of whether or not the lease is effectively a financed purchase by
 the lessee. This classification will determine whether lease
 expense is recognized based on an effective interest method or on a
 straight-line basis over the term of the lease. A lessee is also
 required to record a&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt;&amp;#xA0;asset
 and a lease liability for all leases with a term of greater than
 12&amp;#xA0;months regardless of their classification. Leases with a
 term of 12 months or less may be accounted for similar to prior
 guidance for operating leases. The Company adopted the new leasing
 standard as of the required effective date of January&amp;#xA0;1, 2019
 using a modified retrospective transition approach to be applied to
 leases existing as of, or entered into after, January&amp;#xA0;1, 2019.
 The adoption had no impact on accumulated deficit. The new lease
 standard provides a number of optional practical expedients in
 transition. The Company applied the package of practical expedients
 to leases that commenced prior to the effective date, whereby it
 will elect to not reassess the following: (i)&amp;#xA0;whether any
 expired or existing contracts contain leases; (ii)&amp;#xA0;the lease
 classification for any expired or existing leases; and
 (iii)&amp;#xA0;initial direct costs for any existing leases. The
 Company also elected the short-term lease recognition exemption for
 all leases that qualify, where a&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt;&amp;#xA0;asset
 or lease liability will not be recognized for short-term leases.
 Upon the adoption of ASC 842, the Company recorded
 $2.5&amp;#xA0;million of operating lease liabilities and
 $2.0&amp;#xA0;million of&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&amp;#xA0;assets&lt;/font&gt;&lt;/font&gt;&amp;#xA0;on
 its consolidated balance. The adoption did not have a material
 impact on the Company&amp;#x2019;s statement of operations, statement of
 comprehensive loss or statement of cash flows.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In January 2017, the FASB issued ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;No.&amp;#xA0;2017-04,&lt;/font&gt;&lt;i&gt;&amp;#xA0;Intangibles-Goodwill
 and Other (Topic 350): Simplifying the Test for Goodwill
 Impairment.&lt;/i&gt;&amp;#xA0;The new standard simplifies the subsequent
 measurement of goodwill by eliminating the second step of the
 goodwill impairment test. This ASU will be applied prospectively
 and is effective for annual or interim goodwill impairment tests in
 fiscal years beginning after December&amp;#xA0;15, 2019 with early
 adoption permitted. The Company has adopted this guidance on
 January&amp;#xA0;1, 2019 and will apply it to its annual impairment
 test, and any interim impairment tests during the year ending
 December&amp;#xA0;31, 2019.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In April 2017, the FASB issued ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2017-08,&lt;/font&gt;&lt;i&gt;&amp;#xA0;Receivables &amp;#x2013;
 Nonrefundable Fees and Other
 Costs&lt;/i&gt;&amp;#xA0;(&amp;#x201C;Subtopic&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;310-20&amp;#x201D;).&lt;/font&gt;&amp;#xA0;The
 new standard amends the amortization period for certain purchased
 callable debt securities held at a premium by shortening the
 amortization period for the premium to the earliest call
 date.&amp;#xA0;Subtopic&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;310-20&lt;/font&gt;&amp;#xA0;calls for a
 modified retrospective application under which&amp;#xA0;a
 cumulative-effect adjustment will be made to retained earnings as
 of the beginning of the first reporting period in which the
 guidance is adopted.&amp;#xA0;The new standard will be effective
 beginning January&amp;#xA0;1, 2019 and early adoption is permitted for
 public entities.&amp;#xA0;The Company adopted this guidance, effective
 January&amp;#xA0;1, 2019, and its adoption had no impact on the
 Company&amp;#x2019;s financial position, results of operations or cash
 flows.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In July 2017, the FASB issued ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;No.&amp;#xA0;2017-11,&lt;/font&gt;&amp;#xA0;&lt;i&gt;Earnings
 Per Share (Topic&lt;/i&gt;&lt;i&gt;&amp;#xA0;260), Distinguishing Liabilities from
 Equity (Topic&lt;/i&gt;&lt;i&gt;&amp;#xA0;480), Derivatives and Hedging
 (Topic&lt;/i&gt;&lt;i&gt;&amp;#xA0;815) (Part&lt;/i&gt;&lt;i&gt;&amp;#xA0;I) Accounting for Certain
 Financial Instruments with Down Round Features
 (Part&lt;/i&gt;&lt;i&gt;&amp;#xA0;II) Replacement of the Indefinite Deferral for
 Mandatorily Redeemable Financial Instruments of Certain Nonpublic
 Entities and Certain Mandatorily Redeemable Noncontrolling
 Interests with a Scope
 Exception&lt;/i&gt;&amp;#xA0;(&amp;#x201C;ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2017-11&amp;#x201D;).&lt;/font&gt;&amp;#xA0;Part&amp;#xA0;I
 applies to entities that issue financial instruments such as
 warrants, convertible debt or convertible preferred stock that
 contain down-round features. Part&amp;#xA0;II replaces the indefinite
 deferral for certain mandatorily redeemable noncontrolling
 interests and mandatorily redeemable financial instruments of
 nonpublic entities contained within ASC Topic&amp;#xA0;480 with a scope
 exception and does not impact the accounting for these mandatorily
 redeemable instruments. For public entities,
 ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2017-11&lt;/font&gt;&amp;#xA0;is effective
 for annual reporting periods beginning after December&amp;#xA0;15,
 2018, including interim periods within those fiscal years. The
 Company adopted ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2017-11&lt;/font&gt;&amp;#xA0;as of the
 required effective date of January&amp;#xA0;1, 2019. The adoption of
 ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2017-11&lt;/font&gt;&amp;#xA0;had no
 impact on the Company&amp;#x2019;s financial position, results of
 operations or cash flows.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In June 2018, the FASB issued ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;No.&amp;#xA0;2018-07,&lt;/font&gt;&amp;#xA0;&lt;i&gt;Compensation&amp;#x2014;Stock
 Compensation (Topic&lt;/i&gt;&lt;i&gt;&amp;#xA0;718): Improvements to Nonemployee
 Share-Based Payment
 Accounting&amp;#xA0;&lt;/i&gt;(&amp;#x201C;ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2018-07&amp;#x201D;).&lt;/font&gt;&amp;#xA0;These
 amendments expand the scope of Topic&amp;#xA0;718,
 Compensation&amp;#x2014;Stock Compensation (which previously only
 included share-based payments to employees) to include share-based
 payments issued to&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-employees&lt;/font&gt;&amp;#xA0;for
 goods or services. Consequently, the accounting for share-based
 payments to&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-employees&lt;/font&gt;&amp;#xA0;and
 employees will be substantially aligned. The ASU
 supersedes&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;Subtopic&amp;#xA0;505-50,&lt;/font&gt;&amp;#xA0;Equity&amp;#x2014;&lt;i&gt;Equity-Based
 Payments to&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;Non-Employees&lt;/font&gt;&lt;/i&gt;. The Company adopted
 ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2018-07&lt;/font&gt;&amp;#xA0;on
 January&amp;#xA0;1, 2019. The adoption of this standard had no impact
 on the Company&amp;#x2019;s financial statements.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Recently Issued Accounting Pronouncements&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In August 2018, the FASB issued ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;No.&amp;#xA0;2018-13,&lt;/font&gt;&lt;i&gt;&amp;#xA0;Fair
 Value Measurement (Topic 820): Disclosure Framework&amp;#x2014;Changes
 to the Disclosure Requirements for Fair Value
 Measurement&lt;/i&gt;&amp;#xA0;(&amp;#x201C;ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2018-13&amp;#x201D;),&lt;/font&gt;&amp;#xA0;which&amp;#xA0;removes,
 adds and modifies certain disclosure requirements for fair value
 measurements in Topic 820. The Company will no longer be required
 to disclose the amount of and reasons for transfers between
 Level&amp;#xA0;1 and Level&amp;#xA0;2 of the fair value hierarchy as well
 as the valuation processes of Level&amp;#xA0;3 fair value measurements.
 However, the Company will be required to additionally disclose the
 changes in unrealized gains and losses included in other
 comprehensive income for recurring Level&amp;#xA0;3 fair value
 measurements and the range and weighted average of assumptions used
 to develop significant unobservable inputs for Level&amp;#xA0;3 fair
 value measurements. ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2018-13&lt;/font&gt;&amp;#xA0;is effective
 for fiscal years, and interim periods within those fiscal years,
 beginning after December&amp;#xA0;15, 2019. The amendments relating to
 additional disclosure requirements will be applied prospectively
 for only the most recent interim or annual period presented in the
 initial year of adoption. All other amendments will be applied
 retrospectively to all periods presented upon their effective date.
 The Company is currently evaluating the impact that the adoption of
 ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2018-13&lt;/font&gt;&amp;#xA0;will have on
 its consolidated financial statements.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In August 2018, the FASB issued ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2018-15,&lt;/font&gt;&lt;i&gt;&amp;#xA0;Intangibles-Goodwill
 and&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;Other-Internal-Use&lt;/font&gt;&amp;#xA0;Software
 (Subtopic&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;350-40):&lt;/font&gt;&amp;#xA0;Customer&amp;#x2019;s
 Accounting for Implementation Costs Incurred in a Cloud Computing
 Arrangement That Is a Service Contract,
 (&amp;#x201C;ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2018-15&amp;#x201D;)&lt;/font&gt;&lt;/i&gt;. The amendments in
 this update align the requirements for capitalizing implementation
 costs incurred in a hosting arrangement that is a service contract
 with the requirements for capitalizing implementation costs
 incurred to develop or obtain&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;internal-use&lt;/font&gt;&amp;#xA0;software
 (and hosting arrangements that include
 an&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;internal-use&lt;/font&gt;&amp;#xA0;software
 license). The accounting for the service element of a hosting
 arrangement that is a service contract is not affected by the
 amendments in this update. The new standard will be effective
 beginning January&amp;#xA0;1, 2020 and early adoption is permitted. The
 amendments in this update should be applied either retrospectively
 or prospectively to all implementation costs incurred after the
 date of adoption.&amp;#xA0;The Company is currently evaluating the
 impact that the adoption of ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2018-15&lt;/font&gt;&amp;#xA0;will have on
 its consolidated financial statements.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:NewAccountingPronouncementsPolicyPolicyTextBlock>
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  <us-gaap:OperatingLeaseCost contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_B25143D0-B17D-4DC9-8A68-2788822ABB32_1_0" unitRef="iso4217_USD">187000</us-gaap:OperatingLeaseCost>
  <us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_8A248B6F-7262-4CE5-99F7-44660F4FD70C_1_0" unitRef="iso4217_USD">23000</us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax>
  <us-gaap:OperatingIncomeLoss contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_29777C2D-E0DB-433D-BA39-674C4E97CEBC_1_4" unitRef="iso4217_USD">-10438000</us-gaap:OperatingIncomeLoss>
  <us-gaap:OperatingLeasePayments contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_B25143D0-B17D-4DC9-8A68-2788822ABB32_1_3" unitRef="iso4217_USD">201000</us-gaap:OperatingLeasePayments>
  <us-gaap:PaymentsToAcquireBusinessesNetOfCashAcquired contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_16" unitRef="iso4217_USD">-26406000</us-gaap:PaymentsToAcquireBusinessesNetOfCashAcquired>
  <us-gaap:ProceedsFromStockOptionsExercised contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_19" unitRef="iso4217_USD">113000</us-gaap:ProceedsFromStockOptionsExercised>
  <us-gaap:PropertyPlantAndEquipmentDisclosureTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_524AE12A-400D-4863-8EEF-2764072DF894_1_0">&lt;div&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;&lt;b&gt;5.&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;&lt;b&gt;Property and Equipment, Net&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Property and equipment, net consisted of the following:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="76%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="7%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="7%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;March&amp;#xA0;31,&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;2019&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;December&amp;#xA0;31,&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;2018&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Leasehold improvements&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;299&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;299&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Furniture and fixtures&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;53&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;53&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Computer equipment&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;56&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Software&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;9&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;9&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Lab equipment&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;67&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;448&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;417&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Less: Accumulated depreciation and amortization&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(177&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(176&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;271&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;241&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Depreciation and amortization expense related to property and
 equipment was $20 and $26 for the three months ended March&amp;#xA0;31,
 2019 and 2018, respectively.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:PropertyPlantAndEquipmentDisclosureTextBlock>
  <us-gaap:ProfitLoss contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_1" unitRef="iso4217_USD">10873000</us-gaap:ProfitLoss>
  <us-gaap:PropertyPlantAndEquipmentTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_E56BC26C-E1A0-4A26-9548-7AEF873E455D_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Property and equipment, net consisted of the following:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="76%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="7%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="7%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;March&amp;#xA0;31,&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;2019&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;December&amp;#xA0;31,&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;2018&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Leasehold improvements&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;299&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;299&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Furniture and fixtures&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;53&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;53&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Computer equipment&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;56&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Software&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;9&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;9&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Lab equipment&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;67&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;448&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;417&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Less: Accumulated depreciation and amortization&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(177&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(176&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;271&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;241&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;/div&gt;</us-gaap:PropertyPlantAndEquipmentTextBlock>
  <us-gaap:PropertyPlantAndEquipmentPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_A20B22FD-1E0D-4FFC-9748-B12CC76597BD_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Property and Equipment&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Property and equipment are stated at cost less accumulated
 depreciation and amortization. Depreciation and amortization
 expense is recognized using the straight-line method over the
 estimated useful life of each asset, as follows:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="68%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="62%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="4%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" align="center"&gt;&lt;b&gt;Estimated&amp;#xA0;Useful&amp;#xA0;Life&lt;/b&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Office furniture&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;3 years&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Computer equipment&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;3 years&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Software&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;3 years&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Laboratory equipment&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;3 to 10 years&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Leasehold improvements&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;
 Shorter&amp;#xA0;of&amp;#xA0;lease&amp;#xA0;term&amp;#xA0;or&amp;#xA0;10&amp;#xA0;years&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Estimated useful lives are periodically assessed to determine if
 changes are appropriate. Maintenance and repairs are charged to
 expense as incurred. When assets are retired or otherwise disposed
 of, the cost of these assets and related accumulated depreciation
 or amortization are eliminated from the consolidated balance sheet
 and any resulting gains or losses are included in the consolidated
 statements of operations and comprehensive loss in the period of
 disposal. Costs for capital assets not yet placed into service are
 capitalized as &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;construction-in-progress&lt;/font&gt;&lt;/font&gt; and
 depreciated once placed into service.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:PropertyPlantAndEquipmentPolicyTextBlock>
  <us-gaap:ResearchAndDevelopmentExpense contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_29777C2D-E0DB-433D-BA39-674C4E97CEBC_1_1" unitRef="iso4217_USD">5655000</us-gaap:ResearchAndDevelopmentExpense>
  <us-gaap:ResearchAndDevelopmentExpensePolicy contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_56F4C4EE-CF61-4BEA-886F-121E0C057A23_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Research and Development Costs&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Costs associated with internal research and development and
 external research and development services, including drug
 development and preclinical studies, are expensed as incurred.
 Research and development expenses include costs for salaries,
 employee benefits, subcontractors, facility-related expenses,
 depreciation and amortization, stock-based compensation,
 third-party license fees, laboratory supplies, and external costs
 of outside vendors engaged to conduct discovery, preclinical and
 clinical development activities and clinical trials as well as to
 manufacture clinical trial materials, and other costs. The Company
 recognizes external research and development costs based on an
 evaluation of the progress to completion of specific tasks using
 information provided to the Company by its service providers.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Nonrefundable advance payments for goods or services to be received
 in the future for use in research and development activities are
 recorded as prepaid expenses. Such prepaid expenses are recognized
 as an expense when the goods have been delivered or the related
 services have been performed, or when it is no longer expected that
 the goods will be delivered or the services rendered.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Upfront payments, milestone payments and annual maintenance fees
 under license agreements are expensed in the period in which they
 are incurred.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:ResearchAndDevelopmentExpensePolicy>
  <us-gaap:RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="0" id="id_13073811_B25143D0-B17D-4DC9-8A68-2788822ABB32_1_4" unitRef="iso4217_USD">781</us-gaap:RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability>
  <us-gaap:ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_EAD28E9A-CDD0-48CC-A972-CB62FA4A92C6_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company excluded the following potential common shares,
 presented based on amounts outstanding at each period end and
 adjusted for the Exchange Ratio and Reverse Stock Split, from the
 computation of diluted net loss per share attributable to common
 stockholders for the periods indicated because including them would
 have had an anti-dilutive effect:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 12px"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="76%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="3%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="3%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="6" align="center"&gt;&lt;b&gt;Three Months Ended&lt;br /&gt;
 March&amp;#xA0;31,&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2019&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2018&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Options to purchase common stock&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,037,089&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;538,429&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Convertible preferred stock (as converted to common stock)&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;3,556,147&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Warrants to purchase common stock (presented on an &lt;font style="WHITE-SPACE: nowrap"&gt;as-converted,&lt;/font&gt; as exchanged,
 split-adjusted basis.&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;493,927&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;423,416&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,531,016&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,517,992&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;/div&gt;</us-gaap:ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock>
  <us-gaap:ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_118DCDFA-CDE7-4065-89F8-1613BE3496D0_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company adopted ASU &lt;font style="WHITE-SPACE: nowrap"&gt;2016-02&lt;/font&gt; on January&amp;#xA0;1, 2019 as
 noted above, and as required, the following disclosure is provided
 for periods prior to adoption. Future annual minimum lease payments
 due under the Company&amp;#x2019;s operating leases as of
 December&amp;#xA0;31, 2018 were as follows:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="68%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="81%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="14%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; BORDER-BOTTOM: #000000 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell"&gt;
 &lt;b&gt;Year Ending December&amp;#xA0;31,&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Operating&amp;#xA0;Leases&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2019&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;810&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2020&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;823&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2021&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;835&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2022&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;492&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Total&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2,960&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;/div&gt;</us-gaap:ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock>
  <us-gaap:RevenueFromContractWithCustomerPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_E1F49BB2-55F2-4D1B-8018-F38872D8C471_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Revenue Recognition&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Effective January&amp;#xA0;1, 2018, the Company adopted ASC Topic 606,
 Revenue from Contracts with Customers (&amp;#x201C;ASC 606&amp;#x201D;),
 using the modified retrospective transition method. The modified
 retrospective method requires that the cumulative effect of
 initially applying ASC 606 be recognized as an adjustment to the
 opening balance of retained earnings or accumulated deficit of the
 annual period that includes the date of initial application. The
 Company did not have any arrangements that were in the scope of ASC
 606 on January&amp;#xA0;1, 2018 and thus there was no impact to the
 condensed consolidated financial statements as a result of the
 adoption. This standard applies to all contracts with customers,
 except for contracts that are within the scope of other standards,
 such as collaboration arrangements and leases. Prior to completion
 of the Merger, Arsanis entered into a
 single&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;out-licensing&lt;/font&gt;&amp;#xA0;agreement
 with Janssen Pharmaceuticals, Inc. (see Note 13) that was within
 the scope of ASC 606.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:RevenueFromContractWithCustomerPolicyTextBlock>
  <us-gaap:ScheduleOfAccruedLiabilitiesTableTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_1F7D00C9-59C2-41C9-B4D2-7991D23A7DAF_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Accrued expenses consisted of the following:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="72%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="8%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="8%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;March&amp;#xA0;31,&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;2019&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;December&amp;#xA0;31,&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;2018&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Accrued employee compensation and benefits&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;
 &amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;1,239&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;924&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Accrued external research and development expenses&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;819&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;754&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Accrued professional fees&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,850&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,324&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Deferred rent, current portion&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;93&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Other&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;271&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;156&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,179&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;3,251&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;br class="Apple-interchange-newline" /&gt;

 &lt;/div&gt;</us-gaap:ScheduleOfAccruedLiabilitiesTableTextBlock>
  <us-gaap:ScheduleOfCompensationCostForShareBasedPaymentArrangementsAllocationOfShareBasedCompensationCostsByPlanTableTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_60EDC73C-6600-49ED-8B01-33EB96EC79B5_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Stock-based compensation expense was classified in the consolidated
 statements of operations and comprehensive loss as follows:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="80%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="8%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="8%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="6" align="center"&gt;&lt;b&gt;Three Months Ended&lt;br /&gt;
 March&amp;#xA0;31,&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2019&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2018&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Research and development expense&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;84&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;38&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 General and administrative expense&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;178&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;90&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Total stock-based compensation&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;262&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;128&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;/div&gt;</us-gaap:ScheduleOfCompensationCostForShareBasedPaymentArrangementsAllocationOfShareBasedCompensationCostsByPlanTableTextBlock>
  <us-gaap:ShareBasedCompensation contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_3" unitRef="iso4217_USD">262000</us-gaap:ShareBasedCompensation>
  <us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_017F787D-60B9-463C-95F5-35D9FA332CDB_1_1">Incentive  stock options granted to employees and restricted stock awards granted to  employees, officers, members of the board of directors, advisors, and  consultants of the Company typically vest over four years. Non-statutory options  granted to employees, officers, members of the board of directors, advisors, and  consultants of the Company typically vest over three or four years.</us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights>
  <us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1 contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_8F24BC0F-1335-4625-993E-6C8BB0CDE523_1_1">P5Y10M24D</us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1>
  <us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2 contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_E1C4989F-8666-4E6A-A026-FD37F32988CC_3001_2">P7Y7M24D</us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2>
  <us-gaap:ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="2" id="id_13073811_E685F46A-0EFF-4A61-907A-DD6330BCD82D_5001_4" unitRef="iso4217_USD_per_shares">6.85</us-gaap:ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice>
  <us-gaap:SignificantAccountingPoliciesTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_0E777C3F-6167-4A35-A105-E53977D23736_1_0">&lt;div&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;&lt;b&gt;2.&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;&lt;b&gt;Summary of Significant Accounting Policies&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 &lt;b&gt;&lt;i&gt;Unaudited Interim Financial Statements&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The condensed balance sheet at December&amp;#xA0;31, 2018 was derived
 from audited financial statements but does not include all
 disclosures required by GAAP. The accompanying condensed
 consolidated financial statements are unaudited. The accompanying
 unaudited interim consolidated financial statements have been
 prepared by the Company pursuant to the rules and regulations of
 the Securities and Exchange Commission (the &amp;#x201C;SEC&amp;#x201D;) for
 interim financial statements. Accordingly, certain information and
 footnote disclosures normally included in financial statements
 prepared in accordance with GAAP have been condensed or omitted
 pursuant to such rules and regulations. However, the Company
 believes that the disclosures are adequate to make the information
 presented not misleading. These unaudited condensed financial
 statements should be read in conjunction with the
 Company&amp;#x2019;s&amp;#xA0;audited financial statements and the notes
 thereto for the year ended December&amp;#xA0;31, 2018. In the opinion
 of management, all adjustments, consisting only of normal recurring
 adjustments as necessary, for the fair statement of the
 Company&amp;#x2019;s condensed financial position, condensed results of
 its operations and cash flows have been made. The results of
 operations for the three months ended March&amp;#xA0;31, 2019 are not
 necessarily indicative of the results of operations that may be
 expected for the year ending December&amp;#xA0;31, 2019.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Use of Estimates&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The preparation of the Company&amp;#x2019;s condensed consolidated
 financial statements in conformity with GAAP requires management to
 make estimates and assumptions that affect the reported amounts of
 assets and liabilities, the disclosure of contingent assets and
 liabilities at the date of the consolidated financial statements,
 and the reported amounts of expenses during the reporting period.
 Significant estimates and assumptions reflected in these
 consolidated financial statements include, but are not limited to,
 the accrual of research and development expenses, the valuation of
 intangible assets acquired in business combinations, the valuations
 of common stock prior to the Merger, the valuation of stock
 options, preferred stock warrants (and the resulting preferred
 stock warrant liability), derivative instruments (and the resulting
 derivative liability), and the preferred stock repurchase
 liability, and valuation of lease liabilities. The Company bases
 its estimates on historical experience, known trends and other
 market-specific or other relevant factors that it believes to be
 reasonable under the circumstances. On an ongoing basis, management
 evaluates its estimates when there are changes in circumstances,
 facts and experience. Changes in estimates are recorded in the
 period in which they become known. Actual results could differ from
 those estimates.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Principles of Consolidation&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The condensed consolidated financial statements include the
 accounts of the Company and its wholly owned subsidiaries,
 including Arsanis Biosciences GmbH, which is incorporated in
 Vienna, Austria (&amp;#x201C;Arsanis GmbH&amp;#x201D;), and X4 Therapeutics,
 Inc. All significant intercompany accounts and transactions have
 been eliminated.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Foreign Currency and Currency Translation&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Management has determined that the functional currency for the
 Company&amp;#x2019;s wholly owned foreign subsidiary, Arsanis
 Biosciences GmbH, is the Euro. Management&amp;#x2019;s assessment
 considered the currency environment in which the entity operates,
 including inflows of cash from research and development incentive
 programs and outflows of cash for operating expenditure.
 Accordingly, the assets and liabilities of Arsanis Biosciences GmbH
 are translated from the Euro into United States dollars at the
 exchange rate in effect on the balance sheet date and income and
 expenses are translated at the average exchange rate in effect
 during the period. Unrealized translation gains and losses are
 recorded as a cumulative translation adjustment, which is included
 in the consolidated balance sheet as a component of accumulated
 other comprehensive income (loss). Adjustments that arise from
 exchange rate changes on transactions denominated in a currency
 other than the Euro are included in other income (expense), net in
 the consolidated statements of operations as incurred.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Concentrations of Credit Risk and Significant
 Suppliers&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Financial instruments that potentially subject the Company to
 concentrations of credit risk consist principally of cash and cash
 equivalents and research and development incentive receivables. The
 Company generally maintains cash balances in various operating
 accounts at financial institutions that management believes to be
 of high credit quality, in amounts that may exceed federally
 insured limits. The Company has not experienced any losses related
 to its cash and cash equivalents.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company is dependent on third-party manufacturers to supply
 products for research and development activities in its programs.
 The Company relies and expects to continue to rely on a small
 number of manufacturers to supply it with its requirements for the
 active pharmaceutical ingredients and formulated drugs related to
 these programs. These programs could be adversely affected by a
 significant interruption in these manufacturing services or in the
 supply of active pharmaceutical ingredients and formulated
 drugs.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Cash and Cash Equivalents&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company considers all highly liquid investments with maturities
 of three months or less at the date of purchase to be cash
 equivalents. Cash equivalents consisted of money market funds as of
 March&amp;#xA0;31, 2019 and December&amp;#xA0;31, 2018.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Restricted Cash&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 In connection with the Company&amp;#x2019;s lease agreement entered into
 January 2017 for its facility in Cambridge, Massachusetts, the
 Company maintains a letter of credit of $264 for the benefit of the
 landlord. As of March&amp;#xA0;31, 2019 and December&amp;#xA0;31, 2018, the
 underlying cash balance securing this letter of credit was
 classified as restricted cash &lt;font style="WHITE-SPACE: nowrap"&gt;(non-current)&lt;/font&gt; on its condensed
 consolidated balance sheets.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company also maintains letters of credit for the benefit of the
 landlords in connection with the Company&amp;#x2019;s office,
 laboratory, parking and storage space leases in Waltham, MA and
 Vienna, Austria and another letter of credit in connection with
 Company&amp;#x2019;s corporate credit cards. As of March&amp;#xA0;31, 2019,
 long term restricted cash consisted of letters of credit related to
 the Company&amp;#x2019;s leases of office, laboratory, parking and
 storage space lease in Vienna, Austria, of $283 and leased office
 space acquired from Arsanis located in Waltham, MA, which expires
 on December&amp;#xA0;31, 2023, of approximately $250.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 As of March&amp;#xA0;31, 2019, the Company was also required to
 maintain a separate cash balance of $150 to collateralize corporate
 credit cards with a bank, which was classified as restricted cash
 &lt;font style="WHITE-SPACE: nowrap"&gt;(non-current)&lt;/font&gt; on its
 consolidated balance sheets.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Property and Equipment&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Property and equipment are stated at cost less accumulated
 depreciation and amortization. Depreciation and amortization
 expense is recognized using the straight-line method over the
 estimated useful life of each asset, as follows:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="68%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="62%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="4%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" align="center"&gt;&lt;b&gt;Estimated&amp;#xA0;Useful&amp;#xA0;Life&lt;/b&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Office furniture&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;3 years&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Computer equipment&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;3 years&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Software&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;3 years&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Laboratory equipment&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;3 to 10 years&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Leasehold improvements&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;
 Shorter&amp;#xA0;of&amp;#xA0;lease&amp;#xA0;term&amp;#xA0;or&amp;#xA0;10&amp;#xA0;years&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Estimated useful lives are periodically assessed to determine if
 changes are appropriate. Maintenance and repairs are charged to
 expense as incurred. When assets are retired or otherwise disposed
 of, the cost of these assets and related accumulated depreciation
 or amortization are eliminated from the consolidated balance sheet
 and any resulting gains or losses are included in the consolidated
 statements of operations and comprehensive loss in the period of
 disposal. Costs for capital assets not yet placed into service are
 capitalized as &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;construction-in-progress&lt;/font&gt;&lt;/font&gt; and
 depreciated once placed into service.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 18px"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt"&gt;
 &lt;b&gt;&lt;i&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;Right-of-Use&lt;/font&gt;&lt;/font&gt; Assets and
 Leases&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Effective January&amp;#xA0;1, 2019, the Company adopted Accounting
 Standards Codification (&amp;#x201C;ASC&amp;#x201D;), Topic 842,
 &lt;i&gt;Leases&lt;/i&gt; (&amp;#x201C;ASC 842&amp;#x201D;), using the modified
 retrospective approach through a cumulative-effect adjustment and
 utilizing the effective date as its date of initial application,
 with prior periods unchanged and presented in accordance with the
 guidance in Topic 840, &lt;i&gt;Leases&lt;/i&gt; (&amp;#x201C;ASC 840&amp;#x201D;).&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 At the inception of an arrangement, the Company determines whether
 the arrangement is or contains a lease based on the unique facts
 and circumstances present. Leases with a &lt;font style="WHITE-SPACE: nowrap"&gt;non-cancellable&lt;/font&gt; term greater than one
 year are recognized on the balance sheet as &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt; assets, lease
 liabilities and long-term lease liabilities. The Company has
 elected not to recognize on the balance sheet leases with terms of
 one year or less. Options to renew a lease are not included in the
 Company&amp;#x2019;s initial lease term assessment unless there is
 reasonable certainty that the Company will renew.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Operating lease liabilities and their corresponding &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt; assets are
 recorded based on the present value of lease payments over the
 expected remaining lease term. However, certain adjustments to the
 &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt; operating asset
 may be required for items, such as incentives received. The
 interest rate implicit in lease contracts is typically not readily
 determinable. As a result, the Company utilizes its incremental
 borrowing rates, which are the rates it incurs to borrow on a
 collateralized basis over a similar term an amount equal to the
 lease payments in a similar economic environment.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 In accordance with the guidance in ASC 842, components of a lease
 are split into lease components and &lt;font style="WHITE-SPACE: nowrap"&gt;non-lease&lt;/font&gt; components. A policy
 election is available pursuant to which an entity may elect to not
 separate lease and &lt;font style="WHITE-SPACE: nowrap"&gt;non-lease&lt;/font&gt; components. Rather, each
 lease component and the related &lt;font style="WHITE-SPACE: nowrap"&gt;non-lease&lt;/font&gt; components would be
 accounted for together as a single component. For new and amended
 leases beginning in 2019 and after, the Company has elected to
 account for the lease and &lt;font style="WHITE-SPACE: nowrap"&gt;non-lease&lt;/font&gt; components as a combined
 lease component for its office and laboratory building leases.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Impairment of Long-Lived Assets&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Long-lived assets consist of property and equipment. Long-lived
 assets to be held and used are tested for recoverability whenever
 events or changes in business circumstances indicate that the
 carrying amount of the assets may not be fully recoverable. Factors
 that the Company considers in deciding when to perform an
 impairment review include significant underperformance of the
 business in relation to expectations, significant negative industry
 or economic trends and significant changes or planned changes in
 the use of the assets. If an impairment review is performed to
 evaluate a long-lived asset group for recoverability, the Company
 compares forecasts of undiscounted cash flows expected to result
 from the use and eventual disposition of the long-lived asset group
 to its carrying value. An impairment loss would be recognized in
 loss from operations when estimated undiscounted future cash flows
 expected to result from the use of an asset group are less than its
 carrying amount. The impairment loss would be based on the excess
 of the carrying value of the impaired asset group over its fair
 value. To date, the Company has not recorded any impairment losses
 on long-lived assets.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Goodwill&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Business combinations are accounted for under the acquisition
 method. The total purchase price of an acquisition is allocated to
 the underlying identifiable net assets, based on their respective
 estimated fair values as of the acquisition date. Determining the
 fair value of assets acquired and liabilities assumed requires
 management&amp;#x2019;s judgment and often involves the use of
 significant estimates and assumptions, including assumptions with
 respect to future cash inflows and outflows, probabilities of
 success, discount rates, and asset lives, among other items. Assets
 acquired and liabilities assumed are recorded at their estimated
 fair values. The excess of the purchase price over the estimated
 fair values of the net assets acquired is recorded as goodwill.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Goodwill is tested for impairment at the reporting unit level
 annually in the fourth quarter, or more frequently when events or
 changes in circumstances indicate that the asset might be impaired.
 Examples of such events or circumstances include, but are not
 limited to, a significant adverse change in legal or business
 climate, an adverse regulatory action or unanticipated competition.
 The Company has determined that it operates in a single operating
 segment and has a single reporting unit.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company assesses qualitative factors to determine whether the
 existence of events or circumstances would indicate that it is more
 likely than not that the fair value of the reporting unit was less
 than its carrying amount. If after assessing the totality of events
 or circumstances, the Company were to determine that it is more
 likely than not that the fair value of the reporting unit is less
 than its carrying amount, then the Company would perform a
 quantitative impairment test.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company compares the fair value of the reporting unit to its
 carrying value. If the fair value of the reporting unit exceeds the
 carrying value of the net assets, goodwill is not impaired, and no
 further testing is required. If the fair value of the reporting
 unit is less than the carrying value, the Company measures the
 amount of impairment loss, if any, as the excess of the carrying
 value over the fair value of the reporting unit. The Company has
 determined there were no indicators of goodwill impairment as of
 March&amp;#xA0;31, 2019.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 18px"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt"&gt;
 &lt;b&gt;&lt;i&gt;Intangible Assets&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company acquired certain &lt;font style="WHITE-SPACE: nowrap"&gt;in-process&lt;/font&gt; research and development
 assets (&amp;#x201C;IPR&amp;amp;D&amp;#x201D;), which are classified as
 indefinite-lived intangible assets. Acquired IPR&amp;amp;D represents
 the fair value assigned to research and development assets that the
 Company acquires and have not been completed at the acquisition
 date. The fair value of IPR&amp;amp;D acquired in a business
 combination is capitalized on the Company&amp;#x2019;s consolidated
 balance sheets at the acquisition-date fair value and is determined
 by estimating the costs to develop the technology into commercially
 viable products, estimating the resulting revenue from the
 projects, and discounting the projected net cash flows to present
 value. IPR&amp;amp;D is not amortized, but rather is reviewed for
 impairment on an annual basis or more frequently if indicators of
 impairment are present, until the project is completed or
 abandoned. If the Company determines that IPR&amp;amp;D becomes
 impaired or is abandoned, the carrying value is written down to its
 fair value with the related impairment charge recognized in the
 Company&amp;#x2019;s consolidated statement of operations in the period
 in which the impairment occurs. Upon successful completion of each
 project and launch of the product, the Company will make a separate
 determination of the estimated useful life of the IPR&amp;amp;D
 intangible asset and the related amortization will be recorded as
 an expense prospectively over its estimated useful life.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The projected discounted cash flow models used to estimate the
 Company&amp;#x2019;s IPR&amp;amp;D reflect significant assumptions regarding
 the estimates a market participant would make in order to evaluate
 a drug development asset, including the following:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;Probability of successfully completing clinical trials
 and obtaining regulatory approval;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;Market size, market growth projections, and market
 share;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;Estimates regarding the timing of and the expected
 costs to advance the Company&amp;#x2019;s clinical programs to
 commercialization;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;Estimates of future cash flows from potential product
 sales; and&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;A discount rate.&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Additionally, to the extent the Company acquire other
 indefinite-lived intangible assets through its business
 combinations, these assets are reviewed for impairment on an annual
 basis or more frequently if indicators of impairment are present.
 If the Company determines that the asset becomes impaired, the
 carrying value is written down to its fair value with the related
 impairment charge recognized in its consolidated statements of
 operations in the period in which the impairment occurs.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Deferred Rent&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company&amp;#x2019;s lease agreements include payment escalations
 and lease incentives (including a leasehold improvement tenant
 allowance). For periods prior to January&amp;#xA0;1, 2019, these
 payments were accrued or deferred as appropriate such that rent
 expense was recognized on a straight-line basis over the respective
 lease terms. Effective January&amp;#xA0;1, 2019, upon the adoption of
 ASC 842, deferred rent was reclassified as a reduction to the
 applicable &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt; asset as further
 described in Note 8.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Fair Value Measurements&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Certain assets and liabilities of the Company are carried at fair
 value under GAAP. Fair value is defined as the exchange price that
 would be received for an asset or paid to transfer a liability (an
 exit price) in the principal or most advantageous market for the
 asset or liability in an orderly transaction between market
 participants on the measurement date. Valuation techniques used to
 measure fair value must maximize the use of observable inputs and
 minimize the use of unobservable inputs. Financial assets and
 liabilities carried at fair value are to be classified and
 disclosed in one of the following three levels of the fair value
 hierarchy, of which the first two are considered observable and the
 last is considered unobservable:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;Level 1&amp;#x2014;Quoted prices in active markets for
 identical assets or liabilities.&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;Level 2&amp;#x2014;Observable inputs (other than
 Level&amp;#xA0;1 quoted prices), such as quoted prices in active
 markets for similar assets or liabilities, quoted prices in markets
 that are not active for identical or similar assets or liabilities,
 or other inputs that are observable or can be corroborated by
 observable market data.&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;Level 3&amp;#x2014;Unobservable inputs that are supported
 by little or no market activity that are significant to determining
 the fair value of the assets or liabilities, including pricing
 models, discounted cash flow methodologies and similar
 techniques.&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Prior to the Merger, the Company&amp;#x2019;s preferred stock warrant
 liability, derivative liability and preferred stock repurchase
 liability were carried at fair value, determined according to
 Level&amp;#xA0;3 inputs in the fair value hierarchy described above
 (See Note&amp;#xA0;4). The Company&amp;#x2019;s cash equivalents, consisting
 of money market funds invested in U.S. Treasury securities, are
 carried at fair value, determined based on Level&amp;#xA0;2 inputs in
 the fair value hierarchy described above (see Note 4). The carrying
 values of the Company&amp;#x2019;s accounts payable and accrued expenses
 approximate their fair values due to the short-term nature of these
 liabilities. The carrying value of the Company&amp;#x2019;s outstanding
 loan and security agreement (the &amp;#x201C;Hercules Loan
 Agreement&amp;#x201D;) with Hercules Capital, Inc.
 (&amp;#x201C;Hercules&amp;#x201D;) approximates its fair value at
 March&amp;#xA0;31, 2019 because the debt bears interest at a variable
 market rate and the Company&amp;#x2019;s credit risk has not materially
 changed since the inception of the agreement. The carrying value of
 the Company&amp;#x2019;s loans under the funding agreements with
 &amp;#xD6;sterreichische Forschungsf&amp;#xF6;rderungsgesellschaft mbH
 (&amp;#x201C;FFG&amp;#x201D;) were recorded at fair value on the opening
 balance sheet of Arsanis as of the date of the Merger, and
 approximates the fair value of the loans at March&amp;#xA0;31, 2019.
 (See Note&amp;#xA0;3).&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Segment Information&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company manages its operations as a single operating segment
 for the purposes of assessing performance and making operating
 decisions. The Company&amp;#x2019;s focus is on the discovery,
 development and commercialization of novel therapeutics for the
 treatment of rare diseases.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Revenue Recognition&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Effective January&amp;#xA0;1, 2018, the Company adopted ASC Topic 606,
 Revenue from Contracts with Customers (&amp;#x201C;ASC 606&amp;#x201D;),
 using the modified retrospective transition method. The modified
 retrospective method requires that the cumulative effect of
 initially applying ASC 606 be recognized as an adjustment to the
 opening balance of retained earnings or accumulated deficit of the
 annual period that includes the date of initial application. The
 Company did not have any arrangements that were in the scope of ASC
 606 on January&amp;#xA0;1, 2018 and thus there was no impact to the
 condensed consolidated financial statements as a result of the
 adoption. This standard applies to all contracts with customers,
 except for contracts that are within the scope of other standards,
 such as collaboration arrangements and leases. Prior to completion
 of the Merger, Arsanis entered into a single &lt;font style="WHITE-SPACE: nowrap"&gt;out-licensing&lt;/font&gt; agreement with Janssen
 Pharmaceuticals, Inc. (see Note 13) that was within the scope of
 ASC 606.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Research and Development Programs&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Proceeds under the research and development incentive program from
 the Austrian government are recognized as other income in an amount
 equal to the qualifying expenses incurred in each period multiplied
 by the applicable reimbursement percentage. Incentive income
 recognized upon incurring qualifying expenses in advance of receipt
 of proceeds from research and development incentives is recorded in
 the consolidated balance sheet as research and development
 incentive receivables.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Research and Development Costs&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Costs associated with internal research and development and
 external research and development services, including drug
 development and preclinical studies, are expensed as incurred.
 Research and development expenses include costs for salaries,
 employee benefits, subcontractors, facility-related expenses,
 depreciation and amortization, stock-based compensation,
 third-party license fees, laboratory supplies, and external costs
 of outside vendors engaged to conduct discovery, preclinical and
 clinical development activities and clinical trials as well as to
 manufacture clinical trial materials, and other costs. The Company
 recognizes external research and development costs based on an
 evaluation of the progress to completion of specific tasks using
 information provided to the Company by its service providers.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Nonrefundable advance payments for goods or services to be received
 in the future for use in research and development activities are
 recorded as prepaid expenses. Such prepaid expenses are recognized
 as an expense when the goods have been delivered or the related
 services have been performed, or when it is no longer expected that
 the goods will be delivered or the services rendered.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Upfront payments, milestone payments and annual maintenance fees
 under license agreements are expensed in the period in which they
 are incurred.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Patent Costs&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 All patent-related costs incurred in connection with filing and
 prosecuting patent applications are expensed as incurred due to the
 uncertainty about the recovery of the expenditure. Amounts incurred
 are classified as general and administrative expenses.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Debt Issuance Costs&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Debt issuance costs consist of payments made to secure commitments
 under certain debt financing arrangements. These amounts are
 recognized as interest expense over the period of the financing
 arrangement using the effective interest method. If the financing
 arrangement is canceled or forfeited, or if the utility of the
 arrangement to the Company is otherwise compromised, these costs
 are recognized as interest expense immediately. The Company&amp;#x2019;s
 consolidated financial statements present debt issuance costs
 related to a recognized debt liability as a direct reduction from
 the carrying amount of that debt liability.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Stock-Based Compensation&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company measures all stock-based awards granted to employees
 and directors based on the fair value on the date of the grant and
 recognizes compensation expense for those awards, net of estimated
 forfeitures, over the requisite service period, which is generally
 the vesting period of the respective award. The Company issues
 stock-based awards with only service-based vesting conditions and
 records the expense for these awards using the straight-line
 method. The Company has not issued any stock-based awards with
 performance-based vesting conditions.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 12px"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt"&gt;
 Effective January&amp;#xA0;1, 2019, the Company adopted ASU No.
 &lt;font style="WHITE-SPACE: nowrap"&gt;2018-07,&amp;#xA0;Compensation&amp;#x2014;Stock&lt;/font&gt;
 Compensation (Topic 718): Improvements to Nonemployee Share-Based
 Payment Accounting&amp;#xA0;(&amp;#x201C;ASU &lt;font style="WHITE-SPACE: nowrap"&gt;2018-07&amp;#x201D;),&lt;/font&gt; which expands the
 scope of Topic 718 to include share-based payment awards to
 nonemployees. As a result, stock-based awards granted to
 consultants and &lt;font style="WHITE-SPACE: nowrap"&gt;non-employees&lt;/font&gt; are accounted for in the
 same manner as awards granted to employees and directors as
 described above. The impact of adoption this new guidance did not
 have a material impact on the Company&amp;#x2019;s consolidated
 financial statements. Prior to the adoption of ASU &lt;font style="WHITE-SPACE: nowrap"&gt;2018-07,&lt;/font&gt; for stock-based awards
 granted to &lt;font style="WHITE-SPACE: nowrap"&gt;non-employee&lt;/font&gt;
 consultants, compensation expense was recognized over the period
 during which services were rendered by such &lt;font style="WHITE-SPACE: nowrap"&gt;non-employee&lt;/font&gt; consultants until
 completed. At the end of each financial reporting period prior to
 completion of the service, the fair value of these awards was
 remeasured using the then-current fair value of the Company&amp;#x2019;s
 common stock and updated assumption inputs in the Black-Scholes
 option-pricing model.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company classifies stock-based compensation expense in its
 consolidated statement of operations and comprehensive loss in the
 same manner in which the award recipient&amp;#x2019;s payroll costs are
 classified or in which the award recipient&amp;#x2019;s service payments
 are classified.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company recognizes compensation expense for only the portion of
 awards that are expected to vest. In developing a forfeiture rate
 estimate, the Company has considered its historical experience to
 estimate &lt;font style="WHITE-SPACE: nowrap"&gt;pre-vesting&lt;/font&gt;
 forfeitures for service-based awards. The impact of a forfeiture
 rate adjustment will be recognized in full in the period of
 adjustment, and if the actual forfeiture rate is materially
 different from the Company&amp;#x2019;s estimate, the Company may be
 required to record adjustments to stock-based compensation expense
 in future periods.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The fair value of each stock option grant is estimated on the date
 of grant using the Black-Scholes option-pricing model. Prior to
 March&amp;#xA0;13, 2019, the Company had been a private company and
 lacked company-specific historical and implied volatility
 information for its stock. Therefore, the Company estimates its
 expected stock price volatility based on the historical volatility
 of publicly traded peer companies and expects to continue to do so
 until it has adequate historical data regarding the volatility of
 its own traded stock price. The expected term of the
 Company&amp;#x2019;s stock options has been determined utilizing the
 &amp;#x201C;simplified&amp;#x201D; method for awards that qualify as
 &amp;#x201C;plain-vanilla&amp;#x201D; options. The expected term of stock
 options granted to &lt;font style="WHITE-SPACE: nowrap"&gt;non-employee&lt;/font&gt; consultants is equal to
 the contractual term of the option award. The risk-free interest
 rate is determined by reference to the U.S. Treasury yield curve in
 effect at the time of grant of the award for time periods
 approximately equal to the expected term of the award. Expected
 dividend yield is based on the fact that the Company has never paid
 cash dividends on common stock and does not expect to pay any cash
 dividends in the foreseeable future.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Preferred Stock Warrant Liability&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Prior to the Merger with Arsanis, the Company classified warrants
 for the purchase of shares of its convertible preferred stock (see
 Note&amp;#xA0;10) as a liability on its consolidated balance sheets as
 these warrants are freestanding financial instruments that may have
 required the Company to transfer assets upon exercise. The warrant
 liability, which consisted of warrants for the purchase of
 Series&amp;#xA0;A and Series&amp;#xA0;B convertible preferred stock, was
 initially recorded at fair value upon the date of issuance of each
 warrant and is subsequently remeasured to fair value at each
 reporting date. Changes in the fair value of the warrant liability
 are recognized as a component of other income (expense), net in the
 consolidated statement of operations and comprehensive loss.
 Concurrent with the closing of the Merger, all X4 preferred stock
 was converted to Arsanis common stock and the X4 preferred stock
 warrants converted to warrants for the purchase of Arsanis common
 stock. The Company assessed the features of the warrants and
 determined that they qualify for classification as permanent
 equity. Accordingly, the Company remeasured the warrants to fair
 value upon the closing of the Merger and reclassified the resulting
 warrant liability to additional &lt;font style="WHITE-SPACE: nowrap"&gt;paid-in&lt;/font&gt; capital. (see
 Note&amp;#xA0;10).&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Derivative Liability&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company&amp;#x2019;s license agreement with Genzyme Corporation
 (&amp;#x201C;Genzyme&amp;#x201D;) (see Note&amp;#xA0;13) contained a contingent
 payment obligation that required the Company to make a cash payment
 to Genzyme upon a change of control event of the Company. The
 contingent payment obligation met the definition of a derivative
 instrument as the contingent payment obligation was not clearly and
 closely related to its host instrument and was a cash-settled
 liability. Accordingly, the Company classified this derivative as a
 liability within other liabilities &lt;font style="WHITE-SPACE: nowrap"&gt;(non-current)&lt;/font&gt; on its condensed
 consolidated balance sheet. The derivative liability was initially
 recorded at fair value on the date of entering into the license
 agreement and was subsequently remeasured to fair value at each
 reporting date. Changes in the fair value of this derivative
 liability were recognized as a component of other income (expense),
 net in the condensed consolidated statement of operations and
 comprehensive loss. The Merger with Arsanis (see Note 1) qualified
 as a change of control event, as defined in the license agreement,
 but resulted in no payment being due to Genzyme under the license
 agreement. As a result, on March&amp;#xA0;13, 2019, the closing date of
 the Merger with Arsanis, the derivative liability was remeasured to
 fair value, which was $0, and subsequent changes in fair value will
 no longer be recognized in the consolidated statements of
 operations and comprehensive loss because the contingent payment
 obligation to Genzyme expired at that time.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 12px"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt"&gt;
 In addition, the Company&amp;#x2019;s Hercules loan (see Note&amp;#xA0;7)
 contains a redemption feature that, upon an event of default,
 provides Hercules the option to accelerate and demand repayment of
 the debt, including a prepayment premium. The redemption feature
 meets the definition of a derivative instrument as the repayment of
 the debt contains a substantial premium, resulting in the
 redemption feature not being clearly and closely related to its
 host instrument. Accordingly, the Company classifies this
 derivative as a liability within other liabilities &lt;font style="WHITE-SPACE: nowrap"&gt;(non-current)&lt;/font&gt; on its condensed
 consolidated balance sheet. The derivative liability was initially
 recorded at fair value on the date of entering into the Hercules
 Loan Agreement and is subsequently remeasured to fair value at each
 reporting date. Changes in the fair value of this derivative
 liability are recognized as a component of other income (expense),
 net in the condensed consolidated statement of operations and
 comprehensive loss. Changes in the fair value of this derivative
 liability will continue to be recognized until all amounts
 outstanding under the Hercules Loan Agreement are repaid or until
 the Hercules Loan Agreement is terminated.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Comprehensive Loss&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Comprehensive loss includes net loss as well as other changes in
 stockholders&amp;#x2019; equity (deficit) that result from transactions
 and economic events other than those with stockholders. For the
 three months ended March&amp;#xA0;31, 2019, comprehensive loss included
 $23 of foreign currency translation gain adjustments.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Income Taxes&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company accounts for income taxes using the asset and liability
 method, which requires the recognition of deferred tax assets and
 liabilities for the expected future tax consequences of events that
 have been recognized in the consolidated financial statements or in
 the Company&amp;#x2019;s tax returns. Deferred tax assets and
 liabilities are determined based on the difference between the
 financial statement and tax basis of assets and liabilities using
 enacted tax rates in effect for the year in which the differences
 are expected to reverse. Changes in deferred tax assets and
 liabilities are recorded in the provision for income taxes. The
 Company assesses the likelihood that its deferred tax assets will
 be recovered from future taxable income and, to the extent it
 believes, based upon the weight of available evidence, that it is
 more likely than not that all or a portion of the deferred tax
 assets will not be realized, a valuation allowance is established
 through a charge to income tax expense. Potential for recovery of
 deferred tax assets is evaluated by estimating the future taxable
 profits expected and considering prudent and feasible tax planning
 strategies.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company accounts for uncertainty in income taxes recognized in
 the consolidated financial statements by applying a &lt;font style="WHITE-SPACE: nowrap"&gt;two-step&lt;/font&gt; process to determine the
 amount of tax benefit to be recognized. First, the tax position
 must be evaluated to determine the likelihood that it will be
 sustained upon external examination by the taxing authorities. If
 the tax position is deemed &lt;font style="WHITE-SPACE: nowrap"&gt;more-likely-than-not&lt;/font&gt; to be sustained,
 the tax position is then assessed to determine the amount of
 benefit to recognize in the consolidated financial statements. The
 amount of the benefit that may be recognized is the largest amount
 that has a greater than 50% likelihood of being realized upon
 ultimate settlement. The provision for income taxes includes the
 effects of any resulting tax reserves, or unrecognized tax
 benefits, that are considered appropriate as well as the related
 net interest and penalties.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Net Income (Loss) per Share&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company follows the &lt;font style="WHITE-SPACE: nowrap"&gt;two-class&lt;/font&gt; method when computing net
 income (loss) per share as the Company has issued shares that meet
 the definition of participating securities. The &lt;font style="WHITE-SPACE: nowrap"&gt;two-class&lt;/font&gt; method determines net income
 (loss) per share for each class of common and participating
 securities according to dividends declared or accumulated and
 participation rights in undistributed earnings. The &lt;font style="WHITE-SPACE: nowrap"&gt;two-class&lt;/font&gt; method requires income
 available to common stockholders for the period to be allocated
 between common and participating securities based upon their
 respective rights to receive dividends as if all income for the
 period had been distributed.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Basic net income (loss) per share attributable to common
 stockholders is computed by dividing the net income (loss)
 attributable to common stockholders by the weighted average number
 of common shares outstanding for the period. Diluted net income
 (loss) attributable to common stockholders is computed by adjusting
 net income (loss) attributable to common stockholders to reallocate
 undistributed earnings based on the potential impact of dilutive
 securities. Diluted net income (loss) per share attributable to
 common stockholders is computed by dividing the diluted net income
 (loss) attributable to common stockholders by the weighted average
 number of common shares outstanding for the period, including
 potential dilutive common shares. For purpose of this calculation,
 outstanding stock options, convertible preferred stock and warrants
 to purchase shares of convertible preferred stock are considered
 potential dilutive common shares.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The Company&amp;#x2019;s convertible preferred stock contractually
 entitles the holders of such shares to participate in dividends but
 does not contractually require the holders of such shares to
 participate in losses of the Company. Accordingly, in periods in
 which the Company reports a net loss attributable to common
 stockholders, such losses are not allocated to such participating
 securities. In periods in which the Company reports a net loss
 attributable to common stockholders, diluted net loss per share
 attributable to common stockholders is the same as basic net loss
 per share attributable to common stockholders, since dilutive
 common shares are not assumed to have been issued if their effect
 is anti-dilutive. The Company reported a net loss attributable to
 common stockholders for the three months ended March&amp;#xA0;31, 2019
 and 2018.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 18px"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt"&gt;
 &lt;b&gt;&lt;i&gt;Recently Adopted Accounting Pronouncements&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 In February 2016, the FASB issued ASU &lt;font style="WHITE-SPACE: nowrap"&gt;No.&amp;#xA0;2016-02&lt;/font&gt;&lt;i&gt;, Leases
 (Topic&lt;/i&gt;&lt;i&gt;&amp;#xA0;842)&lt;/i&gt; (&amp;#x201C;ASU &lt;font style="WHITE-SPACE: nowrap"&gt;2016-02&amp;#x201D;&lt;/font&gt; or &amp;#x201C;ASC
 842&amp;#x201D;)), which sets out the principles for the recognition,
 measurement, presentation and disclosure of leases for both parties
 to a contract (i.e., lessees and lessors). The new standard
 requires lessees to apply a dual approach, classifying leases as
 either finance or operating leases based on the principle of
 whether or not the lease is effectively a financed purchase by the
 lessee. This classification will determine whether lease expense is
 recognized based on an effective interest method or on a
 straight-line basis over the term of the lease. A lessee is also
 required to record a &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt; asset and a lease
 liability for all leases with a term of greater than 12&amp;#xA0;months
 regardless of their classification. Leases with a term of 12 months
 or less may be accounted for similar to prior guidance for
 operating leases. The Company adopted the new leasing standard as
 of the required effective date of January&amp;#xA0;1, 2019 using a
 modified retrospective transition approach to be applied to leases
 existing as of, or entered into after, January&amp;#xA0;1, 2019. The
 adoption had no impact on accumulated deficit. The new lease
 standard provides a number of optional practical expedients in
 transition. The Company applied the package of practical expedients
 to leases that commenced prior to the effective date, whereby it
 will elect to not reassess the following: (i)&amp;#xA0;whether any
 expired or existing contracts contain leases; (ii)&amp;#xA0;the lease
 classification for any expired or existing leases; and
 (iii)&amp;#xA0;initial direct costs for any existing leases. The
 Company also elected the short-term lease recognition exemption for
 all leases that qualify, where a &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt; asset or lease
 liability will not be recognized for short-term leases. Upon the
 adoption of ASC 842, the Company recorded $2.5&amp;#xA0;million of
 operating lease liabilities and $2.0&amp;#xA0;million of &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&amp;#xA0;assets&lt;/font&gt;&lt;/font&gt; on its
 consolidated balance. The adoption did not have a material impact
 on the Company&amp;#x2019;s statement of operations, statement of
 comprehensive loss or statement of cash flows.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 In January 2017, the FASB issued ASU &lt;font style="WHITE-SPACE: nowrap"&gt;No.&amp;#xA0;2017-04,&lt;/font&gt;&lt;i&gt;&amp;#xA0;Intangibles-Goodwill
 and Other (Topic 350): Simplifying the Test for Goodwill
 Impairment.&lt;/i&gt;&amp;#xA0;The new standard simplifies the subsequent
 measurement of goodwill by eliminating the second step of the
 goodwill impairment test. This ASU will be applied prospectively
 and is effective for annual or interim goodwill impairment tests in
 fiscal years beginning after December&amp;#xA0;15, 2019 with early
 adoption permitted. The Company has adopted this guidance on
 January&amp;#xA0;1, 2019 and will apply it to its annual impairment
 test, and any interim impairment tests during the year ending
 December&amp;#xA0;31, 2019.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 In April 2017, the FASB issued ASU &lt;font style="WHITE-SPACE: nowrap"&gt;2017-08,&lt;/font&gt;&lt;i&gt;&amp;#xA0;Receivables &amp;#x2013;
 Nonrefundable Fees and Other Costs&lt;/i&gt; (&amp;#x201C;Subtopic
 &lt;font style="WHITE-SPACE: nowrap"&gt;310-20&amp;#x201D;).&lt;/font&gt; The new
 standard amends the amortization period for certain purchased
 callable debt securities held at a premium by shortening the
 amortization period for the premium to the earliest call
 date.&amp;#xA0;Subtopic &lt;font style="WHITE-SPACE: nowrap"&gt;310-20&lt;/font&gt;
 calls for a modified retrospective application under which&amp;#xA0;a
 cumulative-effect adjustment will be made to retained earnings as
 of the beginning of the first reporting period in which the
 guidance is adopted.&amp;#xA0;The new standard will be effective
 beginning January&amp;#xA0;1, 2019 and early adoption is permitted for
 public entities.&amp;#xA0;The Company adopted this guidance, effective
 January&amp;#xA0;1, 2019, and its adoption had no impact on the
 Company&amp;#x2019;s financial position, results of operations or cash
 flows.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 In July 2017, the FASB issued ASU &lt;font style="WHITE-SPACE: nowrap"&gt;No.&amp;#xA0;2017-11,&lt;/font&gt; &lt;i&gt;Earnings Per
 Share (Topic&lt;/i&gt;&lt;i&gt;&amp;#xA0;260), Distinguishing Liabilities from
 Equity (Topic&lt;/i&gt;&lt;i&gt;&amp;#xA0;480), Derivatives and Hedging
 (Topic&lt;/i&gt;&lt;i&gt;&amp;#xA0;815) (Part&lt;/i&gt;&lt;i&gt;&amp;#xA0;I) Accounting for Certain
 Financial Instruments with Down Round Features
 (Part&lt;/i&gt;&lt;i&gt;&amp;#xA0;II) Replacement of the Indefinite Deferral for
 Mandatorily Redeemable Financial Instruments of Certain Nonpublic
 Entities and Certain Mandatorily Redeemable Noncontrolling
 Interests with a Scope Exception&lt;/i&gt; (&amp;#x201C;ASU &lt;font style="WHITE-SPACE: nowrap"&gt;2017-11&amp;#x201D;).&lt;/font&gt; Part&amp;#xA0;I applies
 to entities that issue financial instruments such as warrants,
 convertible debt or convertible preferred stock that contain
 down-round features. Part&amp;#xA0;II replaces the indefinite deferral
 for certain mandatorily redeemable noncontrolling interests and
 mandatorily redeemable financial instruments of nonpublic entities
 contained within ASC Topic&amp;#xA0;480 with a scope exception and does
 not impact the accounting for these mandatorily redeemable
 instruments. For public entities, ASU &lt;font style="WHITE-SPACE: nowrap"&gt;2017-11&lt;/font&gt; is effective for annual
 reporting periods beginning after December&amp;#xA0;15, 2018, including
 interim periods within those fiscal years. The Company adopted ASU
 &lt;font style="WHITE-SPACE: nowrap"&gt;2017-11&lt;/font&gt; as of the required
 effective date of January&amp;#xA0;1, 2019. The adoption of ASU
 &lt;font style="WHITE-SPACE: nowrap"&gt;2017-11&lt;/font&gt; had no impact on
 the Company&amp;#x2019;s financial position, results of operations or
 cash flows.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 In June 2018, the FASB issued ASU &lt;font style="WHITE-SPACE: nowrap"&gt;No.&amp;#xA0;2018-07,&lt;/font&gt;
 &lt;i&gt;Compensation&amp;#x2014;Stock Compensation (Topic&lt;/i&gt;&lt;i&gt;&amp;#xA0;718):
 Improvements to Nonemployee Share-Based Payment Accounting&lt;/i&gt;
 (&amp;#x201C;ASU &lt;font style="WHITE-SPACE: nowrap"&gt;2018-07&amp;#x201D;).&lt;/font&gt; These amendments
 expand the scope of Topic&amp;#xA0;718, Compensation&amp;#x2014;Stock
 Compensation (which previously only included share-based payments
 to employees) to include share-based payments issued to
 &lt;font style="WHITE-SPACE: nowrap"&gt;non-employees&lt;/font&gt; for goods or
 services. Consequently, the accounting for share-based payments to
 &lt;font style="WHITE-SPACE: nowrap"&gt;non-employees&lt;/font&gt; and
 employees will be substantially aligned. The ASU supersedes
 &lt;font style="WHITE-SPACE: nowrap"&gt;Subtopic&amp;#xA0;505-50,&lt;/font&gt;
 Equity&amp;#x2014;&lt;i&gt;Equity-Based Payments to &lt;font style="WHITE-SPACE: nowrap"&gt;Non-Employees&lt;/font&gt;&lt;/i&gt;. The Company adopted
 ASU &lt;font style="WHITE-SPACE: nowrap"&gt;2018-07&lt;/font&gt; on
 January&amp;#xA0;1, 2019. The adoption of this standard had no impact
 on the Company&amp;#x2019;s financial statements.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Recently Issued Accounting Pronouncements&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 In August 2018, the FASB issued ASU &lt;font style="WHITE-SPACE: nowrap"&gt;No.&amp;#xA0;2018-13,&lt;/font&gt; &lt;i&gt;Fair Value
 Measurement (Topic 820): Disclosure Framework&amp;#x2014;Changes to the
 Disclosure Requirements for Fair Value Measurement&lt;/i&gt; (&amp;#x201C;ASU
 &lt;font style="WHITE-SPACE: nowrap"&gt;2018-13&amp;#x201D;),&lt;/font&gt;
 which&amp;#xA0;removes, adds and modifies certain disclosure
 requirements for fair value measurements in Topic 820. The Company
 will no longer be required to disclose the amount of and reasons
 for transfers between Level&amp;#xA0;1 and Level&amp;#xA0;2 of the fair
 value hierarchy as well as the valuation processes of Level&amp;#xA0;3
 fair value measurements. However, the Company will be required to
 additionally disclose the changes in unrealized gains and losses
 included in other comprehensive income for recurring Level&amp;#xA0;3
 fair value measurements and the range and weighted average of
 assumptions used to develop significant unobservable inputs for
 Level&amp;#xA0;3 fair value measurements. ASU &lt;font style="WHITE-SPACE: nowrap"&gt;2018-13&lt;/font&gt; is effective for fiscal years,
 and interim periods within those fiscal years, beginning after
 December&amp;#xA0;15, 2019. The amendments relating to additional
 disclosure requirements will be applied prospectively for only the
 most recent interim or annual period presented in the initial year
 of adoption. All other amendments will be applied retrospectively
 to all periods presented upon their effective date. The Company is
 currently evaluating the impact that the adoption of ASU
 &lt;font style="WHITE-SPACE: nowrap"&gt;2018-13&lt;/font&gt; will have on its
 consolidated financial statements.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 In August 2018, the FASB issued ASU &lt;font style="WHITE-SPACE: nowrap"&gt;2018-15,&lt;/font&gt;&lt;i&gt;&amp;#xA0;Intangibles-Goodwill
 and &lt;font style="WHITE-SPACE: nowrap"&gt;Other-Internal-Use&lt;/font&gt;
 Software (Subtopic &lt;font style="WHITE-SPACE: nowrap"&gt;350-40):&lt;/font&gt; Customer&amp;#x2019;s Accounting
 for Implementation Costs Incurred in a Cloud Computing Arrangement
 That Is a Service Contract, (&amp;#x201C;ASU &lt;font style="WHITE-SPACE: nowrap"&gt;2018-15&amp;#x201D;)&lt;/font&gt;&lt;/i&gt;. The amendments in
 this update align the requirements for capitalizing implementation
 costs incurred in a hosting arrangement that is a service contract
 with the requirements for capitalizing implementation costs
 incurred to develop or obtain &lt;font style="WHITE-SPACE: nowrap"&gt;internal-use&lt;/font&gt; software (and hosting
 arrangements that include an &lt;font style="WHITE-SPACE: nowrap"&gt;internal-use&lt;/font&gt; software license). The
 accounting for the service element of a hosting arrangement that is
 a service contract is not affected by the amendments in this
 update. The new standard will be effective beginning
 January&amp;#xA0;1, 2020 and early adoption is permitted. The
 amendments in this update should be applied either retrospectively
 or prospectively to all implementation costs incurred after the
 date of adoption.&amp;#xA0;The Company is currently evaluating the
 impact that the adoption of ASU &lt;font style="WHITE-SPACE: nowrap"&gt;2018-15&lt;/font&gt; will have on its consolidated
 financial statements.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:SignificantAccountingPoliciesTextBlock>
  <us-gaap:StockIssuedDuringPeriodValueStockOptionsExercised contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_AF788C25-DA69-4060-97BB-D7B7447FD5A4_5008_1100011" unitRef="iso4217_USD">113000</us-gaap:StockIssuedDuringPeriodValueStockOptionsExercised>
  <us-gaap:ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_1BC34F3A-22F1-4659-9B41-9154980DE11F_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The following summarizes the preliminary estimate of the purchase
 price paid in the Merger:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="85%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="9%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Number of shares of the combined organization owned by Arsanis
 stockholders&amp;#xA0;(1)&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2,440,582&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Multiplied by the fair value per share of Arsanis common
 stock&amp;#xA0;(2)&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;18.66&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Fair value of consideration issued it effect the Merger&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;45,541&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Fair value of replacement awards held by former employees, board of
 directors and consultants of Arsanis that were vested as of the
 Merger.&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;817&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Purchase price:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;46,358&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 2pt; FONT-SIZE: medium; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WIDTH: 124px; WHITE-SPACE: normal; WORD-SPACING: 0px; BORDER-BOTTOM: rgb(0,0,0) 1px solid; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; LINE-HEIGHT: 8pt; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;(1)&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;The number of shares of 2,440,582 represents the
 historical 14,643,737 shares of Arsanis common stock outstanding
 immediately prior to the closing of the Merger, adjusted for the
 Reverse Stock Split.&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;(2)&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;Based on the last reported sale price of Arsanis
 common stock on the Nasdaq Global Market on March&amp;#xA0;13, 2019,
 the closing date of the Merger, and gives effect to the Reverse
 Stock Split.&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;/div&gt;</us-gaap:ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTextBlock>
  <us-gaap:ScheduleOfDebtTableTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_D2716E5E-0CE9-46D4-8B2D-5B008A4562B0_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Long-term debt consisted of the following:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="72%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="8%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="8%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;March&amp;#xA0;31,&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;2019&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;December&amp;#xA0;31,&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;2018&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Principal amount of long-term debt&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19,546&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;10,000&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Less: Current portion of long-term debt&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(5,298&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(1,687&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Long-term debt, net of current portion&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;14,248&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,313&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Debt discount, net of accretion&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(1,019&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(226&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Cumulative accretion of final payment due at maturity&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;136&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;58&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Long-term debt, including accretion, net of current portion&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;13,365&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,145&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;br class="Apple-interchange-newline" /&gt;&lt;/div&gt;</us-gaap:ScheduleOfDebtTableTextBlock>
  <us-gaap:ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_E4B8BCA0-775C-469D-ACCE-2CBDE918D1E6_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Basic and diluted net loss per share attributable to common
 stockholders was calculated as follow:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="75%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="6%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="6%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="6" align="center"&gt;&lt;b&gt;Three Months Ended&lt;br /&gt;
 March&amp;#xA0;31,&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2019&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2018&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Numerator:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 5em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Net loss&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(10,873&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(7,367&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 5em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Accruing dividends on Series A convertible preferred stock&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(592&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(740&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 5em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Net loss attributable to common stockholders&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(11,465&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(8,107&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Denominator:&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Weighted average common shares outstanding&amp;#x2014;basic and
 diluted&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,717,808&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;457,971&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Net loss per share attributable to common stockholders&amp;#x2014;basic
 and diluted&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(6.67&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(17.70&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;br class="Apple-interchange-newline" /&gt;

 &lt;/div&gt;</us-gaap:ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock>
  <us-gaap:ScheduleOfMaturitiesOfLongTermDebtTableTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_3CC2B1FB-8767-4FBF-8580-29CD7119768E_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 As of March&amp;#xA0;31, 2019, future principal payments and the final
 payment due under the Company&amp;#x2019;s loan agreements were as
 follows:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="68%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="61%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="5%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="5%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="5%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;Year Ending December&amp;#xA0;31,&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Hercules&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;FFG&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Total&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2019&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,345&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2,914&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,259&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2020&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,305&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,462&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,767&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 2021&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,350&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2,170&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;6,520&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Long-term debt&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;
 &amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;10,000&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;
 &amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;9,546&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19,546&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;/div&gt;</us-gaap:ScheduleOfMaturitiesOfLongTermDebtTableTextBlock>
  <us-gaap:ScheduleOfShareBasedPaymentAwardEmployeeStockPurchasePlanValuationAssumptionsTableTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_CE5E6F08-DD9E-46D8-B3E2-D3A490712D21_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The following table presents, on a weighted average basis, the
 assumptions used in the Black-Scholes option-pricing model to
 determine the grant-date fair value of stock options granted to
 employees, directors and &lt;font style="WHITE-SPACE: nowrap"&gt;non-&lt;/font&gt; employees:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="80%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="7%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="7%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="6" align="center"&gt;&lt;b&gt;Three Months Ended&lt;br /&gt;
 March&amp;#xA0;31,&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2019&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;2018&amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Risk-free interest rate&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2.4&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;%&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2.8&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;%&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Expected term (in years)&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5.90&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5.94&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Expected volatility&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;90.6&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;%&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;86.0&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;%&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Expected dividend yield&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;0&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;%&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;0&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;%&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;/div&gt;</us-gaap:ScheduleOfShareBasedPaymentAwardEmployeeStockPurchasePlanValuationAssumptionsTableTextBlock>
  <us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="2" id="id_13073811_8F24BC0F-1335-4625-993E-6C8BB0CDE523_1_3" unitRef="pure">0.00</us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate>
  <us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="3" id="id_13073811_8F24BC0F-1335-4625-993E-6C8BB0CDE523_1_0" unitRef="pure">0.024</us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate>
  <us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="INF" id="id_13073811_73B62E47-DB55-41EC-AE91-BF83DD2EEEAC_5001_400005" unitRef="shares">22378</us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod>
  <us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_017F787D-60B9-463C-95F5-35D9FA332CDB_1_0">These Plans are administered by the board of directors or, at the discretion of the board of directors, by a committee of the board of directors. The exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, or its committee if so delegated, except that the exercise price per share of stock options may not be less than 100% of the fair market value of the share of common stock on the date of grant and the term of the stock option may not be greater than ten years.</us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription>
  <us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="3" id="id_13073811_8F24BC0F-1335-4625-993E-6C8BB0CDE523_1_2" unitRef="pure">0.906</us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate>
  <us-gaap:ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_27B3A1EC-760A-4554-9176-5BA012A2AFFF_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The following summarizes the allocation of the purchase price to
 the net tangible and intangible assets acquired:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="85%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="6%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Cash and cash equivalents and restricted cash&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;26,406&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Other current assets&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2,147&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Property and equipment, net&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;68&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 IPR&amp;amp;D indefinite-lived intangible assets&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,900&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Other assets,&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-current&lt;/font&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;879&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Current liabilities&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(5,221&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Loans payable&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(8,713&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Other liabilities,&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-current&lt;/font&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(1,515&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Goodwill&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;27,407&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Purchase price&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;
 &amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;46,358&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;br class="Apple-interchange-newline" /&gt;&lt;/div&gt;</us-gaap:ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock>
  <us-gaap:ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_7DB5D6EC-C05A-481D-89F3-E9B3CF271FB3_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The following table summarizes the Company&amp;#x2019;s stock option
 activity since December&amp;#xA0;31, 2018:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="92%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="61%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="5%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="5%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="5%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="5%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Number&amp;#xA0;of&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Shares&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Weighted&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Average&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Exercise&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Price&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Weighted&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Average&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Contractual&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Term&amp;#xA0;(Years)&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Aggregate&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Intrinsic&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Value&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Outstanding as of December&amp;#xA0;31, 2018&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;797,931&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8.29&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;8.42&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;6,486&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Assumed as part of Merger with Arsanis&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;271,230&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;
 &amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;62.60&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Granted&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;136,913&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;17.22&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Exercised&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(16,483&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;6.85&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Forfeited&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;(22,378&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;)&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8.43&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Outstanding as of March&amp;#xA0;31, 2019&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,167,213&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;21.97&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;7.65&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;7,168&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Exercisable as of March&amp;#xA0;31, 2019&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;556,774&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;30.13&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Vested and expected to vest as of March&amp;#xA0;31, 2019&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;979,466&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;48.79&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/div&gt;</us-gaap:ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock>
  <us-gaap:ScheduleOfStockholdersEquityNoteWarrantsOrRightsTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_45BD644C-780E-43FB-8C8C-BBF59AF76E2F_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 As of March&amp;#xA0;31, 2019, the Company&amp;#x2019;s outstanding warrants
 to purchase shares of common stock consisted of the following:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="80%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="60%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="3%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="3%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="3%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="3%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; BORDER-BOTTOM: rgb(0,0,0) 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell"&gt;
 &lt;b&gt;Issuance Date&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Number&amp;#xA0;of&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Shares of&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Common&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Stock&amp;#xA0;Issuable&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Exercise&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Price&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Classification&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Expiration&amp;#xA0;Date&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 August&amp;#xA0;14, 2015&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;81,228&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;21.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;August&amp;#xA0;14,&amp;#xA0;2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 August&amp;#xA0;21, 2015&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;69,603&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;21.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;August&amp;#xA0;21, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 October&amp;#xA0;25, 2016&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5,155&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;24, 2026&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 November&amp;#xA0;1, 2017&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;130,609&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;31,&amp;#xA0;2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 November&amp;#xA0;17, 2017&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;8,442&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;November&amp;#xA0;16, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 December&amp;#xA0;4, 2017&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5,661&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;3, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 December&amp;#xA0;28, 2017&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;6,925&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;27, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 December&amp;#xA0;28, 2017&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;115,916&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;28, 2027&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 September&amp;#xA0;12, 2018&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;25,275&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;September&amp;#xA0;12,&amp;#xA0;2021&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 September&amp;#xA0;12, 2018&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;20,220&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;September&amp;#xA0;12, 2028&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 October&amp;#xA0;19, 2018&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;20,016&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.78&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;19, 2028&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 December&amp;#xA0;11, 2018&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5,004&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19.80&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Equity&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;19, 2028&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;494,054&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 As of December&amp;#xA0;31, 2018, the Company&amp;#x2019;s outstanding
 warrants to purchase shares of preferred stock (which converted
 into warrants to purchase common stock upon close of the Merger)
 consisted of the following (not adjusted for the Reverse Stock
 Split or Exchange Ratio):&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="32%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="24" nowrap="nowrap" align="center"&gt;
 &lt;p style="MARGIN-BOTTOM: 1pt; FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="center"&gt;&lt;b&gt;December&amp;#xA0;31, 2018&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 9pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 9pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; BORDER-BOTTOM: rgb(0,0,0) 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell"&gt;
 &lt;b&gt;Warrant Name&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Issuance Date&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Number&amp;#xA0;of&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Shares of&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Preferred&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Stock&amp;#xA0;Issuable&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Exercise&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Price&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Exercisable&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;for&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Classification&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Expiration Date&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series A warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;August&amp;#xA0;14, 2015&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;854,785&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2.07&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series&amp;#xA0;A&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;August&amp;#xA0;14, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series A warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;August&amp;#xA0;21, 2015&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;732,453&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2.07&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series A&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;August&amp;#xA0;21, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 SVB warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;25, 2016&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;54,256&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series A&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;24, 2026&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;November&amp;#xA0;1, 2017&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,374,435&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;31, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;November&amp;#xA0;17, 2017&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;88,845&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;November&amp;#xA0;16, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;4, 2017&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;59,576&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;3, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;28, 2017&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;72,875&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;27, 2020&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;28, 2017&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,219,815&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;December&amp;#xA0;28, 2027&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;September&amp;#xA0;12, 2018&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;265,957&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;September&amp;#xA0;12,&amp;#xA0;2021&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;September&amp;#xA0;12,&amp;#xA0;2018&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;212,765&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;September&amp;#xA0;12, 2028&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B warrants&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;19, 2018&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;210,638&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1.88&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Series B&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;Liability&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;October&amp;#xA0;19, 2028&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;5,146,400&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;br class="Apple-interchange-newline" /&gt;

 &lt;/div&gt;</us-gaap:ScheduleOfStockholdersEquityNoteWarrantsOrRightsTextBlock>
  <us-gaap:SegmentReportingPolicyPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_6B865A6E-20D4-4A50-AD57-25EA9FDAAC28_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Segment Information&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company manages its operations as a single operating segment
 for the purposes of assessing performance and making operating
 decisions. The Company&amp;#x2019;s focus is on the discovery,
 development and commercialization of novel therapeutics for the
 treatment of rare diseases.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:SegmentReportingPolicyPolicyTextBlock>
  <us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_BB7D5514-A78B-4C83-ABBC-5CD6F99BD440_5001_2" unitRef="iso4217_USD">0</us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue>
  <us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="INF" id="id_13073811_E23A72E6-2EB5-4F4A-B04B-4DB66A036609_1_0" unitRef="shares">136913</us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross>
  <us-gaap:TemporaryEquityAccretionToRedemptionValueAdjustment contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_5407D593-0C59-4365-B2A1-7886CC26A113_1_2" unitRef="iso4217_USD">592000</us-gaap:TemporaryEquityAccretionToRedemptionValueAdjustment>
  <us-gaap:TemporaryEquityDividendsAdjustment contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_29777C2D-E0DB-433D-BA39-674C4E97CEBC_1_12" unitRef="iso4217_USD">592000</us-gaap:TemporaryEquityDividendsAdjustment>
  <dei:TradingSymbol contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_A7F8FC82-9EF2-433E-A4E3-49D3C0BA9AB7_1_0">XFOR</dei:TradingSymbol>
  <us-gaap:ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="2" id="id_13073811_E685F46A-0EFF-4A61-907A-DD6330BCD82D_5001_5" unitRef="iso4217_USD_per_shares">8.43</us-gaap:ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice>
  <us-gaap:ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="2" id="id_13073811_E685F46A-0EFF-4A61-907A-DD6330BCD82D_5001_3" unitRef="iso4217_USD_per_shares">17.22</us-gaap:ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice>
  <us-gaap:ShareBasedCompensationOptionAndIncentivePlansPolicy contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_BA7A653E-D56E-449D-AA3A-042759DA6A38_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Stock-Based Compensation&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The Company measures all stock-based awards granted to employees
 and directors based on the fair value on the date of the grant and
 recognizes compensation expense for those awards, net of estimated
 forfeitures, over the requisite service period, which is generally
 the vesting period of the respective award. The Company issues
 stock-based awards with only service-based vesting conditions and
 records the expense for these awards using the straight-line
 method. The Company has not issued any stock-based awards with
 performance-based vesting conditions.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Effective January&amp;#xA0;1, 2019, the Company adopted ASU
 No.&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2018-07,&amp;#xA0;Compensation&amp;#x2014;Stock&lt;/font&gt;&amp;#xA0;Compensation
 (Topic 718): Improvements to Nonemployee Share-Based Payment
 Accounting&amp;#xA0;(&amp;#x201C;ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2018-07&amp;#x201D;),&lt;/font&gt;&amp;#xA0;which
 expands the scope of Topic 718 to include share-based payment
 awards to nonemployees. As a result, stock-based awards granted to
 consultants and&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-employees&lt;/font&gt;&amp;#xA0;are
 accounted for in the same manner as awards granted to employees and
 directors as described above. The impact of adoption this new
 guidance did not have a material impact on the Company&amp;#x2019;s
 consolidated financial statements. Prior to the adoption of
 ASU&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;2018-07,&lt;/font&gt;&amp;#xA0;for
 stock-based awards granted to&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-employee&lt;/font&gt;consultants, compensation
 expense was recognized over the period during which services were
 rendered by such&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-employee&lt;/font&gt;&amp;#xA0;consultants
 until completed. At the end of each financial reporting period
 prior to completion of the service, the fair value of these awards
 was remeasured using the then-current fair value of the
 Company&amp;#x2019;s common stock and updated assumption inputs in the
 Black-Scholes option-pricing model.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The Company classifies stock-based compensation expense in its
 consolidated statement of operations and comprehensive loss in the
 same manner in which the award recipient&amp;#x2019;s payroll costs are
 classified or in which the award recipient&amp;#x2019;s service payments
 are classified.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The Company recognizes compensation expense for only the portion of
 awards that are expected to vest. In developing a forfeiture rate
 estimate, the Company has considered its historical experience to
 estimate&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;pre-vesting&lt;/font&gt;&amp;#xA0;forfeitures
 for service-based awards. The impact of a forfeiture rate
 adjustment will be recognized in full in the period of adjustment,
 and if the actual forfeiture rate is materially different from the
 Company&amp;#x2019;s estimate, the Company may be required to record
 adjustments to stock-based compensation expense in future
 periods.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The fair value of each stock option grant is estimated on the date
 of grant using the Black-Scholes option-pricing model. Prior to
 March&amp;#xA0;13, 2019, the Company had been a private company and
 lacked company-specific historical and implied volatility
 information for its stock. Therefore, the Company estimates its
 expected stock price volatility based on the historical volatility
 of publicly traded peer companies and expects to continue to do so
 until it has adequate historical data regarding the volatility of
 its own traded stock price. The expected term of the
 Company&amp;#x2019;s stock options has been determined utilizing the
 &amp;#x201C;simplified&amp;#x201D; method for awards that qualify as
 &amp;#x201C;plain-vanilla&amp;#x201D; options. The expected term of stock
 options granted to&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-employee&lt;/font&gt;&amp;#xA0;consultants
 is equal to the contractual term of the option award. The risk-free
 interest rate is determined by reference to the U.S. Treasury yield
 curve in effect at the time of grant of the award for time periods
 approximately equal to the expected term of the award. Expected
 dividend yield is based on the fact that the Company has never paid
 cash dividends on common stock and does not expect to pay any cash
 dividends in the foreseeable future.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:ShareBasedCompensationOptionAndIncentivePlansPolicy>
  <us-gaap:ShortTermLeaseCost contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_B25143D0-B17D-4DC9-8A68-2788822ABB32_1_1" unitRef="iso4217_USD">8000</us-gaap:ShortTermLeaseCost>
  <us-gaap:StockIssuedDuringPeriodValueAcquisitions contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_AF788C25-DA69-4060-97BB-D7B7447FD5A4_5008_1100007" unitRef="iso4217_USD">45541000</us-gaap:StockIssuedDuringPeriodValueAcquisitions>
  <us-gaap:SubsequentEventsTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_0E5453C5-634D-4DC7-B957-0ECBC5A18530_1_0">&lt;div&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;&lt;b&gt;16.&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;&lt;b&gt;Subsequent Events&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 On April&amp;#xA0;12, 2019, the Company entered into an underwriting
 agreement with Cowen and Company, LLC and Stifel,
 Nicolaus&amp;#xA0;&amp;amp; Company, Incorporated, as representatives of
 the several underwriters named therein pursuant to which it sold
 5,670,000 shares of common stock and, in lieu of common
 stock,&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;pre-funded&lt;/font&gt;&amp;#xA0;warrants
 to purchase 2,130,000 shares of common stock, and accompanying
 Class&amp;#xA0;A warrants to purchase 3,900,000 shares of its common
 stock, at a price to the public of $11.00 per share and
 accompanying Class&amp;#xA0;A warrants (or $10.999
 per&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;pre-funded&lt;/font&gt;&amp;#xA0;warrant
 and accompanying Class&amp;#xA0;A&amp;#xA0;warrants).&amp;#xA0;The Class&amp;#xA0;A
 warrants have an exercise price of $13.20, will expire five years
 from the date of issuance, and are immediately exercisable with
 certain restrictions. The gross proceeds from the offering were
 $85.8&amp;#xA0;million before deducting underwriting discounts and
 estimated offering expenses. The offering closed on April&amp;#xA0;16,
 2019.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:SubsequentEventsTextBlock>
  <us-gaap:StockholdersEquityNoteDisclosureTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_A4958204-6DB4-417E-B417-35A42884F165_1_0">&lt;div&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;&lt;b&gt;11.&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;&lt;b&gt;Common Stock, Redeemable Common Stock, and
 Convertible Preferred Stock (converted to Common Stock)&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Common Stock&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 As of March&amp;#xA0;31, 2019 and December&amp;#xA0;31, 2018, the
 Company&amp;#x2019;s certificate of incorporation, as amended and
 restated, authorized the Company to issue 33,333,333 shares and
 11,070,776, shares, respectively, of $0.001 par value common stock.
 The voting, dividend and liquidation rights of the holders of the
 Company&amp;#x2019;s common stock are subject to and qualified by the
 rights, powers and preferences of the holders of the preferred
 stock.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Each share of common stock entitles the holder to one vote on all
 matters submitted to a vote of the Company&amp;#x2019;s stockholders.
 Common stockholders are entitled to receive dividends, as may be
 declared by the board of directors, if any. Through March&amp;#xA0;31,
 2019 and December&amp;#xA0;31, 2018, no cash dividends had been
 declared or paid.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Redeemable Common Stock&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Pursuant to the requirements of the July 2014 license agreement
 with Genzyme (see Note&amp;#xA0;13), in August 2015, the Company issued
 to Genzyme for no additional consideration 107,371, as adjusted for
 the Reverse Stock Split and Exchange Ratio, shares of common stock,
 which had an aggregate fair value of $734 on the date of issuance.
 Genzyme had the right to require the Company to repurchase all, but
 not less than all, of these shares of common stock at any time
 during the term of the license agreement for a price of $0.01 per
 share. Because of this redemption feature, the shares of common
 stock issued to Genzyme were classified outside of
 stockholders&amp;#x2019; deficit on the consolidated balance sheets. As
 a result of the Merger, these shares were exchanged for common
 stock.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Convertible Preferred Stock (converted to Common
 Stock)&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The Company has issued Series Seed convertible preferred stock (the
 &amp;#x201C;Series Seed preferred stock&amp;#x201D;), Series&amp;#xA0;A
 convertible preferred stock (the &amp;#x201C;Series&amp;#xA0;A preferred
 stock&amp;#x201D;) and Series&amp;#xA0;B convertible preferred stock (the
 &amp;#x201C;Series&amp;#xA0;B preferred stock&amp;#x201D;). As of March&amp;#xA0;31,
 2019 and December&amp;#xA0;31, 2018, the Company&amp;#x2019;s certificate of
 incorporation, as amended and restated, authorized the Company to
 issue a total of 10,000,000 shares and 59,413,523 shares,
 respectively, of preferred stock, with a par value of $0.001 per
 share.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The holders of Preferred Stock have liquidation rights in the event
 of a deemed liquidation that, in certain situations, are not solely
 within the control of the Company. Therefore, the Preferred Stock
 is classified outside of stockholders&amp;#x2019; deficit on the
 consolidated balance sheet.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 As of March&amp;#xA0;31, 2019, there were no preferred stock
 outstanding. As of December&amp;#xA0;31, 2018, the Preferred Stock
 consisted of the following:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="57%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="18" align="center"&gt;&lt;b&gt;December&amp;#xA0;31, 2018&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Preferred&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Stock&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Designated&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Preferred&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Stock&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Issued and&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Outstanding&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Carrying&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Value&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Liquidation&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Preference&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Common&lt;br /&gt;
 Stock&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Issuable&lt;br /&gt;
 Upon&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Conversion(1)&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series Seed preferred stock&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2,313,523&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,516,136&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,310&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,444&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;143,630&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series A preferred stock&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;22,000,000&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19,946,862&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;32,480&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;47,624&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,895,610&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B preferred stock&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;25,100,000&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;18,616,569&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;30,885&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;34,999&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,769,190&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;49,413,523&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;40,079,567&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;64,675&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;84,067&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;3,808,430&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;(1)&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;Adjusted to reflect Reverse Stock Split and Exchange
 Ratio.&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;


 &lt;/div&gt;</us-gaap:StockholdersEquityNoteDisclosureTextBlock>
  <us-gaap:StockIssuedDuringPeriodSharesStockOptionsExercised contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="INF" id="id_13073811_73B62E47-DB55-41EC-AE91-BF83DD2EEEAC_5001_400004" unitRef="shares">16483</us-gaap:StockIssuedDuringPeriodSharesStockOptionsExercised>
  <us-gaap:StockIssuedDuringPeriodValueConversionOfConvertibleSecurities contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_AF788C25-DA69-4060-97BB-D7B7447FD5A4_5008_1100005" unitRef="iso4217_USD">64675000</us-gaap:StockIssuedDuringPeriodValueConversionOfConvertibleSecurities>
  <us-gaap:TemporaryEquityTableTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_7E2333FA-9294-41C5-831E-970454D005B6_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 As of March&amp;#xA0;31, 2019, there were no preferred stock
 outstanding. As of December&amp;#xA0;31, 2018, the Preferred Stock
 consisted of the following:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="57%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="2%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="18" align="center"&gt;&lt;b&gt;December&amp;#xA0;31, 2018&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Preferred&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Stock&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Designated&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Preferred&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Stock&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Issued and&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Outstanding&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Carrying&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Value&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Liquidation&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Preference&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;Common&lt;br /&gt;
 Stock&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Issuable&lt;br /&gt;
 Upon&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;Conversion(1)&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series Seed preferred stock&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;2,313,523&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,516,136&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,310&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,444&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;143,630&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series A preferred stock&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;22,000,000&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;19,946,862&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;32,480&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;47,624&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,895,610&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Series B preferred stock&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;25,100,000&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;18,616,569&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;30,885&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;34,999&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,769,190&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;49,413,523&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;40,079,567&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;64,675&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;84,067&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;3,808,430&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;(1)&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;Adjusted to reflect Reverse Stock Split and Exchange
 Ratio.&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;


 &lt;/div&gt;</us-gaap:TemporaryEquityTableTextBlock>
  <us-gaap:UseOfEstimates contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_43C2BFF8-2BB0-4C1E-A472-69423DFCE40C_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Use of Estimates&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The preparation of the Company&amp;#x2019;s condensed consolidated
 financial statements in conformity with GAAP requires management to
 make estimates and assumptions that affect the reported amounts of
 assets and liabilities, the disclosure of contingent assets and
 liabilities at the date of the consolidated financial statements,
 and the reported amounts of expenses during the reporting period.
 Significant estimates and assumptions reflected in these
 consolidated financial statements include, but are not limited to,
 the accrual of research and development expenses, the valuation of
 intangible assets acquired in business combinations, the valuations
 of common stock prior to the Merger, the valuation of stock
 options, preferred stock warrants (and the resulting preferred
 stock warrant liability), derivative instruments (and the resulting
 derivative liability), and the preferred stock repurchase
 liability, and valuation of lease liabilities. The Company bases
 its estimates on historical experience, known trends and other
 market-specific or other relevant factors that it believes to be
 reasonable under the circumstances. On an ongoing basis, management
 evaluates its estimates when there are changes in circumstances,
 facts and experience. Changes in estimates are recorded in the
 period in which they become known. Actual results could differ from
 those estimates.&lt;/p&gt;
 &lt;/div&gt;</us-gaap:UseOfEstimates>
  <us-gaap:WeightedAverageNumberOfShareOutstandingBasicAndDiluted contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="0" id="id_13073811_29777C2D-E0DB-433D-BA39-674C4E97CEBC_1_15" unitRef="shares">1717808</us-gaap:WeightedAverageNumberOfShareOutstandingBasicAndDiluted>
  <xfor:NonCashLeaseExpense contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_5" unitRef="iso4217_USD">119000</xfor:NonCashLeaseExpense>
  <xfor:ConversionOfConvertiblePreferredStockToCommonStockValue contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_31" unitRef="iso4217_USD">64675000</xfor:ConversionOfConvertiblePreferredStockToCommonStockValue>
  <xfor:AccretionOnLongTermDebt contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_7F20F548-1D2D-4F2A-B5BF-C7817B5138A4_1_4" unitRef="iso4217_USD">-136000</xfor:AccretionOnLongTermDebt>
  <xfor:ConversionOfConvertiblePreferredStockWarrantsToCommonStockWarrants contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_33" unitRef="iso4217_USD">5235000</xfor:ConversionOfConvertiblePreferredStockWarrantsToCommonStockWarrants>
  <xfor:NonCashInterestExpense contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_6" unitRef="iso4217_USD">153000</xfor:NonCashInterestExpense>
  <xfor:ChangeInFairValueOfConvertiblePreferredStockWarrantLiability contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="-3" id="id_13073811_0494D198-BC4A-4EFB-967E-572E92F85446_1_7" unitRef="iso4217_USD">288000</xfor:ChangeInFairValueOfConvertiblePreferredStockWarrantLiability>
  <xfor:NumberOfDirectorsEntitledToBeElected contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" decimals="INF" id="id_13073811_1AB6290E-7443-4606-BB16-B76C5E212DFB_1_1" unitRef="Directors">1</xfor:NumberOfDirectorsEntitledToBeElected>
  <xfor:AccruedExpensesTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_F219F3F0-ED5A-471A-9C35-7B5E9210F0C0_1_0">&lt;div&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="break-inside: avoid"&gt;
 &lt;td valign="top" width="4%" align="left"&gt;&lt;b&gt;6.&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-TOP: 0pt" align="left"&gt;&lt;b&gt;Accrued Expenses&lt;/b&gt;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Accrued expenses consisted of the following:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="72%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="8%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="8%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;
 &lt;b&gt;&amp;#xA0;&amp;#xA0;&amp;#xA0;March&amp;#xA0;31,&amp;#xA0;&amp;#xA0;&amp;#xA0;&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;2019&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"&gt;&lt;b&gt;December&amp;#xA0;31,&lt;/b&gt;&lt;br /&gt;
 &lt;b&gt;2018&lt;/b&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Accrued employee compensation and benefits&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;
 &amp;#xA0;&amp;#xA0;&amp;#xA0;&amp;#xA0;1,239&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;924&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Accrued external research and development expenses&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;819&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;754&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Accrued professional fees&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,850&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;1,324&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Deferred rent, current portion&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap" align="right"&gt;
 &amp;#x2014;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;93&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="top"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Other&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;271&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;156&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; break-inside: avoid"&gt;
 &lt;td valign="top"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;4,179&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;$&lt;/td&gt;
 &lt;td valign="bottom" align="right"&gt;3,251&lt;/td&gt;
 &lt;td valign="bottom" nowrap="nowrap"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 1px"&gt;
 &lt;td valign="bottom"&gt;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/td&gt;
 &lt;td&gt;&amp;#xA0;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 18pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;/div&gt;</xfor:AccruedExpensesTextBlock>
  <xfor:ConcentrationOfCreditRiskPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_92D5CB39-C9B0-4E4C-AE50-146E019DC4F9_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Concentrations of Credit Risk and Significant
 Suppliers&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Financial instruments that potentially subject the Company to
 concentrations of credit risk consist principally of cash and cash
 equivalents and research and development incentive receivables. The
 Company generally maintains cash balances in various operating
 accounts at financial institutions that management believes to be
 of high credit quality, in amounts that may exceed federally
 insured limits. The Company has not experienced any losses related
 to its cash and cash equivalents.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 The Company is dependent on third-party manufacturers to supply
 products for research and development activities in its programs.
 The Company relies and expects to continue to rely on a small
 number of manufacturers to supply it with its requirements for the
 active pharmaceutical ingredients and formulated drugs related to
 these programs. These programs could be adversely affected by a
 significant interruption in these manufacturing services or in the
 supply of active pharmaceutical ingredients and formulated
 drugs.&lt;/p&gt;
 &lt;/div&gt;</xfor:ConcentrationOfCreditRiskPolicyTextBlock>
  <xfor:IntangibleAssetsPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_1B68ACD6-439B-4276-BCCD-E650C610E415_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt"&gt;
 &lt;b&gt;&lt;i&gt;Intangible Assets&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company acquired certain &lt;font style="WHITE-SPACE: nowrap"&gt;in-process&lt;/font&gt; research and development
 assets (&amp;#x201C;IPR&amp;amp;D&amp;#x201D;), which are classified as
 indefinite-lived intangible assets. Acquired IPR&amp;amp;D represents
 the fair value assigned to research and development assets that the
 Company acquires and have not been completed at the acquisition
 date. The fair value of IPR&amp;amp;D acquired in a business
 combination is capitalized on the Company&amp;#x2019;s consolidated
 balance sheets at the acquisition-date fair value and is determined
 by estimating the costs to develop the technology into commercially
 viable products, estimating the resulting revenue from the
 projects, and discounting the projected net cash flows to present
 value. IPR&amp;amp;D is not amortized, but rather is reviewed for
 impairment on an annual basis or more frequently if indicators of
 impairment are present, until the project is completed or
 abandoned. If the Company determines that IPR&amp;amp;D becomes
 impaired or is abandoned, the carrying value is written down to its
 fair value with the related impairment charge recognized in the
 Company&amp;#x2019;s consolidated statement of operations in the period
 in which the impairment occurs. Upon successful completion of each
 project and launch of the product, the Company will make a separate
 determination of the estimated useful life of the IPR&amp;amp;D
 intangible asset and the related amortization will be recorded as
 an expense prospectively over its estimated useful life.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 The projected discounted cash flow models used to estimate the
 Company&amp;#x2019;s IPR&amp;amp;D reflect significant assumptions regarding
 the estimates a market participant would make in order to evaluate
 a drug development asset, including the following:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;Probability of successfully completing clinical trials
 and obtaining regulatory approval;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;Market size, market growth projections, and market
 share;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;Estimates regarding the timing of and the expected
 costs to advance the Company&amp;#x2019;s clinical programs to
 commercialization;&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;Estimates of future cash flows from potential product
 sales; and&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0"&gt;
 &lt;tr style="PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td width="5%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" width="2%" align="left"&gt;&amp;#x2022;&lt;/td&gt;
 &lt;td valign="top" width="1%"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="top" align="left"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"&gt;A discount rate.&lt;/p&gt;
 &lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt"&gt;
 Additionally, to the extent the Company acquire other
 indefinite-lived intangible assets through its business
 combinations, these assets are reviewed for impairment on an annual
 basis or more frequently if indicators of impairment are present.
 If the Company determines that the asset becomes impaired, the
 carrying value is written down to its fair value with the related
 impairment charge recognized in its consolidated statements of
 operations in the period in which the impairment occurs.&lt;/p&gt;
 &lt;/div&gt;</xfor:IntangibleAssetsPolicyTextBlock>
  <xfor:PreferredStockWarrantLiabilityPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_5F64028B-FC5E-4222-84EA-5847419F3F91_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;Preferred Stock Warrant Liability&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Prior to the Merger with Arsanis, the Company classified warrants
 for the purchase of shares of its convertible preferred stock (see
 Note&amp;#xA0;10) as a liability on its consolidated balance sheets as
 these warrants are freestanding financial instruments that may have
 required the Company to transfer assets upon exercise. The warrant
 liability, which consisted of warrants for the purchase of
 Series&amp;#xA0;A and Series&amp;#xA0;B convertible preferred stock, was
 initially recorded at fair value upon the date of issuance of each
 warrant and is subsequently remeasured to fair value at each
 reporting date. Changes in the fair value of the warrant liability
 are recognized as a component of other income (expense), net in the
 consolidated statement of operations and comprehensive loss.
 Concurrent with the closing of the Merger, all X4 preferred stock
 was converted to Arsanis common stock and the X4 preferred stock
 warrants converted to warrants for the purchase of Arsanis common
 stock. The Company assessed the features of the warrants and
 determined that they qualify for classification as permanent
 equity. Accordingly, the Company remeasured the warrants to fair
 value upon the closing of the Merger and reclassified the resulting
 warrant liability to additional&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;paid-in&lt;/font&gt;&amp;#xA0;capital.
 (see Note&amp;#xA0;10).&lt;/p&gt;
 &lt;/div&gt;</xfor:PreferredStockWarrantLiabilityPolicyTextBlock>
  <xfor:PropertyPlantAndEquipmentUsefulLivesTableTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_3AF543F4-CEEE-4D0A-9BFD-A9271F90D462_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Property and Equipment&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Property and equipment are stated at cost less accumulated
 depreciation and amortization. Depreciation and amortization
 expense is recognized using the straight-line method over the
 estimated useful life of each asset, as follows:&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt"&gt;
 &amp;#xA0;&lt;/p&gt;
 &lt;table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="68%" align="center" border="0"&gt;
 &lt;tr&gt;
 &lt;td width="62%"&gt;&lt;/td&gt;
 &lt;td valign="bottom" width="4%"&gt;&lt;/td&gt;
 &lt;td&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" align="center"&gt;&lt;b&gt;Estimated&amp;#xA0;Useful&amp;#xA0;Life&lt;/b&gt;&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Office furniture&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;3 years&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Computer equipment&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;3 years&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Software&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;3 years&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid"&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Laboratory equipment&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;3 to 10 years&lt;/td&gt;
 &lt;/tr&gt;
 &lt;tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF"&gt;
 &lt;td valign="bottom"&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em"&gt;
 Leasehold improvements&lt;/p&gt;
 &lt;/td&gt;
 &lt;td valign="bottom"&gt;&amp;#xA0;&amp;#xA0;&lt;/td&gt;
 &lt;td valign="bottom" align="center"&gt;
 Shorter&amp;#xA0;of&amp;#xA0;lease&amp;#xA0;term&amp;#xA0;or&amp;#xA0;10&amp;#xA0;years&lt;/td&gt;
 &lt;/tr&gt;
 &lt;/table&gt;
 &lt;/div&gt;</xfor:PropertyPlantAndEquipmentUsefulLivesTableTextBlock>
  <xfor:ResearchAndDevelopmentPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_660E60AC-CF01-4F81-AB8A-4BFF950D5ED5_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Research and Development Programs&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 Proceeds under the research and development incentive program from
 the Austrian government are recognized as other income in an amount
 equal to the qualifying expenses incurred in each period multiplied
 by the applicable reimbursement percentage. Incentive income
 recognized upon incurring qualifying expenses in advance of receipt
 of proceeds from research and development incentives is recorded in
 the consolidated balance sheet as research and development
 incentive receivables.&lt;/p&gt;
 &lt;/div&gt;</xfor:ResearchAndDevelopmentPolicyTextBlock>
  <xfor:DeferredRentPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_6D2ED321-5787-47C9-B6AA-B21828DC27CD_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt"&gt;
 &lt;b&gt;&lt;i&gt;Deferred Rent&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt"&gt;
 The Company&amp;#x2019;s lease agreements include payment escalations
 and lease incentives (including a leasehold improvement tenant
 allowance). For periods prior to January&amp;#xA0;1, 2019, these
 payments were accrued or deferred as appropriate such that rent
 expense was recognized on a straight-line basis over the respective
 lease terms. Effective January&amp;#xA0;1, 2019, upon the adoption of
 ASC 842,deferred rent was reclassified as a reduction to the
 applicable &lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt; asset as further
 described in Note 8.&lt;/p&gt;
 &lt;/div&gt;</xfor:DeferredRentPolicyTextBlock>
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  <xfor:RightOfUseAssetAndLeaseLiabilityPolicyTextBlock contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0" id="id_13073811_BDF47B17-BE48-46C8-8AD0-F4E85957E143_1_0">&lt;div&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 &lt;b&gt;&lt;i&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;Right-of-Use&lt;/font&gt;&lt;/font&gt;&amp;#xA0;Assets
 and Leases&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Effective January&amp;#xA0;1, 2019, the Company adopted Accounting
 Standards Codification (&amp;#x201C;ASC&amp;#x201D;), Topic
 842,&amp;#xA0;&lt;i&gt;Leases&amp;#xA0;&lt;/i&gt;(&amp;#x201C;ASC
 842&amp;#x201D;), using the modified retrospective approach through a
 cumulative-effect adjustment and utilizing the effective date as
 its date of initial application, with prior periods unchanged and
 presented in accordance with the guidance in Topic
 840,&amp;#xA0;&lt;i&gt;Leases&lt;/i&gt;&amp;#xA0;(&amp;#x201C;ASC
 840&amp;#x201D;).&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 At the inception of an arrangement, the Company determines whether
 the arrangement is or contains a lease based on the unique facts
 and circumstances present. Leases with
 a&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-cancellable&lt;/font&gt;&amp;#xA0;term
 greater than one year are recognized on the balance sheet
 as&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt;&amp;#xA0;assets,
 lease liabilities and long-term lease liabilities. The Company has
 elected not to recognize on the balance sheet leases with terms of
 one year or less. Options to renew a lease are not included in the
 Company&amp;#x2019;s initial lease term assessment unless there is
 reasonable certainty that the Company will renew.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 Operating lease liabilities and their
 corresponding&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt;&amp;#xA0;assets
 are recorded based on the present value of lease payments over the
 expected remaining lease term. However, certain adjustments to
 the&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;&lt;font style="WHITE-SPACE: nowrap"&gt;right-of-use&lt;/font&gt;&lt;/font&gt;&amp;#xA0;operating
 asset may be required for items, such as incentives received. The
 interest rate implicit in lease contracts is typically not readily
 determinable. As a result, the Company utilizes its incremental
 borrowing rates, which are the rates it incurs to borrow on a
 collateralized basis over a similar term an amount equal to the
 lease payments in a similar economic environment.&lt;/p&gt;
 &lt;p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &amp;quot;Times New Roman&amp;quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal"&gt;
 In accordance with the guidance in ASC 842, components of a lease
 are split into lease components and&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-lease&lt;/font&gt;&amp;#xA0;components.
 A policy election is available pursuant to which an entity may
 elect to not separate lease and&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-lease&lt;/font&gt;components. Rather, each
 lease component and the related&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-lease&lt;/font&gt;&amp;#xA0;components
 would be accounted for together as a single component. For new and
 amended leases beginning in 2019 and after, the Company has elected
 to account for the lease and&amp;#xA0;&lt;font style="WHITE-SPACE: nowrap"&gt;non-lease&lt;/font&gt;&amp;#xA0;components
 as a combined lease component for its office and laboratory
 building leases.&lt;/p&gt;
 &lt;/div&gt;</xfor:RightOfUseAssetAndLeaseLiabilityPolicyTextBlock>
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  <us-gaap:DebtInstrumentDescriptionOfVariableRateBasis contextRef="eol_PE837744--1910-Q0004_STD_90_20190331_0_3066061x3566848" id="id_13073811_C7D16AE8-5583-4D8D-9279-281A030F52F7_1003_3">Borrowings under the SVB Loan Agreement bore interest at a variable rate equal  to 5.5% plus the greater of (i) 3.5% or (ii) The Wall Street Journal prime rate.</us-gaap:DebtInstrumentDescriptionOfVariableRateBasis>
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<DOCUMENT>
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<DESCRIPTION>XBRL TAXONOMY EXTENSION SCHEMA
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  <element name="ContractManufacturingOrganizationsAgreementMember" id="xfor_ContractManufacturingOrganizationsAgreementMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ConversionOfConvertiblePreferredStockToCommonStockValue" id="xfor_ConversionOfConvertiblePreferredStockToCommonStockValue" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ConversionOfConvertiblePreferredStockWarrantsToCommonStockWarrants" id="xfor_ConversionOfConvertiblePreferredStockWarrantsToCommonStockWarrants" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ConversionOfRedeemableCommonStockToCommonStockShares" id="xfor_ConversionOfRedeemableCommonStockToCommonStockShares" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ConversionOfRedeemableCommonStockToCommonStockValue" id="xfor_ConversionOfRedeemableCommonStockToCommonStockValue" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ConvertiblePreferredSharesMember" id="xfor_ConvertiblePreferredSharesMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CurrentOfficeSpaceUnderLeaseAgreement" id="xfor_CurrentOfficeSpaceUnderLeaseAgreement" type="num:areaItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DebtCovenantMinimumLiquidityPercentageOfCashAndCashEquivalents" id="xfor_DebtCovenantMinimumLiquidityPercentageOfCashAndCashEquivalents" type="num:percentItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DebtCovenantMinimumLiquidityPercentageOfOutstandingBorrowings" id="xfor_DebtCovenantMinimumLiquidityPercentageOfOutstandingBorrowings" type="num:percentItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DebtInstrumentAccruedInterest" id="xfor_DebtInstrumentAccruedInterest" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DebtInstrumentCarryingValue" id="xfor_DebtInstrumentCarryingValue" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DebtInstrumentPrepaymentPremium" id="xfor_DebtInstrumentPrepaymentPremium" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DebtInstrumentPrePaymentPremiumPercentage" id="xfor_DebtInstrumentPrePaymentPremiumPercentage" type="num:percentItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DebtMaturitiesLineItems" id="xfor_DebtMaturitiesLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredRentPolicyTextBlock" id="xfor_DeferredRentPolicyTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DocumentAndEntityInformationAbstract" id="xfor_DocumentAndEntityInformationAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="EmployeeStockPurchasePlansMember" id="xfor_EmployeeStockPurchasePlansMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisLineItems" id="xfor_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTable" id="xfor_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="FairValueAssetsMeasuredOnRecurringAndNonrecurringBasisLineItems" id="xfor_FairValueAssetsMeasuredOnRecurringAndNonrecurringBasisLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FairValueMeasurementWithUnobservableInputsConversionOfConvertiblePreferredStockWarrantsIntoCommonStockWarrantsInConnectionWithMerger" id="xfor_FairValueMeasurementWithUnobservableInputsConversionOfConvertiblePreferredStockWarrantsIntoCommonStockWarrantsInConnectionWithMerger" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FairValueOfCommonStockPerShare" id="xfor_FairValueOfCommonStockPerShare" type="num:perShareItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FairValueOfNetAssetsAcquiredInReverseMerger" id="xfor_FairValueOfNetAssetsAcquiredInReverseMerger" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FairValueOfReplacementEquityAwards" id="xfor_FairValueOfReplacementEquityAwards" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FairValueTransfersBetweenLevel1Level2OrLevel3Amount" id="xfor_FairValueTransfersBetweenLevel1Level2OrLevel3Amount" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FebruaryTwoThousandAndSeventeenGrantAgreementMember" id="xfor_FebruaryTwoThousandAndSeventeenGrantAgreementMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FfgLoanAgreementMember" id="xfor_FfgLoanAgreementMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FirstTrancheMember" id="xfor_FirstTrancheMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FundingCommitmentPeriod" id="xfor_FundingCommitmentPeriod" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="GenzymeAgreementMember" id="xfor_GenzymeAgreementMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="GeorgetownAgreementMember" id="xfor_GeorgetownAgreementMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="GrantAgreementMember" id="xfor_GrantAgreementMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="GrantAndIncentiveReceivables" id="xfor_GrantAndIncentiveReceivables" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="GrantsAgreementMaximumAwardAmount" id="xfor_GrantsAgreementMaximumAwardAmount" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="HerculesLoanAgreementMember" id="xfor_HerculesLoanAgreementMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IncreaseDecreaseInOperatingLeaseLiabilities" id="xfor_IncreaseDecreaseInOperatingLeaseLiabilities" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IndemnificationAgreementsMember" id="xfor_IndemnificationAgreementsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IntangibleAssetsPolicyTextBlock" id="xfor_IntangibleAssetsPolicyTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IssuanceOnAugustFourteenTwoThousandFifteenMember" id="xfor_IssuanceOnAugustFourteenTwoThousandFifteenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IssuanceOnAugustTwentyOneTwoThousandFifteenMember" id="xfor_IssuanceOnAugustTwentyOneTwoThousandFifteenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IssuanceOnDecemberElevenTwoThousandEighteenMember" id="xfor_IssuanceOnDecemberElevenTwoThousandEighteenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IssuanceOnDecemberFourTwoThousandSeventeenMember" id="xfor_IssuanceOnDecemberFourTwoThousandSeventeenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IssuanceOnDecemberTwentyEightTwoThousandSeventeenMember" id="xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IssuanceOnDecemberTwentyEightTwoThousandSeventeenOneMember" id="xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenOneMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IssuanceOnNovemberOneTwoThousandSeventeenMember" id="xfor_IssuanceOnNovemberOneTwoThousandSeventeenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IssuanceOnNovemberSeventeenTwoThousandSeventeenMember" id="xfor_IssuanceOnNovemberSeventeenTwoThousandSeventeenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IssuanceOnOctoberNineteenTwoThousandEighteenMember" id="xfor_IssuanceOnOctoberNineteenTwoThousandEighteenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IssuanceOnOctoberTwentyFiveTwoThousandSixteenMember" id="xfor_IssuanceOnOctoberTwentyFiveTwoThousandSixteenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IssuanceOnSeptemberTwelveTwoThousandEighteenMember" id="xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IssuanceOnSeptemberTwelveTwoThousandEighteenOneMember" id="xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenOneMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="JanssenLicenseAndOptionAgreementMember" id="xfor_JanssenLicenseAndOptionAgreementMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="JanssenPharmaceuticalsIncorporationMember" id="xfor_JanssenPharmaceuticalsIncorporationMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="LabEquipmentMember" id="xfor_LabEquipmentMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="LeaseAgreementExtensionDescription" id="xfor_LeaseAgreementExtensionDescription" type="xbrli:stringItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="LeaseAgreementPeriodOfWrittenNoticeForCancellable" id="xfor_LeaseAgreementPeriodOfWrittenNoticeForCancellable" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="LicenseAgreementTerminationDescription" id="xfor_LicenseAgreementTerminationDescription" type="xbrli:stringItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="LongTermDebtByMaturityTable" id="xfor_LongTermDebtByMaturityTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="LongTermDebtNonCurrentIncludingAccretion" id="xfor_LongTermDebtNonCurrentIncludingAccretion" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MaximumFundingCommitmentAmount" id="xfor_MaximumFundingCommitmentAmount" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MilestonePaymentObligation" id="xfor_MilestonePaymentObligation" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MilestonePayments" id="xfor_MilestonePayments" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MilestonePaymentsPaid" id="xfor_MilestonePaymentsPaid" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NetProceedsFromIssuanceOfCommonStockAndWarrants" id="xfor_NetProceedsFromIssuanceOfCommonStockAndWarrants" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NonCashInterestExpense" id="xfor_NonCashInterestExpense" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NonCashLeaseExpense" id="xfor_NonCashLeaseExpense" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfCommonStockSharesIssuableUponConversion" id="xfor_NumberOfCommonStockSharesIssuableUponConversion" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfDirectorsEntitledToBeElected" id="xfor_NumberOfDirectorsEntitledToBeElected" type="xbrli:integerItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfYearsAcceleratedPaymentTerm" id="xfor_NumberOfYearsAcceleratedPaymentTerm" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OfficeLeasesMember" id="xfor_OfficeLeasesMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OneTimeUpfrontPayment" id="xfor_OneTimeUpfrontPayment" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OperatingLeaseExpiration" id="xfor_OperatingLeaseExpiration" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OptionFee" id="xfor_OptionFee" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PaymentOnObligationUnderLicenseAgreement" id="xfor_PaymentOnObligationUnderLicenseAgreement" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PaymentsOfIssuanceCostsOfRedeemableConvertiblePreferredStock" id="xfor_PaymentsOfIssuanceCostsOfRedeemableConvertiblePreferredStock" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PercentageOfMinimumCashBalanceEqualToOutstandingPrincipalAmountOfLoans" id="xfor_PercentageOfMinimumCashBalanceEqualToOutstandingPrincipalAmountOfLoans" type="num:percentItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PreferredStockFairValuePerShare" id="xfor_PreferredStockFairValuePerShare" type="num:perShareItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PreferredStockIssuanceCosts" id="xfor_PreferredStockIssuanceCosts" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PreferredStockWarrantLiability" id="xfor_PreferredStockWarrantLiability" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PreferredStockWarrantLiabilityMember" id="xfor_PreferredStockWarrantLiabilityMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PreferredStockWarrantLiabilityPolicyTextBlock" id="xfor_PreferredStockWarrantLiabilityPolicyTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PreFundedWarrantMember" id="xfor_PreFundedWarrantMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ProceedsFromIssuanceOfCommonStockBeforeUnderwritingDiscountsCommissionsAndOtherExpenses" id="xfor_ProceedsFromIssuanceOfCommonStockBeforeUnderwritingDiscountsCommissionsAndOtherExpenses" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PropertyPlantAndEquipmentUsefulLivesAbstract" id="xfor_PropertyPlantAndEquipmentUsefulLivesAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PropertyPlantAndEquipmentUsefulLivesTableTextBlock" id="xfor_PropertyPlantAndEquipmentUsefulLivesTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="QualifyingExpensesUnderLetterAgreement" id="xfor_QualifyingExpensesUnderLetterAgreement" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ReacquisitionPriceOfBorrowing" id="xfor_ReacquisitionPriceOfBorrowing" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RedeemableCommonStockMember" id="xfor_RedeemableCommonStockMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ReimbursementRateForResearchAndDevelopment" id="xfor_ReimbursementRateForResearchAndDevelopment" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RepaymentOfDebtFinalPayment" id="xfor_RepaymentOfDebtFinalPayment" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ResearchAndDevelopmentIncentiveProgramMember" id="xfor_ResearchAndDevelopmentIncentiveProgramMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ResearchAndDevelopmentIncentiveReceivable" id="xfor_ResearchAndDevelopmentIncentiveReceivable" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ResearchAndDevelopmentPolicyTextBlock" id="xfor_ResearchAndDevelopmentPolicyTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RightOfUseAssetAndLeaseLiabilityPolicyTextBlock" id="xfor_RightOfUseAssetAndLeaseLiabilityPolicyTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfAccountingPoliciesLineItems" id="xfor_ScheduleOfAccountingPoliciesLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfAccountingPoliciesTable" id="xfor_ScheduleOfAccountingPoliciesTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="ScheduleOfLongTermDebtLineItems" id="xfor_ScheduleOfLongTermDebtLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfLongTermDebtTable" id="xfor_ScheduleOfLongTermDebtTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="SecondTrancheaMember" id="xfor_SecondTrancheaMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SecondTranchebMember" id="xfor_SecondTranchebMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SeriesAConvertiblePreferredStockMember" id="xfor_SeriesAConvertiblePreferredStockMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SeriesAPreferredStockWarrantsMember" id="xfor_SeriesAPreferredStockWarrantsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SeriesBConvertiblePreferredStockMember" id="xfor_SeriesBConvertiblePreferredStockMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SeriesBPreferredStockWarrantsMember" id="xfor_SeriesBPreferredStockWarrantsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SeriesBRedeemableConvertiblePreferredStockMember" id="xfor_SeriesBRedeemableConvertiblePreferredStockMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SeriesSeedConvertiblePreferredStockMember" id="xfor_SeriesSeedConvertiblePreferredStockMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SeriesSeedPreferredStockMember" id="xfor_SeriesSeedPreferredStockMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
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</XBRL>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-101.CAL
<SEQUENCE>13
<FILENAME>xfor-20190331_cal.xml
<DESCRIPTION>XBRL TAXONOMY EXTENSION CALCULATION LINKBASE
<TEXT>
<XBRL>
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<!-- Version: 6.23.6 -->
<!-- Round: 9 -->
<!-- Creation date: 2019-05-15T20:37:51Z -->
<!-- Copyright (c) 2019 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
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<DOCUMENT>
<TYPE>EX-101.DEF
<SEQUENCE>14
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<DESCRIPTION>XBRL TAXONOMY EXTENSION DEFINITION LINKBASE
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_AdditionalTermLoanOneMember_lbl" xml:lang="en-US" id="id_13073811_3566861_2_1">Additional Term Loan One [Member]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain_lbl" xml:lang="en-US" id="id_13073811_3064119_2_1">Antidilutive Securities, Name [Domain]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ArsanisAndMergerSubMember_lbl" xml:lang="en-US" id="id_13073811_3566252_2_1">Arsanis And Merger Sub [Member]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ArsanisMember_lbl" xml:lang="en-US" id="id_13073811_3566373_1_1">Arsanis [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ArsanisMember_lbl" xml:lang="en-US" id="id_13073811_3566373_2_1">Arsanis [Member]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ArsanisSecurityHoldersMember_lbl" xml:lang="en-US" id="id_13073811_3566370_2_1">Arsanis Security Holders [Member]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CashAndCashEquivalentsAxis_lbl" xml:lang="en-US" id="id_13073811_3065067_2_1">Cash and Cash Equivalents [Axis]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsAxis" xlink:to="us-gaap_CashAndCashEquivalentsAxis_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CashAndCashEquivalentsFairValueDisclosure_lbl" xml:lang="en-US" id="id_13073811_3065488_2_1">Cash equivalents</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ClassOfWarrantOrRightLineItems_lbl" xml:lang="en-US" id="id_13073811_3065550_2_1">Class of Warrant or Right [Line Items]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_lbl" xml:lang="en-US" id="id_13073811_3065368_1_1">Class of Warrant or Right, Number of Securities Called by Each Warrant or Right</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_lbl" xml:lang="en-US" id="id_13073811_3065368_2_1">Number of warrant</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_lbl" xml:lang="en-US" id="id_13073811_3065368_12_1">Number of warrants for purchase of convertible preferred shares</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xml:lang="en-US" id="id_13073811_3065811_1_1">Class of Warrant or Right, Number of Securities Called by Warrants or Rights</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/positiveLabel" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xml:lang="en-US" id="id_13073811_3065811_32_1">Warrant issued to purchase stock</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xml:lang="en-US" id="id_13073811_3065811_2_1">Business combination warrants to purchase of common stock</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xml:lang="en-US" id="id_13073811_3065811_12_1">Class of warrant or right, warrants to purchase of common stock</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:to="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfWarrantOrRightOutstanding" xlink:label="us-gaap_ClassOfWarrantOrRightOutstanding"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ClassOfWarrantOrRightOutstanding_lbl" xml:lang="en-US" id="id_13073811_3065551_1_1">Class of Warrant or Right, Outstanding</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ClassOfWarrantOrRightOutstanding_lbl" xml:lang="en-US" id="id_13073811_3065551_2_1">Number of Shares of common Stock Issuable</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfWarrantOrRightOutstanding" xlink:to="us-gaap_ClassOfWarrantOrRightOutstanding_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ClassOfWarrantOrRightsExpirationDate" xlink:label="xfor_ClassOfWarrantOrRightsExpirationDate"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ClassOfWarrantOrRightsExpirationDate_lbl" xml:lang="en-US" id="id_13073811_3213240_3_1">Class of warrant or rights expiration date.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ClassOfWarrantOrRightsExpirationDate_lbl" xml:lang="en-US" id="id_13073811_3213240_1_1">Class Of Warrant Or Rights Expiration Date</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ClassOfWarrantOrRightsExpirationDate_lbl" xml:lang="en-US" id="id_13073811_3213240_2_1">Expiration Date</label>
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    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ClassOfWarrantOrRightsIssuanceDate" xlink:label="xfor_ClassOfWarrantOrRightsIssuanceDate"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ClassOfWarrantOrRightsIssuanceDate_lbl" xml:lang="en-US" id="id_13073811_3212522_3_1">Class Of Warrant Or Rights Issuance Date</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ClassOfWarrantOrRightsIssuanceDate_lbl" xml:lang="en-US" id="id_13073811_3212522_1_1">Class Of Warrant Or Rights Issuance Date</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ClassOfWarrantOrRightsIssuanceDate_lbl" xml:lang="en-US" id="id_13073811_3212522_2_1">Issuance Date</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ClassOfWarrantOrRightsIssuanceDate" xlink:to="xfor_ClassOfWarrantOrRightsIssuanceDate_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ClassOfWarrantOrRightsWarrantsExpirationPeriod" xlink:label="xfor_ClassOfWarrantOrRightsWarrantsExpirationPeriod"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ClassOfWarrantOrRightsWarrantsExpirationPeriod_lbl" xml:lang="en-US" id="id_13073811_3234175_3_1">Class Of Warrant Or Rights Warrants Expiration Period</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ClassOfWarrantOrRightsWarrantsExpirationPeriod_lbl" xml:lang="en-US" id="id_13073811_3234175_1_1">Class Of Warrant Or Rights Warrants Expiration Period</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ClassOfWarrantOrRightsWarrantsExpirationPeriod_lbl" xml:lang="en-US" id="id_13073811_3234175_2_1">Class of warrant expiration period</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ClassOfWarrantOrRightsWarrantsExpirationPeriod" xlink:to="xfor_ClassOfWarrantOrRightsWarrantsExpirationPeriod_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfWarrantOrRightTable" xlink:label="us-gaap_ClassOfWarrantOrRightTable"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ClassOfWarrantOrRightTable_lbl" xml:lang="en-US" id="id_13073811_3065553_1_1">Class of Warrant or Right [Table]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ClassOfWarrantOrRightTable_lbl" xml:lang="en-US" id="id_13073811_3065553_2_1">Class of Warrant or Right [Table]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfWarrantOrRightTable" xlink:to="us-gaap_ClassOfWarrantOrRightTable_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ClassOfWarrantOrRightWarrantsExpirationPeriod" xlink:label="xfor_ClassOfWarrantOrRightWarrantsExpirationPeriod"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ClassOfWarrantOrRightWarrantsExpirationPeriod_lbl" xml:lang="en-US" id="id_13073811_3228471_3_1">Class Of Warrant Or Right Warrants Expiration Period</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ClassOfWarrantOrRightWarrantsExpirationPeriod_lbl" xml:lang="en-US" id="id_13073811_3228471_1_1">Class Of Warrant Or Right Warrants Expiration Period</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ClassOfWarrantOrRightWarrantsExpirationPeriod_lbl" xml:lang="en-US" id="id_13073811_3228471_2_1">Class of warrants or rights expiration period</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ClassOfWarrantOrRightWarrantsExpirationPeriod" xlink:to="xfor_ClassOfWarrantOrRightWarrantsExpirationPeriod_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_CollaborationLicenseAndFundingArrangementsLineItems" xlink:label="xfor_CollaborationLicenseAndFundingArrangementsLineItems"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_CollaborationLicenseAndFundingArrangementsLineItems_lbl" xml:lang="en-US" id="id_13073811_3393256_3_1">Collaboration, license and funding arrangements.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_CollaborationLicenseAndFundingArrangementsLineItems_lbl" xml:lang="en-US" id="id_13073811_3393256_1_1">Collaboration License And Funding Arrangements [Line Items]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_CollaborationLicenseAndFundingArrangementsLineItems_lbl" xml:lang="en-US" id="id_13073811_3393256_2_1">Collaboration License And Funding Arrangements [Line Items]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_CollaborationLicenseAndFundingArrangementsLineItems" xlink:to="xfor_CollaborationLicenseAndFundingArrangementsLineItems_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_CollaborationLicenseAndFundingArrangementsTable" xlink:label="xfor_CollaborationLicenseAndFundingArrangementsTable"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_CollaborationLicenseAndFundingArrangementsTable_lbl" xml:lang="en-US" id="id_13073811_3393257_3_1">Collaboration, license and funding arrangements.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_CollaborationLicenseAndFundingArrangementsTable_lbl" xml:lang="en-US" id="id_13073811_3393257_1_1">Collaboration License And Funding Arrangements [Table]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_CollaborationLicenseAndFundingArrangementsTable_lbl" xml:lang="en-US" id="id_13073811_3393257_2_1">Collaboration License And Funding Arrangements [Table]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_CollaborationLicenseAndFundingArrangementsTable" xlink:to="xfor_CollaborationLicenseAndFundingArrangementsTable_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CollaborativeArrangementDisclosureTextBlock" xlink:label="us-gaap_CollaborativeArrangementDisclosureTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CollaborativeArrangementDisclosureTextBlock_lbl" xml:lang="en-US" id="id_13073811_3065179_1_1">Collaborative Arrangement Disclosure [Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CollaborativeArrangementDisclosureTextBlock_lbl" xml:lang="en-US" id="id_13073811_3065179_2_1">License, Collaboration, and Funding Agreements</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CollaborativeArrangementDisclosureTextBlock" xlink:to="us-gaap_CollaborativeArrangementDisclosureTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CollaborativeArrangementRightsAndObligations" xlink:label="us-gaap_CollaborativeArrangementRightsAndObligations"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CollaborativeArrangementRightsAndObligations_lbl" xml:lang="en-US" id="id_13073811_3065182_1_1">Collaborative Arrangement, Rights and Obligations</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CollaborativeArrangementRightsAndObligations_lbl" xml:lang="en-US" id="id_13073811_3065182_2_1">License and options agreement description</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CollaborativeArrangementRightsAndObligations" xlink:to="us-gaap_CollaborativeArrangementRightsAndObligations_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CollateralizedCreditCardSecuritiesMember" xlink:label="us-gaap_CollateralizedCreditCardSecuritiesMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CollateralizedCreditCardSecuritiesMember_lbl" xml:lang="en-US" id="id_13073811_3065836_1_1">Collateralized Credit Card Securities [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CollateralizedCreditCardSecuritiesMember_lbl" xml:lang="en-US" id="id_13073811_3065836_2_1">Collateralized Credit Card Securities [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CollateralizedCreditCardSecuritiesMember" xlink:to="us-gaap_CollateralizedCreditCardSecuritiesMember_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="us-gaap_CommitmentsAndContingencies"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xml:lang="en-US" id="id_13073811_3065406_1_1">Commitments and Contingencies</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xml:lang="en-US" id="id_13073811_3065406_2_1">Commitments and contingencies (Note 9)</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract_lbl" xml:lang="en-US" id="id_13073811_3065589_1_1">Commitments and Contingencies Disclosure [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract_lbl" xml:lang="en-US" id="id_13073811_3065589_2_1">Commitments and Contingencies Disclosure [Abstract]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xml:lang="en-US" id="id_13073811_3065193_1_1">Commitments and Contingencies Disclosure [Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xml:lang="en-US" id="id_13073811_3065193_2_1">Commitment and Contingencies</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockMember" xlink:label="us-gaap_CommonStockMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockMember_lbl" xml:lang="en-US" id="id_13073811_3065602_1_1">Common Stock [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CommonStockMember_lbl" xml:lang="en-US" id="id_13073811_3065602_2_1">Common Stock [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockMember" xlink:to="us-gaap_CommonStockMember_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xml:lang="en-US" id="id_13073811_3065857_1_1">Common Stock, Par or Stated Value Per Share</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xml:lang="en-US" id="id_13073811_3065857_2_1">Common stock, par value</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockParOrStatedValuePerShare" xlink:to="us-gaap_CommonStockParOrStatedValuePerShare_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_CommonStockRepurchasePricePerShare" xlink:label="xfor_CommonStockRepurchasePricePerShare"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_CommonStockRepurchasePricePerShare_lbl" xml:lang="en-US" id="id_13073811_3357128_1_1">Common Stock Repurchase Price Per Share</label>
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    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_CommonStockRepurchasePricePerShare" xlink:to="xfor_CommonStockRepurchasePricePerShare_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_CommonStockReservedForIssuanceDescription" xlink:label="xfor_CommonStockReservedForIssuanceDescription"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_CommonStockReservedForIssuanceDescription_lbl" xml:lang="en-US" id="id_13073811_3210324_3_1">Common Stock Reserved For Issuance Description</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_CommonStockReservedForIssuanceDescription_lbl" xml:lang="en-US" id="id_13073811_3210324_1_1">Common Stock Reserved For Issuance Description</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_CommonStockReservedForIssuanceDescription_lbl" xml:lang="en-US" id="id_13073811_3210324_2_1">Common stock reserved for future issuance, description</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_CommonStockReservedForIssuanceDescription" xlink:to="xfor_CommonStockReservedForIssuanceDescription_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="us-gaap_CommonStockSharesAuthorized"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xml:lang="en-US" id="id_13073811_3065416_1_1">Common Stock, Shares Authorized</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xml:lang="en-US" id="id_13073811_3065416_2_1">Common stock, authorized shares</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xml:lang="en-US" id="id_13073811_3065416_12_1">Common stock, shares authorized</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesAuthorized" xlink:to="us-gaap_CommonStockSharesAuthorized_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockSharesIssued" xlink:label="us-gaap_CommonStockSharesIssued"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xml:lang="en-US" id="id_13073811_3065859_1_1">Common Stock, Shares, Issued</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xml:lang="en-US" id="id_13073811_3065859_2_1">Common stock, shares issued</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesIssued" xlink:to="us-gaap_CommonStockSharesIssued_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="us-gaap_CommonStockSharesOutstanding"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xml:lang="en-US" id="id_13073811_3065417_1_1">Common Stock, Shares, Outstanding</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xml:lang="en-US" id="id_13073811_3065417_2_1">Common stock, shares outstanding</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesOutstanding" xlink:to="us-gaap_CommonStockSharesOutstanding_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockValue" xlink:label="us-gaap_CommonStockValue"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockValue_lbl" xml:lang="en-US" id="id_13073811_3065862_1_1">Common Stock, Value, Issued</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CommonStockValue_lbl" xml:lang="en-US" id="id_13073811_3065862_2_1">Common stock</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockValue" xlink:to="us-gaap_CommonStockValue_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockVotingRights" xlink:label="us-gaap_CommonStockVotingRights"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockVotingRights_lbl" xml:lang="en-US" id="id_13073811_3065212_1_1">Common Stock, Voting Rights</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CommonStockVotingRights_lbl" xml:lang="en-US" id="id_13073811_3065212_2_1">Common stock, voting right</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockVotingRights" xlink:to="us-gaap_CommonStockVotingRights_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xml:lang="en-US" id="id_13073811_3065872_1_1">Comprehensive Income (Loss), Net of Tax, Attributable to Parent</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xml:lang="en-US" id="id_13073811_3065872_2_1">Net loss</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xml:lang="en-US" id="id_13073811_3065872_6_1">Total comprehensive loss</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ComprehensiveIncomeNetOfTax" xlink:to="us-gaap_ComprehensiveIncomeNetOfTax_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ComprehensiveIncomePolicyPolicyTextBlock" xlink:label="us-gaap_ComprehensiveIncomePolicyPolicyTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ComprehensiveIncomePolicyPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3065876_1_1">Comprehensive Income, Policy [Policy Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ComprehensiveIncomePolicyPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3065876_2_1">Comprehensive Loss</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ComprehensiveIncomePolicyPolicyTextBlock" xlink:to="us-gaap_ComprehensiveIncomePolicyPolicyTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ComputerEquipmentMember" xlink:label="us-gaap_ComputerEquipmentMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ComputerEquipmentMember_lbl" xml:lang="en-US" id="id_13073811_3065616_1_1">Computer Equipment [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ComputerEquipmentMember_lbl" xml:lang="en-US" id="id_13073811_3065616_2_1">Computer Equipment [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ComputerEquipmentMember" xlink:to="us-gaap_ComputerEquipmentMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ConcentrationOfCreditRiskPolicyTextBlock" xlink:label="xfor_ConcentrationOfCreditRiskPolicyTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ConcentrationOfCreditRiskPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3339888_3_1">Concentration Of Credit Risk Policy Text Block.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ConcentrationOfCreditRiskPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3339888_1_1">Concentration Of Credit Risk [Policy Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ConcentrationOfCreditRiskPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3339888_2_1">Concentrations of Credit Risk and Significant Suppliers</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ConcentrationOfCreditRiskPolicyTextBlock" xlink:to="xfor_ConcentrationOfCreditRiskPolicyTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ConsiderationToEquityShareholders" xlink:label="xfor_ConsiderationToEquityShareholders"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ConsiderationToEquityShareholders_lbl" xml:lang="en-US" id="id_13073811_3566709_3_1">Consideration to equity shareholders.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ConsiderationToEquityShareholders_lbl" xml:lang="en-US" id="id_13073811_3566709_1_1">Consideration To Equity Shareholders</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ConsiderationToEquityShareholders_lbl" xml:lang="en-US" id="id_13073811_3566709_2_1">Consideration paid to equity shareholders</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ConsiderationToEquityShareholders" xlink:to="xfor_ConsiderationToEquityShareholders_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConsolidationPolicyTextBlock" xlink:label="us-gaap_ConsolidationPolicyTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ConsolidationPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3066117_1_1">Consolidation, Policy [Policy Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ConsolidationPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3066117_2_1">Principles of Consolidation</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConsolidationPolicyTextBlock" xlink:to="us-gaap_ConsolidationPolicyTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ContingenciesAndCommitmentsLineItems" xlink:label="xfor_ContingenciesAndCommitmentsLineItems"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ContingenciesAndCommitmentsLineItems_lbl" xml:lang="en-US" id="id_13073811_3088677_3_1">Contingencies And Commitments [Line Items]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ContingenciesAndCommitmentsLineItems_lbl" xml:lang="en-US" id="id_13073811_3088677_1_1">Contingencies And Commitments [Line Items]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ContingenciesAndCommitmentsLineItems_lbl" xml:lang="en-US" id="id_13073811_3088677_2_1">Contingencies And Commitments [Line Items]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ContingenciesAndCommitmentsLineItems" xlink:to="xfor_ContingenciesAndCommitmentsLineItems_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ContingenciesAndCommitmentsTable" xlink:label="xfor_ContingenciesAndCommitmentsTable"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ContingenciesAndCommitmentsTable_lbl" xml:lang="en-US" id="id_13073811_3237938_3_1">Contingencies And Commitments [Table]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ContingenciesAndCommitmentsTable_lbl" xml:lang="en-US" id="id_13073811_3237938_1_1">Contingencies And Commitments [Table]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ContingenciesAndCommitmentsTable_lbl" xml:lang="en-US" id="id_13073811_3237938_2_1">Contingencies And Commitments [Table]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ContingenciesAndCommitmentsTable" xlink:to="xfor_ContingenciesAndCommitmentsTable_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ContractManufacturingOrganizationsAgreementMember" xlink:label="xfor_ContractManufacturingOrganizationsAgreementMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ContractManufacturingOrganizationsAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3566703_3_1">Contract Manufacturing Organizations Agreement [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ContractManufacturingOrganizationsAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3566703_1_1">Contract Manufacturing Organizations Agreement [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ContractManufacturingOrganizationsAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3566703_2_1">Contract Manufacturing Organizations Agreement [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ContractManufacturingOrganizationsAgreementMember" xlink:to="xfor_ContractManufacturingOrganizationsAgreementMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ConversionOfConvertiblePreferredStockToCommonStockValue" xlink:label="xfor_ConversionOfConvertiblePreferredStockToCommonStockValue"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ConversionOfConvertiblePreferredStockToCommonStockValue_lbl" xml:lang="en-US" id="id_13073811_3116424_3_1">Conversion of convertible preferred stock to common stock value.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ConversionOfConvertiblePreferredStockToCommonStockValue_lbl" xml:lang="en-US" id="id_13073811_3116424_1_1">Conversion of Convertible Preferred Stock to Common Stock Value</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ConversionOfConvertiblePreferredStockToCommonStockValue_lbl" xml:lang="en-US" id="id_13073811_3116424_2_1">Conversion of convertible preferred stock into common stock</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ConversionOfConvertiblePreferredStockToCommonStockValue" xlink:to="xfor_ConversionOfConvertiblePreferredStockToCommonStockValue_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ConversionOfConvertiblePreferredStockWarrantsToCommonStockWarrants" xlink:label="xfor_ConversionOfConvertiblePreferredStockWarrantsToCommonStockWarrants"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ConversionOfConvertiblePreferredStockWarrantsToCommonStockWarrants_lbl" xml:lang="en-US" id="id_13073811_3151333_3_1">Conversion of convertible preferred stock warrants to common stock warrants.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ConversionOfConvertiblePreferredStockWarrantsToCommonStockWarrants_lbl" xml:lang="en-US" id="id_13073811_3151333_1_1">Conversion Of Convertible Preferred Stock Warrants To Common Stock Warrants</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ConversionOfConvertiblePreferredStockWarrantsToCommonStockWarrants_lbl" xml:lang="en-US" id="id_13073811_3151333_2_1">Conversion of convertible preferred stock warrants into common stock warrants</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ConversionOfConvertiblePreferredStockWarrantsToCommonStockWarrants" xlink:to="xfor_ConversionOfConvertiblePreferredStockWarrantsToCommonStockWarrants_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ConversionOfRedeemableCommonStockToCommonStockShares" xlink:label="xfor_ConversionOfRedeemableCommonStockToCommonStockShares"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ConversionOfRedeemableCommonStockToCommonStockShares_lbl" xml:lang="en-US" id="id_13073811_3566221_3_1">Conversion of redeemable common stock to common stock shares.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ConversionOfRedeemableCommonStockToCommonStockShares_lbl" xml:lang="en-US" id="id_13073811_3566221_1_1">Conversion of Redeemable Common Stock to Common Stock Shares</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ConversionOfRedeemableCommonStockToCommonStockShares_lbl" xml:lang="en-US" id="id_13073811_3566221_2_1">Conversion of redeemable common stock into common stock, shares</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ConversionOfRedeemableCommonStockToCommonStockShares" xlink:to="xfor_ConversionOfRedeemableCommonStockToCommonStockShares_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ConversionOfRedeemableCommonStockToCommonStockValue" xlink:label="xfor_ConversionOfRedeemableCommonStockToCommonStockValue"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ConversionOfRedeemableCommonStockToCommonStockValue_lbl" xml:lang="en-US" id="id_13073811_3566218_3_1">Conversion of redeemable common stock to common stock value.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ConversionOfRedeemableCommonStockToCommonStockValue_lbl" xml:lang="en-US" id="id_13073811_3566218_1_1">Conversion of Redeemable Common Stock to Common Stock Value</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ConversionOfRedeemableCommonStockToCommonStockValue_lbl" xml:lang="en-US" id="id_13073811_3566218_2_1">Conversion of redeemable common stock into common stock</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ConversionOfRedeemableCommonStockToCommonStockValue" xlink:to="xfor_ConversionOfRedeemableCommonStockToCommonStockValue_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ConvertiblePreferredSharesMember" xlink:label="xfor_ConvertiblePreferredSharesMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ConvertiblePreferredSharesMember_lbl" xml:lang="en-US" id="id_13073811_3251702_3_1">Convertible Preferred Shares [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ConvertiblePreferredSharesMember_lbl" xml:lang="en-US" id="id_13073811_3251702_1_1">Convertible Preferred Shares [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ConvertiblePreferredSharesMember_lbl" xml:lang="en-US" id="id_13073811_3251702_2_1">Convertible Preferred Shares [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ConvertiblePreferredSharesMember" xlink:to="xfor_ConvertiblePreferredSharesMember_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_CounterpartyNameAxis_lbl" xml:lang="en-US" id="id_13073811_3066006_1_1">Counterparty Name [Axis]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="srt_CounterpartyNameAxis_lbl" xml:lang="en-US" id="id_13073811_3066006_2_1">Counterparty Name [Axis]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_CounterpartyNameAxis" xlink:to="srt_CounterpartyNameAxis_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="us-gaap_CreditFacilityAxis"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CreditFacilityAxis_lbl" xml:lang="en-US" id="id_13073811_3066013_1_1">Credit Facility [Axis]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CreditFacilityAxis_lbl" xml:lang="en-US" id="id_13073811_3066013_2_1">Credit Facility [Axis]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CreditFacilityAxis" xlink:to="us-gaap_CreditFacilityAxis_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CreditFacilityDomain_lbl" xml:lang="en-US" id="id_13073811_3066014_1_1">Credit Facility [Domain]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CreditFacilityDomain_lbl" xml:lang="en-US" id="id_13073811_3066014_2_1">Credit Facility [Domain]</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CurrentFederalTaxExpenseBenefit" xlink:label="us-gaap_CurrentFederalTaxExpenseBenefit"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CurrentFederalTaxExpenseBenefit_lbl" xml:lang="en-US" id="id_13073811_3066250_1_1">Current Federal Tax Expense (Benefit)</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CurrentFederalTaxExpenseBenefit_lbl" xml:lang="en-US" id="id_13073811_3066250_2_1">Federal income tax benefit</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CurrentFederalTaxExpenseBenefit" xlink:to="us-gaap_CurrentFederalTaxExpenseBenefit_lbl"/>
    <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_CurrentFiscalYearEndDate" xlink:label="dei_CurrentFiscalYearEndDate"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xml:lang="en-US" id="id_13073811_3066670_1_1">Current Fiscal Year End Date</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xml:lang="en-US" id="id_13073811_3066670_2_1">Current Fiscal Year End Date</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_CurrentFiscalYearEndDate" xlink:to="dei_CurrentFiscalYearEndDate_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_CurrentOfficeSpaceUnderLeaseAgreement" xlink:label="xfor_CurrentOfficeSpaceUnderLeaseAgreement"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_CurrentOfficeSpaceUnderLeaseAgreement_lbl" xml:lang="en-US" id="id_13073811_3532964_3_1">Current office space under lease agreement.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_CurrentOfficeSpaceUnderLeaseAgreement_lbl" xml:lang="en-US" id="id_13073811_3532964_1_1">Current Office Space Under Lease Agreement</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_CurrentOfficeSpaceUnderLeaseAgreement_lbl" xml:lang="en-US" id="id_13073811_3532964_2_1">Current office space under lease agreement</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_CurrentOfficeSpaceUnderLeaseAgreement" xlink:to="xfor_CurrentOfficeSpaceUnderLeaseAgreement_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CurrentStateAndLocalTaxExpenseBenefit" xlink:label="us-gaap_CurrentStateAndLocalTaxExpenseBenefit"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CurrentStateAndLocalTaxExpenseBenefit_lbl" xml:lang="en-US" id="id_13073811_3066412_1_1">Current State and Local Tax Expense (Benefit)</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CurrentStateAndLocalTaxExpenseBenefit_lbl" xml:lang="en-US" id="id_13073811_3066412_2_1">State income tax benefit</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CurrentStateAndLocalTaxExpenseBenefit" xlink:to="us-gaap_CurrentStateAndLocalTaxExpenseBenefit_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_DebtCovenantMinimumLiquidityPercentageOfCashAndCashEquivalents" xlink:label="xfor_DebtCovenantMinimumLiquidityPercentageOfCashAndCashEquivalents"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_DebtCovenantMinimumLiquidityPercentageOfCashAndCashEquivalents_lbl" xml:lang="en-US" id="id_13073811_3566865_3_1">Debt Covenant Minimum Liquidity Percentage Of Cash And Cash Equivalents.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_DebtCovenantMinimumLiquidityPercentageOfCashAndCashEquivalents_lbl" xml:lang="en-US" id="id_13073811_3566865_1_1">Debt Covenant Minimum Liquidity Percentage Of Cash And Cash Equivalents</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_DebtCovenantMinimumLiquidityPercentageOfCashAndCashEquivalents_lbl" xml:lang="en-US" id="id_13073811_3566865_2_1">Minimum liquidity as a percentage of debt</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_DebtCovenantMinimumLiquidityPercentageOfCashAndCashEquivalents" xlink:to="xfor_DebtCovenantMinimumLiquidityPercentageOfCashAndCashEquivalents_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_DebtCovenantMinimumLiquidityPercentageOfOutstandingBorrowings" xlink:label="xfor_DebtCovenantMinimumLiquidityPercentageOfOutstandingBorrowings"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_DebtCovenantMinimumLiquidityPercentageOfOutstandingBorrowings_lbl" xml:lang="en-US" id="id_13073811_3566863_3_1">Debt covenant minimum liquidity percentage of outstanding borrowings.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_DebtCovenantMinimumLiquidityPercentageOfOutstandingBorrowings_lbl" xml:lang="en-US" id="id_13073811_3566863_1_1">Debt Covenant Minimum Liquidity Percentage Of Outstanding Borrowings</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_DebtCovenantMinimumLiquidityPercentageOfOutstandingBorrowings_lbl" xml:lang="en-US" id="id_13073811_3566863_2_1">Minimum liquidity as a percentage of debt</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_DebtCovenantMinimumLiquidityPercentageOfOutstandingBorrowings" xlink:to="xfor_DebtCovenantMinimumLiquidityPercentageOfOutstandingBorrowings_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtDisclosureAbstract" xlink:label="us-gaap_DebtDisclosureAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtDisclosureAbstract_lbl" xml:lang="en-US" id="id_13073811_3066703_1_1">Debt Disclosure [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtDisclosureAbstract_lbl" xml:lang="en-US" id="id_13073811_3066703_2_1">Debt Disclosure [Abstract]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtDisclosureAbstract" xlink:to="us-gaap_DebtDisclosureAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_DebtInstrumentAccruedInterest" xlink:label="xfor_DebtInstrumentAccruedInterest"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_DebtInstrumentAccruedInterest_lbl" xml:lang="en-US" id="id_13073811_3147524_3_1">Debt Instrument Accrued Interest</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_DebtInstrumentAccruedInterest_lbl" xml:lang="en-US" id="id_13073811_3147524_1_1">Debt Instrument Accrued Interest</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_DebtInstrumentAccruedInterest_lbl" xml:lang="en-US" id="id_13073811_3147524_2_1">Debt instrument accrued interest</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_DebtInstrumentAccruedInterest" xlink:to="xfor_DebtInstrumentAccruedInterest_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentAxis_lbl" xml:lang="en-US" id="id_13073811_3066061_1_1">Debt Instrument [Axis]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtInstrumentAxis_lbl" xml:lang="en-US" id="id_13073811_3066061_2_1">Debt Instrument [Axis]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentAxis_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl" xml:lang="en-US" id="id_13073811_3066062_1_1">Debt Instrument, Basis Spread on Variable Rate</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl" xml:lang="en-US" id="id_13073811_3066062_2_1">Debt instrument variable percentage</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:to="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_DebtInstrumentCarryingValue" xlink:label="xfor_DebtInstrumentCarryingValue"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_DebtInstrumentCarryingValue_lbl" xml:lang="en-US" id="id_13073811_3171096_3_1">Debt Instrument Carrying Value</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_DebtInstrumentCarryingValue_lbl" xml:lang="en-US" id="id_13073811_3171096_1_1">Debt Instrument Carrying Value</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_DebtInstrumentCarryingValue_lbl" xml:lang="en-US" id="id_13073811_3171096_2_1">Debt instrument carrying value</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_DebtInstrumentCarryingValue" xlink:to="xfor_DebtInstrumentCarryingValue_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentDescriptionOfVariableRateBasis" xlink:label="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis_lbl" xml:lang="en-US" id="id_13073811_3066710_1_1">Debt Instrument, Description of Variable Rate Basis</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis_lbl" xml:lang="en-US" id="id_13073811_3066710_2_1">Debt instrument description</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis" xlink:to="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage" xlink:label="us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentInterestRateEffectivePercentage_lbl" xml:lang="en-US" id="id_13073811_3066078_1_1">Debt Instrument, Interest Rate, Effective Percentage</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtInstrumentInterestRateEffectivePercentage_lbl" xml:lang="en-US" id="id_13073811_3066078_2_1">Effective interest rate of loan</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentInterestRateEffectivePercentage" xlink:to="us-gaap_DebtInstrumentInterestRateEffectivePercentage_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentInterestRateIncreaseDecrease" xlink:label="us-gaap_DebtInstrumentInterestRateIncreaseDecrease"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentInterestRateIncreaseDecrease_lbl" xml:lang="en-US" id="id_13073811_3066307_1_1">Debt Instrument, Interest Rate, Increase (Decrease)</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtInstrumentInterestRateIncreaseDecrease_lbl" xml:lang="en-US" id="id_13073811_3066307_2_1">Interest rate increase percentage</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentInterestRateIncreaseDecrease" xlink:to="us-gaap_DebtInstrumentInterestRateIncreaseDecrease_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xml:lang="en-US" id="id_13073811_3066308_1_1">Debt Instrument, Interest Rate, Stated Percentage</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/positiveLabel" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xml:lang="en-US" id="id_13073811_3066308_32_1">Debt instrument, interest rate</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xml:lang="en-US" id="id_13073811_3066308_2_1">Debt instrument interest rate</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xml:lang="en-US" id="id_13073811_3066308_12_1">Debt instrument stated percentage</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:to="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentMaturityDateRangeEnd1" xlink:label="us-gaap_DebtInstrumentMaturityDateRangeEnd1"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentMaturityDateRangeEnd1_lbl" xml:lang="en-US" id="id_13073811_3066466_1_1">Debt Instrument, Maturity Date Range, End</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtInstrumentMaturityDateRangeEnd1_lbl" xml:lang="en-US" id="id_13073811_3066466_2_1">Debt instrument, maturity end date</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentMaturityDateRangeEnd1" xlink:to="us-gaap_DebtInstrumentMaturityDateRangeEnd1_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentMaturityDateRangeStart1" xlink:label="us-gaap_DebtInstrumentMaturityDateRangeStart1"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentMaturityDateRangeStart1_lbl" xml:lang="en-US" id="id_13073811_3066082_1_1">Debt Instrument, Maturity Date Range, Start</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtInstrumentMaturityDateRangeStart1_lbl" xml:lang="en-US" id="id_13073811_3066082_2_1">Debt instrument, maturity start date</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentMaturityDateRangeStart1" xlink:to="us-gaap_DebtInstrumentMaturityDateRangeStart1_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentNameDomain_lbl" xml:lang="en-US" id="id_13073811_3066716_1_1">Debt Instrument, Name [Domain]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_DebtInstrumentPrepaymentPremium_lbl" xml:lang="en-US" id="id_13073811_3172088_3_1">Debt Instrument, Prepayment Premium</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_DebtInstrumentPrepaymentPremium_lbl" xml:lang="en-US" id="id_13073811_3172088_1_1">Debt Instrument, Prepayment Premium</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_DebtInstrumentPrepaymentPremium_lbl" xml:lang="en-US" id="id_13073811_3172088_2_1">Debt instrument prepayment premium</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_DebtInstrumentPrePaymentPremiumPercentage_lbl" xml:lang="en-US" id="id_13073811_3362763_3_1">Debt Instrument Pre Payment Premium Percentage</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_DebtInstrumentPrePaymentPremiumPercentage_lbl" xml:lang="en-US" id="id_13073811_3362763_1_1">Debt Instrument Pre Payment Premium Percentage</label>
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    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_DebtInstrumentPrePaymentPremiumPercentage" xlink:to="xfor_DebtInstrumentPrePaymentPremiumPercentage_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentRedemptionDescription_lbl" xml:lang="en-US" id="id_13073811_3066312_1_1">Debt Instrument, Redemption, Description</label>
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    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentRedemptionDescription" xlink:to="us-gaap_DebtInstrumentRedemptionDescription_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentUnamortizedDiscount" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscount"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscount_lbl" xml:lang="en-US" id="id_13073811_3066726_1_1">Debt Instrument, Unamortized Discount</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscount_lbl" xml:lang="en-US" id="id_13073811_3066726_2_1">Unamortized debt discount</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscount_lbl" xml:lang="en-US" id="id_13073811_3066726_14_1">Debt discount, net of accretion</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentUnamortizedDiscount" xlink:to="us-gaap_DebtInstrumentUnamortizedDiscount_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_DebtMaturitiesLineItems" xlink:label="xfor_DebtMaturitiesLineItems"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_DebtMaturitiesLineItems_lbl" xml:lang="en-US" id="id_13073811_3388305_3_1">Debt Maturities [Line Items]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_DebtMaturitiesLineItems_lbl" xml:lang="en-US" id="id_13073811_3388305_1_1">Debt Maturities [Line Items]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_DebtMaturitiesLineItems_lbl" xml:lang="en-US" id="id_13073811_3388305_2_1">Debt Maturities [Line Items]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_DebtMaturitiesLineItems" xlink:to="xfor_DebtMaturitiesLineItems_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtPolicyTextBlock" xlink:label="us-gaap_DebtPolicyTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3066740_1_1">Debt, Policy [Policy Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3066740_2_1">Debt Issuance Costs</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtPolicyTextBlock" xlink:to="us-gaap_DebtPolicyTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredRentCredit" xlink:label="us-gaap_DeferredRentCredit"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DeferredRentCredit_lbl" xml:lang="en-US" id="id_13073811_3067192_1_1">Deferred Rent Credit</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DeferredRentCredit_lbl" xml:lang="en-US" id="id_13073811_3067192_2_1">Net deferred, accrued and prepaid rent</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredRentCredit" xlink:to="us-gaap_DeferredRentCredit_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredRentCreditCurrent" xlink:label="us-gaap_DeferredRentCreditCurrent"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DeferredRentCreditCurrent_lbl" xml:lang="en-US" id="id_13073811_3066838_1_1">Deferred Rent Credit, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DeferredRentCreditCurrent_lbl" xml:lang="en-US" id="id_13073811_3066838_2_1">Deferred rent, current portion</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredRentCreditCurrent" xlink:to="us-gaap_DeferredRentCreditCurrent_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredRentCreditNoncurrent" xlink:label="us-gaap_DeferredRentCreditNoncurrent"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DeferredRentCreditNoncurrent_lbl" xml:lang="en-US" id="id_13073811_3067063_1_1">Deferred Rent Credit, Noncurrent</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DeferredRentCreditNoncurrent_lbl" xml:lang="en-US" id="id_13073811_3067063_2_1">Deferred rent</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredRentCreditNoncurrent" xlink:to="us-gaap_DeferredRentCreditNoncurrent_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_DeferredRentPolicyTextBlock" xlink:label="xfor_DeferredRentPolicyTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_DeferredRentPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3348351_3_1">Deferred Rent Policy.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_DeferredRentPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3348351_1_1">Deferred Rent [Policy Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_DeferredRentPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3348351_2_1">Deferred Rent</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_DeferredRentPolicyTextBlock" xlink:to="xfor_DeferredRentPolicyTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="us-gaap_DepreciationDepletionAndAmortization"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DepreciationDepletionAndAmortization_lbl" xml:lang="en-US" id="id_13073811_3067619_1_1">Depreciation, Depletion and Amortization</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DepreciationDepletionAndAmortization_lbl" xml:lang="en-US" id="id_13073811_3067619_2_1">Depreciation and amortization expense</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_DepreciationDepletionAndAmortization_lbl" xml:lang="en-US" id="id_13073811_3067619_12_1">Depreciation expense</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DepreciationDepletionAndAmortization" xlink:to="us-gaap_DepreciationDepletionAndAmortization_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DerivativeFairValueOfDerivativeLiability_lbl" xml:lang="en-US" id="id_13073811_3068328_1_1">Derivative Liability, Fair Value, Gross Liability</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/positiveLabel" xlink:label="us-gaap_DerivativeFairValueOfDerivativeLiability_lbl" xml:lang="en-US" id="id_13073811_3068328_32_1">Fair value of warrants</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DerivativeFairValueOfDerivativeLiability_lbl" xml:lang="en-US" id="id_13073811_3068328_2_1">Fair value of derivative liability</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_DerivativeFairValueOfDerivativeLiability_lbl" xml:lang="en-US" id="id_13073811_3068328_12_1">Fair value of warrant purchase</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeFairValueOfDerivativeLiability" xlink:to="us-gaap_DerivativeFairValueOfDerivativeLiability_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember" xlink:label="us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_lbl" xml:lang="en-US" id="id_13073811_3067382_1_1">Derivative Financial Instruments, Liabilities [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_lbl" xml:lang="en-US" id="id_13073811_3067382_2_1">Derivative Liability [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember" xlink:to="us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DerivativeGainLossOnDerivativeNet_lbl" xml:lang="en-US" id="id_13073811_3067386_1_1">Derivative, Gain (Loss) on Derivative, Net</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DerivativeGainLossOnDerivativeNet_lbl" xml:lang="en-US" id="id_13073811_3067386_2_1">Change in fair value of derivative liability</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_DerivativeGainLossOnDerivativeNet_lbl" xml:lang="en-US" id="id_13073811_3067386_14_1">Change in fair value of derivative liability</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeGainLossOnDerivativeNet" xlink:to="us-gaap_DerivativeGainLossOnDerivativeNet_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract_lbl" xml:lang="en-US" id="id_13073811_3067916_1_1">Derivative Instruments and Hedging Activities Disclosure [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract_lbl" xml:lang="en-US" id="id_13073811_3067916_2_1">Derivative Instruments and Hedging Activities Disclosure [Abstract]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:to="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock_lbl" xml:lang="en-US" id="id_13073811_3067919_1_1">Derivative Instruments and Hedging Activities Disclosure [Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock_lbl" xml:lang="en-US" id="id_13073811_3067919_2_1">Preferred and Common Stock Warrants</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock" xlink:to="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeLiabilities" xlink:label="us-gaap_DerivativeLiabilities"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DerivativeLiabilities_lbl" xml:lang="en-US" id="id_13073811_3068346_1_1">Derivative Liability</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DerivativeLiabilities_lbl" xml:lang="en-US" id="id_13073811_3068346_2_1">Derivative Liability</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_DerivativeLiabilities_lbl" xml:lang="en-US" id="id_13073811_3068346_12_1">Fair value of derivative liability</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeLiabilities" xlink:to="us-gaap_DerivativeLiabilities_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativesPolicyTextBlock" xlink:label="us-gaap_DerivativesPolicyTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DerivativesPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3068067_1_1">Derivatives, Policy [Policy Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DerivativesPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3068067_2_1">Derivative Liability</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativesPolicyTextBlock" xlink:to="us-gaap_DerivativesPolicyTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract_lbl" xml:lang="en-US" id="id_13073811_3068434_1_1">Disclosure of Compensation Related Costs, Share-based Payments [Abstract]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xml:lang="en-US" id="id_13073811_3069403_1_1">Fair Value Hierarchy and NAV [Domain]</label>
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    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_FairValueMeasurementWithUnobservableInputsConversionOfConvertiblePreferredStockWarrantsIntoCommonStockWarrantsInConnectionWithMerger" xlink:label="xfor_FairValueMeasurementWithUnobservableInputsConversionOfConvertiblePreferredStockWarrantsIntoCommonStockWarrantsInConnectionWithMerger"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_FairValueMeasurementWithUnobservableInputsConversionOfConvertiblePreferredStockWarrantsIntoCommonStockWarrantsInConnectionWithMerger_lbl" xml:lang="en-US" id="id_13073811_3566576_3_1">Fair value measurement with unobservable inputs conversion of convertible preferred stock warrants into common stock warrants in connection with merger.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_FairValueMeasurementWithUnobservableInputsConversionOfConvertiblePreferredStockWarrantsIntoCommonStockWarrantsInConnectionWithMerger_lbl" xml:lang="en-US" id="id_13073811_3566576_1_1">Fair Value Measurement With Unobservable Inputs Conversion Of Convertible Preferred Stock Warrants Into Common Stock Warrants In Connection With Merger</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="xfor_FairValueMeasurementWithUnobservableInputsConversionOfConvertiblePreferredStockWarrantsIntoCommonStockWarrantsInConnectionWithMerger_lbl" xml:lang="en-US" id="id_13073811_3566576_14_1">Conversion of convertible preferred stock warrant into common stock warrant in connection with Merger</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPeriodIncreaseDecrease" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPeriodIncreaseDecrease"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPeriodIncreaseDecrease_lbl" xml:lang="en-US" id="id_13073811_3070139_1_1">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease)</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_lbl" xml:lang="en-US" id="id_13073811_3069417_1_1">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_lbl" xml:lang="en-US" id="id_13073811_3069417_4_1">Balance as of March 31, 2019</label>
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    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_FairValueOfCommonStockPerShare" xlink:label="xfor_FairValueOfCommonStockPerShare"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_FairValueOfCommonStockPerShare_lbl" xml:lang="en-US" id="id_13073811_3353885_2_1">Multiplied by the fair value per share of Arsanis common stock</label>
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    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_FairValueOfNetAssetsAcquiredInReverseMerger" xlink:label="xfor_FairValueOfNetAssetsAcquiredInReverseMerger"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_FairValueOfNetAssetsAcquiredInReverseMerger_lbl" xml:lang="en-US" id="id_13073811_3566991_3_1">Fair value of net assets acquired in reverse merger.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_FairValueOfNetAssetsAcquiredInReverseMerger_lbl" xml:lang="en-US" id="id_13073811_3566991_1_1">Fair Value Of Net Assets Acquired In Reverse Merger</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_FairValueOfNetAssetsAcquiredInReverseMerger_lbl" xml:lang="en-US" id="id_13073811_3566991_2_1">Fair value of net assets acquired in Merger</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_FairValueOfNetAssetsAcquiredInReverseMerger" xlink:to="xfor_FairValueOfNetAssetsAcquiredInReverseMerger_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_FairValueOfReplacementEquityAwards" xlink:label="xfor_FairValueOfReplacementEquityAwards"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_FairValueOfReplacementEquityAwards_lbl" xml:lang="en-US" id="id_13073811_3566172_3_1">Fair Value of replacement equity awards.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_FairValueOfReplacementEquityAwards_lbl" xml:lang="en-US" id="id_13073811_3566172_1_1">Fair Value of Replacement Equity Awards</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_FairValueOfReplacementEquityAwards_lbl" xml:lang="en-US" id="id_13073811_3566172_2_1">Fair value of replacement awards held by former employees, board of directors and consultants of Arsanis that were vested as of the Merger.</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_FairValueOfReplacementEquityAwards" xlink:to="xfor_FairValueOfReplacementEquityAwards_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueOptionChangesInFairValueGainLoss1" xlink:label="us-gaap_FairValueOptionChangesInFairValueGainLoss1"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FairValueOptionChangesInFairValueGainLoss1_lbl" xml:lang="en-US" id="id_13073811_3069843_1_1">Fair Value, Option, Changes in Fair Value, Gain (Loss)</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_FairValueOptionChangesInFairValueGainLoss1_lbl" xml:lang="en-US" id="id_13073811_3069843_2_1">Gain (loss) on change in fair value of warrant</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueOptionChangesInFairValueGainLoss1" xlink:to="us-gaap_FairValueOptionChangesInFairValueGainLoss1_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_FairValueTransfersBetweenLevel1Level2OrLevel3Amount" xlink:label="xfor_FairValueTransfersBetweenLevel1Level2OrLevel3Amount"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_FairValueTransfersBetweenLevel1Level2OrLevel3Amount_lbl" xml:lang="en-US" id="id_13073811_3393268_3_1">Fair value transfers between Level 1, Level 2 and Level 3 amount.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_FairValueTransfersBetweenLevel1Level2OrLevel3Amount_lbl" xml:lang="en-US" id="id_13073811_3393268_1_1">Fair Value Transfers Between Level 1 Level 2 Or Level 3 Amount</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_FairValueTransfersBetweenLevel1Level2OrLevel3Amount_lbl" xml:lang="en-US" id="id_13073811_3393268_2_1">Transfers between fair value levels</label>
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    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_FebruaryTwoThousandAndSeventeenGrantAgreementMember" xlink:label="xfor_FebruaryTwoThousandAndSeventeenGrantAgreementMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_FebruaryTwoThousandAndSeventeenGrantAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3532969_3_1">February two thousand and seventeen grant agreement.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_FebruaryTwoThousandAndSeventeenGrantAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3532969_1_1">February Two Thousand And Seventeen Grant Agreement [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_FebruaryTwoThousandAndSeventeenGrantAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3532969_2_1">February 2017 Grant Agreement</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_FebruaryTwoThousandAndSeventeenGrantAgreementMember" xlink:to="xfor_FebruaryTwoThousandAndSeventeenGrantAgreementMember_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FederalHomeLoanBanksAbstract" xlink:label="us-gaap_FederalHomeLoanBanksAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FederalHomeLoanBanksAbstract_lbl" xml:lang="en-US" id="id_13073811_3069758_1_1">Federal Home Loan Banks [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_FederalHomeLoanBanksAbstract_lbl" xml:lang="en-US" id="id_13073811_3069758_2_1">Federal Home Loan Banks [Abstract]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FederalHomeLoanBanksAbstract" xlink:to="us-gaap_FederalHomeLoanBanksAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_FfgLoanAgreementMember" xlink:label="xfor_FfgLoanAgreementMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_FfgLoanAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3567104_3_1">FFG Loan Agreement [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_FfgLoanAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3567104_1_1">FFG Loan Agreement [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_FfgLoanAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3567104_2_1">FFG Loan Agreement [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_FfgLoanAgreementMember" xlink:to="xfor_FfgLoanAgreementMember_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract" xlink:label="us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_lbl" xml:lang="en-US" id="id_13073811_3070895_1_1">Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_lbl" xml:lang="en-US" id="id_13073811_3070895_2_1">Assets:</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract" xlink:to="us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract" xlink:label="us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_lbl" xml:lang="en-US" id="id_13073811_3070455_1_1">Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_lbl" xml:lang="en-US" id="id_13073811_3070455_2_1">Liabilities:</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract" xlink:to="us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_lbl" xml:lang="en-US" id="id_13073811_3070943_1_1">Finite-Lived Intangible Assets by Major Class [Axis]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_lbl" xml:lang="en-US" id="id_13073811_3070943_2_1">Finite-Lived Intangible Assets by Major Class [Axis]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_GrantAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3244729_1_1">Grant Agreement [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_GrantAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3244729_2_1">Grant Agreement [Member]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_HerculesLoanAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3384925_1_1">Hercules Loan Agreement [Member]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_IncomeStatementAbstract_lbl" xml:lang="en-US" id="id_13073811_3071185_2_1">Numerator:</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_IndemnificationAgreementsMember_lbl" xml:lang="en-US" id="id_13073811_3566762_3_1">Indemnification Agreements Member.</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_IntangibleAssetsFiniteLivedPolicyCostsIncurredToRenewOrExtend_lbl" xml:lang="en-US" id="id_13073811_3071965_2_1">Patent Costs</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IntangibleAssetsFiniteLivedPolicyCostsIncurredToRenewOrExtend" xlink:to="us-gaap_IntangibleAssetsFiniteLivedPolicyCostsIncurredToRenewOrExtend_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill" xlink:label="us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_IntangibleAssetsNetExcludingGoodwill_lbl" xml:lang="en-US" id="id_13073811_3072262_2_1">Intangible assets</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IntangibleAssetsNetExcludingGoodwill" xlink:to="us-gaap_IntangibleAssetsNetExcludingGoodwill_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_IntangibleAssetsPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3343086_3_1">Intangible Assets [Policy Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_IntangibleAssetsPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3343086_1_1">Intangible Assets [Policy Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_IntangibleAssetsPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3343086_2_1">Intangible Assets</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_InterestExpense_lbl" xml:lang="en-US" id="id_13073811_3071986_1_1">Interest Expense</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_InvestmentIncomeInterest_lbl" xml:lang="en-US" id="id_13073811_3073036_2_1">Interest income</label>
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    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_IssuanceOnAugustFourteenTwoThousandFifteenMember" xlink:label="xfor_IssuanceOnAugustFourteenTwoThousandFifteenMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_IssuanceOnAugustFourteenTwoThousandFifteenMember_lbl" xml:lang="en-US" id="id_13073811_3566785_3_1">Issuance on August Fourteen Two Thousand Fifteen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_IssuanceOnAugustFourteenTwoThousandFifteenMember_lbl" xml:lang="en-US" id="id_13073811_3566785_1_1">Issuance On August Fourteen Two Thousand Fifteen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_IssuanceOnAugustFourteenTwoThousandFifteenMember_lbl" xml:lang="en-US" id="id_13073811_3566785_2_1">Issuance On August 14, 2015 [Member]</label>
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    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_IssuanceOnAugustTwentyOneTwoThousandFifteenMember" xlink:label="xfor_IssuanceOnAugustTwentyOneTwoThousandFifteenMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_IssuanceOnAugustTwentyOneTwoThousandFifteenMember_lbl" xml:lang="en-US" id="id_13073811_3566787_3_1">Issuance on August Twenty One Two Thousand Fifteen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_IssuanceOnAugustTwentyOneTwoThousandFifteenMember_lbl" xml:lang="en-US" id="id_13073811_3566787_1_1">Issuance On August Twenty One Two Thousand Fifteen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_IssuanceOnAugustTwentyOneTwoThousandFifteenMember_lbl" xml:lang="en-US" id="id_13073811_3566787_2_1">Issuance On August 21, 2015 [Member]</label>
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    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_IssuanceOnDecemberElevenTwoThousandEighteenMember" xlink:label="xfor_IssuanceOnDecemberElevenTwoThousandEighteenMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_IssuanceOnDecemberElevenTwoThousandEighteenMember_lbl" xml:lang="en-US" id="id_13073811_3566798_3_1">Issuance On December Eleven Two Thousand Eighteen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_IssuanceOnDecemberElevenTwoThousandEighteenMember_lbl" xml:lang="en-US" id="id_13073811_3566798_1_1">Issuance On December Eleven Two Thousand Eighteen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_IssuanceOnDecemberElevenTwoThousandEighteenMember_lbl" xml:lang="en-US" id="id_13073811_3566798_2_1">Issuance On December 11, 2018 [Member]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_IssuanceOnDecemberFourTwoThousandSeventeenMember_lbl" xml:lang="en-US" id="id_13073811_3566792_3_1">Issuance on December Four Two Thousand Seventeen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_IssuanceOnDecemberFourTwoThousandSeventeenMember_lbl" xml:lang="en-US" id="id_13073811_3566792_1_1">Issuance On December Four Two Thousand Seventeen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_IssuanceOnDecemberFourTwoThousandSeventeenMember_lbl" xml:lang="en-US" id="id_13073811_3566792_2_1">Issuance On December 4, 2017 [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_IssuanceOnDecemberFourTwoThousandSeventeenMember" xlink:to="xfor_IssuanceOnDecemberFourTwoThousandSeventeenMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenMember" xlink:label="xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenMember_lbl" xml:lang="en-US" id="id_13073811_3566793_3_1">Issuance on December Twenty Eight Two Thousand Seventeen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenMember_lbl" xml:lang="en-US" id="id_13073811_3566793_1_1">Issuance On December Twenty Eight Two Thousand Seventeen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenMember_lbl" xml:lang="en-US" id="id_13073811_3566793_2_1">Issuance On December 28, 2017 [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenMember" xlink:to="xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenOneMember" xlink:label="xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenOneMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenOneMember_lbl" xml:lang="en-US" id="id_13073811_3566816_3_1">Issuance on December Twenty Eight Two Thousand Seventeen One [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenOneMember_lbl" xml:lang="en-US" id="id_13073811_3566816_1_1">Issuance On December Twenty Eight Two Thousand Seventeen One [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenOneMember_lbl" xml:lang="en-US" id="id_13073811_3566816_2_1">Issuance On December 28, 2017 One [Member]</label>
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    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_IssuanceOnNovemberOneTwoThousandSeventeenMember" xlink:label="xfor_IssuanceOnNovemberOneTwoThousandSeventeenMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_IssuanceOnNovemberOneTwoThousandSeventeenMember_lbl" xml:lang="en-US" id="id_13073811_3566790_3_1">Issuance on November One Two Thousand Seventeen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_IssuanceOnNovemberOneTwoThousandSeventeenMember_lbl" xml:lang="en-US" id="id_13073811_3566790_1_1">Issuance On November One Two Thousand Seventeen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_IssuanceOnNovemberOneTwoThousandSeventeenMember_lbl" xml:lang="en-US" id="id_13073811_3566790_2_1">Issuance On November 1, 2017 [Member]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_IssuanceOnNovemberSeventeenTwoThousandSeventeenMember_lbl" xml:lang="en-US" id="id_13073811_3566791_3_1">Issuance on November Seventeen Two Thousand Seventeen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_IssuanceOnNovemberSeventeenTwoThousandSeventeenMember_lbl" xml:lang="en-US" id="id_13073811_3566791_1_1">Issuance On November Seventeen Two Thousand Seventeen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_IssuanceOnNovemberSeventeenTwoThousandSeventeenMember_lbl" xml:lang="en-US" id="id_13073811_3566791_2_1">Issuance On November 17, 2017 [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_IssuanceOnNovemberSeventeenTwoThousandSeventeenMember" xlink:to="xfor_IssuanceOnNovemberSeventeenTwoThousandSeventeenMember_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_IssuanceOnOctoberNineteenTwoThousandEighteenMember_lbl" xml:lang="en-US" id="id_13073811_3566795_3_1">Issuance on October Nineteen Two Thousand Eighteen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_IssuanceOnOctoberNineteenTwoThousandEighteenMember_lbl" xml:lang="en-US" id="id_13073811_3566795_1_1">Issuance On October Nineteen Two Thousand Eighteen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_IssuanceOnOctoberNineteenTwoThousandEighteenMember_lbl" xml:lang="en-US" id="id_13073811_3566795_2_1">Issuance On October 19, 2018 [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_IssuanceOnOctoberNineteenTwoThousandEighteenMember" xlink:to="xfor_IssuanceOnOctoberNineteenTwoThousandEighteenMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_IssuanceOnOctoberTwentyFiveTwoThousandSixteenMember" xlink:label="xfor_IssuanceOnOctoberTwentyFiveTwoThousandSixteenMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_IssuanceOnOctoberTwentyFiveTwoThousandSixteenMember_lbl" xml:lang="en-US" id="id_13073811_3566789_3_1">Issuance on October Twenty Five Two Thousand Sixteen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_IssuanceOnOctoberTwentyFiveTwoThousandSixteenMember_lbl" xml:lang="en-US" id="id_13073811_3566789_1_1">Issuance On October Twenty Five Two Thousand Sixteen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_IssuanceOnOctoberTwentyFiveTwoThousandSixteenMember_lbl" xml:lang="en-US" id="id_13073811_3566789_2_1">Issuance On October 25, 2016 [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_IssuanceOnOctoberTwentyFiveTwoThousandSixteenMember" xlink:to="xfor_IssuanceOnOctoberTwentyFiveTwoThousandSixteenMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenMember" xlink:label="xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenMember_lbl" xml:lang="en-US" id="id_13073811_3566794_3_1">Issuance on September Twelve Two Thousand Eighteen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenMember_lbl" xml:lang="en-US" id="id_13073811_3566794_1_1">Issuance On September Twelve Two Thousand Eighteen [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenMember_lbl" xml:lang="en-US" id="id_13073811_3566794_2_1">Issuance On September 12, 2018 [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenMember" xlink:to="xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenOneMember" xlink:label="xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenOneMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenOneMember_lbl" xml:lang="en-US" id="id_13073811_3566822_3_1">Issuance on September Twelve Two Thousand Eighteen One [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenOneMember_lbl" xml:lang="en-US" id="id_13073811_3566822_1_1">Issuance On September Twelve Two Thousand Eighteen One [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenOneMember_lbl" xml:lang="en-US" id="id_13073811_3566822_2_1">Issuance On September 12, 2018 One [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenOneMember" xlink:to="xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenOneMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_JanssenLicenseAndOptionAgreementMember" xlink:label="xfor_JanssenLicenseAndOptionAgreementMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_JanssenLicenseAndOptionAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3566590_3_1">Janssen License And Option Agreement [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_JanssenLicenseAndOptionAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3566590_1_1">Janssen License And Option Agreement [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_JanssenLicenseAndOptionAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3566590_2_1">Janssen License and Option Agreement [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_JanssenLicenseAndOptionAgreementMember" xlink:to="xfor_JanssenLicenseAndOptionAgreementMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_JanssenPharmaceuticalsIncorporationMember" xlink:label="xfor_JanssenPharmaceuticalsIncorporationMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_JanssenPharmaceuticalsIncorporationMember_lbl" xml:lang="en-US" id="id_13073811_3566591_3_1">Janssen Pharmaceuticals Incorporation [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_JanssenPharmaceuticalsIncorporationMember_lbl" xml:lang="en-US" id="id_13073811_3566591_1_1">Janssen Pharmaceuticals Incorporation [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_JanssenPharmaceuticalsIncorporationMember_lbl" xml:lang="en-US" id="id_13073811_3566591_2_1">Janssen Pharmaceuticals Incorporation [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_JanssenPharmaceuticalsIncorporationMember" xlink:to="xfor_JanssenPharmaceuticalsIncorporationMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_LabEquipmentMember" xlink:label="xfor_LabEquipmentMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_LabEquipmentMember_lbl" xml:lang="en-US" id="id_13073811_3265131_3_1">Lab Equipment [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_LabEquipmentMember_lbl" xml:lang="en-US" id="id_13073811_3265131_1_1">Lab Equipment [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_LabEquipmentMember_lbl" xml:lang="en-US" id="id_13073811_3265131_2_1">Lab Equipment [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_LabEquipmentMember" xlink:to="xfor_LabEquipmentMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_LeaseAgreementExtensionDescription" xlink:label="xfor_LeaseAgreementExtensionDescription"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_LeaseAgreementExtensionDescription_lbl" xml:lang="en-US" id="id_13073811_3532971_3_1">Lease agreement extension description.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_LeaseAgreementExtensionDescription_lbl" xml:lang="en-US" id="id_13073811_3532971_1_1">Lease Agreement Extension Description</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_LeaseAgreementExtensionDescription_lbl" xml:lang="en-US" id="id_13073811_3532971_2_1">Option to extend the lease agreement</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_LeaseAgreementExtensionDescription" xlink:to="xfor_LeaseAgreementExtensionDescription_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_LeaseAgreementPeriodOfWrittenNoticeForCancellable" xlink:label="xfor_LeaseAgreementPeriodOfWrittenNoticeForCancellable"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_LeaseAgreementPeriodOfWrittenNoticeForCancellable_lbl" xml:lang="en-US" id="id_13073811_3566995_3_1">Lease agreement period of written notice for cancellable.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_LeaseAgreementPeriodOfWrittenNoticeForCancellable_lbl" xml:lang="en-US" id="id_13073811_3566995_1_1">Lease Agreement Period Of Written Notice For Cancellable</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_LeaseAgreementPeriodOfWrittenNoticeForCancellable_lbl" xml:lang="en-US" id="id_13073811_3566995_2_1">Period for written notice for cancellable</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_LeaseAgreementPeriodOfWrittenNoticeForCancellable" xlink:to="xfor_LeaseAgreementPeriodOfWrittenNoticeForCancellable_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeaseArrangementTypeAxis" xlink:label="us-gaap_LeaseArrangementTypeAxis"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LeaseArrangementTypeAxis_lbl" xml:lang="en-US" id="id_13073811_3073336_1_1">Lease Arrangement, Type [Axis]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LeaseArrangementTypeAxis_lbl" xml:lang="en-US" id="id_13073811_3073336_2_1">Lease Arrangement, Type [Axis]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeaseArrangementTypeAxis" xlink:to="us-gaap_LeaseArrangementTypeAxis_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="us-gaap_LeaseArrangementTypeDomain"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LeaseArrangementTypeDomain_lbl" xml:lang="en-US" id="id_13073811_3073565_1_1">Lease Arrangement, Type [Domain]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LeaseArrangementTypeDomain_lbl" xml:lang="en-US" id="id_13073811_3073565_2_1">Lease Arrangement, Type [Domain]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeaseArrangementTypeDomain" xlink:to="us-gaap_LeaseArrangementTypeDomain_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeaseCost" xlink:label="us-gaap_LeaseCost"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LeaseCost_lbl" xml:lang="en-US" id="id_13073811_3073337_1_1">Lease, Cost</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_LeaseCost_lbl" xml:lang="en-US" id="id_13073811_3073337_6_1">Total lease expense</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeaseCost" xlink:to="us-gaap_LeaseCost_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeaseCostTableTextBlock" xlink:label="us-gaap_LeaseCostTableTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LeaseCostTableTextBlock_lbl" xml:lang="en-US" id="id_13073811_3073338_1_1">Lease, Cost [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LeaseCostTableTextBlock_lbl" xml:lang="en-US" id="id_13073811_3073338_2_1">Schedule of Components of Lease Expense</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeaseCostTableTextBlock" xlink:to="us-gaap_LeaseCostTableTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeaseExpirationDate1" xlink:label="us-gaap_LeaseExpirationDate1"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LeaseExpirationDate1_lbl" xml:lang="en-US" id="id_13073811_3073339_1_1">Lease Expiration Date</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LeaseExpirationDate1_lbl" xml:lang="en-US" id="id_13073811_3073339_2_1">Lease expiration date</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeaseExpirationDate1" xlink:to="us-gaap_LeaseExpirationDate1_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeaseholdImprovementsMember" xlink:label="us-gaap_LeaseholdImprovementsMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LeaseholdImprovementsMember_lbl" xml:lang="en-US" id="id_13073811_3073567_1_1">Leasehold Improvements [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LeaseholdImprovementsMember_lbl" xml:lang="en-US" id="id_13073811_3073567_2_1">Leasehold Improvements [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeaseholdImprovementsMember" xlink:to="us-gaap_LeaseholdImprovementsMember_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeasesAbstract" xlink:label="us-gaap_LeasesAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LeasesAbstract_lbl" xml:lang="en-US" id="id_13073811_3073569_1_1">Leases [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LeasesAbstract_lbl" xml:lang="en-US" id="id_13073811_3073569_2_1">Leases [Abstract]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeasesAbstract" xlink:to="us-gaap_LeasesAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeasesOfLesseeDisclosureTextBlock" xlink:label="us-gaap_LeasesOfLesseeDisclosureTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LeasesOfLesseeDisclosureTextBlock_lbl" xml:lang="en-US" id="id_13073811_3073134_1_1">Leases of Lessee Disclosure [Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LeasesOfLesseeDisclosureTextBlock_lbl" xml:lang="en-US" id="id_13073811_3073134_2_1">Leases</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeasesOfLesseeDisclosureTextBlock" xlink:to="us-gaap_LeasesOfLesseeDisclosureTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeLeaseDescriptionLineItems" xlink:label="us-gaap_LesseeLeaseDescriptionLineItems"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeLeaseDescriptionLineItems_lbl" xml:lang="en-US" id="id_13073811_3073588_1_1">Lessee, Lease, Description [Line Items]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeLeaseDescriptionLineItems_lbl" xml:lang="en-US" id="id_13073811_3073588_2_1">Lessee, Lease, Description [Line Items]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeLeaseDescriptionLineItems" xlink:to="us-gaap_LesseeLeaseDescriptionLineItems_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeLeaseDescriptionTable" xlink:label="us-gaap_LesseeLeaseDescriptionTable"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeLeaseDescriptionTable_lbl" xml:lang="en-US" id="id_13073811_3072853_1_1">Lessee, Lease, Description [Table]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeLeaseDescriptionTable_lbl" xml:lang="en-US" id="id_13073811_3072853_2_1">Lessee, Lease, Description [Table]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeLeaseDescriptionTable" xlink:to="us-gaap_LesseeLeaseDescriptionTable_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock_lbl" xml:lang="en-US" id="id_13073811_3072857_1_1">Lessee, Operating Lease, Liability, Maturity [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock_lbl" xml:lang="en-US" id="id_13073811_3072857_2_1">Schedule of Maturities of Lease Liabilities</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xml:lang="en-US" id="id_13073811_3073599_1_1">Lessee, Operating Lease, Liability, Payments, Due</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xml:lang="en-US" id="id_13073811_3073599_2_1">Total lease payments</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_lbl" xml:lang="en-US" id="id_13073811_3073600_1_1">Lessee, Operating Lease, Liability, Payments, Due after Year Five</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_lbl" xml:lang="en-US" id="id_13073811_3073600_2_1">Thereafter</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_lbl" xml:lang="en-US" id="id_13073811_3073602_1_1">Lessee, Operating Lease, Liability, Payments, Due Year Five</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_lbl" xml:lang="en-US" id="id_13073811_3073602_2_1">2023</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_lbl" xml:lang="en-US" id="id_13073811_3073372_1_1">Lessee, Operating Lease, Liability, Payments, Due Year Four</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_lbl" xml:lang="en-US" id="id_13073811_3073372_2_1">2022</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl" xml:lang="en-US" id="id_13073811_3072858_1_1">Lessee, Operating Lease, Liability, Payments, Due Year Three</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl" xml:lang="en-US" id="id_13073811_3072858_2_1">2021</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" xml:lang="en-US" id="id_13073811_3073373_1_1">Lessee, Operating Lease, Liability, Payments, Due Year Two</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" xml:lang="en-US" id="id_13073811_3073373_2_1">2020</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_lbl" xml:lang="en-US" id="id_13073811_3073374_1_1">Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_lbl" xml:lang="en-US" id="id_13073811_3073374_2_1">2019 (remainder of 2019)</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xml:lang="en-US" id="id_13073811_3073375_1_1">Lessee, Operating Lease, Liability, Undiscounted Excess Amount</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xml:lang="en-US" id="id_13073811_3073375_14_1">Less: interest</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeOperatingLeaseRenewalTerm" xlink:label="us-gaap_LesseeOperatingLeaseRenewalTerm"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseRenewalTerm_lbl" xml:lang="en-US" id="id_13073811_3072859_1_1">Lessee, Operating Lease, Renewal Term</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseRenewalTerm_lbl" xml:lang="en-US" id="id_13073811_3072859_2_1">Lease, renewal term of contract</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseRenewalTerm" xlink:to="us-gaap_LesseeOperatingLeaseRenewalTerm_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeOperatingLeaseTermOfContract" xlink:label="us-gaap_LesseeOperatingLeaseTermOfContract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseTermOfContract_lbl" xml:lang="en-US" id="id_13073811_3073159_1_1">Lessee, Operating Lease, Term of Contract</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseTermOfContract_lbl" xml:lang="en-US" id="id_13073811_3073159_2_1">Lease, term of contract</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseTermOfContract" xlink:to="us-gaap_LesseeOperatingLeaseTermOfContract_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LetterOfCreditMember" xlink:label="us-gaap_LetterOfCreditMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LetterOfCreditMember_lbl" xml:lang="en-US" id="id_13073811_3073193_1_1">Letter of Credit [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LetterOfCreditMember_lbl" xml:lang="en-US" id="id_13073811_3073193_2_1">Letter of Credit [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LetterOfCreditMember" xlink:to="us-gaap_LetterOfCreditMember_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_Liabilities" xlink:label="us-gaap_Liabilities"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_Liabilities_lbl" xml:lang="en-US" id="id_13073811_3073419_1_1">Liabilities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_Liabilities_lbl" xml:lang="en-US" id="id_13073811_3073419_6_1">Total liabilities</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Liabilities" xlink:to="us-gaap_Liabilities_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xml:lang="en-US" id="id_13073811_3073420_1_1">Liabilities and Equity</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xml:lang="en-US" id="id_13073811_3073420_6_1">Total liabilities, convertible preferred stock, redeemable common stock and stockholders' equity (deficit)</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="us-gaap_LiabilitiesAndStockholdersEquity_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xml:lang="en-US" id="id_13073811_3073204_1_1">Liabilities and Equity [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xml:lang="en-US" id="id_13073811_3073204_2_1">Liabilities, Convertible Preferred Stock, Redeemable Common Stock and Stockholders' Equity (Deficit)</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="us-gaap_LiabilitiesCurrent"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xml:lang="en-US" id="id_13073811_3072894_1_1">Liabilities, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xml:lang="en-US" id="id_13073811_3072894_6_1">Total current liabilities</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesCurrent" xlink:to="us-gaap_LiabilitiesCurrent_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract" xlink:label="us-gaap_LiabilitiesCurrentAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xml:lang="en-US" id="id_13073811_3073422_1_1">Liabilities, Current [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xml:lang="en-US" id="id_13073811_3073422_2_1">Current liabilities:</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_LiabilitiesCurrentAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LiabilitiesFairValueDisclosure" xlink:label="us-gaap_LiabilitiesFairValueDisclosure"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LiabilitiesFairValueDisclosure_lbl" xml:lang="en-US" id="id_13073811_3072895_1_1">Financial and Nonfinancial Liabilities, Fair Value Disclosure</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LiabilitiesFairValueDisclosure_lbl" xml:lang="en-US" id="id_13073811_3072895_2_1">Derivative liability</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_LiabilitiesFairValueDisclosure_lbl" xml:lang="en-US" id="id_13073811_3072895_12_1">Total</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesFairValueDisclosure" xlink:to="us-gaap_LiabilitiesFairValueDisclosure_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_LicenseAgreementTerminationDescription" xlink:label="xfor_LicenseAgreementTerminationDescription"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_LicenseAgreementTerminationDescription_lbl" xml:lang="en-US" id="id_13073811_3211662_3_1">License Agreement, Termination Description</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_LicenseAgreementTerminationDescription_lbl" xml:lang="en-US" id="id_13073811_3211662_1_1">License Agreement, Termination Description</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_LicenseAgreementTerminationDescription_lbl" xml:lang="en-US" id="id_13073811_3211662_2_1">License agreement termination description</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_LicenseAgreementTerminationDescription" xlink:to="xfor_LicenseAgreementTerminationDescription_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LineOfCreditFacilityExpirationDate1" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1_lbl" xml:lang="en-US" id="id_13073811_3074401_1_1">Line of Credit Facility, Expiration Date</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1_lbl" xml:lang="en-US" id="id_13073811_3074401_2_1">Line of credit facility, expiration date</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityExpirationDate1" xlink:to="us-gaap_LineOfCreditFacilityExpirationDate1_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LineOfCreditFacilityInterestRateDescription" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDescription"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDescription_lbl" xml:lang="en-US" id="id_13073811_3072972_1_1">Line of Credit Facility, Interest Rate Description</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDescription_lbl" xml:lang="en-US" id="id_13073811_3072972_2_1">Line of credit interest rate, Description</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityInterestRateDescription" xlink:to="us-gaap_LineOfCreditFacilityInterestRateDescription_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LineOfCreditFacilityInterestRateDuringPeriod" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_lbl" xml:lang="en-US" id="id_13073811_3072973_1_1">Line of Credit Facility, Interest Rate During Period</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_lbl" xml:lang="en-US" id="id_13073811_3072973_2_1">Line of credit facility interest rate</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod" xlink:to="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xml:lang="en-US" id="id_13073811_3074404_1_1">Line of Credit Facility, Maximum Borrowing Capacity</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xml:lang="en-US" id="id_13073811_3074404_2_1">Line of credit facility, maximum borrowing capacity</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xml:lang="en-US" id="id_13073811_3074404_12_1">Maximum term loan borrowing capacity</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:to="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LineOfCreditFacilityPeriodicPaymentInterest" xlink:label="us-gaap_LineOfCreditFacilityPeriodicPaymentInterest"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LineOfCreditFacilityPeriodicPaymentInterest_lbl" xml:lang="en-US" id="id_13073811_3074178_1_1">Line of Credit Facility, Periodic Payment, Interest</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LineOfCreditFacilityPeriodicPaymentInterest_lbl" xml:lang="en-US" id="id_13073811_3074178_2_1">Line of credit facility, periodic payment, interest</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityPeriodicPaymentInterest" xlink:to="us-gaap_LineOfCreditFacilityPeriodicPaymentInterest_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebt" xlink:label="us-gaap_LongTermDebt"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LongTermDebt_lbl" xml:lang="en-US" id="id_13073811_3073715_1_1">Long-term Debt</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LongTermDebt_lbl" xml:lang="en-US" id="id_13073811_3073715_2_1">Debt instrument, outstanding value</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_LongTermDebt_lbl" xml:lang="en-US" id="id_13073811_3073715_6_1">Long-term debt</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_LongTermDebt_lbl" xml:lang="en-US" id="id_13073811_3073715_12_1">Principal amount of long-term debt</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebt" xlink:to="us-gaap_LongTermDebt_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtAbstract" xlink:label="us-gaap_LongTermDebtAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LongTermDebtAbstract_lbl" xml:lang="en-US" id="id_13073811_3073716_1_1">Long-term Debt, Unclassified [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LongTermDebtAbstract_lbl" xml:lang="en-US" id="id_13073811_3073716_2_1">Long-term Debt, Unclassified [Abstract]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtAbstract" xlink:to="us-gaap_LongTermDebtAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtByMaturityAbstract" xlink:label="us-gaap_LongTermDebtByMaturityAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LongTermDebtByMaturityAbstract_lbl" xml:lang="en-US" id="id_13073811_3074487_1_1">Long-term Debt, Fiscal Year Maturity [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LongTermDebtByMaturityAbstract_lbl" xml:lang="en-US" id="id_13073811_3074487_2_1">Long-term Debt, Fiscal Year Maturity [Abstract]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtByMaturityAbstract" xlink:to="us-gaap_LongTermDebtByMaturityAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_LongTermDebtByMaturityTable" xlink:label="xfor_LongTermDebtByMaturityTable"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_LongTermDebtByMaturityTable_lbl" xml:lang="en-US" id="id_13073811_3238693_3_1">Long Term Debt By Maturity [Table]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_LongTermDebtByMaturityTable_lbl" xml:lang="en-US" id="id_13073811_3238693_1_1">Long Term Debt By Maturity [Table]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_LongTermDebtByMaturityTable_lbl" xml:lang="en-US" id="id_13073811_3238693_2_1">Long Term Debt By Maturity [Table]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_LongTermDebtByMaturityTable" xlink:to="xfor_LongTermDebtByMaturityTable_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtCurrent" xlink:label="us-gaap_LongTermDebtCurrent"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LongTermDebtCurrent_lbl" xml:lang="en-US" id="id_13073811_3073724_1_1">Long-term Debt, Current Maturities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LongTermDebtCurrent_lbl" xml:lang="en-US" id="id_13073811_3073724_2_1">Current portion of long-term debt</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_LongTermDebtCurrent_lbl" xml:lang="en-US" id="id_13073811_3073724_12_1">Debt instrument, current portion</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_LongTermDebtCurrent_lbl" xml:lang="en-US" id="id_13073811_3073724_14_1">Less: Current portion of long-term debt</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtCurrent" xlink:to="us-gaap_LongTermDebtCurrent_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_lbl" xml:lang="en-US" id="id_13073811_3073733_1_1">Long-term Debt, Maturities, Repayments of Principal in Year Three</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_lbl" xml:lang="en-US" id="id_13073811_3073733_2_1">2021</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree" xlink:to="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_lbl" xml:lang="en-US" id="id_13073811_3074062_1_1">Long-term Debt, Maturities, Repayments of Principal in Year Two</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_lbl" xml:lang="en-US" id="id_13073811_3074062_2_1">2020</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" xlink:to="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_lbl" xml:lang="en-US" id="id_13073811_3074063_1_1">Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_lbl" xml:lang="en-US" id="id_13073811_3074063_2_1">2019</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear" xlink:to="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtNoncurrent" xlink:label="us-gaap_LongTermDebtNoncurrent"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LongTermDebtNoncurrent_lbl" xml:lang="en-US" id="id_13073811_3074496_1_1">Long-term Debt, Excluding Current Maturities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_LongTermDebtNoncurrent_lbl" xml:lang="en-US" id="id_13073811_3074496_6_1">Long-term debt, net of current portion</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtNoncurrent" xlink:to="us-gaap_LongTermDebtNoncurrent_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_LongTermDebtNonCurrentIncludingAccretion" xlink:label="xfor_LongTermDebtNonCurrentIncludingAccretion"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_LongTermDebtNonCurrentIncludingAccretion_lbl" xml:lang="en-US" id="id_13073811_3566706_3_1">Long term debt non current including accretion.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_LongTermDebtNonCurrentIncludingAccretion_lbl" xml:lang="en-US" id="id_13073811_3566706_1_1">Long Term Debt Non Current Including Accretion</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_LongTermDebtNonCurrentIncludingAccretion_lbl" xml:lang="en-US" id="id_13073811_3566706_2_1">Long-term debt, including accretion, net of current portion</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="xfor_LongTermDebtNonCurrentIncludingAccretion_lbl" xml:lang="en-US" id="id_13073811_3566706_12_1">Long-term debt, including accretion, net of discount and current portion</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_LongTermDebtNonCurrentIncludingAccretion" xlink:to="xfor_LongTermDebtNonCurrentIncludingAccretion_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtTextBlock" xlink:label="us-gaap_LongTermDebtTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LongTermDebtTextBlock_lbl" xml:lang="en-US" id="id_13073811_3074277_1_1">Long-term Debt [Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LongTermDebtTextBlock_lbl" xml:lang="en-US" id="id_13073811_3074277_2_1">Long-Term Debt</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtTextBlock" xlink:to="us-gaap_LongTermDebtTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_MaximumFundingCommitmentAmount" xlink:label="xfor_MaximumFundingCommitmentAmount"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_MaximumFundingCommitmentAmount_lbl" xml:lang="en-US" id="id_13073811_3566707_3_1">Maximum funding commitment amount.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_MaximumFundingCommitmentAmount_lbl" xml:lang="en-US" id="id_13073811_3566707_1_1">Maximum Funding Commitment Amount</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_MaximumFundingCommitmentAmount_lbl" xml:lang="en-US" id="id_13073811_3566707_2_1">Purchase commitment, amount</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_MaximumFundingCommitmentAmount" xlink:to="xfor_MaximumFundingCommitmentAmount_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_MaximumMember_lbl" xml:lang="en-US" id="id_13073811_3074821_1_1">Maximum [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="srt_MaximumMember_lbl" xml:lang="en-US" id="id_13073811_3074821_2_1">Maximum [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MaximumMember" xlink:to="srt_MaximumMember_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputExpectedDividendRateMember" xlink:label="us-gaap_MeasurementInputExpectedDividendRateMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_MeasurementInputExpectedDividendRateMember_lbl" xml:lang="en-US" id="id_13073811_3075256_1_1">Measurement Input, Expected Dividend Rate [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_MeasurementInputExpectedDividendRateMember_lbl" xml:lang="en-US" id="id_13073811_3075256_2_1">Measurement Input, Expected Dividend Rate [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MeasurementInputExpectedDividendRateMember" xlink:to="us-gaap_MeasurementInputExpectedDividendRateMember_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputTypeAxis" xlink:label="us-gaap_MeasurementInputTypeAxis"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_MeasurementInputTypeAxis_lbl" xml:lang="en-US" id="id_13073811_3075027_1_1">Measurement Input Type [Axis]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_MeasurementInputTypeAxis_lbl" xml:lang="en-US" id="id_13073811_3075027_2_1">Measurement Input Type [Axis]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MeasurementInputTypeAxis" xlink:to="us-gaap_MeasurementInputTypeAxis_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="us-gaap_MeasurementInputTypeDomain"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_MeasurementInputTypeDomain_lbl" xml:lang="en-US" id="id_13073811_3075259_1_1">Measurement Input Type [Domain]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_MeasurementInputTypeDomain_lbl" xml:lang="en-US" id="id_13073811_3075259_2_1">Measurement Input Type [Domain]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MeasurementInputTypeDomain" xlink:to="us-gaap_MeasurementInputTypeDomain_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_MilestonePaymentObligation" xlink:label="xfor_MilestonePaymentObligation"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_MilestonePaymentObligation_lbl" xml:lang="en-US" id="id_13073811_3101653_3_1">Milestone Payment Obligation</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_MilestonePaymentObligation_lbl" xml:lang="en-US" id="id_13073811_3101653_1_1">Milestone Payment Obligation</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_MilestonePaymentObligation_lbl" xml:lang="en-US" id="id_13073811_3101653_2_1">Milestone payment obligation</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_MilestonePaymentObligation" xlink:to="xfor_MilestonePaymentObligation_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_MilestonePayments" xlink:label="xfor_MilestonePayments"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_MilestonePayments_lbl" xml:lang="en-US" id="id_13073811_3096602_3_1">Milestone payments.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_MilestonePayments_lbl" xml:lang="en-US" id="id_13073811_3096602_1_1">Milestone Payments</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_MilestonePayments_lbl" xml:lang="en-US" id="id_13073811_3096602_2_1">Future milestone payments</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="xfor_MilestonePayments_lbl" xml:lang="en-US" id="id_13073811_3096602_12_1">Milestone payments</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_MilestonePayments" xlink:to="xfor_MilestonePayments_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_MilestonePaymentsPaid" xlink:label="xfor_MilestonePaymentsPaid"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_MilestonePaymentsPaid_lbl" xml:lang="en-US" id="id_13073811_3176452_3_1">Milestone Payments Paid</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_MilestonePaymentsPaid_lbl" xml:lang="en-US" id="id_13073811_3176452_1_1">Milestone Payments Paid</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_MilestonePaymentsPaid_lbl" xml:lang="en-US" id="id_13073811_3176452_2_1">Milestone payments</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_MinimumMember" xlink:label="srt_MinimumMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_MinimumMember_lbl" xml:lang="en-US" id="id_13073811_3075282_1_1">Minimum [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="srt_MinimumMember_lbl" xml:lang="en-US" id="id_13073811_3075282_2_1">Minimum [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MinimumMember" xlink:to="srt_MinimumMember_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MoneyMarketFundsMember" xlink:label="us-gaap_MoneyMarketFundsMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_MoneyMarketFundsMember_lbl" xml:lang="en-US" id="id_13073811_3075297_1_1">Money Market Funds [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_MoneyMarketFundsMember_lbl" xml:lang="en-US" id="id_13073811_3075297_2_1">Money Market Funds [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MoneyMarketFundsMember" xlink:to="us-gaap_MoneyMarketFundsMember_lbl"/>
    <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/exch/2018/exch-2018-01-31.xsd#exch_MTSA" xlink:label="exch_MTSA"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="exch_MTSA_lbl" xml:lang="en-US" id="id_13073811_3074558_1_1">MTS AUSTRIA [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="exch_MTSA_lbl" xml:lang="en-US" id="id_13073811_3074558_2_1">AUSTRIA [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="exch_MTSA" xlink:to="exch_MTSA_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xml:lang="en-US" id="id_13073811_3075138_1_1">Net Cash Provided by (Used in) Financing Activities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xml:lang="en-US" id="id_13073811_3075138_6_1">Net cash provided by (used in) financing activities</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xml:lang="en-US" id="id_13073811_3075384_1_1">Net Cash Provided by (Used in) Financing Activities [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xml:lang="en-US" id="id_13073811_3075384_2_1">Cash flows from financing activities:</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xml:lang="en-US" id="id_13073811_3074968_1_1">Net Cash Provided by (Used in) Investing Activities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xml:lang="en-US" id="id_13073811_3074968_2_1">Net cash provided by investing activities</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xml:lang="en-US" id="id_13073811_3075386_1_1">Net Cash Provided by (Used in) Investing Activities [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xml:lang="en-US" id="id_13073811_3075386_2_1">Cash flows from investing activities:</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xml:lang="en-US" id="id_13073811_3075387_1_1">Net Cash Provided by (Used in) Operating Activities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xml:lang="en-US" id="id_13073811_3075387_6_1">Net cash used in operating activities</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xml:lang="en-US" id="id_13073811_3074970_1_1">Net Cash Provided by (Used in) Operating Activities [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xml:lang="en-US" id="id_13073811_3074970_2_1">Cash flows from operating activities:</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="us-gaap_NetIncomeLoss"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetIncomeLoss_lbl" xml:lang="en-US" id="id_13073811_3075391_1_1">Net Income (Loss) Attributable to Parent</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_NetIncomeLoss_lbl" xml:lang="en-US" id="id_13073811_3075391_2_1">Net loss</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_NetIncomeLoss_lbl" xml:lang="en-US" id="id_13073811_3075391_6_1">Net loss</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetIncomeLoss" xlink:to="us-gaap_NetIncomeLoss_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic" xlink:label="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_lbl" xml:lang="en-US" id="id_13073811_3074619_1_1">Net Income (Loss) Available to Common Stockholders, Basic</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_lbl" xml:lang="en-US" id="id_13073811_3074619_6_1">Net loss attributable to common stockholders</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic" xlink:to="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_NetProceedsFromIssuanceOfCommonStockAndWarrants" xlink:label="xfor_NetProceedsFromIssuanceOfCommonStockAndWarrants"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_NetProceedsFromIssuanceOfCommonStockAndWarrants_lbl" xml:lang="en-US" id="id_13073811_3195943_3_1">Net Proceeds From Issuance Of Common Stock And Warrants</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_NetProceedsFromIssuanceOfCommonStockAndWarrants_lbl" xml:lang="en-US" id="id_13073811_3195943_1_1">Net Proceeds From Issuance Of Common Stock And Warrants</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_NetProceedsFromIssuanceOfCommonStockAndWarrants_lbl" xml:lang="en-US" id="id_13073811_3195943_2_1">Net proceeds from sale of common stock and pre-funded warrants</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_NetProceedsFromIssuanceOfCommonStockAndWarrants" xlink:to="xfor_NetProceedsFromIssuanceOfCommonStockAndWarrants_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3074638_1_1">New Accounting Pronouncements, Policy [Policy Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3074638_2_1">Recently Adopted Accounting Pronouncements</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:to="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_NonCashInterestExpense" xlink:label="xfor_NonCashInterestExpense"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_NonCashInterestExpense_lbl" xml:lang="en-US" id="id_13073811_3160103_3_1">Non-cash interest expense.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_NonCashInterestExpense_lbl" xml:lang="en-US" id="id_13073811_3160103_1_1">Non Cash Interest Expense</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_NonCashInterestExpense_lbl" xml:lang="en-US" id="id_13073811_3160103_2_1">Non-cash interest expense</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_NonCashInterestExpense" xlink:to="xfor_NonCashInterestExpense_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_NonCashLeaseExpense" xlink:label="xfor_NonCashLeaseExpense"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_NonCashLeaseExpense_lbl" xml:lang="en-US" id="id_13073811_3104388_3_1">Non-cash lease expense.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_NonCashLeaseExpense_lbl" xml:lang="en-US" id="id_13073811_3104388_1_1">Non Cash Lease Expense</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_NonCashLeaseExpense_lbl" xml:lang="en-US" id="id_13073811_3104388_2_1">Non-cash lease expense</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_NonCashLeaseExpense" xlink:to="xfor_NonCashLeaseExpense_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="us-gaap_NonoperatingIncomeExpense"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NonoperatingIncomeExpense_lbl" xml:lang="en-US" id="id_13073811_3074676_1_1">Nonoperating Income (Expense)</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_NonoperatingIncomeExpense_lbl" xml:lang="en-US" id="id_13073811_3074676_6_1">Total other income (expense), net</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NonoperatingIncomeExpense" xlink:to="us-gaap_NonoperatingIncomeExpense_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NonoperatingIncomeExpenseAbstract" xlink:label="us-gaap_NonoperatingIncomeExpenseAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NonoperatingIncomeExpenseAbstract_lbl" xml:lang="en-US" id="id_13073811_3074677_1_1">Nonoperating Income (Expense) [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_NonoperatingIncomeExpenseAbstract_lbl" xml:lang="en-US" id="id_13073811_3074677_2_1">Other income (expense):</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NonoperatingIncomeExpenseAbstract" xlink:to="us-gaap_NonoperatingIncomeExpenseAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_NumberOfCommonStockSharesIssuableUponConversion" xlink:label="xfor_NumberOfCommonStockSharesIssuableUponConversion"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_NumberOfCommonStockSharesIssuableUponConversion_lbl" xml:lang="en-US" id="id_13073811_3534839_3_1">Number of Common Stock Shares Issuable Upon Conversion</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_NumberOfCommonStockSharesIssuableUponConversion_lbl" xml:lang="en-US" id="id_13073811_3534839_1_1">Number of Common Stock Shares Issuable Upon Conversion</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_NumberOfCommonStockSharesIssuableUponConversion_lbl" xml:lang="en-US" id="id_13073811_3534839_2_1">Common Stock Issuable Upon Conversion</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_NumberOfCommonStockSharesIssuableUponConversion" xlink:to="xfor_NumberOfCommonStockSharesIssuableUponConversion_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_NumberOfDirectorsEntitledToBeElected" xlink:label="xfor_NumberOfDirectorsEntitledToBeElected"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_NumberOfDirectorsEntitledToBeElected_lbl" xml:lang="en-US" id="id_13073811_3219240_3_1">Number of directors entitled to be elected.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_NumberOfDirectorsEntitledToBeElected_lbl" xml:lang="en-US" id="id_13073811_3219240_1_1">Number of Directors Entitled To Be Elected</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_NumberOfDirectorsEntitledToBeElected_lbl" xml:lang="en-US" id="id_13073811_3219240_2_1">Number of directors entitled to be elected</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_NumberOfDirectorsEntitledToBeElected" xlink:to="xfor_NumberOfDirectorsEntitledToBeElected_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_NumberOfYearsAcceleratedPaymentTerm" xlink:label="xfor_NumberOfYearsAcceleratedPaymentTerm"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_NumberOfYearsAcceleratedPaymentTerm_lbl" xml:lang="en-US" id="id_13073811_3566595_3_1">Number Of Years Accelerated Payment Term</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_NumberOfYearsAcceleratedPaymentTerm_lbl" xml:lang="en-US" id="id_13073811_3566595_1_1">Number Of Years Accelerated Payment Term</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_NumberOfYearsAcceleratedPaymentTerm_lbl" xml:lang="en-US" id="id_13073811_3566595_2_1">Number of years accelerated payment</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_NumberOfYearsAcceleratedPaymentTerm" xlink:to="xfor_NumberOfYearsAcceleratedPaymentTerm_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_OfficeLeasesMember" xlink:label="xfor_OfficeLeasesMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_OfficeLeasesMember_lbl" xml:lang="en-US" id="id_13073811_3286661_3_1">Company's office leases.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_OfficeLeasesMember_lbl" xml:lang="en-US" id="id_13073811_3286661_1_1">Office Leases [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_OfficeLeasesMember_lbl" xml:lang="en-US" id="id_13073811_3286661_2_1">Company's Office Leases</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_OfficeLeasesMember" xlink:to="xfor_OfficeLeasesMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_OneTimeUpfrontPayment" xlink:label="xfor_OneTimeUpfrontPayment"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_OneTimeUpfrontPayment_lbl" xml:lang="en-US" id="id_13073811_3145920_3_1">One Time Upfront Payment</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_OneTimeUpfrontPayment_lbl" xml:lang="en-US" id="id_13073811_3145920_1_1">One Time Upfront Payment</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_OneTimeUpfrontPayment_lbl" xml:lang="en-US" id="id_13073811_3145920_2_1">One time upfront payment</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_OneTimeUpfrontPayment" xlink:to="xfor_OneTimeUpfrontPayment_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingCashFlowsDirectMethodAbstract" xlink:label="us-gaap_OperatingCashFlowsDirectMethodAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingCashFlowsDirectMethodAbstract_lbl" xml:lang="en-US" id="id_13073811_3076163_1_1">Operating Cash Flows, Direct Method [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OperatingCashFlowsDirectMethodAbstract_lbl" xml:lang="en-US" id="id_13073811_3076163_2_1">Operating Cash Flows, Direct Method [Abstract]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingCashFlowsDirectMethodAbstract" xlink:to="us-gaap_OperatingCashFlowsDirectMethodAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingExpenses" xlink:label="us-gaap_OperatingExpenses"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingExpenses_lbl" xml:lang="en-US" id="id_13073811_3075924_1_1">Operating Expenses</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_OperatingExpenses_lbl" xml:lang="en-US" id="id_13073811_3075924_6_1">Total operating expenses</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_OperatingExpenses_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingExpensesAbstract" xlink:label="us-gaap_OperatingExpensesAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xml:lang="en-US" id="id_13073811_3075761_1_1">Operating Expenses [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xml:lang="en-US" id="id_13073811_3075761_2_1">Operating expenses:</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_OperatingExpensesAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="us-gaap_OperatingIncomeLoss"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xml:lang="en-US" id="id_13073811_3076165_1_1">Operating Income (Loss)</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xml:lang="en-US" id="id_13073811_3076165_2_1">Loss from operations</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingIncomeLoss" xlink:to="us-gaap_OperatingIncomeLoss_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeaseCost" xlink:label="us-gaap_OperatingLeaseCost"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseCost_lbl" xml:lang="en-US" id="id_13073811_3075926_1_1">Operating Lease, Cost</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OperatingLeaseCost_lbl" xml:lang="en-US" id="id_13073811_3075926_2_1">Fixed operating lease cost</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseCost" xlink:to="us-gaap_OperatingLeaseCost_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_OperatingLeaseExpiration" xlink:label="xfor_OperatingLeaseExpiration"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_OperatingLeaseExpiration_lbl" xml:lang="en-US" id="id_13073811_3567019_3_1">Operating lease expiration.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_OperatingLeaseExpiration_lbl" xml:lang="en-US" id="id_13073811_3567019_1_1">Operating Lease Expiration</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_OperatingLeaseExpiration_lbl" xml:lang="en-US" id="id_13073811_3567019_2_1">Operating lease expiration</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_OperatingLeaseExpiration" xlink:to="xfor_OperatingLeaseExpiration_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeaseLiability" xlink:label="us-gaap_OperatingLeaseLiability"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xml:lang="en-US" id="id_13073811_3075763_1_1">Operating Lease, Liability</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xml:lang="en-US" id="id_13073811_3075763_2_1">Operating lease liabilities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xml:lang="en-US" id="id_13073811_3075763_12_1">Total operating lease liabilities as of March 31, 2019</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiability" xlink:to="us-gaap_OperatingLeaseLiability_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeaseLiabilityCurrent" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xml:lang="en-US" id="id_13073811_3075929_1_1">Operating Lease, Liability, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xml:lang="en-US" id="id_13073811_3075929_2_1">Current portion of lease liability</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiabilityCurrent" xlink:to="us-gaap_OperatingLeaseLiabilityCurrent_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xml:lang="en-US" id="id_13073811_3075930_1_1">Operating Lease, Liability, Noncurrent</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xml:lang="en-US" id="id_13073811_3075930_2_1">Lease liability</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xml:lang="en-US" id="id_13073811_3075930_12_1">Lease liability, net of current portion</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiabilityNoncurrent" xlink:to="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasePayments" xlink:label="us-gaap_OperatingLeasePayments"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeasePayments_lbl" xml:lang="en-US" id="id_13073811_3076172_1_1">Operating Lease, Payments</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OperatingLeasePayments_lbl" xml:lang="en-US" id="id_13073811_3076172_2_1">Operating cash flows from operating leases</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasePayments" xlink:to="us-gaap_OperatingLeasePayments_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xml:lang="en-US" id="id_13073811_3075931_1_1">Operating Lease, Right-of-Use Asset</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xml:lang="en-US" id="id_13073811_3075931_2_1">Right-of-use assets</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseRightOfUseAsset" xlink:to="us-gaap_OperatingLeaseRightOfUseAsset_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDue" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDue"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDue_lbl" xml:lang="en-US" id="id_13073811_3075932_1_1">Operating Leases, Future Minimum Payments Due</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDue_lbl" xml:lang="en-US" id="id_13073811_3075932_6_1">Total</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsDue" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDue_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_lbl" xml:lang="en-US" id="id_13073811_3076176_1_1">Operating Leases, Future Minimum Payments, Due in Four Years</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_lbl" xml:lang="en-US" id="id_13073811_3076176_2_1">2022</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_lbl" xml:lang="en-US" id="id_13073811_3075775_1_1">Operating Leases, Future Minimum Payments, Due in Three Years</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_lbl" xml:lang="en-US" id="id_13073811_3075775_2_1">2021</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_lbl" xml:lang="en-US" id="id_13073811_3075935_1_1">Operating Leases, Future Minimum Payments, Due in Two Years</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_lbl" xml:lang="en-US" id="id_13073811_3075935_2_1">2020</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear_lbl" xml:lang="en-US" id="id_13073811_3076183_1_1">Operating Leases, Future Minimum Payments, Remainder of Fiscal Year</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear_lbl" xml:lang="en-US" id="id_13073811_3076183_2_1">2019</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl" xml:lang="en-US" id="id_13073811_3076188_1_1">Operating Lease, Weighted Average Discount Rate, Percent</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl" xml:lang="en-US" id="id_13073811_3076188_2_1">Weighted-average discount rate-operating leases</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent" xlink:to="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl" xml:lang="en-US" id="id_13073811_3074760_1_1">Operating Lease, Weighted Average Remaining Lease Term</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl" xml:lang="en-US" id="id_13073811_3074760_2_1">Weighted-average remaining lease term-operating leases</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1" xlink:to="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_OptionFee" xlink:label="xfor_OptionFee"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_OptionFee_lbl" xml:lang="en-US" id="id_13073811_3117833_3_1">Option fee.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_OptionFee_lbl" xml:lang="en-US" id="id_13073811_3117833_1_1">Option Fee</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_OptionFee_lbl" xml:lang="en-US" id="id_13073811_3117833_2_1">Option fee</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_OptionFee" xlink:to="xfor_OptionFee_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_lbl" xml:lang="en-US" id="id_13073811_3075797_1_1">Organization, Consolidation and Presentation of Financial Statements [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_lbl" xml:lang="en-US" id="id_13073811_3075797_2_1">Organization, Consolidation and Presentation of Financial Statements [Abstract]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract" xlink:to="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherAccruedLiabilitiesCurrent" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent_lbl" xml:lang="en-US" id="id_13073811_3075431_1_1">Other Accrued Liabilities, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent_lbl" xml:lang="en-US" id="id_13073811_3075431_2_1">Other</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherAccruedLiabilitiesCurrent" xlink:to="us-gaap_OtherAccruedLiabilitiesCurrent_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OtherLiabilitiesNoncurrent_lbl" xml:lang="en-US" id="id_13073811_3076709_1_1">Other Liabilities, Noncurrent</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_OwnershipAxis" xlink:label="srt_OwnershipAxis"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_OwnershipAxis_lbl" xml:lang="en-US" id="id_13073811_3075605_1_1">Ownership [Axis]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="srt_OwnershipAxis_lbl" xml:lang="en-US" id="id_13073811_3075605_2_1">Ownership [Axis]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_OwnershipAxis" xlink:to="srt_OwnershipAxis_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_OwnershipDomain_lbl" xml:lang="en-US" id="id_13073811_3075606_1_1">Ownership [Domain]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="srt_OwnershipDomain_lbl" xml:lang="en-US" id="id_13073811_3075606_2_1">Ownership [Domain]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_OwnershipDomain" xlink:to="srt_OwnershipDomain_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PatentsMember" xlink:label="us-gaap_PatentsMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PatentsMember_lbl" xml:lang="en-US" id="id_13073811_3076643_1_1">Patents [Member]</label>
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    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PatentsMember" xlink:to="us-gaap_PatentsMember_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PayablesAndAccrualsAbstract_lbl" xml:lang="en-US" id="id_13073811_3076645_1_1">Payables and Accruals [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PayablesAndAccrualsAbstract_lbl" xml:lang="en-US" id="id_13073811_3076645_2_1">Payables and Accruals [Abstract]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PayablesAndAccrualsAbstract" xlink:to="us-gaap_PayablesAndAccrualsAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_PaymentOnObligationUnderLicenseAgreement" xlink:label="xfor_PaymentOnObligationUnderLicenseAgreement"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_PaymentOnObligationUnderLicenseAgreement_lbl" xml:lang="en-US" id="id_13073811_3106238_3_1">Payment On Obligation Under License Agreement</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_PaymentOnObligationUnderLicenseAgreement_lbl" xml:lang="en-US" id="id_13073811_3106238_1_1">Payment On Obligation Under License Agreement</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_PaymentOnObligationUnderLicenseAgreement_lbl" xml:lang="en-US" id="id_13073811_3106238_2_1">Payment on obligation under license agreement</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_PaymentOnObligationUnderLicenseAgreement" xlink:to="xfor_PaymentOnObligationUnderLicenseAgreement_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PaymentsForRepurchaseOfConvertiblePreferredStock" xlink:label="us-gaap_PaymentsForRepurchaseOfConvertiblePreferredStock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PaymentsForRepurchaseOfConvertiblePreferredStock_lbl" xml:lang="en-US" id="id_13073811_3077071_1_1">Payments for Repurchase of Convertible Preferred Stock</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_PaymentsForRepurchaseOfConvertiblePreferredStock_lbl" xml:lang="en-US" id="id_13073811_3077071_14_1">Repurchase of Series Seed convertible preferred stock</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsForRepurchaseOfConvertiblePreferredStock" xlink:to="us-gaap_PaymentsForRepurchaseOfConvertiblePreferredStock_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_PaymentsOfIssuanceCostsOfRedeemableConvertiblePreferredStock" xlink:label="xfor_PaymentsOfIssuanceCostsOfRedeemableConvertiblePreferredStock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_PaymentsOfIssuanceCostsOfRedeemableConvertiblePreferredStock_lbl" xml:lang="en-US" id="id_13073811_3532977_3_1">Payments of issuance costs of redeemable convertible preferred stock.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_PaymentsOfIssuanceCostsOfRedeemableConvertiblePreferredStock_lbl" xml:lang="en-US" id="id_13073811_3532977_1_1">Payments Of Issuance Costs Of Redeemable Convertible Preferred Stock</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="xfor_PaymentsOfIssuanceCostsOfRedeemableConvertiblePreferredStock_lbl" xml:lang="en-US" id="id_13073811_3532977_14_1">Payments of issuance costs of convertible preferred stock</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired" xlink:label="us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_lbl" xml:lang="en-US" id="id_13073811_3076853_1_1">Payments to Acquire Businesses, Net of Cash Acquired</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_lbl" xml:lang="en-US" id="id_13073811_3076853_14_1">Cash and restricted cash acquired in connection with the Merger</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired" xlink:to="us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment" xlink:label="us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment_lbl" xml:lang="en-US" id="id_13073811_3076856_1_1">Payments to Acquire in Process Research and Development</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment_lbl" xml:lang="en-US" id="id_13073811_3076856_2_1">Cash payment</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment" xlink:to="us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_PercentageOfMinimumCashBalanceEqualToOutstandingPrincipalAmountOfLoans" xlink:label="xfor_PercentageOfMinimumCashBalanceEqualToOutstandingPrincipalAmountOfLoans"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_PercentageOfMinimumCashBalanceEqualToOutstandingPrincipalAmountOfLoans_lbl" xml:lang="en-US" id="id_13073811_3566599_3_1">Percentage Of Minimum Cash Balance Equal To Outstanding Principal Amount Of Loans</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_PercentageOfMinimumCashBalanceEqualToOutstandingPrincipalAmountOfLoans_lbl" xml:lang="en-US" id="id_13073811_3566599_1_1">Percentage Of Minimum Cash Balance Equal To Outstanding Principal Amount Of Loans</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_PercentageOfMinimumCashBalanceEqualToOutstandingPrincipalAmountOfLoans_lbl" xml:lang="en-US" id="id_13073811_3566599_2_1">Percentage of minimum cash balance</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_PercentageOfMinimumCashBalanceEqualToOutstandingPrincipalAmountOfLoans" xlink:to="xfor_PercentageOfMinimumCashBalanceEqualToOutstandingPrincipalAmountOfLoans_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="us-gaap_PlanNameAxis"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PlanNameAxis_lbl" xml:lang="en-US" id="id_13073811_3076363_1_1">Plan Name [Axis]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PlanNameAxis_lbl" xml:lang="en-US" id="id_13073811_3076363_2_1">Plan Name [Axis]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PlanNameAxis" xlink:to="us-gaap_PlanNameAxis_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="us-gaap_PlanNameDomain"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PlanNameDomain_lbl" xml:lang="en-US" id="id_13073811_3076892_1_1">Plan Name [Domain]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PlanNameDomain_lbl" xml:lang="en-US" id="id_13073811_3076892_2_1">Plan Name [Domain]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PlanNameDomain" xlink:to="us-gaap_PlanNameDomain_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PreferredStockDividendRatePercentage" xlink:label="us-gaap_PreferredStockDividendRatePercentage"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PreferredStockDividendRatePercentage_lbl" xml:lang="en-US" id="id_13073811_3077606_1_1">Preferred Stock, Dividend Rate, Percentage</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PreferredStockDividendRatePercentage_lbl" xml:lang="en-US" id="id_13073811_3077606_2_1">Expected dividend yield</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockDividendRatePercentage" xlink:to="us-gaap_PreferredStockDividendRatePercentage_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_PreferredStockFairValuePerShare" xlink:label="xfor_PreferredStockFairValuePerShare"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_PreferredStockFairValuePerShare_lbl" xml:lang="en-US" id="id_13073811_3353968_3_1">Preferred stock fair value per share.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_PreferredStockFairValuePerShare_lbl" xml:lang="en-US" id="id_13073811_3353968_1_1">Preferred Stock Fair Value Per Share</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_PreferredStockFairValuePerShare_lbl" xml:lang="en-US" id="id_13073811_3353968_2_1">Preferred stock Fair value per share</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_PreferredStockFairValuePerShare" xlink:to="xfor_PreferredStockFairValuePerShare_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_PreferredStockIssuanceCosts" xlink:label="xfor_PreferredStockIssuanceCosts"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_PreferredStockIssuanceCosts_lbl" xml:lang="en-US" id="id_13073811_3112344_3_1">Preferred Stock Issuance Costs</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_PreferredStockIssuanceCosts_lbl" xml:lang="en-US" id="id_13073811_3112344_1_1">Preferred Stock Issuance Costs</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_PreferredStockIssuanceCosts_lbl" xml:lang="en-US" id="id_13073811_3112344_2_1">Net of issuance costs</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PreferredStockValueOutstanding" xlink:label="us-gaap_PreferredStockValueOutstanding"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PreferredStockValueOutstanding_lbl" xml:lang="en-US" id="id_13073811_3077619_1_1">Preferred Stock, Value, Outstanding</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PreferredStockValueOutstanding_lbl" xml:lang="en-US" id="id_13073811_3077619_2_1">Preferred stock outstanding</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockValueOutstanding" xlink:to="us-gaap_PreferredStockValueOutstanding_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_PreferredStockWarrantLiability" xlink:label="xfor_PreferredStockWarrantLiability"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_PreferredStockWarrantLiability_lbl" xml:lang="en-US" id="id_13073811_3107639_3_1">Preferred Stock Warrant Liability</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_PreferredStockWarrantLiability_lbl" xml:lang="en-US" id="id_13073811_3107639_2_1">Preferred stock warrant liability</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ProceedsFromIssuanceOfCommonStockBeforeUnderwritingDiscountsCommissionsAndOtherExpenses_lbl" xml:lang="en-US" id="id_13073811_3191464_3_1">Proceeds From Issuance Of Common Stock Before Underwriting Discounts Commissions And Other Expenses</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromLinesOfCredit" xlink:label="us-gaap_ProceedsFromLinesOfCredit"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ProceedsFromLinesOfCredit_lbl" xml:lang="en-US" id="id_13073811_3077904_2_1">Proceeds from lines of credit</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromLinesOfCredit" xlink:to="us-gaap_ProceedsFromLinesOfCredit_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProceedsFromSaleOfIntangibleAssets_lbl" xml:lang="en-US" id="id_13073811_3078227_1_1">Proceeds from Sale of Intangible Assets</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProfitLoss_lbl" xml:lang="en-US" id="id_13073811_3078267_1_1">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProFormaMember" xlink:label="us-gaap_ProFormaMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProFormaMember_lbl" xml:lang="en-US" id="id_13073811_3078418_1_1">Pro Forma [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ProFormaMember_lbl" xml:lang="en-US" id="id_13073811_3078418_2_1">Pro Forma [Member]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PropertyPlantAndEquipmentAbstract_lbl" xml:lang="en-US" id="id_13073811_3078271_2_1">Property, Plant and Equipment [Abstract]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl" xml:lang="en-US" id="id_13073811_3078429_2_1">Property, Plant and Equipment, Type [Axis]</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="us-gaap_PropertyPlantAndEquipmentGross"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xml:lang="en-US" id="id_13073811_3078637_1_1">Property, Plant and Equipment, Gross</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xml:lang="en-US" id="id_13073811_3078637_2_1">Property and Equipment, Gross</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentGross" xlink:to="us-gaap_PropertyPlantAndEquipmentGross_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems_lbl" xml:lang="en-US" id="id_13073811_3078642_1_1">Property, Plant and Equipment [Line Items]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems_lbl" xml:lang="en-US" id="id_13073811_3078642_2_1">Property, Plant and Equipment [Line Items]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentLineItems" xlink:to="us-gaap_PropertyPlantAndEquipmentLineItems_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="us-gaap_PropertyPlantAndEquipmentNet"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xml:lang="en-US" id="id_13073811_3077229_1_1">Property, Plant and Equipment, Net</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xml:lang="en-US" id="id_13073811_3077229_2_1">Property and equipment, net</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xml:lang="en-US" id="id_13073811_3077229_6_1">Property and Equipment, Net</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentPolicyTextBlock" xlink:label="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3078434_1_1">Property, Plant and Equipment, Policy [Policy Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock_lbl" xml:lang="en-US" id="id_13073811_3078434_2_1">Property and Equipment</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock" xlink:to="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTextBlock" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xml:lang="en-US" id="id_13073811_3078284_1_1">Property, Plant and Equipment [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xml:lang="en-US" id="id_13073811_3078284_2_1">Schedule of Property and Equipment</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" xml:lang="en-US" id="id_13073811_3078646_1_1">Property, Plant and Equipment, Type [Domain]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" xml:lang="en-US" id="id_13073811_3078646_2_1">Property, Plant and Equipment, Type [Domain]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:to="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PropertyPlantAndEquipmentUsefulLife_lbl" xml:lang="en-US" id="id_13073811_3078647_1_1">Property, Plant and Equipment, Useful Life</label>
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    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_PropertyPlantAndEquipmentUsefulLivesAbstract" xlink:label="xfor_PropertyPlantAndEquipmentUsefulLivesAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_PropertyPlantAndEquipmentUsefulLivesAbstract_lbl" xml:lang="en-US" id="id_13073811_3085950_3_1">Property Plant And Equipment Useful Lives [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_PropertyPlantAndEquipmentUsefulLivesAbstract_lbl" xml:lang="en-US" id="id_13073811_3085950_1_1">Property Plant And Equipment Useful Lives [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_PropertyPlantAndEquipmentUsefulLivesAbstract_lbl" xml:lang="en-US" id="id_13073811_3085950_2_1">Property Plant And Equipment Useful Lives [Abstract]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_PropertyPlantAndEquipmentUsefulLivesAbstract" xlink:to="xfor_PropertyPlantAndEquipmentUsefulLivesAbstract_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_PropertyPlantAndEquipmentUsefulLivesTableTextBlock_lbl" xml:lang="en-US" id="id_13073811_3343630_3_1">Property Plant And Equipment Useful Lives Table [Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_PropertyPlantAndEquipmentUsefulLivesTableTextBlock_lbl" xml:lang="en-US" id="id_13073811_3343630_1_1">Property Plant And Equipment Useful Lives [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_PropertyPlantAndEquipmentUsefulLivesTableTextBlock_lbl" xml:lang="en-US" id="id_13073811_3343630_2_1">Property and Equipment</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PurchaseObligation" xlink:label="us-gaap_PurchaseObligation"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PurchaseObligation_lbl" xml:lang="en-US" id="id_13073811_3078492_1_1">Purchase Obligation</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PurchaseObligation_lbl" xml:lang="en-US" id="id_13073811_3078492_2_1">Non-cancelable purchase commitments amount</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PurchaseObligation" xlink:to="us-gaap_PurchaseObligation_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PurchaseObligationDueInSecondYear" xlink:label="us-gaap_PurchaseObligationDueInSecondYear"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PurchaseObligationDueInSecondYear_lbl" xml:lang="en-US" id="id_13073811_3078697_1_1">Purchase Obligation, Due in Second Year</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PurchaseObligationDueInSecondYear_lbl" xml:lang="en-US" id="id_13073811_3078697_2_1">Non-cancelable purchase commitments amount, 2020</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PurchaseObligationDueInSecondYear" xlink:to="us-gaap_PurchaseObligationDueInSecondYear_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear" xlink:label="us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear_lbl" xml:lang="en-US" id="id_13073811_3078494_1_1">Purchase Obligation, Future Minimum Payments, Remainder of Fiscal Year</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear_lbl" xml:lang="en-US" id="id_13073811_3078494_2_1">Non-cancelable purchase commitments amount, 2019</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear" xlink:to="us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_QualifyingExpensesUnderLetterAgreement" xlink:label="xfor_QualifyingExpensesUnderLetterAgreement"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_QualifyingExpensesUnderLetterAgreement_lbl" xml:lang="en-US" id="id_13073811_3532978_3_1">Qualifying expenses under the letter agreement.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_QualifyingExpensesUnderLetterAgreement_lbl" xml:lang="en-US" id="id_13073811_3532978_1_1">Qualifying Expenses Under Letter Agreement</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_QualifyingExpensesUnderLetterAgreement_lbl" xml:lang="en-US" id="id_13073811_3532978_2_1">Qualifying expenses related to letter agreement</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_QualifyingExpensesUnderLetterAgreement" xlink:to="xfor_QualifyingExpensesUnderLetterAgreement_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_RangeAxis_lbl" xml:lang="en-US" id="id_13073811_3078512_1_1">Range [Axis]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="srt_RangeAxis_lbl" xml:lang="en-US" id="id_13073811_3078512_2_1">Range [Axis]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RangeAxis" xlink:to="srt_RangeAxis_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_RangeMember_lbl" xml:lang="en-US" id="id_13073811_3077288_1_1">Range [Domain]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="srt_RangeMember_lbl" xml:lang="en-US" id="id_13073811_3077288_2_1">Range [Domain]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RangeMember" xlink:to="srt_RangeMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ReacquisitionPriceOfBorrowing" xlink:label="xfor_ReacquisitionPriceOfBorrowing"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ReacquisitionPriceOfBorrowing_lbl" xml:lang="en-US" id="id_13073811_3566850_3_1">Reacquisition price of borrowing.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ReacquisitionPriceOfBorrowing_lbl" xml:lang="en-US" id="id_13073811_3566850_1_1">Reacquisition Price of Borrowing</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ReacquisitionPriceOfBorrowing_lbl" xml:lang="en-US" id="id_13073811_3566850_2_1">Reacquisition price of borrowing</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ReacquisitionPriceOfBorrowing" xlink:to="xfor_ReacquisitionPriceOfBorrowing_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_RedeemableCommonStockMember" xlink:label="xfor_RedeemableCommonStockMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_RedeemableCommonStockMember_lbl" xml:lang="en-US" id="id_13073811_3265817_3_1">Redeemable Common Stock [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_RedeemableCommonStockMember_lbl" xml:lang="en-US" id="id_13073811_3265817_1_1">Redeemable Common Stock [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_RedeemableCommonStockMember_lbl" xml:lang="en-US" id="id_13073811_3265817_2_1">Redeemable Common Stock [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_RedeemableCommonStockMember" xlink:to="xfor_RedeemableCommonStockMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ReimbursementRateForResearchAndDevelopment" xlink:label="xfor_ReimbursementRateForResearchAndDevelopment"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ReimbursementRateForResearchAndDevelopment_lbl" xml:lang="en-US" id="id_13073811_3393287_3_1">Reimbursement rate for research and development expenses.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ReimbursementRateForResearchAndDevelopment_lbl" xml:lang="en-US" id="id_13073811_3393287_1_1">Reimbursement Rate For Research And Development</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ReimbursementRateForResearchAndDevelopment_lbl" xml:lang="en-US" id="id_13073811_3393287_2_1">Grant income</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ReimbursementRateForResearchAndDevelopment" xlink:to="xfor_ReimbursementRateForResearchAndDevelopment_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="us-gaap_RelatedPartyDomain"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RelatedPartyDomain_lbl" xml:lang="en-US" id="id_13073811_3078036_1_1">Related Party [Domain]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_RelatedPartyDomain_lbl" xml:lang="en-US" id="id_13073811_3078036_2_1">Related Party [Domain]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="us-gaap_RelatedPartyDomain_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" xml:lang="en-US" id="id_13073811_3078046_1_1">Related Party [Axis]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" xml:lang="en-US" id="id_13073811_3078046_2_1">Related Party [Axis]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_RepaymentOfDebtFinalPayment" xlink:label="xfor_RepaymentOfDebtFinalPayment"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_RepaymentOfDebtFinalPayment_lbl" xml:lang="en-US" id="id_13073811_3566864_3_1">Repayment of debt final payment.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_RepaymentOfDebtFinalPayment_lbl" xml:lang="en-US" id="id_13073811_3566864_1_1">Repayment of Debt Final Payment</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_RepaymentOfDebtFinalPayment_lbl" xml:lang="en-US" id="id_13073811_3566864_2_1">Repayments portion of total borrowing</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_RepaymentOfDebtFinalPayment" xlink:to="xfor_RepaymentOfDebtFinalPayment_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RepaymentsOfDebt" xlink:label="us-gaap_RepaymentsOfDebt"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RepaymentsOfDebt_lbl" xml:lang="en-US" id="id_13073811_3078823_1_1">Repayments of Debt</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_RepaymentsOfDebt_lbl" xml:lang="en-US" id="id_13073811_3078823_2_1">Repayment of outstanding loan principal</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RepaymentsOfDebt" xlink:to="us-gaap_RepaymentsOfDebt_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RepaymentsOfLinesOfCredit" xlink:label="us-gaap_RepaymentsOfLinesOfCredit"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RepaymentsOfLinesOfCredit_lbl" xml:lang="en-US" id="id_13073811_3078057_1_1">Repayments of Lines of Credit</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_RepaymentsOfLinesOfCredit_lbl" xml:lang="en-US" id="id_13073811_3078057_2_1">Repayments of lines of credit</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RepaymentsOfLinesOfCredit" xlink:to="us-gaap_RepaymentsOfLinesOfCredit_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RepaymentsOfLongTermDebt" xlink:label="us-gaap_RepaymentsOfLongTermDebt"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RepaymentsOfLongTermDebt_lbl" xml:lang="en-US" id="id_13073811_3079120_1_1">Repayments of Long-term Debt</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_RepaymentsOfLongTermDebt_lbl" xml:lang="en-US" id="id_13073811_3079120_14_1">Repayments of borrowings under loan and security agreement</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RepaymentsOfLongTermDebt" xlink:to="us-gaap_RepaymentsOfLongTermDebt_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain_lbl" xml:lang="en-US" id="id_13073811_3078066_1_1">Counterparty Name [Domain]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain_lbl" xml:lang="en-US" id="id_13073811_3078066_2_1">Counterparty Name [Domain]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RepurchaseAgreementCounterpartyNameDomain" xlink:to="srt_RepurchaseAgreementCounterpartyNameDomain_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense" xlink:label="us-gaap_ResearchAndDevelopmentExpense"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xml:lang="en-US" id="id_13073811_3078842_1_1">Research and Development Expense</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xml:lang="en-US" id="id_13073811_3078842_2_1">Research and development</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xml:lang="en-US" id="id_13073811_3078842_12_1">Research and development expense</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentExpense" xlink:to="us-gaap_ResearchAndDevelopmentExpense_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xml:lang="en-US" id="id_13073811_3078843_1_1">Research and Development Expense [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xml:lang="en-US" id="id_13073811_3078843_2_1">Research and Development Expenses [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentExpenseMember" xlink:to="us-gaap_ResearchAndDevelopmentExpenseMember_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ResearchAndDevelopmentExpensePolicy" xlink:label="us-gaap_ResearchAndDevelopmentExpensePolicy"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ResearchAndDevelopmentExpensePolicy_lbl" xml:lang="en-US" id="id_13073811_3078844_1_1">Research and Development Expense, Policy [Policy Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ResearchAndDevelopmentExpensePolicy_lbl" xml:lang="en-US" id="id_13073811_3078844_2_1">Research and Development Costs</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentExpensePolicy" xlink:to="us-gaap_ResearchAndDevelopmentExpensePolicy_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_SeriesBConvertiblePreferredStockMember_lbl" xml:lang="en-US" id="id_13073811_3336062_2_1">Series B Convertible Preferred Stock [Member]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SeriesBPreferredStockMember_lbl" xml:lang="en-US" id="id_13073811_3079750_1_1">Series B Preferred Stock [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SeriesBPreferredStockMember_lbl" xml:lang="en-US" id="id_13073811_3079750_2_1">Series B Preferred Stock</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_SeriesBPreferredStockWarrantsMember_lbl" xml:lang="en-US" id="id_13073811_3280649_3_1">Series B Preferred Stock Warrants [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_SeriesBPreferredStockWarrantsMember_lbl" xml:lang="en-US" id="id_13073811_3280649_1_1">Series B Preferred Stock Warrants [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_SeriesBPreferredStockWarrantsMember_lbl" xml:lang="en-US" id="id_13073811_3280649_2_1">Series B Preferred Stock Warrants [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_SeriesBPreferredStockWarrantsMember" xlink:to="xfor_SeriesBPreferredStockWarrantsMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_SeriesBRedeemableConvertiblePreferredStockMember" xlink:label="xfor_SeriesBRedeemableConvertiblePreferredStockMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_SeriesBRedeemableConvertiblePreferredStockMember_lbl" xml:lang="en-US" id="id_13073811_3313843_3_1">Series B redeemable convertible preferred stock</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_SeriesBRedeemableConvertiblePreferredStockMember_lbl" xml:lang="en-US" id="id_13073811_3313843_1_1">Series B Redeemable Convertible Preferred Stock [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_SeriesBRedeemableConvertiblePreferredStockMember_lbl" xml:lang="en-US" id="id_13073811_3313843_2_1">Series B Redeemable Convertible Preferred Stock [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_SeriesBRedeemableConvertiblePreferredStockMember" xlink:to="xfor_SeriesBRedeemableConvertiblePreferredStockMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_SeriesSeedConvertiblePreferredStockMember" xlink:label="xfor_SeriesSeedConvertiblePreferredStockMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_SeriesSeedConvertiblePreferredStockMember_lbl" xml:lang="en-US" id="id_13073811_3252547_3_1">Series Seed Convertible Preferred Stock [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_SeriesSeedConvertiblePreferredStockMember_lbl" xml:lang="en-US" id="id_13073811_3252547_1_1">Series Seed Convertible Preferred Stock [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_SeriesSeedConvertiblePreferredStockMember_lbl" xml:lang="en-US" id="id_13073811_3252547_2_1">Series Seed Preferred Stock [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_SeriesSeedConvertiblePreferredStockMember" xlink:to="xfor_SeriesSeedConvertiblePreferredStockMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_SeriesSeedPreferredStockMember" xlink:label="xfor_SeriesSeedPreferredStockMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_SeriesSeedPreferredStockMember_lbl" xml:lang="en-US" id="id_13073811_3252195_3_1">Series Seed Preferred Stock [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_SeriesSeedPreferredStockMember_lbl" xml:lang="en-US" id="id_13073811_3252195_1_1">Series Seed Preferred Stock [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_SeriesSeedPreferredStockMember_lbl" xml:lang="en-US" id="id_13073811_3252195_2_1">Series Seed Preferred Stock [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_SeriesSeedPreferredStockMember" xlink:to="xfor_SeriesSeedPreferredStockMember_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensation_lbl" xml:lang="en-US" id="id_13073811_3079780_2_1">Stock-based compensation expense</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensation" xlink:to="us-gaap_ShareBasedCompensation_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardsGrantInPeriodWeightedAverageGrantDateFairValue" xlink:label="xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardsGrantInPeriodWeightedAverageGrantDateFairValue"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardsGrantInPeriodWeightedAverageGrantDateFairValue_lbl" xml:lang="en-US" id="id_13073811_3355784_3_1">Share Based Compensation Arrangement By Share Based Payment Award Awards Grant in Period Weighted Average Grant Date Fair Value</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardsGrantInPeriodWeightedAverageGrantDateFairValue_lbl" xml:lang="en-US" id="id_13073811_3355784_1_1">Share Based Compensation Arrangement By Share Based Payment Award Awards Grant in Period Weighted Average Grant Date Fair Value</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardsGrantInPeriodWeightedAverageGrantDateFairValue_lbl" xml:lang="en-US" id="id_13073811_3355784_2_1">Options granted, weighted average grant date fair value</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardsGrantInPeriodWeightedAverageGrantDateFairValue" xlink:to="xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardsGrantInPeriodWeightedAverageGrantDateFairValue_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights_lbl" xml:lang="en-US" id="id_13073811_3079783_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights_lbl" xml:lang="en-US" id="id_13073811_3079783_2_1">Vesting rights, descriptions</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription_lbl" xml:lang="en-US" id="id_13073811_3080375_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Description</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription_lbl" xml:lang="en-US" id="id_13073811_3080375_2_1">Share based compensation, description</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl" xml:lang="en-US" id="id_13073811_3080149_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl" xml:lang="en-US" id="id_13073811_3080149_2_1">Expected dividend yield</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_lbl" xml:lang="en-US" id="id_13073811_3079790_2_1">Expected term (in years)</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_lbl" xml:lang="en-US" id="id_13073811_3080387_2_1">Expected volatility</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_lbl" xml:lang="en-US" id="id_13073811_3080152_2_1">Risk-free interest rate</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xml:lang="en-US" id="id_13073811_3080537_1_1">Share-based Compensation Arrangement by Share-based Payment Award [Line Items]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xml:lang="en-US" id="id_13073811_3080537_2_1">Share Based Compensation Arrangement By Share Based Payment Award [Line Items]</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" xml:lang="en-US" id="id_13073811_3079794_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" xml:lang="en-US" id="id_13073811_3079794_2_1">Ordinary share issued</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAcquiredInReverseMerger_lbl" xml:lang="en-US" id="id_13073811_3567024_3_1">Share based compensation arrangement by share based payment award options acquired in reverse merger.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAcquiredInReverseMerger_lbl" xml:lang="en-US" id="id_13073811_3567024_1_1">Share Based Compensation Arrangement By Share Based Payment Award Options Acquired In Reverse Merger</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAcquiredInReverseMergerWeightedAverageExercisePrice_lbl" xml:lang="en-US" id="id_13073811_3567023_3_1">Share based compensation arrangement by share based payment award options acquired in reverse merger weighted average exercise price.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAcquiredInReverseMergerWeightedAverageExercisePrice_lbl" xml:lang="en-US" id="id_13073811_3567023_1_1">Share Based Compensation Arrangement By Share Based Payment Award Options Acquired In Reverse Merger Weighted Average Exercise Price</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAcquiredInReverseMergerWeightedAverageExercisePrice_lbl" xml:lang="en-US" id="id_13073811_3567023_2_1">Weighted average exercise price, Assumed as part of merger with Arsanis</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAcquiredInReverseMergerWeightedAverageExercisePrice" xlink:to="xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAcquiredInReverseMergerWeightedAverageExercisePrice_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_lbl" xml:lang="en-US" id="id_13073811_3079795_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_lbl" xml:lang="en-US" id="id_13073811_3079795_2_1">Number of share options exercisable, aggregate intrinsic Value</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" xml:lang="en-US" id="id_13073811_3080542_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" xml:lang="en-US" id="id_13073811_3080542_2_1">Number of shares Options, Exercisable</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl" xml:lang="en-US" id="id_13073811_3080543_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl" xml:lang="en-US" id="id_13073811_3080543_2_1">Weighted average exercise price, Exercisable</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_lbl" xml:lang="en-US" id="id_13073811_3080544_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_lbl" xml:lang="en-US" id="id_13073811_3080544_2_1">Aggregate intrinsic value, Exercised</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_lbl" xml:lang="en-US" id="id_13073811_3080159_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_lbl" xml:lang="en-US" id="id_13073811_3080159_14_1">Number of shares, Forfeited</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xml:lang="en-US" id="id_13073811_3080547_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xml:lang="en-US" id="id_13073811_3080547_2_1">Number of shares, Granted</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xml:lang="en-US" id="id_13073811_3080547_12_1">Stock-based compensation arrangement, number of options granted to purchase shares</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_lbl" xml:lang="en-US" id="id_13073811_3081064_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_lbl" xml:lang="en-US" id="id_13073811_3081064_4_1">Aggregate intrinsic value, Ending balance</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_lbl" xml:lang="en-US" id="id_13073811_3081064_5_1">Aggregate intrinsic value, Beginning balance</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xml:lang="en-US" id="id_13073811_3080549_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xml:lang="en-US" id="id_13073811_3080549_4_1">Number of shares Outstanding, Ending balance</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xml:lang="en-US" id="id_13073811_3080549_5_1">Number of shares outstanding, Beginning balance</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xml:lang="en-US" id="id_13073811_3080551_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xml:lang="en-US" id="id_13073811_3080551_4_1">Weighted average exercise price, Ending balance</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xml:lang="en-US" id="id_13073811_3080551_5_1">Weighted average exercise price, Beginning balance</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_lbl" xml:lang="en-US" id="id_13073811_3079805_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_lbl" xml:lang="en-US" id="id_13073811_3079805_2_1">Weighted average contractual term outstanding, Beginning balance</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice_lbl" xml:lang="en-US" id="id_13073811_3080553_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Exercise Price</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice_lbl" xml:lang="en-US" id="id_13073811_3080553_2_1">Weighted average exercise price, Vested and expected to vest</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_lbl" xml:lang="en-US" id="id_13073811_3080164_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_lbl" xml:lang="en-US" id="id_13073811_3080164_2_1">Number of shares Options, Vested and expected to vest</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum_lbl" xml:lang="en-US" id="id_13073811_3079812_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Outstanding Stock Maximum</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum_lbl" xml:lang="en-US" id="id_13073811_3079812_2_1">Percentage of number of common stock outstanding</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_lbl" xml:lang="en-US" id="id_13073811_3081069_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_lbl" xml:lang="en-US" id="id_13073811_3081069_2_1">Shares of common stock issued</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_SharebasedCompensationArrangementBySharebasedPaymentAwardStockOptionsSharesOutstandingWeightedAverageExercisePriceAndAdditionalDisclosuresAbstract" xlink:label="xfor_SharebasedCompensationArrangementBySharebasedPaymentAwardStockOptionsSharesOutstandingWeightedAverageExercisePriceAndAdditionalDisclosuresAbstract"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockIssuedDuringPeriodSharesAcquisitions_lbl" xml:lang="en-US" id="id_13073811_3081323_1_1">Stock Issued During Period, Shares, Acquisitions</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodSharesAcquisitions_lbl" xml:lang="en-US" id="id_13073811_3081323_2_1">Exchange of common stock in connection with Merger, shares</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_lbl" xml:lang="en-US" id="id_13073811_3080940_1_1">Stock Issued During Period, Shares, Conversion of Convertible Securities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_lbl" xml:lang="en-US" id="id_13073811_3080940_2_1">Conversion of convertible preferred shares into common stock, shares</label>
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    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_StockIssuedDuringPeriodSharesLicenseAgreement" xlink:label="xfor_StockIssuedDuringPeriodSharesLicenseAgreement"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_StockIssuedDuringPeriodSharesLicenseAgreement_lbl" xml:lang="en-US" id="id_13073811_3202466_3_1">Stock Issued During Period Shares License Agreement</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_StockIssuedDuringPeriodSharesLicenseAgreement_lbl" xml:lang="en-US" id="id_13073811_3202466_1_1">Stock Issued During Period Shares License Agreement</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_StockIssuedDuringPeriodSharesLicenseAgreement_lbl" xml:lang="en-US" id="id_13073811_3202466_2_1">Stock issued during period</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_StockIssuedDuringPeriodSharesLicenseAgreement" xlink:to="xfor_StockIssuedDuringPeriodSharesLicenseAgreement_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xml:lang="en-US" id="id_13073811_3081183_1_1">Stock Issued During Period, Shares, New Issues</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xml:lang="en-US" id="id_13073811_3081183_2_1">Common Stock issued</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xml:lang="en-US" id="id_13073811_3081183_14_1">Repurchase of Series Seed convertible preferred stock</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:to="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits" xlink:label="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits_lbl" xml:lang="en-US" id="id_13073811_3079936_1_1">Stock Issued During Period, Shares, Reverse Stock Splits</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits_lbl" xml:lang="en-US" id="id_13073811_3079936_2_1">Number of shares of the combined organization owned by Arsanis stockholders</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits" xlink:to="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xml:lang="en-US" id="id_13073811_3081328_1_1">Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xml:lang="en-US" id="id_13073811_3081328_2_1">Exercise of stock options, shares</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xml:lang="en-US" id="id_13073811_3081328_14_1">Number of shares, Exercised</label>
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    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueAcquisitions" xlink:label="us-gaap_StockIssuedDuringPeriodValueAcquisitions"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockIssuedDuringPeriodValueAcquisitions_lbl" xml:lang="en-US" id="id_13073811_3080944_1_1">Stock Issued During Period, Value, Acquisitions</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodValueAcquisitions_lbl" xml:lang="en-US" id="id_13073811_3080944_2_1">Exchange of common stock in connection with Merger</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodValueAcquisitions_lbl" xml:lang="en-US" id="id_13073811_3080944_12_1">Fair value of consideration issued it effect the Merger</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueAcquisitions" xlink:to="us-gaap_StockIssuedDuringPeriodValueAcquisitions_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" xlink:label="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_lbl" xml:lang="en-US" id="id_13073811_3081330_1_1">Stock Issued During Period, Value, Conversion of Convertible Securities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_lbl" xml:lang="en-US" id="id_13073811_3081330_2_1">Conversion of convertible preferred shares into common stock</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" xlink:to="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_StockIssuedDuringPeriodValueLicenseAgreement" xlink:label="xfor_StockIssuedDuringPeriodValueLicenseAgreement"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_StockIssuedDuringPeriodValueLicenseAgreement_lbl" xml:lang="en-US" id="id_13073811_3096339_3_1">Stock Issued During Period Value License Agreement</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_StockIssuedDuringPeriodValueLicenseAgreement_lbl" xml:lang="en-US" id="id_13073811_3096339_1_1">Stock Issued During Period Value License Agreement</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_StockIssuedDuringPeriodValueLicenseAgreement_lbl" xml:lang="en-US" id="id_13073811_3096339_2_1">Common stock aggregate fair value</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_StockIssuedDuringPeriodValueLicenseAgreement" xlink:to="xfor_StockIssuedDuringPeriodValueLicenseAgreement_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xml:lang="en-US" id="id_13073811_3079941_1_1">Stock Issued During Period, Value, New Issues</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xml:lang="en-US" id="id_13073811_3079941_2_1">Repurchase of Series Seed convertible preferred stock, share</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xml:lang="en-US" id="id_13073811_3079941_12_1">Research and Development Expense</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:to="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_lbl" xml:lang="en-US" id="id_13073811_3079946_1_1">Stock Issued During Period, Value, Stock Options Exercised</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_lbl" xml:lang="en-US" id="id_13073811_3079946_2_1">Exercise of stock options</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:to="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SubsequentEventLineItems_lbl" xml:lang="en-US" id="id_13073811_3080631_1_1">Subsequent Event [Line Items]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SubsequentEventLineItems_lbl" xml:lang="en-US" id="id_13073811_3080631_2_1">Subsequent Event [Line Items]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SubsequentEventMember_lbl" xml:lang="en-US" id="id_13073811_3080964_1_1">Subsequent Event [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SubsequentEventMember_lbl" xml:lang="en-US" id="id_13073811_3080964_2_1">Subsequent Event [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventMember" xlink:to="us-gaap_SubsequentEventMember_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SubsequentEventsAbstract_lbl" xml:lang="en-US" id="id_13073811_3080965_1_1">Subsequent Events [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SubsequentEventsAbstract_lbl" xml:lang="en-US" id="id_13073811_3080965_2_1">Subsequent Events [Abstract]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventsAbstract" xlink:to="us-gaap_SubsequentEventsAbstract_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SubsequentEventsTextBlock_lbl" xml:lang="en-US" id="id_13073811_3081212_2_1">Subsequent Events</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventsTextBlock" xlink:to="us-gaap_SubsequentEventsTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventTable" xlink:label="us-gaap_SubsequentEventTable"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SubsequentEventTable_lbl" xml:lang="en-US" id="id_13073811_3080632_1_1">Subsequent Event [Table]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SubsequentEventTable_lbl" xml:lang="en-US" id="id_13073811_3080632_2_1">Subsequent Event [Table]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventTable" xlink:to="us-gaap_SubsequentEventTable_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SubsequentEventTypeDomain_lbl" xml:lang="en-US" id="id_13073811_3080966_2_1">Subsequent Event Type [Domain]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventTypeDomain_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_SvbLoanAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3566848_3_1">SVB loan agreement [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_SvbLoanAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3566848_1_1">SVB Loan Agreement [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_SvbLoanAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3566848_2_1">SVB Loan Agreement [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_SvbLoanAgreementMember" xlink:to="xfor_SvbLoanAgreementMember_lbl"/>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment_lbl" xml:lang="en-US" id="id_13073811_3080695_1_1">Temporary Equity, Accretion to Redemption Value, Adjustment</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment_lbl" xml:lang="en-US" id="id_13073811_3080695_14_1">Accruing dividends on Series A convertible preferred stock</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment" xlink:to="us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TemporaryEquityByClassOfStockTable" xlink:label="us-gaap_TemporaryEquityByClassOfStockTable"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TemporaryEquityByClassOfStockTable_lbl" xml:lang="en-US" id="id_13073811_3081032_1_1">Temporary Equity, by Class of Stock [Table]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_TemporaryEquityByClassOfStockTable_lbl" xml:lang="en-US" id="id_13073811_3081032_2_1">Temporary Equity, by Class of Stock [Table]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TemporaryEquityByClassOfStockTable" xlink:to="us-gaap_TemporaryEquityByClassOfStockTable_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TemporaryEquityCarryingAmountAttributableToParent" xlink:label="us-gaap_TemporaryEquityCarryingAmountAttributableToParent"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TemporaryEquityCarryingAmountAttributableToParent_lbl" xml:lang="en-US" id="id_13073811_3081033_1_1">Temporary Equity, Carrying Amount, Attributable to Parent</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_TemporaryEquityCarryingAmountAttributableToParent_lbl" xml:lang="en-US" id="id_13073811_3081033_4_1">Convertible preferred shares, ending balance</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_TemporaryEquityCarryingAmountAttributableToParent_lbl" xml:lang="en-US" id="id_13073811_3081033_5_1">Convertible preferred shares, beginning balance</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_TemporaryEquityCarryingAmountAttributableToParent_lbl" xml:lang="en-US" id="id_13073811_3081033_2_1">Carrying Value</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_TemporaryEquityCarryingAmountAttributableToParent_lbl" xml:lang="en-US" id="id_13073811_3081033_12_1">Convertible preferred stock (Series Seed, A and B), $0.001 par value;10,000,000 and 59,413,523 shares authorized as of March 31, 2019 and December 31, 2018, respectively; 0 and 40,079,567 shares issued and outstanding as of March 31, 2019 and December 31, 2018, respectively</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TemporaryEquityCarryingAmountAttributableToParent" xlink:to="us-gaap_TemporaryEquityCarryingAmountAttributableToParent_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TemporaryEquityDividendsAdjustment" xlink:label="us-gaap_TemporaryEquityDividendsAdjustment"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TemporaryEquityDividendsAdjustment_lbl" xml:lang="en-US" id="id_13073811_3080697_1_1">Temporary Equity, Dividends, Adjustment</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_TemporaryEquityDividendsAdjustment_lbl" xml:lang="en-US" id="id_13073811_3080697_14_1">Accruing dividends on Series A convertible preferred stock</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TemporaryEquityDividendsAdjustment" xlink:to="us-gaap_TemporaryEquityDividendsAdjustment_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TemporaryEquityLineItems" xlink:label="us-gaap_TemporaryEquityLineItems"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TemporaryEquityLineItems_lbl" xml:lang="en-US" id="id_13073811_3080698_1_1">Temporary Equity [Line Items]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_TemporaryEquityLineItems_lbl" xml:lang="en-US" id="id_13073811_3080698_2_1">Temporary Equity [Line Items]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TemporaryEquityLineItems" xlink:to="us-gaap_TemporaryEquityLineItems_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TemporaryEquityLiquidationPreference" xlink:label="us-gaap_TemporaryEquityLiquidationPreference"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TemporaryEquityLiquidationPreference_lbl" xml:lang="en-US" id="id_13073811_3080699_1_1">Temporary Equity, Liquidation Preference</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_TemporaryEquityLiquidationPreference_lbl" xml:lang="en-US" id="id_13073811_3080699_2_1">Liquidation Preference</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TemporaryEquityLiquidationPreference" xlink:to="us-gaap_TemporaryEquityLiquidationPreference_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TemporaryEquityParOrStatedValuePerShare" xlink:label="us-gaap_TemporaryEquityParOrStatedValuePerShare"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TemporaryEquityParOrStatedValuePerShare_lbl" xml:lang="en-US" id="id_13073811_3081037_1_1">Temporary Equity, Par or Stated Value Per Share</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_TemporaryEquityParOrStatedValuePerShare_lbl" xml:lang="en-US" id="id_13073811_3081037_2_1">Convertible preferred stock, par or stated value per share</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TemporaryEquityParOrStatedValuePerShare" xlink:to="us-gaap_TemporaryEquityParOrStatedValuePerShare_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStock" xlink:label="xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStock_lbl" xml:lang="en-US" id="id_13073811_3566162_3_1">Temporary equity repurchase of convertible preferred stock.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStock_lbl" xml:lang="en-US" id="id_13073811_3566162_1_1">Temporary Equity Repurchase of Convertible Preferred Stock</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStock_lbl" xml:lang="en-US" id="id_13073811_3566162_14_1">Repurchase of Series Seed convertible preferred stock, net of issuance costs of $1</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStock" xlink:to="xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStock_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStockShare" xlink:label="xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStockShare"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStockShare_lbl" xml:lang="en-US" id="id_13073811_3566163_3_1">Temporary equity repurchase of convertible preferred share.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStockShare_lbl" xml:lang="en-US" id="id_13073811_3566163_1_1">Temporary Equity Repurchase of Convertible Preferred Stock Share</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStockShare_lbl" xml:lang="en-US" id="id_13073811_3566163_2_1">Repurchase of Series Seed convertible preferred stock, net of issuance costs of $1, share</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStockShare" xlink:to="xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStockShare_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TemporaryEquitySharesAuthorized" xlink:label="us-gaap_TemporaryEquitySharesAuthorized"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TemporaryEquitySharesAuthorized_lbl" xml:lang="en-US" id="id_13073811_3081415_1_1">Temporary Equity, Shares Authorized</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_TemporaryEquitySharesAuthorized_lbl" xml:lang="en-US" id="id_13073811_3081415_2_1">Convertible preferred stock, shares authorized</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_TemporaryEquitySharesAuthorized_lbl" xml:lang="en-US" id="id_13073811_3081415_12_1">Preferred Stock Designated</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TemporaryEquitySharesAuthorized" xlink:to="us-gaap_TemporaryEquitySharesAuthorized_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TemporaryEquitySharesIssued" xlink:label="us-gaap_TemporaryEquitySharesIssued"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TemporaryEquitySharesIssued_lbl" xml:lang="en-US" id="id_13073811_3081039_1_1">Temporary Equity, Shares Issued</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_TemporaryEquitySharesIssued_lbl" xml:lang="en-US" id="id_13073811_3081039_2_1">Convertible preferred stock, shares issued</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_TemporaryEquitySharesIssued_lbl" xml:lang="en-US" id="id_13073811_3081039_12_1">Preferred Stock Issued</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TemporaryEquitySharesIssued" xlink:to="us-gaap_TemporaryEquitySharesIssued_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TemporaryEquitySharesOutstanding" xlink:label="us-gaap_TemporaryEquitySharesOutstanding"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TemporaryEquitySharesOutstanding_lbl" xml:lang="en-US" id="id_13073811_3080701_1_1">Temporary Equity, Shares Outstanding</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_TemporaryEquitySharesOutstanding_lbl" xml:lang="en-US" id="id_13073811_3080701_4_1">Convertible preferred shares, ending balance, shares</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_TemporaryEquitySharesOutstanding_lbl" xml:lang="en-US" id="id_13073811_3080701_5_1">Convertible preferred shares, beginning balance, shares</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_TemporaryEquitySharesOutstanding_lbl" xml:lang="en-US" id="id_13073811_3080701_2_1">Convertible preferred stock, shares outstanding</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_TemporaryEquitySharesOutstanding_lbl" xml:lang="en-US" id="id_13073811_3080701_12_1">Preferred Stock Outstanding</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TemporaryEquitySharesOutstanding" xlink:to="us-gaap_TemporaryEquitySharesOutstanding_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TemporaryEquityTableTextBlock" xlink:label="us-gaap_TemporaryEquityTableTextBlock"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TemporaryEquityTableTextBlock_lbl" xml:lang="en-US" id="id_13073811_3081937_1_1">Temporary Equity [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_TemporaryEquityTableTextBlock_lbl" xml:lang="en-US" id="id_13073811_3081937_2_1">Preferred Stock</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TemporaryEquityTableTextBlock" xlink:to="us-gaap_TemporaryEquityTableTextBlock_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_TermLoanAMember" xlink:label="xfor_TermLoanAMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_TermLoanAMember_lbl" xml:lang="en-US" id="id_13073811_3274845_3_1">Term Loan A [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_TermLoanAMember_lbl" xml:lang="en-US" id="id_13073811_3274845_1_1">Term Loan A [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_TermLoanAMember_lbl" xml:lang="en-US" id="id_13073811_3274845_2_1">Term Loan A [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_TermLoanAMember" xlink:to="xfor_TermLoanAMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_TermLoanMember" xlink:label="xfor_TermLoanMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_TermLoanMember_lbl" xml:lang="en-US" id="id_13073811_3277065_3_1">Term Loan [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_TermLoanMember_lbl" xml:lang="en-US" id="id_13073811_3277065_1_1">Term Loan [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_TermLoanMember_lbl" xml:lang="en-US" id="id_13073811_3277065_2_1">Term Loan [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_TermLoanMember" xlink:to="xfor_TermLoanMember_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TextBlockAbstract" xlink:label="us-gaap_TextBlockAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TextBlockAbstract_lbl" xml:lang="en-US" id="id_13073811_3081941_1_1">Text Block [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_TextBlockAbstract_lbl" xml:lang="en-US" id="id_13073811_3081941_2_1">Text Block [Abstract]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TextBlockAbstract" xlink:to="us-gaap_TextBlockAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ThirdTrancheMember" xlink:label="xfor_ThirdTrancheMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ThirdTrancheMember_lbl" xml:lang="en-US" id="id_13073811_3320627_3_1">Third Tranche [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ThirdTrancheMember_lbl" xml:lang="en-US" id="id_13073811_3320627_1_1">Third Tranche [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ThirdTrancheMember_lbl" xml:lang="en-US" id="id_13073811_3320627_2_1">Third Tranche [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ThirdTrancheMember" xlink:to="xfor_ThirdTrancheMember_lbl"/>
    <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_TradingSymbol" xlink:label="dei_TradingSymbol"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_TradingSymbol_lbl" xml:lang="en-US" id="id_13073811_3080759_1_1">Trading Symbol</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="dei_TradingSymbol_lbl" xml:lang="en-US" id="id_13073811_3080759_2_1">Trading Symbol</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_TradingSymbol" xlink:to="dei_TradingSymbol_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_TwoThousandFifteenEquityIncentivePlanMember" xlink:label="xfor_TwoThousandFifteenEquityIncentivePlanMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_TwoThousandFifteenEquityIncentivePlanMember_lbl" xml:lang="en-US" id="id_13073811_3285121_3_1">Two Thousand Fifteen Equity Incentive Plan [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_TwoThousandFifteenEquityIncentivePlanMember_lbl" xml:lang="en-US" id="id_13073811_3285121_1_1">Two Thousand Fifteen Equity Incentive Plan [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_TwoThousandFifteenEquityIncentivePlanMember_lbl" xml:lang="en-US" id="id_13073811_3285121_2_1">2015 Equity Incentive Plan [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_TwoThousandFifteenEquityIncentivePlanMember" xlink:to="xfor_TwoThousandFifteenEquityIncentivePlanMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_TwoThousandSeventeenEquityIncentivePlanMember" xlink:label="xfor_TwoThousandSeventeenEquityIncentivePlanMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_TwoThousandSeventeenEquityIncentivePlanMember_lbl" xml:lang="en-US" id="id_13073811_3384951_3_1">2017 equity incentive plan.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_TwoThousandSeventeenEquityIncentivePlanMember_lbl" xml:lang="en-US" id="id_13073811_3384951_1_1">Two Thousand Seventeen Equity Incentive Plan [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_TwoThousandSeventeenEquityIncentivePlanMember_lbl" xml:lang="en-US" id="id_13073811_3384951_2_1">2017 Equity Incentive Plan [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_TwoThousandSeventeenEquityIncentivePlanMember" xlink:to="xfor_TwoThousandSeventeenEquityIncentivePlanMember_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="us-gaap_TypeOfAdoptionMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TypeOfAdoptionMember_lbl" xml:lang="en-US" id="id_13073811_3082039_1_1">Type of Adoption [Domain]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_TypeOfAdoptionMember_lbl" xml:lang="en-US" id="id_13073811_3082039_2_1">Type of Adoption [Domain]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TypeOfAdoptionMember" xlink:to="us-gaap_TypeOfAdoptionMember_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TypeOfArrangementAxis" xlink:label="us-gaap_TypeOfArrangementAxis"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TypeOfArrangementAxis_lbl" xml:lang="en-US" id="id_13073811_3080792_1_1">Type of Arrangement and Non-arrangement Transactions [Axis]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_TypeOfArrangementAxis_lbl" xml:lang="en-US" id="id_13073811_3080792_2_1">Type of Arrangement and Non-arrangement Transactions [Axis]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TypeOfArrangementAxis" xlink:to="us-gaap_TypeOfArrangementAxis_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UnderlyingAssetClassAxis" xlink:label="us-gaap_UnderlyingAssetClassAxis"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_UnderlyingAssetClassAxis_lbl" xml:lang="en-US" id="id_13073811_3082067_1_1">Underlying Asset Class [Axis]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_UnderlyingAssetClassAxis_lbl" xml:lang="en-US" id="id_13073811_3082067_2_1">Underlying Asset Class [Axis]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UnderlyingAssetClassAxis" xlink:to="us-gaap_UnderlyingAssetClassAxis_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UnderlyingAssetClassDomain" xlink:label="us-gaap_UnderlyingAssetClassDomain"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_UnderlyingAssetClassDomain_lbl" xml:lang="en-US" id="id_13073811_3081803_1_1">Underlying Asset Class [Domain]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_UnderlyingAssetClassDomain_lbl" xml:lang="en-US" id="id_13073811_3081803_2_1">Underlying Asset Class [Domain]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UnderlyingAssetClassDomain" xlink:to="us-gaap_UnderlyingAssetClassDomain_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_UpfrontPayments" xlink:label="xfor_UpfrontPayments"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_UpfrontPayments_lbl" xml:lang="en-US" id="id_13073811_3163639_3_1">Upfront payments</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_UpfrontPayments_lbl" xml:lang="en-US" id="id_13073811_3163639_1_1">Upfront Payments</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_UpfrontPayments_lbl" xml:lang="en-US" id="id_13073811_3163639_2_1">Upfront payments</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_UpfrontPayments" xlink:to="xfor_UpfrontPayments_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UseOfEstimates" xlink:label="us-gaap_UseOfEstimates"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_UseOfEstimates_lbl" xml:lang="en-US" id="id_13073811_3082249_1_1">Use of Estimates, Policy [Policy Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_UseOfEstimates_lbl" xml:lang="en-US" id="id_13073811_3082249_2_1">Use of Estimates</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UseOfEstimates" xlink:to="us-gaap_UseOfEstimates_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VariableRateAxis" xlink:label="us-gaap_VariableRateAxis"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_VariableRateAxis_lbl" xml:lang="en-US" id="id_13073811_3082302_1_1">Variable Rate [Axis]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_VariableRateAxis_lbl" xml:lang="en-US" id="id_13073811_3082302_2_1">Variable Rate [Axis]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_VariableRateAxis" xlink:to="us-gaap_VariableRateAxis_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="us-gaap_VariableRateDomain"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_VariableRateDomain_lbl" xml:lang="en-US" id="id_13073811_3082303_1_1">Variable Rate [Domain]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_VariableRateDomain_lbl" xml:lang="en-US" id="id_13073811_3082303_2_1">Variable Rate [Domain]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_VariableRateDomain" xlink:to="us-gaap_VariableRateDomain_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VestingAxis" xlink:label="us-gaap_VestingAxis"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_VestingAxis_lbl" xml:lang="en-US" id="id_13073811_3082820_1_1">Vesting [Axis]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_VestingAxis_lbl" xml:lang="en-US" id="id_13073811_3082820_2_1">Vesting [Axis]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_VestingAxis" xlink:to="us-gaap_VestingAxis_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VestingDomain" xlink:label="us-gaap_VestingDomain"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_VestingDomain_lbl" xml:lang="en-US" id="id_13073811_3082821_1_1">Vesting [Domain]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_VestingDomain_lbl" xml:lang="en-US" id="id_13073811_3082821_2_1">Vesting [Domain]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_VestingDomain" xlink:to="us-gaap_VestingDomain_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_ViennaLeaseAgreementMember" xlink:label="xfor_ViennaLeaseAgreementMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_ViennaLeaseAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3532984_3_1">Vienna lease agreement.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_ViennaLeaseAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3532984_1_1">Vienna Lease Agreement [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_ViennaLeaseAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3532984_2_1">Vienna Lease [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_ViennaLeaseAgreementMember" xlink:to="xfor_ViennaLeaseAgreementMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_WalthamLeaseAgreementMember" xlink:label="xfor_WalthamLeaseAgreementMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_WalthamLeaseAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3532985_3_1">Waltham lease agreement.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_WalthamLeaseAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3532985_1_1">Waltham Lease Agreement [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_WalthamLeaseAgreementMember_lbl" xml:lang="en-US" id="id_13073811_3532985_2_1">Waltham Lease [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_WalthamLeaseAgreementMember" xlink:to="xfor_WalthamLeaseAgreementMember_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_WalthamLeaseMember" xlink:label="xfor_WalthamLeaseMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_WalthamLeaseMember_lbl" xml:lang="en-US" id="id_13073811_3319533_3_1">Waltham Lease [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_WalthamLeaseMember_lbl" xml:lang="en-US" id="id_13073811_3319533_1_1">Waltham Lease [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_WalthamLeaseMember_lbl" xml:lang="en-US" id="id_13073811_3319533_2_1">Waltham Lease [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_WalthamLeaseMember" xlink:to="xfor_WalthamLeaseMember_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_WarrantMember" xlink:label="us-gaap_WarrantMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_WarrantMember_lbl" xml:lang="en-US" id="id_13073811_3082828_1_1">Warrant [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_WarrantMember_lbl" xml:lang="en-US" id="id_13073811_3082828_2_1">Warrant [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WarrantMember" xlink:to="us-gaap_WarrantMember_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_WarrantsAndRightsNoteDisclosureAbstract" xlink:label="us-gaap_WarrantsAndRightsNoteDisclosureAbstract"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_WarrantsAndRightsNoteDisclosureAbstract_lbl" xml:lang="en-US" id="id_13073811_3082316_1_1">Warrants and Rights Note Disclosure [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_WarrantsAndRightsNoteDisclosureAbstract_lbl" xml:lang="en-US" id="id_13073811_3082316_2_1">Warrants and Rights Note Disclosure [Abstract]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WarrantsAndRightsNoteDisclosureAbstract" xlink:to="us-gaap_WarrantsAndRightsNoteDisclosureAbstract_lbl"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" xlink:label="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_lbl" xml:lang="en-US" id="id_13073811_3082590_1_1">Weighted Average Number of Shares Outstanding, Basic and Diluted</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_lbl" xml:lang="en-US" id="id_13073811_3082590_2_1">Redeemable common stock</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_lbl" xml:lang="en-US" id="id_13073811_3082590_12_1">Weighted average common shares outstanding-basic and diluted</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" xlink:to="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_lbl"/>
    <loc xlink:type="locator" xlink:href="xfor-20190331.xsd#xfor_XfourSecurityHoldersMember" xlink:label="xfor_XfourSecurityHoldersMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="xfor_XfourSecurityHoldersMember_lbl" xml:lang="en-US" id="id_13073811_3566377_3_1">XFour Security Holders [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="xfor_XfourSecurityHoldersMember_lbl" xml:lang="en-US" id="id_13073811_3566377_1_1">XFour Security Holders [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="xfor_XfourSecurityHoldersMember_lbl" xml:lang="en-US" id="id_13073811_3566377_2_1">XFour Security Holders [Member]</label>
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="xfor_XfourSecurityHoldersMember" xlink:to="xfor_XfourSecurityHoldersMember_lbl"/>
  </labelLink>
</linkbase>
</XBRL>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-101.PRE
<SEQUENCE>16
<FILENAME>xfor-20190331_pre.xml
<DESCRIPTION>XBRL TAXONOMY EXTENSION PRESENTATION LINKBASE
<TEXT>
<XBRL>
<?xml version="1.0" encoding="US-ASCII"?>
<!-- DFIN Xcelerate Taxonomy Presentation Linkbase - https://www.dfinsolutions.com/ -->
<!-- Version: 6.23.6 -->
<!-- Round: 9 -->
<!-- Creation date: 2019-05-15T20:37:51Z -->
<!-- Copyright (c) 2019 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
<linkbase xmlns="http://www.xbrl.org/2003/linkbase"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:xlink="http://www.w3.org/1999/xlink"
  xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <roleRef xlink:type="simple" xlink:href="xfor-20190331.xsd#DocumentandEntityInformation" roleURI="http://www.x4pharma.com/taxonomy/role/DocumentandEntityInformation"/>
  <roleRef xlink:type="simple" xlink:href="xfor-20190331.xsd#StatementOfFinancialPositionClassified" roleURI="http://www.x4pharma.com/taxonomy/role/StatementOfFinancialPositionClassified"/>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>This is focus fiscal year of the document report in CCYY format. For a 2006 annual report, which may also provide financial information from prior periods, fiscal 2006 should be given as the fiscal year focus. Example: 2006.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_DocumentFiscalYearFocus</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
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<td>xbrli:gYearItemType</td>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
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<td><strong> Period Type:</strong></td>
<td>duration</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_DocumentPeriodEndDate">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The end date of the period reflected on the cover page if a periodic report. For all other reports and registration statements containing historical data, it is the date up through which that historical data is presented.  If there is no historical data in the report, use the filing date. The format of the date is CCYY-MM-DD.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_DocumentPeriodEndDate</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:dateItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_DocumentType">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_DocumentType</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>dei:submissionTypeItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityCentralIndexKey">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Regulation 12B<br> -Number 240<br> -Section 12<br> -Subsection b-2<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityCentralIndexKey</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
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<td><strong> Data Type:</strong></td>
<td>dei:centralIndexKeyItemType</td>
</tr>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityCommonStockSharesOutstanding">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Indicate number of shares or other units outstanding of each of registrant's classes of capital or common stock or other ownership interests, if and as stated on cover of related periodic report. Where multiple classes or units exist define each class/interest by adding class of stock items such as Common Class A [Member], Common Class B [Member] or Partnership Interest [Member] onto the Instrument [Domain] of the Entity Listings, Instrument.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityCommonStockSharesOutstanding</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityEmergingGrowthCompany">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Indicate if registrant meets the emerging growth company criteria.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Regulation 12B<br> -Number 240<br> -Section 12<br> -Subsection b-2<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityEmergingGrowthCompany</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:booleanItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityExTransitionPeriod">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Indicate if registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Securities Act<br> -Number 7A<br> -Section B<br> -Subsection 2<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityExTransitionPeriod</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:booleanItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityFilerCategory">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Indicate whether the registrant is one of the following: (1) Large Accelerated Filer, (2) Accelerated Filer, (3) Non-accelerated Filer, (4) Smaller Reporting Company (Non-accelerated), (5) Smaller Reporting Accelerated Filer or (6) Smaller Reporting Company and Large Accelerated Filer. Definitions of these categories are stated in Rule 12b-2 of the Exchange Act. This information should be based on the registrant's current or most recent filing containing the related disclosure.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Regulation 12B<br> -Number 240<br> -Section 12<br> -Subsection b-2<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityFilerCategory</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
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<td><strong> Data Type:</strong></td>
<td>dei:filerCategoryItemType</td>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityRegistrantName">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Regulation 12B<br> -Number 240<br> -Section 12<br> -Subsection b-2<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityRegistrantName</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:normalizedStringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntitySmallBusiness">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Indicates that the company is a smaller reporting company with both a public float and revenues of less than $75 million.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Regulation 12B<br> -Number 240<br> -Section 12<br> -Subsection b-2<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntitySmallBusiness</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:booleanItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_TradingSymbol">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Trading symbol of an instrument as listed on an exchange.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_TradingSymbol</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:normalizedStringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_DocumentAndEntityInformationAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Document and Entity Information [Abstract]</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_DocumentAndEntityInformationAbstract</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
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<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
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<td><strong> Balance Type:</strong></td>
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<td>duration</td>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6837038080">
<tr>
<th class="tl" colspan="1" rowspan="1"><div style="width: 200px;"><strong>CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Dec. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AssetsCurrentAbstract', window );"><strong>Current assets:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CashAndCashEquivalentsAtCarryingValue', window );">Cash and cash equivalents</a></td>
<td class="nump">$ 22,299<span></span>
</td>
<td class="nump">$ 8,134<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ResearchAndDevelopmentIncentiveReceivable', window );">Research and development incentive receivable</a></td>
<td class="nump">1,552<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PrepaidExpenseAndOtherAssetsCurrent', window );">Prepaid expenses and other current assets</a></td>
<td class="nump">2,372<span></span>
</td>
<td class="nump">1,205<span></span>
</td>
</tr>
<tr class="reu">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AssetsCurrent', window );">Total current assets</a></td>
<td class="nump">26,223<span></span>
</td>
<td class="nump">9,339<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentNet', window );">Property and equipment, net</a></td>
<td class="nump">271<span></span>
</td>
<td class="nump">241<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_IntangibleAssetsNetExcludingGoodwill', window );">Intangible assets</a></td>
<td class="nump">4,900<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_Goodwill', window );">Goodwill</a></td>
<td class="nump">27,407<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseRightOfUseAsset', window );">Right-of-use assets</a></td>
<td class="nump">2,705<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RestrictedCashNoncurrent', window );">Restricted cash</a></td>
<td class="nump">947<span></span>
</td>
<td class="nump">364<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OtherAssetsNoncurrent', window );">Other assets</a></td>
<td class="nump">96<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rou">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_Assets', window );">Total assets</a></td>
<td class="nump">62,549<span></span>
</td>
<td class="nump">9,944<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesCurrentAbstract', window );"><strong>Current liabilities:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AccountsPayableCurrent', window );">Accounts payable</a></td>
<td class="nump">6,132<span></span>
</td>
<td class="nump">2,969<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AccruedLiabilitiesCurrent', window );">Accrued expenses</a></td>
<td class="nump">4,179<span></span>
</td>
<td class="nump">3,251<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseLiabilityCurrent', window );">Current portion of lease liability</a></td>
<td class="nump">841<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebtCurrent', window );">Current portion of long-term debt</a></td>
<td class="nump">5,298<span></span>
</td>
<td class="nump">1,687<span></span>
</td>
</tr>
<tr class="rou">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesCurrent', window );">Total current liabilities</a></td>
<td class="nump">16,450<span></span>
</td>
<td class="nump">7,907<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_PreferredStockWarrantLiability', window );">Preferred stock warrant liability</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">4,947<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_LongTermDebtNonCurrentIncludingAccretion', window );">Long-term debt, including accretion, net of discount and current portion</a></td>
<td class="nump">13,365<span></span>
</td>
<td class="nump">8,145<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DeferredRentCreditNoncurrent', window );">Deferred rent</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">417<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseLiabilityNoncurrent', window );">Lease liability</a></td>
<td class="nump">3,275<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OtherLiabilitiesNoncurrent', window );">Other liabilities</a></td>
<td class="nump">18<span></span>
</td>
<td class="nump">205<span></span>
</td>
</tr>
<tr class="rou">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_Liabilities', window );">Total liabilities</a></td>
<td class="nump">33,108<span></span>
</td>
<td class="nump">21,621<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommitmentsAndContingencies', window );">Commitments and contingencies (Note 9)</a></td>
<td class="text"> <span></span>
</td>
<td class="text"> <span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityCarryingAmountAttributableToParent', window );">Convertible preferred stock (Series Seed, A and B), $0.001 par value;10,000,000 and 59,413,523 shares authorized as of March 31, 2019 and December 31, 2018, respectively; 0 and 40,079,567 shares issued and outstanding as of March 31, 2019 and December 31, 2018, respectively</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">64,675<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommonStockValue', window );">Common stock</a></td>
<td class="nump">7<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockholdersEquityAbstract', window );"><strong>Stockholders' equity (deficit):</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommonStockValue', window );">Common stock</a></td>
<td class="nump">7<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AdditionalPaidInCapitalCommonStock', window );">Additional paid-in capital</a></td>
<td class="nump">119,521<span></span>
</td>
<td class="nump">2,151<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax', window );">Accumulated other comprehensive income</a></td>
<td class="nump">23<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RetainedEarningsAccumulatedDeficit', window );">Accumulated deficit</a></td>
<td class="num">(90,110)<span></span>
</td>
<td class="num">(79,237)<span></span>
</td>
</tr>
<tr class="reu">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockholdersEquity', window );">Total stockholders' equity (deficit)</a></td>
<td class="nump">29,441<span></span>
</td>
<td class="num">(77,086)<span></span>
</td>
</tr>
<tr class="rou">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesAndStockholdersEquity', window );">Total liabilities, convertible preferred stock, redeemable common stock and stockholders' equity (deficit)</a></td>
<td class="nump">$ 62,549<span></span>
</td>
<td class="nump">9,944<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=us-gaap_ConvertiblePreferredStockMember', window );">Convertible Preferred Stock [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesCurrentAbstract', window );"><strong>Current liabilities:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityCarryingAmountAttributableToParent', window );">Convertible preferred stock (Series Seed, A and B), $0.001 par value;10,000,000 and 59,413,523 shares authorized as of March 31, 2019 and December 31, 2018, respectively; 0 and 40,079,567 shares issued and outstanding as of March 31, 2019 and December 31, 2018, respectively</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">64,675<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_RedeemableCommonStockMember', window );">Redeemable Common Stock [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesCurrentAbstract', window );"><strong>Current liabilities:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommonStockValue', window );">Common stock</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">734<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockholdersEquityAbstract', window );"><strong>Stockholders' equity (deficit):</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommonStockValue', window );">Common stock</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">734<span></span>
</td>
</tr>
<tr class="reu">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockholdersEquity', window );">Total stockholders' equity (deficit)</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 734<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_AccountsPayableCurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.19(a))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AccountsPayableCurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_AccruedLiabilitiesCurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.20)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AccruedLiabilitiesCurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 11<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=d3e637-108580<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 14A<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669686-108580<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 14<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=d3e681-108580<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_AdditionalPaidInCapitalCommonStock">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Value received from shareholders in common stock-related transactions that are in excess of par value or stated value and amounts received from other stock-related transactions. Includes only common stock transactions (excludes preferred stock transactions). May be called contributed capital, capital in excess of par, capital surplus, or paid-in capital.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(30)(a)(1))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AdditionalPaidInCapitalCommonStock</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_Assets">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 942<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.9-03(11))<br> -URI http://asc.fasb.org/extlink&amp;oid=6876686&amp;loc=d3e534808-122878<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 280<br> -SubTopic 10<br> -Section 50<br> -Paragraph 22<br> -URI http://asc.fasb.org/extlink&amp;oid=115929826&amp;loc=d3e8736-108599<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 944<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.7-03(a)(12))<br> -URI http://asc.fasb.org/extlink&amp;oid=6879938&amp;loc=d3e572229-122910<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_Assets</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Data Type:</strong></td>
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</tr>
<tr>
<td><strong> Balance Type:</strong></td>
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</tr>
<tr>
<td><strong> Period Type:</strong></td>
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</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_AssetsCurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Sum of the carrying amounts as of the balance sheet date of all assets that are expected to be realized in cash, sold, or consumed within one year (or the normal operating cycle, if longer). Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section 45<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=82887183&amp;loc=d3e6801-107765<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.9)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=82887183&amp;loc=d3e6676-107765<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AssetsCurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
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<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_AssetsCurrentAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AssetsCurrentAbstract</td>
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<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CashAndCashEquivalentsAtCarryingValue">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 4<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3044-108585<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=82887183&amp;loc=d3e6676-107765<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.1)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CashAndCashEquivalentsAtCarryingValue</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CommitmentsAndContingencies">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Represents the caption on the face of the balance sheet to indicate that the entity has entered into (1) purchase or supply arrangements that will require expending a portion of its resources to meet the terms thereof, and (2) is exposed to potential losses or, less frequently, gains, arising from (a) possible claims against a company's resources due to future performance under contract terms, and (b) possible losses or likely gains from uncertainties that will ultimately be resolved when one or more future events that are deemed likely to occur do occur or fail to occur.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.25)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 944<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.7-03.(a),19)<br> -URI http://asc.fasb.org/extlink&amp;oid=6879938&amp;loc=d3e572229-122910<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 942<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.9-03.17)<br> -URI http://asc.fasb.org/extlink&amp;oid=6876686&amp;loc=d3e534808-122878<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 450<br> -SubTopic 20<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=82911808&amp;loc=d3e14326-108349<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CommitmentsAndContingencies</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CommonStockValue">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Aggregate par or stated value of issued nonredeemable common stock (or common stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable common shares, par value and other disclosure concepts are in another section within stockholders' equity.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CommonStockValue</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DeferredRentCreditNoncurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>For a classified balance sheet, the cumulative difference between the rental income or payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense, by the lessor or lessee, respectively, more than one year after the balance sheet date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.26(c))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 840<br> -SubTopic 20<br> -Section 25<br> -Paragraph 2<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=77902458&amp;loc=d3e39927-112707<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DeferredRentCreditNoncurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_Goodwill">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 350<br> -SubTopic 20<br> -Section 45<br> -Paragraph 5<br> -URI http://asc.fasb.org/extlink&amp;oid=77989000&amp;loc=SL49117168-202975<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 350<br> -SubTopic 20<br> -Section 45<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=99380562&amp;loc=d3e13770-109266<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_Goodwill</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_IntangibleAssetsNetExcludingGoodwill">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 350<br> -SubTopic 30<br> -Section 50<br> -Paragraph 2<br> -Subparagraph ((a)(1),(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=66006027&amp;loc=d3e16323-109275<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 350<br> -SubTopic 30<br> -Section 45<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6388964&amp;loc=d3e16212-109274<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_IntangibleAssetsNetExcludingGoodwill</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_Liabilities">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Sum of the carrying amounts as of the balance sheet date of all liabilities that are recognized. Liabilities are probable future sacrifices of economic benefits arising from present obligations of an entity to transfer assets or provide services to other entities in the future.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.19-26)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_Liabilities</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of liabilities and equity items, including the portion of equity attributable to noncontrolling interests, if any.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 942<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.9-03(23))<br> -URI http://asc.fasb.org/extlink&amp;oid=6876686&amp;loc=d3e534808-122878<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 944<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.7-03(a)(25))<br> -URI http://asc.fasb.org/extlink&amp;oid=6879938&amp;loc=d3e572229-122910<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(32))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LiabilitiesAndStockholdersEquity</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LiabilitiesCurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Total obligations incurred as part of normal operations that are expected to be paid during the following twelve months or within one business cycle, if longer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.21)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LiabilitiesCurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LiabilitiesCurrentAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LiabilitiesCurrentAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LongTermDebtCurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.19,20)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LongTermDebtCurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeaseLiabilityCurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 45<br> -Paragraph 1<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888419&amp;loc=SL77918627-209977<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeaseLiabilityCurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeaseLiabilityNoncurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Present value of lessee's discounted obligation for lease payments from operating lease, classified as noncurrent.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 45<br> -Paragraph 1<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888419&amp;loc=SL77918627-209977<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeaseLiabilityNoncurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeaseRightOfUseAsset">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of lessee's right to use underlying asset under operating lease.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 45<br> -Paragraph 1<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888419&amp;loc=SL77918627-209977<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeaseRightOfUseAsset</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OtherAssetsNoncurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of noncurrent assets classified as other.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.17)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OtherAssetsNoncurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OtherLiabilitiesNoncurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of liabilities classified as other, due after one year or the normal operating cycle, if longer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.24)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OtherLiabilitiesNoncurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_PrepaidExpenseAndOtherAssetsCurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of asset related to consideration paid in advance for costs that provide economic benefits in future periods, and amount of other assets that are expected to be realized or consumed within one year or the normal operating cycle, if longer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(7))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=82887183&amp;loc=d3e6676-107765<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(8))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PrepaidExpenseAndOtherAssetsCurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_PropertyPlantAndEquipmentNet">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(14))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 360<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6391035&amp;loc=d3e2868-110229<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 944<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.7-03(a)(8))<br> -URI http://asc.fasb.org/extlink&amp;oid=6879938&amp;loc=d3e572229-122910<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(13))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PropertyPlantAndEquipmentNet</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_RestrictedCashNoncurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of cash restricted as to withdrawal or usage, classified as noncurrent. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section 45<br> -Paragraph 4<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=82887183&amp;loc=d3e6812-107765<br><br>Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(17))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 50<br> -Paragraph 8<br> -URI http://asc.fasb.org/extlink&amp;oid=98513485&amp;loc=SL98516268-108586<br><br>Reference 4: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 954<br> -SubTopic 305<br> -Section 45<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=84242212&amp;loc=d3e2352-115587<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_RestrictedCashNoncurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_RetainedEarningsAccumulatedDeficit">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The cumulative amount of the reporting entity's undistributed earnings or deficit.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(30)(a)(3))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 944<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.7-03(a)(23)(a)(4))<br> -URI http://asc.fasb.org/extlink&amp;oid=6879938&amp;loc=d3e572229-122910<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_RetainedEarningsAccumulatedDeficit</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockholdersEquity">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 310<br> -SubTopic 10<br> -Section S99<br> -Paragraph 2<br> -Subparagraph (SAB Topic 4.E)<br> -URI http://asc.fasb.org/extlink&amp;oid=27010918&amp;loc=d3e74512-122707<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(31))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(30))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockholdersEquity</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockholdersEquityAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockholdersEquityAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TemporaryEquityCarryingAmountAttributableToParent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Carrying amount, attributable to parent, of an entity's issued and outstanding stock which is not included within permanent equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. Includes stock with a put option held by an ESOP and stock redeemable by a holder only in the event of a change in control of the issuer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquityCarryingAmountAttributableToParent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_LongTermDebtNonCurrentIncludingAccretion">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Long term debt non current including accretion.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_LongTermDebtNonCurrentIncludingAccretion</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_PreferredStockWarrantLiability">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Preferred Stock Warrant Liability</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_PreferredStockWarrantLiability</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ResearchAndDevelopmentIncentiveReceivable">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Research and development incentive receivable.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ResearchAndDevelopmentIncentiveReceivable</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StatementClassOfStockAxis=us-gaap_ConvertiblePreferredStockMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementClassOfStockAxis=us-gaap_ConvertiblePreferredStockMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StatementClassOfStockAxis=xfor_RedeemableCommonStockMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementClassOfStockAxis=xfor_RedeemableCommonStockMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6837522496">
<tr>
<th class="tl" colspan="1" rowspan="1"><div style="width: 200px;"><strong>CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares<br></strong></div></th>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Dec. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesAuthorized', window );">Convertible preferred stock, shares authorized</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">49,413,523<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesIssued', window );">Convertible preferred stock, shares issued</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">40,079,567<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesOutstanding', window );">Convertible preferred stock, shares outstanding</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">40,079,567<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommonStockParOrStatedValuePerShare', window );">Common stock, par value</a></td>
<td class="nump">$ 0.001<span></span>
</td>
<td class="nump">$ 0.001<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommonStockSharesAuthorized', window );">Common stock, shares authorized</a></td>
<td class="nump">33,333,333<span></span>
</td>
<td class="nump">11,070,776<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommonStockSharesIssued', window );">Common stock, shares issued</a></td>
<td class="nump">6,724,511<span></span>
</td>
<td class="nump">351,652<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommonStockSharesOutstanding', window );">Common stock, shares outstanding</a></td>
<td class="nump">6,724,511<span></span>
</td>
<td class="nump">351,652<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=us-gaap_ConvertiblePreferredStockMember', window );">Convertible Preferred Stock [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityParOrStatedValuePerShare', window );">Convertible preferred stock, par or stated value per share</a></td>
<td class="nump">$ 0.001<span></span>
</td>
<td class="nump">$ 0.001<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesAuthorized', window );">Convertible preferred stock, shares authorized</a></td>
<td class="nump">10,000,000<span></span>
</td>
<td class="nump">59,413,523<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesIssued', window );">Convertible preferred stock, shares issued</a></td>
<td class="nump">0<span></span>
</td>
<td class="nump">40,079,567<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesOutstanding', window );">Convertible preferred stock, shares outstanding</a></td>
<td class="nump">0<span></span>
</td>
<td class="nump">40,079,567<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_RedeemableCommonStockMember', window );">Redeemable Common Stock [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommonStockParOrStatedValuePerShare', window );">Common stock, par value</a></td>
<td class="nump">$ 0.001<span></span>
</td>
<td class="nump">$ 0.001<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommonStockSharesIssued', window );">Common stock, shares issued</a></td>
<td class="nump">0<span></span>
</td>
<td class="nump">107,364<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommonStockSharesOutstanding', window );">Common stock, shares outstanding</a></td>
<td class="nump">0<span></span>
</td>
<td class="nump">107,364<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CommonStockParOrStatedValuePerShare">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Face amount or stated value per share of common stock.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CommonStockParOrStatedValuePerShare</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CommonStockSharesAuthorized">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The maximum number of common shares permitted to be issued by an entity's charter and bylaws.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CommonStockSharesAuthorized</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CommonStockSharesIssued">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CommonStockSharesIssued</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CommonStockSharesOutstanding">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21463-112644<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CommonStockSharesOutstanding</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TemporaryEquityParOrStatedValuePerShare">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Per share amount of par value or stated value of stock classified as temporary equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 480<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=65877616&amp;loc=d3e177068-122764<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (27)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquityParOrStatedValuePerShare</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TemporaryEquitySharesAuthorized">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The maximum number of securities classified as temporary equity that are permitted to be issued by an entity's charter and bylaws. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(27)(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquitySharesAuthorized</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TemporaryEquitySharesIssued">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The number of securities classified as temporary equity that have been sold (or granted) to the entity's shareholders. Securities issued include securities outstanding and securities held in treasury. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(27)(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquitySharesIssued</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TemporaryEquitySharesOutstanding">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The number of securities classified as temporary equity that have been issued and are held by the entity's shareholders. Securities outstanding equals securities issued minus securities held in treasury. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(27)(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquitySharesOutstanding</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StatementClassOfStockAxis=us-gaap_ConvertiblePreferredStockMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementClassOfStockAxis=us-gaap_ConvertiblePreferredStockMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StatementClassOfStockAxis=xfor_RedeemableCommonStockMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementClassOfStockAxis=xfor_RedeemableCommonStockMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6836241312">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th" colspan="2">3 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Mar. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingExpensesAbstract', window );"><strong>Operating expenses:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ResearchAndDevelopmentExpense', window );">Research and development</a></td>
<td class="nump">$ 5,655<span></span>
</td>
<td class="nump">$ 4,744<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_GeneralAndAdministrativeExpense', window );">General and administrative</a></td>
<td class="nump">4,783<span></span>
</td>
<td class="nump">1,366<span></span>
</td>
</tr>
<tr class="rou">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingExpenses', window );">Total operating expenses</a></td>
<td class="nump">10,438<span></span>
</td>
<td class="nump">6,110<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingIncomeLoss', window );">Loss from operations</a></td>
<td class="num">(10,438)<span></span>
</td>
<td class="num">(6,110)<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NonoperatingIncomeExpenseAbstract', window );"><strong>Other income (expense):</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_InvestmentIncomeInterest', window );">Interest income</a></td>
<td class="nump">69<span></span>
</td>
<td class="nump">69<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_InterestExpense', window );">Interest expense</a></td>
<td class="num">(399)<span></span>
</td>
<td class="num">(169)<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueAdjustmentOfWarrants', window );">Change in fair value of preferred stock warrant liability</a></td>
<td class="num">(288)<span></span>
</td>
<td class="num">(592)<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DerivativeGainLossOnDerivativeNet', window );">Change in fair value of derivative liability</a></td>
<td class="nump">183<span></span>
</td>
<td class="num">(565)<span></span>
</td>
</tr>
<tr class="reu">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NonoperatingIncomeExpense', window );">Total other income (expense), net</a></td>
<td class="num">(435)<span></span>
</td>
<td class="num">(1,257)<span></span>
</td>
</tr>
<tr class="rou">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NetIncomeLoss', window );">Net loss</a></td>
<td class="num">(10,873)<span></span>
</td>
<td class="num">(7,367)<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityDividendsAdjustment', window );">Accruing dividends on Series A convertible preferred stock</a></td>
<td class="num">(592)<span></span>
</td>
<td class="num">(740)<span></span>
</td>
</tr>
<tr class="rou">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic', window );">Net loss attributable to common stockholders</a></td>
<td class="num">$ (11,465)<span></span>
</td>
<td class="num">$ (8,107)<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_EarningsPerShareBasicAndDiluted', window );">Net loss per share attributable to common stockholders-basic and diluted</a></td>
<td class="num">$ (6.67)<span></span>
</td>
<td class="num">$ (17.70)<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted', window );">Weighted average common shares outstanding-basic and diluted</a></td>
<td class="nump">1,717,808<span></span>
</td>
<td class="nump">457,971<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DerivativeGainLossOnDerivativeNet">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 815<br> -SubTopic 10<br> -Section 50<br> -Paragraph 4A<br> -Subparagraph (b)(1)<br> -URI http://asc.fasb.org/extlink&amp;oid=109980867&amp;loc=SL5618551-113959<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DerivativeGainLossOnDerivativeNet</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_EarningsPerShareBasicAndDiluted">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements.  Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period.  Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 260<br> -SubTopic 10<br> -Section 45<br> -Paragraph 7<br> -URI http://asc.fasb.org/extlink&amp;oid=109260490&amp;loc=d3e1337-109256<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_EarningsPerShareBasicAndDiluted</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_FairValueAdjustmentOfWarrants">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of expense (income) related to adjustment to fair value of warrant liability.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 28<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3602-108585<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 480<br> -SubTopic 10<br> -Section 25<br> -Paragraph 13<br> -URI http://asc.fasb.org/extlink&amp;oid=109262497&amp;loc=d3e20148-110875<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FairValueAdjustmentOfWarrants</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_GeneralAndAdministrativeExpense">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section S99<br> -Paragraph 2<br> -Subparagraph (SX 210.5-03.4)<br> -URI http://asc.fasb.org/extlink&amp;oid=115205541&amp;loc=SL114868664-224227<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_GeneralAndAdministrativeExpense</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_InterestExpense">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of the cost of borrowed funds accounted for as interest expense.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 835<br> -SubTopic 20<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=6450988&amp;loc=d3e26243-108391<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 835<br> -SubTopic 30<br> -Section 45<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=114775744&amp;loc=d3e28555-108399<br><br>Reference 3: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 280<br> -SubTopic 10<br> -Section 50<br> -Paragraph 22<br> -Subparagraph (d)<br> -URI http://asc.fasb.org/extlink&amp;oid=115929826&amp;loc=d3e8736-108599<br><br>Reference 4: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section S99<br> -Paragraph 2<br> -Subparagraph (210.5-03(11))<br> -URI http://asc.fasb.org/extlink&amp;oid=115205541&amp;loc=SL114868664-224227<br><br>Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 942<br> -SubTopic 220<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.9-04.9)<br> -URI http://asc.fasb.org/extlink&amp;oid=114873765&amp;loc=SL114874048-224260<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_InterestExpense</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_InvestmentIncomeInterest">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section S99<br> -Paragraph 2<br> -Subparagraph (SX 210.5-03.7(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=115205541&amp;loc=SL114868664-224227<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 280<br> -SubTopic 10<br> -Section 50<br> -Paragraph 22<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=115929826&amp;loc=d3e8736-108599<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_InvestmentIncomeInterest</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_NetIncomeLoss">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1A<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669619-108580<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 942<br> -SubTopic 220<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.9-04(22))<br> -URI http://asc.fasb.org/extlink&amp;oid=114873765&amp;loc=SL114874048-224260<br><br>Reference 3: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1B<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669625-108580<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 944<br> -SubTopic 220<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.7-04(18))<br> -URI http://asc.fasb.org/extlink&amp;oid=114873790&amp;loc=SL114874131-224263<br><br>Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section S99<br> -Paragraph 2<br> -Subparagraph (SX 210.5-03(20))<br> -URI http://asc.fasb.org/extlink&amp;oid=115205541&amp;loc=SL114868664-224227<br><br>Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 28<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3602-108585<br><br>Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 260<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6371337&amp;loc=d3e3550-109257<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_NetIncomeLoss</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 250<br> -SubTopic 10<br> -Section 50<br> -Paragraph 11<br> -URI http://asc.fasb.org/extlink&amp;oid=109234566&amp;loc=d3e22694-107794<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 260<br> -SubTopic 10<br> -Section 45<br> -Paragraph 11<br> -URI http://asc.fasb.org/extlink&amp;oid=109260490&amp;loc=d3e1377-109256<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_NonoperatingIncomeExpense">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The aggregate amount of income or expense from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section S99<br> -Paragraph 2<br> -Subparagraph (SX 210.5-03.7)<br> -URI http://asc.fasb.org/extlink&amp;oid=115205541&amp;loc=SL114868664-224227<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_NonoperatingIncomeExpense</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_NonoperatingIncomeExpenseAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_NonoperatingIncomeExpenseAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly related to production and included in cost of sales or services. Includes selling, general and administrative expense.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingExpenses</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Period Type:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingExpensesAbstract</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The net result for the period of deducting operating expenses from operating revenues.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingIncomeLoss</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 985<br> -SubTopic 20<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6501960&amp;loc=d3e128462-111756<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 730<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6420194&amp;loc=d3e21568-108373<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ResearchAndDevelopmentExpense</td>
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<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Balance Type:</strong></td>
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<td><strong> Period Type:</strong></td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TemporaryEquityDividendsAdjustment">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Accretion of temporary equity during the period due to cash, stock, and in-kind dividends. This item is an adjustment to net income necessary to derive net income apportioned to common stockholders and is to be distinguished from Temporary Equity, Accretion of Dividends (Temporary Equity, Accretion of Dividends).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquityDividendsAdjustment</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Balance Type:</strong></td>
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<td><strong> Period Type:</strong></td>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6813407072">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th" colspan="2">3 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Mar. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract', window );"><strong>Statement of Comprehensive Income [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
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</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NetIncomeLoss', window );">Net loss</a></td>
<td class="num">$ (10,873)<span></span>
</td>
<td class="num">$ (7,367)<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract', window );"><strong>Other comprehensive gain</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
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</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax', window );">Currency translation adjustments</a></td>
<td class="nump">23<span></span>
</td>
<td class="nump">0<span></span>
</td>
</tr>
<tr class="reu">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ComprehensiveIncomeNetOfTax', window );">Total comprehensive loss</a></td>
<td class="num">$ (10,850)<span></span>
</td>
<td class="num">$ (7,367)<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ComprehensiveIncomeNetOfTax">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 5<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=d3e557-108580<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1B<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669625-108580<br><br>Reference 3: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1A<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669619-108580<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ComprehensiveIncomeNetOfTax</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
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<td><strong> Balance Type:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1A<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669619-108580<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 942<br> -SubTopic 220<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.9-04(22))<br> -URI http://asc.fasb.org/extlink&amp;oid=114873765&amp;loc=SL114874048-224260<br><br>Reference 3: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1B<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669625-108580<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 944<br> -SubTopic 220<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.7-04(18))<br> -URI http://asc.fasb.org/extlink&amp;oid=114873790&amp;loc=SL114874131-224263<br><br>Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section S99<br> -Paragraph 2<br> -Subparagraph (SX 210.5-03(20))<br> -URI http://asc.fasb.org/extlink&amp;oid=115205541&amp;loc=SL114868664-224227<br><br>Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 28<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3602-108585<br><br>Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 260<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6371337&amp;loc=d3e3550-109257<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_NetIncomeLoss</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
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<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
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<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 10A<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669646-108580<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 830<br> -SubTopic 30<br> -Section 45<br> -Paragraph 20<br> -Subparagraph (b,c)<br> -URI http://asc.fasb.org/extlink&amp;oid=109240241&amp;loc=d3e32211-110900<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax</td>
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<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Data Type:</strong></td>
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<td><strong> Balance Type:</strong></td>
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<td><strong> Period Type:</strong></td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<td style="white-space:nowrap;">us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<DOCUMENT>
<TYPE>XML
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<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6838638304">
<tr>
<th class="tl" colspan="1" rowspan="1"><div style="width: 200px;"><strong>CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK, REDEEMABLE COMMON STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Unaudited) - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th"><div>Total</div></th>
<th class="th"><div>Redeemable Common Stock [Member]</div></th>
<th class="th"><div>Convertible Preferred Shares [Member]</div></th>
<th class="th"><div>Common Stock [Member]</div></th>
<th class="th"><div>Additional Paid-in Capital [Member]</div></th>
<th class="th"><div>Accumulated Other Comprehensive Income [Member]</div></th>
<th class="th"><div>Accumulated Deficit [Member]</div></th>
</tr>
<tr class="rc">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockholdersEquity', window );">Beginning balance at Dec. 31, 2017</a></td>
<td class="num">$ (44,545)<span></span>
</td>
<td class="nump">$ 734<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 1,385<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="num">$ (45,930)<span></span>
</td>
</tr>
<tr class="rc">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityCarryingAmountAttributableToParent', window );">Convertible preferred shares, beginning balance at Dec. 31, 2017</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 60,903<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rc">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SharesOutstanding', window );">Beginning balance, shares at Dec. 31, 2017</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">107,364<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">350,607<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rc">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesOutstanding', window );">Convertible preferred shares, beginning balance, shares at Dec. 31, 2017</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">38,018,968<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodSharesNewIssues', window );">Repurchase of Series Seed convertible preferred stock</a></td>
<td class="num">(22,000)<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="num">(22,000)<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStock', window );">Repurchase of Series Seed convertible preferred stock, net of issuance costs of $1</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="num">$ (517)<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodValueNewIssues', window );">Repurchase of Series Seed convertible preferred stock, share</a></td>
<td class="nump">$ 0<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
<td class="nump">0<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStockShare', window );">Repurchase of Series Seed convertible preferred stock, net of issuance costs of $1, share</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="num">(598,975)<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rc">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityCarryingAmountAttributableToParent', window );">Convertible preferred shares, ending balance at Mar. 31, 2018</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 60,386<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rc">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesOutstanding', window );">Convertible preferred shares, ending balance, shares at Mar. 31, 2018</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">37,419,993<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue', window );">Stock-based compensation expense</a></td>
<td class="nump">128<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">128<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ComprehensiveIncomeNetOfTax', window );">Net loss</a></td>
<td class="num">(7,367)<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NetIncomeLoss', window );">Net loss</a></td>
<td class="num">(7,367)<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="num">(7,367)<span></span>
</td>
</tr>
<tr class="rc">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockholdersEquity', window );">Ending balance at Mar. 31, 2018</a></td>
<td class="num">(51,806)<span></span>
</td>
<td class="nump">$ 734<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">1,513<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="num">(53,319)<span></span>
</td>
</tr>
<tr class="rc">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SharesOutstanding', window );">Ending balance, shares at Mar. 31, 2018</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">107,364<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">350,607<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rc">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockholdersEquity', window );">Beginning balance at Dec. 31, 2018</a></td>
<td class="num">(77,086)<span></span>
</td>
<td class="nump">$ 734<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">2,151<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="num">(79,237)<span></span>
</td>
</tr>
<tr class="rc">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityCarryingAmountAttributableToParent', window );">Convertible preferred shares, beginning balance at Dec. 31, 2018</a></td>
<td class="nump">$ 64,675<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 64,675<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rc">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SharesOutstanding', window );">Beginning balance, shares at Dec. 31, 2018</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">107,364<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">351,652<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rc">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesOutstanding', window );">Convertible preferred shares, beginning balance, shares at Dec. 31, 2018</a></td>
<td class="nump">40,079,567<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">40,079,567<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ConversionOfRedeemableCommonStockToCommonStockValue', window );">Conversion of redeemable common stock into common stock</a></td>
<td class="nump">$ 734<span></span>
</td>
<td class="num">$ (734)<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 1<span></span>
</td>
<td class="nump">733<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ConversionOfRedeemableCommonStockToCommonStockShares', window );">Conversion of redeemable common stock into common stock, shares</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="num">(107,364)<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">107,364<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities', window );">Conversion of convertible preferred shares into common stock</a></td>
<td class="nump">64,675<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="num">$ (64,675)<span></span>
</td>
<td class="nump">$ 4<span></span>
</td>
<td class="nump">64,671<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities', window );">Conversion of convertible preferred shares into common stock, shares</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="num">(40,079,567)<span></span>
</td>
<td class="nump">3,808,430<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodValueAcquisitions', window );">Exchange of common stock in connection with Merger</a></td>
<td class="nump">45,541<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 2<span></span>
</td>
<td class="nump">45,539<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodSharesAcquisitions', window );">Exchange of common stock in connection with Merger, shares</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">2,440,582<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AdjustmentsToAdditionalPaidInCapitalMarkToMarket', window );">Fair value of replacement equity awards</a></td>
<td class="nump">817<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">817<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_AdjustmentToAdditionalPaidInCapitalReclassificationOfWarrantLiabilityToPermanentEquity', window );">Reclassification of warrant liability to permanent equity</a></td>
<td class="nump">5,235<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">5,235<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised', window );">Exercise of stock options</a></td>
<td class="nump">$ 113<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">113<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised', window );">Exercise of stock options, shares</a></td>
<td class="nump">16,483<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">16,483<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue', window );">Stock-based compensation expense</a></td>
<td class="nump">$ 262<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">262<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ComprehensiveIncomeNetOfTax', window );">Net loss</a></td>
<td class="num">(10,850)<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">23<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NetIncomeLoss', window );">Net loss</a></td>
<td class="num">(10,873)<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="num">(10,873)<span></span>
</td>
</tr>
<tr class="rc">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockholdersEquity', window );">Ending balance at Mar. 31, 2019</a></td>
<td class="nump">$ 29,441<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 7<span></span>
</td>
<td class="nump">$ 119,521<span></span>
</td>
<td class="nump">$ 23<span></span>
</td>
<td class="num">$ (90,110)<span></span>
</td>
</tr>
<tr class="rc">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SharesOutstanding', window );">Ending balance, shares at Mar. 31, 2019</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">6,724,511<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_AdjustmentsToAdditionalPaidInCapitalMarkToMarket">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of increase (decrease) to additional paid in capital (APIC) resulting from changes in fair value of common and preferred stock issued to employee benefit trust but unearned.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21463-112644<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AdjustmentsToAdditionalPaidInCapitalMarkToMarket</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of increase to additional paid-in capital (APIC) from recognition of equity-based compensation.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 20<br> -Section 55<br> -Paragraph 12<br> -URI http://asc.fasb.org/extlink&amp;oid=109196918&amp;loc=d3e11149-113907<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5047-113901<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 20<br> -Section 55<br> -Paragraph 13<br> -URI http://asc.fasb.org/extlink&amp;oid=109196918&amp;loc=d3e11178-113907<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 35<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=79507207&amp;loc=d3e4534-113899<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ComprehensiveIncomeNetOfTax">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 5<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=d3e557-108580<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1B<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669625-108580<br><br>Reference 3: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1A<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669619-108580<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ComprehensiveIncomeNetOfTax</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_NetIncomeLoss">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1A<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669619-108580<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 942<br> -SubTopic 220<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.9-04(22))<br> -URI http://asc.fasb.org/extlink&amp;oid=114873765&amp;loc=SL114874048-224260<br><br>Reference 3: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1B<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669625-108580<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 944<br> -SubTopic 220<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.7-04(18))<br> -URI http://asc.fasb.org/extlink&amp;oid=114873790&amp;loc=SL114874131-224263<br><br>Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section S99<br> -Paragraph 2<br> -Subparagraph (SX 210.5-03(20))<br> -URI http://asc.fasb.org/extlink&amp;oid=115205541&amp;loc=SL114868664-224227<br><br>Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 28<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3602-108585<br><br>Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 260<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6371337&amp;loc=d3e3550-109257<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_NetIncomeLoss</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_SharesOutstanding">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of shares issued which are neither cancelled nor held in the treasury.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_SharesOutstanding</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockIssuedDuringPeriodSharesAcquisitions">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of shares of stock issued during the period pursuant to acquisitions.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(28))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockIssuedDuringPeriodSharesAcquisitions</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of shares issued during the period as a result of the conversion of convertible securities.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.29-30)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21475-112644<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21463-112644<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockIssuedDuringPeriodSharesNewIssues">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of new stock issued during the period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21463-112644<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(28))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockIssuedDuringPeriodSharesNewIssues</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of share options (or share units) exercised during the current period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (c)(1)(iv)(2)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(28))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21463-112644<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockIssuedDuringPeriodValueAcquisitions">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Value of stock issued pursuant to acquisitions during the period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21463-112644<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.29-31)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockIssuedDuringPeriodValueAcquisitions</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The gross value of stock issued during the period upon the conversion of convertible securities.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21463-112644<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.29-31)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockIssuedDuringPeriodValueNewIssues">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21463-112644<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(28))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockIssuedDuringPeriodValueNewIssues</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Value of stock issued as a result of the exercise of stock options.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21463-112644<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.29-31)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockholdersEquity">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 310<br> -SubTopic 10<br> -Section S99<br> -Paragraph 2<br> -Subparagraph (SAB Topic 4.E)<br> -URI http://asc.fasb.org/extlink&amp;oid=27010918&amp;loc=d3e74512-122707<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(31))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(30))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockholdersEquity</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TemporaryEquityCarryingAmountAttributableToParent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Carrying amount, attributable to parent, of an entity's issued and outstanding stock which is not included within permanent equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. Includes stock with a put option held by an ESOP and stock redeemable by a holder only in the event of a change in control of the issuer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquityCarryingAmountAttributableToParent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TemporaryEquitySharesOutstanding">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The number of securities classified as temporary equity that have been issued and are held by the entity's shareholders. Securities outstanding equals securities issued minus securities held in treasury. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(27)(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquitySharesOutstanding</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_AdjustmentToAdditionalPaidInCapitalReclassificationOfWarrantLiabilityToPermanentEquity">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Adjustment to additional paid in capital reclassification of warrant liability to permanent equity.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_AdjustmentToAdditionalPaidInCapitalReclassificationOfWarrantLiabilityToPermanentEquity</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ConversionOfRedeemableCommonStockToCommonStockShares">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Conversion of redeemable common stock to common stock shares.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ConversionOfRedeemableCommonStockToCommonStockShares</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ConversionOfRedeemableCommonStockToCommonStockValue">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Conversion of redeemable common stock to common stock value.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ConversionOfRedeemableCommonStockToCommonStockValue</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStock">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Temporary equity repurchase of convertible preferred stock.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStock</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStockShare">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Temporary equity repurchase of convertible preferred share.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_TemporaryEquityRepurchaseOfConvertiblePreferredStockShare</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
</div>
</body>
</html>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>XML
<SEQUENCE>23
<FILENAME>R7.htm
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
<script type="text/javascript" src="Show.js">/* Do Not Remove This Comment */</script><script type="text/javascript">
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</head>
<body>
<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6827332768">
<tr>
<th class="tl" colspan="1" rowspan="1"><div style="width: 200px;"><strong>CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK, REDEEMABLE COMMON STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Unaudited) (Parenthetical)<br> $ in Thousands</strong></div></th>
<th class="th">
<div>Mar. 31, 2018 </div>
<div>USD ($)</div>
</th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementOfStockholdersEquityAbstract', window );"><strong>Statement of Stockholders' Equity [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_PreferredStockIssuanceCosts', window );">Net of issuance costs</a></td>
<td class="nump">$ 1<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StatementOfStockholdersEquityAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementOfStockholdersEquityAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_PreferredStockIssuanceCosts">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Preferred Stock Issuance Costs</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_PreferredStockIssuanceCosts</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
</div>
</body>
</html>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>XML
<SEQUENCE>24
<FILENAME>R8.htm
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
<script type="text/javascript" src="Show.js">/* Do Not Remove This Comment */</script><script type="text/javascript">
							function toggleNextSibling (e) {
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							e.nextSibling.style.display='block';
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							}</script>
</head>
<body>
<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6837317376">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th" colspan="2">3 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Mar. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract', window );"><strong>Cash flows from operating activities:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ProfitLoss', window );">Net loss</a></td>
<td class="num">$ (10,873)<span></span>
</td>
<td class="num">$ (7,367)<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract', window );"><strong>Adjustments to reconcile net loss to net cash used in operating activities:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensation', window );">Stock-based compensation expense</a></td>
<td class="nump">262<span></span>
</td>
<td class="nump">128<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DepreciationDepletionAndAmortization', window );">Depreciation expense</a></td>
<td class="nump">20<span></span>
</td>
<td class="nump">26<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_NonCashLeaseExpense', window );">Non-cash lease expense</a></td>
<td class="nump">119<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_NonCashInterestExpense', window );">Non-cash interest expense</a></td>
<td class="nump">153<span></span>
</td>
<td class="nump">27<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ChangeInFairValueOfConvertiblePreferredStockWarrantLiability', window );">Change in fair value of preferred stock warrant liability</a></td>
<td class="nump">288<span></span>
</td>
<td class="nump">592<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DerivativeGainLossOnDerivativeNet', window );">Change in fair value of derivative liability</a></td>
<td class="num">(183)<span></span>
</td>
<td class="nump">565<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract', window );"><strong>Changes in operating assets and liabilities:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets', window );">Prepaid expenses and other current assets</a></td>
<td class="num">(595)<span></span>
</td>
<td class="nump">170<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_IncreaseDecreaseInAccountsPayable', window );">Accounts payable</a></td>
<td class="nump">1,332<span></span>
</td>
<td class="num">(563)<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_IncreaseDecreaseInAccruedLiabilities', window );">Accrued expenses</a></td>
<td class="num">(2,072)<span></span>
</td>
<td class="nump">240<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_IncreaseDecreaseInOperatingLeaseLiabilities', window );">Operating lease liabilities</a></td>
<td class="num">(201)<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="reu">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NetCashProvidedByUsedInOperatingActivities', window );">Net cash used in operating activities</a></td>
<td class="num">(11,750)<span></span>
</td>
<td class="num">(6,182)<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract', window );"><strong>Cash flows from investing activities:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired', window );">Cash and restricted cash acquired in connection with the Merger</a></td>
<td class="nump">26,406<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NetCashProvidedByUsedInInvestingActivities', window );">Net cash provided by investing activities</a></td>
<td class="nump">26,406<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract', window );"><strong>Cash flows from financing activities:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ProceedsFromStockOptionsExercised', window );">Proceeds from exercise of stock options</a></td>
<td class="nump">113<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PaymentsForRepurchaseOfConvertiblePreferredStock', window );">Repurchase of Series Seed convertible preferred stock</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="num">(1,126)<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RepaymentsOfLongTermDebt', window );">Repayments of borrowings under loan and security agreement</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="num">(500)<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_PaymentsOfIssuanceCostsOfRedeemableConvertiblePreferredStock', window );">Payments of issuance costs of convertible preferred stock</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="num">(34)<span></span>
</td>
</tr>
<tr class="rou">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NetCashProvidedByUsedInFinancingActivities', window );">Net cash provided by (used in) financing activities</a></td>
<td class="nump">113<span></span>
</td>
<td class="num">(1,660)<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents', window );">Effect of exchange rate changes on cash, cash equivalents and restricted cash</a></td>
<td class="num">(21)<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rou">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect', window );">Net increase (decrease) in cash, cash equivalents and restricted cash</a></td>
<td class="nump">14,748<span></span>
</td>
<td class="num">(7,842)<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents', window );">Cash, cash equivalents and restricted cash at beginning of period</a></td>
<td class="nump">8,498<span></span>
</td>
<td class="nump">27,048<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents', window );">Cash, cash equivalents and restricted cash at end of period</a></td>
<td class="nump">23,246<span></span>
</td>
<td class="nump">19,206<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SupplementalCashFlowInformationAbstract', window );"><strong>Supplemental disclosure of cash flow information:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_InterestPaidNet', window );">Cash paid for interest</a></td>
<td class="nump">243<span></span>
</td>
<td class="nump">$ 146<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract', window );"><strong>Supplemental disclosure of non-cash investing and financing activities:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ConversionOfConvertiblePreferredStockToCommonStockValue', window );">Conversion of convertible preferred stock into common stock</a></td>
<td class="nump">64,675<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ConversionOfRedeemableCommonStockToCommonStockValue', window );">Conversion of redeemable common stock into common stock</a></td>
<td class="nump">734<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ConversionOfConvertiblePreferredStockWarrantsToCommonStockWarrants', window );">Conversion of convertible preferred stock warrants into common stock warrants</a></td>
<td class="nump">5,235<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_FairValueOfNetAssetsAcquiredInReverseMerger', window );">Fair value of net assets acquired in Merger</a></td>
<td class="nump">$ 46,358<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 24<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3521-108585<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 4<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3044-108585<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 50<br> -Paragraph 8<br> -URI http://asc.fasb.org/extlink&amp;oid=98513485&amp;loc=SL98516268-108586<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of increase (decrease) in cash, cash equivalents, and cash and cash equivalents restricted to withdrawal or usage; including effect from exchange rate change. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 830<br> -SubTopic 230<br> -Section 45<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=98513438&amp;loc=d3e33268-110906<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 24<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3521-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DepreciationDepletionAndAmortization">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 280<br> -SubTopic 10<br> -Section 50<br> -Paragraph 22<br> -Subparagraph (e)<br> -URI http://asc.fasb.org/extlink&amp;oid=115929826&amp;loc=d3e8736-108599<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 28<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3602-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DepreciationDepletionAndAmortization</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DerivativeGainLossOnDerivativeNet">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 815<br> -SubTopic 10<br> -Section 50<br> -Paragraph 4A<br> -Subparagraph (b)(1)<br> -URI http://asc.fasb.org/extlink&amp;oid=109980867&amp;loc=SL5618551-113959<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DerivativeGainLossOnDerivativeNet</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of increase (decrease) from effect of exchange rate changes on cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage; held in foreign currencies. Excludes amounts for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 830<br> -SubTopic 230<br> -Section 45<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=98513438&amp;loc=d3e33268-110906<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_IncreaseDecreaseInAccountsPayable">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The increase (decrease) during the reporting period in the aggregate amount of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 28<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3602-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_IncreaseDecreaseInAccountsPayable</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_IncreaseDecreaseInAccruedLiabilities">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The increase (decrease) during the reporting period in the aggregate amount of expenses incurred but not yet paid.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 28<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3602-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_IncreaseDecreaseInAccruedLiabilities</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_IncreaseDecreaseInOperatingCapitalAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of increase (decrease) in prepaid expenses, and assets classified as other.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 28<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3602-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_InterestPaidNet">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of cash paid for interest, excluding capitalized interest, classified as operating activity. Includes, but is not limited to, payment to settle zero-coupon bond for accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=98513485&amp;loc=d3e4297-108586<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 17<br> -Subparagraph (d)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3367-108585<br><br>Reference 3: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 25<br> -Subparagraph (e)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3536-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_InterestPaidNet</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_NetCashProvidedByUsedInFinancingActivities">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 24<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3521-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_NetCashProvidedByUsedInFinancingActivities</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_NetCashProvidedByUsedInInvestingActivities">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 24<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3521-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_NetCashProvidedByUsedInInvestingActivities</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_NetCashProvidedByUsedInOperatingActivities">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 25<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3536-108585<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 24<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3521-108585<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 28<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3602-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_NetCashProvidedByUsedInOperatingActivities</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_PaymentsForRepurchaseOfConvertiblePreferredStock">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The cash outflow to reacquire preferred stock originally issued and identified as a security that can be exchanged for another type of financial security. This repurchased stock is held in treasury.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 15<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3291-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PaymentsForRepurchaseOfConvertiblePreferredStock</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 13<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3213-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ProceedsFromStockOptionsExercised">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2A<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=SL79508275-113901<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 14<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3255-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ProceedsFromStockOptionsExercised</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ProfitLoss">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1A<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669619-108580<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 810<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1A<br> -Subparagraph (a)(1)<br> -URI http://asc.fasb.org/extlink&amp;oid=109239629&amp;loc=SL4573702-111684<br><br>Reference 3: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1B<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669625-108580<br><br>Reference 4: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 810<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1A<br> -Subparagraph (c)(1)<br> -URI http://asc.fasb.org/extlink&amp;oid=109239629&amp;loc=SL4573702-111684<br><br>Reference 5: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 280<br> -SubTopic 10<br> -Section 50<br> -Paragraph 22<br> -URI http://asc.fasb.org/extlink&amp;oid=115929826&amp;loc=d3e8736-108599<br><br>Reference 6: http://www.xbrl.org/2003/role/exampleRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 810<br> -SubTopic 10<br> -Section 55<br> -Paragraph 4J<br> -URI http://asc.fasb.org/extlink&amp;oid=84234705&amp;loc=SL4591551-111686<br><br>Reference 7: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3000-108585<br><br>Reference 8: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 810<br> -SubTopic 10<br> -Section 45<br> -Paragraph 19<br> -URI http://asc.fasb.org/extlink&amp;oid=108774443&amp;loc=SL4569616-111683<br><br>Reference 9: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 280<br> -SubTopic 10<br> -Section 50<br> -Paragraph 32<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=115929826&amp;loc=d3e8933-108599<br><br>Reference 10: http://www.xbrl.org/2003/role/exampleRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 810<br> -SubTopic 10<br> -Section 55<br> -Paragraph 4K<br> -URI http://asc.fasb.org/extlink&amp;oid=84234705&amp;loc=SL4591552-111686<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ProfitLoss</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 15<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3291-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_RepaymentsOfLongTermDebt</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 28<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3602-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensation</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_SupplementalCashFlowInformationAbstract</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Change in fair value of convertible preferred stock warrant liability.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ChangeInFairValueOfConvertiblePreferredStockWarrantLiability</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Balance Type:</strong></td>
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<td><strong> Period Type:</strong></td>
<td>duration</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ConversionOfConvertiblePreferredStockToCommonStockValue">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Conversion of convertible preferred stock to common stock value.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ConversionOfConvertiblePreferredStockToCommonStockValue</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Conversion of convertible preferred stock warrants to common stock warrants.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ConversionOfConvertiblePreferredStockWarrantsToCommonStockWarrants</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ConversionOfRedeemableCommonStockToCommonStockValue">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Conversion of redeemable common stock to common stock value.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Fair value of net assets acquired in reverse merger.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Increase decrease in operating lease liabilities.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_IncreaseDecreaseInOperatingLeaseLiabilities</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Non-cash interest expense.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_NonCashInterestExpense</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Non-cash lease expense.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_NonCashLeaseExpense</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
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<td><strong> Data Type:</strong></td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Payments of issuance costs of redeemable convertible preferred stock.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6827375488">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Nature of the Business and Basis of Presentation<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
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<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
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<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AccountingPoliciesAbstract', window );"><strong>Accounting Policies [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessDescriptionAndBasisOfPresentationTextBlock', window );">Nature of the Business and Basis of Presentation</a></td>
<td class="text"><div>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td valign="top" width="4%" align="left"><b>1.</b></td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"><b>Nature of the Business and Basis of
 Presentation</b></p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 X4 Pharmaceuticals, Inc. (formerly Arsanis, Inc.), together with
 its subsidiaries (the &#x201C;Company&#x201D;), is a clinical-stage
 biotechnology research and development company focused on the
 development of novel therapeutics for the treatment of rare
 diseases. The Company is headquartered in Cambridge,
 Massachusetts.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company is subject to risks and uncertainties common to
 early-stage companies in the biotechnology industry, including, but
 not limited to, development by competitors of new technological
 innovations, dependence on key personnel, protection of proprietary
 technology, compliance with governmental regulations and the
 ability to secure additional capital to fund operations. Drug
 candidates currently under development will require extensive
 preclinical and clinical testing and regulatory approval prior to
 commercialization. These efforts require significant amounts of
 additional capital, adequate personnel, and infrastructure and
 extensive compliance-reporting capabilities. Even if the
 Company&#x2019;s drug development efforts are successful, it is
 uncertain when, if ever, the Company will realize significant
 revenue from product sales.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The accompanying condensed consolidated financial statements have
 been prepared in accordance with accounting principles generally
 accepted in the United States of America (&#x201C;GAAP&#x201D;) and
 include the accounts of the Company and its wholly owned
 subsidiaries. All intercompany accounts and transactions have been
 eliminated in consolidation.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Merger with Arsanis</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 On November&#xA0;26, 2018, Arsanis, Inc., a publicly held Delaware
 corporation (&#x201C;Arsanis&#x201D;), Artemis AC Corp., a Delaware
 corporation and a wholly owned subsidiary of Arsanis (&#x201C;Merger
 Sub&#x201D;), and X4 Therapeutics, Inc. (&#x201C;X4&#x201D;) entered
 into an Agreement and Plan of Merger, as amended on
 December&#xA0;20, 2018 and March&#xA0;8, 2019 (the &#x201C;Merger
 Agreement&#x201D;), pursuant to which the Merger Sub merged with and
 into X4, with X4 surviving the merger as a wholly owned subsidiary
 of Arsanis. The transactions described in the foregoing sentence
 may be referred to in these condensed consolidated financial
 statements as &#x201C;the Merger.&#x201D;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The transaction was accounted for as a reverse merger in accordance
 with GAAP. Under this method of accounting, X4 was deemed to be the
 accounting acquirer for financial reporting purposes. This
 determination was primarily based on the facts that, immediately
 following the Merger: (i)&#xA0;the Company&#x2019;s stockholders own
 a substantial majority of the voting rights in the combined
 organization, (ii)&#xA0;the Company designated a majority of the
 members of the initial board of directors of the combined
 organization and (iii)&#xA0;the Company&#x2019;s senior management
 hold all key positions in the senior management of the combined
 organization. Accordingly, for accounting purposes, the business
 combination was treated as the equivalent of X4 issuing stock to
 acquire the net assets of Arsanis. As a result, as of the closing
 date of the Merger, the net assets of Arsanis were recorded at
 their acquisition-date fair values in the financial statements of
 the Company and the reported operating results prior to the
 business combination will be those of the Company. In addition,
 transaction costs incurred by the Company in connection with the
 business combination will be expensed as incurred.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 On March&#xA0;13, 2019, Arsanis, X4 and Merger Sub completed the
 Merger pursuant to the terms of the Merger Agreement. Pursuant to
 the terms of the Merger Agreement, each outstanding share of
 X4&#x2019;s common stock and preferred stock was exchanged for
 0.5702 shares of Arsanis&#x2019;s common stock (the &#x201C;Exchange
 Ratio&#x201D;). In addition, all outstanding options exercisable for
 common stock and warrants exercisable for convertible preferred
 stock of X4 became options and warrants exercisable for the same
 number of shares of common stock of Arsanis multiplied by the
 Exchange Ratio. In connection with the Merger, X4 changed its name
 to X4 Therapeutics, Inc. Following the closing of the Merger, X4
 Therapeutics, Inc. is a wholly owned subsidiary of the Company.
 which changed its name to X4 Pharmaceuticals, Inc. As used herein,
 the words &#x201C;the Company&#x201D; refers to, for periods
 following the Merger, X4 Pharmaceuticals, Inc. (formerly Arsanis,
 Inc.), together with is direct and indirect subsidiaries, and for
 periods prior to the Merger, X4 Therapeutics, Inc. (formerly X4
 Pharmaceuticals, Inc.), and its direct and indirect subsidiaries,
 as applicable.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Immediately following the Merger, stockholders of X4 owned
 approximately 63.7% of the combined organization&#x2019;s
 outstanding common stock. On March&#xA0;14, 2019, the combined
 organization&#x2019;s common stock began trading on The Nasdaq
 Capital Market under the ticker symbol &#x201C;XFOR.&#x201D;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Reverse Stock Split</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 On March&#xA0;13, 2019, immediately following the closing of the
 Merger, the Company effected a <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">6-for-1</font></font> reverse stock split of
 its common stock (the &#x201C;Reverse Stock Split&#x201D;).
 Accordingly, all share and per share amounts for all periods
 presented in the accompanying condensed consolidated financial
 statements and notes thereto have been adjusted retroactively,
 where applicable, to reflect the Reverse Stock Split. No fractional
 shares were issued in connection with the Reverse Stock Split.
 Unless otherwise noted, all references to common stock share and
 per share amounts have also been adjusted to reflect the exchange
 ratio of 0.5702.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 18px">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt">
 <b><i>Going Concern Assessment</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 In accordance with Accounting Standards Update (&#x201C;ASU&#x201D;)
 <font style="WHITE-SPACE: nowrap">No.&#xA0;2014-15,</font>
 <i>Disclosure of Uncertainties about an Entity&#x2019;s Ability to
 Continue as a Going Concern (Subtopic <font style="WHITE-SPACE: nowrap">205-40)</font></i> , the Company has
 evaluated whether there are certain conditions and events,
 considered in the aggregate, that raise substantial doubt about the
 Company&#x2019;s ability to continue as a going concern within one
 year after the date that the consolidated financial statements are
 issued. As of May&#xA0;14, 2019, the issuance date of these
 condensed consolidated financial statements, the Company expects
 that its cash and cash equivalents, including approximately
 $79&#xA0;million of net proceeds from the public sale of common
 stock, <font style="WHITE-SPACE: nowrap">pre-funded</font> warrants
 and Class A warrants in April 2019, will be sufficient to fund its
 forecasted operating expenses, capital expenditure requirements and
 debt service payments for at least the next twelve months from the
 issuance of these financial statements. The future viability of the
 Company beyond that point is dependent on its ability to raise
 additional capital to finance its operations.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 If the Company is unable to obtain funding, the Company will be
 forced to delay, reduce or eliminate some or all of its research
 and development programs, product portfolio expansion or
 <font style="WHITE-SPACE: nowrap">pre-commercialization</font>
 efforts, which could adversely affect its business prospects, or
 the Company may be unable to continue operations. Although
 management continues to pursue these plans, there is no assurance
 that the Company will be successful in obtaining sufficient funding
 on terms acceptable to the Company to fund continuing operations,
 if at all.</p>


 </div><span></span>
</td>
</tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The entire disclosure for the business description and basis of presentation concepts.  Business description describes the nature and type of organization including but not limited to organizational structure as may be applicable to holding companies, parent and subsidiary relationships, business divisions, business units, business segments, affiliates and information about significant ownership of the reporting entity.  Basis of presentation describes the underlying basis used to prepare the financial statements (for example, US Generally Accepted Accounting Principles, Other Comprehensive Basis of Accounting, IFRS).</p></div>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6770772608">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Summary of Significant Accounting Policies<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AccountingPoliciesAbstract', window );"><strong>Accounting Policies [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SignificantAccountingPoliciesTextBlock', window );">Summary of Significant Accounting Policies</a></td>
<td class="text"><div>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td valign="top" width="4%" align="left"><b>2.</b></td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"><b>Summary of Significant Accounting Policies</b></p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 <b><i>Unaudited Interim Financial Statements</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The condensed balance sheet at December&#xA0;31, 2018 was derived
 from audited financial statements but does not include all
 disclosures required by GAAP. The accompanying condensed
 consolidated financial statements are unaudited. The accompanying
 unaudited interim consolidated financial statements have been
 prepared by the Company pursuant to the rules and regulations of
 the Securities and Exchange Commission (the &#x201C;SEC&#x201D;) for
 interim financial statements. Accordingly, certain information and
 footnote disclosures normally included in financial statements
 prepared in accordance with GAAP have been condensed or omitted
 pursuant to such rules and regulations. However, the Company
 believes that the disclosures are adequate to make the information
 presented not misleading. These unaudited condensed financial
 statements should be read in conjunction with the
 Company&#x2019;s&#xA0;audited financial statements and the notes
 thereto for the year ended December&#xA0;31, 2018. In the opinion
 of management, all adjustments, consisting only of normal recurring
 adjustments as necessary, for the fair statement of the
 Company&#x2019;s condensed financial position, condensed results of
 its operations and cash flows have been made. The results of
 operations for the three months ended March&#xA0;31, 2019 are not
 necessarily indicative of the results of operations that may be
 expected for the year ending December&#xA0;31, 2019.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Use of Estimates</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The preparation of the Company&#x2019;s condensed consolidated
 financial statements in conformity with GAAP requires management to
 make estimates and assumptions that affect the reported amounts of
 assets and liabilities, the disclosure of contingent assets and
 liabilities at the date of the consolidated financial statements,
 and the reported amounts of expenses during the reporting period.
 Significant estimates and assumptions reflected in these
 consolidated financial statements include, but are not limited to,
 the accrual of research and development expenses, the valuation of
 intangible assets acquired in business combinations, the valuations
 of common stock prior to the Merger, the valuation of stock
 options, preferred stock warrants (and the resulting preferred
 stock warrant liability), derivative instruments (and the resulting
 derivative liability), and the preferred stock repurchase
 liability, and valuation of lease liabilities. The Company bases
 its estimates on historical experience, known trends and other
 market-specific or other relevant factors that it believes to be
 reasonable under the circumstances. On an ongoing basis, management
 evaluates its estimates when there are changes in circumstances,
 facts and experience. Changes in estimates are recorded in the
 period in which they become known. Actual results could differ from
 those estimates.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Principles of Consolidation</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The condensed consolidated financial statements include the
 accounts of the Company and its wholly owned subsidiaries,
 including Arsanis Biosciences GmbH, which is incorporated in
 Vienna, Austria (&#x201C;Arsanis GmbH&#x201D;), and X4 Therapeutics,
 Inc. All significant intercompany accounts and transactions have
 been eliminated.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Foreign Currency and Currency Translation</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Management has determined that the functional currency for the
 Company&#x2019;s wholly owned foreign subsidiary, Arsanis
 Biosciences GmbH, is the Euro. Management&#x2019;s assessment
 considered the currency environment in which the entity operates,
 including inflows of cash from research and development incentive
 programs and outflows of cash for operating expenditure.
 Accordingly, the assets and liabilities of Arsanis Biosciences GmbH
 are translated from the Euro into United States dollars at the
 exchange rate in effect on the balance sheet date and income and
 expenses are translated at the average exchange rate in effect
 during the period. Unrealized translation gains and losses are
 recorded as a cumulative translation adjustment, which is included
 in the consolidated balance sheet as a component of accumulated
 other comprehensive income (loss). Adjustments that arise from
 exchange rate changes on transactions denominated in a currency
 other than the Euro are included in other income (expense), net in
 the consolidated statements of operations as incurred.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Concentrations of Credit Risk and Significant
 Suppliers</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Financial instruments that potentially subject the Company to
 concentrations of credit risk consist principally of cash and cash
 equivalents and research and development incentive receivables. The
 Company generally maintains cash balances in various operating
 accounts at financial institutions that management believes to be
 of high credit quality, in amounts that may exceed federally
 insured limits. The Company has not experienced any losses related
 to its cash and cash equivalents.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company is dependent on third-party manufacturers to supply
 products for research and development activities in its programs.
 The Company relies and expects to continue to rely on a small
 number of manufacturers to supply it with its requirements for the
 active pharmaceutical ingredients and formulated drugs related to
 these programs. These programs could be adversely affected by a
 significant interruption in these manufacturing services or in the
 supply of active pharmaceutical ingredients and formulated
 drugs.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Cash and Cash Equivalents</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company considers all highly liquid investments with maturities
 of three months or less at the date of purchase to be cash
 equivalents. Cash equivalents consisted of money market funds as of
 March&#xA0;31, 2019 and December&#xA0;31, 2018.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Restricted Cash</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 In connection with the Company&#x2019;s lease agreement entered into
 January 2017 for its facility in Cambridge, Massachusetts, the
 Company maintains a letter of credit of $264 for the benefit of the
 landlord. As of March&#xA0;31, 2019 and December&#xA0;31, 2018, the
 underlying cash balance securing this letter of credit was
 classified as restricted cash <font style="WHITE-SPACE: nowrap">(non-current)</font> on its condensed
 consolidated balance sheets.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company also maintains letters of credit for the benefit of the
 landlords in connection with the Company&#x2019;s office,
 laboratory, parking and storage space leases in Waltham, MA and
 Vienna, Austria and another letter of credit in connection with
 Company&#x2019;s corporate credit cards. As of March&#xA0;31, 2019,
 long term restricted cash consisted of letters of credit related to
 the Company&#x2019;s leases of office, laboratory, parking and
 storage space lease in Vienna, Austria, of $283 and leased office
 space acquired from Arsanis located in Waltham, MA, which expires
 on December&#xA0;31, 2023, of approximately $250.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 As of March&#xA0;31, 2019, the Company was also required to
 maintain a separate cash balance of $150 to collateralize corporate
 credit cards with a bank, which was classified as restricted cash
 <font style="WHITE-SPACE: nowrap">(non-current)</font> on its
 consolidated balance sheets.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Property and Equipment</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Property and equipment are stated at cost less accumulated
 depreciation and amortization. Depreciation and amortization
 expense is recognized using the straight-line method over the
 estimated useful life of each asset, as follows:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="68%" align="center" border="0">
 <tr>
 <td width="62%"></td>
 <td valign="bottom" width="4%"></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" align="center"><b>Estimated&#xA0;Useful&#xA0;Life</b></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Office furniture</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" align="center">3 years</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Computer equipment</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" align="center">3 years</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Software</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" align="center">3 years</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Laboratory equipment</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" align="center">3 to 10 years</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Leasehold improvements</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" align="center">
 Shorter&#xA0;of&#xA0;lease&#xA0;term&#xA0;or&#xA0;10&#xA0;years</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Estimated useful lives are periodically assessed to determine if
 changes are appropriate. Maintenance and repairs are charged to
 expense as incurred. When assets are retired or otherwise disposed
 of, the cost of these assets and related accumulated depreciation
 or amortization are eliminated from the consolidated balance sheet
 and any resulting gains or losses are included in the consolidated
 statements of operations and comprehensive loss in the period of
 disposal. Costs for capital assets not yet placed into service are
 capitalized as <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">construction-in-progress</font></font> and
 depreciated once placed into service.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 18px">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt">
 <b><i><font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">Right-of-Use</font></font> Assets and
 Leases</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Effective January&#xA0;1, 2019, the Company adopted Accounting
 Standards Codification (&#x201C;ASC&#x201D;), Topic 842,
 <i>Leases</i> (&#x201C;ASC 842&#x201D;), using the modified
 retrospective approach through a cumulative-effect adjustment and
 utilizing the effective date as its date of initial application,
 with prior periods unchanged and presented in accordance with the
 guidance in Topic 840, <i>Leases</i> (&#x201C;ASC 840&#x201D;).</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 At the inception of an arrangement, the Company determines whether
 the arrangement is or contains a lease based on the unique facts
 and circumstances present. Leases with a <font style="WHITE-SPACE: nowrap">non-cancellable</font> term greater than one
 year are recognized on the balance sheet as <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font> assets, lease
 liabilities and long-term lease liabilities. The Company has
 elected not to recognize on the balance sheet leases with terms of
 one year or less. Options to renew a lease are not included in the
 Company&#x2019;s initial lease term assessment unless there is
 reasonable certainty that the Company will renew.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Operating lease liabilities and their corresponding <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font> assets are
 recorded based on the present value of lease payments over the
 expected remaining lease term. However, certain adjustments to the
 <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font> operating asset
 may be required for items, such as incentives received. The
 interest rate implicit in lease contracts is typically not readily
 determinable. As a result, the Company utilizes its incremental
 borrowing rates, which are the rates it incurs to borrow on a
 collateralized basis over a similar term an amount equal to the
 lease payments in a similar economic environment.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 In accordance with the guidance in ASC 842, components of a lease
 are split into lease components and <font style="WHITE-SPACE: nowrap">non-lease</font> components. A policy
 election is available pursuant to which an entity may elect to not
 separate lease and <font style="WHITE-SPACE: nowrap">non-lease</font> components. Rather, each
 lease component and the related <font style="WHITE-SPACE: nowrap">non-lease</font> components would be
 accounted for together as a single component. For new and amended
 leases beginning in 2019 and after, the Company has elected to
 account for the lease and <font style="WHITE-SPACE: nowrap">non-lease</font> components as a combined
 lease component for its office and laboratory building leases.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Impairment of Long-Lived Assets</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Long-lived assets consist of property and equipment. Long-lived
 assets to be held and used are tested for recoverability whenever
 events or changes in business circumstances indicate that the
 carrying amount of the assets may not be fully recoverable. Factors
 that the Company considers in deciding when to perform an
 impairment review include significant underperformance of the
 business in relation to expectations, significant negative industry
 or economic trends and significant changes or planned changes in
 the use of the assets. If an impairment review is performed to
 evaluate a long-lived asset group for recoverability, the Company
 compares forecasts of undiscounted cash flows expected to result
 from the use and eventual disposition of the long-lived asset group
 to its carrying value. An impairment loss would be recognized in
 loss from operations when estimated undiscounted future cash flows
 expected to result from the use of an asset group are less than its
 carrying amount. The impairment loss would be based on the excess
 of the carrying value of the impaired asset group over its fair
 value. To date, the Company has not recorded any impairment losses
 on long-lived assets.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Goodwill</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Business combinations are accounted for under the acquisition
 method. The total purchase price of an acquisition is allocated to
 the underlying identifiable net assets, based on their respective
 estimated fair values as of the acquisition date. Determining the
 fair value of assets acquired and liabilities assumed requires
 management&#x2019;s judgment and often involves the use of
 significant estimates and assumptions, including assumptions with
 respect to future cash inflows and outflows, probabilities of
 success, discount rates, and asset lives, among other items. Assets
 acquired and liabilities assumed are recorded at their estimated
 fair values. The excess of the purchase price over the estimated
 fair values of the net assets acquired is recorded as goodwill.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Goodwill is tested for impairment at the reporting unit level
 annually in the fourth quarter, or more frequently when events or
 changes in circumstances indicate that the asset might be impaired.
 Examples of such events or circumstances include, but are not
 limited to, a significant adverse change in legal or business
 climate, an adverse regulatory action or unanticipated competition.
 The Company has determined that it operates in a single operating
 segment and has a single reporting unit.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company assesses qualitative factors to determine whether the
 existence of events or circumstances would indicate that it is more
 likely than not that the fair value of the reporting unit was less
 than its carrying amount. If after assessing the totality of events
 or circumstances, the Company were to determine that it is more
 likely than not that the fair value of the reporting unit is less
 than its carrying amount, then the Company would perform a
 quantitative impairment test.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company compares the fair value of the reporting unit to its
 carrying value. If the fair value of the reporting unit exceeds the
 carrying value of the net assets, goodwill is not impaired, and no
 further testing is required. If the fair value of the reporting
 unit is less than the carrying value, the Company measures the
 amount of impairment loss, if any, as the excess of the carrying
 value over the fair value of the reporting unit. The Company has
 determined there were no indicators of goodwill impairment as of
 March&#xA0;31, 2019.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 18px">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt">
 <b><i>Intangible Assets</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company acquired certain <font style="WHITE-SPACE: nowrap">in-process</font> research and development
 assets (&#x201C;IPR&amp;D&#x201D;), which are classified as
 indefinite-lived intangible assets. Acquired IPR&amp;D represents
 the fair value assigned to research and development assets that the
 Company acquires and have not been completed at the acquisition
 date. The fair value of IPR&amp;D acquired in a business
 combination is capitalized on the Company&#x2019;s consolidated
 balance sheets at the acquisition-date fair value and is determined
 by estimating the costs to develop the technology into commercially
 viable products, estimating the resulting revenue from the
 projects, and discounting the projected net cash flows to present
 value. IPR&amp;D is not amortized, but rather is reviewed for
 impairment on an annual basis or more frequently if indicators of
 impairment are present, until the project is completed or
 abandoned. If the Company determines that IPR&amp;D becomes
 impaired or is abandoned, the carrying value is written down to its
 fair value with the related impairment charge recognized in the
 Company&#x2019;s consolidated statement of operations in the period
 in which the impairment occurs. Upon successful completion of each
 project and launch of the product, the Company will make a separate
 determination of the estimated useful life of the IPR&amp;D
 intangible asset and the related amortization will be recorded as
 an expense prospectively over its estimated useful life.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The projected discounted cash flow models used to estimate the
 Company&#x2019;s IPR&amp;D reflect significant assumptions regarding
 the estimates a market participant would make in order to evaluate
 a drug development asset, including the following:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">Probability of successfully completing clinical trials
 and obtaining regulatory approval;</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">Market size, market growth projections, and market
 share;</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">Estimates regarding the timing of and the expected
 costs to advance the Company&#x2019;s clinical programs to
 commercialization;</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">Estimates of future cash flows from potential product
 sales; and</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">A discount rate.</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Additionally, to the extent the Company acquire other
 indefinite-lived intangible assets through its business
 combinations, these assets are reviewed for impairment on an annual
 basis or more frequently if indicators of impairment are present.
 If the Company determines that the asset becomes impaired, the
 carrying value is written down to its fair value with the related
 impairment charge recognized in its consolidated statements of
 operations in the period in which the impairment occurs.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Deferred Rent</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company&#x2019;s lease agreements include payment escalations
 and lease incentives (including a leasehold improvement tenant
 allowance). For periods prior to January&#xA0;1, 2019, these
 payments were accrued or deferred as appropriate such that rent
 expense was recognized on a straight-line basis over the respective
 lease terms. Effective January&#xA0;1, 2019, upon the adoption of
 ASC 842, deferred rent was reclassified as a reduction to the
 applicable <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font> asset as further
 described in Note 8.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Fair Value Measurements</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Certain assets and liabilities of the Company are carried at fair
 value under GAAP. Fair value is defined as the exchange price that
 would be received for an asset or paid to transfer a liability (an
 exit price) in the principal or most advantageous market for the
 asset or liability in an orderly transaction between market
 participants on the measurement date. Valuation techniques used to
 measure fair value must maximize the use of observable inputs and
 minimize the use of unobservable inputs. Financial assets and
 liabilities carried at fair value are to be classified and
 disclosed in one of the following three levels of the fair value
 hierarchy, of which the first two are considered observable and the
 last is considered unobservable:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">Level 1&#x2014;Quoted prices in active markets for
 identical assets or liabilities.</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">Level 2&#x2014;Observable inputs (other than
 Level&#xA0;1 quoted prices), such as quoted prices in active
 markets for similar assets or liabilities, quoted prices in markets
 that are not active for identical or similar assets or liabilities,
 or other inputs that are observable or can be corroborated by
 observable market data.</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">Level 3&#x2014;Unobservable inputs that are supported
 by little or no market activity that are significant to determining
 the fair value of the assets or liabilities, including pricing
 models, discounted cash flow methodologies and similar
 techniques.</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Prior to the Merger, the Company&#x2019;s preferred stock warrant
 liability, derivative liability and preferred stock repurchase
 liability were carried at fair value, determined according to
 Level&#xA0;3 inputs in the fair value hierarchy described above
 (See Note&#xA0;4). The Company&#x2019;s cash equivalents, consisting
 of money market funds invested in U.S. Treasury securities, are
 carried at fair value, determined based on Level&#xA0;2 inputs in
 the fair value hierarchy described above (see Note 4). The carrying
 values of the Company&#x2019;s accounts payable and accrued expenses
 approximate their fair values due to the short-term nature of these
 liabilities. The carrying value of the Company&#x2019;s outstanding
 loan and security agreement (the &#x201C;Hercules Loan
 Agreement&#x201D;) with Hercules Capital, Inc.
 (&#x201C;Hercules&#x201D;) approximates its fair value at
 March&#xA0;31, 2019 because the debt bears interest at a variable
 market rate and the Company&#x2019;s credit risk has not materially
 changed since the inception of the agreement. The carrying value of
 the Company&#x2019;s loans under the funding agreements with
 &#xD6;sterreichische Forschungsf&#xF6;rderungsgesellschaft mbH
 (&#x201C;FFG&#x201D;) were recorded at fair value on the opening
 balance sheet of Arsanis as of the date of the Merger, and
 approximates the fair value of the loans at March&#xA0;31, 2019.
 (See Note&#xA0;3).</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Segment Information</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company manages its operations as a single operating segment
 for the purposes of assessing performance and making operating
 decisions. The Company&#x2019;s focus is on the discovery,
 development and commercialization of novel therapeutics for the
 treatment of rare diseases.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Revenue Recognition</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Effective January&#xA0;1, 2018, the Company adopted ASC Topic 606,
 Revenue from Contracts with Customers (&#x201C;ASC 606&#x201D;),
 using the modified retrospective transition method. The modified
 retrospective method requires that the cumulative effect of
 initially applying ASC 606 be recognized as an adjustment to the
 opening balance of retained earnings or accumulated deficit of the
 annual period that includes the date of initial application. The
 Company did not have any arrangements that were in the scope of ASC
 606 on January&#xA0;1, 2018 and thus there was no impact to the
 condensed consolidated financial statements as a result of the
 adoption. This standard applies to all contracts with customers,
 except for contracts that are within the scope of other standards,
 such as collaboration arrangements and leases. Prior to completion
 of the Merger, Arsanis entered into a single <font style="WHITE-SPACE: nowrap">out-licensing</font> agreement with Janssen
 Pharmaceuticals, Inc. (see Note 13) that was within the scope of
 ASC 606.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Research and Development Programs</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Proceeds under the research and development incentive program from
 the Austrian government are recognized as other income in an amount
 equal to the qualifying expenses incurred in each period multiplied
 by the applicable reimbursement percentage. Incentive income
 recognized upon incurring qualifying expenses in advance of receipt
 of proceeds from research and development incentives is recorded in
 the consolidated balance sheet as research and development
 incentive receivables.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Research and Development Costs</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Costs associated with internal research and development and
 external research and development services, including drug
 development and preclinical studies, are expensed as incurred.
 Research and development expenses include costs for salaries,
 employee benefits, subcontractors, facility-related expenses,
 depreciation and amortization, stock-based compensation,
 third-party license fees, laboratory supplies, and external costs
 of outside vendors engaged to conduct discovery, preclinical and
 clinical development activities and clinical trials as well as to
 manufacture clinical trial materials, and other costs. The Company
 recognizes external research and development costs based on an
 evaluation of the progress to completion of specific tasks using
 information provided to the Company by its service providers.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Nonrefundable advance payments for goods or services to be received
 in the future for use in research and development activities are
 recorded as prepaid expenses. Such prepaid expenses are recognized
 as an expense when the goods have been delivered or the related
 services have been performed, or when it is no longer expected that
 the goods will be delivered or the services rendered.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Upfront payments, milestone payments and annual maintenance fees
 under license agreements are expensed in the period in which they
 are incurred.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Patent Costs</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 All patent-related costs incurred in connection with filing and
 prosecuting patent applications are expensed as incurred due to the
 uncertainty about the recovery of the expenditure. Amounts incurred
 are classified as general and administrative expenses.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Debt Issuance Costs</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Debt issuance costs consist of payments made to secure commitments
 under certain debt financing arrangements. These amounts are
 recognized as interest expense over the period of the financing
 arrangement using the effective interest method. If the financing
 arrangement is canceled or forfeited, or if the utility of the
 arrangement to the Company is otherwise compromised, these costs
 are recognized as interest expense immediately. The Company&#x2019;s
 consolidated financial statements present debt issuance costs
 related to a recognized debt liability as a direct reduction from
 the carrying amount of that debt liability.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Stock-Based Compensation</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company measures all stock-based awards granted to employees
 and directors based on the fair value on the date of the grant and
 recognizes compensation expense for those awards, net of estimated
 forfeitures, over the requisite service period, which is generally
 the vesting period of the respective award. The Company issues
 stock-based awards with only service-based vesting conditions and
 records the expense for these awards using the straight-line
 method. The Company has not issued any stock-based awards with
 performance-based vesting conditions.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 12px">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt">
 Effective January&#xA0;1, 2019, the Company adopted ASU No.
 <font style="WHITE-SPACE: nowrap">2018-07,&#xA0;Compensation&#x2014;Stock</font>
 Compensation (Topic 718): Improvements to Nonemployee Share-Based
 Payment Accounting&#xA0;(&#x201C;ASU <font style="WHITE-SPACE: nowrap">2018-07&#x201D;),</font> which expands the
 scope of Topic 718 to include share-based payment awards to
 nonemployees. As a result, stock-based awards granted to
 consultants and <font style="WHITE-SPACE: nowrap">non-employees</font> are accounted for in the
 same manner as awards granted to employees and directors as
 described above. The impact of adoption this new guidance did not
 have a material impact on the Company&#x2019;s consolidated
 financial statements. Prior to the adoption of ASU <font style="WHITE-SPACE: nowrap">2018-07,</font> for stock-based awards
 granted to <font style="WHITE-SPACE: nowrap">non-employee</font>
 consultants, compensation expense was recognized over the period
 during which services were rendered by such <font style="WHITE-SPACE: nowrap">non-employee</font> consultants until
 completed. At the end of each financial reporting period prior to
 completion of the service, the fair value of these awards was
 remeasured using the then-current fair value of the Company&#x2019;s
 common stock and updated assumption inputs in the Black-Scholes
 option-pricing model.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company classifies stock-based compensation expense in its
 consolidated statement of operations and comprehensive loss in the
 same manner in which the award recipient&#x2019;s payroll costs are
 classified or in which the award recipient&#x2019;s service payments
 are classified.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company recognizes compensation expense for only the portion of
 awards that are expected to vest. In developing a forfeiture rate
 estimate, the Company has considered its historical experience to
 estimate <font style="WHITE-SPACE: nowrap">pre-vesting</font>
 forfeitures for service-based awards. The impact of a forfeiture
 rate adjustment will be recognized in full in the period of
 adjustment, and if the actual forfeiture rate is materially
 different from the Company&#x2019;s estimate, the Company may be
 required to record adjustments to stock-based compensation expense
 in future periods.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The fair value of each stock option grant is estimated on the date
 of grant using the Black-Scholes option-pricing model. Prior to
 March&#xA0;13, 2019, the Company had been a private company and
 lacked company-specific historical and implied volatility
 information for its stock. Therefore, the Company estimates its
 expected stock price volatility based on the historical volatility
 of publicly traded peer companies and expects to continue to do so
 until it has adequate historical data regarding the volatility of
 its own traded stock price. The expected term of the
 Company&#x2019;s stock options has been determined utilizing the
 &#x201C;simplified&#x201D; method for awards that qualify as
 &#x201C;plain-vanilla&#x201D; options. The expected term of stock
 options granted to <font style="WHITE-SPACE: nowrap">non-employee</font> consultants is equal to
 the contractual term of the option award. The risk-free interest
 rate is determined by reference to the U.S. Treasury yield curve in
 effect at the time of grant of the award for time periods
 approximately equal to the expected term of the award. Expected
 dividend yield is based on the fact that the Company has never paid
 cash dividends on common stock and does not expect to pay any cash
 dividends in the foreseeable future.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Preferred Stock Warrant Liability</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Prior to the Merger with Arsanis, the Company classified warrants
 for the purchase of shares of its convertible preferred stock (see
 Note&#xA0;10) as a liability on its consolidated balance sheets as
 these warrants are freestanding financial instruments that may have
 required the Company to transfer assets upon exercise. The warrant
 liability, which consisted of warrants for the purchase of
 Series&#xA0;A and Series&#xA0;B convertible preferred stock, was
 initially recorded at fair value upon the date of issuance of each
 warrant and is subsequently remeasured to fair value at each
 reporting date. Changes in the fair value of the warrant liability
 are recognized as a component of other income (expense), net in the
 consolidated statement of operations and comprehensive loss.
 Concurrent with the closing of the Merger, all X4 preferred stock
 was converted to Arsanis common stock and the X4 preferred stock
 warrants converted to warrants for the purchase of Arsanis common
 stock. The Company assessed the features of the warrants and
 determined that they qualify for classification as permanent
 equity. Accordingly, the Company remeasured the warrants to fair
 value upon the closing of the Merger and reclassified the resulting
 warrant liability to additional <font style="WHITE-SPACE: nowrap">paid-in</font> capital. (see
 Note&#xA0;10).</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Derivative Liability</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company&#x2019;s license agreement with Genzyme Corporation
 (&#x201C;Genzyme&#x201D;) (see Note&#xA0;13) contained a contingent
 payment obligation that required the Company to make a cash payment
 to Genzyme upon a change of control event of the Company. The
 contingent payment obligation met the definition of a derivative
 instrument as the contingent payment obligation was not clearly and
 closely related to its host instrument and was a cash-settled
 liability. Accordingly, the Company classified this derivative as a
 liability within other liabilities <font style="WHITE-SPACE: nowrap">(non-current)</font> on its condensed
 consolidated balance sheet. The derivative liability was initially
 recorded at fair value on the date of entering into the license
 agreement and was subsequently remeasured to fair value at each
 reporting date. Changes in the fair value of this derivative
 liability were recognized as a component of other income (expense),
 net in the condensed consolidated statement of operations and
 comprehensive loss. The Merger with Arsanis (see Note 1) qualified
 as a change of control event, as defined in the license agreement,
 but resulted in no payment being due to Genzyme under the license
 agreement. As a result, on March&#xA0;13, 2019, the closing date of
 the Merger with Arsanis, the derivative liability was remeasured to
 fair value, which was $0, and subsequent changes in fair value will
 no longer be recognized in the consolidated statements of
 operations and comprehensive loss because the contingent payment
 obligation to Genzyme expired at that time.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 12px">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt">
 In addition, the Company&#x2019;s Hercules loan (see Note&#xA0;7)
 contains a redemption feature that, upon an event of default,
 provides Hercules the option to accelerate and demand repayment of
 the debt, including a prepayment premium. The redemption feature
 meets the definition of a derivative instrument as the repayment of
 the debt contains a substantial premium, resulting in the
 redemption feature not being clearly and closely related to its
 host instrument. Accordingly, the Company classifies this
 derivative as a liability within other liabilities <font style="WHITE-SPACE: nowrap">(non-current)</font> on its condensed
 consolidated balance sheet. The derivative liability was initially
 recorded at fair value on the date of entering into the Hercules
 Loan Agreement and is subsequently remeasured to fair value at each
 reporting date. Changes in the fair value of this derivative
 liability are recognized as a component of other income (expense),
 net in the condensed consolidated statement of operations and
 comprehensive loss. Changes in the fair value of this derivative
 liability will continue to be recognized until all amounts
 outstanding under the Hercules Loan Agreement are repaid or until
 the Hercules Loan Agreement is terminated.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Comprehensive Loss</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Comprehensive loss includes net loss as well as other changes in
 stockholders&#x2019; equity (deficit) that result from transactions
 and economic events other than those with stockholders. For the
 three months ended March&#xA0;31, 2019, comprehensive loss included
 $23 of foreign currency translation gain adjustments.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Income Taxes</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company accounts for income taxes using the asset and liability
 method, which requires the recognition of deferred tax assets and
 liabilities for the expected future tax consequences of events that
 have been recognized in the consolidated financial statements or in
 the Company&#x2019;s tax returns. Deferred tax assets and
 liabilities are determined based on the difference between the
 financial statement and tax basis of assets and liabilities using
 enacted tax rates in effect for the year in which the differences
 are expected to reverse. Changes in deferred tax assets and
 liabilities are recorded in the provision for income taxes. The
 Company assesses the likelihood that its deferred tax assets will
 be recovered from future taxable income and, to the extent it
 believes, based upon the weight of available evidence, that it is
 more likely than not that all or a portion of the deferred tax
 assets will not be realized, a valuation allowance is established
 through a charge to income tax expense. Potential for recovery of
 deferred tax assets is evaluated by estimating the future taxable
 profits expected and considering prudent and feasible tax planning
 strategies.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company accounts for uncertainty in income taxes recognized in
 the consolidated financial statements by applying a <font style="WHITE-SPACE: nowrap">two-step</font> process to determine the
 amount of tax benefit to be recognized. First, the tax position
 must be evaluated to determine the likelihood that it will be
 sustained upon external examination by the taxing authorities. If
 the tax position is deemed <font style="WHITE-SPACE: nowrap">more-likely-than-not</font> to be sustained,
 the tax position is then assessed to determine the amount of
 benefit to recognize in the consolidated financial statements. The
 amount of the benefit that may be recognized is the largest amount
 that has a greater than 50% likelihood of being realized upon
 ultimate settlement. The provision for income taxes includes the
 effects of any resulting tax reserves, or unrecognized tax
 benefits, that are considered appropriate as well as the related
 net interest and penalties.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Net Income (Loss) per Share</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company follows the <font style="WHITE-SPACE: nowrap">two-class</font> method when computing net
 income (loss) per share as the Company has issued shares that meet
 the definition of participating securities. The <font style="WHITE-SPACE: nowrap">two-class</font> method determines net income
 (loss) per share for each class of common and participating
 securities according to dividends declared or accumulated and
 participation rights in undistributed earnings. The <font style="WHITE-SPACE: nowrap">two-class</font> method requires income
 available to common stockholders for the period to be allocated
 between common and participating securities based upon their
 respective rights to receive dividends as if all income for the
 period had been distributed.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Basic net income (loss) per share attributable to common
 stockholders is computed by dividing the net income (loss)
 attributable to common stockholders by the weighted average number
 of common shares outstanding for the period. Diluted net income
 (loss) attributable to common stockholders is computed by adjusting
 net income (loss) attributable to common stockholders to reallocate
 undistributed earnings based on the potential impact of dilutive
 securities. Diluted net income (loss) per share attributable to
 common stockholders is computed by dividing the diluted net income
 (loss) attributable to common stockholders by the weighted average
 number of common shares outstanding for the period, including
 potential dilutive common shares. For purpose of this calculation,
 outstanding stock options, convertible preferred stock and warrants
 to purchase shares of convertible preferred stock are considered
 potential dilutive common shares.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company&#x2019;s convertible preferred stock contractually
 entitles the holders of such shares to participate in dividends but
 does not contractually require the holders of such shares to
 participate in losses of the Company. Accordingly, in periods in
 which the Company reports a net loss attributable to common
 stockholders, such losses are not allocated to such participating
 securities. In periods in which the Company reports a net loss
 attributable to common stockholders, diluted net loss per share
 attributable to common stockholders is the same as basic net loss
 per share attributable to common stockholders, since dilutive
 common shares are not assumed to have been issued if their effect
 is anti-dilutive. The Company reported a net loss attributable to
 common stockholders for the three months ended March&#xA0;31, 2019
 and 2018.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 18px">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt">
 <b><i>Recently Adopted Accounting Pronouncements</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 In February 2016, the FASB issued ASU <font style="WHITE-SPACE: nowrap">No.&#xA0;2016-02</font><i>, Leases
 (Topic</i><i>&#xA0;842)</i> (&#x201C;ASU <font style="WHITE-SPACE: nowrap">2016-02&#x201D;</font> or &#x201C;ASC
 842&#x201D;)), which sets out the principles for the recognition,
 measurement, presentation and disclosure of leases for both parties
 to a contract (i.e., lessees and lessors). The new standard
 requires lessees to apply a dual approach, classifying leases as
 either finance or operating leases based on the principle of
 whether or not the lease is effectively a financed purchase by the
 lessee. This classification will determine whether lease expense is
 recognized based on an effective interest method or on a
 straight-line basis over the term of the lease. A lessee is also
 required to record a <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font> asset and a lease
 liability for all leases with a term of greater than 12&#xA0;months
 regardless of their classification. Leases with a term of 12 months
 or less may be accounted for similar to prior guidance for
 operating leases. The Company adopted the new leasing standard as
 of the required effective date of January&#xA0;1, 2019 using a
 modified retrospective transition approach to be applied to leases
 existing as of, or entered into after, January&#xA0;1, 2019. The
 adoption had no impact on accumulated deficit. The new lease
 standard provides a number of optional practical expedients in
 transition. The Company applied the package of practical expedients
 to leases that commenced prior to the effective date, whereby it
 will elect to not reassess the following: (i)&#xA0;whether any
 expired or existing contracts contain leases; (ii)&#xA0;the lease
 classification for any expired or existing leases; and
 (iii)&#xA0;initial direct costs for any existing leases. The
 Company also elected the short-term lease recognition exemption for
 all leases that qualify, where a <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font> asset or lease
 liability will not be recognized for short-term leases. Upon the
 adoption of ASC 842, the Company recorded $2.5&#xA0;million of
 operating lease liabilities and $2.0&#xA0;million of <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use&#xA0;assets</font></font> on its
 consolidated balance. The adoption did not have a material impact
 on the Company&#x2019;s statement of operations, statement of
 comprehensive loss or statement of cash flows.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 In January 2017, the FASB issued ASU <font style="WHITE-SPACE: nowrap">No.&#xA0;2017-04,</font><i>&#xA0;Intangibles-Goodwill
 and Other (Topic 350): Simplifying the Test for Goodwill
 Impairment.</i>&#xA0;The new standard simplifies the subsequent
 measurement of goodwill by eliminating the second step of the
 goodwill impairment test. This ASU will be applied prospectively
 and is effective for annual or interim goodwill impairment tests in
 fiscal years beginning after December&#xA0;15, 2019 with early
 adoption permitted. The Company has adopted this guidance on
 January&#xA0;1, 2019 and will apply it to its annual impairment
 test, and any interim impairment tests during the year ending
 December&#xA0;31, 2019.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 In April 2017, the FASB issued ASU <font style="WHITE-SPACE: nowrap">2017-08,</font><i>&#xA0;Receivables &#x2013;
 Nonrefundable Fees and Other Costs</i> (&#x201C;Subtopic
 <font style="WHITE-SPACE: nowrap">310-20&#x201D;).</font> The new
 standard amends the amortization period for certain purchased
 callable debt securities held at a premium by shortening the
 amortization period for the premium to the earliest call
 date.&#xA0;Subtopic <font style="WHITE-SPACE: nowrap">310-20</font>
 calls for a modified retrospective application under which&#xA0;a
 cumulative-effect adjustment will be made to retained earnings as
 of the beginning of the first reporting period in which the
 guidance is adopted.&#xA0;The new standard will be effective
 beginning January&#xA0;1, 2019 and early adoption is permitted for
 public entities.&#xA0;The Company adopted this guidance, effective
 January&#xA0;1, 2019, and its adoption had no impact on the
 Company&#x2019;s financial position, results of operations or cash
 flows.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 In July 2017, the FASB issued ASU <font style="WHITE-SPACE: nowrap">No.&#xA0;2017-11,</font> <i>Earnings Per
 Share (Topic</i><i>&#xA0;260), Distinguishing Liabilities from
 Equity (Topic</i><i>&#xA0;480), Derivatives and Hedging
 (Topic</i><i>&#xA0;815) (Part</i><i>&#xA0;I) Accounting for Certain
 Financial Instruments with Down Round Features
 (Part</i><i>&#xA0;II) Replacement of the Indefinite Deferral for
 Mandatorily Redeemable Financial Instruments of Certain Nonpublic
 Entities and Certain Mandatorily Redeemable Noncontrolling
 Interests with a Scope Exception</i> (&#x201C;ASU <font style="WHITE-SPACE: nowrap">2017-11&#x201D;).</font> Part&#xA0;I applies
 to entities that issue financial instruments such as warrants,
 convertible debt or convertible preferred stock that contain
 down-round features. Part&#xA0;II replaces the indefinite deferral
 for certain mandatorily redeemable noncontrolling interests and
 mandatorily redeemable financial instruments of nonpublic entities
 contained within ASC Topic&#xA0;480 with a scope exception and does
 not impact the accounting for these mandatorily redeemable
 instruments. For public entities, ASU <font style="WHITE-SPACE: nowrap">2017-11</font> is effective for annual
 reporting periods beginning after December&#xA0;15, 2018, including
 interim periods within those fiscal years. The Company adopted ASU
 <font style="WHITE-SPACE: nowrap">2017-11</font> as of the required
 effective date of January&#xA0;1, 2019. The adoption of ASU
 <font style="WHITE-SPACE: nowrap">2017-11</font> had no impact on
 the Company&#x2019;s financial position, results of operations or
 cash flows.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 In June 2018, the FASB issued ASU <font style="WHITE-SPACE: nowrap">No.&#xA0;2018-07,</font>
 <i>Compensation&#x2014;Stock Compensation (Topic</i><i>&#xA0;718):
 Improvements to Nonemployee Share-Based Payment Accounting</i>
 (&#x201C;ASU <font style="WHITE-SPACE: nowrap">2018-07&#x201D;).</font> These amendments
 expand the scope of Topic&#xA0;718, Compensation&#x2014;Stock
 Compensation (which previously only included share-based payments
 to employees) to include share-based payments issued to
 <font style="WHITE-SPACE: nowrap">non-employees</font> for goods or
 services. Consequently, the accounting for share-based payments to
 <font style="WHITE-SPACE: nowrap">non-employees</font> and
 employees will be substantially aligned. The ASU supersedes
 <font style="WHITE-SPACE: nowrap">Subtopic&#xA0;505-50,</font>
 Equity&#x2014;<i>Equity-Based Payments to <font style="WHITE-SPACE: nowrap">Non-Employees</font></i>. The Company adopted
 ASU <font style="WHITE-SPACE: nowrap">2018-07</font> on
 January&#xA0;1, 2019. The adoption of this standard had no impact
 on the Company&#x2019;s financial statements.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Recently Issued Accounting Pronouncements</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 In August 2018, the FASB issued ASU <font style="WHITE-SPACE: nowrap">No.&#xA0;2018-13,</font> <i>Fair Value
 Measurement (Topic 820): Disclosure Framework&#x2014;Changes to the
 Disclosure Requirements for Fair Value Measurement</i> (&#x201C;ASU
 <font style="WHITE-SPACE: nowrap">2018-13&#x201D;),</font>
 which&#xA0;removes, adds and modifies certain disclosure
 requirements for fair value measurements in Topic 820. The Company
 will no longer be required to disclose the amount of and reasons
 for transfers between Level&#xA0;1 and Level&#xA0;2 of the fair
 value hierarchy as well as the valuation processes of Level&#xA0;3
 fair value measurements. However, the Company will be required to
 additionally disclose the changes in unrealized gains and losses
 included in other comprehensive income for recurring Level&#xA0;3
 fair value measurements and the range and weighted average of
 assumptions used to develop significant unobservable inputs for
 Level&#xA0;3 fair value measurements. ASU <font style="WHITE-SPACE: nowrap">2018-13</font> is effective for fiscal years,
 and interim periods within those fiscal years, beginning after
 December&#xA0;15, 2019. The amendments relating to additional
 disclosure requirements will be applied prospectively for only the
 most recent interim or annual period presented in the initial year
 of adoption. All other amendments will be applied retrospectively
 to all periods presented upon their effective date. The Company is
 currently evaluating the impact that the adoption of ASU
 <font style="WHITE-SPACE: nowrap">2018-13</font> will have on its
 consolidated financial statements.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 In August 2018, the FASB issued ASU <font style="WHITE-SPACE: nowrap">2018-15,</font><i>&#xA0;Intangibles-Goodwill
 and <font style="WHITE-SPACE: nowrap">Other-Internal-Use</font>
 Software (Subtopic <font style="WHITE-SPACE: nowrap">350-40):</font> Customer&#x2019;s Accounting
 for Implementation Costs Incurred in a Cloud Computing Arrangement
 That Is a Service Contract, (&#x201C;ASU <font style="WHITE-SPACE: nowrap">2018-15&#x201D;)</font></i>. The amendments in
 this update align the requirements for capitalizing implementation
 costs incurred in a hosting arrangement that is a service contract
 with the requirements for capitalizing implementation costs
 incurred to develop or obtain <font style="WHITE-SPACE: nowrap">internal-use</font> software (and hosting
 arrangements that include an <font style="WHITE-SPACE: nowrap">internal-use</font> software license). The
 accounting for the service element of a hosting arrangement that is
 a service contract is not affected by the amendments in this
 update. The new standard will be effective beginning
 January&#xA0;1, 2020 and early adoption is permitted. The
 amendments in this update should be applied either retrospectively
 or prospectively to all implementation costs incurred after the
 date of adoption.&#xA0;The Company is currently evaluating the
 impact that the adoption of ASU <font style="WHITE-SPACE: nowrap">2018-15</font> will have on its consolidated
 financial statements.</p>
 </div><span></span>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The entire disclosure for all significant accounting policies of the reporting entity.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -URI http://asc.fasb.org/topic&amp;trid=2122369<br></p></div>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6827468144">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Merger Accounting<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessCombinationsAbstract', window );"><strong>Business Combinations [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessCombinationDisclosureTextBlock', window );">Merger Accounting</a></td>
<td class="text"><div>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="break-inside: avoid">
 <td valign="top" width="4%" align="left"><b>3.</b></td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left"><b>Merger Accounting</b></p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Based on the Exchange Ratio of 0.5702, immediately following the
 Merger, former Arsanis stockholders, Arsanis option holders and
 other persons holding securities or other rights directly or
 indirectly convertible, exercisable or exchangeable for Arsanis
 common stock owned approximately 31.3% of the outstanding capital
 stock of the combined organization on a fully diluted basis, and
 former X4&#xA0;stockholders, holders of options or warrants to
 acquire X4 capital stock and other persons holding securities and
 other rights directly or indirectly convertible, exercisable or
 exchangeable for X4 capital stock owned approximately 68.7% of the
 outstanding capital stock of the combined organization on a fully
 diluted basis. At the closing of the Merger, all shares of X4
 common stock and X4&#xA0;preferred stock then outstanding were
 exchanged for Arsanis common stock.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In addition, pursuant to the terms of the Merger Agreement, the
 Company, for accounting purposes, assumed all outstanding stock
 options to purchase shares of Arsanis common stock at the closing
 of the Merger. At the closing of the Merger, such stock options
 became options to purchase an aggregate of 271,230 shares of the
 Company&#x2019;s common stock after giving effect to the Reverse
 Stock Split.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The total purchase price paid in the Merger has been allocated to
 the tangible and intangible assets acquired and liabilities assumed
 of Arsanis based on their fair values as of the completion of the
 Merger, with the excess allocated to goodwill. The following
 summarizes the preliminary estimate of the purchase price paid in
 the Merger:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0">
 <tr>
 <td width="85%"></td>
 <td valign="bottom" width="9%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Number of shares of the combined organization owned by Arsanis
 stockholders&#xA0;(1)</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">2,440,582</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Multiplied by the fair value per share of Arsanis common
 stock&#xA0;(2)</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">18.66</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Fair value of consideration issued it effect the Merger</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">45,541</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Fair value of replacement awards held by former employees, board of
 directors and consultants of Arsanis that were vested as of the
 Merger.</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">817</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Purchase price:</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">46,358</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 2pt; FONT-SIZE: medium; FONT-FAMILY: &quot;Times New Roman&quot;; WIDTH: 124px; WHITE-SPACE: normal; WORD-SPACING: 0px; BORDER-BOTTOM: rgb(0,0,0) 1px solid; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; LINE-HEIGHT: 8pt; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="break-inside: avoid">
 <td valign="top" width="4%" align="left">(1)</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left">The number of shares of 2,440,582 represents the
 historical 14,643,737 shares of Arsanis common stock outstanding
 immediately prior to the closing of the Merger, adjusted for the
 Reverse Stock Split.</p>
 </td>
 </tr>
 </table>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="break-inside: avoid">
 <td valign="top" width="4%" align="left">(2)</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left">Based on the last reported sale price of Arsanis
 common stock on the Nasdaq Global Market on March&#xA0;13, 2019,
 the closing date of the Merger, and gives effect to the Reverse
 Stock Split.</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The following summarizes the allocation of the purchase price to
 the net tangible and intangible assets acquired:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0">
 <tr>
 <td width="85%"></td>
 <td valign="bottom" width="6%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Cash and cash equivalents and restricted cash</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">26,406</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Other current assets</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">2,147</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Property and equipment, net</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">68</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 IPR&amp;D indefinite-lived intangible assets</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">4,900</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Other assets,&#xA0;<font style="WHITE-SPACE: nowrap">non-current</font></p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">879</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Current liabilities</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(5,221</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Loans payable</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(8,713</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Other liabilities,&#xA0;<font style="WHITE-SPACE: nowrap">non-current</font></p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(1,515</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Goodwill</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">27,407</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Purchase price</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">
 &#xA0;&#xA0;&#xA0;&#xA0;46,358</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The goodwill of $27,407 is not tax deductible and represents the
 excess of the consideration paid over the fair value of assets
 acquired and liabilities assumed.&#xA0;Goodwill is mainly
 attributable to the enhanced value of the combined company, as
 reflected in the increase in market value of the Arsanis common
 shares following the announcement of the Merger with X4. The
 Company incurred costs directly related to the Merger of
 approximately $1&#xA0;million for the three months ended
 March&#xA0;31, 2019.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The preliminary allocation of the purchase price for the Merger was
 based on estimates of the fair value of the net assets acquired and
 is subject to adjustment upon finalization of the valuation of the
 acquired intangible assets, property, plant and
 equipment,&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font>&#xA0;assets,
 lease obligations, fair value of debt and any related deferred
 taxes. Measurements of these items inherently require significant
 estimates and assumptions.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The following supplemental unaudited pro forma information presents
 the Company&#x2019;s financial results as if the acquisition of
 Arsanis had occurred on January&#xA0;1, 2018:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0">
 <tr>
 <td width="78%"></td>
 <td valign="bottom" width="4%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="4%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="6" align="center"><b>Three Months Ended<br />
 March&#xA0;31,</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>2019</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>2018</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" colspan="6" align="center">
 <b>(unaudited)</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Revenue</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">0</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">0</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Net loss</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">(16,258</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">(20,235</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The above unaudited pro forma information was determined based on
 the historical GAAP results of the Company and Arsanis. The
 unaudited pro forma consolidated results are not necessarily
 indicative of what the Company&#x2019;s consolidated results of
 operations would have been if the acquisition was completed on
 January&#xA0;1, 2018. The unaudited pro forma consolidated net loss
 includes pro forma adjustments primarily relating to the
 reclassification of transaction costs and severance payments
 directly related to the closing of the Merger of $2.7&#xA0;million
 from the three months ended March&#xA0;31, 2019 to the three months
 ended March&#xA0;31, 2018.</p>
 </div><span></span>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The entire disclosure for a business combination (or series of individually immaterial business combinations) completed during the period, including background, timing, and recognized assets and liabilities. The disclosure may include leverage buyout transactions (as applicable).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -URI http://asc.fasb.org/topic&amp;trid=2303972<br></p></div>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6817706032">
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<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Fair Value of Financial Assets and Liabilities<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
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<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueDisclosuresTextBlock', window );">Fair Value of Financial Assets and Liabilities</a></td>
<td class="text"><div>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="break-inside: avoid">
 <td valign="top" width="4%" align="left"><b>4.</b></td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left"><b>Fair Value of Financial Assets and
 Liabilities</b></p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The following tables present information about the Company&#x2019;s
 financial assets and liabilities measured at fair value on a
 recurring basis and indicate the level of the fair value hierarchy
 used to determine such fair values:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="92%" align="center" border="0">
 <tr>
 <td width="60%"></td>
 <td valign="bottom" width="4%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="4%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="4%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="4%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="14" align="center"><b>Fair Value Measurements as of
 March&#xA0;31, 2019 Using:</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;Level&#xA0;1&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;Level&#xA0;2&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;Level&#xA0;3&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;Total&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Assets:</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Cash equivalents&#x2014;money market funds</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">22,299</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">22,299</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">22,299</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">22,299</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Liabilities:</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Preferred stock warrant liability</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Derivative liability</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">18</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">18</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">18</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">18</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="92%" align="center" border="0">
 <tr>
 <td width="61%"></td>
 <td valign="bottom" width="6%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="6%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="6%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="6%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="14" align="center"><b>Fair Value Measurements as of
 December&#xA0;31, 2018 Using:</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;Level&#xA0;1&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;Level&#xA0;2&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;Level&#xA0;3&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;Total&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Assets:</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Cash equivalents&#x2014;money market fund</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">8,134</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">8,134</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">8,134</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">8,134</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Liabilities:</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Preferred stock warrant liability</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">4,947</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">4,947</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Derivative liability</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">201</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">201</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">5,148</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">5,148</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 As of March&#xA0;31, 2019 and December&#xA0;31, 2018, there were no
 transfers between Level&#xA0;1, Level&#xA0;2 and Level&#xA0;3.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The Company&#x2019;s cash equivalents consisted of a money market
 fund invested in U.S. Treasury securities. The money market fund
 was valued using inputs observable in active markets for similar
 securities, which represents a Level&#xA0;2 measurement in the fair
 value hierarchy.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Valuation of Preferred Stock Warrant Liabilities</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The preferred stock warrant liability in the table above consists
 of the fair values of (i)&#xA0;warrants to purchase shares of
 Series&#xA0;A convertible preferred stock that were issued in 2015
 and shares of Series&#xA0;B convertible preferred stock that were
 issued in 2017 and 2018 in connection with the Company&#x2019;s
 Series&#xA0;A and Series&#xA0;B convertible preferred stock
 financings, respectively (see Notes&#xA0;10), (ii)&#xA0;warrants to
 purchase shares of Series&#xA0;A convertible preferred stock that
 were issued in 2016 in connection with the Company&#x2019;s entering
 into a loan and security agreement with Silicon Valley Bank (see
 Note&#xA0;7) and (iii)&#xA0;warrants to purchase shares of
 Series&#xA0;B convertible preferred stock that were issued or were
 issuable in 2018 in connection with the Company&#x2019;s entering
 into the Hercules Loan Agreement (see Note&#xA0;7). The liability
 associated with the warrants was recorded at fair value on the
 dates the warrants were issued and exercisable and was subsequently
 remeasured to fair value at each reporting date through
 December&#xA0;31, 2018. Upon the closing of the Merger, all X4
 preferred stock warrants were converted to warrants for
 Company&#x2019;s common stock and, as a result, the warrants were
 adjusted to fair value and reclassified to permanent equity. The
 aggregate fair value of the warrant liability was determined based
 on significant inputs not observable in the market, which
 represents a Level&#xA0;3 measurement within the fair value
 hierarchy.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The Company used various valuation methods, including the Monte
 Carlo method, the option-pricing method and the hybrid method
 (which is a combination of an option-pricing method and a
 probability-weighted expected return method), all of which
 incorporate assumptions and estimates, to value the preferred stock
 warrants. Estimates and assumptions impacting the fair value
 measurement include the fair value per share of the underlying
 shares of the Company&#x2019;s Series&#xA0;A and Series&#xA0;B
 convertible preferred stock, risk free interest rate, expected
 dividend yield, expected volatility of the price of the underlying
 preferred stock, and either the remaining contractual term of the
 warrants (except for warrants that would be automatically exercised
 upon an initial public offering, in which case the remaining
 estimated term to automatic exercise was used). The most
 significant assumption in the Monte Carlo method, the
 option-pricing method and the hybrid method impacting the fair
 value of the preferred stock warrants is the fair value of the
 Company&#x2019;s convertible preferred stock as of each
 remeasurement date. The Company determines the fair value per share
 of the underlying preferred stock by taking into consideration the
 most recent sales of its convertible preferred stock, results
 obtained from third-party valuations and additional factors that
 are deemed relevant. As of December&#xA0;31, 2018, the fair value
 of the Series&#xA0;A convertible preferred stock was $1.70&#xA0;per
 share the fair value of the Series&#xA0;B convertible preferred
 stock was $1.86&#xA0;per share. There were no warrants for the
 purchase of convertible preferred shares as of March&#xA0;31, 2019
 as all such warrants were converted to warrants for the purchase of
 common stock upon the Merger. The Company has been a private
 company prior to the Merger and lacks company-specific historical
 and implied volatility information of its stock. Therefore, it
 estimates its expected stock volatility based on the historical
 volatility of publicly traded peer companies for a term equal to
 the estimated remaining term of the warrants. The risk-free
 interest rate is determined by reference to the U.S. Treasury yield
 curve for time periods approximately equal to the estimated
 remaining term of the warrants. The Company estimated a 0% expected
 dividend yield based on the fact that the Company has never paid or
 declared dividends and does not intend to do so in the foreseeable
 future.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Valuation of Derivative Liability</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The fair value of the derivative liability recognized in connection
 with the Company&#x2019;s July 2014 license agreement with Genzyme
 (see Note&#xA0;13) was determined based on significant inputs not
 observable in the market, which represents a Level&#xA0;3
 measurement within the fair value hierarchy. The fair value of this
 derivative liability is reported within other liabilities on the
 consolidated balance sheets. The fair value of this derivative
 liability was estimated by the Company at each reporting date
 based, in part, on the results of third-party valuations, which
 were prepared using the option-pricing method or the hybrid method,
 each of which considered as inputs the type, timing and probability
 of occurrence of a change of control event, the potential amount of
 the payment under potential exit scenarios, the fair value per
 share of the underlying common stock and the risk-adjusted discount
 rate. As of December&#xA0;31, 2018, the fair value of this
 derivative liability was $183. The Merger with Arsanis (see Note 1)
 qualified as a change of control event, as defined in the license
 agreement, but results in no payment being due to Genzyme under the
 license agreement. As a result, on March&#xA0;13, 2019, the closing
 date of the Merger with Arsanis, this derivative liability was
 remeasured to fair value, which was $0, and subsequent changes in
 fair value will no longer be recognized in the consolidated
 statements of operations and comprehensive loss because the
 contingent payment obligation to Genzyme expired at that time.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The fair value of the derivative liability recognized in connection
 with the Hercules Loan Agreement (see Note&#xA0;7) was determined
 based on significant inputs not observable in the market, which
 represents a Level&#xA0;3 measurement within the fair value
 hierarchy. The fair value of this derivative liability is reported
 within other liabilities on the consolidated balance sheets. The
 fair value of this derivative liability was estimated by the
 Company at each reporting date based, in part, on the results of
 third-party valuations, which were prepared based on a discounted
 cash flow model that considered the timing and probability of
 occurrence of a redemption upon an event of default, the potential
 amount of prepayment upon an event of default and the risk-adjusted
 discount rate. As of March&#xA0;31, 2019 and December&#xA0;31,
 2018, the fair value of this derivative liability was
 immaterial.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The following table provides a roll-forward of the aggregate fair
 values of the Company&#x2019;s warrant liability, derivative
 liability and preferred stock repurchase liability, for which fair
 values are determined using Level&#xA0;3 inputs:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0">
 <tr>
 <td width="74%"></td>
 <td valign="bottom" width="9%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="9%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Preferred&#xA0;Stock</b><br />
 <b>Warrant</b><br />
 <b>Liability</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Derivative</b><br />
 <b>Liability</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Balance as of December&#xA0;31, 2018</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">4,947</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">201</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Change in fair value</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">288</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(183</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Conversion of convertible preferred stock warrant into common stock
 warrant in connection with Merger</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(5,235</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Balance as of March&#xA0;31, 2019</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">18</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 18pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 </div><span></span>
</td>
</tr>
</table>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 820<br> -URI http://asc.fasb.org/topic&amp;trid=2155941<br></p></div>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6827468144">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Property and Equipment, Net<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
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<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentAbstract', window );"><strong>Property, Plant and Equipment [Abstract]</strong></a></td>
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 Property and equipment, net consisted of the following:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="76%" align="center" border="0">
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 <td valign="bottom">&#xA0;</td>
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 <td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"><b>March&#xA0;31,</b><br />
 <b>2019</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"><b>December&#xA0;31,</b><br />
 <b>2018</b></td>
 <td valign="bottom">&#xA0;</td>
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 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Leasehold improvements</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">&#xA0;&#xA0;&#xA0;&#xA0;299</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">&#xA0;&#xA0;&#xA0;&#xA0;299</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
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 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
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 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Furniture and fixtures</p>
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 <td valign="bottom">&#xA0;&#xA0;</td>
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 <td valign="bottom" align="right">53</td>
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 <td valign="bottom">&#xA0;</td>
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 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
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 Computer equipment</p>
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 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
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 <td valign="bottom">&#xA0;</td>
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 Software</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">9</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
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 Lab equipment</p>
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 &#x2014;&#xA0;&#xA0;</td>
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 &#xA0;</p>
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 &#xA0;</p>
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 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 &#xA0;</p>
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 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
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 Less: Accumulated depreciation and amortization</p>
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 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(177</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
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 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
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 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <td>&#xA0;</td>
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 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <td valign="bottom">$</td>
 <td valign="bottom" align="right">271</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">241</td>
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 &#xA0;</p>
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 &#xA0;</p>
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 &#xA0;</p>
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 &#xA0;</p>
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 Depreciation and amortization expense related to property and
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 2019 and 2018, respectively.</p>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The entire disclosure for long-lived, physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, accounting policies and methodology, roll forwards, depreciation, depletion and amortization expense, including composite depreciation, accumulated depreciation, depletion and amortization expense, useful lives and method used, income statement disclosures, assets held for sale and public utility disclosures.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 360<br> -URI http://asc.fasb.org/topic&amp;trid=2155823<br></p></div>
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<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Accrued Expenses<br></strong></div></th>
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 &#xA0;</p>
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 <b>&#xA0;&#xA0;&#xA0;March&#xA0;31,&#xA0;&#xA0;&#xA0;</b><br />
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 &#xA0;&#xA0;&#xA0;&#xA0;1,239</td>
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 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
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 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Accrued external research and development expenses</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">819</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">754</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Accrued professional fees</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,850</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,324</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Deferred rent, current portion</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">93</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Other</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">271</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">156</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">4,179</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">3,251</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
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 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 18pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6769543104">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Long-Term Debt<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
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<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
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<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtDisclosureAbstract', window );"><strong>Debt Disclosure [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
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<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebtTextBlock', window );">Long-Term Debt</a></td>
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 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
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 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Long-term debt consisted of the following:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0">
 <tr>
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 <td valign="bottom" width="8%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="8%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;March&#xA0;31,&#xA0;&#xA0;&#xA0;</b><br />
 <b>2019</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>December&#xA0;31,</b><br />
 <b>2018</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Principal amount of long-term debt</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19,546</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">10,000</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Less: Current portion of long-term debt</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(5,298</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(1,687</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Long-term debt, net of current portion</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">14,248</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">8,313</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Debt discount, net of accretion</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(1,019</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(226</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Cumulative accretion of final payment due at maturity</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">136</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">58</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Long-term debt, including accretion, net of current portion</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">13,365</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">8,145</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
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 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>SVB Loan Agreement</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In October 2016, the Company entered into a loan and security
 agreement with Silicon Valley Bank (&#x201C;SVB&#x201D;), which the
 Company refers to as the SVB Loan Agreement, pursuant to which SVB
 made certain term loans available to the Company. The SVB Loan
 Agreement provided for a term loan of up to $6,000, which was
 borrowed by the Company in June&#xA0;2017. Borrowings under the SVB
 Loan Agreement bore interest at a variable rate equal to 5.5% plus
 the greater of (i)&#xA0;3.5% or (ii)&#xA0;The Wall Street Journal
 prime rate. In October 2018, in connection with entering into the
 Hercules Loan Agreement, the Company terminated the SVB Loan
 Agreement and repaid all amounts due under the SVB Loan Agreement,
 including unpaid principal of $4,333, a final payment of $270, a
 prepayment premium of $87 and accrued interest of $23. The Company
 accounted for the repayment of amounts as an extinguishment of the
 SVB Loan Agreement and recognized a loss on extinguishment of debt
 of $229 within other income (expense), net in the consolidated
 statement of operations and comprehensive loss. The loss on
 extinguishment of debt was calculated as the difference between the
 reacquisition price of the borrowings under the SVB Loan Agreement
 of $4,713 and the carrying value of the debt under the SVB Loan
 Agreement of $4,484. As of October&#xA0;19, 2018, the date of
 repayment of all borrowings under the SVB Loan&#xA0;Agreement, the
 interest rate applicable to borrowings under the SVB Loan Agreement
 was 10.75%.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Hercules Loan Agreement</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In October 2018, the Company entered into the Hercules Loan
 Agreement, which provided for aggregate borrowings of up to
 $13,000, consisting of (i)&#xA0;a term loan of up to $8,000, which
 was available upon entering into the agreement, (ii)&#xA0;subject
 to specified financing conditions, an additional term loan of up to
 $2,000, available for borrowing from January&#xA0;1, 2019 to
 March&#xA0;31, 2019, and (iii)&#xA0;subject to specified financing
 conditions and the receipt of the second tranche $2,000 term loan
 described above, an additional term loan of up to $3,000, available
 for borrowing until March&#xA0;31, 2019. In October 2018, the
 Company borrowed $8,000 under the Hercules Loan Agreement.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In December 2018, the Company entered into the First Amendment to
 the Hercules Loan Agreement (the &#x201C;First Amendment&#x201D;),
 which amended the available borrowing dates of the second tranche
 from between January&#xA0;1, 2019 and March&#xA0;31, 2019 to
 between December&#xA0;11, 2018 and December&#xA0;14, 2018 and
 amended the term loan maturity date to November&#xA0;1, 2021. In
 December 2018, the Company borrowed the additional $2,000 provided
 under the Hercules Loan Agreement, as amended by the First
 Amendment.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In March&#xA0;2019, the conditions necessary for borrowing the
 remaining $3,000 under the Hercules Loan Agreement were not met and
 the borrowing capacity expired at that time.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Borrowings under the Hercules Loan Agreement bear interest at
 variable rates, with the first tranche bearing interest at a
 variable rate equal to the greater of (i)&#xA0;9.5% or
 (ii)&#xA0;9.5% plus<i>&#xA0;The Wall Street
 Journal</i>&#xA0;prime rate minus 5.25%, the second
 tranche bearing interest at a variable rate, subject to completion
 of specified financing conditions, equal to either (A)&#xA0;the
 greater of (i)&#xA0;9.5% or (ii)&#xA0;9.5%
 plus<i>&#xA0;The Wall Street
 Journal</i>&#xA0;prime rate minus 5.25% or
 (B)&#xA0;the greater of (i)&#xA0;8.75% or (ii)&#xA0;8.75%
 plus<i>&#xA0;The Wall Street
 Journal</i>&#xA0;prime rate minus 5.25%, and the third
 tranche bearing interest at a variable rate equal to the greater of
 (i)&#xA0;8.75% or (ii)&#xA0;8.75% plus<i>&#xA0;The
 Wall Street Journal</i>&#xA0;prime rate minus 5.25%.
 In an event of default, as defined, and until such event is no
 longer continuing, the interest rate applicable to borrowings under
 the Hercules Loan Agreement would be increased by 4.0%. As of
 March&#xA0;31, 2019 and December&#xA0;31, 2018, the interest rate
 applicable to borrowings under the Hercules Loan Agreement was
 9.80% and 9.75%.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Borrowings under the Hercules Loan Agreement are repayable in
 monthly interest-only payments through August 2019, or a later date
 upon achievement of specified conditions, and in equal monthly
 payments of principal and accrued interest from September 2019
 until the maturity date of the loan, which is November 2021. At the
 Company&#x2019;s option, the Company may prepay all, but not less
 than all, of the outstanding borrowings, subject to a prepayment
 premium of up to 2.0% of the principal amount outstanding as of the
 date of repayment. The Hercules Loan Agreement also provides for a
 final payment, payable upon maturity or the repayment in full of
 all obligations under the agreement, of up to $953. An aggregate
 final payment of $794 payable in connection with the $8,000 term
 loan and the $2,000 term loan is being accreted to interest expense
 to increase the carrying value of the debt over the term of the
 loan using the effective interest method.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In addition, the Hercules Loan Agreement contains a redemption
 feature that, upon an event of default, provides Hercules the
 option to accelerate and demand repayment of the debt, including a
 prepayment premium. The Company concluded that the redemption
 feature meets the definition of a derivative instrument as the
 repayment of the debt contains a substantial premium, resulting in
 the redemption feature not being clearly and closely related to the
 host instrument. The Company recorded the issuance-date fair value
 of the derivative liability of $18 as a debt discount and as a
 derivative liability on its consolidated balance sheet.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Borrowings under the Hercules Loan Agreement are collateralized by
 substantially all of the Company&#x2019;s personal property and
 other assets, including its intellectual property until a specified
 financing condition is met. Under the Hercules Loan Agreement, the
 Company has agreed to affirmative and negative covenants to which
 the Company will remain subject until maturity or repayment in
 full. The covenants include maintaining a minimum liquidity amount
 of the lesser of (i)&#xA0;125% of outstanding borrowings under the
 Hercules Loan Agreement and (ii)&#xA0;100% of the Company&#x2019;s
 cash and cash equivalents in an account in which Hercules has a
 first priority security interest as well as restrictions on the
 Company&#x2019;s ability to incur additional indebtedness, pay
 dividends, encumber its intellectual property, or engage in certain
 fundamental business transactions, such as mergers or acquisitions
 of other businesses. Obligations under the Hercules Loan Agreement
 are subject to acceleration upon occurrence of specified events of
 default, including payment default, insolvency and a material
 adverse change in the Company&#x2019;s business, operations or
 financial or other condition.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In connection with entering into the Hercules Loan Agreement in
 October 2018, the Company issued to Hercules warrants for the
 purchase of 210,638&#xA0;shares of Series&#xA0;B convertible
 preferred stock at an exercise price of $1.88 per share. These
 warrants were immediately exercisable and expire in October
 2028.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In connection with entering into the First Amendment in December
 2018, the Company agreed to issue to Hercules warrants for the
 purchase of a specified number of shares of convertible preferred
 stock or, if issued following the Merger with Arsanis, a specified
 number of shares of common stock of the combined organization, at
 an aggregate exercise price of $99. The warrants were to be issued
 at the earliest of (i)&#xA0;June&#xA0;30, 2019, (ii)&#xA0;the
 earlier to occur of (a)&#xA0;the date the Company prepays the
 outstanding borrowings or (b)&#xA0;the date the outstanding
 borrowings become due and payable, or (iii)&#xA0;on or before the
 fifth business day following the closing of or the announcement of
 the termination of the Company&#x2019;s Merger with Arsanis. The
 number of shares of convertible preferred stock issuable upon
 exercise of these warrants was determined to be 52,659 shares,
 calculated by dividing $99 by the $1.88 price per share paid by
 investors that purchased shares of Series&#xA0;B convertible
 preferred stock in September 2018 (see Note&#xA0;11). On
 March&#xA0;18, 2019, as a result of the closing of the Merger with
 Arsanis on March&#xA0;13, 2019, the Company issued to Hercules
 warrants for the purchase of 5,000 shares of common stock of the
 combined organization at an exercise price of $19.80 per share,
 each of which reflected the share Exchange Ratio
 of&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">1-for-0.5702</font></font>&#xA0;applied
 in the Merger as well as the Reverse Stock Split effected by the
 combined organization on March&#xA0;13, 2019.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 On October&#xA0;19, 2018 and December&#xA0;11, 2018, the dates the
 Company entered into the Hercules Loan Agreement and the First
 Amendment, respectively, the Company recorded the aggregate initial
 fair value of the warrants of $132 as a preferred stock warrant
 liability, with a corresponding amount recorded as a debt discount
 on the Company&#x2019;s consolidated balance sheet. As of
 March&#xA0;13, 2019 and December&#xA0;31, 2018, the fair value of
 the warrants was $326 and $282, respectively. Upon the closing of
 the Merger, the warrants were converted to warrants for common
 stock and are no longer adjusted to fair value.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In connection with entering into the Hercules Loan Agreement and
 the First Amendment, the Company also paid Hercules $92 of upfront
 fees, including facility, due diligence and legal fees associated
 with entering into the agreement, which were also recorded as a
 debt discount. The debt discount is reflected as a reduction of the
 carrying value of long-term debt on the Company&#x2019;s
 consolidated balance sheet and is being amortized to interest
 expense over the term of the loan using the effective interest
 method.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The Company recognized aggregate interest expense under the
 Hercules Loan Agreement of $357 and $0 during three months ended
 March&#xA0;31, 2019 and 2018, respectively, which
 included&#xA0;<font style="WHITE-SPACE: nowrap">non-cash</font>&#xA0;interest
 expense of $113 related to the accretion of the debt discount and
 the final payment. As of March&#xA0;31, 2019 and December&#xA0;31,
 2018, the unamortized debt discount was $182 and $226,
 respectively. The Company&#x2019;s annual effective interest rate of
 the Hercules Loan Agreement as of March&#xA0;31, 2019 and
 December&#xA0;31, 2018 was approximately 14.2%, respectively.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 There were no principal payments due or paid under the Hercules
 Loan Agreement during the three months ended March&#xA0;31, 2019.
 Principal payments begin in September 2019.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>FFG Loan Agreement</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Between September 2011 and March 2017, Arsanis GmbH, a subsidiary
 of Arsanis, entered into a series of funding agreements with
 &#xD6;sterreichische Forschungsf&#xF6;rderungsgesellschaft mbH
 (&#x201C;FFG&#x201D;) that provided for loans and grants to fund
 qualifying research and development expenditures of Arsanis GmbH on
 a&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">project-by-project</font></font>&#xA0;basis,
 as approved by FFG. Amounts due under the FFG loans bear interest
 at rates ranging from 0.75% to 2.0%&#xA0;per annum. As of
 March&#xA0;31, 2019, giving effect to the Settlement Agreement (as
 defined below), the loans matured at various dates between
 March&#xA0;31, 2019 and March 2021. Interest on amounts due under
 the loans is payable semi-annually in arrears, with all principal
 and remaining accrued interest due upon maturity.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 As of March&#xA0;31, 2019, the outstanding principal amount under
 loans from FFG was $9,546, including $2,914 of current portion.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 On March&#xA0;8, 2019, Arsanis, Merger Sub, X4 and Arsanis GmbH, a
 wholly owned subsidiary of Arsanis, entered into the Settlement
 Agreement with FFG (the &#x201C;Settlement Agreement&#x201D;) in
 respect to allegations by FFG in February 2019 that Arsanis and
 Arsanis GmbH breached certain reporting, performance and other
 obligations in connection with grants and loans made by FFG to
 Arsanis GmbH between September 2011 and March 2017 to fund
 qualifying research and development expenditures. Pursuant to the
 terms of the Settlement Agreement, in exchange for FFG&#x2019;s
 waiver of all claims against Arsanis and Arsanis GmbH (except for
 its claims for repayment of the loans and regular interest but
 including its waiver of claims for repayment of grants and interest
 exceeding regular interest), subject to compliance by Arsanis and
 Arsanis GmbH with the terms of the Settlement Agreement, Arsanis
 GmbH agreed to repay the outstanding loan principal (plus regular
 interest accrued thereon) on an accelerated payment schedule of
 three years instead of five years, with the final accelerated
 installment due and payable on June&#xA0;30, 2021. The parties also
 agreed, among other things, that (i)&#xA0;the portion of such loans
 to be repaid in 2019 is $2,914&#xA0;on the first
 business day following&#xA0;March&#xA0;31, 2019 and
 (ii)&#xA0;until all of the loans have been repaid and subject to
 other terms specified in the Settlement Agreement, commencing
 April&#xA0;30, 2019, a minimum cash balance equal to 70% of the
 then-outstanding principal amount of the loans will be maintained
 at Arsanis GmbH in an account held with an Austrian bank.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 As of March&#xA0;31, 2019, future principal payments and the final
 payment due under the Company&#x2019;s loan agreements were as
 follows:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0">
 <tr>
 <td width="61%"></td>
 <td valign="bottom" width="5%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="5%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="5%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">Year Ending December&#xA0;31,</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Hercules</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>FFG</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Total</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2019</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1,345</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">2,914</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">4,259</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2020</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">4,305</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">4,462</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">8,767</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2021</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">4,350</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">2,170</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">6,520</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Long-term debt</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">
 &#xA0;&#xA0;&#xA0;&#xA0;10,000</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">
 &#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;9,546</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19,546</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 18pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 </div><span></span>
</td>
</tr>
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<div style="display: none;">
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The entire disclosure for long-term debt.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 470<br> -URI http://asc.fasb.org/topic&amp;trid=2208564<br></p></div>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6817692496">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Leases<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LeasesAbstract', window );"><strong>Leases [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LeasesOfLesseeDisclosureTextBlock', window );">Leases</a></td>
<td class="text"><div>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="break-inside: avoid">
 <td valign="top" width="4%" align="left"><b>8.</b></td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left"><b>Leases</b></p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Effective January&#xA0;1, 2019, the Company adopted ASC 842 using
 the modified retrospective approach through a cumulative-effect
 adjustment and utilizing the effective date as its date of initial
 application, with prior periods unchanged and presented in
 accordance with the previous lease accounting guidance. Upon
 adoption, the Company recorded&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font>&#xA0;assets
 of $2,026 and lease liabilities of $2,538, of which $1,925 was
 classified as&#xA0;<font style="WHITE-SPACE: nowrap">non-current</font>&#xA0;and $613
 as current. The difference between the value of
 the&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font>&#xA0;asset
 and the lease liabilities relates to $512 of net deferred, accrued
 and prepaid rent that was reclassified against
 the&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font>&#xA0;asset
 upon adoption of ASC 842 on January&#xA0;1, 2019. The Company has
 lease agreements for its facilities in Cambridge, Massachusetts,
 which is the Company&#x2019;s global headquarters, Vienna, Austria,
 which is the Company&#x2019;s research and development center, and
 Waltham, Massachusetts, which is the former headquarters of
 Arsanis. The Company plans to sublease its Waltham, Massachusetts
 facility. There are no restrictions or financial covenants
 associated with any of the lease agreements.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <i>Cambridge Lease</i></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In August 2017, the Company entered into a lease agreement for
 office space of approximately thirteen thousand square feet in
 Cambridge, Massachusetts (&#x201C;Cambridge Lease&#x201D;) which
 expires on July&#xA0;31, 2022. The Cambridge lease includes an
 annual rent escalation clause and the Company has the option to
 extend the lease for one period of five additional years. Base rent
 is approximately $810 annually and the monthly rent expense is
 being recognized on a straight-line basis over the term of the
 lease. In addition to the base rent, the Company is also
 responsible for its share of operating expenses, electricity and
 real estate taxes, in accordance with the terms of lease. These
 costs are classified as variable lease payments and are not
 included in the determination of the
 leases&#x2019;&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font>&#xA0;operating
 assets or lease operating liabilities.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <i>Waltham Lease</i></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 On March&#xA0;13, 2019, as part of its Merger with Arsanis, the
 Company acquired an operating lease for approximately six thousand
 square feet of office space in Waltham, Massachusetts
 (&#x201C;Waltham Lease&#x201D;). The Waltham lease, as amended,
 commenced on January&#xA0;1, 2019, and expires approximately 5
 years from the commencement date. The base rent is approximately
 $459 annually. In addition to the base rent, the Company is also
 responsible for its share of operating expenses, electricity and
 real estate taxes, in accordance with the terms of the Amended
 Lease Agreement. These costs are classified as variable lease
 payments and are not included in the determination of the
 leases&#x2019;&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font>&#xA0;assets
 or lease liabilities.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <i>Vienna Lease</i></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 On March&#xA0;13, 2019, as part of its Merger with Arsanis, the
 Company acquired an operating lease for approximately four hundred
 square meters of laboratory and office space in Vienna, Austria,
 which commenced on March&#xA0;1, 2019, as amended, for a term of
 two years. The lease is cancellable by the Company upon three
 month&#x2019;s notice with no penalty. The annual base rent is
 approximately $155. The Company has classified this lease as a
 short-term lease as it is not reasonably certain that the Company
 with not terminate the lease within one year and, accordingly, has
 not recorded a&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font>&#xA0;asset.
 Accordingly, rent expense is recorded on a straight-line basis as
 incurred over the term of the lease.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 As the Company&#x2019;s leases do not provide an implicit rate, the
 Company estimated the incremental borrowing rate in calculating the
 present value of the lease payments. The Company utilizes its
 incremental borrowing rates, which are the rates incurred to borrow
 on a collateralized basis over a similar term an amount equal to
 the lease payments in a similar economic environment.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The components of lease expense for the three months ended
 March&#xA0;31, 2019 were as follows:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0">
 <tr>
 <td width="72%"></td>
 <td valign="bottom" width="25%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom" nowrap="nowrap"><font style="FONT-SIZE: 10pt"><b>Lease Cost</b></font></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>For&#xA0;the&#xA0;three&#xA0;months&#xA0;ended</b><br />
 <b>March&#xA0;31, 2019</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Fixed operating lease cost</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">187</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Short-term lease costs</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">8</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Total lease expense</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">195</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 <b>Other information</b></p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Cash paid for amounts included in the measurement of lease
 liabilities:</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 5em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Operating cash flows from operating leases</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">201</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Leased assets obtained in exchange for new operating lease
 liabilities&#xA0;(1)</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">781</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Weighted-average remaining lease term&#x2014;operating leases</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">3.9&#xA0;years</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Weighted-average discount rate&#x2014;operating leases</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">9.0</td>
 <td valign="bottom" nowrap="nowrap">%&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="break-inside: avoid">
 <td valign="top" width="4%" align="left">(1)</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left">Acquired in Merger with Arsanis</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Maturities of lease liabilities due under these lease agreements as
 of March&#xA0;31, 2019 are as follows:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0">
 <tr>
 <td width="81%"></td>
 <td valign="bottom" width="14%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom" nowrap="nowrap">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; BORDER-BOTTOM: rgb(0,0,0) 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell">
 <b>Maturity of lease liabilities</b></p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Operating&#xA0;Leases</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2019 (remainder of 2019)</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">837</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2020</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,281</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2021</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,304</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2022</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">970</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2023</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">489</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Thereafter</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Total lease payments</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">4,880</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Less: interest</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(764</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Total operating lease liabilities as of March&#xA0;31, 2019</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">4,116</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The Company adopted ASU&#xA0;<font style="WHITE-SPACE: nowrap">2016-02</font>&#xA0;on
 January&#xA0;1, 2019 as noted above, and as required, the following
 disclosure is provided for periods prior to adoption. Future annual
 minimum lease payments due under the Company&#x2019;s operating
 leases as of December&#xA0;31, 2018 were as follows:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0">
 <tr>
 <td width="81%"></td>
 <td valign="bottom" width="14%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom" nowrap="nowrap">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; BORDER-BOTTOM: rgb(0,0,0) 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell">
 <b>Year Ending December&#xA0;31,</b></p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Operating&#xA0;Leases</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2019</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">810</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2020</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">823</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2021</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">835</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2022</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">492</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Total</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">2,960</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 </table>
 <br class="Apple-interchange-newline" />

 </div><span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LeasesAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LeasesAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LeasesOfLesseeDisclosureTextBlock">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The entire disclosure for lessee entity's leasing arrangements including, but not limited to, all of the following: (a.) The basis on which contingent rental payments are determined, (b.) The existence and terms of renewal or purchase options and escalation clauses, (c.) Restrictions imposed by lease agreements, such as those concerning dividends, additional debt, and further leasing.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -URI http://asc.fasb.org/subtopic&amp;trid=77888251<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 840<br> -URI http://asc.fasb.org/topic&amp;trid=2208923<br></p></div>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6827346560">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Commitment and Contingencies<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommitmentsAndContingenciesDisclosureAbstract', window );"><strong>Commitments and Contingencies Disclosure [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock', window );">Commitment and Contingencies</a></td>
<td class="text"><div>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="break-inside: avoid">
 <td valign="top" width="4%" align="left"><b>9.</b></td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left"><b>Commitment and Contingencies</b></p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Sponsored Research Agreement Commitments</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In April&#xA0;2017, the Company entered into a sponsored research
 agreement with a university that the Company refers to as the
 Sponsored Research Agreement, pursuant to which the Company and the
 university intend to conduct a research program related to
 understanding the mechanisms of failed long-term adaptive immunity
 in WHIM patients. Under the terms of the Sponsored Research
 Agreement, the Company agreed to provide funding for the research
 program of up to $499 over a three-year period. The Sponsored
 Research Agreement will remain in effect for three years, unless
 earlier terminated in the event that (i)&#xA0;either party
 materially breaches any representation, obligation or covenant and
 fails to remedy such breach within 30 days after receipt of notice
 or (ii)&#xA0;the Principal Investigator, as defined in the
 agreement, is unable or unwilling to conduct the research or
 perform his or her obligations under the agreement, at which time
 the Company may terminate the agreement upon 30 days&#x2019; prior
 written notice to the university. The Company may terminate the
 agreement at any time upon at least 60 days&#x2019; prior written
 notice.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 During the three months ended March&#xA0;31, 2019 and 2018, the
 Company incurred $42, respectively, of research and development
 expenses related to its payment obligations to the university under
 the Sponsored Research Agreement. As of March&#xA0;31, 2019, the
 Company had&#xA0;<font style="WHITE-SPACE: nowrap">non-cancelable</font>&#xA0;purchase
 commitments under this agreement totaling $181, with $125 committed
 in 2019 and $56 committed in 2020.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Manufacturing Commitments</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 As of March&#xA0;31, 2019, the Company entered into agreements with
 several contract manufacturing organizations to provide preclinical
 and clinical trial materials. As of March&#xA0;31, 2019, and
 December&#xA0;31, 2018, the Company
 had&#xA0;<font style="WHITE-SPACE: nowrap">non-cancelable</font>&#xA0;purchase
 commitments under these agreements totaling approximately $250, all
 committed in 2019.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Indemnification Agreements</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In the ordinary course of business, the Company may provide
 indemnification of varying scope and terms to vendors, lessors,
 business partners and other parties with respect to certain matters
 including, but not limited to, losses arising out of breach of such
 agreements or from intellectual property infringement claims made
 by third parties. In addition, the Company has entered into
 indemnification agreements with members of its board of directors
 and its executive officers that will require the Company to, among
 other things, indemnify them against certain liabilities that may
 arise by reason of their status or service as directors or
 officers. The maximum potential amount of future payments the
 Company could be required to make under these indemnification
 agreements is, in many cases, unlimited. To date, the Company has
 not incurred any material costs as a result of such indemnification
 obligations. The Company is not currently aware of any
 indemnification claims and has not accrued any liabilities related
 to such obligations in its consolidated financial statements as of
 March&#xA0;31, 2019 or December&#xA0;31, 2018.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>License Agreements</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Arsanis entered into an agreement (the &#x201C;Adimab Option
 Agreement&#x201D;) in February 2017, which was acquired by the
 Company as a result of the Merger, under which the Company is
 obligated to make contingent and&#xA0;<font style="WHITE-SPACE: nowrap">non-contingent</font>&#xA0;payments
 should the Company exercise its option to obtain rights to certain
 RSV antibodies. If the Company chose to exercise its option, it
 would be obligated to pay Adimab an option fee of approximately
 $250 and make clinical and regulatory milestone payments of up to
 approximately $25,000, as well as royalty payments on
 a&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">product-by-product</font></font>&#xA0;and&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">country-by-country</font></font>&#xA0;basis
 of a mid single-digit percentage based on net sales by the Company,
 its affiliates, licensees or sublicensees of products based on
 certain RSV antibodies during the applicable term for such product
 in that country. The Company may choose to exercise its option
 under the terms of the Adimab Option Agreement at any time on or
 before August&#xA0;31, 2019. As of March&#xA0;31, 2019, the Company
 had not exercised its option under the Adimab Option Agreement.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Legal Proceedings</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The Company is not a party to any litigation and does not have
 contingency reserves established for any litigation liabilities. At
 each reporting date, the Company evaluates whether or not a
 potential loss amount or a potential range of loss is probable and
 reasonably estimable under the provisions of the authoritative
 guidance that addresses accounting for contingencies. The Company
 expenses as incurred the costs related to such legal
 proceedings</p>
 </div><span></span>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The entire disclosure for commitments and contingencies.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 450<br> -URI http://asc.fasb.org/topic&amp;trid=2127136<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 440<br> -URI http://asc.fasb.org/topic&amp;trid=2144648<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6827320864">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Preferred and Common Stock Warrants<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
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<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock', window );">Preferred and Common Stock Warrants</a></td>
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 <tr style="break-inside: avoid">
 <td valign="top" width="4%" align="left"><b>10.</b></td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left"><b>Preferred and Common Stock Warrants</b></p>
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 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 As of March&#xA0;31, 2019, the Company&#x2019;s outstanding warrants
 to purchase shares of common stock consisted of the following:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="80%" align="center" border="0">
 <tr>
 <td width="60%"></td>
 <td valign="bottom" width="3%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="3%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="3%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="3%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom" nowrap="nowrap">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; BORDER-BOTTOM: rgb(0,0,0) 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell">
 <b>Issuance Date</b></p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Number&#xA0;of</b><br />
 <b>Shares of</b><br />
 <b>Common</b><br />
 <b>Stock&#xA0;Issuable</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Exercise</b><br />
 <b>Price</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Classification</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Expiration&#xA0;Date</b></td>
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 August&#xA0;14, 2015</p>
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 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">81,228</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
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 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">August&#xA0;14,&#xA0;2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 August&#xA0;21, 2015</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">69,603</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">21.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">August&#xA0;21, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 October&#xA0;25, 2016</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">5,155</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;24, 2026</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 November&#xA0;1, 2017</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">130,609</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;31,&#xA0;2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 November&#xA0;17, 2017</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">8,442</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">November&#xA0;16, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 December&#xA0;4, 2017</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">5,661</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;3, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 December&#xA0;28, 2017</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">6,925</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;27, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 December&#xA0;28, 2017</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">115,916</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;28, 2027</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 September&#xA0;12, 2018</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">25,275</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">September&#xA0;12,&#xA0;2021</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 September&#xA0;12, 2018</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">20,220</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">September&#xA0;12, 2028</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 October&#xA0;19, 2018</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">20,016</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;19, 2028</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 December&#xA0;11, 2018</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">5,004</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.80</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;19, 2028</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">494,054</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 As of December&#xA0;31, 2018, the Company&#x2019;s outstanding
 warrants to purchase shares of preferred stock (which converted
 into warrants to purchase common stock upon close of the Merger)
 consisted of the following (not adjusted for the Reverse Stock
 Split or Exchange Ratio):</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" align="center" border="0">
 <tr>
 <td width="32%"></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="24" nowrap="nowrap" align="center">
 <p style="MARGIN-BOTTOM: 1pt; FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="center"><b>December&#xA0;31, 2018</b></p>
 </td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 9pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom" nowrap="nowrap">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 9pt; FONT-FAMILY: &quot;Times New Roman&quot;; BORDER-BOTTOM: rgb(0,0,0) 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell">
 <b>Warrant Name</b></p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Issuance Date</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Number&#xA0;of</b><br />
 <b>Shares of</b><br />
 <b>Preferred</b><br />
 <b>Stock&#xA0;Issuable</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Exercise</b><br />
 <b>Price</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Exercisable</b><br />
 <b>for</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Classification</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Expiration Date</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series A warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">August&#xA0;14, 2015</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">854,785</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">2.07</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series&#xA0;A</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">August&#xA0;14, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series A warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">August&#xA0;21, 2015</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">732,453</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">2.07</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series A</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">August&#xA0;21, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 SVB warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;25, 2016</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">54,256</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series A</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;24, 2026</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">November&#xA0;1, 2017</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,374,435</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;31, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">November&#xA0;17, 2017</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">88,845</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">November&#xA0;16, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;4, 2017</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">59,576</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;3, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;28, 2017</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">72,875</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;27, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;28, 2017</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,219,815</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;28, 2027</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">September&#xA0;12, 2018</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">265,957</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">September&#xA0;12,&#xA0;2021</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">September&#xA0;12,&#xA0;2018</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">212,765</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">September&#xA0;12, 2028</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;19, 2018</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">210,638</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;19, 2028</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">5,146,400</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Prior to the Merger, the Company classified its preferred stock
 warrants as a liability on its consolidated balance sheet because
 the warrants are freestanding financial instruments that may have
 required the Company to transfer assets upon exercise. The
 liability associated with each of these warrants was initially
 recorded at fair value upon the issuance date of each warrant and
 is subsequently remeasured to fair value as a component of other
 income (expense), net in the consolidated statement of operations
 and comprehensive loss. Upon the closing of the Merger with Arsanis
 (see Note 1), pursuant to the Merger Agreement, all of the
 outstanding X4 preferred stock was converted to Arsanis common
 stock and the X4 preferred stock warrants converted to warrants for
 the purchase of Arsanis common stock. The Company assessed the
 features of the warrants and determined that they qualify for
 classification as permanent equity upon the closing of the Merger.
 Accordingly, the Company remeasured the warrants to fair value upon
 the closing of the Merger, which was $5,235 at March&#xA0;13, 2019,
 with $288 of expense recorded during the three months ended
 March&#xA0;31, 2019. Upon the closing of the Merger, the warrant
 liability was reclassified to
 additional&#xA0;<font style="WHITE-SPACE: nowrap">paid-in</font>&#xA0;capital.&#xA0;&#xA0;&#xA0;&#xA0;</p>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract</td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 815<br> -URI http://asc.fasb.org/topic&amp;trid=2229140<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6817726848">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Common Stock, Redeemable Common Stock, and Convertible Preferred Stock<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FederalHomeLoanBanksAbstract', window );"><strong>Federal Home Loan Banks [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockholdersEquityNoteDisclosureTextBlock', window );">Common Stock, Redeemable Common Stock, and Convertible Preferred Stock</a></td>
<td class="text"><div>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="break-inside: avoid">
 <td valign="top" width="4%" align="left"><b>11.</b></td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left"><b>Common Stock, Redeemable Common Stock, and
 Convertible Preferred Stock (converted to Common Stock)</b></p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Common Stock</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 As of March&#xA0;31, 2019 and December&#xA0;31, 2018, the
 Company&#x2019;s certificate of incorporation, as amended and
 restated, authorized the Company to issue 33,333,333 shares and
 11,070,776, shares, respectively, of $0.001 par value common stock.
 The voting, dividend and liquidation rights of the holders of the
 Company&#x2019;s common stock are subject to and qualified by the
 rights, powers and preferences of the holders of the preferred
 stock.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Each share of common stock entitles the holder to one vote on all
 matters submitted to a vote of the Company&#x2019;s stockholders.
 Common stockholders are entitled to receive dividends, as may be
 declared by the board of directors, if any. Through March&#xA0;31,
 2019 and December&#xA0;31, 2018, no cash dividends had been
 declared or paid.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Redeemable Common Stock</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Pursuant to the requirements of the July 2014 license agreement
 with Genzyme (see Note&#xA0;13), in August 2015, the Company issued
 to Genzyme for no additional consideration 107,371, as adjusted for
 the Reverse Stock Split and Exchange Ratio, shares of common stock,
 which had an aggregate fair value of $734 on the date of issuance.
 Genzyme had the right to require the Company to repurchase all, but
 not less than all, of these shares of common stock at any time
 during the term of the license agreement for a price of $0.01 per
 share. Because of this redemption feature, the shares of common
 stock issued to Genzyme were classified outside of
 stockholders&#x2019; deficit on the consolidated balance sheets. As
 a result of the Merger, these shares were exchanged for common
 stock.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Convertible Preferred Stock (converted to Common
 Stock)</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The Company has issued Series Seed convertible preferred stock (the
 &#x201C;Series Seed preferred stock&#x201D;), Series&#xA0;A
 convertible preferred stock (the &#x201C;Series&#xA0;A preferred
 stock&#x201D;) and Series&#xA0;B convertible preferred stock (the
 &#x201C;Series&#xA0;B preferred stock&#x201D;). As of March&#xA0;31,
 2019 and December&#xA0;31, 2018, the Company&#x2019;s certificate of
 incorporation, as amended and restated, authorized the Company to
 issue a total of 10,000,000 shares and 59,413,523 shares,
 respectively, of preferred stock, with a par value of $0.001 per
 share.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The holders of Preferred Stock have liquidation rights in the event
 of a deemed liquidation that, in certain situations, are not solely
 within the control of the Company. Therefore, the Preferred Stock
 is classified outside of stockholders&#x2019; deficit on the
 consolidated balance sheet.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 As of March&#xA0;31, 2019, there were no preferred stock
 outstanding. As of December&#xA0;31, 2018, the Preferred Stock
 consisted of the following:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" align="center" border="0">
 <tr>
 <td width="57%"></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="18" align="center"><b>December&#xA0;31, 2018</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Preferred</b><br />
 <b>Stock</b><br />
 <b>Designated</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Preferred</b><br />
 <b>Stock</b><br />
 <b>Issued and</b><br />
 <b>Outstanding</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Carrying</b><br />
 <b>Value</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Liquidation</b><br />
 <b>Preference</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Common<br />
 Stock</b><br />
 <b>Issuable<br />
 Upon</b><br />
 <b>Conversion(1)</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series Seed preferred stock</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">2,313,523</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,516,136</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1,310</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1,444</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">143,630</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series A preferred stock</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">22,000,000</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">19,946,862</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">32,480</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">47,624</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,895,610</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B preferred stock</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">25,100,000</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">18,616,569</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">30,885</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">34,999</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,769,190</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">49,413,523</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">40,079,567</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">64,675</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">84,067</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">3,808,430</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="break-inside: avoid">
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 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left">Adjusted to reflect Reverse Stock Split and Exchange
 Ratio.</p>
 </td>
 </tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FederalHomeLoanBanksAbstract</td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -URI http://asc.fasb.org/topic&amp;trid=2208762<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockholdersEquityNoteDisclosureTextBlock</td>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6828044880">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Stock-Based Compensation<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract', window );"><strong>Disclosure of Compensation Related Costs, Share-based Payments [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock', window );">Stock-Based Compensation</a></td>
<td class="text"><div>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="break-inside: avoid">
 <td valign="top" width="4%" align="left"><b>12.</b></td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left"><b>Stock-Based Compensation</b></p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Summary of Plans</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Upon completion of the Merger with Arsanis on March&#xA0;13, 2019,
 X4&#x2019;s 2015 Employee, Director and Consultant Equity Incentive
 Plan, as amended (the &#x201C;2015 Plan&#x201D;), Arsanis&#x2019; 2017
 Equity Incentive Plan (the &#x201C;2017 Plan&#x201D;) and
 Arsanis&#x2019; 2017 Employee Stock Purchase Plan (the &#x201C;2017
 ESPP&#x201D;) (collectively, the &#x201C;Plans&#x201D;) were assumed
 by the Company. These Plans are administered by the board of
 directors or, at the discretion of the board of directors, by a
 committee of the board of directors. The exercise prices, vesting
 and other restrictions are determined at the discretion of the
 board of directors, or its committee if so delegated, except that
 the exercise price per share of stock options may not be less than
 100% of the fair market value of the share of common stock on the
 date of grant and the term of the stock option may not be greater
 than ten years. Incentive stock options granted to employees and
 restricted stock awards granted to employees, officers, members of
 the board of directors, advisors, and consultants of the Company
 typically vest over four years.&#xA0;<font style="WHITE-SPACE: nowrap">Non-statutory</font>&#xA0;options
 granted to employees, officers, members of the board of directors,
 advisors, and consultants of the Company typically vest over three
 or four years. Shares that are expired, terminated, surrendered or
 canceled under the Plans without having been fully exercised will
 be available for future awards. In addition, shares of common stock
 that are tendered to the Company by a participant to exercise an
 award are added to the number of shares of common stock available
 for the grant of awards.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>2015 Employee, Director and Consultant Equity Incentive
 Plan</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In 2015, the board of directors and shareholders of X4 adopted the
 2015 Plan, which provided for the Company to grant incentive stock
 options or nonqualified stock options, restricted stock awards and
 other stock-based awards to employees, directors and consultants of
 the Company. Each stock option outstanding under the 2015 Plan at
 the effective time of the Merger was automatically converted into a
 stock option exercisable for a number of shares of the
 Company&#x2019;s common stock calculated based on the Exchange Ratio
 and the exercise price per share of such outstanding stock
 option.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The total number of shares of common stock that may be issued under
 the 2015 Plan was 1,700,000 shares, adjusted for the reverse stock
 split as of December&#xA0;31, 2018 and March&#xA0;31, 2019. Shares
 that are expired, forfeited, canceled or otherwise terminated
 without having been fully exercised will be available for future
 grant under the 2015 Plan. In addition, shares of common stock that
 are tendered to the Company by a participant to exercise an award
 are added to the number of shares of common stock available for
 future grants.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>2017 Equity Incentive Plan</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In 2017, the board of directors and shareholders of Arsanis adopted
 the 2017 Plan which provided for the Company to grant incentive
 stock options,&#xA0;<font style="WHITE-SPACE: nowrap">non-qualified</font>&#xA0;options,
 stock appreciation rights, restricted stock awards, restricted
 stock units and other stock-based awards. Incentive stock options
 may be granted only to the Company&#x2019;s employees, including
 officers and directors who are also employees. Awards other than
 incentive stock options may be granted to employees, officers,
 members of the board of directors, advisors and consultants of the
 Company. The number of shares of common stock reserved for issuance
 under this plan will automatically increase on January&#xA0;1 of
 each year, through January&#xA0;1, 2027, in an amount equal to the
 lowest of 1,025,490 shares of the Company&#x2019;s common stock, 4%
 of the number of shares of the Company&#x2019;s common stock
 outstanding on January&#xA0;1 of each year and an amount determined
 by the Company&#x2019;s board of directors.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>2017 Employee Stock Purchase Plan</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In 2017, the board of directors and shareholders of Arsanis adopted
 the 2017 ESPP. The 2017 ESPP provides participating employees with
 the opportunity to purchase shares of the Company&#x2019;s common
 stock at defined purchase prices
 over&#xA0;<font style="WHITE-SPACE: nowrap">six-month</font>&#xA0;offering
 periods. For the three month period ended March&#xA0;31, 2019, no
 shares of common stock were issued under the 2017 ESPP.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Stock Option Valuation</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The fair value of stock option grants is estimated using the
 Black-Scholes option-pricing model. The Company has historically
 been a private company prior to March&#xA0;13, 2019, and as a
 result, lacked company-specific historical and implied volatility
 information. The Company estimated expected stock volatility based
 on the historical volatility of a publicly traded set of peer
 companies and expects to continue to do so until it has adequate
 historical data regarding the volatility of its own traded stock
 price. For options with service-based vesting conditions, the
 expected term of the Company&#x2019;s stock options has been
 determined utilizing the &#x201C;simplified&#x201D; method for awards
 that qualify as &#x201C;plain-vanilla&#x201D; options. The expected
 term of stock options granted&#xA0;<font style="WHITE-SPACE: nowrap">to&#xA0;non-employee&#xA0;consultants</font>&#xA0;is
 equal to the contractual term of the option award. The risk-free
 interest rate is determined by reference to the U.S. Treasury yield
 curve in effect at the time of grant of the award for time periods
 approximately equal to the expected term of the award. Expected
 dividend yield is based on the fact that the Company has never paid
 cash dividends and does not expect to pay any cash dividends in the
 foreseeable future.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The following table presents, on a weighted average basis, the
 assumptions used in the Black-Scholes option-pricing model to
 determine the grant-date fair value of stock options granted to
 employees, directors and&#xA0;<font style="WHITE-SPACE: nowrap">non-</font>&#xA0;employees:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0">
 <tr>
 <td width="80%"></td>
 <td valign="bottom" width="7%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="7%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="6" align="center"><b>Three Months Ended<br />
 March&#xA0;31,</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;2019&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;2018&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Risk-free interest rate</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">2.4</td>
 <td valign="bottom" nowrap="nowrap">%&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">2.8</td>
 <td valign="bottom" nowrap="nowrap">%&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Expected term (in years)</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">5.90</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">5.94</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Expected volatility</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">90.6</td>
 <td valign="bottom" nowrap="nowrap">%&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">86.0</td>
 <td valign="bottom" nowrap="nowrap">%&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Expected dividend yield</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">0</td>
 <td valign="bottom" nowrap="nowrap">%&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">0</td>
 <td valign="bottom" nowrap="nowrap">%&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Stock Options</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The following table summarizes the Company&#x2019;s stock option
 activity since December&#xA0;31, 2018:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="92%" align="center" border="0">
 <tr>
 <td width="61%"></td>
 <td valign="bottom" width="5%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="5%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="5%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="5%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Number&#xA0;of</b><br />
 <b>Shares</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Weighted</b><br />
 <b>Average</b><br />
 <b>Exercise</b><br />
 <b>Price</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Weighted</b><br />
 <b>Average</b><br />
 <b>Contractual</b><br />
 <b>Term&#xA0;(Years)</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Aggregate</b><br />
 <b>Intrinsic</b><br />
 <b>Value</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Outstanding as of December&#xA0;31, 2018</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">797,931</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">8.29</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">8.42</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">6,486</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Assumed as part of Merger with Arsanis</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">271,230</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">
 &#xA0;&#xA0;&#xA0;&#xA0;62.60</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Granted</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">136,913</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">17.22</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Exercised</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(16,483</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">6.85</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Forfeited</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(22,378</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">8.43</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Outstanding as of March&#xA0;31, 2019</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,167,213</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">21.97</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">7.65</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">7,168</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Exercisable as of March&#xA0;31, 2019</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">556,774</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">30.13</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Vested and expected to vest as of March&#xA0;31, 2019</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">979,466</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">48.79</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The aggregate intrinsic value of options is calculated as the
 difference between the exercise price of the stock options and the
 fair value of the Company&#x2019;s common stock for those options
 that had exercise prices lower than the fair value of the
 Company&#x2019;s common stock. The aggregate intrinsic value of
 stock options exercised during the three months ended
 March&#xA0;31, 2019 was $123. The weighted average grant-date fair
 value per share of stock options granted during the three months
 ended March&#xA0;31, 2019 was $12.88.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Stock-Based Compensation</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Effective January&#xA0;1, 2019, the Company adopted
 ASU&#xA0;<font style="WHITE-SPACE: nowrap">2018-07</font>&#xA0;which
 required the Company to adjust compensation expense for the three
 months ended March&#xA0;31, 2019 for an immaterial amount for the
 unvested&#xA0;<font style="WHITE-SPACE: nowrap">non-employee</font>&#xA0;share
 options outstanding. The Company no longer remeasures the fair
 value of options granted to&#xA0;<font style="WHITE-SPACE: nowrap">non-employees</font>&#xA0;at
 each reporting period end (see Note&#xA0;2).</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 During the three months ended March&#xA0;31, 2019, the Company
 granted options to purchase 136,913 shares of common stock. As of
 March&#xA0;31, 2019, total unrecognized compensation expense
 related to unvested stock options award was $5,066, which is
 expected to be recognized over a weighted average period of
 2.5&#xA0;years.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Stock-based compensation expense was classified in the consolidated
 statements of operations and comprehensive loss as follows:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0">
 <tr>
 <td width="80%"></td>
 <td valign="bottom" width="8%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="8%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="6" align="center"><b>Three Months Ended<br />
 March&#xA0;31,</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;2019&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;2018&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Research and development expense</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">84</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">38</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 General and administrative expense</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">178</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">90</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Total stock-based compensation</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">262</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">128</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 &#xA0;</p>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6693110320">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>License, Collaboration, and Funding Agreements<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract', window );"><strong>Organization, Consolidation and Presentation of Financial Statements [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CollaborativeArrangementDisclosureTextBlock', window );">License, Collaboration, and Funding Agreements</a></td>
<td class="text"><div>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td valign="top" width="4%" align="left"><b>13.</b></td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left"><b>License, Collaboration, and Funding
 Agreements</b></p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 <b><i>Genzyme Agreement</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 In July&#xA0;2014, the Company entered into a license agreement
 (the &#x201C;Genzyme Agreement&#x201D;) with Genzyme pursuant to
 which the Company was granted an exclusive license to certain
 patents and intellectual property owned or controlled by Genzyme
 related to the CXCR4 receptor to develop and commercialize products
 containing licensed compounds (including but not limited to
 <font style="WHITE-SPACE: nowrap">X4P-001)</font> for all
 therapeutic, prophylactic and diagnostic uses, with the exception
 of autologous and allogenic human stem cell therapy. Under the
 terms of the Genzyme Agreement, the Company is obligated to use
 commercially reasonable efforts to develop and commercialize
 licensed products for use in the field in the United States and at
 least one other major market country. The Company has the right to
 grant sublicenses of the licensed rights that cover <font style="WHITE-SPACE: nowrap">X4P-001</font> to third parties.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 In exchange for these rights, in August 2014, the Company made an
 upfront payment of $50 to Genzyme. The Company accounted for the
 acquisition of technology as an asset acquisition because it did
 not meet the definition of a business. The Company recorded the
 upfront payment as research and development expense in the
 consolidated statement of operations and comprehensive loss because
 the acquired technology represented <font style="WHITE-SPACE: nowrap">in-process</font> research and development
 and had no alternative future use. In August&#xA0;2015, as a result
 of the closing of the Company&#x2019;s Series A preferred stock
 financing, the Company made an additional cash payment of $300 to
 Genzyme and issued to Genzyme 107,371 shares of its common stock,
 as adjusted for the 6 for 1 Reverse Stock Split and Exchange Ratio
 (see Note&#xA0;11), each as required by the Genzyme Agreement. The
 $300 payment and the $734 fair value of the 107,371 shares of
 common stock issued to Genzyme were recorded as research and
 development expense in the consolidated statements of operations
 and comprehensive loss for the year ended December&#xA0;31, 2015.
 Prior to the Merger with Arsanis, Genzyme has the right to require
 the Company to repurchase all, but not less than all, of these
 shares of common stock at any time during the term of the Genzyme
 Agreement for a price of $0.01 per share. Due to this redemption
 feature, the shares of common stock issued to Genzyme were
 classified outside of stockholders&#x2019; deficit on the
 consolidated balance sheets as of December&#xA0;31, 2018. On
 March&#xA0;13, 2019, the closing date of the Merger with Arsanis,
 these redeemable common shares were exchanged for common shares
 and, as a result, the fair value of the shares was reclassified to
 permanent equity.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Under the Genzyme Agreement, the Company is obligated to pay
 Genzyme milestone payments in the aggregate amount of up to
 $25,000, contingent upon the achievement by the Company of certain
 late-stage regulatory and sales milestones with respect to licensed
 products. In addition, the Company may be required to make a
 <font style="WHITE-SPACE: nowrap">one-time</font> milestone payment
 to Genzyme upon the consummation by the Company of a change of
 control transaction, in an amount equal to 5.5% of the
 consideration paid to equity holders of the Company, other than
 Genzyme, in connection with such change of control transaction,
 after deducting outstanding debt obligations of the Company and the
 aggregate cash investments made by equity holders into the Company
 prior to the closing of the change of control transaction. The
 Merger with Arsanis qualifies as a change of control transaction,
 as defined in the license agreement, but results in no payment
 being due to Genzyme under the license agreement.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company concluded that this contingent payment obligation meets
 the definition of a derivative instrument as the contingent payment
 obligation is not clearly and closely related to its host
 instrument and is a cash-settled liability (see Note&#xA0;2).
 Accordingly, the Company classifies this derivative as a liability
 within other liabilities <font style="WHITE-SPACE: nowrap">(non-current)</font> on its consolidated
 balance sheet (see Note&#xA0;2), and changes in the fair value of
 the derivative liability are recognized as a component of other
 income (expense), net in the consolidated statement of operations
 and comprehensive loss (see Note&#xA0;4). On March&#xA0;13, 2019,
 the closing date of the Merger with Arsanis, this derivative
 liability was remeasured to fair value, which was $0, and
 subsequent changes in fair value will no longer be recognized in
 the consolidated statements of operations and comprehensive loss
 because the contingent payment obligation expired at that time.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Under the Genzyme Agreement, the Company is obligated to pay
 Genzyme tiered royalties based on net sales of licensed products
 that the Company commercializes under the agreement. The obligation
 to pay royalties for each licensed product expires on a
 <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">country-by-country</font></font> basis on the
 latest of (i)&#xA0;the expiration of&#xA0;licensed patent rights
 that cover that licensed product in that country, (ii)&#xA0;the
 expiration of regulatory exclusivity in that country and
 (iii)&#xA0;ten years after the first commercial sale of such
 licensed product in that country. Royalty rates are subject to
 reduction under the agreement in specified circumstances, including
 in any country if the Company is required to obtain a license from
 any third party to the extent the Company&#x2019;s patent rights
 might infringe the third party&#x2019;s patent rights, if a licensed
 product is not covered by a valid claim in that country or if sales
 of generic products reach certain thresholds in that country. If
 the Company enters into a sublicense under the agreement, the
 Company will be obligated to pay Genzyme a percentage of certain
 upfront fees, maintenance fees, milestone payments and royalty
 payments paid to the Company by the sublicensee.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Under the Genzyme Agreement, the Company will itself manufacture
 and supply, or enter into manufacturing or supply agreements with
 Genzyme or third parties to manufacture and supply, clinical and
 commercial supplies of licensed compounds and each licensed
 product. During the three months ended March&#xA0;31, 2019 and
 2018, the Company did not enter into any third-party manufacturing
 or supply agreements in connection with the Genzyme Agreement. The
 Company is also responsible for all costs related to the filing,
 prosecution and maintenance of the licensed patent rights.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Genzyme Agreement will remain in effect until the expiration of
 the royalty term in all countries for all licensed
 products.&#xA0;The agreement may be terminated by either party with
 at least 90&#xA0;days&#x2019; notice in the event of material breach
 by the other party that remains uncured for 90 days, by either
 party for insolvency or bankruptcy of the other party, immediately
 by Genzyme if the Company challenges the licensed patents, or
 immediately by the Company if a material safety issue arises.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 During the three months ended March&#xA0;31, 2019 and 2018, the
 Company did not incur any payment obligations to Genzyme under the
 Genzyme Agreement.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Georgetown Agreement</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 In December 2016, the Company entered into a license agreement (the
 &#x201C;Georgetown Agreement&#x201D;) with Georgetown University
 (&#x201C;Georgetown&#x201D;) pursuant to which the Company obtained
 an exclusive, worldwide license to make, have made, use, sell,
 offer for sale and import of products covered by patent rights
 <font style="WHITE-SPACE: nowrap">co-owned</font> by Georgetown.
 The rights licensed to the Company are for all therapeutic,
 prophylactic and diagnostic uses in all disease indications in
 humans and animals.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Under the terms of the Georgetown Agreement, the Company paid a
 <font style="WHITE-SPACE: nowrap">one-time</font> only, upfront fee
 of $50 and the Company may be required to pay milestone payments of
 up to an aggregate of $800 related to commercial sales of a
 product. The Company accounted for the acquisition of technology as
 an asset acquisition because it did not meet the definition of a
 business. The Company recorded the upfront payment as research and
 development expense in the consolidated statement of operations and
 comprehensive loss because the acquired technology represented
 <font style="WHITE-SPACE: nowrap">in-process</font> research and
 development and had no alternative future use.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Under the Georgetown Agreement, the Company is solely responsible
 for all development and commercialization activities and costs in
 its respective territories. The Company is also responsible for all
 costs related to the filing, prosecution and maintenance of the
 licensed patent rights.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 12px">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt">
 The term of the Georgetown Agreement will continue until the
 expiration of the last valid claim within the patent rights
 covering the product. Georgetown may terminate the agreement in the
 event (i)&#xA0;the Company fails to pay any amount and fails to
 cure such failure within 30 days after receipt of notice,
 (ii)&#xA0;the Company defaults in its obligation to obtain and
 maintain insurance and fails to remedy such breach within
 45&#xA0;days after receipt of notice, or (iii)&#xA0;the Company
 declares insolvency or bankruptcy. The Company may terminate the
 agreement at any time upon at least 60&#xA0;days&#x2019; written
 notice.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 During the three months ended March&#xA0;31, 2019 and 2018, the
 Company did not incur any payment obligations to Georgetown under
 the Georgetown Agreement and no milestone payments were made or due
 under the Georgetown Agreement.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Beth Israel Deaconess Medical Center Agreement</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 In December 2016, the Company entered into a license agreement (the
 &#x201C;BIDMC Agreement&#x201D;) with Beth Israel Deaconess Medical
 Center (&#x201C;BIDMC&#x201D;), pursuant to which the Company
 obtained an exclusive, worldwide license to make, have made, use,
 sell, offer for sale and import of products covered by patent
 rights <font style="WHITE-SPACE: nowrap">co-owned</font> by BIDMC.
 The rights licensed to the Company are for all fields of use.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Under the terms of the BIDMC Agreement, the Company paid a
 <font style="WHITE-SPACE: nowrap">one-time</font> only, upfront fee
 of $20 and the Company is responsible for all future patent
 prosecution costs. The Company accounted for the acquisition of
 technology as an asset acquisition because it did not meet the
 definition of a business. The Company recorded the upfront payment
 as research and development expense in the consolidated statement
 of operations and comprehensive loss because the acquired
 technology represented <font style="WHITE-SPACE: nowrap">in-process</font> research and development
 and had no alternative future use.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The term of the BIDMC Agreement will continue until the expiration
 of the last valid claim within the patent rights covering the
 licensed products. BIDMC may terminate the agreement in the event
 (i)&#xA0;the Company fails to pay any amount and fails to cure such
 failure within 15 days after receipt of notice, (ii)&#xA0;the
 Company is in material breach of any material provision of the
 agreement and fails to remedy such breach within 60 days after
 receipt of notice, or (iii)&#xA0;the Company declares insolvency or
 bankruptcy. We may terminate the agreement at any time upon at
 least 90 days&#x2019; written notice.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company did not incur any payment obligations under the BIDMC
 Agreement during the months ended March&#xA0;31, 2019 and 2018.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Adimab Option and License Agreement</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 In February 2017, Arsanis entered into an option and license
 agreement with Adimab, a related party (the &#x201C;Adimab Option
 Agreement&#x201D;). Under the Adimab Option Agreement, Adimab has
 provided to Arsanis certain proprietary antibodies against
 respiratory syncytial virus (&#x201C;RSV antibodies&#x201D;) for its
 evaluation during a specified option period and has granted Arsanis
 an exclusive, <font style="WHITE-SPACE: nowrap">non-sublicensable</font> license in a
 specified field under certain Adimab patent rights and <font style="WHITE-SPACE: nowrap">know-how</font> during the option period.
 Under the Adimab Option Agreement, the Company has an exclusive
 option, exercisable during the option period upon payment of an
 option fee to Adimab, to require Adimab to assign to the Company
 all rights in up to a specified number of RSV antibodies selected
 by the Company and certain patent rights owned by Adimab that cover
 these antibodies, and to obtain from Adimab a <font style="WHITE-SPACE: nowrap">non-exclusive</font> license in a specified
 field, with the right to grant sublicenses, under certain other
 patent rights and <font style="WHITE-SPACE: nowrap">know-how</font>
 owned by Adimab.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 If the Company exercises its option under the Adimab Option
 Agreement, the Company is required to use commercially reasonable
 efforts to develop and commercialize at least one product based on
 a licensed RSV antibody in major markets and is obligated to pay
 Adimab an option fee of $0.3&#xA0;million and make future milestone
 payments upon the achievement of specified clinical and regulatory
 milestones in the aggregate amount of up to $24.4&#xA0;million. The
 Company is obligated to pay Adimab royalties at a mid single-digit
 percentage of net sales of products based on the initial RSV
 antibodies (including modified or derivative forms of those
 antibodies created by or for the Company) by the Company or any of
 its affiliates, licensees or sublicensees, regardless of whether
 these products practice any of the assigned or licensed patents or
 <font style="WHITE-SPACE: nowrap">know-how.</font> If the Company
 materially breaches these diligence obligations, Adimab will have
 the right to terminate the Adimab Option Agreement.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company has no payment obligations under the Adimab Option
 Agreement with respect to sales of products based on licensed RSV
 antibodies to the extent they are sold at cost in developing
 countries under the February 2017 Gates Foundation grant agreement,
 as amended and restated in August 2018, and the August 2018 Gates
 Foundation grant agreement (which are described in further detail
 below). However, if such products are sold in developing countries
 for an amount that exceeds cost, then the amount of such excess
 will be subject to the royalty payment obligations described in the
 preceding paragraph.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 12px">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt">
 If the Company does not exercise its option, the Adimab Option
 Agreement will expire on the Company&#x2019;s achievement of
 specified preclinical milestones under the grant agreements with
 the Gates Foundation, but in any event no later than <font style="WHITE-SPACE: nowrap">mid-2019.</font> If the Company does exercise
 its option, the Adimab Option Agreement will expire on the
 <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">last-to-expire</font></font> royalty term
 (defined, on a <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">product-by-product</font></font> and
 <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">country-by-country</font></font> basis, as
 the period ending on the later of twelve years after the first
 commercial sale of such product in such country and the expiration
 of the last of a specified set of patents and patent applications
 covering such product in such country) for any and all products for
 which the Company is obligated to pay Adimab royalties under the
 Adimab Option Agreement. The Company has the right to terminate the
 Adimab Option Agreement for any reason by providing Adimab with a
 specified amount of prior written notice. Adimab has the right to
 terminate the Adimab Option Agreement if the Company materially
 breaches the agreement and fails to cure such breach within a
 specified cure period, including for the Company&#x2019;s failure to
 use commercially reasonable efforts to develop and commercialize at
 least one product based on a licensed RSV antibody in major
 markets. If Adimab terminates the Adimab Option Agreement for the
 Company&#x2019;s breach, if the Company terminates the agreement for
 convenience or if the agreement expires before the Company
 exercises its option, then the Company must return or destroy
 certain <font style="WHITE-SPACE: nowrap">know-how,</font>
 including all initial RSV antibodies, and all modified or
 derivative forms of those antibodies, in its possession other than
 those for which the Company has made all payments required under
 the Adimab Option Agreement, assign certain patents covering
 certain RSV antibodies to Adimab, grant Adimab a <font style="WHITE-SPACE: nowrap">non-exclusive,</font> royalty-free license
 under certain other patents, and grant Adimab a time-limited right
 of first negotiation to obtain an exclusive license to certain
 patents and <font style="WHITE-SPACE: nowrap">know-how</font> and
 the transfer and assignment of certain regulatory filings and
 approvals and other related assets related to products based on
 licensed RSV antibodies. Certain of the Company&#x2019;s payment
 obligations relating to specified products and patents arising from
 the agreement survive expiration or termination of the
 agreement.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 During the three months ended March&#xA0;31, 2019, the Company
 recognized no research and development expense in connection with
 the Adimab Option Agreement.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Adimab Collaboration Agreement</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 In May 2011, Arsanis entered into a collaboration agreement with
 Adimab, LLC (&#x201C;Adimab&#x201D;) and together with certain
 applicable option exercise letters the Company has sent to Adimab,
 the &#x201C;Adimab Collaboration Agreement&#x201D;). Under the Adimab
 Collaboration Agreement, the Company and Adimab were required to
 use reasonable efforts to conduct certain research, which was
 funded by the Company, to discover and optimize antibodies directed
 against targets selected by the Company. With respect to each
 target that was the subject of the research, the Company had an
 exclusive option to obtain, with respect to a specified number of
 antibodies directed against such target and discovered or optimized
 by Adimab, (i)&#xA0;ownership of certain patent rights relating to
 such antibodies and (ii)&#xA0;exclusive and <font style="WHITE-SPACE: nowrap">non-exclusive</font> licenses in a specified
 field, with the right to grant sublicenses, under certain patent
 rights and <font style="WHITE-SPACE: nowrap">know-how.</font></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Under the Adimab Collaboration Agreement, for each target for which
 the Company has exercised an option, the Company is required to use
 commercially reasonable efforts to develop and commercialize at
 least one product in major markets. If the Company does not fulfill
 these diligence obligations, Adimab may consider it a material
 breach, allowing Adimab to terminate the Adimab Collaboration
 Agreement with respect to such target and all associated
 products.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company is obligated to pay Adimab royalties at a mid
 single-digit percentage of net sales made by the Company or its
 affiliates of products based on antibodies for which the Company
 exercised its option, or products that use or are based on any
 antibody discovered or optimized under the agreement, any
 derivative or modified version of any such antibody, or any
 sequence information as to any such antibody. In addition, if the
 Company sells or licenses to any third party, or otherwise grants
 rights to any third party to, any of the products for which the
 Company is obligated to pay Adimab royalties, either alone or as
 part of a package including specified patents not directed to these
 antibodies, the Company is obligated to pay Adimab either
 (i)&#xA0;the same royalties on net sales of such products by such
 third party or (ii)&#xA0;a percentage, ranging from the low double
 digits to a maximum of less than 30%, of the payments the Company
 receives from such third parties that are attributable to such
 grant of rights. In April 2017, the Company entered into a letter
 agreement with the Gates Foundation, pursuant to which the Company
 licensed to the Gates Foundation certain rights under its
 ASN100&#xA0;program. The Company has no payment obligations under
 the Adimab Collaboration Agreement with respect to sales of certain
 antibody products if they are sold at cost in developing countries
 under its letter agreement with the Gates Foundation. However, if
 such products are sold in developing countries for an amount that
 exceeds cost, then the amount of such excess over cost will be
 subject to the royalty payment obligations described above.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 If the Company (or one of its affiliates with rights under the
 agreement) undergoes a change in control and, at the time of such
 change in control, the Company has not sold or licensed to third
 parties all of its rights in antibodies for which the Company is
 obligated to pay Adimab royalties under the agreement, then the
 Company is obligated to either (i)&#xA0;pay Adimab a percentage, in
 the mid double digits, of the payments it receives from that change
 in control that are reasonably attributable to those rights and
 certain patents arising from the collaboration or (ii)&#xA0;require
 the Company&#x2019;s acquirer and all of its future third-party
 collaborators to pay to Adimab the royalties at a mid single-digit
 percentage of net sales based on those rights. If the Company
 grants rights to a third party under certain patents that are not
 directed to the antibodies for which the Company is obligated to
 pay Adimab royalties (as described above), the Company is also
 obligated to pay Adimab, in place of royalties or a percentage of
 payments received from the third party, a lump sum in the high six
 digits.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Adimab Collaboration Agreement will expire on a <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">country-by-country</font></font> basis twelve
 years after the first commercial sale in such country of the last
 product for which the Company is obligated to pay Adimab royalties
 in such country under the Adimab Collaboration Agreement. The
 Company has the right to terminate the Adimab Collaboration
 Agreement for any reason by providing Adimab with a specified
 amount of prior written notice. Adimab has the right to terminate
 the Adimab Collaboration Agreement if the Company materially
 breaches the agreement and fails to cure such breach within a
 specified cure period, including for its failure to use
 commercially reasonable efforts to develop and commercialize at
 least one product directed at a target for which the Company has
 exercised an option in major markets. If Adimab terminates the
 Adimab Collaboration Agreement for the Company&#x2019;s breach, or
 if the Company terminates the agreement for convenience, then the
 Company must transfer or license to Adimab certain rights and
 assets relating to targets and antibodies for which the Company has
 exercised its option. Adimab is then obligated to make payments to
 the Company with respect to these targets and antibodies that are
 similar to the payments the Company is required to make to Adimab
 during the term of the agreement. Certain of the Company&#x2019;s
 payment obligations relating to specified products and patents
 arising from the agreement survive expiration or termination of the
 agreement.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 During the three months ended March&#xA0;31, 2019, the Company did
 not recognize any research and development under the Adimab
 Collaboration Agreement.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Gates Foundation Grant Agreements</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 In February 2017, Arsanis entered into a grant agreement with the
 Gates Foundation (&#x201C;Grant Agreement&#x201D;), under which the
 Gates Foundation agreed to provide the Company up to approximately
 $9,300 to conduct preclinical development of monoclonal antibodies
 for the prevention of RSV infection in newborns (the &#x201C;RSV
 project&#x201D;).</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 In connection with this Grant Agreement, the Company has granted to
 the Gates Foundation a <font style="WHITE-SPACE: nowrap">non-exclusive,</font> perpetual,
 royalty-free, fully paid up, sublicensable license to make, use,
 sell, offer to sell, import, distribute, copy, modify, create
 derivative works, publicly perform and display the funded
 developments and, to the extent incorporated into a funded
 development or required to use a funded development, any other
 technology created outside of the RSV project that was used as part
 of the RSV project, for the benefit of people in developing
 countries. This license survives any expiration or termination of
 the grant agreement. The Grant Agreement expires on
 October&#xA0;31, 2019. The Gates Foundation can modify, suspend or
 discontinue any payment under the grant agreement, or terminate the
 grant agreement, if it is not reasonably satisfied with the
 Company&#x2019;s progress on the RSV project; if there are
 significant changes to the Company&#x2019;s leadership or other
 factors that the Gates Foundation reasonably believes may threaten
 the RSV project&#x2019;s success; if the Company undergoes a change
 in control; if there is a change in the Company&#x2019;s tax status;
 if the RSV project is no longer aligned with the Gates
 Foundation&#x2019;s programmatic strategy; or if the Company fails
 to comply with the grant agreement. Any grant funds that have not
 been used for, or committed to, the RSV project upon the expiration
 or termination of the grant agreement must be returned to the Gates
 Foundation or otherwise used as directed by the Gates Foundation.
 In August 2018, Arsanis entered into an amended and restated grant
 agreement which replaced the February 2017 grant agreement in its
 entirety. The amended and restated grant agreement includes
 amendments to conform to current Gates Foundation audit, reporting,
 and other administrative requirements, as well as to make the
 perpetual Gates Foundation license grant described below
 irrevocable.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 During the three months ended March&#xA0;31, 2019, the Company did
 not incur qualifying expenses under the letter agreement with the
 Gates Foundation.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Research and Development Incentive Program</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company participates in a research and development incentive
 program provided by the Austrian government whereby the Company is
 entitled to reimbursement by the Austrian government for a
 percentage of qualifying research and development expenses incurred
 by the Company&#x2019;s subsidiary in Austria. Under the program,
 the reimbursement rate for qualifying research and development
 expenses incurred by the Company through its subsidiary in Austria
 is 14% for the current year .</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company recognizes incentive income from Austrian research and
 development incentives when qualifying expenses have been incurred,
 there is reasonable assurance that the payment will be received,
 and the consideration can be reliably measured. Management has
 assessed the Company&#x2019;s research and development activities
 and expenditures to determine which activities and expenditures are
 likely to be eligible under the research and development incentive
 program described above. At each reporting date, management
 estimates the reimbursable incentive income available to the
 Company based on available information at the time.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 12px">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt">
 As of March&#xA0;31, 2019, the Company recorded receivables for
 amounts due under the program of $1.6&#xA0;million, which amounts
 were included in grant and incentive receivables in the
 consolidated balance sheet.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Janssen License and Option Agreement</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 On December&#xA0;12, 2018, Arsanis entered into a patent license
 and option agreement with Janssen Pharmaceuticals, Inc.
 (&#x201C;Janssen&#x201D;), (the &#x201C;Janssen License and Option
 Agreement&#x201D;). Pursuant to the Janssen License and Option
 Agreement, Arsanis granted to Janssen (i)&#xA0;a <font style="WHITE-SPACE: nowrap">non-exclusive</font> license to specified
 patents in Arsanis&#x2019;s portfolio related to the ASN200 E. coli
 program, and (ii)&#xA0;an option for Janssen to acquire these
 patents in the future if specified conditions are met. Janssen
 agreed to pay Arsanis $3.5&#xA0;million within 15 business days
 after the December&#xA0;12, 2018 effective date of the Janssen
 License and Option Agreement, in addition to a future
 $0.5&#xA0;million payment in the event Janssen exercises its option
 to acquire the relevant patents. Arsanis received the
 $3.5&#xA0;million payment from Janssen in December 2018 and
 recognized this amount as revenue. Such revenue is not reflected in
 the consolidated financial statements of the Company as it occurred
 prior to the Merger. Janssen&#x2019;s option to the relevant patents
 will be recognized as revenue in full in the period in which the
 option exercise occurs.</p>


 </div><span></span>
</td>
</tr>
</table>
<div style="display: none;">
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The entire disclosure for collaborative arrangements in which the entity is a participant, including a) information about the nature and purpose of such arrangements; b) its rights and obligations thereunder; c) the accounting policy for collaborative arrangements; and d) the income statement classification and amounts attributable to transactions arising from the collaborative arrangement between participants.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 808<br> -URI http://asc.fasb.org/topic&amp;trid=5833765<br></p></div>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6769543104">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Income Taxes<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_IncomeTaxDisclosureAbstract', window );"><strong>Income Tax Disclosure [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_IncomeTaxDisclosureTextBlock', window );">Income Taxes</a></td>
<td class="text"><div>
 <table style="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" border="0" cellpadding="0" cellspacing="0" width="100%">
 <tr style="page-break-inside:avoid">
 <td width="4%" valign="top" align="left"><b>14.</b></td>
 <td align="left" valign="top">
 <p style="margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman;" align="left"><b>Income Taxes</b></p>
 </td>
 </tr>
 </table>
 <p style="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">
 The Company did not record a federal or state income tax benefit
 for its losses for the three months ended March&#xA0;31, 2019 and
 2018 due to the conclusion that a full valuation allowance is
 required against the Company&#x2019;s deferred tax assets.</p>
 </div><span></span>
</td>
</tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 740<br> -URI http://asc.fasb.org/topic&amp;trid=2144680<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6661120464">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Net Loss per Share<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_EarningsPerShareAbstract', window );"><strong>Earnings Per Share [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_EarningsPerShareTextBlock', window );">Net Loss per Share</a></td>
<td class="text"><div>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="break-inside: avoid">
 <td valign="top" width="4%" align="left"><b>15.</b></td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left"><b>Net Loss per Share</b></p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Basic and diluted net loss per share attributable to common
 stockholders was calculated as follow:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0">
 <tr>
 <td width="75%"></td>
 <td valign="bottom" width="6%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="6%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="6" align="center"><b>Three Months Ended<br />
 March&#xA0;31,</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;2019&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;2018&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Numerator:</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 5em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Net loss</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">(10,873</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">(7,367</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 5em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Accruing dividends on Series A convertible preferred stock</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(592</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(740</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 5em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Net loss attributable to common stockholders</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">(11,465</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">(8,107</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Denominator:</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Weighted average common shares outstanding&#x2014;basic and
 diluted</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,717,808</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">457,971</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Net loss per share attributable to common stockholders&#x2014;basic
 and diluted</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">(6.67</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">(17.70</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The Company has included 107,371 shares of redeemable common stock
 in its computation of basic and diluted weighted average common
 shares outstanding for the three months ended March&#xA0;31, 2019
 and 2018 as this class of stock participates in losses similarly to
 other common stockholders.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The Company&#x2019;s potentially dilutive securities included
 outstanding stock options, convertible preferred stock, and
 warrants to purchase shares of convertible preferred stock for the
 three month period ended March&#xA0;31, 2018 and included
 outstanding stock options and warrants to purchase common stock for
 the three month period ended March&#xA0;31, 2019. These potentially
 dilutive securities have been excluded from the computation of
 diluted net loss per share as the effect would be to reduce the net
 loss per share, and thus they are considered
 &#x201C;anti-dilutive.&#x201D; Therefore, the weighted average number
 of common shares outstanding used to calculate both basic and
 diluted net loss per share attributable to common stockholders is
 the same. The Company excluded the following potential common
 shares, presented based on amounts outstanding at each period end
 and adjusted for the Exchange Ratio and Reverse Stock Split, from
 the computation of diluted net loss per share attributable to
 common stockholders for the periods indicated because including
 them would have had an anti-dilutive effect:</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="76%" align="center" border="0">
 <tr>
 <td width="76%"></td>
 <td valign="bottom" width="3%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="3%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="6" align="center"><b>Three Months Ended<br />
 March&#xA0;31,</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;2019&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;2018&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Options to purchase common stock</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,037,089</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">538,429</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Convertible preferred stock (as converted to common stock)</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">3,556,147</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Warrants to purchase common stock (presented on
 an&#xA0;<font style="WHITE-SPACE: nowrap">as-converted,</font>&#xA0;as
 exchanged, split-adjusted basis.</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">493,927</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">423,416</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,531,016</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">4,517,992</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 18pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 </div><span></span>
</td>
</tr>
</table>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The entire disclosure for earnings per share.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 260<br> -URI http://asc.fasb.org/topic&amp;trid=2144383<br></p></div>
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<tr>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6612886624">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Subsequent Events<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SubsequentEventsAbstract', window );"><strong>Subsequent Events [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SubsequentEventsTextBlock', window );">Subsequent Events</a></td>
<td class="text"><div>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="break-inside: avoid">
 <td valign="top" width="4%" align="left"><b>16.</b></td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left"><b>Subsequent Events</b></p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 On April&#xA0;12, 2019, the Company entered into an underwriting
 agreement with Cowen and Company, LLC and Stifel,
 Nicolaus&#xA0;&amp; Company, Incorporated, as representatives of
 the several underwriters named therein pursuant to which it sold
 5,670,000 shares of common stock and, in lieu of common
 stock,&#xA0;<font style="WHITE-SPACE: nowrap">pre-funded</font>&#xA0;warrants
 to purchase 2,130,000 shares of common stock, and accompanying
 Class&#xA0;A warrants to purchase 3,900,000 shares of its common
 stock, at a price to the public of $11.00 per share and
 accompanying Class&#xA0;A warrants (or $10.999
 per&#xA0;<font style="WHITE-SPACE: nowrap">pre-funded</font>&#xA0;warrant
 and accompanying Class&#xA0;A&#xA0;warrants).&#xA0;The Class&#xA0;A
 warrants have an exercise price of $13.20, will expire five years
 from the date of issuance, and are immediately exercisable with
 certain restrictions. The gross proceeds from the offering were
 $85.8&#xA0;million before deducting underwriting discounts and
 estimated offering expenses. The offering closed on April&#xA0;16,
 2019.</p>
 </div><span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_SubsequentEventsAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_SubsequentEventsAbstract</td>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The entire disclosure for significant events or transactions that occurred after the balance sheet date through the date the financial statements were issued or the date the financial statements were available to be issued. Examples include: the sale of a capital stock issue, purchase of a business, settlement of litigation, catastrophic loss, significant foreign exchange rate changes, loans to insiders or affiliates, and transactions not in the ordinary course of business.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 855<br> -URI http://asc.fasb.org/topic&amp;trid=2122774<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_SubsequentEventsTextBlock</td>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6836634128">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Summary of Significant Accounting Policies (Policies)<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AccountingPoliciesAbstract', window );"><strong>Accounting Policies [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BasisOfAccountingPolicyPolicyTextBlock', window );">Unaudited Interim Financial Statements</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Unaudited Interim Financial Statements</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The condensed balance sheet at December&#xA0;31, 2018 was derived
 from audited financial statements but does not include all
 disclosures required by GAAP. The accompanying condensed
 consolidated financial statements are unaudited. The accompanying
 unaudited interim consolidated financial statements have been
 prepared by the Company pursuant to the rules and regulations of
 the Securities and Exchange Commission (the &#x201C;SEC&#x201D;) for
 interim financial statements. Accordingly, certain information and
 footnote disclosures normally included in financial statements
 prepared in accordance with GAAP have been condensed or omitted
 pursuant to such rules and regulations. However, the Company
 believes that the disclosures are adequate to make the information
 presented not misleading. These unaudited condensed financial
 statements should be read in conjunction with the
 Company&#x2019;s&#xA0;audited financial statements and the notes
 thereto for the year ended December&#xA0;31, 2018. In the opinion
 of management, all adjustments, consisting only of normal recurring
 adjustments as necessary, for the fair statement of the
 Company&#x2019;s condensed financial position, condensed results of
 its operations and cash flows have been made. The results of
 operations for the three months ended March&#xA0;31, 2019 are not
 necessarily indicative of the results of operations that may be
 expected for the year ending December&#xA0;31, 2019.</p>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_UseOfEstimates', window );">Use of Estimates</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Use of Estimates</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The preparation of the Company&#x2019;s condensed consolidated
 financial statements in conformity with GAAP requires management to
 make estimates and assumptions that affect the reported amounts of
 assets and liabilities, the disclosure of contingent assets and
 liabilities at the date of the consolidated financial statements,
 and the reported amounts of expenses during the reporting period.
 Significant estimates and assumptions reflected in these
 consolidated financial statements include, but are not limited to,
 the accrual of research and development expenses, the valuation of
 intangible assets acquired in business combinations, the valuations
 of common stock prior to the Merger, the valuation of stock
 options, preferred stock warrants (and the resulting preferred
 stock warrant liability), derivative instruments (and the resulting
 derivative liability), and the preferred stock repurchase
 liability, and valuation of lease liabilities. The Company bases
 its estimates on historical experience, known trends and other
 market-specific or other relevant factors that it believes to be
 reasonable under the circumstances. On an ongoing basis, management
 evaluates its estimates when there are changes in circumstances,
 facts and experience. Changes in estimates are recorded in the
 period in which they become known. Actual results could differ from
 those estimates.</p>
 </div><span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ConsolidationPolicyTextBlock', window );">Principles of Consolidation</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Principles of Consolidation</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The condensed consolidated financial statements include the
 accounts of the Company and its wholly owned subsidiaries,
 including Arsanis Biosciences GmbH, which is incorporated in
 Vienna, Austria (&#x201C;Arsanis GmbH&#x201D;), and X4 Therapeutics,
 Inc. All significant intercompany accounts and transactions have
 been eliminated.</p>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock', window );">Foreign Currency and Currency Translation</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Foreign Currency and Currency Translation</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Management has determined that the functional currency for the
 Company&#x2019;s wholly owned foreign subsidiary, Arsanis
 Biosciences GmbH, is the Euro. Management&#x2019;s assessment
 considered the currency environment in which the entity operates,
 including inflows of cash from research and development incentive
 programs and outflows of cash for operating expenditure.
 Accordingly, the assets and liabilities of Arsanis Biosciences GmbH
 are translated from the Euro into United States dollars at the
 exchange rate in effect on the balance sheet date and income and
 expenses are translated at the average exchange rate in effect
 during the period. Unrealized translation gains and losses are
 recorded as a cumulative translation adjustment, which is included
 in the consolidated balance sheet as a component of accumulated
 other comprehensive income (loss). Adjustments that arise from
 exchange rate changes on transactions denominated in a currency
 other than the Euro are included in other income (expense), net in
 the consolidated statements of operations as incurred.</p>
 </div><span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ConcentrationOfCreditRiskPolicyTextBlock', window );">Concentrations of Credit Risk and Significant Suppliers</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Concentrations of Credit Risk and Significant
 Suppliers</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Financial instruments that potentially subject the Company to
 concentrations of credit risk consist principally of cash and cash
 equivalents and research and development incentive receivables. The
 Company generally maintains cash balances in various operating
 accounts at financial institutions that management believes to be
 of high credit quality, in amounts that may exceed federally
 insured limits. The Company has not experienced any losses related
 to its cash and cash equivalents.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The Company is dependent on third-party manufacturers to supply
 products for research and development activities in its programs.
 The Company relies and expects to continue to rely on a small
 number of manufacturers to supply it with its requirements for the
 active pharmaceutical ingredients and formulated drugs related to
 these programs. These programs could be adversely affected by a
 significant interruption in these manufacturing services or in the
 supply of active pharmaceutical ingredients and formulated
 drugs.</p>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CashAndCashEquivalentsPolicyTextBlock', window );">Cash and Cash Equivalents</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Cash and Cash Equivalents</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company considers all highly liquid investments with maturities
 of three months or less at the date of purchase to be cash
 equivalents. Cash equivalents consisted of money market funds as of
 March&#xA0;31, 2019 and December&#xA0;31, 2018.</p>
 </div><span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CashAndCashEquivalentsRestrictedCashAndCashEquivalentsPolicy', window );">Restricted Cash</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Restricted Cash</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 In connection with the Company&#x2019;s lease agreement entered into
 January 2017 for its facility in Cambridge, Massachusetts, the
 Company maintains a letter of credit of $264 for the benefit of the
 landlord. As of March&#xA0;31, 2019 and December&#xA0;31, 2018, the
 underlying cash balance securing this letter of credit was
 classified as restricted cash <font style="WHITE-SPACE: nowrap">(non-current)</font> on its condensed
 consolidated balance sheets.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company also maintains letters of credit for the benefit of the
 landlords in connection with the Company&#x2019;s office,
 laboratory, parking and storage space leases in Waltham, MA and
 Vienna, Austria and another letter of credit in connection with
 Company&#x2019;s corporate credit cards. As of March&#xA0;31, 2019,
 long term restricted cash consisted of letters of credit related to
 the Company&#x2019;s leases of office, laboratory, parking and
 storage space lease in Vienna, Austria, of $283 and leased office
 space acquired from Arsanis located in Waltham, MA, which expires
 on December&#xA0;31, 2023, of approximately $250.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 As of March&#xA0;31, 2019, the Company was also required to
 maintain a separate cash balance of $150 to collateralize corporate
 credit cards with a bank, which was classified as restricted cash
 <font style="WHITE-SPACE: nowrap">(non-current)</font> on its
 consolidated balance sheets.</p>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentPolicyTextBlock', window );">Property and Equipment</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Property and Equipment</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Property and equipment are stated at cost less accumulated
 depreciation and amortization. Depreciation and amortization
 expense is recognized using the straight-line method over the
 estimated useful life of each asset, as follows:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="68%" align="center" border="0">
 <tr>
 <td width="62%"></td>
 <td valign="bottom" width="4%"></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" align="center"><b>Estimated&#xA0;Useful&#xA0;Life</b></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Office furniture</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" align="center">3 years</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Computer equipment</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" align="center">3 years</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Software</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" align="center">3 years</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Laboratory equipment</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" align="center">3 to 10 years</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Leasehold improvements</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" align="center">
 Shorter&#xA0;of&#xA0;lease&#xA0;term&#xA0;or&#xA0;10&#xA0;years</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Estimated useful lives are periodically assessed to determine if
 changes are appropriate. Maintenance and repairs are charged to
 expense as incurred. When assets are retired or otherwise disposed
 of, the cost of these assets and related accumulated depreciation
 or amortization are eliminated from the consolidated balance sheet
 and any resulting gains or losses are included in the consolidated
 statements of operations and comprehensive loss in the period of
 disposal. Costs for capital assets not yet placed into service are
 capitalized as <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">construction-in-progress</font></font> and
 depreciated once placed into service.</p>
 </div><span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_RightOfUseAssetAndLeaseLiabilityPolicyTextBlock', window );">Right-of-Use Assets and Leases</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i><font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">Right-of-Use</font></font>&#xA0;Assets
 and Leases</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Effective January&#xA0;1, 2019, the Company adopted Accounting
 Standards Codification (&#x201C;ASC&#x201D;), Topic
 842,&#xA0;<i>Leases&#xA0;</i>(&#x201C;ASC
 842&#x201D;), using the modified retrospective approach through a
 cumulative-effect adjustment and utilizing the effective date as
 its date of initial application, with prior periods unchanged and
 presented in accordance with the guidance in Topic
 840,&#xA0;<i>Leases</i>&#xA0;(&#x201C;ASC
 840&#x201D;).</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 At the inception of an arrangement, the Company determines whether
 the arrangement is or contains a lease based on the unique facts
 and circumstances present. Leases with
 a&#xA0;<font style="WHITE-SPACE: nowrap">non-cancellable</font>&#xA0;term
 greater than one year are recognized on the balance sheet
 as&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font>&#xA0;assets,
 lease liabilities and long-term lease liabilities. The Company has
 elected not to recognize on the balance sheet leases with terms of
 one year or less. Options to renew a lease are not included in the
 Company&#x2019;s initial lease term assessment unless there is
 reasonable certainty that the Company will renew.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Operating lease liabilities and their
 corresponding&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font>&#xA0;assets
 are recorded based on the present value of lease payments over the
 expected remaining lease term. However, certain adjustments to
 the&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font>&#xA0;operating
 asset may be required for items, such as incentives received. The
 interest rate implicit in lease contracts is typically not readily
 determinable. As a result, the Company utilizes its incremental
 borrowing rates, which are the rates it incurs to borrow on a
 collateralized basis over a similar term an amount equal to the
 lease payments in a similar economic environment.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In accordance with the guidance in ASC 842, components of a lease
 are split into lease components and&#xA0;<font style="WHITE-SPACE: nowrap">non-lease</font>&#xA0;components.
 A policy election is available pursuant to which an entity may
 elect to not separate lease and&#xA0;<font style="WHITE-SPACE: nowrap">non-lease</font>components. Rather, each
 lease component and the related&#xA0;<font style="WHITE-SPACE: nowrap">non-lease</font>&#xA0;components
 would be accounted for together as a single component. For new and
 amended leases beginning in 2019 and after, the Company has elected
 to account for the lease and&#xA0;<font style="WHITE-SPACE: nowrap">non-lease</font>&#xA0;components
 as a combined lease component for its office and laboratory
 building leases.</p>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ImpairmentOrDisposalOfLongLivedAssetsPolicyTextBlock', window );">Impairment of Long-Lived Assets</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Impairment of Long-Lived Assets</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Long-lived assets consist of property and equipment. Long-lived
 assets to be held and used are tested for recoverability whenever
 events or changes in business circumstances indicate that the
 carrying amount of the assets may not be fully recoverable. Factors
 that the Company considers in deciding when to perform an
 impairment review include significant underperformance of the
 business in relation to expectations, significant negative industry
 or economic trends and significant changes or planned changes in
 the use of the assets. If an impairment review is performed to
 evaluate a long-lived asset group for recoverability, the Company
 compares forecasts of undiscounted cash flows expected to result
 from the use and eventual disposition of the long-lived asset group
 to its carrying value. An impairment loss would be recognized in
 loss from operations when estimated undiscounted future cash flows
 expected to result from the use of an asset group are less than its
 carrying amount. The impairment loss would be based on the excess
 of the carrying value of the impaired asset group over its fair
 value. To date, the Company has not recorded any impairment losses
 on long-lived assets.</p>
 </div><span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_GoodwillAndIntangibleAssetsGoodwillPolicy', window );">Goodwill</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Goodwill</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Business combinations are accounted for under the acquisition
 method. The total purchase price of an acquisition is allocated to
 the underlying identifiable net assets, based on their respective
 estimated fair values as of the acquisition date. Determining the
 fair value of assets acquired and liabilities assumed requires
 management&#x2019;s judgment and often involves the use of
 significant estimates and assumptions, including assumptions with
 respect to future cash inflows and outflows, probabilities of
 success, discount rates, and asset lives, among other items. Assets
 acquired and liabilities assumed are recorded at their estimated
 fair values. The excess of the purchase price over the estimated
 fair values of the net assets acquired is recorded as goodwill.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Goodwill is tested for impairment at the reporting unit level
 annually in the fourth quarter, or more frequently when events or
 changes in circumstances indicate that the asset might be impaired.
 Examples of such events or circumstances include, but are not
 limited to, a significant adverse change in legal or business
 climate, an adverse regulatory action or unanticipated competition.
 The Company has determined that it operates in a single operating
 segment and has a single reporting unit.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company assesses qualitative factors to determine whether the
 existence of events or circumstances would indicate that it is more
 likely than not that the fair value of the reporting unit was less
 than its carrying amount. If after assessing the totality of events
 or circumstances, the Company were to determine that it is more
 likely than not that the fair value of the reporting unit is less
 than its carrying amount, then the Company would perform a
 quantitative impairment test.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company compares the fair value of the reporting unit to its
 carrying value. If the fair value of the reporting unit exceeds the
 carrying value of the net assets, goodwill is not impaired, and no
 further testing is required. If the fair value of the reporting
 unit is less than the carrying value, the Company measures the
 amount of impairment loss, if any, as the excess of the carrying
 value over the fair value of the reporting unit. The Company has
 determined there were no indicators of goodwill impairment as of
 March&#xA0;31, 2019.</p>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_IntangibleAssetsPolicyTextBlock', window );">Intangible Assets</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt">
 <b><i>Intangible Assets</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company acquired certain <font style="WHITE-SPACE: nowrap">in-process</font> research and development
 assets (&#x201C;IPR&amp;D&#x201D;), which are classified as
 indefinite-lived intangible assets. Acquired IPR&amp;D represents
 the fair value assigned to research and development assets that the
 Company acquires and have not been completed at the acquisition
 date. The fair value of IPR&amp;D acquired in a business
 combination is capitalized on the Company&#x2019;s consolidated
 balance sheets at the acquisition-date fair value and is determined
 by estimating the costs to develop the technology into commercially
 viable products, estimating the resulting revenue from the
 projects, and discounting the projected net cash flows to present
 value. IPR&amp;D is not amortized, but rather is reviewed for
 impairment on an annual basis or more frequently if indicators of
 impairment are present, until the project is completed or
 abandoned. If the Company determines that IPR&amp;D becomes
 impaired or is abandoned, the carrying value is written down to its
 fair value with the related impairment charge recognized in the
 Company&#x2019;s consolidated statement of operations in the period
 in which the impairment occurs. Upon successful completion of each
 project and launch of the product, the Company will make a separate
 determination of the estimated useful life of the IPR&amp;D
 intangible asset and the related amortization will be recorded as
 an expense prospectively over its estimated useful life.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The projected discounted cash flow models used to estimate the
 Company&#x2019;s IPR&amp;D reflect significant assumptions regarding
 the estimates a market participant would make in order to evaluate
 a drug development asset, including the following:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">Probability of successfully completing clinical trials
 and obtaining regulatory approval;</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">Market size, market growth projections, and market
 share;</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">Estimates regarding the timing of and the expected
 costs to advance the Company&#x2019;s clinical programs to
 commercialization;</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">Estimates of future cash flows from potential product
 sales; and</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">A discount rate.</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Additionally, to the extent the Company acquire other
 indefinite-lived intangible assets through its business
 combinations, these assets are reviewed for impairment on an annual
 basis or more frequently if indicators of impairment are present.
 If the Company determines that the asset becomes impaired, the
 carrying value is written down to its fair value with the related
 impairment charge recognized in its consolidated statements of
 operations in the period in which the impairment occurs.</p>
 </div><span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_DeferredRentPolicyTextBlock', window );">Deferred Rent</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Deferred Rent</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company&#x2019;s lease agreements include payment escalations
 and lease incentives (including a leasehold improvement tenant
 allowance). For periods prior to January&#xA0;1, 2019, these
 payments were accrued or deferred as appropriate such that rent
 expense was recognized on a straight-line basis over the respective
 lease terms. Effective January&#xA0;1, 2019, upon the adoption of
 ASC 842,deferred rent was reclassified as a reduction to the
 applicable <font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font> asset as further
 described in Note 8.</p>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueMeasurementPolicyPolicyTextBlock', window );">Fair Value Measurements</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Fair Value Measurements</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Certain assets and liabilities of the Company are carried at fair
 value under GAAP. Fair value is defined as the exchange price that
 would be received for an asset or paid to transfer a liability (an
 exit price) in the principal or most advantageous market for the
 asset or liability in an orderly transaction between market
 participants on the measurement date. Valuation techniques used to
 measure fair value must maximize the use of observable inputs and
 minimize the use of unobservable inputs. Financial assets and
 liabilities carried at fair value are to be classified and
 disclosed in one of the following three levels of the fair value
 hierarchy, of which the first two are considered observable and the
 last is considered unobservable:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">Level 1&#x2014;Quoted prices in active markets for
 identical assets or liabilities.</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">Level 2&#x2014;Observable inputs (other than
 Level&#xA0;1 quoted prices), such as quoted prices in active
 markets for similar assets or liabilities, quoted prices in markets
 that are not active for identical or similar assets or liabilities,
 or other inputs that are observable or can be corroborated by
 observable market data.</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 6pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="PAGE-BREAK-INSIDE: avoid">
 <td width="5%">&#xA0;</td>
 <td valign="top" width="2%" align="left">&#x2022;</td>
 <td valign="top" width="1%">&#xA0;</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt" align="left">Level 3&#x2014;Unobservable inputs that are supported
 by little or no market activity that are significant to determining
 the fair value of the assets or liabilities, including pricing
 models, discounted cash flow methodologies and similar
 techniques.</p>
 </td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Prior to the Merger, the Company&#x2019;s preferred stock warrant
 liability, derivative liability and preferred stock repurchase
 liability were carried at fair value, determined according to
 Level&#xA0;3 inputs in the fair value hierarchy described above
 (See Note&#xA0;4). The Company&#x2019;s cash equivalents, consisting
 of money market funds invested in U.S. Treasury securities, are
 carried at fair value, determined based on Level&#xA0;2 inputs in
 the fair value hierarchy described above (see Note 4). The carrying
 values of the Company&#x2019;s accounts payable and accrued expenses
 approximate their fair values due to the short-term nature of these
 liabilities. The carrying value of the Company&#x2019;s outstanding
 loan and security agreement (the &#x201C;Hercules Loan
 Agreement&#x201D;) with Hercules Capital, Inc.
 (&#x201C;Hercules&#x201D;) approximates its fair value at
 March&#xA0;31, 2019 because the debt bears interest at a variable
 market rate and the Company&#x2019;s credit risk has not materially
 changed since the inception of the agreement. The carrying value of
 the Company&#x2019;s loans under the funding agreements with
 &#xD6;sterreichische Forschungsf&#xF6;rderungsgesellschaft mbH
 (&#x201C;FFG&#x201D;) were recorded at fair value on the opening
 balance sheet of Arsanis as of the date of the Merger, and
 approximates the fair value of the loans at March&#xA0;31, 2019.
 (See Note&#xA0;3).</p>
 </div><span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SegmentReportingPolicyPolicyTextBlock', window );">Segment Information</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Segment Information</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company manages its operations as a single operating segment
 for the purposes of assessing performance and making operating
 decisions. The Company&#x2019;s focus is on the discovery,
 development and commercialization of novel therapeutics for the
 treatment of rare diseases.</p>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RevenueFromContractWithCustomerPolicyTextBlock', window );">Revenue Recognition</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Revenue Recognition</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Effective January&#xA0;1, 2018, the Company adopted ASC Topic 606,
 Revenue from Contracts with Customers (&#x201C;ASC 606&#x201D;),
 using the modified retrospective transition method. The modified
 retrospective method requires that the cumulative effect of
 initially applying ASC 606 be recognized as an adjustment to the
 opening balance of retained earnings or accumulated deficit of the
 annual period that includes the date of initial application. The
 Company did not have any arrangements that were in the scope of ASC
 606 on January&#xA0;1, 2018 and thus there was no impact to the
 condensed consolidated financial statements as a result of the
 adoption. This standard applies to all contracts with customers,
 except for contracts that are within the scope of other standards,
 such as collaboration arrangements and leases. Prior to completion
 of the Merger, Arsanis entered into a
 single&#xA0;<font style="WHITE-SPACE: nowrap">out-licensing</font>&#xA0;agreement
 with Janssen Pharmaceuticals, Inc. (see Note 13) that was within
 the scope of ASC 606.</p>
 </div><span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ResearchAndDevelopmentPolicyTextBlock', window );">Research and Development Programs</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Research and Development Programs</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Proceeds under the research and development incentive program from
 the Austrian government are recognized as other income in an amount
 equal to the qualifying expenses incurred in each period multiplied
 by the applicable reimbursement percentage. Incentive income
 recognized upon incurring qualifying expenses in advance of receipt
 of proceeds from research and development incentives is recorded in
 the consolidated balance sheet as research and development
 incentive receivables.</p>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ResearchAndDevelopmentExpensePolicy', window );">Research and Development Costs</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Research and Development Costs</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Costs associated with internal research and development and
 external research and development services, including drug
 development and preclinical studies, are expensed as incurred.
 Research and development expenses include costs for salaries,
 employee benefits, subcontractors, facility-related expenses,
 depreciation and amortization, stock-based compensation,
 third-party license fees, laboratory supplies, and external costs
 of outside vendors engaged to conduct discovery, preclinical and
 clinical development activities and clinical trials as well as to
 manufacture clinical trial materials, and other costs. The Company
 recognizes external research and development costs based on an
 evaluation of the progress to completion of specific tasks using
 information provided to the Company by its service providers.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Nonrefundable advance payments for goods or services to be received
 in the future for use in research and development activities are
 recorded as prepaid expenses. Such prepaid expenses are recognized
 as an expense when the goods have been delivered or the related
 services have been performed, or when it is no longer expected that
 the goods will be delivered or the services rendered.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Upfront payments, milestone payments and annual maintenance fees
 under license agreements are expensed in the period in which they
 are incurred.</p>
 </div><span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_IntangibleAssetsFiniteLivedPolicyCostsIncurredToRenewOrExtend', window );">Patent Costs</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Patent Costs</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 All patent-related costs incurred in connection with filing and
 prosecuting patent applications are expensed as incurred due to the
 uncertainty about the recovery of the expenditure. Amounts incurred
 are classified as general and administrative expenses.</p>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtPolicyTextBlock', window );">Debt Issuance Costs</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Debt Issuance Costs</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Debt issuance costs consist of payments made to secure commitments
 under certain debt financing arrangements. These amounts are
 recognized as interest expense over the period of the financing
 arrangement using the effective interest method. If the financing
 arrangement is canceled or forfeited, or if the utility of the
 arrangement to the Company is otherwise compromised, these costs
 are recognized as interest expense immediately. The Company&#x2019;s
 consolidated financial statements present debt issuance costs
 related to a recognized debt liability as a direct reduction from
 the carrying amount of that debt liability.</p>
 </div><span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy', window );">Stock-Based Compensation</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Stock-Based Compensation</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The Company measures all stock-based awards granted to employees
 and directors based on the fair value on the date of the grant and
 recognizes compensation expense for those awards, net of estimated
 forfeitures, over the requisite service period, which is generally
 the vesting period of the respective award. The Company issues
 stock-based awards with only service-based vesting conditions and
 records the expense for these awards using the straight-line
 method. The Company has not issued any stock-based awards with
 performance-based vesting conditions.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Effective January&#xA0;1, 2019, the Company adopted ASU
 No.&#xA0;<font style="WHITE-SPACE: nowrap">2018-07,&#xA0;Compensation&#x2014;Stock</font>&#xA0;Compensation
 (Topic 718): Improvements to Nonemployee Share-Based Payment
 Accounting&#xA0;(&#x201C;ASU&#xA0;<font style="WHITE-SPACE: nowrap">2018-07&#x201D;),</font>&#xA0;which
 expands the scope of Topic 718 to include share-based payment
 awards to nonemployees. As a result, stock-based awards granted to
 consultants and&#xA0;<font style="WHITE-SPACE: nowrap">non-employees</font>&#xA0;are
 accounted for in the same manner as awards granted to employees and
 directors as described above. The impact of adoption this new
 guidance did not have a material impact on the Company&#x2019;s
 consolidated financial statements. Prior to the adoption of
 ASU&#xA0;<font style="WHITE-SPACE: nowrap">2018-07,</font>&#xA0;for
 stock-based awards granted to&#xA0;<font style="WHITE-SPACE: nowrap">non-employee</font>consultants, compensation
 expense was recognized over the period during which services were
 rendered by such&#xA0;<font style="WHITE-SPACE: nowrap">non-employee</font>&#xA0;consultants
 until completed. At the end of each financial reporting period
 prior to completion of the service, the fair value of these awards
 was remeasured using the then-current fair value of the
 Company&#x2019;s common stock and updated assumption inputs in the
 Black-Scholes option-pricing model.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The Company classifies stock-based compensation expense in its
 consolidated statement of operations and comprehensive loss in the
 same manner in which the award recipient&#x2019;s payroll costs are
 classified or in which the award recipient&#x2019;s service payments
 are classified.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The Company recognizes compensation expense for only the portion of
 awards that are expected to vest. In developing a forfeiture rate
 estimate, the Company has considered its historical experience to
 estimate&#xA0;<font style="WHITE-SPACE: nowrap">pre-vesting</font>&#xA0;forfeitures
 for service-based awards. The impact of a forfeiture rate
 adjustment will be recognized in full in the period of adjustment,
 and if the actual forfeiture rate is materially different from the
 Company&#x2019;s estimate, the Company may be required to record
 adjustments to stock-based compensation expense in future
 periods.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The fair value of each stock option grant is estimated on the date
 of grant using the Black-Scholes option-pricing model. Prior to
 March&#xA0;13, 2019, the Company had been a private company and
 lacked company-specific historical and implied volatility
 information for its stock. Therefore, the Company estimates its
 expected stock price volatility based on the historical volatility
 of publicly traded peer companies and expects to continue to do so
 until it has adequate historical data regarding the volatility of
 its own traded stock price. The expected term of the
 Company&#x2019;s stock options has been determined utilizing the
 &#x201C;simplified&#x201D; method for awards that qualify as
 &#x201C;plain-vanilla&#x201D; options. The expected term of stock
 options granted to&#xA0;<font style="WHITE-SPACE: nowrap">non-employee</font>&#xA0;consultants
 is equal to the contractual term of the option award. The risk-free
 interest rate is determined by reference to the U.S. Treasury yield
 curve in effect at the time of grant of the award for time periods
 approximately equal to the expected term of the award. Expected
 dividend yield is based on the fact that the Company has never paid
 cash dividends on common stock and does not expect to pay any cash
 dividends in the foreseeable future.</p>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_PreferredStockWarrantLiabilityPolicyTextBlock', window );">Preferred Stock Repurchase Liability</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Preferred Stock Warrant Liability</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Prior to the Merger with Arsanis, the Company classified warrants
 for the purchase of shares of its convertible preferred stock (see
 Note&#xA0;10) as a liability on its consolidated balance sheets as
 these warrants are freestanding financial instruments that may have
 required the Company to transfer assets upon exercise. The warrant
 liability, which consisted of warrants for the purchase of
 Series&#xA0;A and Series&#xA0;B convertible preferred stock, was
 initially recorded at fair value upon the date of issuance of each
 warrant and is subsequently remeasured to fair value at each
 reporting date. Changes in the fair value of the warrant liability
 are recognized as a component of other income (expense), net in the
 consolidated statement of operations and comprehensive loss.
 Concurrent with the closing of the Merger, all X4 preferred stock
 was converted to Arsanis common stock and the X4 preferred stock
 warrants converted to warrants for the purchase of Arsanis common
 stock. The Company assessed the features of the warrants and
 determined that they qualify for classification as permanent
 equity. Accordingly, the Company remeasured the warrants to fair
 value upon the closing of the Merger and reclassified the resulting
 warrant liability to additional&#xA0;<font style="WHITE-SPACE: nowrap">paid-in</font>&#xA0;capital.
 (see Note&#xA0;10).</p>
 </div><span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DerivativesPolicyTextBlock', window );">Derivative Liability</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Derivative Liability</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company&#x2019;s license agreement with Genzyme Corporation
 (&#x201C;Genzyme&#x201D;) (see Note&#xA0;13) contained a contingent
 payment obligation that required the Company to make a cash payment
 to Genzyme upon a change of control event of the Company. The
 contingent payment obligation met the definition of a derivative
 instrument as the contingent payment obligation was not clearly and
 closely related to its host instrument and was a cash-settled
 liability. Accordingly, the Company classified this derivative as a
 liability within other liabilities <font style="WHITE-SPACE: nowrap">(non-current)</font> on its condensed
 consolidated balance sheet. The derivative liability was initially
 recorded at fair value on the date of entering into the license
 agreement and was subsequently remeasured to fair value at each
 reporting date. Changes in the fair value of this derivative
 liability were recognized as a component of other income (expense),
 net in the condensed consolidated statement of operations and
 comprehensive loss. The Merger with Arsanis (see Note 1) qualified
 as a change of control event, as defined in the license agreement,
 but resulted in no payment being due to Genzyme under the license
 agreement. As a result, on March&#xA0;13, 2019, the closing date of
 the Merger with Arsanis, the derivative liability was remeasured to
 fair value, which was $0, and subsequent changes in fair value will
 no longer be recognized in the consolidated statements of
 operations and comprehensive loss because the contingent payment
 obligation to Genzyme expired at that time.</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 12px">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 0pt">
 In addition, the Company&#x2019;s Hercules loan (see Note&#xA0;7)
 contains a redemption feature that, upon an event of default,
 provides Hercules the option to accelerate and demand repayment of
 the debt, including a prepayment premium. The redemption feature
 meets the definition of a derivative instrument as the repayment of
 the debt contains a substantial premium, resulting in the
 redemption feature not being clearly and closely related to its
 host instrument. Accordingly, the Company classifies this
 derivative as a liability within other liabilities <font style="WHITE-SPACE: nowrap">(non-current)</font> on its condensed
 consolidated balance sheet. The derivative liability was initially
 recorded at fair value on the date of entering into the Hercules
 Loan Agreement and is subsequently remeasured to fair value at each
 reporting date. Changes in the fair value of this derivative
 liability are recognized as a component of other income (expense),
 net in the condensed consolidated statement of operations and
 comprehensive loss. Changes in the fair value of this derivative
 liability will continue to be recognized until all amounts
 outstanding under the Hercules Loan Agreement are repaid or until
 the Hercules Loan Agreement is terminated.</p>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ComprehensiveIncomePolicyPolicyTextBlock', window );">Comprehensive Loss</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Comprehensive Loss</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Comprehensive loss includes net loss as well as other changes in
 stockholders&#x2019; equity (deficit) that result from transactions
 and economic events other than those with stockholders. For the
 three months ended March&#xA0;31, 2019, comprehensive loss included
 $23 of foreign currency translation gain adjustments.</p>
 </div><span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_IncomeTaxPolicyTextBlock', window );">Income Taxes</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Income Taxes</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company accounts for income taxes using the asset and liability
 method, which requires the recognition of deferred tax assets and
 liabilities for the expected future tax consequences of events that
 have been recognized in the consolidated financial statements or in
 the Company&#x2019;s tax returns. Deferred tax assets and
 liabilities are determined based on the difference between the
 financial statement and tax basis of assets and liabilities using
 enacted tax rates in effect for the year in which the differences
 are expected to reverse. Changes in deferred tax assets and
 liabilities are recorded in the provision for income taxes. The
 Company assesses the likelihood that its deferred tax assets will
 be recovered from future taxable income and, to the extent it
 believes, based upon the weight of available evidence, that it is
 more likely than not that all or a portion of the deferred tax
 assets will not be realized, a valuation allowance is established
 through a charge to income tax expense. Potential for recovery of
 deferred tax assets is evaluated by estimating the future taxable
 profits expected and considering prudent and feasible tax planning
 strategies.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company accounts for uncertainty in income taxes recognized in
 the consolidated financial statements by applying a <font style="WHITE-SPACE: nowrap">two-step</font> process to determine the
 amount of tax benefit to be recognized. First, the tax position
 must be evaluated to determine the likelihood that it will be
 sustained upon external examination by the taxing authorities. If
 the tax position is deemed <font style="WHITE-SPACE: nowrap">more-likely-than-not</font> to be sustained,
 the tax position is then assessed to determine the amount of
 benefit to recognize in the consolidated financial statements. The
 amount of the benefit that may be recognized is the largest amount
 that has a greater than 50% likelihood of being realized upon
 ultimate settlement. The provision for income taxes includes the
 effects of any resulting tax reserves, or unrecognized tax
 benefits, that are considered appropriate as well as the related
 net interest and penalties.</p>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_EarningsPerSharePolicyTextBlock', window );">Net Income (Loss) per Share</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Net Income (Loss) per Share</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 The Company follows the <font style="WHITE-SPACE: nowrap">two-class</font> method when computing net
 income (loss) per share as the Company has issued shares that meet
 the definition of participating securities. The <font style="WHITE-SPACE: nowrap">two-class</font> method determines net income
 (loss) per share for each class of common and participating
 securities according to dividends declared or accumulated and
 participation rights in undistributed earnings. The <font style="WHITE-SPACE: nowrap">two-class</font> method requires income
 available to common stockholders for the period to be allocated
 between common and participating securities based upon their
 respective rights to receive dividends as if all income for the
 period had been distributed.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 Basic net income (loss) per share attributable to common
 stockholders is computed by dividing the net income (loss)
 attributable to common stockholders by the weighted average number
 of common shares outstanding for the period. Diluted net income
 (loss) attributable to common stockholders is computed by adjusting
 net income (loss) attributable to common stockholders to reallocate
 undistributed earnings based on the potential impact of dilutive
 securities. Diluted net income (loss) per share attributable to
 common stockholders is computed by dividing the diluted net income
 (loss) attributable to common stockholders by the weighted average
 number of common shares outstanding for the period, including
 potential dilutive common shares. For purpose of this calculation,
 outstanding stock options, convertible preferred stock and warrants
 to purchase shares of convertible preferred stock are considered
 potential dilutive common shares.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company&#x2019;s convertible preferred stock contractually
 entitles the holders of such shares to participate in dividends but
 does not contractually require the holders of such shares to
 participate in losses of the Company. Accordingly, in periods in
 which the Company reports a net loss attributable to common
 stockholders, such losses are not allocated to such participating
 securities. In periods in which the Company reports a net loss
 attributable to common stockholders, diluted net loss per share
 attributable to common stockholders is the same as basic net loss
 per share attributable to common stockholders, since dilutive
 common shares are not assumed to have been issued if their effect
 is anti-dilutive. The Company reported a net loss attributable to
 common stockholders for the three months ended March&#xA0;31, 2019
 and 2018.</p>
 </div><span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock', window );">Recently Adopted Accounting Pronouncements</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Recently Adopted Accounting Pronouncements</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In February 2016, the FASB issued
 ASU&#xA0;<font style="WHITE-SPACE: nowrap">No.&#xA0;2016-02</font><i>,
 Leases
 (Topic</i><i>&#xA0;842)</i>&#xA0;(&#x201C;ASU&#xA0;<font style="WHITE-SPACE: nowrap">2016-02&#x201D;</font>&#xA0;or
 &#x201C;ASC 842&#x201D;)), which sets out the principles for the
 recognition, measurement, presentation and disclosure of leases for
 both parties to a contract (i.e., lessees and lessors). The new
 standard requires lessees to apply a dual approach, classifying
 leases as either finance or operating leases based on the principle
 of whether or not the lease is effectively a financed purchase by
 the lessee. This classification will determine whether lease
 expense is recognized based on an effective interest method or on a
 straight-line basis over the term of the lease. A lessee is also
 required to record a&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font>&#xA0;asset
 and a lease liability for all leases with a term of greater than
 12&#xA0;months regardless of their classification. Leases with a
 term of 12 months or less may be accounted for similar to prior
 guidance for operating leases. The Company adopted the new leasing
 standard as of the required effective date of January&#xA0;1, 2019
 using a modified retrospective transition approach to be applied to
 leases existing as of, or entered into after, January&#xA0;1, 2019.
 The adoption had no impact on accumulated deficit. The new lease
 standard provides a number of optional practical expedients in
 transition. The Company applied the package of practical expedients
 to leases that commenced prior to the effective date, whereby it
 will elect to not reassess the following: (i)&#xA0;whether any
 expired or existing contracts contain leases; (ii)&#xA0;the lease
 classification for any expired or existing leases; and
 (iii)&#xA0;initial direct costs for any existing leases. The
 Company also elected the short-term lease recognition exemption for
 all leases that qualify, where a&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use</font></font>&#xA0;asset
 or lease liability will not be recognized for short-term leases.
 Upon the adoption of ASC 842, the Company recorded
 $2.5&#xA0;million of operating lease liabilities and
 $2.0&#xA0;million of&#xA0;<font style="WHITE-SPACE: nowrap"><font style="WHITE-SPACE: nowrap">right-of-use&#xA0;assets</font></font>&#xA0;on
 its consolidated balance. The adoption did not have a material
 impact on the Company&#x2019;s statement of operations, statement of
 comprehensive loss or statement of cash flows.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In January 2017, the FASB issued ASU&#xA0;<font style="WHITE-SPACE: nowrap">No.&#xA0;2017-04,</font><i>&#xA0;Intangibles-Goodwill
 and Other (Topic 350): Simplifying the Test for Goodwill
 Impairment.</i>&#xA0;The new standard simplifies the subsequent
 measurement of goodwill by eliminating the second step of the
 goodwill impairment test. This ASU will be applied prospectively
 and is effective for annual or interim goodwill impairment tests in
 fiscal years beginning after December&#xA0;15, 2019 with early
 adoption permitted. The Company has adopted this guidance on
 January&#xA0;1, 2019 and will apply it to its annual impairment
 test, and any interim impairment tests during the year ending
 December&#xA0;31, 2019.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In April 2017, the FASB issued ASU&#xA0;<font style="WHITE-SPACE: nowrap">2017-08,</font><i>&#xA0;Receivables &#x2013;
 Nonrefundable Fees and Other
 Costs</i>&#xA0;(&#x201C;Subtopic&#xA0;<font style="WHITE-SPACE: nowrap">310-20&#x201D;).</font>&#xA0;The
 new standard amends the amortization period for certain purchased
 callable debt securities held at a premium by shortening the
 amortization period for the premium to the earliest call
 date.&#xA0;Subtopic&#xA0;<font style="WHITE-SPACE: nowrap">310-20</font>&#xA0;calls for a
 modified retrospective application under which&#xA0;a
 cumulative-effect adjustment will be made to retained earnings as
 of the beginning of the first reporting period in which the
 guidance is adopted.&#xA0;The new standard will be effective
 beginning January&#xA0;1, 2019 and early adoption is permitted for
 public entities.&#xA0;The Company adopted this guidance, effective
 January&#xA0;1, 2019, and its adoption had no impact on the
 Company&#x2019;s financial position, results of operations or cash
 flows.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In July 2017, the FASB issued ASU&#xA0;<font style="WHITE-SPACE: nowrap">No.&#xA0;2017-11,</font>&#xA0;<i>Earnings
 Per Share (Topic</i><i>&#xA0;260), Distinguishing Liabilities from
 Equity (Topic</i><i>&#xA0;480), Derivatives and Hedging
 (Topic</i><i>&#xA0;815) (Part</i><i>&#xA0;I) Accounting for Certain
 Financial Instruments with Down Round Features
 (Part</i><i>&#xA0;II) Replacement of the Indefinite Deferral for
 Mandatorily Redeemable Financial Instruments of Certain Nonpublic
 Entities and Certain Mandatorily Redeemable Noncontrolling
 Interests with a Scope
 Exception</i>&#xA0;(&#x201C;ASU&#xA0;<font style="WHITE-SPACE: nowrap">2017-11&#x201D;).</font>&#xA0;Part&#xA0;I
 applies to entities that issue financial instruments such as
 warrants, convertible debt or convertible preferred stock that
 contain down-round features. Part&#xA0;II replaces the indefinite
 deferral for certain mandatorily redeemable noncontrolling
 interests and mandatorily redeemable financial instruments of
 nonpublic entities contained within ASC Topic&#xA0;480 with a scope
 exception and does not impact the accounting for these mandatorily
 redeemable instruments. For public entities,
 ASU&#xA0;<font style="WHITE-SPACE: nowrap">2017-11</font>&#xA0;is effective
 for annual reporting periods beginning after December&#xA0;15,
 2018, including interim periods within those fiscal years. The
 Company adopted ASU&#xA0;<font style="WHITE-SPACE: nowrap">2017-11</font>&#xA0;as of the
 required effective date of January&#xA0;1, 2019. The adoption of
 ASU&#xA0;<font style="WHITE-SPACE: nowrap">2017-11</font>&#xA0;had no
 impact on the Company&#x2019;s financial position, results of
 operations or cash flows.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In June 2018, the FASB issued ASU&#xA0;<font style="WHITE-SPACE: nowrap">No.&#xA0;2018-07,</font>&#xA0;<i>Compensation&#x2014;Stock
 Compensation (Topic</i><i>&#xA0;718): Improvements to Nonemployee
 Share-Based Payment
 Accounting&#xA0;</i>(&#x201C;ASU&#xA0;<font style="WHITE-SPACE: nowrap">2018-07&#x201D;).</font>&#xA0;These
 amendments expand the scope of Topic&#xA0;718,
 Compensation&#x2014;Stock Compensation (which previously only
 included share-based payments to employees) to include share-based
 payments issued to&#xA0;<font style="WHITE-SPACE: nowrap">non-employees</font>&#xA0;for
 goods or services. Consequently, the accounting for share-based
 payments to&#xA0;<font style="WHITE-SPACE: nowrap">non-employees</font>&#xA0;and
 employees will be substantially aligned. The ASU
 supersedes&#xA0;<font style="WHITE-SPACE: nowrap">Subtopic&#xA0;505-50,</font>&#xA0;Equity&#x2014;<i>Equity-Based
 Payments to&#xA0;<font style="WHITE-SPACE: nowrap">Non-Employees</font></i>. The Company adopted
 ASU&#xA0;<font style="WHITE-SPACE: nowrap">2018-07</font>&#xA0;on
 January&#xA0;1, 2019. The adoption of this standard had no impact
 on the Company&#x2019;s financial statements.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 18pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 <b><i>Recently Issued Accounting Pronouncements</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In August 2018, the FASB issued ASU&#xA0;<font style="WHITE-SPACE: nowrap">No.&#xA0;2018-13,</font><i>&#xA0;Fair
 Value Measurement (Topic 820): Disclosure Framework&#x2014;Changes
 to the Disclosure Requirements for Fair Value
 Measurement</i>&#xA0;(&#x201C;ASU&#xA0;<font style="WHITE-SPACE: nowrap">2018-13&#x201D;),</font>&#xA0;which&#xA0;removes,
 adds and modifies certain disclosure requirements for fair value
 measurements in Topic 820. The Company will no longer be required
 to disclose the amount of and reasons for transfers between
 Level&#xA0;1 and Level&#xA0;2 of the fair value hierarchy as well
 as the valuation processes of Level&#xA0;3 fair value measurements.
 However, the Company will be required to additionally disclose the
 changes in unrealized gains and losses included in other
 comprehensive income for recurring Level&#xA0;3 fair value
 measurements and the range and weighted average of assumptions used
 to develop significant unobservable inputs for Level&#xA0;3 fair
 value measurements. ASU&#xA0;<font style="WHITE-SPACE: nowrap">2018-13</font>&#xA0;is effective
 for fiscal years, and interim periods within those fiscal years,
 beginning after December&#xA0;15, 2019. The amendments relating to
 additional disclosure requirements will be applied prospectively
 for only the most recent interim or annual period presented in the
 initial year of adoption. All other amendments will be applied
 retrospectively to all periods presented upon their effective date.
 The Company is currently evaluating the impact that the adoption of
 ASU&#xA0;<font style="WHITE-SPACE: nowrap">2018-13</font>&#xA0;will have on
 its consolidated financial statements.</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 In August 2018, the FASB issued ASU&#xA0;<font style="WHITE-SPACE: nowrap">2018-15,</font><i>&#xA0;Intangibles-Goodwill
 and&#xA0;<font style="WHITE-SPACE: nowrap">Other-Internal-Use</font>&#xA0;Software
 (Subtopic&#xA0;<font style="WHITE-SPACE: nowrap">350-40):</font>&#xA0;Customer&#x2019;s
 Accounting for Implementation Costs Incurred in a Cloud Computing
 Arrangement That Is a Service Contract,
 (&#x201C;ASU&#xA0;<font style="WHITE-SPACE: nowrap">2018-15&#x201D;)</font></i>. The amendments in
 this update align the requirements for capitalizing implementation
 costs incurred in a hosting arrangement that is a service contract
 with the requirements for capitalizing implementation costs
 incurred to develop or obtain&#xA0;<font style="WHITE-SPACE: nowrap">internal-use</font>&#xA0;software
 (and hosting arrangements that include
 an&#xA0;<font style="WHITE-SPACE: nowrap">internal-use</font>&#xA0;software
 license). The accounting for the service element of a hosting
 arrangement that is a service contract is not affected by the
 amendments in this update. The new standard will be effective
 beginning January&#xA0;1, 2020 and early adoption is permitted. The
 amendments in this update should be applied either retrospectively
 or prospectively to all implementation costs incurred after the
 date of adoption.&#xA0;The Company is currently evaluating the
 impact that the adoption of ASU&#xA0;<font style="WHITE-SPACE: nowrap">2018-15</font>&#xA0;will have on
 its consolidated financial statements.</p>
 </div><span></span>
</td>
</tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for basis of accounting, or basis of presentation, used to prepare the financial statements (for example, US Generally Accepted Accounting Principles, Other Comprehensive Basis of Accounting, IFRS).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for cash and cash equivalents, including the policy for determining which items are treated as cash equivalents. Other information that may be disclosed includes (1) the nature of any restrictions on the entity's use of its cash and cash equivalents, (2) whether the entity's cash and cash equivalents are insured or expose the entity to credit risk, (3) the classification of any negative balance accounts (overdrafts), and (4) the carrying basis of cash equivalents (for example, at cost) and whether the carrying amount of cash equivalents approximates fair value.</p></div>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Entity's cash and cash equivalents accounting policy with respect to restricted balances.  Restrictions may include legally restricted deposits held as compensating balances against short-term borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits.</p></div>
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<td><strong> Period Type:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for comprehensive income.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example, common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting.  The accounting policy may also address the accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 810<br> -SubTopic 10<br> -Section S99<br> -Paragraph 2<br> -Subparagraph (SX 210.3A-02)<br> -URI http://asc.fasb.org/extlink&amp;oid=27015204&amp;loc=d3e355033-122828<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 810<br> -SubTopic 10<br> -Section S99<br> -Paragraph 3<br> -Subparagraph (SX 210.3A-03)<br> -URI http://asc.fasb.org/extlink&amp;oid=27015204&amp;loc=d3e355100-122828<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=84158767&amp;loc=d3e18780-107790<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 810<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=109239629&amp;loc=d3e5614-111684<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy related to debt. Includes, but is not limited to, debt issuance costs, the effects of refinancings, method of amortizing debt issuance costs and original issue discount, and classifications of debt.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=84158767&amp;loc=d3e18780-107790<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 470<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6802200&amp;loc=d3e1835-112601<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtPolicyTextBlock</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for its derivative instruments and hedging activities.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 815<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109980867&amp;loc=d3e41620-113959<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=84158767&amp;loc=d3e18780-107790<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 815<br> -SubTopic 10<br> -Section 50<br> -Paragraph 4<br> -URI http://asc.fasb.org/extlink&amp;oid=109980867&amp;loc=d3e41638-113959<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 815<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1A<br> -URI http://asc.fasb.org/extlink&amp;oid=109980867&amp;loc=SL5579245-113959<br><br>Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 815<br> -SubTopic 10<br> -Section 50<br> -Paragraph 7<br> -URI http://asc.fasb.org/extlink&amp;oid=109980867&amp;loc=d3e41675-113959<br><br>Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.4-08.(n))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e23780-122690<br><br>Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 815<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=109980867&amp;loc=SL5579240-113959<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DerivativesPolicyTextBlock</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for computing basic and diluted earnings or loss per share for each class of common stock and participating security. Addresses all significant policy factors, including any antidilutive items that have been excluded from the computation and takes into account stock dividends, splits and reverse splits that occur after the balance sheet date of the latest reporting period but before the issuance of the financial statements.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 260<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=6371337&amp;loc=d3e3550-109257<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 260<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6371337&amp;loc=d3e3550-109257<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=84158767&amp;loc=d3e18780-107790<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 260<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=6371337&amp;loc=d3e3630-109257<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_EarningsPerSharePolicyTextBlock</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for fair value measurements of financial and non-financial assets, liabilities and instruments classified in shareholders' equity. Disclosures include, but are not limited to, how an entity that manages a group of financial assets and liabilities on the basis of its net exposure measures the fair value of those assets and liabilities.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<tr>
<td><strong> Period Type:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for (1) transactions denominated in a currency other than the reporting enterprise's functional currency, (2) translating foreign currency financial statements that are incorporated into the financial statements of the reporting enterprise by consolidation, combination, or the equity method of accounting, and (3) remeasurement of the financial statements of a foreign reporting enterprise in a hyperinflationary economy.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=84158767&amp;loc=d3e18780-107790<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 830<br> -SubTopic 30<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6450520&amp;loc=d3e32583-110901<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 830<br> -SubTopic 20<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6450222&amp;loc=d3e30840-110895<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Period Type:</strong></td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_GoodwillAndIntangibleAssetsGoodwillPolicy">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for goodwill. This accounting policy also may address how an entity assesses and measures impairment of goodwill, how reporting units are determined, how goodwill is allocated to such units, and how the fair values of the reporting units are determined.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 350<br> -SubTopic 20<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=108376223&amp;loc=d3e13816-109267<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=84158767&amp;loc=d3e18780-107790<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for recognizing and measuring the impairment of long-lived assets. An entity also may disclose its accounting policy for long-lived assets to be sold. This policy excludes goodwill and intangible assets.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 360<br> -SubTopic 10<br> -Section 05<br> -Paragraph 4<br> -URI http://asc.fasb.org/extlink&amp;oid=109226317&amp;loc=d3e202-110218<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=84158767&amp;loc=d3e18780-107790<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 360<br> -SubTopic 10<br> -Section S99<br> -Paragraph 2<br> -Subparagraph (SAB Topic 5.CC)<br> -URI http://asc.fasb.org/extlink&amp;oid=27011434&amp;loc=d3e125687-122742<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ImpairmentOrDisposalOfLongLivedAssetsPolicyTextBlock</td>
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<tr>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for income taxes, which may include its accounting policies for recognizing and measuring deferred tax assets and liabilities and related valuation allowances, recognizing investment tax credits, operating loss carryforwards, tax credit carryforwards, and other carryforwards, methodologies for determining its effective income tax rate and the characterization of interest and penalties in the financial statements.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 740<br> -SubTopic 10<br> -Section 50<br> -Paragraph 20<br> -URI http://asc.fasb.org/extlink&amp;oid=84230637&amp;loc=d3e32847-109319<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 954<br> -SubTopic 740<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6491622&amp;loc=d3e9504-115650<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=84158767&amp;loc=d3e18780-107790<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 740<br> -SubTopic 10<br> -Section 50<br> -Paragraph 17<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=84230637&amp;loc=d3e32809-109319<br><br>Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 740<br> -SubTopic 10<br> -Section 50<br> -Paragraph 19<br> -URI http://asc.fasb.org/extlink&amp;oid=84230637&amp;loc=d3e32840-109319<br><br>Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 740<br> -SubTopic 10<br> -Section 45<br> -Paragraph 25<br> -URI http://asc.fasb.org/extlink&amp;oid=84176650&amp;loc=d3e32247-109318<br><br>Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 740<br> -SubTopic 10<br> -Section 45<br> -Paragraph 28<br> -URI http://asc.fasb.org/extlink&amp;oid=84176650&amp;loc=d3e32280-109318<br><br>Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 740<br> -SubTopic 30<br> -Section 05<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=65884525&amp;loc=d3e40913-109327<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_IncomeTaxPolicyTextBlock</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for the treatment of costs incurred to renew or extend the term of a recognized intangible asset.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 350<br> -SubTopic 30<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=66006027&amp;loc=d3e16323-109275<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy pertaining to new accounting pronouncements that may impact the entity's financial reporting. Includes, but is not limited to, quantification of the expected or actual impact.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for long-lived, physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, basis of assets, depreciation and depletion methods used, including composite deprecation, estimated useful lives, capitalization policy, accounting treatment for costs incurred for repairs and maintenance, capitalized interest and the method it is calculated, disposals and impairments.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.13(a))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 360<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6391035&amp;loc=d3e2868-110229<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=84158767&amp;loc=d3e18780-107790<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for costs it has incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=84158767&amp;loc=d3e18780-107790<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 730<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6420194&amp;loc=d3e21568-108373<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ResearchAndDevelopmentExpensePolicy</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Period Type:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for revenue from contract with customer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/exampleRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section 50<br> -Paragraph 4<br> -Subparagraph (e)<br> -URI http://asc.fasb.org/extlink&amp;oid=84158767&amp;loc=d3e18823-107790<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 606<br> -URI http://asc.fasb.org/topic&amp;trid=49130388<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for segment reporting.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=84158767&amp;loc=d3e18780-107790<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for stock option and stock incentive plans. This disclosure may include (1) the types of stock option or incentive plans sponsored by the entity (2) the groups that participate in (or are covered by) each plan (3) significant plan provisions and (4) how stock compensation is measured, and the methodologies and significant assumptions used to determine that measurement.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=84158767&amp;loc=d3e18780-107790<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (b),(f)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5047-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Disclosure of accounting policy for the use of estimates in the preparation of financial statements in conformity with generally accepted accounting principles.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 275<br> -SubTopic 10<br> -Section 50<br> -Paragraph 12<br> -URI http://asc.fasb.org/extlink&amp;oid=99393423&amp;loc=d3e6191-108592<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 275<br> -SubTopic 10<br> -Section 50<br> -Paragraph 11<br> -URI http://asc.fasb.org/extlink&amp;oid=99393423&amp;loc=d3e6161-108592<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 275<br> -SubTopic 10<br> -Section 50<br> -Paragraph 9<br> -URI http://asc.fasb.org/extlink&amp;oid=99393423&amp;loc=d3e6143-108592<br><br>Reference 4: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 275<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=99393423&amp;loc=d3e5967-108592<br><br>Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 275<br> -SubTopic 10<br> -Section 50<br> -Paragraph 4<br> -URI http://asc.fasb.org/extlink&amp;oid=99393423&amp;loc=d3e6061-108592<br><br>Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 275<br> -SubTopic 10<br> -Section 50<br> -Paragraph 8<br> -URI http://asc.fasb.org/extlink&amp;oid=99393423&amp;loc=d3e6132-108592<br><br>Reference 7: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 275<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=99393423&amp;loc=d3e5967-108592<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Concentration Of Credit Risk Policy Text Block.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
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</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_DeferredRentPolicyTextBlock">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Deferred Rent Policy.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_DeferredRentPolicyTextBlock</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Data Type:</strong></td>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
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<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_IntangibleAssetsPolicyTextBlock">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Intangible Assets [Policy Text Block]</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_IntangibleAssetsPolicyTextBlock</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Data Type:</strong></td>
<td>nonnum:textBlockItemType</td>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
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<td><strong> Period Type:</strong></td>
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</table></div>
</div></td></tr>
</table>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Preferred Stock Warrant Liability [Policy Text Block]</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_PreferredStockWarrantLiabilityPolicyTextBlock</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Data Type:</strong></td>
<td>nonnum:textBlockItemType</td>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
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<td><strong> Period Type:</strong></td>
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</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ResearchAndDevelopmentPolicyTextBlock">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Research And Development Policy [Text Block]</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ResearchAndDevelopmentPolicyTextBlock</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Data Type:</strong></td>
<td>nonnum:textBlockItemType</td>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_RightOfUseAssetAndLeaseLiabilityPolicyTextBlock">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Right of use asset and lease liability.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_RightOfUseAssetAndLeaseLiabilityPolicyTextBlock</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
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<td><strong> Data Type:</strong></td>
<td>nonnum:textBlockItemType</td>
</tr>
<tr>
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<td>na</td>
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<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
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</div>
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</DOCUMENT>
<DOCUMENT>
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<head>
<title></title>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6817692496">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Summary of Significant Accounting Policies (Tables)<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AccountingPoliciesAbstract', window );"><strong>Accounting Policies [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_PropertyPlantAndEquipmentUsefulLivesTableTextBlock', window );">Property and Equipment</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 18pt">
 <b><i>Property and Equipment</i></b></p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 6pt">
 Property and equipment are stated at cost less accumulated
 depreciation and amortization. Depreciation and amortization
 expense is recognized using the straight-line method over the
 estimated useful life of each asset, as follows:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="68%" align="center" border="0">
 <tr>
 <td width="62%"></td>
 <td valign="bottom" width="4%"></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" align="center"><b>Estimated&#xA0;Useful&#xA0;Life</b></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Office furniture</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" align="center">3 years</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Computer equipment</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" align="center">3 years</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Software</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" align="center">3 years</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Laboratory equipment</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" align="center">3 to 10 years</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Leasehold improvements</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" align="center">
 Shorter&#xA0;of&#xA0;lease&#xA0;term&#xA0;or&#xA0;10&#xA0;years</td>
 </tr>
 </table>
 </div><span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_AccountingPoliciesAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AccountingPoliciesAbstract</td>
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</table>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Property Plant And Equipment Useful Lives Table [Text Block]</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_PropertyPlantAndEquipmentUsefulLivesTableTextBlock</td>
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</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>XML
<SEQUENCE>43
<FILENAME>R27.htm
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
<script type="text/javascript" src="Show.js">/* Do Not Remove This Comment */</script><script type="text/javascript">
							function toggleNextSibling (e) {
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6817772656">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Merger Accounting (Tables)<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessCombinationsAbstract', window );"><strong>Business Combinations [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTextBlock', window );">Schedule of Business Acquisitions by Acquisition, Contingent Consideration</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The following summarizes the preliminary estimate of the purchase
 price paid in the Merger:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0">
 <tr>
 <td width="85%"></td>
 <td valign="bottom" width="9%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Number of shares of the combined organization owned by Arsanis
 stockholders&#xA0;(1)</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">2,440,582</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Multiplied by the fair value per share of Arsanis common
 stock&#xA0;(2)</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">18.66</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Fair value of consideration issued it effect the Merger</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">45,541</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Fair value of replacement awards held by former employees, board of
 directors and consultants of Arsanis that were vested as of the
 Merger.</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">817</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Purchase price:</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">46,358</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 2pt; FONT-SIZE: medium; FONT-FAMILY: &quot;Times New Roman&quot;; WIDTH: 124px; WHITE-SPACE: normal; WORD-SPACING: 0px; BORDER-BOTTOM: rgb(0,0,0) 1px solid; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; LINE-HEIGHT: 8pt; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="break-inside: avoid">
 <td valign="top" width="4%" align="left">(1)</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left">The number of shares of 2,440,582 represents the
 historical 14,643,737 shares of Arsanis common stock outstanding
 immediately prior to the closing of the Merger, adjusted for the
 Reverse Stock Split.</p>
 </td>
 </tr>
 </table>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="break-inside: avoid">
 <td valign="top" width="4%" align="left">(2)</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left">Based on the last reported sale price of Arsanis
 common stock on the Nasdaq Global Market on March&#xA0;13, 2019,
 the closing date of the Merger, and gives effect to the Reverse
 Stock Split.</p>
 </td>
 </tr>
 </table>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock', window );">Schedule of Recognized Identified Assets Acquired and Liabilities Assumed</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The following summarizes the allocation of the purchase price to
 the net tangible and intangible assets acquired:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0">
 <tr>
 <td width="85%"></td>
 <td valign="bottom" width="6%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Cash and cash equivalents and restricted cash</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">26,406</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Other current assets</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">2,147</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Property and equipment, net</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">68</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 IPR&amp;D indefinite-lived intangible assets</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">4,900</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Other assets,&#xA0;<font style="WHITE-SPACE: nowrap">non-current</font></p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">879</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Current liabilities</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(5,221</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Loans payable</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(8,713</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Other liabilities,&#xA0;<font style="WHITE-SPACE: nowrap">non-current</font></p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(1,515</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Goodwill</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">27,407</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
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 <td valign="bottom"></td>
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 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Purchase price</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">
 &#xA0;&#xA0;&#xA0;&#xA0;46,358</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
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 <br class="Apple-interchange-newline" /></div><span></span>
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</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionProFormaInformationTextBlock', window );">Business Acquisition, Pro Forma Information</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The following supplemental unaudited pro forma information presents
 the Company&#x2019;s financial results as if the acquisition of
 Arsanis had occurred on January&#xA0;1, 2018:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="76%" align="center" border="0">
 <tr>
 <td width="78%"></td>
 <td valign="bottom" width="4%"></td>
 <td></td>
 <td></td>
 <td></td>
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 <td></td>
 <td></td>
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 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="6" align="center"><b>Three Months Ended<br />
 March&#xA0;31,</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"><b>2019</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"><b>2018</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
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 <b>(unaudited)</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Revenue</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">0</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">0</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Net loss</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">(16,258</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">(20,235</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 </table>
 </div><span></span>
</td>
</tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Tabular disclosure of pro forma results of operations for a material business acquisition or series of individually immaterial business acquisitions that are material in the aggregate.</p></div>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Tabular disclosure of contingent payment arrangements including the terms that will result in payment and the accounting treatment that will be followed if such contingencies occur, including the potential impact on earnings per share if contingencies are to be settled in common stock of the entity. The description also may include the period over which amounts are expected to be paid, and changes in the amount since the previous reporting period. This also includes contingent options and commitments.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Tabular disclosure of the amounts recognized as of the acquisition date for each major class of assets acquired and liabilities assumed. May include but not limited to the following: (a) acquired receivables; (b) contingencies recognized at the acquisition date; and (c) the fair value of noncontrolling interests in the acquiree.</p></div>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6817746848">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Fair Value of Financial Assets and Liabilities (Tables)<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
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<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueDisclosuresAbstract', window );"><strong>Fair Value Disclosures [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueAssetsMeasuredOnRecurringBasisTextBlock', window );">Schedule of Assets and Liabilities Measured at Fair Value</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The following tables present information about the Company&#x2019;s
 financial assets and liabilities measured at fair value on a
 recurring basis and indicate the level of the fair value hierarchy
 used to determine such fair values:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="92%" align="center" border="0">
 <tr>
 <td width="60%"></td>
 <td valign="bottom" width="4%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="4%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="4%"></td>
 <td></td>
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 <td></td>
 <td valign="bottom" width="4%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="14" align="center"><b>Fair Value Measurements as of
 March&#xA0;31, 2019 Using:</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;Level&#xA0;1&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;Level&#xA0;2&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;Level&#xA0;3&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;Total&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Assets:</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Cash equivalents&#x2014;money market funds</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">22,299</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">22,299</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">22,299</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">22,299</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Liabilities:</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Preferred stock warrant liability</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Derivative liability</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">18</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">18</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">18</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">18</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="92%" align="center" border="0">
 <tr>
 <td width="61%"></td>
 <td valign="bottom" width="6%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="6%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="6%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="6%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="14" align="center"><b>Fair Value Measurements as of
 December&#xA0;31, 2018 Using:</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;Level&#xA0;1&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;Level&#xA0;2&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;Level&#xA0;3&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;Total&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Assets:</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Cash equivalents&#x2014;money market fund</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">8,134</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">8,134</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">8,134</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">8,134</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Liabilities:</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Preferred stock warrant liability</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">4,947</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">4,947</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Derivative liability</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">201</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">201</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">$</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">5,148</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">5,148</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 </table>
 <br class="Apple-interchange-newline" /></div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock', window );">Summary of Aggregate Fair Values of Warrant Liability and Derivative Liability and Preferred Stock Repurchase Liability</a></td>
<td class="text"><div>
 <p style="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">
 The following table provides a roll-forward of the aggregate fair
 values of the Company&#x2019;s warrant liability, derivative
 liability and preferred stock repurchase liability, for which fair
 values are determined using Level&#xA0;3 inputs:</p>
 <p style="font-size:12pt;margin-top:0pt;margin-bottom:0pt">
 &#xA0;</p>
 <table cellspacing="0" cellpadding="0" width="76%" border="0" style="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" align="center">
 <tr>
 <td width="74%"></td>
 <td valign="bottom" width="9%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="9%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" colspan="2" align="center" style="border-bottom:1.00pt solid #000000">
 <b>Preferred&#xA0;Stock</b><br />
 <b>Warrant</b><br />
 <b>Liability</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" colspan="2" align="center" style="border-bottom:1.00pt solid #000000"><b>Derivative</b><br />
 <b>Liability</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr bgcolor="#CCEEFF" style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
 <td valign="top">
 <p style=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">
 Balance as of December&#xA0;31, 2018</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">4,947</td>
 <td nowrap="nowrap" valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">201</td>
 <td nowrap="nowrap" valign="bottom">&#xA0;</td>
 </tr>
 <tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
 <td valign="top">
 <p style=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">
 Change in fair value</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">288</td>
 <td nowrap="nowrap" valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(183</td>
 <td nowrap="nowrap" valign="bottom">)&#xA0;</td>
 </tr>
 <tr bgcolor="#CCEEFF" style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
 <td valign="top">
 <p style=" margin-top:0pt ; margin-bottom:0pt; margin-left:3.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">
 Conversion of convertible preferred stock warrant into common stock
 warrant in connection with Merger</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(5,235</td>
 <td nowrap="nowrap" valign="bottom">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td nowrap="nowrap" valign="bottom">&#xA0;</td>
 <td nowrap="nowrap" valign="bottom" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td nowrap="nowrap" valign="bottom">&#xA0;</td>
 </tr>
 <tr style="font-size:1px;">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style=" margin-top:0pt ; margin-bottom:0pt; border-top:1.00px solid #000000">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
 <td valign="top">
 <p style=" margin-top:0pt ; margin-bottom:0pt; margin-left:1.00em; text-indent:-1.00em; font-size:10pt; font-family:Times New Roman">
 Balance as of March&#xA0;31, 2019</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td nowrap="nowrap" valign="bottom">$</td>
 <td nowrap="nowrap" valign="bottom" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td nowrap="nowrap" valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">18</td>
 <td nowrap="nowrap" valign="bottom">&#xA0;</td>
 </tr>
 <tr style="font-size:1px;">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style=" margin-top:0pt ; margin-bottom:0pt; border-top:3.00px double #000000">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 </table>
 </div><span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_FairValueAssetsMeasuredOnRecurringBasisTextBlock">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Tabular disclosure of assets, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, by class that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 820<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=99377789&amp;loc=d3e19207-110258<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 820<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=99377789&amp;loc=d3e19190-110258<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 820<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=99377789&amp;loc=d3e19207-110258<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Tabular disclosure of the fair value measurement of liabilities using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes attributable to the following: (1) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets), and gains or losses recognized in other comprehensive income (loss) and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (2) purchases, sales, issues, and settlements (each type disclosed separately); and (3) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs) by class of liability.</p></div>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6636851600">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Property and Equipment, Net (Tables)<br></strong></div></th>
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 &#xA0;</p>
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 Leasehold improvements</p>
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 Software</p>
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 Less: Accumulated depreciation and amortization</p>
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 &#xA0;</p>
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 &#xA0;</p>
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 &#xA0;</p>
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 &#xA0;</p>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Tabular disclosure of physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, balances by class of assets, depreciation and depletion expense and method used, including composite depreciation, and accumulated deprecation.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(13))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 360<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6391035&amp;loc=d3e2868-110229<br></p></div>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6827302352">
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 <b>2018</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Accrued employee compensation and benefits</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">
 &#xA0;&#xA0;&#xA0;&#xA0;1,239</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">924</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Accrued external research and development expenses</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">819</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">754</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Accrued professional fees</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,850</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,324</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Deferred rent, current portion</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">93</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Other</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">271</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">156</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">4,179</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">3,251</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6824551408">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Long-Term Debt (Tables)<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtDisclosureAbstract', window );"><strong>Debt Disclosure [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
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<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ScheduleOfDebtTableTextBlock', window );">Summary of Long Term Debt</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Long-term debt consisted of the following:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
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 <td></td>
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 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;March&#xA0;31,&#xA0;&#xA0;&#xA0;</b><br />
 <b>2019</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>December&#xA0;31,</b><br />
 <b>2018</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Principal amount of long-term debt</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19,546</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">10,000</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Less: Current portion of long-term debt</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(5,298</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(1,687</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
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 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Long-term debt, net of current portion</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">14,248</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">8,313</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Debt discount, net of accretion</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(1,019</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
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 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Cumulative accretion of final payment due at maturity</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">136</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">58</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Long-term debt, including accretion, net of current portion</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">13,365</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">8,145</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
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 <br class="Apple-interchange-newline" /></div><span></span>
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<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock', window );">Schedule of Future Principal Payments and the Final Payments Due</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 As of March&#xA0;31, 2019, future principal payments and the final
 payment due under the Company&#x2019;s loan agreements were as
 follows:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="68%" align="center" border="0">
 <tr>
 <td width="61%"></td>
 <td valign="bottom" width="5%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="5%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="5%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom">Year Ending December&#xA0;31,</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"><b>Hercules</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"><b>FFG</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"><b>Total</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2019</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1,345</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">2,914</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">4,259</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
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 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2020</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">4,305</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">4,462</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">8,767</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2021</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">4,350</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">2,170</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">6,520</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
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 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Long-term debt</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">
 &#xA0;&#xA0;&#xA0;&#xA0;10,000</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
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 &#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;9,546</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19,546</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
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 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
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 &#xA0;</p>
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 &#xA0;</p>
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 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Tabular disclosure of the combined aggregate amount of maturities and sinking fund requirements for all long-term borrowings for each of the five years following the date of the latest balance sheet date presented.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 470<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6802200&amp;loc=d3e1835-112601<br></p></div>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6836734832">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Leases (Tables)<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LeasesAbstract', window );"><strong>Leases [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LeaseCostTableTextBlock', window );">Schedule of Components of Lease Expense</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The components of lease expense for the three months ended
 March&#xA0;31, 2019 were as follows:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0">
 <tr>
 <td width="72%"></td>
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 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom" nowrap="nowrap"><font style="FONT-SIZE: 10pt"><b>Lease Cost</b></font></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center">
 <b>For&#xA0;the&#xA0;three&#xA0;months&#xA0;ended</b><br />
 <b>March&#xA0;31, 2019</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Fixed operating lease cost</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">187</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Short-term lease costs</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">8</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Total lease expense</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">195</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 <b>Other information</b></p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Cash paid for amounts included in the measurement of lease
 liabilities:</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 5em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Operating cash flows from operating leases</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">201</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Leased assets obtained in exchange for new operating lease
 liabilities&#xA0;(1)</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">781</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Weighted-average remaining lease term&#x2014;operating leases</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">3.9&#xA0;years</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Weighted-average discount rate&#x2014;operating leases</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">9.0</td>
 <td valign="bottom" nowrap="nowrap">%&#xA0;</td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
 <tr style="break-inside: avoid">
 <td valign="top" width="4%" align="left">(1)</td>
 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left">Acquired in Merger with Arsanis</p>
 </td>
 </tr>
 </table>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock', window );">Schedule of Maturities of Lease Liabilities</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 Maturities of lease liabilities due under these lease agreements as
 of March&#xA0;31, 2019 are as follows:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="68%" align="center" border="0">
 <tr>
 <td width="81%"></td>
 <td valign="bottom" width="14%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom" nowrap="nowrap">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; BORDER-BOTTOM: rgb(0,0,0) 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell">
 <b>Maturity of lease liabilities</b></p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Operating&#xA0;Leases</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2019 (remainder of 2019)</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">837</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2020</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,281</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2021</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,304</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2022</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">970</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2023</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">489</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Thereafter</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Total lease payments</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">4,880</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Less: interest</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(764</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Total operating lease liabilities as of March&#xA0;31, 2019</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">4,116</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
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 <br class="Apple-interchange-newline" /></div><span></span>
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<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock', window );">Summary of Future Minimum Lease Payments Due under Operating Leases</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company adopted ASU <font style="WHITE-SPACE: nowrap">2016-02</font> on January&#xA0;1, 2019 as
 noted above, and as required, the following disclosure is provided
 for periods prior to adoption. Future annual minimum lease payments
 due under the Company&#x2019;s operating leases as of
 December&#xA0;31, 2018 were as follows:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="68%" align="center" border="0">
 <tr>
 <td width="81%"></td>
 <td valign="bottom" width="14%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom" nowrap="nowrap">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; BORDER-BOTTOM: #000000 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell">
 <b>Year Ending December&#xA0;31,</b></p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center"><b>Operating&#xA0;Leases</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2019</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">810</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2020</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">823</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2021</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">835</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 2022</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">492</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Total</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">2,960</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 </tr>
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</td>
</tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Tabular disclosure of lessee's lease cost. Includes, but is not limited to, interest expense for finance lease, amortization of right-of-use asset for finance lease, operating lease cost, short-term lease cost, variable lease cost and sublease income.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 4<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918686-209980<br></p></div>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Tabular disclosure of undiscounted cash flows of lessee's operating lease liability. Includes, but is not limited to, reconciliation of undiscounted cash flows to operating lease liability recognized in statement of financial position.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 6<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918701-209980<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Tabular disclosure of future minimum payments required in the aggregate and for each of the five succeeding fiscal years for operating leases having initial or remaining noncancelable lease terms in excess of one year and the total minimum rentals to be received in the future under noncancelable subleases as of the balance sheet date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 840<br> -SubTopic 20<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=77902758&amp;loc=d3e41502-112717<br></p></div>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6691676016">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Preferred and Common Stock Warrants (Tables)<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract', window );"><strong>Derivative Instruments and Hedging Activities Disclosure [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ScheduleOfStockholdersEquityNoteWarrantsOrRightsTextBlock', window );">Schedule of Warrant to Purchase Redeemable Convertible Preferred Stock</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 As of March&#xA0;31, 2019, the Company&#x2019;s outstanding warrants
 to purchase shares of common stock consisted of the following:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="80%" align="center" border="0">
 <tr>
 <td width="60%"></td>
 <td valign="bottom" width="3%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="3%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="3%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="3%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom" nowrap="nowrap">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; BORDER-BOTTOM: rgb(0,0,0) 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell">
 <b>Issuance Date</b></p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Number&#xA0;of</b><br />
 <b>Shares of</b><br />
 <b>Common</b><br />
 <b>Stock&#xA0;Issuable</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Exercise</b><br />
 <b>Price</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Classification</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Expiration&#xA0;Date</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 August&#xA0;14, 2015</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">81,228</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">21.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">August&#xA0;14,&#xA0;2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 August&#xA0;21, 2015</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">69,603</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">21.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">August&#xA0;21, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 October&#xA0;25, 2016</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">5,155</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;24, 2026</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 November&#xA0;1, 2017</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">130,609</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;31,&#xA0;2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 November&#xA0;17, 2017</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">8,442</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">November&#xA0;16, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 December&#xA0;4, 2017</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">5,661</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;3, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 December&#xA0;28, 2017</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">6,925</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;27, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 December&#xA0;28, 2017</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">115,916</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;28, 2027</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 September&#xA0;12, 2018</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">25,275</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">September&#xA0;12,&#xA0;2021</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 September&#xA0;12, 2018</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">20,220</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">September&#xA0;12, 2028</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 October&#xA0;19, 2018</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">20,016</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.78</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;19, 2028</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 December&#xA0;11, 2018</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">5,004</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">19.80</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Equity</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;19, 2028</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">494,054</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 </table>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12px; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 As of December&#xA0;31, 2018, the Company&#x2019;s outstanding
 warrants to purchase shares of preferred stock (which converted
 into warrants to purchase common stock upon close of the Merger)
 consisted of the following (not adjusted for the Reverse Stock
 Split or Exchange Ratio):</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" align="center" border="0">
 <tr>
 <td width="32%"></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="2%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="24" nowrap="nowrap" align="center">
 <p style="MARGIN-BOTTOM: 1pt; FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="center"><b>December&#xA0;31, 2018</b></p>
 </td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 9pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom" nowrap="nowrap">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 9pt; FONT-FAMILY: &quot;Times New Roman&quot;; BORDER-BOTTOM: rgb(0,0,0) 1pt solid; MARGIN-TOP: 0pt; DISPLAY: table-cell">
 <b>Warrant Name</b></p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Issuance Date</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Number&#xA0;of</b><br />
 <b>Shares of</b><br />
 <b>Preferred</b><br />
 <b>Stock&#xA0;Issuable</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Exercise</b><br />
 <b>Price</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Exercisable</b><br />
 <b>for</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Classification</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Expiration Date</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series A warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">August&#xA0;14, 2015</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">854,785</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">2.07</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series&#xA0;A</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">August&#xA0;14, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series A warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">August&#xA0;21, 2015</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">732,453</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">2.07</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series A</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">August&#xA0;21, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 SVB warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;25, 2016</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">54,256</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series A</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;24, 2026</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">November&#xA0;1, 2017</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,374,435</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;31, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">November&#xA0;17, 2017</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">88,845</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">November&#xA0;16, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;4, 2017</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">59,576</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;3, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;28, 2017</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">72,875</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;27, 2020</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;28, 2017</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,219,815</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">December&#xA0;28, 2027</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">September&#xA0;12, 2018</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">265,957</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">September&#xA0;12,&#xA0;2021</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">September&#xA0;12,&#xA0;2018</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">212,765</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">September&#xA0;12, 2028</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B warrants</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;19, 2018</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">210,638</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1.88</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Series B</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">Liability</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">October&#xA0;19, 2028</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">5,146,400</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 </table>
 <br class="Apple-interchange-newline" />

 </div><span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Tabular disclosure of warrants or rights issued. Warrants and rights outstanding are derivative securities that give the holder the right to purchase securities (usually equity) from the issuer at a specific price within a certain time frame. Warrants are often included in a new debt issue to entice investors by a higher return potential. The main difference between warrants and call options is that warrants are issued and guaranteed by the company, whereas options are exchange instruments and are not issued by the company. Also, the lifetime of a warrant is often measured in years, while the lifetime of a typical option is measured in months. Disclose the title of issue of securities called for by warrants and rights outstanding, the aggregate amount of securities called for by warrants and rights outstanding, the date from which the warrants or rights are exercisable, and the price at which the warrant or right is exercisable.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5047-113901<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.4-08(i))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e23780-122690<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 50<br> -Section S99<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6784392&amp;loc=d3e188667-122775<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 50<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=68057994&amp;loc=d3e25284-112666<br></p></div>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6827366640">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Common Stock, Redeemable Common Stock, and Convertible Preferred Stock (Tables)<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FederalHomeLoanBanksAbstract', window );"><strong>Federal Home Loan Banks [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityTableTextBlock', window );">Preferred Stock</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 12pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 As of March&#xA0;31, 2019, there were no preferred stock
 outstanding. As of December&#xA0;31, 2018, the Preferred Stock
 consisted of the following:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" align="center" border="0">
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 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="18" align="center"><b>December&#xA0;31, 2018</b></td>
 <td valign="bottom">&#xA0;</td>
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 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Preferred</b><br />
 <b>Stock</b><br />
 <b>Designated</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Preferred</b><br />
 <b>Stock</b><br />
 <b>Issued and</b><br />
 <b>Outstanding</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Carrying</b><br />
 <b>Value</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Liquidation</b><br />
 <b>Preference</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Common<br />
 Stock</b><br />
 <b>Issuable<br />
 Upon</b><br />
 <b>Conversion(1)</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series Seed preferred stock</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">2,313,523</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,516,136</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1,310</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">1,444</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">143,630</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series A preferred stock</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">22,000,000</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">19,946,862</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">32,480</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">47,624</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,895,610</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Series B preferred stock</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">25,100,000</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">18,616,569</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">30,885</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">34,999</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,769,190</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
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 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
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 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">49,413,523</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">40,079,567</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">64,675</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">84,067</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">3,808,430</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 &#xA0;</p>
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 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="100%" border="0">
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 <td valign="top" align="left">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-TOP: 0pt" align="left">Adjusted to reflect Reverse Stock Split and Exchange
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Tabular disclosure of temporary equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (27)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 480<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=65877616&amp;loc=d3e177068-122764<br></p></div>
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<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquityTableTextBlock</td>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6796418736">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Stock-Based Compensation (Tables)<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract', window );"><strong>Disclosure of Compensation Related Costs, Share-based Payments [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ScheduleOfShareBasedPaymentAwardEmployeeStockPurchasePlanValuationAssumptionsTableTextBlock', window );">Stock Option Valuation</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The following table presents, on a weighted average basis, the
 assumptions used in the Black-Scholes option-pricing model to
 determine the grant-date fair value of stock options granted to
 employees, directors and <font style="WHITE-SPACE: nowrap">non-</font> employees:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; MARGIN-TOP: 0pt">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="76%" align="center" border="0">
 <tr>
 <td width="80%"></td>
 <td valign="bottom" width="7%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="7%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="6" align="center"><b>Three Months Ended<br />
 March&#xA0;31,</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;2019&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td style="BORDER-BOTTOM: #000000 1pt solid" valign="bottom" colspan="2" align="center">
 <b>&#xA0;&#xA0;&#xA0;&#xA0;2018&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Risk-free interest rate</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">2.4</td>
 <td valign="bottom" nowrap="nowrap">%&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">2.8</td>
 <td valign="bottom" nowrap="nowrap">%&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Expected term (in years)</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">5.90</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">5.94</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Expected volatility</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">90.6</td>
 <td valign="bottom" nowrap="nowrap">%&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">86.0</td>
 <td valign="bottom" nowrap="nowrap">%&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Expected dividend yield</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">0</td>
 <td valign="bottom" nowrap="nowrap">%&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">0</td>
 <td valign="bottom" nowrap="nowrap">%&#xA0;</td>
 </tr>
 </table>
 </div><span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock', window );">Summary of Stock Option Activity</a></td>
<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 6pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 The following table summarizes the Company&#x2019;s stock option
 activity since December&#xA0;31, 2018:</p>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 12pt; FONT-FAMILY: &quot;Times New Roman&quot;; WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; FONT-WEIGHT: 400; COLOR: rgb(0,0,0); FONT-STYLE: normal; ORPHANS: 2; WIDOWS: 2; MARGIN-TOP: 0pt; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial; font-variant-ligatures: normal; font-variant-caps: normal">
 &#xA0;</p>
 <table style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; WORD-SPACING: 0px; BORDER-COLLAPSE: collapse; TEXT-TRANSFORM: none; ORPHANS: 2; WIDOWS: 2; LETTER-SPACING: normal; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial" cellspacing="0" cellpadding="0" width="92%" align="center" border="0">
 <tr>
 <td width="61%"></td>
 <td valign="bottom" width="5%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="5%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="5%"></td>
 <td></td>
 <td></td>
 <td></td>
 <td valign="bottom" width="5%"></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Number&#xA0;of</b><br />
 <b>Shares</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Weighted</b><br />
 <b>Average</b><br />
 <b>Exercise</b><br />
 <b>Price</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Weighted</b><br />
 <b>Average</b><br />
 <b>Contractual</b><br />
 <b>Term&#xA0;(Years)</b></td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td style="BORDER-BOTTOM: rgb(0,0,0) 1pt solid" valign="bottom" colspan="2" align="center"><b>Aggregate</b><br />
 <b>Intrinsic</b><br />
 <b>Value</b></td>
 <td valign="bottom">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Outstanding as of December&#xA0;31, 2018</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">797,931</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">8.29</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">8.42</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">6,486</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Assumed as part of Merger with Arsanis</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">271,230</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">
 &#xA0;&#xA0;&#xA0;&#xA0;62.60</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Granted</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">136,913</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">17.22</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Exercised</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(16,483</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">6.85</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 3em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Forfeited</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">(22,378</td>
 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">8.43</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Outstanding as of March&#xA0;31, 2019</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,167,213</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">21.97</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="center">7.65</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">7,168</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid" bgcolor="#CCEEFF">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Exercisable as of March&#xA0;31, 2019</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">556,774</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
 <td valign="bottom" align="right">30.13</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Vested and expected to vest as of March&#xA0;31, 2019</p>
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 <td valign="bottom">&#xA0;&#xA0;</td>
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 &#xA0;</p>
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 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
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 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
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 &#xA0;</p>
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 Stock-based compensation expense was classified in the consolidated
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 &#xA0;</p>
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 <b>&#xA0;&#xA0;&#xA0;&#xA0;2019&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
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 <b>&#xA0;&#xA0;&#xA0;&#xA0;2018&#xA0;&#xA0;&#xA0;&#xA0;</b></td>
 <td valign="bottom">&#xA0;</td>
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 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Research and development expense</p>
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 General and administrative expense</p>
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 <td valign="bottom">&#xA0;&#xA0;</td>
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 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 &#xA0;</p>
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 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 Total stock-based compensation</p>
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 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">262</td>
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 &#xA0;</p>
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 &#xA0;</p>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Tabular disclosure of the significant assumptions used during the year to estimate the fair value of employee stock purchase plans, including, but not limited to: (a) expected term, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions.</p></div>
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 &#xA0;</p>
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 <td valign="bottom">&#xA0;</td>
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 Numerator:</p>
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 <td valign="bottom"></td>
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 Accruing dividends on Series A convertible preferred stock</p>
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 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 Net loss attributable to common stockholders</p>
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 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">$</td>
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 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
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 <td valign="bottom"></td>
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 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <td>&#xA0;</td>
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 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: rgb(0,0,0) 3px double; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
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 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 <td valign="bottom"></td>
 </tr>
 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; break-inside: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: &quot;Times New Roman&quot;; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Weighted average common shares outstanding&#x2014;basic and
 diluted</p>
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 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
 <td valign="bottom" align="right">1,717,808</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
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 Net loss per share attributable to common stockholders&#x2014;basic
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 <td valign="bottom">$</td>
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 <td valign="bottom" nowrap="nowrap">)&#xA0;</td>
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 <td valign="bottom">$</td>
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 <br class="Apple-interchange-newline" />

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<td class="text"><div>
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-TOP: 12pt">
 The Company excluded the following potential common shares,
 presented based on amounts outstanding at each period end and
 adjusted for the Exchange Ratio and Reverse Stock Split, from the
 computation of diluted net loss per share attributable to common
 stockholders for the periods indicated because including them would
 have had an anti-dilutive effect:</p>
 <p style="MARGIN-BOTTOM: 0px; FONT-SIZE: 1px; MARGIN-TOP: 12px">
 &#xA0;</p>
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 <td valign="bottom" width="3%"></td>
 <td></td>
 <td></td>
 <td></td>
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 <tr style="FONT-SIZE: 8pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
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 March&#xA0;31,</b></td>
 <td valign="bottom">&#xA0;</td>
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 Options to purchase common stock</p>
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 <td valign="bottom">&#xA0;&#xA0;</td>
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 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="top">
 <p style="MARGIN-BOTTOM: 0pt; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; MARGIN-LEFT: 1em; MARGIN-TOP: 0pt; TEXT-INDENT: -1em">
 Convertible preferred stock (as converted to common stock)</p>
 </td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom" nowrap="nowrap" align="right">
 &#x2014;&#xA0;&#xA0;</td>
 <td valign="bottom" nowrap="nowrap">&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
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 Warrants to purchase common stock (presented on an <font style="WHITE-SPACE: nowrap">as-converted,</font> as exchanged,
 split-adjusted basis.</p>
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 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
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 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
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 <tr style="FONT-SIZE: 1px">
 <td valign="bottom"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
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 <td>&#xA0;</td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
 <td valign="bottom">
 <p style="MARGIN-BOTTOM: 0pt; BORDER-TOP: #000000 1px solid; MARGIN-TOP: 0pt">
 &#xA0;</p>
 </td>
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 <tr style="FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman; PAGE-BREAK-INSIDE: avoid">
 <td valign="top"></td>
 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
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 <td valign="bottom">&#xA0;&#xA0;</td>
 <td valign="bottom">&#xA0;</td>
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 <td valign="bottom"></td>
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 &#xA0;</p>
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 &#xA0;</p>
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 &#xA0;</p>
 </td>
 <td valign="bottom">
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 &#xA0;</p>
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 <td>&#xA0;</td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Tabular disclosure of securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) in the future that were not included in the computation of diluted EPS because to do so would increase EPS amounts or decrease loss per share amounts for the period presented, by antidilutive securities.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 260<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=6371337&amp;loc=d3e3550-109257<br></p></div>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Tabular disclosure of an entity's basic and diluted earnings per share calculations, including a reconciliation of numerators and denominators of the basic and diluted per-share computations for income from continuing operations.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 260<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6371337&amp;loc=d3e3550-109257<br></p></div>
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<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Nature of the Business and Basis of Presentation - Additional Information (Detail)<br> $ in Millions</strong></div></th>
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<th class="th" colspan="1">3 Months Ended</th>
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<td class="text">&#160;<span></span>
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<td class="text">&#160;<span></span>
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<td class="text">&#160;<span></span>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Percentage of voting equity interests acquired at the acquisition date in the business combination.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=79982066&amp;loc=d3e1392-128463<br></p></div>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Business Combination Share Exchange Ratio1</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_BusinessCombinationShareExchangeRatio1</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Net Proceeds From Issuance Of Common Stock And Warrants</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_NetProceedsFromIssuanceOfCommonStockAndWarrants</td>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Schedule Of Accounting Policies [Line Items]</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ScheduleOfAccountingPoliciesLineItems</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember</td>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6837371472">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
<th class="th" colspan="1"></th>
<th class="th" colspan="1"></th>
<th class="th" colspan="1"></th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Mar. 13, 2019</div></th>
<th class="th"><div>Jan. 01, 2019</div></th>
<th class="th"><div>Dec. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems', window );"><strong>Restricted Cash and Cash Equivalents Items [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RestrictedCashNoncurrent', window );">Restricted cash - non-current</a></td>
<td class="nump">$ 947<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 364<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DerivativeFairValueOfDerivativeLiability', window );">Fair value of derivative liability</a></td>
<td class="nump">0<span></span>
</td>
<td class="nump">$ 5,235<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax', window );">Comprehensive loss included of foreign currency translation gain adjustments</a></td>
<td class="nump">23<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseLiability', window );">Operating lease liabilities</a></td>
<td class="nump">4,116<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseRightOfUseAsset', window );">Right-of-use assets</a></td>
<td class="nump">2,705<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_UnderlyingAssetClassAxis=us-gaap_CollateralizedCreditCardSecuritiesMember', window );">Collateralized Credit Card Securities [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems', window );"><strong>Restricted Cash and Cash Equivalents Items [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RestrictedCashNoncurrent', window );">Restricted cash - non-current</a></td>
<td class="nump">150<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201602Member', window );">Accounting Standards Update 2016-02 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems', window );"><strong>Restricted Cash and Cash Equivalents Items [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseLiability', window );">Operating lease liabilities</a></td>
<td class="nump">2,538<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 2,538<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseRightOfUseAsset', window );">Right-of-use assets</a></td>
<td class="nump">2,026<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 2,026<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis=xfor_OfficeLeasesMember', window );">Company's Office Leases</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems', window );"><strong>Restricted Cash and Cash Equivalents Items [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RestrictedCashNoncurrent', window );">Restricted cash - non-current</a></td>
<td class="nump">$ 250<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LeaseExpirationDate1', window );">Lease expiration date</a></td>
<td class="text">Dec. 31,  2023<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis=xfor_OfficeLeasesMember', window );">Company's Office Leases | Waltham Lease [Member] | Arsanis [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems', window );"><strong>Restricted Cash and Cash Equivalents Items [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RestrictedCashNoncurrent', window );">Restricted cash - non-current</a></td>
<td class="nump">$ 283<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember', window );">Letter of Credit [Member] | Cambridge Lease Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems', window );"><strong>Restricted Cash and Cash Equivalents Items [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RestrictedCashNoncurrent', window );">Restricted cash - non-current</a></td>
<td class="nump">$ 264<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 264<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DerivativeFairValueOfDerivativeLiability">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 860<br> -SubTopic 20<br> -Section 50<br> -Paragraph 4D<br> -Subparagraph (c)(2)<br> -URI http://asc.fasb.org/extlink&amp;oid=109247956&amp;loc=SL51823488-111719<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 815<br> -SubTopic 10<br> -Section 50<br> -Paragraph 4B<br> -Subparagraph (a),(c)<br> -URI http://asc.fasb.org/extlink&amp;oid=109980867&amp;loc=SL5624163-113959<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 20<br> -Section 50<br> -Paragraph 3<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=51824906&amp;loc=SL20225862-175312<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 20<br> -Section 55<br> -Paragraph 7<br> -URI http://asc.fasb.org/extlink&amp;oid=99393222&amp;loc=SL20226000-175313<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DerivativeFairValueOfDerivativeLiability</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LeaseExpirationDate1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Date which lease or group of leases is set to expire, in CCYY-MM-DD format.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LeaseExpirationDate1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:dateItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeaseLiability">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Present value of lessee's discounted obligation for lease payments from operating lease.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 45<br> -Paragraph 1<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888419&amp;loc=SL77918627-209977<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeaseLiability</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeaseRightOfUseAsset">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of lessee's right to use underlying asset under operating lease.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 45<br> -Paragraph 1<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888419&amp;loc=SL77918627-209977<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeaseRightOfUseAsset</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of tax expense (benefit), after reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 12<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=d3e640-108580<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 10A<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669646-108580<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_RestrictedCashNoncurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of cash restricted as to withdrawal or usage, classified as noncurrent. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section 45<br> -Paragraph 4<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=82887183&amp;loc=d3e6812-107765<br><br>Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(17))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 50<br> -Paragraph 8<br> -URI http://asc.fasb.org/extlink&amp;oid=98513485&amp;loc=SL98516268-108586<br><br>Reference 4: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 954<br> -SubTopic 305<br> -Section 45<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=84242212&amp;loc=d3e2352-115587<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_RestrictedCashNoncurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_UnderlyingAssetClassAxis=us-gaap_CollateralizedCreditCardSecuritiesMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_UnderlyingAssetClassAxis=us-gaap_CollateralizedCreditCardSecuritiesMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201602Member">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201602Member</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis=xfor_OfficeLeasesMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis=xfor_OfficeLeasesMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LeaseArrangementTypeAxis=xfor_WalthamLeaseAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LeaseArrangementTypeAxis=xfor_WalthamLeaseAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LeaseArrangementTypeAxis=xfor_CambridgeMAOperatingLeaseAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LeaseArrangementTypeAxis=xfor_CambridgeMAOperatingLeaseAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
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<head>
<title></title>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6837035040">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Summary of Significant Accounting Policies - Schedule of Property and Equipment (Detail)<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th"><div>Mar. 31, 2019</div></th></tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_FurnitureAndFixturesMember', window );">Furniture and Fixtures [Member]</a></td>
<td class="text">&#160;<span></span>
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</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentUsefulLife', window );">Estimated useful life</a></td>
<td class="text">3 years<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_ComputerEquipmentMember', window );">Computer Equipment [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentUsefulLife', window );">Estimated useful life</a></td>
<td class="text">3 years<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_SoftwareDevelopmentMember', window );">Software Development [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentUsefulLife', window );">Estimated useful life</a></td>
<td class="text">3 years<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_EquipmentMember', window );">Laboratory Equipment [Member] | Minimum [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentUsefulLife', window );">Estimated useful life</a></td>
<td class="text">3 years<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_EquipmentMember', window );">Laboratory Equipment [Member] | Maximum [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentUsefulLife', window );">Estimated useful life</a></td>
<td class="text">10 years<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_LeaseholdImprovementsMember', window );">Leasehold Improvements [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentUsefulLife', window );">Estimated useful life</a></td>
<td class="text">10 years<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives', window );">Estimated useful life</a></td>
<td class="text">Shorter of lease term or 10 years<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Describes the periods of time over which an entity anticipates to receive utility from its property, plant and equipment (that is, the periods of time over which an entity allocates the initial cost of its property, plant and equipment).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 360<br> -SubTopic 10<br> -Section 35<br> -Paragraph 4<br> -URI http://asc.fasb.org/extlink&amp;oid=68071081&amp;loc=d3e1205-110223<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=84158767&amp;loc=d3e18780-107790<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_PropertyPlantAndEquipmentUsefulLife">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PropertyPlantAndEquipmentUsefulLife</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<td><strong> Data Type:</strong></td>
<td>xbrli:durationItemType</td>
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<td><strong> Balance Type:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_FurnitureAndFixturesMember</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_ComputerEquipmentMember</td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_SoftwareDevelopmentMember</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_EquipmentMember</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
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<td style="white-space:nowrap;">srt_RangeAxis=srt_MinimumMember</td>
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<td><strong> Name:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6838807072">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Merger Accounting - Additional Information (Detail)<br> shares in Thousands, $ in Thousands</strong></div></th>
<th class="th" colspan="2">3 Months Ended</th>
<th class="th" colspan="1"></th>
</tr>
<tr>
<th class="th">
<div>Mar. 31, 2019 </div>
<div>USD ($) </div>
<div>shares</div>
</th>
<th class="th">
<div>Mar. 31, 2018 </div>
<div>USD ($)</div>
</th>
<th class="th"><div>Mar. 13, 2019</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionLineItems', window );"><strong>Business Acquisition [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired', window );">Business acquisition, equity interest</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">63.70%<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_Goodwill', window );">Good will</a></td>
<td class="nump">$ 27,407<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessCombinationAcquisitionRelatedCosts', window );">Business combination, acquisition related costs</a></td>
<td class="nump">1,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementScenarioAxis=us-gaap_ProFormaMember', window );">Pro Forma [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionLineItems', window );"><strong>Business Acquisition [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessCombinationAcquisitionRelatedCosts', window );">Business combination, acquisition related costs</a></td>
<td class="nump">$ 2,700<span></span>
</td>
<td class="nump">$ 2,700<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_srt_OwnershipAxis=xfor_ArsanisSecurityHoldersMember', window );">Arsanis Security Holders [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionLineItems', window );"><strong>Business Acquisition [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired', window );">Business acquisition, equity interest</a></td>
<td class="nump">31.30%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_srt_OwnershipAxis=xfor_XfourSecurityHoldersMember', window );">XFour Security Holders [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionLineItems', window );"><strong>Business Acquisition [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired', window );">Business acquisition, equity interest</a></td>
<td class="nump">68.70%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
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<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember', window );">Arsanis [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionLineItems', window );"><strong>Business Acquisition [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_BusinessCombinationShareExchangeRatio1', window );">Business acquisition share exchange ratio</a></td>
<td class="nump">0.5702<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights', window );">Business combination warrants to purchase of common stock | shares</a></td>
<td class="nump">271,230<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
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<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_Goodwill', window );">Good will</a></td>
<td class="nump">$ 27,407<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessAcquisitionLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessAcquisitionLineItems</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Percentage of voting equity interests acquired at the acquisition date in the business combination.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=79982066&amp;loc=d3e1392-128463<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired</td>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 10<br> -Section 25<br> -Paragraph 23<br> -URI http://asc.fasb.org/extlink&amp;oid=84229725&amp;loc=d3e1043-128460<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<td><strong> Balance Type:</strong></td>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.4-08.(i)(2))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e23780-122690<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 350<br> -SubTopic 20<br> -Section 45<br> -Paragraph 5<br> -URI http://asc.fasb.org/extlink&amp;oid=77989000&amp;loc=SL49117168-202975<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 350<br> -SubTopic 20<br> -Section 45<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=99380562&amp;loc=d3e13770-109266<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Business Combination Share Exchange Ratio1</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6839033664">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Merger Accounting - Schedule of Business Acquisitions by Acquisition, Contingent Consideration (Detail)<br> $ / shares in Units, $ in Thousands</strong></div></th>
<th class="th" colspan="2">3 Months Ended</th>
</tr>
<tr><th class="th" colspan="2">
<div>Mar. 31, 2019 </div>
<div>USD ($) </div>
<div>$ / shares </div>
<div>shares</div>
</th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_AcquisitionDateLineItems', window );"><strong>Acquisition Date [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
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<td class="fn" style="border-bottom: 0px;"></td>
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<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodValueAcquisitions', window );">Fair value of consideration issued it effect the Merger</a></td>
<td class="nump">$ 45,541<span></span>
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<td class="fn" style="border-bottom: 0px;"></td>
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<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember', window );">Arsanis [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="fn" style="border-bottom: 0px;"></td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_AcquisitionDateLineItems', window );"><strong>Acquisition Date [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="fn" style="border-bottom: 0px;"></td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits', window );">Number of shares of the combined organization owned by Arsanis stockholders | shares</a></td>
<td class="nump">2,440,582<span></span>
</td>
<td class="fn" style="border-bottom: 0px;"><sup>[1]</sup></td>
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<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_FairValueOfCommonStockPerShare', window );">Multiplied by the fair value per share of Arsanis common stock | $ / shares</a></td>
<td class="nump">$ 18.66<span></span>
</td>
<td class="fn" style="border-bottom: 0px;"><sup>[2]</sup></td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodValueAcquisitions', window );">Fair value of consideration issued it effect the Merger</a></td>
<td class="nump">$ 45,541<span></span>
</td>
<td class="fn" style="border-bottom: 0px;"></td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_FairValueOfReplacementEquityAwards', window );">Fair value of replacement awards held by former employees, board of directors and consultants of Arsanis that were vested as of the Merger.</a></td>
<td class="nump">817<span></span>
</td>
<td class="fn" style="border-bottom: 0px;"></td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessCombinationConsiderationTransferred1', window );">Purchase price:</a></td>
<td class="nump">$ 46,358<span></span>
</td>
<td class="fn" style="border-bottom: 0px;"></td>
</tr>
<tr><td colspan="3"></td></tr>
<tr><td colspan="3"><table class="outerFootnotes" width="100%">
<tr class="outerFootnote">
<td style="vertical-align: top; width: 12pt;" valign="top">[1]</td>
<td style="vertical-align: top;" valign="top">The number of shares of 2,440,582 represents the historical 14,643,737 shares of Arsanis common stock outstanding immediately prior to the closing of the Merger, adjusted for the Reverse Stock Split.</td>
</tr>
<tr class="outerFootnote">
<td style="vertical-align: top; width: 12pt;" valign="top">[2]</td>
<td style="vertical-align: top;" valign="top">Based on the last reported sale price of Arsanis common stock on the Nasdaq Global Market on March 13, 2019, the closing date of the Merger, and gives effect to the Reverse Stock Split.</td>
</tr>
</table></td></tr>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 30<br> -Section 30<br> -Paragraph 8<br> -URI http://asc.fasb.org/extlink&amp;oid=109124213&amp;loc=d3e6613-128477<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 30<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=35744584&amp;loc=d3e6927-128479<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 30<br> -Section 30<br> -Paragraph 7<br> -URI http://asc.fasb.org/extlink&amp;oid=109124213&amp;loc=d3e6578-128477<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Reduction in the number of shares during the period as a result of a reverse stock split.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21463-112644<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Value of stock issued pursuant to acquisitions during the period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21463-112644<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.29-31)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockIssuedDuringPeriodValueAcquisitions</td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Acquisition Date [Line Items]</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_FairValueOfCommonStockPerShare">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Fair value of common stock per share.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_FairValueOfCommonStockPerShare</td>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Fair Value of replacement equity awards.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_FairValueOfReplacementEquityAwards</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember</td>
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<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<head>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6632382048">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Merger Accounting - Schedule of Business Acquisitions by Acquisition, Contingent Consideration (Parenthetical) (Detail)<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th">
<div>Mar. 31, 2019 </div>
<div>shares</div>
</th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_AcquisitionDateLineItems', window );"><strong>Acquisition Date [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued', window );">Stock issued during period, shares, reverse stock splits</a></td>
<td class="nump">2,440,582<span></span>
</td>
</tr>
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<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember', window );">Arsanis [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_AcquisitionDateLineItems', window );"><strong>Acquisition Date [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued', window );">Stock issued during period, shares, reverse stock splits</a></td>
<td class="nump">14,643,737<span></span>
</td>
</tr>
</table>
<div style="display: none;">
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of shares of equity interests issued or issuable to acquire entity.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 30<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (b)(4)<br> -URI http://asc.fasb.org/extlink&amp;oid=35744584&amp;loc=d3e6927-128479<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued</td>
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<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
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<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
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<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_AcquisitionDateLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Acquisition Date [Line Items]</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_AcquisitionDateLineItems</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
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<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
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<html>
<head>
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<link rel="stylesheet" type="text/css" href="report.css">
<script type="text/javascript" src="Show.js">/* Do Not Remove This Comment */</script><script type="text/javascript">
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<body>
<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6824707760">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Merger Accounting - Schedule of Recognized Identified Assets Acquired and Liabilities Assumed (Detail)<br> $ in Thousands</strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th">
<div>Mar. 31, 2019 </div>
<div>USD ($)</div>
</th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_AcquisitionDateLineItems', window );"><strong>Acquisition Date [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_Goodwill', window );">Goodwill</a></td>
<td class="nump">$ 27,407<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember', window );">Arsanis [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_AcquisitionDateLineItems', window );"><strong>Acquisition Date [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRestrictedCashAndCashEquivalents', window );">Cash and cash equivalents and restricted cash</a></td>
<td class="nump">26,406<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther', window );">Other current assets</a></td>
<td class="nump">2,147<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment', window );">Property and equipment, net</a></td>
<td class="nump">68<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles', window );">IPR&amp;D indefinite-lived intangible assets</a></td>
<td class="nump">4,900<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets', window );">Other assets, non-current</a></td>
<td class="nump">879<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities', window );">Current liabilities</a></td>
<td class="num">(5,221)<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt', window );">Loans payable</a></td>
<td class="num">(8,713)<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther', window );">Other liabilities, non-current</a></td>
<td class="num">(1,515)<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_Goodwill', window );">Goodwill</a></td>
<td class="nump">27,407<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessCombinationConsiderationTransferred1', window );">Purchase price</a></td>
<td class="nump">$ 46,358<span></span>
</td>
</tr>
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<div style="display: none;">
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 30<br> -Section 30<br> -Paragraph 8<br> -URI http://asc.fasb.org/extlink&amp;oid=109124213&amp;loc=d3e6613-128477<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 30<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=35744584&amp;loc=d3e6927-128479<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 30<br> -Section 30<br> -Paragraph 7<br> -URI http://asc.fasb.org/extlink&amp;oid=109124213&amp;loc=d3e6578-128477<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessCombinationConsiderationTransferred1</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Balance Type:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of other assets expected to be realized or consumed before one year or the normal operating cycle, if longer, acquired at the acquisition date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 20<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=84161108&amp;loc=d3e4845-128472<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther</td>
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<td><strong> Period Type:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of liabilities due within one year or within the normal operating cycle, if longer, assumed at the acquisition date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 20<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=84161108&amp;loc=d3e4845-128472<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities</td>
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<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
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<td><strong> Balance Type:</strong></td>
<td>credit</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
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</table></div>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The amount of identifiable intangible assets recognized as of the acquisition date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 10<br> -Section 55<br> -Paragraph 37<br> -URI http://asc.fasb.org/extlink&amp;oid=108330185&amp;loc=d3e2207-128464<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 20<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=84161108&amp;loc=d3e4845-128472<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
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<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
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<td><strong> Period Type:</strong></td>
<td>instant</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of long-term debt due after one year or the normal operating cycle, if longer, assumed at the acquisition date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 20<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=84161108&amp;loc=d3e4845-128472<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
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<td><strong> Balance Type:</strong></td>
<td>credit</td>
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<td><strong> Period Type:</strong></td>
<td>instant</td>
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</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of other liabilities due after one year or the normal operating cycle, if longer, assumed at the acquisition date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 20<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=84161108&amp;loc=d3e4845-128472<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
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<td><strong> Period Type:</strong></td>
<td>instant</td>
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</table></div>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of other assets expected to be realized or consumed after one year or the normal operating cycle, if longer, acquired at the acquisition date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 20<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=84161108&amp;loc=d3e4845-128472<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets</td>
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<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
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<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
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<td><strong> Period Type:</strong></td>
<td>instant</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The amount of property, plant, and equipment recognized as of the acquisition date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 10<br> -Section 55<br> -Paragraph 37<br> -URI http://asc.fasb.org/extlink&amp;oid=108330185&amp;loc=d3e2207-128464<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 20<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=84161108&amp;loc=d3e4845-128472<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
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<td><strong> Balance Type:</strong></td>
<td>debit</td>
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<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
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</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_Goodwill">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 350<br> -SubTopic 20<br> -Section 45<br> -Paragraph 5<br> -URI http://asc.fasb.org/extlink&amp;oid=77989000&amp;loc=SL49117168-202975<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 350<br> -SubTopic 20<br> -Section 45<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=99380562&amp;loc=d3e13770-109266<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_Goodwill</td>
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<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<td>xbrli:monetaryItemType</td>
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<td><strong> Balance Type:</strong></td>
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<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_AcquisitionDateLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Acquisition Date [Line Items]</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_AcquisitionDateLineItems</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRestrictedCashAndCashEquivalents">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Restricted Cash And Cash Equivalents</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRestrictedCashAndCashEquivalents</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember</td>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6630406848">
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<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Merger Accounting - Business Acquisition, Pro Forma Information (Detail) - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th" colspan="2">3 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Mar. 31, 2018</div></th>
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<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessCombinationsAbstract', window );"><strong>Business Combinations [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
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<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionsProFormaRevenue', window );">Revenue</a></td>
<td class="nump">$ 0<span></span>
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<td class="nump">$ 0<span></span>
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<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss', window );">Net loss</a></td>
<td class="num">$ (16,258)<span></span>
</td>
<td class="num">$ (20,235)<span></span>
</td>
</tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss">
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (h)(3)<br> -URI http://asc.fasb.org/extlink&amp;oid=79982066&amp;loc=d3e1392-128463<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (h)(2)<br> -URI http://asc.fasb.org/extlink&amp;oid=79982066&amp;loc=d3e1392-128463<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessAcquisitionsProFormaRevenue">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (h)(2)<br> -URI http://asc.fasb.org/extlink&amp;oid=79982066&amp;loc=d3e1392-128463<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 805<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (h)(3)<br> -URI http://asc.fasb.org/extlink&amp;oid=79982066&amp;loc=d3e1392-128463<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessAcquisitionsProFormaRevenue</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessCombinationsAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessCombinationsAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
</div>
</body>
</html>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6838463152">
<tr>
<th class="tl" colspan="1" rowspan="1"><div style="width: 200px;"><strong>Fair Value of Financial Assets and Liabilities - Schedule of Assets and Liabilities Measured at Fair Value (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Dec. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract', window );"><strong>Assets:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CashAndCashEquivalentsFairValueDisclosure', window );">Cash equivalents</a></td>
<td class="nump">$ 22,299<span></span>
</td>
<td class="nump">$ 8,134<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract', window );"><strong>Liabilities:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesFairValueDisclosure', window );">Derivative liability</a></td>
<td class="nump">18<span></span>
</td>
<td class="nump">5,148<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesFairValueDisclosure', window );">Total</a></td>
<td class="nump">18<span></span>
</td>
<td class="nump">5,148<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember', window );">Preferred Stock Warrant Liability [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract', window );"><strong>Liabilities:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesFairValueDisclosure', window );">Derivative liability</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">4,947<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesFairValueDisclosure', window );">Total</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">4,947<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember', window );">Derivative Liability [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract', window );"><strong>Liabilities:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesFairValueDisclosure', window );">Derivative liability</a></td>
<td class="nump">18<span></span>
</td>
<td class="nump">201<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesFairValueDisclosure', window );">Total</a></td>
<td class="nump">18<span></span>
</td>
<td class="nump">201<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember', window );">Money Market Funds [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract', window );"><strong>Assets:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CashAndCashEquivalentsFairValueDisclosure', window );">Cash equivalents</a></td>
<td class="nump">22,299<span></span>
</td>
<td class="nump">8,134<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember', window );">Level 2 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract', window );"><strong>Assets:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CashAndCashEquivalentsFairValueDisclosure', window );">Cash equivalents</a></td>
<td class="nump">22,299<span></span>
</td>
<td class="nump">8,134<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember', window );">Level 2 [Member] | Money Market Funds [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract', window );"><strong>Assets:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CashAndCashEquivalentsFairValueDisclosure', window );">Cash equivalents</a></td>
<td class="nump">22,299<span></span>
</td>
<td class="nump">8,134<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember', window );">Level 3 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract', window );"><strong>Liabilities:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesFairValueDisclosure', window );">Derivative liability</a></td>
<td class="nump">18<span></span>
</td>
<td class="nump">5,148<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesFairValueDisclosure', window );">Total</a></td>
<td class="nump">18<span></span>
</td>
<td class="nump">5,148<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember', window );">Level 3 [Member] | Preferred Stock Warrant Liability [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract', window );"><strong>Liabilities:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesFairValueDisclosure', window );">Derivative liability</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">4,947<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesFairValueDisclosure', window );">Total</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">4,947<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember', window );">Level 3 [Member] | Derivative Liability [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract', window );"><strong>Liabilities:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesFairValueDisclosure', window );">Derivative liability</a></td>
<td class="nump">18<span></span>
</td>
<td class="nump">201<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LiabilitiesFairValueDisclosure', window );">Total</a></td>
<td class="nump">$ 18<span></span>
</td>
<td class="nump">$ 201<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CashAndCashEquivalentsFairValueDisclosure">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CashAndCashEquivalentsFairValueDisclosure</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LiabilitiesFairValueDisclosure">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Fair value of financial and nonfinancial obligations.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 820<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=99377789&amp;loc=d3e19207-110258<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LiabilitiesFairValueDisclosure</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_FairValueByLiabilityClassAxis=xfor_PreferredStockWarrantLiabilityMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FairValueByLiabilityClassAxis=xfor_PreferredStockWarrantLiabilityMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_FairValueByLiabilityClassAxis=us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FairValueByLiabilityClassAxis=us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
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<td><strong> Data Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Balance Type:</strong></td>
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<tr>
<td><strong> Period Type:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CashAndCashEquivalentsAxis=us-gaap_MoneyMarketFundsMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
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<tr>
<td><strong> Period Type:</strong></td>
<td></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member</td>
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<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
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<td><strong> Data Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
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<td></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member</td>
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<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
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<DESCRIPTION>IDEA: XBRL DOCUMENT
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<head>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6824898464">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Fair Value of Financial Assets and Liabilities - Additional Information (Detail) - USD ($)<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
<th class="th" colspan="1">12 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Dec. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_FairValueTransfersBetweenLevel1Level2OrLevel3Amount', window );">Transfers between fair value levels</a></td>
<td class="nump">$ 0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputExpectedDividendRateMember', window );">Measurement Input, Expected Dividend Rate [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PreferredStockDividendRatePercentage', window );">Expected dividend yield</a></td>
<td class="nump">0.00%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_GenzymeAgreementMember', window );">Genzyme Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DerivativeLiabilities', window );">Fair value of derivative liability</a></td>
<td class="nump">$ 0<span></span>
</td>
<td class="nump">$ 183,000<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember', window );">Arsanis [Member] | Genzyme Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DerivativeLiabilities', window );">Fair value of derivative liability</a></td>
<td class="nump">$ 0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesAConvertiblePreferredStockMember', window );">Series A Convertible Preferred Stock [Member] | Arsanis And Merger Sub [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_PreferredStockFairValuePerShare', window );">Preferred stock Fair value per share</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 1.70<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesBConvertiblePreferredStockMember', window );">Series B Convertible Preferred Stock [Member] | Arsanis And Merger Sub [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_PreferredStockFairValuePerShare', window );">Preferred stock Fair value per share</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 1.86<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=us-gaap_ConvertiblePreferredStockMember', window );">Convertible Preferred Stock [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight', window );">Number of warrants for purchase of convertible preferred shares</a></td>
<td class="nump">0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of securities into which each warrant or right may be converted. For example, but not limited to, each warrant may be converted into two shares.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DerivativeLiabilities">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 20<br> -Section 50<br> -Paragraph 3<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=51824906&amp;loc=SL20225862-175312<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 825<br> -SubTopic 10<br> -Section 50<br> -Paragraph 10<br> -URI http://asc.fasb.org/extlink&amp;oid=109250915&amp;loc=d3e13433-108611<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 20<br> -Section 55<br> -Paragraph 10<br> -URI http://asc.fasb.org/extlink&amp;oid=99393222&amp;loc=SL20226008-175313<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DerivativeLiabilities</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_PreferredStockDividendRatePercentage">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The percentage rate used to calculate dividend payments on preferred stock.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PreferredStockDividendRatePercentage</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_FairValueTransfersBetweenLevel1Level2OrLevel3Amount">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Fair value transfers between Level 1, Level 2 and Level 3 amount.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_FairValueTransfersBetweenLevel1Level2OrLevel3Amount</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_PreferredStockFairValuePerShare">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Preferred stock fair value per share.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_PreferredStockFairValuePerShare</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputExpectedDividendRateMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputExpectedDividendRateMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
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<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TypeOfArrangementAxis=xfor_GenzymeAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TypeOfArrangementAxis=xfor_GenzymeAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td>na</td>
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<tr>
<td><strong> Balance Type:</strong></td>
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<tr>
<td><strong> Period Type:</strong></td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
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<td><strong> Data Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
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<tr>
<td><strong> Period Type:</strong></td>
<td></td>
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</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesAConvertiblePreferredStockMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementClassOfStockAxis=xfor_SeriesAConvertiblePreferredStockMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
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</table></div>
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</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessAcquisitionAxis=xfor_ArsanisAndMergerSubMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessAcquisitionAxis=xfor_ArsanisAndMergerSubMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesBConvertiblePreferredStockMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementClassOfStockAxis=xfor_SeriesBConvertiblePreferredStockMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StatementClassOfStockAxis=us-gaap_ConvertiblePreferredStockMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementClassOfStockAxis=us-gaap_ConvertiblePreferredStockMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
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<DOCUMENT>
<TYPE>XML
<SEQUENCE>63
<FILENAME>R47.htm
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
<script type="text/javascript" src="Show.js">/* Do Not Remove This Comment */</script><script type="text/javascript">
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6825009952">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Fair Value of Financial Assets and Liabilities - Summary of Aggregate Fair Values of Warrant Liability and Derivative Liability and Preferred Stock Repurchase Liability (Detail) - Level 3 [Member]<br> $ in Thousands</strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr><th class="th">
<div>Mar. 31, 2019 </div>
<div>USD ($)</div>
</th></tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueByLiabilityClassAxis=xfor_PreferredStockWarrantLiabilityMember', window );">Preferred Stock Warrant Liability [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_FairValueAssetsMeasuredOnRecurringAndNonrecurringBasisLineItems', window );"><strong>Fair Value Assets Measured On Recurring and Nonrecurring Basis [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue', window );">Balance as of December 31, 2018</a></td>
<td class="nump">$ 4,947<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPeriodIncreaseDecrease', window );">Change in fair value</a></td>
<td class="nump">288<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_FairValueMeasurementWithUnobservableInputsConversionOfConvertiblePreferredStockWarrantsIntoCommonStockWarrantsInConnectionWithMerger', window );">Conversion of convertible preferred stock warrant into common stock warrant in connection with Merger</a></td>
<td class="num">(5,235)<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue', window );">Balance as of March 31, 2019</a></td>
<td class="nump">0<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueByLiabilityClassAxis=us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember', window );">Derivative Liability [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_FairValueAssetsMeasuredOnRecurringAndNonrecurringBasisLineItems', window );"><strong>Fair Value Assets Measured On Recurring and Nonrecurring Basis [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue', window );">Balance as of December 31, 2018</a></td>
<td class="nump">201<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPeriodIncreaseDecrease', window );">Change in fair value</a></td>
<td class="num">(183)<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue', window );">Balance as of March 31, 2019</a></td>
<td class="nump">$ 18<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPeriodIncreaseDecrease">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of increase (decrease) of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 820<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=99377789&amp;loc=d3e19207-110258<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPeriodIncreaseDecrease</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 820<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=99377789&amp;loc=d3e19207-110258<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_FairValueAssetsMeasuredOnRecurringAndNonrecurringBasisLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Fair Value Assets Measured On Recurring and Nonrecurring Basis [Line Items]</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_FairValueAssetsMeasuredOnRecurringAndNonrecurringBasisLineItems</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
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<tr>
<td><strong> Data Type:</strong></td>
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<tr>
<td><strong> Balance Type:</strong></td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
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</table></div>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_FairValueMeasurementWithUnobservableInputsConversionOfConvertiblePreferredStockWarrantsIntoCommonStockWarrantsInConnectionWithMerger">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Fair value measurement with unobservable inputs conversion of convertible preferred stock warrants into common stock warrants in connection with merger.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_FairValueMeasurementWithUnobservableInputsConversionOfConvertiblePreferredStockWarrantsIntoCommonStockWarrantsInConnectionWithMerger</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_FairValueByLiabilityClassAxis=xfor_PreferredStockWarrantLiabilityMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FairValueByLiabilityClassAxis=xfor_PreferredStockWarrantLiabilityMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
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<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
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<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_FairValueByLiabilityClassAxis=us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FairValueByLiabilityClassAxis=us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
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<tr>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6824070992">
<tr>
<th class="tl" colspan="1" rowspan="1"><div style="width: 200px;"><strong>Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail) - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Dec. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentLineItems', window );"><strong>Property, Plant and Equipment [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentGross', window );">Property and Equipment, Gross</a></td>
<td class="nump">$ 448<span></span>
</td>
<td class="nump">$ 417<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment', window );">Less: Accumulated depreciation and amortization</a></td>
<td class="num">(177)<span></span>
</td>
<td class="num">(176)<span></span>
</td>
</tr>
<tr class="rou">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentNet', window );">Property and Equipment, Net</a></td>
<td class="nump">271<span></span>
</td>
<td class="nump">241<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_LeaseholdImprovementsMember', window );">Leasehold Improvements [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentLineItems', window );"><strong>Property, Plant and Equipment [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentGross', window );">Property and Equipment, Gross</a></td>
<td class="nump">299<span></span>
</td>
<td class="nump">299<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_FurnitureAndFixturesMember', window );">Furniture and Fixtures [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentLineItems', window );"><strong>Property, Plant and Equipment [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentGross', window );">Property and Equipment, Gross</a></td>
<td class="nump">53<span></span>
</td>
<td class="nump">53<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_ComputerEquipmentMember', window );">Computer Equipment [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentLineItems', window );"><strong>Property, Plant and Equipment [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentGross', window );">Property and Equipment, Gross</a></td>
<td class="nump">19<span></span>
</td>
<td class="nump">56<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentByTypeAxis=xfor_SoftwareMember', window );">Software [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentLineItems', window );"><strong>Property, Plant and Equipment [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentGross', window );">Property and Equipment, Gross</a></td>
<td class="nump">9<span></span>
</td>
<td class="nump">$ 9<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentByTypeAxis=xfor_LabEquipmentMember', window );">Lab Equipment [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
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<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentLineItems', window );"><strong>Property, Plant and Equipment [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentGross', window );">Property and Equipment, Gross</a></td>
<td class="nump">$ 67<span></span>
</td>
<td class="text">&#160;<span></span>
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<div style="display: none;">
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 360<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=6391035&amp;loc=d3e2868-110229<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.14)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment</td>
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<td><strong> Period Type:</strong></td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 360<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=6391035&amp;loc=d3e2868-110229<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.13)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<td><strong> Name:</strong></td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(14))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 360<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6391035&amp;loc=d3e2868-110229<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 944<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.7-03(a)(8))<br> -URI http://asc.fasb.org/extlink&amp;oid=6879938&amp;loc=d3e572229-122910<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(13))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
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<TEXT>
<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
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<body>
<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6815572544">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Property and Equipment, Net - Additional Information (Detail) - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th" colspan="2">3 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Mar. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PropertyPlantAndEquipmentAbstract', window );"><strong>Property, Plant and Equipment [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DepreciationDepletionAndAmortization', window );">Depreciation and amortization expense</a></td>
<td class="nump">$ 20<span></span>
</td>
<td class="nump">$ 26<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DepreciationDepletionAndAmortization">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 280<br> -SubTopic 10<br> -Section 50<br> -Paragraph 22<br> -Subparagraph (e)<br> -URI http://asc.fasb.org/extlink&amp;oid=115929826&amp;loc=d3e8736-108599<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 28<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3602-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DepreciationDepletionAndAmortization</td>
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<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Balance Type:</strong></td>
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<td><strong> Period Type:</strong></td>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PropertyPlantAndEquipmentAbstract</td>
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<head>
<title></title>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6660933536">
<tr>
<th class="tl" colspan="1" rowspan="1"><div style="width: 200px;"><strong>Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Dec. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PayablesAndAccrualsAbstract', window );"><strong>Payables and Accruals [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_EmployeeRelatedLiabilitiesCurrent', window );">Accrued employee compensation and benefits</a></td>
<td class="nump">$ 1,239<span></span>
</td>
<td class="nump">$ 924<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_AccruedExternalResearchAndDevelopmentExpenses', window );">Accrued external research and development expenses</a></td>
<td class="nump">819<span></span>
</td>
<td class="nump">754<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AccruedProfessionalFeesCurrent', window );">Accrued professional fees</a></td>
<td class="nump">1,850<span></span>
</td>
<td class="nump">1,324<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DeferredRentCreditCurrent', window );">Deferred rent, current portion</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">93<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OtherAccruedLiabilitiesCurrent', window );">Other</a></td>
<td class="nump">271<span></span>
</td>
<td class="nump">156<span></span>
</td>
</tr>
<tr class="reu">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AccruedLiabilitiesCurrent', window );">Total accrued expenses</a></td>
<td class="nump">$ 4,179<span></span>
</td>
<td class="nump">$ 3,251<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_AccruedLiabilitiesCurrent">
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.20)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AccruedLiabilitiesCurrent</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Carrying value as of the balance sheet date of obligations incurred through that date and payable for professional fees, such as for legal and accounting services received. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section 45<br> -Paragraph 6<br> -URI http://asc.fasb.org/extlink&amp;oid=82887183&amp;loc=d3e6911-107765<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.20)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section 45<br> -Paragraph 8<br> -URI http://asc.fasb.org/extlink&amp;oid=82887183&amp;loc=d3e6935-107765<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AccruedProfessionalFeesCurrent</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td>xbrli:monetaryItemType</td>
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<td><strong> Balance Type:</strong></td>
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<td><strong> Period Type:</strong></td>
<td>instant</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DeferredRentCreditCurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>For a classified balance sheet, the cumulative difference as of the balance sheet date between the payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense, by the lessor or lessee, respectively, within one year of the balance sheet date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.20)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 840<br> -SubTopic 20<br> -Section 25<br> -Paragraph 2<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=77902458&amp;loc=d3e39927-112707<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DeferredRentCreditCurrent</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_EmployeeRelatedLiabilitiesCurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Total of the carrying values as of the balance sheet date of obligations incurred through that date and payable for obligations related to services received from employees, such as accrued salaries and bonuses, payroll taxes and fringe benefits. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.20)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_EmployeeRelatedLiabilitiesCurrent</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of expenses incurred but not yet paid classified as other, due within one year or the normal operating cycle, if longer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.20)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section 45<br> -Paragraph 6<br> -URI http://asc.fasb.org/extlink&amp;oid=82887183&amp;loc=d3e6911-107765<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section 45<br> -Paragraph 9<br> -URI http://asc.fasb.org/extlink&amp;oid=82887183&amp;loc=d3e7018-107765<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section 45<br> -Paragraph 8<br> -URI http://asc.fasb.org/extlink&amp;oid=82887183&amp;loc=d3e6935-107765<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OtherAccruedLiabilitiesCurrent</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PayablesAndAccrualsAbstract</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Balance Type:</strong></td>
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<td><strong> Period Type:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Accrued external research and development expenses.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_AccruedExternalResearchAndDevelopmentExpenses</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
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<tr>
<td><strong> Data Type:</strong></td>
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<td><strong> Balance Type:</strong></td>
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<title></title>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6660933536">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Long-Term Debt - Summary of Long Term Debt (Detail) - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
<th class="th" colspan="1">12 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Dec. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebtAbstract', window );"><strong>Long-term Debt, Unclassified [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebt', window );">Principal amount of long-term debt</a></td>
<td class="nump">$ 19,546<span></span>
</td>
<td class="nump">$ 10,000<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebtCurrent', window );">Less: Current portion of long-term debt</a></td>
<td class="num">(5,298)<span></span>
</td>
<td class="num">(1,687)<span></span>
</td>
</tr>
<tr class="rou">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebtNoncurrent', window );">Long-term debt, net of current portion</a></td>
<td class="nump">14,248<span></span>
</td>
<td class="nump">8,313<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentUnamortizedDiscount', window );">Debt discount, net of accretion</a></td>
<td class="num">(1,019)<span></span>
</td>
<td class="num">(226)<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_AccretionOnLongTermDebt', window );">Cumulative accretion of final payment due at maturity</a></td>
<td class="nump">136<span></span>
</td>
<td class="nump">58<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_LongTermDebtNonCurrentIncludingAccretion', window );">Long-term debt, including accretion, net of current portion</a></td>
<td class="nump">$ 13,365<span></span>
</td>
<td class="nump">$ 8,145<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentUnamortizedDiscount">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount, after accumulated amortization, of debt discount.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 835<br> -SubTopic 30<br> -Section 45<br> -Paragraph 1A<br> -URI http://asc.fasb.org/extlink&amp;oid=114775744&amp;loc=d3e28541-108399<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 835<br> -SubTopic 30<br> -Section 55<br> -Paragraph 8<br> -URI http://asc.fasb.org/extlink&amp;oid=114775985&amp;loc=d3e28878-108400<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentUnamortizedDiscount</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LongTermDebt">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 470<br> -SubTopic 20<br> -Section 50<br> -Paragraph 4<br> -Subparagraph (b)(3)<br> -URI http://asc.fasb.org/extlink&amp;oid=109500613&amp;loc=SL6031897-161870<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 944<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.7-03(a)(16))<br> -URI http://asc.fasb.org/extlink&amp;oid=6879938&amp;loc=d3e572229-122910<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 942<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.9-03(16))<br> -URI http://asc.fasb.org/extlink&amp;oid=6876686&amp;loc=d3e534808-122878<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(22))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LongTermDebt</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LongTermDebtAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LongTermDebtAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
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<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LongTermDebtCurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.19,20)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LongTermDebtCurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LongTermDebtNoncurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.22)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LongTermDebtNoncurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_AccretionOnLongTermDebt">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Accretion On Long Term Debt</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_AccretionOnLongTermDebt</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_LongTermDebtNonCurrentIncludingAccretion">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Long term debt non current including accretion.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_LongTermDebtNonCurrentIncludingAccretion</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6824177984">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Long Term Debt - SVB Loan Agreement - Additional Information (Detail) - SVB Loan Agreement [Member] - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th" colspan="2">1 Months Ended</th>
<th class="th" colspan="1">3 Months Ended</th>
<th class="th" colspan="1"></th>
<th class="th" colspan="1"></th>
</tr>
<tr>
<th class="th"><div>Oct. 31, 2018</div></th>
<th class="th"><div>Oct. 31, 2016</div></th>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Oct. 19, 2018</div></th>
<th class="th"><div>Jun. 30, 2017</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1', window );">Debt instrument variable percentage</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">5.50%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentDescriptionOfVariableRateBasis', window );">Debt instrument description</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Borrowings under the SVB Loan Agreement bore interest at a variable rate equal  to 5.5% plus the greater of (i) 3.5% or (ii) The Wall Street Journal prime rate.<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RepaymentsOfDebt', window );">Repayment of outstanding loan principal</a></td>
<td class="nump">$ 4,333<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_RepaymentOfDebtFinalPayment', window );">Repayments portion of total borrowing</a></td>
<td class="nump">270<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_DebtInstrumentPrepaymentPremium', window );">Debt instrument prepayment premium</a></td>
<td class="nump">87<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_DebtInstrumentAccruedInterest', window );">Debt instrument accrued interest</a></td>
<td class="nump">23<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_GainsLossesOnExtinguishmentOfDebt', window );">Gains losses on extinguishment of debt</a></td>
<td class="nump">229<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ReacquisitionPriceOfBorrowing', window );">Reacquisition price of borrowing</a></td>
<td class="nump">4,713<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_DebtInstrumentCarryingValue', window );">Debt instrument carrying value</a></td>
<td class="nump">$ 4,484<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentInterestRateStatedPercentage', window );">Debt instrument stated percentage</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">10.75%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_SvbLoanAgreementMember', window );">Minimum [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1', window );">Debt instrument variable percentage</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">3.50%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_SvbLoanAgreementMember', window );">Term Loan A [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity', window );">Maximum term loan borrowing capacity</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 6,000<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Percentage points added to the reference rate to compute the variable rate on the debt instrument.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentBasisSpreadOnVariableRate1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentDescriptionOfVariableRateBasis">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentDescriptionOfVariableRateBasis</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentInterestRateStatedPercentage">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Contractual interest rate for funds borrowed, under the debt agreement.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.22(a)(1))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentInterestRateStatedPercentage</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_GainsLossesOnExtinguishmentOfDebt">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 470<br> -SubTopic 50<br> -Section 40<br> -Paragraph 4<br> -URI http://asc.fasb.org/extlink&amp;oid=114001942&amp;loc=d3e12355-112629<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 470<br> -SubTopic 50<br> -Section 40<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=114001942&amp;loc=d3e12317-112629<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 28<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3602-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_GainsLossesOnExtinguishmentOfDebt</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.19(b),22(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_RepaymentsOfDebt">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 15<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3291-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_RepaymentsOfDebt</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_DebtInstrumentAccruedInterest">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Debt Instrument Accrued Interest</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_DebtInstrumentAccruedInterest</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_DebtInstrumentCarryingValue">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Debt Instrument Carrying Value</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_DebtInstrumentCarryingValue</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_DebtInstrumentPrepaymentPremium">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Debt Instrument, Prepayment Premium</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_DebtInstrumentPrepaymentPremium</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ReacquisitionPriceOfBorrowing">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Reacquisition price of borrowing.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ReacquisitionPriceOfBorrowing</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_RepaymentOfDebtFinalPayment">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Repayment of debt final payment.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_RepaymentOfDebtFinalPayment</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ScheduleOfLongTermDebtLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Schedule Of Long Term Debt [Line Items]</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ScheduleOfLongTermDebtLineItems</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentAxis=xfor_SvbLoanAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentAxis=xfor_SvbLoanAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_srt_RangeAxis=srt_MinimumMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">srt_RangeAxis=srt_MinimumMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CreditFacilityAxis=xfor_TermLoanAMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CreditFacilityAxis=xfor_TermLoanAMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
</div>
</body>
</html>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>XML
<SEQUENCE>69
<FILENAME>R53.htm
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
<script type="text/javascript" src="Show.js">/* Do Not Remove This Comment */</script><script type="text/javascript">
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<body>
<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6844292048">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Long Term Debt - Hercules Loan Agreement - Additional Information (Detail)<br> $ / shares in Units, $ in Thousands</strong></div></th>
<th class="th" colspan="1"></th>
<th class="th" colspan="1"></th>
<th class="th" colspan="1"></th>
<th class="th" colspan="1"></th>
<th class="th" colspan="1">1 Months Ended</th>
<th class="th" colspan="2">3 Months Ended</th>
<th class="th" colspan="1">12 Months Ended</th>
<th class="th" colspan="1"></th>
<th class="th" colspan="1"></th>
<th class="th" colspan="1"></th>
</tr>
<tr>
<th class="th">
<div>Mar. 31, 2019 </div>
<div>USD ($) </div>
<div>shares</div>
</th>
<th class="th">
<div>Mar. 18, 2019 </div>
<div>$ / shares </div>
<div>shares</div>
</th>
<th class="th">
<div>Dec. 31, 2018 </div>
<div>USD ($) </div>
<div>$ / shares </div>
<div>shares</div>
</th>
<th class="th">
<div>Oct. 31, 2018 </div>
<div>USD ($) </div>
<div>$ / shares </div>
<div>shares</div>
</th>
<th class="th">
<div>Oct. 31, 2018 </div>
<div>USD ($) </div>
<div>$ / shares </div>
<div>shares</div>
</th>
<th class="th">
<div>Mar. 31, 2019 </div>
<div>USD ($) </div>
<div>shares</div>
</th>
<th class="th">
<div>Mar. 31, 2018 </div>
<div>USD ($)</div>
</th>
<th class="th">
<div>Dec. 31, 2018 </div>
<div>USD ($) </div>
<div>$ / shares </div>
<div>shares</div>
</th>
<th class="th">
<div>Mar. 13, 2019 </div>
<div>USD ($)</div>
</th>
<th class="th">
<div>Dec. 11, 2018 </div>
<div>USD ($)</div>
</th>
<th class="th">
<div>Oct. 19, 2018 </div>
<div>USD ($)</div>
</th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DerivativeFairValueOfDerivativeLiability', window );">Fair value of warrants</a></td>
<td class="nump">$ 0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 5,235<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_UpfrontPayments', window );">Upfront payments</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 92<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_NonCashInterestExpense', window );">Non-cash interest expense</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">153<span></span>
</td>
<td class="nump">$ 27<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentUnamortizedDiscount', window );">Unamortized debt discount</a></td>
<td class="nump">$ 1,019<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 226<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 1,019<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 226<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember', window );">Arsanis [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights', window );">Warrant issued to purchase stock | shares</a></td>
<td class="nump">271,230,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">271,230,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_BusinessCombinationShareExchangeRatio1', window );">Business acquisition share exchange ratio</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">0.5702<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity', window );">Line of credit facility, maximum borrowing capacity</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">13,000<span></span>
</td>
<td class="nump">$ 13,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ProceedsFromLinesOfCredit', window );">Proceeds from lines of credit</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">8,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentInterestRateIncreaseDecrease', window );">Interest rate increase percentage</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">4.00%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentInterestRateStatedPercentage', window );">Debt instrument interest rate</a></td>
<td class="nump">9.80%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">9.75%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">9.80%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">9.75%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LineOfCreditFacilityInterestRateDescription', window );">Line of credit interest rate, Description</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Borrowings under the Hercules Loan Agreement bear interest at variable rates, with the first tranche bearing interest at a variable rate equal to the greater of (i) 9.5% or (ii) 9.5% plus The Wall Street Journal prime rate minus 5.25%, the second tranche bearing interest at a variable rate, subject to completion of specified financing conditions, equal to either (A) the greater of (i) 9.5% or (ii) 9.5% plus The Wall Street Journal prime rate minus 5.25% or (B) the greater of (i) 8.75% or (ii) 8.75% plus The Wall Street Journal prime rate minus 5.25%, and the third tranche bearing interest at a variable rate equal to the greater of (i) 8.75% or (ii) 8.75% plus The Wall Street Journal prime rate minus 5.25%. In an event of default, as defined, and until such event is no longer continuing, the interest rate applicable to borrowings under the Hercules Loan Agreement would be increased by 4.0%. As of March 31, 2019 and December 31, 2018, the interest rate applicable to borrowings under the Hercules Loan Agreement was 9.80% and 9.75%.<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RepaymentsOfLinesOfCredit', window );">Repayments of lines of credit</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">953<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LineOfCreditFacilityPeriodicPaymentInterest', window );">Line of credit facility, periodic payment, interest</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">794<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DerivativeLiabilities', window );">Fair value of derivative liability</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 18<span></span>
</td>
<td class="nump">$ 18<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_DebtCovenantMinimumLiquidityPercentageOfOutstandingBorrowings', window );">Minimum liquidity as a percentage of debt</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">125.00%<span></span>
</td>
<td class="nump">125.00%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_DebtCovenantMinimumLiquidityPercentageOfCashAndCashEquivalents', window );">Minimum liquidity as a percentage of debt</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">100.00%<span></span>
</td>
<td class="nump">100.00%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DerivativeFairValueOfDerivativeLiability', window );">Fair value of warrants</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 282<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 282<span></span>
</td>
<td class="nump">$ 326<span></span>
</td>
<td class="nump">$ 132<span></span>
</td>
<td class="nump">$ 132<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_InterestExpenseDebt', window );">Interest expense recognized</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 357<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_NonCashInterestExpense', window );">Non-cash interest expense</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">113<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentUnamortizedDiscount', window );">Unamortized debt discount</a></td>
<td class="nump">$ 182<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 226<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 182<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 226<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentInterestRateEffectivePercentage', window );">Effective interest rate of loan</a></td>
<td class="nump">14.20%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">14.20%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">14.20%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">14.20%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentPeriodicPaymentPrincipal', window );">Principal payments</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | Series B Redeemable Convertible Preferred Stock [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights', window );">Warrant issued to purchase stock | shares</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">210,638<span></span>
</td>
<td class="nump">210,638<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Warrant exercise price | $ / shares</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 1.88<span></span>
</td>
<td class="nump">$ 1.88<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsWarrantsExpirationPeriod', window );">Class of warrant expiration period</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">2028-10<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | Maximum [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_DebtInstrumentPrePaymentPremiumPercentage', window );">Debt instrument pre payment premium percentage</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">2.00%<span></span>
</td>
<td class="nump">2.00%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | Arsanis [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Warrant exercise price | $ / shares</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 19.80<span></span>
</td>
<td class="nump">$ 99<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 99<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight', window );">Number of warrant | shares</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">5,000<span></span>
</td>
<td class="nump">52,659<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">52,659<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_BusinessCombinationShareExchangeRatio1', window );">Business acquisition share exchange ratio</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">0.5702<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockholdersEquityNoteStockSplitConversionRatio1', window );">Reverse stock split, conversion ratio</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">0.166<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentRedemptionDescription', window );">Debt instrument redemption description</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">warrants was determined to be 52,659  shares, calculated by dividing $99 by the $1.88 price per share<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | First Tranche [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1', window );">Debt instrument variable percentage</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">9.50%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | First Tranche [Member] | Prime Rate [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod', window );">Line of credit facility interest rate</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">5.25%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | First Tranche [Member] | Minimum [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1', window );">Debt instrument variable percentage</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">9.50%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | Second Tranche A [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1', window );">Debt instrument variable percentage</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">9.50%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | Second Tranche A [Member] | Prime Rate [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod', window );">Line of credit facility interest rate</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">5.25%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | Second Tranche A [Member] | Minimum [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1', window );">Debt instrument variable percentage</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">9.50%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | Second Tranche B [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1', window );">Debt instrument variable percentage</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">8.75%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | Second Tranche B [Member] | Prime Rate [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod', window );">Line of credit facility interest rate</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">5.25%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | Second Tranche B [Member] | Minimum [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1', window );">Debt instrument variable percentage</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">8.75%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | Third Tranche [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1', window );">Debt instrument variable percentage</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">8.75%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | Third Tranche [Member] | Prime Rate [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod', window );">Line of credit facility interest rate</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">5.25%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | Third Tranche [Member] | Minimum [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1', window );">Debt instrument variable percentage</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">8.75%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | Term Loan [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity', window );">Line of credit facility, maximum borrowing capacity</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 8,000<span></span>
</td>
<td class="nump">$ 8,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | Additional Term Loan One [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity', window );">Line of credit facility, maximum borrowing capacity</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">2,000<span></span>
</td>
<td class="nump">2,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ProceedsFromLinesOfCredit', window );">Proceeds from lines of credit</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 2,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LineOfCreditFacilityExpirationDate1', window );">Line of credit facility, expiration date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Nov.  01,  2021<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member] | Additional Term Loan Two [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity', window );">Line of credit facility, maximum borrowing capacity</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 3,000<span></span>
</td>
<td class="nump">$ 3,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LineOfCreditFacilityExpirationDate1', window );">Line of credit facility, expiration date</a></td>
<td class="text">Mar.  01,  2019<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Exercise price per share or per unit of warrants or rights outstanding.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.4-08.(i)(4))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e23780-122690<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of securities into which each warrant or right may be converted. For example, but not limited to, each warrant may be converted into two shares.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.4-08.(i)(2))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e23780-122690<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Percentage points added to the reference rate to compute the variable rate on the debt instrument.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentBasisSpreadOnVariableRate1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentInterestRateEffectivePercentage">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 470<br> -SubTopic 20<br> -Section 50<br> -Paragraph 6<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=109500613&amp;loc=SL6036836-161870<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 835<br> -SubTopic 30<br> -Section 45<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=114775744&amp;loc=d3e28551-108399<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.22(a)(1))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentInterestRateEffectivePercentage</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentInterestRateIncreaseDecrease">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Incremental percentage increase (decrease) in the stated rate on a debt instrument.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentInterestRateIncreaseDecrease</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentInterestRateStatedPercentage">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Contractual interest rate for funds borrowed, under the debt agreement.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.22(a)(1))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentInterestRateStatedPercentage</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentPeriodicPaymentPrincipal">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of the required periodic payments applied to principal.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.22)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentPeriodicPaymentPrincipal</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentRedemptionDescription">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Description of debt redemption features under terms of the debt agreement.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 942<br> -SubTopic 470<br> -Section 50<br> -Paragraph 3<br> -Subparagraph e<br> -URI http://asc.fasb.org/extlink&amp;oid=75038535&amp;loc=d3e64711-112823<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentRedemptionDescription</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentUnamortizedDiscount">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount, after accumulated amortization, of debt discount.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 835<br> -SubTopic 30<br> -Section 45<br> -Paragraph 1A<br> -URI http://asc.fasb.org/extlink&amp;oid=114775744&amp;loc=d3e28541-108399<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 835<br> -SubTopic 30<br> -Section 55<br> -Paragraph 8<br> -URI http://asc.fasb.org/extlink&amp;oid=114775985&amp;loc=d3e28878-108400<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentUnamortizedDiscount</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DerivativeFairValueOfDerivativeLiability">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 860<br> -SubTopic 20<br> -Section 50<br> -Paragraph 4D<br> -Subparagraph (c)(2)<br> -URI http://asc.fasb.org/extlink&amp;oid=109247956&amp;loc=SL51823488-111719<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 815<br> -SubTopic 10<br> -Section 50<br> -Paragraph 4B<br> -Subparagraph (a),(c)<br> -URI http://asc.fasb.org/extlink&amp;oid=109980867&amp;loc=SL5624163-113959<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 20<br> -Section 50<br> -Paragraph 3<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=51824906&amp;loc=SL20225862-175312<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 20<br> -Section 55<br> -Paragraph 7<br> -URI http://asc.fasb.org/extlink&amp;oid=99393222&amp;loc=SL20226000-175313<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DerivativeFairValueOfDerivativeLiability</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DerivativeLiabilities">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 20<br> -Section 50<br> -Paragraph 3<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=51824906&amp;loc=SL20225862-175312<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 825<br> -SubTopic 10<br> -Section 50<br> -Paragraph 10<br> -URI http://asc.fasb.org/extlink&amp;oid=109250915&amp;loc=d3e13433-108611<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 20<br> -Section 55<br> -Paragraph 10<br> -URI http://asc.fasb.org/extlink&amp;oid=99393222&amp;loc=SL20226008-175313<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DerivativeLiabilities</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_InterestExpenseDebt">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of the cost of borrowed funds accounted for as interest expense for debt.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 470<br> -SubTopic 20<br> -Section 50<br> -Paragraph 6<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=109500613&amp;loc=SL6036836-161870<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section S99<br> -Paragraph 2<br> -Subparagraph (SX 210.5-03.8)<br> -URI http://asc.fasb.org/extlink&amp;oid=115205541&amp;loc=SL114868664-224227<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_InterestExpenseDebt</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LineOfCreditFacilityExpirationDate1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Date the credit facility terminates, in CCYY-MM-DD format.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.19(b),22(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LineOfCreditFacilityExpirationDate1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:dateItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LineOfCreditFacilityInterestRateDescription">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Description of the interest rate for the amounts borrowed under the credit facility, including the terms and the method for determining the interest rate (for example, fixed or variable, LIBOR plus a percentage, increasing rate, timing of interest rate resets, remarketing provisions).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.19(b),22(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LineOfCreditFacilityInterestRateDescription</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The effective interest rate during the reporting period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.19(b),22(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LineOfCreditFacilityInterestRateDuringPeriod</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.19(b),22(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LineOfCreditFacilityPeriodicPaymentInterest">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of the required periodic payment applied to interest.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.19(b),22(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LineOfCreditFacilityPeriodicPaymentInterest</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ProceedsFromLinesOfCredit">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 14<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3255-108585<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.4-08.(f))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e23780-122690<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ProceedsFromLinesOfCredit</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_RepaymentsOfLinesOfCredit">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of cash outflow for payment of an obligation from a lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 15<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3291-108585<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.4-08.(f))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e23780-122690<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_RepaymentsOfLinesOfCredit</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockholdersEquityNoteStockSplitConversionRatio1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 4<br> -Subparagraph (SAB TOPIC 4.C)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187143-122770<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockholdersEquityNoteStockSplitConversionRatio1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:pureItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_BusinessCombinationShareExchangeRatio1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Business Combination Share Exchange Ratio1</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_BusinessCombinationShareExchangeRatio1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:pureItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ClassOfWarrantOrRightsWarrantsExpirationPeriod">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Class Of Warrant Or Rights Warrants Expiration Period</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ClassOfWarrantOrRightsWarrantsExpirationPeriod</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:gYearMonthItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_DebtCovenantMinimumLiquidityPercentageOfCashAndCashEquivalents">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Debt Covenant Minimum Liquidity Percentage Of Cash And Cash Equivalents.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_DebtCovenantMinimumLiquidityPercentageOfCashAndCashEquivalents</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_DebtCovenantMinimumLiquidityPercentageOfOutstandingBorrowings">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Debt covenant minimum liquidity percentage of outstanding borrowings.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_DebtCovenantMinimumLiquidityPercentageOfOutstandingBorrowings</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_DebtInstrumentPrePaymentPremiumPercentage">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Debt Instrument Pre Payment Premium Percentage</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_DebtInstrumentPrePaymentPremiumPercentage</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_NonCashInterestExpense">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Non-cash interest expense.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_NonCashInterestExpense</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ScheduleOfLongTermDebtLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Schedule Of Long Term Debt [Line Items]</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ScheduleOfLongTermDebtLineItems</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_UpfrontPayments">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Upfront payments</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_UpfrontPayments</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_BusinessAcquisitionAxis=xfor_ArsanisMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesBRedeemableConvertiblePreferredStockMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementClassOfStockAxis=xfor_SeriesBRedeemableConvertiblePreferredStockMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_srt_RangeAxis=srt_MaximumMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">srt_RangeAxis=srt_MaximumMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_VestingAxis=xfor_FirstTrancheMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_VestingAxis=xfor_FirstTrancheMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_VariableRateAxis=us-gaap_PrimeRateMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_VariableRateAxis=us-gaap_PrimeRateMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_srt_RangeAxis=srt_MinimumMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">srt_RangeAxis=srt_MinimumMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_VestingAxis=xfor_SecondTrancheaMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_VestingAxis=xfor_SecondTrancheaMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_VestingAxis=xfor_SecondTranchebMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_VestingAxis=xfor_SecondTranchebMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_VestingAxis=xfor_ThirdTrancheMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_VestingAxis=xfor_ThirdTrancheMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CreditFacilityAxis=xfor_TermLoanMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CreditFacilityAxis=xfor_TermLoanMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CreditFacilityAxis=xfor_AdditionalTermLoanOneMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CreditFacilityAxis=xfor_AdditionalTermLoanOneMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CreditFacilityAxis=xfor_AdditionalTermLoanTwoMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CreditFacilityAxis=xfor_AdditionalTermLoanTwoMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
</div>
</body>
</html>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>XML
<SEQUENCE>70
<FILENAME>R54.htm
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
<script type="text/javascript" src="Show.js">/* Do Not Remove This Comment */</script><script type="text/javascript">
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<body>
<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6813488752">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Long Term Debt - FFG Loan Agreement - Additional Information (Detail) - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th" colspan="1"></th>
<th class="th" colspan="1">3 Months Ended</th>
<th class="th" colspan="1"></th>
</tr>
<tr>
<th class="th"><div>Mar. 08, 2019</div></th>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Dec. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebt', window );">Debt instrument, outstanding value</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 19,546<span></span>
</td>
<td class="nump">$ 10,000<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebtCurrent', window );">Debt instrument, current portion</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 5,298<span></span>
</td>
<td class="nump">$ 1,687<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_FfgLoanAgreementMember', window );">FFG Loan Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentMaturityDateRangeStart1', window );">Debt instrument, maturity start date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Mar. 31,  2019<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentMaturityDateRangeEnd1', window );">Debt instrument, maturity end date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Mar. 31,  2021<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebt', window );">Debt instrument, outstanding value</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 9,546<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebtCurrent', window );">Debt instrument, current portion</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 2,914<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_NumberOfYearsAcceleratedPaymentTerm', window );">Number of years accelerated payment</a></td>
<td class="text">3 years<span></span>
</td>
<td class="text">5 years<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RepaymentsOfDebt', window );">Repayment of outstanding loan principal</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 2,914<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_PercentageOfMinimumCashBalanceEqualToOutstandingPrincipalAmountOfLoans', window );">Percentage of minimum cash balance</a></td>
<td class="nump">70.00%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_FfgLoanAgreementMember', window );">FFG Loan Agreement [Member] | Minimum [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentInterestRateStatedPercentage', window );">Debt instrument, interest rate</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">0.75%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_FfgLoanAgreementMember', window );">FFG Loan Agreement [Member] | Maximum [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ScheduleOfLongTermDebtLineItems', window );"><strong>Schedule Of Long Term Debt [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentInterestRateStatedPercentage', window );">Debt instrument, interest rate</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">2.00%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentInterestRateStatedPercentage">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Contractual interest rate for funds borrowed, under the debt agreement.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.22(a)(1))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentInterestRateStatedPercentage</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
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</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentMaturityDateRangeEnd1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Latest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.22(a)(2))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentMaturityDateRangeEnd1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:dateItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentMaturityDateRangeStart1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Earliest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.22(a)(2))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentMaturityDateRangeStart1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:dateItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LongTermDebt">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 470<br> -SubTopic 20<br> -Section 50<br> -Paragraph 4<br> -Subparagraph (b)(3)<br> -URI http://asc.fasb.org/extlink&amp;oid=109500613&amp;loc=SL6031897-161870<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 944<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.7-03(a)(16))<br> -URI http://asc.fasb.org/extlink&amp;oid=6879938&amp;loc=d3e572229-122910<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 942<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.9-03(16))<br> -URI http://asc.fasb.org/extlink&amp;oid=6876686&amp;loc=d3e534808-122878<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(22))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LongTermDebt</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LongTermDebtCurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.19,20)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LongTermDebtCurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_RepaymentsOfDebt">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 15<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3291-108585<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_RepaymentsOfDebt</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
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<tr>
<td><strong> Period Type:</strong></td>
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</tr>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number Of Years Accelerated Payment Term</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_NumberOfYearsAcceleratedPaymentTerm</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Data Type:</strong></td>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_PercentageOfMinimumCashBalanceEqualToOutstandingPrincipalAmountOfLoans">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Percentage Of Minimum Cash Balance Equal To Outstanding Principal Amount Of Loans</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_PercentageOfMinimumCashBalanceEqualToOutstandingPrincipalAmountOfLoans</td>
</tr>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Data Type:</strong></td>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ScheduleOfLongTermDebtLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Schedule Of Long Term Debt [Line Items]</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ScheduleOfLongTermDebtLineItems</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DebtInstrumentAxis=xfor_FfgLoanAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentAxis=xfor_FfgLoanAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
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<td><strong> Balance Type:</strong></td>
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<tr>
<td><strong> Period Type:</strong></td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_srt_RangeAxis=srt_MinimumMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">srt_RangeAxis=srt_MinimumMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
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<td><strong> Balance Type:</strong></td>
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<td><strong> Period Type:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">srt_RangeAxis=srt_MaximumMember</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Data Type:</strong></td>
<td>na</td>
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<td><strong> Balance Type:</strong></td>
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<tr>
<td><strong> Period Type:</strong></td>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6824980240">
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<th class="tl" colspan="1" rowspan="1"><div style="width: 200px;"><strong>Long-Term Debt - Schedule of Future Principal Payments and the Final Payments Due (Detail) - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Dec. 31, 2018</div></th>
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<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_DebtMaturitiesLineItems', window );"><strong>Debt Maturities [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
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<td class="text">&#160;<span></span>
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<tr class="ro">
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<td class="nump">$ 4,259<span></span>
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</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo', window );">2020</a></td>
<td class="nump">8,767<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree', window );">2021</a></td>
<td class="nump">6,520<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="reu">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebt', window );">Long-term debt</a></td>
<td class="nump">19,546<span></span>
</td>
<td class="nump">$ 10,000<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember', window );">Hercules Loan Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_DebtMaturitiesLineItems', window );"><strong>Debt Maturities [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear', window );">2019</a></td>
<td class="nump">1,345<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo', window );">2020</a></td>
<td class="nump">4,305<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree', window );">2021</a></td>
<td class="nump">4,350<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="reu">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebt', window );">Long-term debt</a></td>
<td class="nump">10,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DebtInstrumentAxis=xfor_FfgLoanAgreementMember', window );">FFG Loan Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_DebtMaturitiesLineItems', window );"><strong>Debt Maturities [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear', window );">2019</a></td>
<td class="nump">2,914<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo', window );">2020</a></td>
<td class="nump">4,462<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree', window );">2021</a></td>
<td class="nump">2,170<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="reu">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LongTermDebt', window );">Long-term debt</a></td>
<td class="nump">$ 9,546<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
</table>
<div style="display: none;">
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 470<br> -SubTopic 20<br> -Section 50<br> -Paragraph 4<br> -Subparagraph (b)(3)<br> -URI http://asc.fasb.org/extlink&amp;oid=109500613&amp;loc=SL6031897-161870<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 944<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.7-03(a)(16))<br> -URI http://asc.fasb.org/extlink&amp;oid=6879938&amp;loc=d3e572229-122910<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 942<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.9-03(16))<br> -URI http://asc.fasb.org/extlink&amp;oid=6876686&amp;loc=d3e534808-122878<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(22))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LongTermDebt</td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
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<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
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<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 3<br> -Subparagraph (SX 210.12-04.(a))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e24072-122690<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 470<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6802200&amp;loc=d3e1835-112601<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree</td>
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<td><strong> Balance Type:</strong></td>
<td>credit</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 3<br> -Subparagraph (SX 210.12-04.(a))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e24072-122690<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 470<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6802200&amp;loc=d3e1835-112601<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the remainder of the fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 3<br> -Subparagraph (SX 210.12-04.(a))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e24072-122690<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear</td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Debt Maturities [Line Items]</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
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<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentAxis=xfor_HerculesLoanAgreementMember</td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DebtInstrumentAxis=xfor_FfgLoanAgreementMember</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6825384096">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Leases - Additional Information (Detail)<br> $ in Thousands</strong></div></th>
<th class="th" colspan="1"></th>
<th class="th" colspan="1"></th>
<th class="th" colspan="1">3 Months Ended</th>
<th class="th" colspan="1"></th>
</tr>
<tr>
<th class="th">
<div>Mar. 13, 2019 </div>
<div>USD ($) </div>
<div>ft&#178; </div>
<div>m&#178;</div>
</th>
<th class="th">
<div>Aug. 31, 2017 </div>
<div>USD ($) </div>
<div>ft&#178;</div>
</th>
<th class="th">
<div>Mar. 31, 2019 </div>
<div>USD ($)</div>
</th>
<th class="th">
<div>Jan. 01, 2019 </div>
<div>USD ($)</div>
</th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeLeaseDescriptionLineItems', window );"><strong>Lessee, Lease, Description [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseRightOfUseAsset', window );">Right-of-use assets</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 2,705<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
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<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseLiability', window );">Operating lease liabilities</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">4,116<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseLiabilityNoncurrent', window );">Lease liability, net of current portion</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">3,275<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
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<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseLiabilityCurrent', window );">Current portion of lease liability</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">841<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201602Member', window );">Accounting Standards Update 2016-02 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeLeaseDescriptionLineItems', window );"><strong>Lessee, Lease, Description [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseRightOfUseAsset', window );">Right-of-use assets</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">2,026<span></span>
</td>
<td class="nump">$ 2,026<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseLiability', window );">Operating lease liabilities</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 2,538<span></span>
</td>
<td class="nump">2,538<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseLiabilityNoncurrent', window );">Lease liability, net of current portion</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">1,925<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseLiabilityCurrent', window );">Current portion of lease liability</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">613<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DeferredRentCredit', window );">Net deferred, accrued and prepaid rent</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 512<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LeaseArrangementTypeAxis=xfor_CambridgeLeaseAgreementMember', window );">Cambridge Lease Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeLeaseDescriptionLineItems', window );"><strong>Lessee, Lease, Description [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LeaseExpirationDate1', window );">Lease expiration date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Jul. 31,  2022<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CurrentOfficeSpaceUnderLeaseAgreement', window );">Current office space under lease agreement | ft&#178;</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">13,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_LeaseAgreementExtensionDescription', window );">Option to extend the lease agreement</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">The Company has the option to extend the lease for one period of five additional years.<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeOperatingLeaseRenewalTerm', window );">Lease, renewal term of contract</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">5 years<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_AggregateBaseRent', window );">Base rent</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 810<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LeaseArrangementTypeAxis=xfor_WalthamLeaseMember', window );">Waltham Lease [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeLeaseDescriptionLineItems', window );"><strong>Lessee, Lease, Description [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CurrentOfficeSpaceUnderLeaseAgreement', window );">Current office space under lease agreement | ft&#178;</a></td>
<td class="nump">6,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_AggregateBaseRent', window );">Base rent</a></td>
<td class="nump">$ 459<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_AgreementCommencementDate', window );">Agreement commencement date</a></td>
<td class="text">Jan.  01,  2019<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_OperatingLeaseExpiration', window );">Operating lease expiration</a></td>
<td class="text">5 years<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LeaseArrangementTypeAxis=xfor_ViennaLeaseAgreementMember', window );">Vienna Lease [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeLeaseDescriptionLineItems', window );"><strong>Lessee, Lease, Description [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CurrentOfficeSpaceUnderLeaseAgreement', window );">Current office space under lease agreement | m&#178;</a></td>
<td class="nump">400<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_AggregateBaseRent', window );">Base rent</a></td>
<td class="nump">$ 155<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_AgreementCommencementDate', window );">Agreement commencement date</a></td>
<td class="text">Mar.  01,  2019<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeOperatingLeaseTermOfContract', window );">Lease, term of contract</a></td>
<td class="text">2 years<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_LeaseAgreementPeriodOfWrittenNoticeForCancellable', window );">Period for written notice for cancellable</a></td>
<td class="text">3 months<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DeferredRentCredit">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The cumulative difference between the rental payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense over the term of the leased property by the lessor or lessee, respectively.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 840<br> -SubTopic 20<br> -Section 25<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=77902458&amp;loc=d3e39896-112707<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DeferredRentCredit</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LeaseExpirationDate1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Date which lease or group of leases is set to expire, in CCYY-MM-DD format.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LeaseExpirationDate1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:dateItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LesseeLeaseDescriptionLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LesseeLeaseDescriptionLineItems</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LesseeOperatingLeaseRenewalTerm">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 3<br> -Subparagraph (a)(3)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918673-209980<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LesseeOperatingLeaseRenewalTerm</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:durationItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LesseeOperatingLeaseTermOfContract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 3<br> -Subparagraph (a)(3)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918673-209980<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LesseeOperatingLeaseTermOfContract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:durationItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeaseLiability">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Present value of lessee's discounted obligation for lease payments from operating lease.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 45<br> -Paragraph 1<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888419&amp;loc=SL77918627-209977<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeaseLiability</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeaseLiabilityCurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 45<br> -Paragraph 1<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888419&amp;loc=SL77918627-209977<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeaseLiabilityCurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeaseLiabilityNoncurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Present value of lessee's discounted obligation for lease payments from operating lease, classified as noncurrent.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 45<br> -Paragraph 1<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888419&amp;loc=SL77918627-209977<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeaseLiabilityNoncurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeaseRightOfUseAsset">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of lessee's right to use underlying asset under operating lease.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 45<br> -Paragraph 1<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888419&amp;loc=SL77918627-209977<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeaseRightOfUseAsset</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_AggregateBaseRent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Aggregate base rent.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_AggregateBaseRent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_AgreementCommencementDate">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Agreement Commencement Date</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_AgreementCommencementDate</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:dateItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_CurrentOfficeSpaceUnderLeaseAgreement">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Current office space under lease agreement.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_CurrentOfficeSpaceUnderLeaseAgreement</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:areaItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_LeaseAgreementExtensionDescription">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Lease agreement extension description.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_LeaseAgreementExtensionDescription</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_LeaseAgreementPeriodOfWrittenNoticeForCancellable">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Lease agreement period of written notice for cancellable.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_LeaseAgreementPeriodOfWrittenNoticeForCancellable</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:durationItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_OperatingLeaseExpiration">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Operating lease expiration.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_OperatingLeaseExpiration</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:durationItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201602Member">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201602Member</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LeaseArrangementTypeAxis=xfor_CambridgeLeaseAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LeaseArrangementTypeAxis=xfor_CambridgeLeaseAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LeaseArrangementTypeAxis=xfor_WalthamLeaseMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LeaseArrangementTypeAxis=xfor_WalthamLeaseMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LeaseArrangementTypeAxis=xfor_ViennaLeaseAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LeaseArrangementTypeAxis=xfor_ViennaLeaseAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
</div>
</body>
</html>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>XML
<SEQUENCE>73
<FILENAME>R57.htm
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
<script type="text/javascript" src="Show.js">/* Do Not Remove This Comment */</script><script type="text/javascript">
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6824757616">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Leases - Schedule of Components of Lease Expense (Detail)<br></strong></div></th>
<th class="th" colspan="2">3 Months Ended</th>
</tr>
<tr><th class="th" colspan="2">
<div>Mar. 31, 2019 </div>
<div>USD ($)</div>
</th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LeasesAbstract', window );"><strong>Leases [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="fn" style="border-bottom: 0px;"></td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseCost', window );">Fixed operating lease cost</a></td>
<td class="nump">$ 187,000<span></span>
</td>
<td class="fn" style="border-bottom: 0px;"></td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShortTermLeaseCost', window );">Short-term lease costs</a></td>
<td class="nump">8,000<span></span>
</td>
<td class="fn" style="border-bottom: 0px;"></td>
</tr>
<tr class="rou">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LeaseCost', window );">Total lease expense</a></td>
<td class="nump">195,000<span></span>
</td>
<td class="fn" style="border-bottom: 0px;"></td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeasePayments', window );">Operating cash flows from operating leases</a></td>
<td class="nump">201,000<span></span>
</td>
<td class="fn" style="border-bottom: 0px;"></td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability', window );">Leased assets obtained in exchange for new operating lease liabilities</a></td>
<td class="nump">$ 781<span></span>
</td>
<td class="fn" style="border-bottom: 0px;"><sup>[1]</sup></td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1', window );">Weighted-average remaining lease term-operating leases</a></td>
<td class="text">3 years 10 months 24 days<span></span>
</td>
<td class="fn" style="border-bottom: 0px;"></td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent', window );">Weighted-average discount rate-operating leases</a></td>
<td class="nump">9.00%<span></span>
</td>
<td class="fn" style="border-bottom: 0px;"></td>
</tr>
<tr><td colspan="3"></td></tr>
<tr><td colspan="3"><table class="outerFootnotes" width="100%"><tr class="outerFootnote">
<td style="vertical-align: top; width: 12pt;" valign="top">[1]</td>
<td style="vertical-align: top;" valign="top">Acquired in Merger with Arsanis</td>
</tr></table></td></tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LeaseCost">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of lease cost recognized by lessee for lease contract.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 4<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918686-209980<br><br>Reference 2: http://www.xbrl.org/2003/role/exampleRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 55<br> -Paragraph 53<br> -URI http://asc.fasb.org/extlink&amp;oid=77888399&amp;loc=SL77918982-209971<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LeaseCost</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LeasesAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LeasesAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeaseCost">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/exampleRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 55<br> -Paragraph 53<br> -URI http://asc.fasb.org/extlink&amp;oid=77888399&amp;loc=SL77918982-209971<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 4<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918686-209980<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeaseCost</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeasePayments">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 45<br> -Paragraph 5<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888419&amp;loc=SL77918643-209977<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 4<br> -Subparagraph (g)(1)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918686-209980<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeasePayments</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Weighted average discount rate for operating lease calculated at point in time.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 4<br> -Subparagraph (g)(4)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918686-209980<br><br>Reference 2: http://www.xbrl.org/2003/role/exampleRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 55<br> -Paragraph 53<br> -URI http://asc.fasb.org/extlink&amp;oid=77888399&amp;loc=SL77918982-209971<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Weighted average remaining lease term for operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/exampleRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 55<br> -Paragraph 53<br> -URI http://asc.fasb.org/extlink&amp;oid=77888399&amp;loc=SL77918982-209971<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 4<br> -Subparagraph (g)(3)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918686-209980<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:durationItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of increase in right-of-use asset obtained in exchange for operating lease liability.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/exampleRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 55<br> -Paragraph 53<br> -URI http://asc.fasb.org/extlink&amp;oid=77888399&amp;loc=SL77918982-209971<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 4<br> -Subparagraph (g)(2)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918686-209980<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShortTermLeaseCost">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of short-term lease cost, excluding expense for lease with term of one month or less.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 4<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918686-209980<br><br>Reference 2: http://www.xbrl.org/2003/role/exampleRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 55<br> -Paragraph 53<br> -URI http://asc.fasb.org/extlink&amp;oid=77888399&amp;loc=SL77918982-209971<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShortTermLeaseCost</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
</div>
</body>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6819333936">
<tr>
<th class="tl" colspan="1" rowspan="1"><div style="width: 200px;"><strong>Leases - Schedule of Maturities of Lease Liabilities (Detail)<br> $ in Thousands</strong></div></th>
<th class="th">
<div>Mar. 31, 2019 </div>
<div>USD ($)</div>
</th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LeasesAbstract', window );"><strong>Leases [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear', window );">2019 (remainder of 2019)</a></td>
<td class="nump">$ 837<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo', window );">2020</a></td>
<td class="nump">1,281<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree', window );">2021</a></td>
<td class="nump">1,304<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour', window );">2022</a></td>
<td class="nump">970<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive', window );">2023</a></td>
<td class="nump">489<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive', window );">Thereafter</a></td>
<td class="nump">0<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue', window );">Total lease payments</a></td>
<td class="nump">4,880<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount', window );">Less: interest</a></td>
<td class="num">(764)<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeaseLiability', window );">Total operating lease liabilities as of March 31, 2019</a></td>
<td class="nump">$ 4,116<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LeasesAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LeasesAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of lessee's undiscounted obligation for lease payments for operating lease.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 6<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918701-209980<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of lessee's undiscounted obligation for lease payments for operating lease, due after fifth fiscal year following latest fiscal year.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 6<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918701-209980<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of lessee's undiscounted obligation for lease payments for operating lease, due in fifth fiscal year following latest fiscal year.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 6<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918701-209980<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of lessee's undiscounted obligation for lease payments for operating lease, due in fourth fiscal year following latest fiscal year.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 6<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918701-209980<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of lessee's undiscounted obligation for lease payments for operating lease, due in third fiscal year following latest fiscal year.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 6<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918701-209980<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of lessee's undiscounted obligation for lease payments for operating lease, due in second fiscal year following latest fiscal year.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 6<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918701-209980<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of lessee's undiscounted obligation for lease payments for operating lease having an initial or remaining lease term in excess of one year due in remainder of fiscal year following latest fiscal year.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 6<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918701-209980<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for operating lease.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 50<br> -Paragraph 6<br> -URI http://asc.fasb.org/extlink&amp;oid=77888426&amp;loc=SL77918701-209980<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeaseLiability">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Present value of lessee's discounted obligation for lease payments from operating lease.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 842<br> -SubTopic 20<br> -Section 45<br> -Paragraph 1<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=77888419&amp;loc=SL77918627-209977<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeaseLiability</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6817788976">
<tr>
<th class="tl" colspan="1" rowspan="1"><div style="width: 200px;"><strong>Leases - Summary of Future Minimum Lease Payments Due under Operating Leases (Detail)<br> $ in Thousands</strong></div></th>
<th class="th">
<div>Dec. 31, 2018 </div>
<div>USD ($)</div>
</th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_LeasesAbstract', window );"><strong>Leases [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear', window );">2019</a></td>
<td class="nump">$ 810<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears', window );">2020</a></td>
<td class="nump">823<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears', window );">2021</a></td>
<td class="nump">835<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears', window );">2022</a></td>
<td class="nump">492<span></span>
</td>
</tr>
<tr class="rou">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_OperatingLeasesFutureMinimumPaymentsDue', window );">Total</a></td>
<td class="nump">$ 2,960<span></span>
</td>
</tr>
</table>
<div style="display: none;">
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_LeasesAbstract</td>
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<td><strong> Period Type:</strong></td>
<td>duration</td>
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</table></div>
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</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeasesFutureMinimumPaymentsDue">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 840<br> -SubTopic 10<br> -Section 55<br> -Paragraph 40<br> -Subparagraph (Note 3)<br> -URI http://asc.fasb.org/extlink&amp;oid=82846649&amp;loc=d3e38371-112697<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 840<br> -SubTopic 20<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=77902758&amp;loc=d3e41502-112717<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeasesFutureMinimumPaymentsDue</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 840<br> -SubTopic 10<br> -Section 55<br> -Paragraph 40<br> -Subparagraph (Note 3)<br> -URI http://asc.fasb.org/extlink&amp;oid=82846649&amp;loc=d3e38371-112697<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 840<br> -SubTopic 20<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=77902758&amp;loc=d3e41502-112717<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 840<br> -SubTopic 10<br> -Section 55<br> -Paragraph 40<br> -Subparagraph (Note 3)<br> -URI http://asc.fasb.org/extlink&amp;oid=82846649&amp;loc=d3e38371-112697<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 840<br> -SubTopic 20<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=77902758&amp;loc=d3e41502-112717<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 840<br> -SubTopic 10<br> -Section 55<br> -Paragraph 40<br> -Subparagraph (Note 3)<br> -URI http://asc.fasb.org/extlink&amp;oid=82846649&amp;loc=d3e38371-112697<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 840<br> -SubTopic 20<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=77902758&amp;loc=d3e41502-112717<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the remainder of the fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6837370080">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Commitment and Contingencies - Additional Information (Detail) - USD ($)<br></strong></div></th>
<th class="th" colspan="2">1 Months Ended</th>
<th class="th" colspan="2">3 Months Ended</th>
<th class="th" colspan="1"></th>
</tr>
<tr>
<th class="th"><div>Apr. 30, 2017</div></th>
<th class="th"><div>Feb. 28, 2017</div></th>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Mar. 31, 2018</div></th>
<th class="th"><div>Dec. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ContingenciesAndCommitmentsLineItems', window );"><strong>Contingencies And Commitments [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ResearchAndDevelopmentExpense', window );">Research and development expense</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 5,655,000<span></span>
</td>
<td class="nump">$ 4,744,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_SponsoredResearchAgreementMember', window );">Sponsored Research Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ContingenciesAndCommitmentsLineItems', window );"><strong>Contingencies And Commitments [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_MaximumFundingCommitmentAmount', window );">Purchase commitment, amount</a></td>
<td class="nump">$ 499,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_FundingCommitmentPeriod', window );">Purchase commitment, period</a></td>
<td class="text">3 years<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ResearchAndDevelopmentExpense', window );">Research and development expense</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">42,000<span></span>
</td>
<td class="nump">$ 42,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PurchaseObligation', window );">Non-cancelable purchase commitments amount</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">181,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear', window );">Non-cancelable purchase commitments amount, 2019</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">125,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PurchaseObligationDueInSecondYear', window );">Non-cancelable purchase commitments amount, 2020</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">56,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_IndemnificationAgreementsMember', window );">Indemnification Agreements [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ContingenciesAndCommitmentsLineItems', window );"><strong>Contingencies And Commitments [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AccruedLiabilitiesCurrentAndNoncurrent', window );">Accrued liabilities</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_AdimabOptionAgreementMember', window );">Adimab Option Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ContingenciesAndCommitmentsLineItems', window );"><strong>Contingencies And Commitments [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_MilestonePayments', window );">Milestone payments</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 25,000,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_OptionFee', window );">Option fee</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 250,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_ContractManufacturingOrganizationsAgreementMember', window );">Contract Manufacturing Organizations Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ContingenciesAndCommitmentsLineItems', window );"><strong>Contingencies And Commitments [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PurchaseObligation', window );">Non-cancelable purchase commitments amount</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 250,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 250,000<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_AccruedLiabilitiesCurrentAndNoncurrent">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 942<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.9-03.15(5))<br> -URI http://asc.fasb.org/extlink&amp;oid=6876686&amp;loc=d3e534808-122878<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 944<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.7-03.15(a))<br> -URI http://asc.fasb.org/extlink&amp;oid=6879938&amp;loc=d3e572229-122910<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AccruedLiabilitiesCurrentAndNoncurrent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_PurchaseObligation">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PurchaseObligation</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_PurchaseObligationDueInSecondYear">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Minimum amount of purchase arrangement maturing in the second fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PurchaseObligationDueInSecondYear</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Minimum amount of purchase arrangement maturing in the remainder of the fiscal year following the latest fiscal year ended. Includes, but is not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ResearchAndDevelopmentExpense">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 985<br> -SubTopic 20<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6501960&amp;loc=d3e128462-111756<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 730<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6420194&amp;loc=d3e21568-108373<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ResearchAndDevelopmentExpense</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ContingenciesAndCommitmentsLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Contingencies And Commitments [Line Items]</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ContingenciesAndCommitmentsLineItems</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_FundingCommitmentPeriod">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Funding commitment period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_FundingCommitmentPeriod</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:durationItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_MaximumFundingCommitmentAmount">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Maximum funding commitment amount.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_MaximumFundingCommitmentAmount</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_MilestonePayments">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Milestone payments.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_MilestonePayments</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_OptionFee">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Option fee.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_OptionFee</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TypeOfArrangementAxis=xfor_SponsoredResearchAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TypeOfArrangementAxis=xfor_SponsoredResearchAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TypeOfArrangementAxis=xfor_IndemnificationAgreementsMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TypeOfArrangementAxis=xfor_IndemnificationAgreementsMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TypeOfArrangementAxis=xfor_AdimabOptionAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TypeOfArrangementAxis=xfor_AdimabOptionAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TypeOfArrangementAxis=xfor_ContractManufacturingOrganizationsAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TypeOfArrangementAxis=xfor_ContractManufacturingOrganizationsAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
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<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6840952576">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Preferred and Common Stock Warrants - Summary of Outstanding Warrants to Purchase Shares of Common Stock (Detail) - $ / shares<br></strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
<th class="th" colspan="1">12 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Dec. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="nump">494,054<span></span>
</td>
<td class="nump">5,146,400<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnAugustFourteenTwoThousandFifteenMember', window );">Issuance On August 14, 2015 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">Aug. 14,  2015<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="nump">81,228<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="nump">$ 21.78<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">Aug. 14,  2020<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnAugustTwentyOneTwoThousandFifteenMember', window );">Issuance On August 21, 2015 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">Aug. 21,  2015<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="nump">69,603<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="nump">$ 21.78<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">Aug. 21,  2020<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnOctoberTwentyFiveTwoThousandSixteenMember', window );">Issuance On October 25, 2016 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">Nov. 25,  2016<span></span>
</td>
<td class="text">Oct. 25,  2016<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="nump">5,155<span></span>
</td>
<td class="nump">54,256<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="nump">$ 19.78<span></span>
</td>
<td class="nump">$ 1.88<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">Oct. 24,  2026<span></span>
</td>
<td class="text">Oct. 24,  2026<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnNovemberOneTwoThousandSeventeenMember', window );">Issuance On November 1, 2017 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">Nov.  01,  2017<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="nump">130,609<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="nump">$ 19.78<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">Oct. 31,  2020<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnNovemberSeventeenTwoThousandSeventeenMember', window );">Issuance On November 17, 2017 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">Nov. 17,  2017<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="nump">8,442<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="nump">$ 19.78<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">Nov. 16,  2020<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnDecemberFourTwoThousandSeventeenMember', window );">Issuance On December 4, 2017 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">Dec.  04,  2017<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="nump">5,661<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="nump">$ 19.78<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">Dec.  03,  2020<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenMember', window );">Issuance On December 28, 2017 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">Dec. 28,  2017<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="nump">6,925<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="nump">$ 19.78<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">Dec. 27,  2020<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenOneMember', window );">Issuance On December 28, 2017 One [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">Dec. 28,  2017<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="nump">115,916<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="nump">$ 19.78<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">Dec. 28,  2027<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenMember', window );">Issuance On September 12, 2018 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">Sep. 12,  2018<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="nump">25,275<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="nump">$ 19.78<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">Sep. 12,  2021<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenOneMember', window );">Issuance On September 12, 2018 One [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">Sep. 12,  2018<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="nump">20,220<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="nump">$ 19.78<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">Sep. 12,  2028<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnOctoberNineteenTwoThousandEighteenMember', window );">Issuance On October 19, 2018 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">Oct. 19,  2018<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="nump">20,016<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="nump">$ 19.78<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">Oct. 19,  2028<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnDecemberElevenTwoThousandEighteenMember', window );">Issuance On December 11, 2018 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">Dec. 11,  2018<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="nump">5,004<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="nump">$ 19.80<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">Oct. 19,  2021<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesAPreferredStockWarrantsMember', window );">Series A Preferred Stock Warrants [Member] | Issuance On August 14, 2015 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Aug. 14,  2015<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">854,785<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 2.07<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Aug. 14,  2020<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesAPreferredStockWarrantsMember', window );">Series A Preferred Stock Warrants [Member] | Issuance On August 21, 2015 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Aug. 21,  2015<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">732,453<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 2.07<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Aug. 21,  2020<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesBPreferredStockWarrantsMember', window );">Series B Preferred Stock Warrants [Member] | Issuance On November 1, 2017 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Nov.  01,  2017<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">1,374,435<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 1.88<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Oct. 31,  2020<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesBPreferredStockWarrantsMember', window );">Series B Preferred Stock Warrants [Member] | Issuance On November 17, 2017 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Nov. 17,  2017<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">88,845<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 1.88<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Nov. 16,  2020<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesBPreferredStockWarrantsMember', window );">Series B Preferred Stock Warrants [Member] | Issuance On December 4, 2017 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Dec.  04,  2017<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">59,576<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 1.88<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Dec.  03,  2020<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesBPreferredStockWarrantsMember', window );">Series B Preferred Stock Warrants [Member] | Issuance On December 28, 2017 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Dec. 28,  2017<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">72,875<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 1.88<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Dec. 27,  2020<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesBPreferredStockWarrantsMember', window );">Series B Preferred Stock Warrants [Member] | Issuance On December 28, 2017 One [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Dec. 28,  2017<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">1,219,815<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 1.88<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Dec. 28,  2027<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesBPreferredStockWarrantsMember', window );">Series B Preferred Stock Warrants [Member] | Issuance On September 12, 2018 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Sep. 12,  2018<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">265,957<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 1.88<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Sep. 12,  2021<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesBPreferredStockWarrantsMember', window );">Series B Preferred Stock Warrants [Member] | Issuance On September 12, 2018 One [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Sep. 12,  2018<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">212,765<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 1.88<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Sep. 12,  2028<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesBPreferredStockWarrantsMember', window );">Series B Preferred Stock Warrants [Member] | Issuance On October 19, 2018 [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightLineItems', window );"><strong>Class of Warrant or Right [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsIssuanceDate', window );">Issuance Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Oct. 19,  2018<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightOutstanding', window );">Number of Shares of common Stock Issuable</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">210,638<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Exercise Price</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 1.88<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightsExpirationDate', window );">Expiration Date</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Oct. 19,  2028<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Exercise price per share or per unit of warrants or rights outstanding.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.4-08.(i)(4))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e23780-122690<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightLineItems</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightOutstanding">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of warrants or rights outstanding.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.4-08.(i))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e23780-122690<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightOutstanding</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ClassOfWarrantOrRightsExpirationDate">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Class of warrant or rights expiration date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ClassOfWarrantOrRightsExpirationDate</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:dateItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ClassOfWarrantOrRightsIssuanceDate">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Class Of Warrant Or Rights Issuance Date</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ClassOfWarrantOrRightsIssuanceDate</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:dateItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnAugustFourteenTwoThousandFifteenMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnAugustFourteenTwoThousandFifteenMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnAugustTwentyOneTwoThousandFifteenMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnAugustTwentyOneTwoThousandFifteenMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnOctoberTwentyFiveTwoThousandSixteenMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnOctoberTwentyFiveTwoThousandSixteenMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnNovemberOneTwoThousandSeventeenMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnNovemberOneTwoThousandSeventeenMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnNovemberSeventeenTwoThousandSeventeenMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnNovemberSeventeenTwoThousandSeventeenMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnDecemberFourTwoThousandSeventeenMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnDecemberFourTwoThousandSeventeenMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenOneMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnDecemberTwentyEightTwoThousandSeventeenOneMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenOneMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnSeptemberTwelveTwoThousandEighteenOneMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnOctoberNineteenTwoThousandEighteenMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnOctoberNineteenTwoThousandEighteenMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnDecemberElevenTwoThousandEighteenMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightAxis=xfor_IssuanceOnDecemberElevenTwoThousandEighteenMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesAPreferredStockWarrantsMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementClassOfStockAxis=xfor_SeriesAPreferredStockWarrantsMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesBPreferredStockWarrantsMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementClassOfStockAxis=xfor_SeriesBPreferredStockWarrantsMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
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</div>
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<DOCUMENT>
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<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
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<body>
<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6817606032">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Preferred and Common Stock Warrants - Additional Information (Detail) - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
<th class="th" colspan="1"></th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Mar. 13, 2019</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_EquityAbstract', window );"><strong>Equity [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DerivativeFairValueOfDerivativeLiability', window );">Fair value of warrant purchase</a></td>
<td class="nump">$ 0<span></span>
</td>
<td class="nump">$ 5,235<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_FairValueOptionChangesInFairValueGainLoss1', window );">Gain (loss) on change in fair value of warrant</a></td>
<td class="nump">$ 288<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DerivativeFairValueOfDerivativeLiability">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 860<br> -SubTopic 20<br> -Section 50<br> -Paragraph 4D<br> -Subparagraph (c)(2)<br> -URI http://asc.fasb.org/extlink&amp;oid=109247956&amp;loc=SL51823488-111719<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 815<br> -SubTopic 10<br> -Section 50<br> -Paragraph 4B<br> -Subparagraph (a),(c)<br> -URI http://asc.fasb.org/extlink&amp;oid=109980867&amp;loc=SL5624163-113959<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 20<br> -Section 50<br> -Paragraph 3<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=51824906&amp;loc=SL20225862-175312<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 20<br> -Section 55<br> -Paragraph 7<br> -URI http://asc.fasb.org/extlink&amp;oid=99393222&amp;loc=SL20226000-175313<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DerivativeFairValueOfDerivativeLiability</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_EquityAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_EquityAbstract</td>
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<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
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<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_FairValueOptionChangesInFairValueGainLoss1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>For each line item in the statement of financial position, the amounts of gains and losses from fair value changes included in earnings.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 825<br> -SubTopic 10<br> -Section 50<br> -Paragraph 30<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=75031198&amp;loc=d3e14172-108612<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FairValueOptionChangesInFairValueGainLoss1</td>
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<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
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<DOCUMENT>
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<TEXT>
<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
<script type="text/javascript" src="Show.js">/* Do Not Remove This Comment */</script><script type="text/javascript">
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6836980848">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Common Stock, Redeemable Common Stock, and Convertible Preferred Stock - Additional Information (Detail)<br></strong></div></th>
<th class="th" colspan="1">1 Months Ended</th>
<th class="th" colspan="1">3 Months Ended</th>
<th class="th" colspan="1">12 Months Ended</th>
</tr>
<tr>
<th class="th">
<div>Aug. 31, 2015 </div>
<div>USD ($) </div>
<div>$ / shares </div>
<div>shares</div>
</th>
<th class="th">
<div>Mar. 31, 2019 </div>
<div>USD ($) </div>
<div>Directors </div>
<div>$ / shares </div>
<div>shares</div>
</th>
<th class="th">
<div>Dec. 31, 2018 </div>
<div>USD ($) </div>
<div>$ / shares </div>
<div>shares</div>
</th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommonStockSharesAuthorized', window );">Common stock, authorized shares</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">33,333,333<span></span>
</td>
<td class="nump">11,070,776<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommonStockParOrStatedValuePerShare', window );">Common stock, par value | $ / shares</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 0.001<span></span>
</td>
<td class="nump">$ 0.001<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CommonStockVotingRights', window );">Common stock, voting right</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Each share of common stock entitles the holder to one vote on all matters  submitted to a vote of the Company's stockholders. The holders of common stock,  voting exclusively and as a separate class, are entitled to elect one director  of the Company.<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_NumberOfDirectorsEntitledToBeElected', window );">Number of directors entitled to be elected | Directors</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">1<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DividendsCommonStock', window );">Dividends on common stock declared or paid | $</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesAuthorized', window );">Convertible preferred stock, shares authorized</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">49,413,523<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PreferredStockValueOutstanding', window );">Preferred stock outstanding | $</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_GenzymeAgreementMember', window );">Genzyme Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_StockIssuedDuringPeriodSharesLicenseAgreement', window );">Stock issued during period</a></td>
<td class="nump">107,371<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_StockIssuedDuringPeriodValueLicenseAgreement', window );">Common stock aggregate fair value | $</a></td>
<td class="nump">$ 734,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CommonStockRepurchasePricePerShare', window );">Common stock repurchase price per share | $ / shares</a></td>
<td class="nump">$ 0.01<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesSeedConvertiblePreferredStockMember', window );">Series Seed Preferred Stock [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesAuthorized', window );">Convertible preferred stock, shares authorized</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">10,000,000<span></span>
</td>
<td class="nump">59,413,523<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityParOrStatedValuePerShare', window );">Convertible preferred stock, par or stated value per share | $ / shares</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 0.001<span></span>
</td>
<td class="nump">$ 0.001<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CommonStockParOrStatedValuePerShare">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Face amount or stated value per share of common stock.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CommonStockParOrStatedValuePerShare</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CommonStockSharesAuthorized">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The maximum number of common shares permitted to be issued by an entity's charter and bylaws.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CommonStockSharesAuthorized</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CommonStockVotingRights">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Description of voting rights of common stock. Includes eligibility to vote and votes per share owned. Include also, if any, unusual voting rights.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21475-112644<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CommonStockVotingRights</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
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<tr>
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<td>duration</td>
</tr>
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</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DividendsCommonStock">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of paid and unpaid common stock dividends declared with the form of settlement in cash, stock and payment-in-kind (PIK).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 942<br> -SubTopic 405<br> -Section 45<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=6957935&amp;loc=d3e64057-112817<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DividendsCommonStock</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_PreferredStockValueOutstanding">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Value of all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by shareholders, which is net of related treasury stock. May be all or a portion of the number of preferred shares authorized. These shares represent the ownership interest of the preferred shareholders.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(28))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PreferredStockValueOutstanding</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TemporaryEquityParOrStatedValuePerShare">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Per share amount of par value or stated value of stock classified as temporary equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 480<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=65877616&amp;loc=d3e177068-122764<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (27)<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquityParOrStatedValuePerShare</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TemporaryEquitySharesAuthorized">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The maximum number of securities classified as temporary equity that are permitted to be issued by an entity's charter and bylaws. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(27)(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquitySharesAuthorized</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_CommonStockRepurchasePricePerShare">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Common Stock Repurchase Price Per Share</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_CommonStockRepurchasePricePerShare</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_NumberOfDirectorsEntitledToBeElected">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of directors entitled to be elected.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_NumberOfDirectorsEntitledToBeElected</td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_StockIssuedDuringPeriodSharesLicenseAgreement">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Stock Issued During Period Shares License Agreement</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_StockIssuedDuringPeriodSharesLicenseAgreement</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
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<td>na</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
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</table></div>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_StockIssuedDuringPeriodValueLicenseAgreement">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Stock Issued During Period Value License Agreement</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_StockIssuedDuringPeriodValueLicenseAgreement</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TypeOfArrangementAxis=xfor_GenzymeAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TypeOfArrangementAxis=xfor_GenzymeAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesSeedConvertiblePreferredStockMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementClassOfStockAxis=xfor_SeriesSeedConvertiblePreferredStockMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
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<head>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6836889536">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Common Stock, Redeemable Common Stock, and Convertible Preferred Stock - Convertible Preferred Stock (Detail)<br> $ in Thousands</strong></div></th>
<th class="th" colspan="1">12 Months Ended</th>
</tr>
<tr><th class="th">
<div>Dec. 31, 2018 </div>
<div>USD ($) </div>
<div>shares</div>
</th></tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityLineItems', window );"><strong>Temporary Equity [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesAuthorized', window );">Preferred Stock Designated</a></td>
<td class="nump">49,413,523<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesIssued', window );">Preferred Stock Issued</a></td>
<td class="nump">40,079,567<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesOutstanding', window );">Preferred Stock Outstanding</a></td>
<td class="nump">40,079,567<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityCarryingAmountAttributableToParent', window );">Carrying Value | $</a></td>
<td class="nump">$ 64,675<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityLiquidationPreference', window );">Liquidation Preference | $</a></td>
<td class="nump">$ 84,067<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_NumberOfCommonStockSharesIssuableUponConversion', window );">Common Stock Issuable Upon Conversion</a></td>
<td class="nump">3,808,430<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_SeriesSeedPreferredStockMember', window );">Series Seed Preferred Stock [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityLineItems', window );"><strong>Temporary Equity [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesAuthorized', window );">Preferred Stock Designated</a></td>
<td class="nump">2,313,523<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesIssued', window );">Preferred Stock Issued</a></td>
<td class="nump">1,516,136<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesOutstanding', window );">Preferred Stock Outstanding</a></td>
<td class="nump">1,516,136<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityCarryingAmountAttributableToParent', window );">Carrying Value | $</a></td>
<td class="nump">$ 1,310<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityLiquidationPreference', window );">Liquidation Preference | $</a></td>
<td class="nump">$ 1,444<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_NumberOfCommonStockSharesIssuableUponConversion', window );">Common Stock Issuable Upon Conversion</a></td>
<td class="nump">143,630<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=us-gaap_SeriesAPreferredStockMember', window );">Series A Preferred Stock</a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityLineItems', window );"><strong>Temporary Equity [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesAuthorized', window );">Preferred Stock Designated</a></td>
<td class="nump">22,000,000<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesIssued', window );">Preferred Stock Issued</a></td>
<td class="nump">19,946,862<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesOutstanding', window );">Preferred Stock Outstanding</a></td>
<td class="nump">19,946,862<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityCarryingAmountAttributableToParent', window );">Carrying Value | $</a></td>
<td class="nump">$ 32,480<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityLiquidationPreference', window );">Liquidation Preference | $</a></td>
<td class="nump">$ 47,624<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_NumberOfCommonStockSharesIssuableUponConversion', window );">Common Stock Issuable Upon Conversion</a></td>
<td class="nump">1,895,610<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=us-gaap_SeriesBPreferredStockMember', window );">Series B Preferred Stock</a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityLineItems', window );"><strong>Temporary Equity [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesAuthorized', window );">Preferred Stock Designated</a></td>
<td class="nump">25,100,000<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesIssued', window );">Preferred Stock Issued</a></td>
<td class="nump">18,616,569<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquitySharesOutstanding', window );">Preferred Stock Outstanding</a></td>
<td class="nump">18,616,569<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityCarryingAmountAttributableToParent', window );">Carrying Value | $</a></td>
<td class="nump">$ 30,885<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityLiquidationPreference', window );">Liquidation Preference | $</a></td>
<td class="nump">$ 34,999<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_NumberOfCommonStockSharesIssuableUponConversion', window );">Common Stock Issuable Upon Conversion</a></td>
<td class="nump">1,769,190<span></span>
</td>
</tr>
</table>
<div style="display: none;">
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Carrying amount, attributable to parent, of an entity's issued and outstanding stock which is not included within permanent equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. Includes stock with a put option held by an ESOP and stock redeemable by a holder only in the event of a change in control of the issuer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquityCarryingAmountAttributableToParent</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
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</div></td></tr>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquityLineItems</td>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
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</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TemporaryEquityLiquidationPreference">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The aggregate liquidation preference (or restrictions) of stock classified as temporary equity that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02.28(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquityLiquidationPreference</td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The maximum number of securities classified as temporary equity that are permitted to be issued by an entity's charter and bylaws. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(27)(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquitySharesAuthorized</td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The number of securities classified as temporary equity that have been sold (or granted) to the entity's shareholders. Securities issued include securities outstanding and securities held in treasury. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(27)(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TemporaryEquitySharesIssued</td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The number of securities classified as temporary equity that have been issued and are held by the entity's shareholders. Securities outstanding equals securities issued minus securities held in treasury. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(27)(b))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of Common Stock Shares Issuable Upon Conversion</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6842719360">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Stock-Based Compensation - Additional Information (Detail) - USD ($)<br> $ / shares in Units, $ in Thousands</strong></div></th>
<th class="th" colspan="1">1 Months Ended</th>
<th class="th" colspan="1">3 Months Ended</th>
<th class="th" colspan="1"></th>
</tr>
<tr>
<th class="th"><div>Jan. 31, 2017</div></th>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Dec. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems', window );"><strong>Share Based Compensation Arrangement By Share Based Payment Award [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription', window );">Share based compensation, description</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">These Plans are administered by the board of directors or, at the discretion of the board of directors, by a committee of the board of directors. The exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, or its committee if so delegated, except that the exercise price per share of stock options may not be less than 100% of the fair market value of the share of common stock on the date of grant and the term of the stock option may not be greater than ten years.<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights', window );">Vesting rights, descriptions</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Incentive  stock options granted to employees and restricted stock awards granted to  employees, officers, members of the board of directors, advisors, and  consultants of the Company typically vest over four years. Non-statutory options  granted to employees, officers, members of the board of directors, advisors, and  consultants of the Company typically vest over three or four years.<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1', window );">Number of share options exercisable, aggregate intrinsic Value</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 123<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardsGrantInPeriodWeightedAverageGrantDateFairValue', window );">Options granted, weighted average grant date fair value</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 12.88<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross', window );">Stock-based compensation arrangement, number of options granted to purchase shares</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">136,913<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized', window );">Unrecognized compensation cost of stock based awards</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 5,066<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1', window );">Unrecognized compensation cost of stock based awards, recognition period</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">2 years 6 months<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_EmployeeStockOwnershipPlanESOPDisclosuresByPlanAxis=xfor_EmployeeStockPurchasePlansMember', window );">2017 Employee Stock Purchase Plan [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems', window );"><strong>Share Based Compensation Arrangement By Share Based Payment Award [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod', window );">Shares of common stock issued</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PlanNameAxis=xfor_TwoThousandFifteenEquityIncentivePlanMember', window );">2015 Equity Incentive Plan [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems', window );"><strong>Share Based Compensation Arrangement By Share Based Payment Award [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized', window );">Ordinary share issued</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">1,700,000<span></span>
</td>
<td class="nump">1,700,000<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PlanNameAxis=xfor_TwoThousandSeventeenEquityIncentivePlanMember', window );">2017 Equity Incentive Plan [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems', window );"><strong>Share Based Compensation Arrangement By Share Based Payment Award [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized', window );">Ordinary share issued</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">1,025,490<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CommonStockReservedForIssuanceDescription', window );">Common stock reserved for future issuance, description</a></td>
<td class="text">The number of shares of common stock reserved for issuance under  this plan will automatically increase on January 1 of each year, through  January 1, 2027, in an amount equal to the lowest of 1,025,490 shares of the  Company's common stock, 4% of the number of shares of the Company's common stock  outstanding on January 1 of each year and an amount determined by the Company's  board of directors.<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum', window );">Percentage of number of common stock outstanding</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">4.00%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Unrecognized cost of unvested share-based compensation awards.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (i)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (i)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:durationItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Description of award terms as to how many shares or portion of an award are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, to sell the shares, and be entitled to the cash proceeds of such sale. For example, vesting may be expressed as being 25 percent of the shares under option on each anniversary of the grant date.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (a)(1)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>General descriptive information regarding an arrangement under which employees and directors receive: (a) awards of equity shares, equity share options, or other equity instruments; or (b) the entity incurs liabilities to them: (1) in amounts based, at least in part, on the price of the entity's shares or other equity instruments; or (2) that require or may require settlement by issuance of the entity's shares. Such an arrangement is usually provided to employees and directors to compensate them, provide performance incentives to them, and to attract or retain their services. May also include pertinent information particular to a plan that is not elsewhere specified in the taxonomy.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5047-113901<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (a)(3)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Gross number of share options (or share units) granted during the period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Maximum number of shares that may be issued in accordance with the plan as a proportion of outstanding capital stock.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum</td>
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<td><strong> Data Type:</strong></td>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
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</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of share instruments newly issued under a share-based compensation plan.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td><strong> Period Type:</strong></td>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Common Stock Reserved For Issuance Description</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Share Based Compensation Arrangement By Share Based Payment Award Awards Grant in Period Weighted Average Grant Date Fair Value</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
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<td style="white-space:nowrap;">xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardsGrantInPeriodWeightedAverageGrantDateFairValue</td>
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<td>xfor_</td>
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<td>num:perShareItemType</td>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
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<td><strong> Period Type:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_EmployeeStockOwnershipPlanESOPDisclosuresByPlanAxis=xfor_EmployeeStockPurchasePlansMember</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PlanNameAxis=xfor_TwoThousandFifteenEquityIncentivePlanMember</td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_PlanNameAxis=xfor_TwoThousandSeventeenEquityIncentivePlanMember</td>
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<TYPE>XML
<SEQUENCE>82
<FILENAME>R66.htm
<DESCRIPTION>IDEA: XBRL DOCUMENT
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<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
<script type="text/javascript" src="Show.js">/* Do Not Remove This Comment */</script><script type="text/javascript">
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6661043984">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Stock-Based Compensation - Schedule of Assumptions Used in Black-Scholes Option-Pricing Model to Determine Grant-date Fair Value of Stock Options Granted (Detail)<br></strong></div></th>
<th class="th" colspan="2">3 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Mar. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_SharebasedCompensationArrangementBySharebasedPaymentAwardStockOptionsSharesOutstandingWeightedAverageExercisePriceAndAdditionalDisclosuresAbstract', window );"><strong>Share-based Compensation Arrangement by Share-based Payment Award, Stock Options/Shares Outstanding, Weighted-Average Exercise Price, and Additional Disclosures [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate', window );">Risk-free interest rate</a></td>
<td class="nump">2.40%<span></span>
</td>
<td class="nump">2.80%<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1', window );">Expected term (in years)</a></td>
<td class="text">5 years 10 months 24 days<span></span>
</td>
<td class="text">5 years 11 months 8 days<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate', window );">Expected volatility</a></td>
<td class="nump">90.60%<span></span>
</td>
<td class="nump">86.00%<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate', window );">Expected dividend yield</a></td>
<td class="nump">0.00%<span></span>
</td>
<td class="nump">0.00%<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (f)(2)(iii)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (f)(2)(ii)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The risk-free interest rate assumption that is used in valuing an option on its own shares.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (f)(2)(iv)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (f)(2)(i)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SAB Topic 14.D.2)<br> -URI http://asc.fasb.org/extlink&amp;oid=115993241&amp;loc=d3e301413-122809<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:durationItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_SharebasedCompensationArrangementBySharebasedPaymentAwardStockOptionsSharesOutstandingWeightedAverageExercisePriceAndAdditionalDisclosuresAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Share-based compensation arrangement by share-based payment award, stock options/shares outstanding, weighted-average exercise price, and additional disclosures.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_SharebasedCompensationArrangementBySharebasedPaymentAwardStockOptionsSharesOutstandingWeightedAverageExercisePriceAndAdditionalDisclosuresAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
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<DOCUMENT>
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<head>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6825602176">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($)<br> $ / shares in Units, $ in Thousands</strong></div></th>
<th class="th" colspan="1">3 Months Ended</th>
<th class="th" colspan="1">12 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Dec. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract', window );"><strong>Disclosure of Compensation Related Costs, Share-based Payments [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber', window );">Number of shares outstanding, Beginning balance</a></td>
<td class="nump">797,931<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAcquiredInReverseMerger', window );">Number of shares, Assumed as part of merger with Arsanis</a></td>
<td class="nump">271,230<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross', window );">Number of shares, Granted</a></td>
<td class="nump">136,913<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised', window );">Number of shares, Exercised</a></td>
<td class="num">(16,483)<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod', window );">Number of shares, Forfeited</a></td>
<td class="num">(22,378)<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber', window );">Number of shares Outstanding, Ending balance</a></td>
<td class="nump">1,167,213<span></span>
</td>
<td class="nump">797,931<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber', window );">Number of shares Options, Exercisable</a></td>
<td class="nump">556,774<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber', window );">Number of shares Options, Vested and expected to vest</a></td>
<td class="nump">979,466<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice', window );">Weighted average exercise price, Beginning balance</a></td>
<td class="nump">$ 8.29<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAcquiredInReverseMergerWeightedAverageExercisePrice', window );">Weighted average exercise price, Assumed as part of merger with Arsanis</a></td>
<td class="nump">62.60<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice', window );">Weighted average exercise price, Granted</a></td>
<td class="nump">17.22<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice', window );">Weighted average exercise price, Exercised</a></td>
<td class="nump">6.85<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice', window );">Weighted average exercise price, Forfeited</a></td>
<td class="nump">8.43<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice', window );">Weighted average exercise price, Ending balance</a></td>
<td class="nump">21.97<span></span>
</td>
<td class="nump">$ 8.29<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice', window );">Weighted average exercise price, Exercisable</a></td>
<td class="nump">30.13<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice', window );">Weighted average exercise price, Vested and expected to vest</a></td>
<td class="nump">$ 48.79<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2', window );">Weighted average contractual term outstanding, Beginning balance</a></td>
<td class="text">7 years 7 months 24 days<span></span>
</td>
<td class="text">8 years 5 months 1 day<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue', window );">Aggregate intrinsic value, Beginning balance</a></td>
<td class="nump">$ 6,486<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue', window );">Aggregate intrinsic value, Exercised</a></td>
<td class="nump">0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue', window );">Aggregate intrinsic value, Ending balance</a></td>
<td class="nump">$ 7,168<span></span>
</td>
<td class="nump">$ 6,486<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (c)(1)(iii)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (c)(1)(iii)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (d)(2)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (c)(1)(iv)(3)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Gross number of share options (or share units) granted during the period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of options outstanding, including both vested and non-vested options.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (c)(1)(i)-(ii)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
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</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (c)(1)(i)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
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</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (e)(2)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (e)(1)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Weighted average price at which option holders acquired shares when converting their stock options into shares.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (e)(1)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:durationItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of share options (or share units) exercised during the current period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (c)(1)(iv)(2)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(28))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21463-112644<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
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<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Share based compensation arrangement by share based payment award options acquired in reverse merger.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAcquiredInReverseMerger</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAcquiredInReverseMergerWeightedAverageExercisePrice">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Share based compensation arrangement by share based payment award options acquired in reverse merger weighted average exercise price.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAcquiredInReverseMergerWeightedAverageExercisePrice</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
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<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
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<td><strong> Period Type:</strong></td>
<td>duration</td>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6798149056">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Stock-Based Compensation - Summary of Stock-Based Compensation Expense Classification (Detail) - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th" colspan="2">3 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Mar. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems', window );"><strong>Share Based Compensation Arrangement By Share Based Payment Award [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AllocatedShareBasedCompensationExpense', window );">Stock-based compensation expense</a></td>
<td class="nump">$ 262<span></span>
</td>
<td class="nump">$ 128<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_IncomeStatementLocationAxis=us-gaap_ResearchAndDevelopmentExpenseMember', window );">Research and Development Expenses [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems', window );"><strong>Share Based Compensation Arrangement By Share Based Payment Award [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AllocatedShareBasedCompensationExpense', window );">Stock-based compensation expense</a></td>
<td class="nump">84<span></span>
</td>
<td class="nump">38<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_IncomeStatementLocationAxis=us-gaap_GeneralAndAdministrativeExpenseMember', window );">General and Administrative Expenses [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems', window );"><strong>Share Based Compensation Arrangement By Share Based Payment Award [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AllocatedShareBasedCompensationExpense', window );">Stock-based compensation expense</a></td>
<td class="nump">$ 178<span></span>
</td>
<td class="nump">$ 90<span></span>
</td>
</tr>
</table>
<div style="display: none;">
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5047-113901<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SAB Topic 14.F)<br> -URI http://asc.fasb.org/extlink&amp;oid=115993241&amp;loc=d3e301413-122809<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 718<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -Subparagraph (h)(1)(i)<br> -URI http://asc.fasb.org/extlink&amp;oid=109197908&amp;loc=d3e5070-113901<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AllocatedShareBasedCompensationExpense</td>
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<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td>xbrli:monetaryItemType</td>
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<td><strong> Balance Type:</strong></td>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<td>xbrli:stringItemType</td>
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<td>na</td>
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<td>duration</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<td><strong> Data Type:</strong></td>
<td>na</td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6841134672">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>License, Collaboration, and Funding Agreements - Additional Information (Detail) - USD ($)<br></strong></div></th>
<th class="th" colspan="1"></th>
<th class="th" colspan="3">1 Months Ended</th>
<th class="th" colspan="3">3 Months Ended</th>
<th class="th" colspan="1">12 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Oct. 31, 2018</div></th>
<th class="th"><div>Feb. 28, 2017</div></th>
<th class="th"><div>Dec. 31, 2016</div></th>
<th class="th"><div>Aug. 31, 2014</div></th>
<th class="th"><div>Dec. 31, 2019</div></th>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Mar. 31, 2018</div></th>
<th class="th"><div>Dec. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CollaborationLicenseAndFundingArrangementsLineItems', window );"><strong>Collaboration License And Funding Arrangements [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_UpfrontPayments', window );">Upfront payments</a></td>
<td class="nump">$ 92,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodSharesNewIssues', window );">Common Stock issued</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">22,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodValueNewIssues', window );">Research and Development Expense</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ResearchAndDevelopmentExpense', window );">Research and development expense</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 5,655,000<span></span>
</td>
<td class="nump">4,744,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_srt_StatementGeographicalAxis=exch_MTSA', window );">AUSTRIA [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CollaborationLicenseAndFundingArrangementsLineItems', window );"><strong>Collaboration License And Funding Arrangements [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ReimbursementRateForResearchAndDevelopment', window );">Grant income</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">14.00%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_GenzymeAgreementMember', window );">Genzyme Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CollaborationLicenseAndFundingArrangementsLineItems', window );"><strong>Collaboration License And Funding Arrangements [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_UpfrontPayments', window );">Upfront payments</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 50,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment', window );">Cash payment</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 300,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodSharesNewIssues', window );">Common Stock issued</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">107,371<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockholdersEquityReverseStockSplit', window );">Equity reverse stock split</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Adjusted for the 6 for 1 reverse stock split and exchange ratio<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodValueNewIssues', window );">Research and Development Expense</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 734,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SaleOfStockPricePerShare', window );">Shares issued price per share</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 0.01<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_MilestonePayments', window );">Future milestone payments</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 25,000,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ConsiderationToEquityShareholders', window );">Consideration paid to equity shareholders</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">5.50%<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_DerivativeLiabilities', window );">Derivative Liability</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 183,000<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_LicenseAgreementTerminationDescription', window );">License agreement termination description</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">The agreement may be terminated  by either party with at least 90 days' notice in the event of material breach by  the other party that remains uncured for 90 days, by either party for insolvency  or bankruptcy of the other party, immediately by Genzyme if the Company  challenges the licensed patents, or immediately by the Company if a material  safety issue arises.<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_PaymentOnObligationUnderLicenseAgreement', window );">Payment on obligation under license agreement</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
<td class="nump">0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_MilestonePaymentObligation', window );">Milestone payment obligation</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">0<span></span>
</td>
<td class="nump">0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_GeorgetownAgreementMember', window );">Georgetown Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CollaborationLicenseAndFundingArrangementsLineItems', window );"><strong>Collaboration License And Funding Arrangements [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_LicenseAgreementTerminationDescription', window );">License agreement termination description</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">The event (i) the Company fails to pay any amount and  fails to cure such failure within 30 days after receipt of notice, (ii) the  Company defaults in its obligation to obtain and maintain insurance and fails to  remedy such breach within 45 days after receipt of notice, or (iii) the Company  declares insolvency or bankruptcy. The Company may terminate the agreement at  any time upon at least 60 days' written notice.<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_PaymentOnObligationUnderLicenseAgreement', window );">Payment on obligation under license agreement</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">0<span></span>
</td>
<td class="nump">0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_MilestonePaymentObligation', window );">Milestone payment obligation</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">0<span></span>
</td>
<td class="nump">0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_OneTimeUpfrontPayment', window );">One time upfront payment</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 50,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_MilestonePaymentsPaid', window );">Milestone payments</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">800,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_BidmcAgreementMember', window );">BIDMC Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CollaborationLicenseAndFundingArrangementsLineItems', window );"><strong>Collaboration License And Funding Arrangements [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_LicenseAgreementTerminationDescription', window );">License agreement termination description</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">The event (i) the Company fails to pay any amount and  fails to cure such failure within 15 days after receipt of notice, (ii) the  Company is in material breach of any material provision of the agreement and  fails to remedy such breach within 60 days after receipt of notice, or (iii) the  Company declares insolvency or bankruptcy. We may terminate the agreement at any  time upon at least 90 days' written notice.<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_PaymentOnObligationUnderLicenseAgreement', window );">Payment on obligation under license agreement</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">0<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_OneTimeUpfrontPayment', window );">One time upfront payment</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 20,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_AdimabOptionAgreementMember', window );">Adimab Option Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CollaborationLicenseAndFundingArrangementsLineItems', window );"><strong>Collaboration License And Funding Arrangements [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_MilestonePayments', window );">Future milestone payments</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 25,000,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_OptionFee', window );">Option fee</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">250,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_AdimabOptionAgreementMember', window );">Adimab Option Agreement [Member] | Adimab, LLC [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CollaborationLicenseAndFundingArrangementsLineItems', window );"><strong>Collaboration License And Funding Arrangements [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_MilestonePayments', window );">Future milestone payments</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">24,400,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_OptionFee', window );">Option fee</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">300,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ResearchAndDevelopmentExpense', window );">Research and development expense</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_AdimabCollaborationAgreementMember', window );">Adimab Collaboration Agreement | Adimab, LLC [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CollaborationLicenseAndFundingArrangementsLineItems', window );"><strong>Collaboration License And Funding Arrangements [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ResearchAndDevelopmentExpense', window );">Research and development expense</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_ResearchAndDevelopmentIncentiveProgramMember', window );">Research and Development Incentive [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CollaborationLicenseAndFundingArrangementsLineItems', window );"><strong>Collaboration License And Funding Arrangements [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_GrantAndIncentiveReceivables', window );">Grant receivable</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">1,600,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_GrantAgreementMember', window );">Grant Agreement [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CollaborationLicenseAndFundingArrangementsLineItems', window );"><strong>Collaboration License And Funding Arrangements [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_QualifyingExpensesUnderLetterAgreement', window );">Qualifying expenses related to letter agreement</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_FebruaryTwoThousandAndSeventeenGrantAgreementMember', window );">February 2017 Grant Agreement | Gates Foundation [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CollaborationLicenseAndFundingArrangementsLineItems', window );"><strong>Collaboration License And Funding Arrangements [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_GrantsAgreementMaximumAwardAmount', window );">Grant receivable</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 9,300,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_JanssenLicenseAndOptionAgreementMember', window );">Janssen License and Option Agreement [Member] | Janssen Pharmaceuticals Incorporation [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CollaborationLicenseAndFundingArrangementsLineItems', window );"><strong>Collaboration License And Funding Arrangements [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AccountsReceivableRelatedParties', window );">Payables from related parties</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">3,500,000<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax', window );">Payment received from related parties</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 3,500,000<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CollaborativeArrangementRightsAndObligations', window );">License and options agreement description</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">Pursuant to the Janssen License and Option Agreement, Arsanis granted to Janssen (i) a non-exclusive license to specified patents in Arsanis&#8217;s portfolio related to the ASN200 E. coli program, and (ii) an option for Janssen to acquire these patents in the future if specified conditions are met. Janssen agreed to pay Arsanis $3.5 million within 15 business days after the December 12, 2018 effective date of the Janssen License and Option Agreement, in addition to a future $0.5 million payment in the event Janssen exercises its option to acquire the relevant patents. Arsanis received the $3.5 million payment from Janssen in December 2018.<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TypeOfArrangementAxis=xfor_JanssenLicenseAndOptionAgreementMember', window );">Janssen License and Option Agreement [Member] | Janssen Pharmaceuticals Incorporation [Member] | Patents [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_CollaborationLicenseAndFundingArrangementsLineItems', window );"><strong>Collaboration License And Funding Arrangements [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ProceedsFromSaleOfIntangibleAssets', window );">Option to acquire the relevant patents</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">$ 500,000<span></span>
</td>
</tr>
</table>
<div style="display: none;">
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>For an unclassified balance sheet, amount of receivables arising from transactions with related parties.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 850<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (d)<br> -URI http://asc.fasb.org/extlink&amp;oid=6457730&amp;loc=d3e39549-107864<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 850<br> -SubTopic 10<br> -Section 50<br> -Paragraph 4<br> -URI http://asc.fasb.org/extlink&amp;oid=6457730&amp;loc=d3e39622-107864<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 944<br> -SubTopic 210<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.7-03(a)(3))<br> -URI http://asc.fasb.org/extlink&amp;oid=6879938&amp;loc=d3e572229-122910<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 850<br> -SubTopic 10<br> -Section 50<br> -Paragraph 3<br> -URI http://asc.fasb.org/extlink&amp;oid=6457730&amp;loc=d3e39603-107864<br><br>Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(3)(a)(2))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.4-08(k)(1))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e23780-122690<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Description of rights and obligations under the collaborative arrangements.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 808<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=6931272&amp;loc=SL5834143-161434<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 20<br> -Section 50<br> -Paragraph 3<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=51824906&amp;loc=SL20225862-175312<br><br>Reference 2: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 825<br> -SubTopic 10<br> -Section 50<br> -Paragraph 10<br> -URI http://asc.fasb.org/extlink&amp;oid=109250915&amp;loc=d3e13433-108611<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 20<br> -Section 55<br> -Paragraph 10<br> -URI http://asc.fasb.org/extlink&amp;oid=99393222&amp;loc=SL20226008-175313<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The cash outflows from the purchase of net carrying value allocated to in-process research and development costs and materials acquired in a business combination.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 13<br> -Subparagraph (b)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3213-108585<br></p></div>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The cash inflow from disposal of asset without physical form usually arising from contractual or other legal rights, excluding goodwill.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 12<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3179-108585<br></p></div>
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<tr>
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<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ResearchAndDevelopmentExpense">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 985<br> -SubTopic 20<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6501960&amp;loc=d3e128462-111756<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 730<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6420194&amp;loc=d3e21568-108373<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ResearchAndDevelopmentExpense</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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</tr>
<tr>
<td><strong> Balance Type:</strong></td>
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<tr>
<td><strong> Period Type:</strong></td>
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</tr>
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</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 606<br> -SubTopic 10<br> -Section 50<br> -Paragraph 4<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=109196051&amp;loc=SL49130543-203045<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 606<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=109196051&amp;loc=SL49130539-203045<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 606<br> -SubTopic 10<br> -Section 50<br> -Paragraph 5<br> -URI http://asc.fasb.org/extlink&amp;oid=109196051&amp;loc=SL49130545-203045<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<tr>
<td><strong> Data Type:</strong></td>
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</tr>
<tr>
<td><strong> Balance Type:</strong></td>
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<tr>
<td><strong> Period Type:</strong></td>
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</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_SaleOfStockPricePerShare">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_SaleOfStockPricePerShare</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockIssuedDuringPeriodSharesNewIssues">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of new stock issued during the period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21463-112644<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(28))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockIssuedDuringPeriodSharesNewIssues</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockIssuedDuringPeriodValueNewIssues">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21463-112644<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(28))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockIssuedDuringPeriodValueNewIssues</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
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</tr>
<tr>
<td><strong> Period Type:</strong></td>
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</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockholdersEquityReverseStockSplit">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Description of the reverse stock split arrangement. Also provide the retroactive effect given by the reverse split that occurs after the balance sheet date but before the release of financial statements.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 4<br> -Subparagraph (SAB Topic 4.C)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187143-122770<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockholdersEquityReverseStockSplit</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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</tr>
<tr>
<td><strong> Data Type:</strong></td>
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<td><strong> Balance Type:</strong></td>
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<tr>
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</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_CollaborationLicenseAndFundingArrangementsLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Collaboration, license and funding arrangements.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_CollaborationLicenseAndFundingArrangementsLineItems</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
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</tr>
<tr>
<td><strong> Balance Type:</strong></td>
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</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ConsiderationToEquityShareholders">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Consideration to equity shareholders.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ConsiderationToEquityShareholders</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_GrantAndIncentiveReceivables">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Grant and incentive receivables.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_GrantAndIncentiveReceivables</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_GrantsAgreementMaximumAwardAmount">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Grants agreement maximum award amount.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_GrantsAgreementMaximumAwardAmount</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_LicenseAgreementTerminationDescription">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>License Agreement, Termination Description</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_LicenseAgreementTerminationDescription</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_MilestonePaymentObligation">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Milestone Payment Obligation</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_MilestonePaymentObligation</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_MilestonePayments">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Milestone payments.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_MilestonePayments</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_MilestonePaymentsPaid">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Milestone Payments Paid</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_MilestonePaymentsPaid</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_OneTimeUpfrontPayment">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>One Time Upfront Payment</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_OneTimeUpfrontPayment</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_OptionFee">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Option fee.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_OptionFee</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_PaymentOnObligationUnderLicenseAgreement">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Payment On Obligation Under License Agreement</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_PaymentOnObligationUnderLicenseAgreement</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_QualifyingExpensesUnderLetterAgreement">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Qualifying expenses under the letter agreement.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_QualifyingExpensesUnderLetterAgreement</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ReimbursementRateForResearchAndDevelopment">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Reimbursement rate for research and development expenses.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ReimbursementRateForResearchAndDevelopment</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:percentItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_UpfrontPayments">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Upfront payments</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_UpfrontPayments</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_srt_StatementGeographicalAxis=exch_MTSA">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">srt_StatementGeographicalAxis=exch_MTSA</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TypeOfArrangementAxis=xfor_GenzymeAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TypeOfArrangementAxis=xfor_GenzymeAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TypeOfArrangementAxis=xfor_GeorgetownAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TypeOfArrangementAxis=xfor_GeorgetownAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TypeOfArrangementAxis=xfor_BidmcAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TypeOfArrangementAxis=xfor_BidmcAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TypeOfArrangementAxis=xfor_AdimabOptionAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TypeOfArrangementAxis=xfor_AdimabOptionAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=xfor_AdimabLLCMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=xfor_AdimabLLCMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TypeOfArrangementAxis=xfor_AdimabCollaborationAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TypeOfArrangementAxis=xfor_AdimabCollaborationAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TypeOfArrangementAxis=xfor_ResearchAndDevelopmentIncentiveProgramMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TypeOfArrangementAxis=xfor_ResearchAndDevelopmentIncentiveProgramMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TypeOfArrangementAxis=xfor_GrantAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TypeOfArrangementAxis=xfor_GrantAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TypeOfArrangementAxis=xfor_FebruaryTwoThousandAndSeventeenGrantAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TypeOfArrangementAxis=xfor_FebruaryTwoThousandAndSeventeenGrantAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_srt_CounterpartyNameAxis=xfor_BillAndMelindaGatesFoundationMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">srt_CounterpartyNameAxis=xfor_BillAndMelindaGatesFoundationMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_TypeOfArrangementAxis=xfor_JanssenLicenseAndOptionAgreementMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_TypeOfArrangementAxis=xfor_JanssenLicenseAndOptionAgreementMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=xfor_JanssenPharmaceuticalsIncorporationMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=xfor_JanssenPharmaceuticalsIncorporationMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_PatentsMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_PatentsMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
</div>
</body>
</html>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>XML
<SEQUENCE>86
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<TEXT>
<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
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<body>
<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6775904736">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Income Taxes - Additional Information (Detail) - USD ($)<br> $ in Thousands</strong></div></th>
<th class="th" colspan="2">3 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Mar. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_IncomeTaxDisclosureAbstract', window );"><strong>Income Tax Disclosure [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CurrentFederalTaxExpenseBenefit', window );">Federal income tax benefit</a></td>
<td class="nump">$ 0<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_CurrentStateAndLocalTaxExpenseBenefit', window );">State income tax benefit</a></td>
<td class="nump">$ 0<span></span>
</td>
<td class="nump">$ 0<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CurrentFederalTaxExpenseBenefit">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of current federal tax expense (benefit) pertaining to income (loss) from continuing operations.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 740<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SAB Topic 6.I.7)<br> -URI http://asc.fasb.org/extlink&amp;oid=34349781&amp;loc=d3e330036-122817<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.4-08(h))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e23780-122690<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 740<br> -SubTopic 10<br> -Section 50<br> -Paragraph 9<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=84230637&amp;loc=d3e32639-109319<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CurrentFederalTaxExpenseBenefit</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_CurrentStateAndLocalTaxExpenseBenefit">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of current state and local tax expense (benefit) pertaining to income (loss) from continuing operations.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.4-08(h))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e23780-122690<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 740<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SAB Topic 6.I.7)<br> -URI http://asc.fasb.org/extlink&amp;oid=34349781&amp;loc=d3e330036-122817<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 740<br> -SubTopic 10<br> -Section 50<br> -Paragraph 9<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=84230637&amp;loc=d3e32639-109319<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_CurrentStateAndLocalTaxExpenseBenefit</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_IncomeTaxDisclosureAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_IncomeTaxDisclosureAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
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<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
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</table></div>
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</div>
</body>
</html>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>XML
<SEQUENCE>87
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<TEXT>
<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
<script type="text/javascript" src="Show.js">/* Do Not Remove This Comment */</script><script type="text/javascript">
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</head>
<body>
<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6820052912">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Net Loss per Share - Summary of Basic and Diluted Net loss per Share Attributable to Common Stockholders (Detail) - USD ($)<br> $ / shares in Units, $ in Thousands</strong></div></th>
<th class="th" colspan="2">3 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Mar. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_IncomeStatementAbstract', window );"><strong>Numerator:</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NetIncomeLoss', window );">Net loss</a></td>
<td class="num">$ (10,873)<span></span>
</td>
<td class="num">$ (7,367)<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment', window );">Accruing dividends on Series A convertible preferred stock</a></td>
<td class="num">(592)<span></span>
</td>
<td class="num">(740)<span></span>
</td>
</tr>
<tr class="rou">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic', window );">Net loss attributable to common stockholders</a></td>
<td class="num">$ (11,465)<span></span>
</td>
<td class="num">$ (8,107)<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted', window );">Weighted average common shares outstanding-basic and diluted</a></td>
<td class="nump">1,717,808<span></span>
</td>
<td class="nump">457,971<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_EarningsPerShareBasicAndDiluted', window );">Net loss per share attributable to common stockholders-basic and diluted</a></td>
<td class="num">$ (6.67)<span></span>
</td>
<td class="num">$ (17.70)<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_EarningsPerShareBasicAndDiluted">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements.  Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period.  Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 260<br> -SubTopic 10<br> -Section 45<br> -Paragraph 7<br> -URI http://asc.fasb.org/extlink&amp;oid=109260490&amp;loc=d3e1337-109256<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_EarningsPerShareBasicAndDiluted</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_IncomeStatementAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- References</a><div><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_IncomeStatementAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_NetIncomeLoss">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1A<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669619-108580<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 942<br> -SubTopic 220<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.9-04(22))<br> -URI http://asc.fasb.org/extlink&amp;oid=114873765&amp;loc=SL114874048-224260<br><br>Reference 3: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section 45<br> -Paragraph 1B<br> -Subparagraph (a)<br> -URI http://asc.fasb.org/extlink&amp;oid=114867106&amp;loc=SL7669625-108580<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 944<br> -SubTopic 220<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.7-04(18))<br> -URI http://asc.fasb.org/extlink&amp;oid=114873790&amp;loc=SL114874131-224263<br><br>Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 220<br> -SubTopic 10<br> -Section S99<br> -Paragraph 2<br> -Subparagraph (SX 210.5-03(20))<br> -URI http://asc.fasb.org/extlink&amp;oid=115205541&amp;loc=SL114868664-224227<br><br>Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 230<br> -SubTopic 10<br> -Section 45<br> -Paragraph 28<br> -URI http://asc.fasb.org/extlink&amp;oid=109223946&amp;loc=d3e3602-108585<br><br>Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 260<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -URI http://asc.fasb.org/extlink&amp;oid=6371337&amp;loc=d3e3550-109257<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_NetIncomeLoss</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>credit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/disclosureRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 250<br> -SubTopic 10<br> -Section 50<br> -Paragraph 11<br> -URI http://asc.fasb.org/extlink&amp;oid=109234566&amp;loc=d3e22694-107794<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 260<br> -SubTopic 10<br> -Section 45<br> -Paragraph 11<br> -URI http://asc.fasb.org/extlink&amp;oid=109260490&amp;loc=d3e1377-109256<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Amount of decrease to net income for accretion of temporary equity to its redemption value to derive net income apportioned to common stockholders.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<td>duration</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted</td>
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<tr>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
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<td><strong> Period Type:</strong></td>
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<head>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6825093456">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Net Loss per Share - Additional Information (Detail) - shares<br></strong></div></th>
<th class="th" colspan="2">3 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Mar. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_EarningsPerShareBasicLineItems', window );"><strong>Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
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<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted', window );">Redeemable common stock</a></td>
<td class="nump">1,717,808<span></span>
</td>
<td class="nump">457,971<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=xfor_RedeemableCommonStockMember', window );">Redeemable Common Stock [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
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<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_EarningsPerShareBasicLineItems', window );"><strong>Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
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<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted', window );">Redeemable common stock</a></td>
<td class="nump">107,371<span></span>
</td>
<td class="nump">107,371<span></span>
</td>
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<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_EarningsPerShareBasicLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
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<td>na</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted</td>
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<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
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<td>na</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementClassOfStockAxis=xfor_RedeemableCommonStockMember</td>
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<TYPE>XML
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<FILENAME>R73.htm
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="report.css">
<script type="text/javascript" src="Show.js">/* Do Not Remove This Comment */</script><script type="text/javascript">
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<body>
<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6819472048">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Net Loss per Share - Schedule of Anti-dilutive Securities Excluded from Computation of Diluted Net Loss per Share Attributable to Common Stockholders (Detail) - shares<br></strong></div></th>
<th class="th" colspan="2">3 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Mar. 31, 2019</div></th>
<th class="th"><div>Mar. 31, 2018</div></th>
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<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems', window );"><strong>Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
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<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount', window );">Anti-dilutive securities excluded from computation of diluted net loss per share</a></td>
<td class="nump">1,531,016<span></span>
</td>
<td class="nump">4,517,992<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis=us-gaap_EmployeeStockOptionMember', window );">Employee Stock Option [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems', window );"><strong>Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount', window );">Anti-dilutive securities excluded from computation of diluted net loss per share</a></td>
<td class="nump">1,037,089<span></span>
</td>
<td class="nump">538,429<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis=us-gaap_WarrantMember', window );">Warrant [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems', window );"><strong>Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount', window );">Anti-dilutive securities excluded from computation of diluted net loss per share</a></td>
<td class="nump">493,927<span></span>
</td>
<td class="nump">423,416<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementClassOfStockAxis=us-gaap_ConvertiblePreferredStockMember', window );">Convertible Preferred Stock [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems', window );"><strong>Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount', window );">Anti-dilutive securities excluded from computation of diluted net loss per share</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">3,556,147<span></span>
</td>
</tr>
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<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 260<br> -SubTopic 10<br> -Section 50<br> -Paragraph 1<br> -Subparagraph (c)<br> -URI http://asc.fasb.org/extlink&amp;oid=6371337&amp;loc=d3e3550-109257<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount</td>
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<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
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<td><strong> Balance Type:</strong></td>
<td>na</td>
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<td>duration</td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems</td>
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<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis=us-gaap_EmployeeStockOptionMember</td>
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<td><strong> Data Type:</strong></td>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis=us-gaap_WarrantMember</td>
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<td><strong> Data Type:</strong></td>
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<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
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<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementClassOfStockAxis=us-gaap_ConvertiblePreferredStockMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
</div>
</body>
</html>
</TEXT>
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<DOCUMENT>
<TYPE>XML
<SEQUENCE>90
<FILENAME>R74.htm
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
<html>
<head>
<title></title>
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<span style="display: none;">v3.19.1</span><table class="report" border="0" cellspacing="2" id="idp6826502080">
<tr>
<th class="tl" colspan="1" rowspan="2"><div style="width: 200px;"><strong>Subsequent Events - Additional Information (Detail) - USD ($)<br> $ / shares in Units, $ in Millions</strong></div></th>
<th class="th" colspan="1"></th>
<th class="th" colspan="1">3 Months Ended</th>
</tr>
<tr>
<th class="th"><div>Apr. 12, 2019</div></th>
<th class="th"><div>Mar. 31, 2018</div></th>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SubsequentEventLineItems', window );"><strong>Subsequent Event [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodSharesNewIssues', window );">Stock issued during period, shares, new issues</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="nump">22,000<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember', window );">Subsequent Event [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SubsequentEventLineItems', window );"><strong>Subsequent Event [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StockIssuedDuringPeriodSharesNewIssues', window );">Stock issued during period, shares, new issues</a></td>
<td class="nump">5,670,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SaleOfStockPricePerShare', window );">Sale of stock, price per share</a></td>
<td class="nump">$ 11<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ProceedsFromIssuanceOfCommonStockBeforeUnderwritingDiscountsCommissionsAndOtherExpenses', window );">Proceeds from issuance common stock before underwriters discounts and commissions and offering expenses</a></td>
<td class="nump">$ 85.8<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementEquityComponentsAxis=xfor_PreFundedWarrantMember', window );">Pre Funded Warrant [Member] | Subsequent Event [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SubsequentEventLineItems', window );"><strong>Subsequent Event [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights', window );">Class of warrant or right, warrants to purchase of common stock</a></td>
<td class="nump">2,130,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Class of warrant or right, exercise price of warrants or rights</a></td>
<td class="nump">$ 10.999<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="rh">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_StatementEquityComponentsAxis=xfor_ClassAWarrantMember', window );">Class A Warrant [Member] | Subsequent Event [Member]</a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_SubsequentEventLineItems', window );"><strong>Subsequent Event [Line Items]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights', window );">Class of warrant or right, warrants to purchase of common stock</a></td>
<td class="nump">3,900,000<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="re">
<td class="pl " style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1', window );">Class of warrant or right, exercise price of warrants or rights</a></td>
<td class="nump">$ 13.20<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl custom" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="top.Show.showAR( this, 'defref_xfor_ClassOfWarrantOrRightWarrantsExpirationPeriod', window );">Class of warrants or rights expiration period</a></td>
<td class="text">5 years<span></span>
</td>
<td class="text">&#160;<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Exercise price per share or per unit of warrants or rights outstanding.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.4-08.(i)(4))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e23780-122690<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 235<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.4-08.(i)(2))<br> -URI http://asc.fasb.org/extlink&amp;oid=26873400&amp;loc=d3e23780-122690<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_SaleOfStockPricePerShare">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_SaleOfStockPricePerShare</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>num:perShareItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>instant</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StockIssuedDuringPeriodSharesNewIssues">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Number of new stock issued during the period.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(29))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br><br>Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section 50<br> -Paragraph 2<br> -URI http://asc.fasb.org/extlink&amp;oid=109259400&amp;loc=d3e21463-112644<br><br>Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 505<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.3-04)<br> -URI http://asc.fasb.org/extlink&amp;oid=27012166&amp;loc=d3e187085-122770<br><br>Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef<br> -Publisher FASB<br> -Name Accounting Standards Codification<br> -Topic 210<br> -SubTopic 10<br> -Section S99<br> -Paragraph 1<br> -Subparagraph (SX 210.5-02(28))<br> -URI http://asc.fasb.org/extlink&amp;oid=6877327&amp;loc=d3e13212-122682<br></p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StockIssuedDuringPeriodSharesNewIssues</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:sharesItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_SubsequentEventLineItems">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_SubsequentEventLineItems</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>us-gaap_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ClassOfWarrantOrRightWarrantsExpirationPeriod">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Class Of Warrant Or Right Warrants Expiration Period</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ClassOfWarrantOrRightWarrantsExpirationPeriod</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:durationItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_xfor_ProceedsFromIssuanceOfCommonStockBeforeUnderwritingDiscountsCommissionsAndOtherExpenses">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Definition</a><div><p>Proceeds From Issuance Of Common Stock Before Underwriting Discounts Commissions And Other Expenses</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">xfor_ProceedsFromIssuanceOfCommonStockBeforeUnderwritingDiscountsCommissionsAndOtherExpenses</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>xfor_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:monetaryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>debit</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StatementEquityComponentsAxis=xfor_PreFundedWarrantMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementEquityComponentsAxis=xfor_PreFundedWarrantMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_us-gaap_StatementEquityComponentsAxis=xfor_ClassAWarrantMember">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="top.Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="top.Show.toggleNext( this );">- Details</a><div><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">us-gaap_StatementEquityComponentsAxis=xfor_ClassAWarrantMember</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td></td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td></td>
</tr>
</table></div>
</div></td></tr>
</table>
</div>
</body>
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</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EXCEL
<SEQUENCE>91
<FILENAME>Financial_Report.xlsx
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
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end
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
