<SEC-DOCUMENT>0000947871-21-000398.txt : 20210329
<SEC-HEADER>0000947871-21-000398.hdr.sgml : 20210329
<ACCEPTANCE-DATETIME>20210329162508
ACCESSION NUMBER:		0000947871-21-000398
CONFORMED SUBMISSION TYPE:	SC 13D/A
PUBLIC DOCUMENT COUNT:		2
FILED AS OF DATE:		20210329
DATE AS OF CHANGE:		20210329
GROUP MEMBERS:		ORBIMED CAPITAL GP VI LLC

SUBJECT COMPANY:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SYNLOGIC, INC.
		CENTRAL INDEX KEY:			0001527599
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				261824804
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		SC 13D/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	005-89131
		FILM NUMBER:		21781962

	BUSINESS ADDRESS:	
		STREET 1:		301 BINNEY STREET
		STREET 2:		SUITE 402
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02142
		BUSINESS PHONE:		617-401-9975

	MAIL ADDRESS:	
		STREET 1:		301 BINNEY STREET
		STREET 2:		SUITE 402
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02142

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Mirna Therapeutics, Inc.
		DATE OF NAME CHANGE:	20110809

FILED BY:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ORBIMED ADVISORS LLC
		CENTRAL INDEX KEY:			0001055951
		IRS NUMBER:				133976876
		STATE OF INCORPORATION:			DE

	FILING VALUES:
		FORM TYPE:		SC 13D/A

	BUSINESS ADDRESS:	
		STREET 1:		601 LEXINGTON AVENUE
		STREET 2:		54TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10022
		BUSINESS PHONE:		(212) 739-6400

	MAIL ADDRESS:	
		STREET 1:		601 LEXINGTON AVENUE
		STREET 2:		54TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10022
</SEC-HEADER>
<DOCUMENT>
<TYPE>SC 13D/A
<SEQUENCE>1
<FILENAME>ss195345_sc13da.htm
<DESCRIPTION>AMENDMENT 4
<TEXT>
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<P STYLE="margin: 0">&nbsp;</P>

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<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>UNITED STATES<BR>
SECURITIES AND EXCHANGE COMMISSION<BR>
Washington, D.C. 20549</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>SCHEDULE 13D</B><BR>
Under the Securities Exchange Act of 1934</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">(Amendment No. 4)*</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center; border-bottom: black 1.5pt solid"><B>Synlogic,
Inc.</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">(Name of Issuer)</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center; border-bottom: black 1.5pt solid"><B>Common
Stock, par value $0.001 per share</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">(Title of Class of Securities)</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>87166L100</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">(CUSIP Number)</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>OrbiMed Advisors LLC<BR>
OrbiMed Capital GP VI LLC<BR>
<BR>
</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center; border-bottom: black 1.5pt solid"><B>601 Lexington
Avenue, 54th Floor<BR>
New York, NY 10022<BR>
Telephone:&nbsp; (212) 739-6400</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">(Name, Address and Telephone Number of Person<BR>
Authorized to Receive Notices and Communications)</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center; border-bottom: black 1.5pt solid"><B>March 25,
2021</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">(Date of Event Which Requires Filing of this
Statement)</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in">If the filing person has
previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing
this schedule because of &sect; 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box &#9744;.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in">Note:&nbsp; Schedules filed
in paper format shall include a signed original and five copies of the schedule, including all exhibits.&nbsp; See &sect; 240.13d-7(b)
for other parties to whom copies are to be sent.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in">*The remainder of this
cover page shall be filled out for a reporting person&rsquo;s initial filing on this form with respect to the subject class of
securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in">The information required
on the remainder of this cover page shall not be deemed to be &ldquo;filed&rdquo; for the purpose of Section&nbsp;18 of the Securities
Exchange Act of 1934 (&ldquo;<U>Act</U>&rdquo;) or otherwise subject to the liabilities of that section of the Act but shall be
subject to all other provisions of the Act (however, see the Notes).</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

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<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0"></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 10pt 0">&nbsp;</P>

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<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 12pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR>
    <TD COLSPAN="3" STYLE="vertical-align: top; border: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt"><B>CUSIP No.&nbsp; </B>87166L100</FONT></TD>
    <TD COLSPAN="3">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD>
    <TD STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD>
    <TD COLSPAN="2" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD>
    <TD STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD>
    <TD STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">1</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">NAME OF REPORTING PERSON<BR>
OrbiMed Advisors LLC</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">2</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions)</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">(a) &#9744;</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">(b) &#9744;</P></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">3</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">SEC USE ONLY</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">4</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">SOURCE OF FUNDS (See Instructions)<BR>
AF</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">5</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e)</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">&#9744;</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">6</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">CITIZENSHIP OR PLACE OF ORGANIZATION<BR>
Delaware</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR>
    <TD COLSPAN="2" ROWSPAN="4" STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt">
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">NUMBER OF SHARES</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">BENEFICIALLY OWNED</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">BY EACH REPORTING</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">PERSON WITH</P></TD>
    <TD COLSPAN="2" STYLE="vertical-align: top; border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">7</FONT></TD>
    <TD STYLE="vertical-align: top; border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">SOLE VOTING POWER<BR>
0</FONT></TD>
    <TD STYLE="vertical-align: top; border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD COLSPAN="2" STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">8</FONT></TD>
    <TD STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">SHARED VOTING POWER</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">2,029,996</P></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD COLSPAN="2" STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">9</FONT></TD>
    <TD STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">SOLE DISPOSITIVE POWER<BR>
0</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD COLSPAN="2" STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">10</FONT></TD>
    <TD STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">SHARED DISPOSITIVE POWER</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">2,029,996</P></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">11</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">2,029,996</P></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">12</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES <BR>
(See Instructions)</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">&#9744;</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">13</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)<BR>
5.1%*</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">14</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">TYPE OF REPORTING PERSON (See Instructions)<BR>
IA</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR>
    <TD STYLE="width: 7%">&nbsp;</TD>
    <TD STYLE="width: 12%">&nbsp;</TD>
    <TD STYLE="width: 2%">&nbsp;</TD>
    <TD STYLE="width: 1%">&nbsp;</TD>
    <TD STYLE="width: 75%">&nbsp;</TD>
    <TD STYLE="width: 3%">&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</P>


<HR SIZE="1" NOSHADE ALIGN="LEFT" STYLE="width: 192px; width: 2in; color: black">

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 10pt">* This percentage is calculated based upon 39,657,841 shares
of common stock outstanding of Synlogic, Inc. (the &ldquo;Issuer&rdquo;), as set forth in the Issuer&rsquo;s Form 10-K filed with
the Securities and Exchange Commission on March 25, 2021.</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0 0 10pt">&nbsp;</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0 0 10pt">&nbsp;</P>

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<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0 0 10pt"></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0 0 10pt">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 12pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR>
    <TD COLSPAN="3" STYLE="vertical-align: top; border: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt"><B>CUSIP No. </B>87166L100</FONT></TD>
    <TD COLSPAN="3">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD>
    <TD STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD>
    <TD COLSPAN="2" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD>
    <TD STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD>
    <TD STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">1</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">NAME OF REPORTING PERSON<BR>
OrbiMed Capital GP&nbsp;VI LLC</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">2</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions)</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">(a) &#9744;</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">(b) &#9744;</P></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">3</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">SEC USE ONLY</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">4</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">SOURCE OF FUNDS (See Instructions)<BR>
AF</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">5</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e)&nbsp;</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">&#9744;</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">6</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">CITIZENSHIP OR PLACE OF ORGANIZATION<BR>
Delaware</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR>
    <TD COLSPAN="2" ROWSPAN="4" STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt">
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">NUMBER OF SHARES</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">BENEFICIALLY OWNED</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">BY EACH REPORTING</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">PERSON WITH</P></TD>
    <TD COLSPAN="2" STYLE="vertical-align: top; border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">7</FONT></TD>
    <TD STYLE="vertical-align: top; border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">SOLE VOTING POWER</FONT><BR>
<FONT STYLE="font-size: 10pt">0</FONT></TD>
    <TD STYLE="vertical-align: top; border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD COLSPAN="2" STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">8</FONT></TD>
    <TD STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">SHARED VOTING POWER&nbsp;</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">2,029,996</P></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD COLSPAN="2" STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">9</FONT></TD>
    <TD STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">SOLE DISPOSITIVE POWER</FONT><BR>
<FONT STYLE="font-size: 10pt">0</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD COLSPAN="2" STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">10</FONT></TD>
    <TD STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">SHARED DISPOSITIVE POWER</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">2,029,996</P></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">11</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt">
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">2,029,996</P></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">12</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES&nbsp; (See Instructions)</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">&#9744;</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">13</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)<BR>
5.1%*</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 3.75pt; text-align: center"><FONT STYLE="font-size: 10pt">14</FONT></TD>
    <TD COLSPAN="4" STYLE="border-bottom: black 1.5pt solid; padding: 3.75pt"><FONT STYLE="font-size: 10pt">TYPE OF REPORTING PERSON (See Instructions)<BR>
OO</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 3.75pt">&nbsp;</TD></TR>
<TR>
    <TD STYLE="width: 8%">&nbsp;</TD>
    <TD STYLE="width: 12%">&nbsp;</TD>
    <TD STYLE="width: 2%">&nbsp;</TD>
    <TD STYLE="width: 2%">&nbsp;</TD>
    <TD STYLE="width: 70%">&nbsp;</TD>
    <TD STYLE="width: 6%">&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-indent: 1in">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</P>


<HR SIZE="1" NOSHADE ALIGN="LEFT" STYLE="width: 192px; width: 2in; color: black">

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 10pt">* This percentage is calculated based upon 39,657,841 shares
of common stock outstanding of Synlogic, Inc. (the &ldquo;Issuer&rdquo;), as set forth in the Issuer&rsquo;s Form 10-K filed with
the Securities and Exchange Commission on March 25, 2021.</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0 0 10pt">&nbsp;</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0 0 10pt">&nbsp;</P>

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    <DIV STYLE="break-before: page; margin-top: 6pt; margin-bottom: 6pt"><P STYLE="margin: 0pt">&nbsp;</P></DIV>
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<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0 0 10pt"></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0 0 10pt">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 12pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 72px"><FONT STYLE="font-size: 10pt"><B>Item 1.</B></FONT></TD>
    <TD><FONT STYLE="font-size: 10pt"><B>Security and Issuer</B></FONT></TD></TR>
</TABLE>
<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>


<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 12pt; text-align: justify; text-indent: 0.5in">This Amendment No.
4 (&ldquo;<U>Amendment No. 4</U>&rdquo;) to Schedule 13D supplements and amends the statement on Schedule 13D (the &ldquo;<U>Statement</U>&rdquo;)
originally filed by OrbiMed Advisors LLC, OrbiMed Capital GP VI LLC, and Samuel D. Isaly with the Securities and Exchange Commission
(the &ldquo;<U>SEC</U>&rdquo;) on September 7, 2017, as amended by Amendment No.&nbsp;1 (&ldquo;<U>Amendment No. 1</U>&rdquo;)
filed with the SEC on January 26, 2018, Amendment No. 2 filed with the SEC on April 12, 2018, and Amendment No. 3 filed with the
SEC on August 12, 2019 (&ldquo;<U>Amendment No. 3</U>&rdquo;). This Statement relates to the common stock, par value $0.001 per
share (the &ldquo;<U>Shares</U>&rdquo;), of Synlogic, Inc., a Delaware corporation formerly known as Mirna Therapeutics, Inc. (the
&ldquo;<U>Issuer</U>&rdquo;), with its principal offices located at 301 Binney St., Suite 402, Cambridge, Massachusetts 02142.&nbsp;
The Shares are listed on The NASDAQ Capital Market under the ticker symbol &ldquo;SYBX&rdquo;. Information given in response to
each item shall be deemed incorporated by reference in all other items, as applicable. As reported in Amendment No. 1, Samuel D.
Isaly has ceased to be a reporting person for purposes of the Statement.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 12pt; text-align: justify; text-indent: 0.5in"><FONT STYLE="background-color: white">Based
on the Issuer&rsquo;s annual report on&nbsp;</FONT>Form 10-K<FONT STYLE="background-color: white">&nbsp;filed with the SEC on March
25, 2021, there were&nbsp;</FONT>39,657,841 <FONT STYLE="background-color: white">outstanding Shares as of March 18, 2021.&nbsp;
This number is greater than the total number of outstanding Shares reported on the Issuer&rsquo;s&nbsp;Rule 424(b)(4)&nbsp;</FONT>Prospectus<FONT STYLE="background-color: white">,
filed with the SEC on August 8, 2019.&nbsp;&nbsp;As a result of the increase in the Issuer&rsquo;s total number of outstanding
Shares, the beneficial ownership of the outstanding Shares of the Issuer held by the Reporting Persons was&nbsp;reduced by more&nbsp;than
1% since the last filing.</FONT></P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 12pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 72px"><FONT STYLE="font-size: 10pt"><B>Item 2.</B></FONT></TD>
    <TD><FONT STYLE="font-size: 10pt"><B>Identity and Background</B></FONT></TD></TR>
</TABLE>
<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in"><FONT STYLE="font-size: 10pt">(a)</FONT>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<FONT STYLE="font-size: 10pt">This
Statement is being filed by OrbiMed Advisors LLC (&ldquo;<U>Advisors</U>&rdquo;), a limited liability company organized under the
laws of Delaware, and OrbiMed Capital GP VI LLC (&ldquo;<U>GP VI</U>&rdquo;), a limited liability company organized under the laws
of Delaware (collectively, the &ldquo;<U>Reporting Persons</U>&rdquo;).</FONT></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>



<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in"><FONT STYLE="font-size: 10pt">(b)
&ndash; (c), (f)</FONT>&nbsp;&nbsp;<FONT STYLE="font-size: 10pt">Advisors, a registered investment adviser under the Investment
Advisers Act of 1940, as amended, is the managing member of GP VI, which is the general partner of OrbiMed Private Investments
VI, LP (&ldquo;<U>OPI VI</U>&rdquo;), which holds Shares, as more particularly described in Item 3 below.&nbsp; Advisors has its
principal offices at 601 Lexington Avenue, 54th Floor, New York, New York 10022.</FONT></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in">GP VI has its principal
offices at 601 Lexington Avenue, 54th Floor, New York, New York 10022.</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in">The directors and executive
officers of Advisors and GP VI are set forth on Schedules I and II, attached hereto.&nbsp; Schedules I and II set forth the following
information with respect to each such person:</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in"><FONT STYLE="font-size: 10pt">(i)</FONT>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<FONT STYLE="font-size: 10pt">name;</FONT></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in"><FONT STYLE="font-size: 10pt">(ii)</FONT>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<FONT STYLE="font-size: 10pt">business address;</FONT></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in"><FONT STYLE="font-size: 10pt">(iii)</FONT>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<FONT STYLE="font-size: 10pt">present principal occupation or employment and the name, principal business and address of any corporation
or other organization in which such employment is conducted; and</FONT></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in"><FONT STYLE="font-size: 10pt">(iv)</FONT>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<FONT STYLE="font-size: 10pt">citizenship.</FONT></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in"><FONT STYLE="font-size: 10pt">(d)
&ndash; (e)</FONT>&nbsp;&nbsp;<FONT STYLE="font-size: 10pt">During the last five years, neither the Reporting Persons nor any person
named in Schedule I or II have been (i) convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors)
or (ii) a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding
was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject
to, federal or state securities laws or finding any violation with respect to such laws.</FONT></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in"><FONT STYLE="font-size: 10pt">&nbsp;</FONT></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in"><FONT STYLE="font-size: 10pt"></FONT></P>

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<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in"><FONT STYLE="font-size: 10pt">&nbsp;</FONT></P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 12pt"><TR STYLE="vertical-align: top">
<TD STYLE="width: 0"></TD><TD STYLE="width: 0.75in"><B>Item 3.</B></TD><TD><B>Source and Amount of Funds or Other Consideration</B></TD></TR></TABLE>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 12pt; text-align: justify; text-indent: 0.5in">Not applicable.</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 12pt"><TR STYLE="vertical-align: top">
<TD STYLE="width: 0"></TD><TD STYLE="width: 0.75in"><B>Item 4.</B></TD><TD><B>Purpose of Transaction</B></TD></TR></TABLE>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 12pt; text-align: justify; text-indent: 0.5in">The Shares were
initially acquired by the Reporting Persons for the purpose of making an investment in the Issuer and not with the intention of
acquiring control of the Issuer&rsquo;s business.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 12pt; text-align: justify; text-indent: 0.5in">The Reporting Persons
from time to time intend to review their investment in the Issuer on the basis of various factors, including the Issuer&rsquo;s
business, financial condition, results of operations and prospects, general economic and industry conditions, the securities markets
in general and those for the Issuer&rsquo;s Shares in particular, as well as other developments and other investment opportunities.
Based upon such review, the Reporting Persons will take such actions in the future as the Reporting Persons may deem appropriate
in light of the circumstances existing from time to time. If the Reporting Persons believe that further investment in the Issuer
is attractive, whether because of the market price of the Shares or otherwise, they may acquire Shares or other securities of the
Issuer either in the open market or in privately negotiated transactions. Similarly, depending on market and other factors, the
Reporting Persons may determine to dispose of some or all of the Shares currently owned by the Reporting Persons or otherwise acquired
by the Reporting Persons either in the open market or in privately negotiated transactions.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in">Except as set forth in this Statement, the Reporting
Persons have not formulated any plans or proposals which relate to or would result in: (a) the acquisition by any person of additional
securities of the Issuer or the disposition of securities of the Issuer; (b) an extraordinary corporate transaction, such as a
merger, reorganization or liquidation, involving the Issuer or any of its subsidiaries; (c) a sale or transfer of a material amount
of the assets of the Issuer or any of its subsidiaries; (d) any change in the present Board of Directors or management of the Issuer,
including any plans or proposals to change the number or term of directors or to fill any existing vacancies on the board; (e)
any material change in the Issuer&rsquo;s capitalization or dividend policy of the Issuer; (f) any other material change in the
Issuer&rsquo;s business or corporate structure; (g) any change in the Issuer&rsquo;s charter or bylaws or other instrument corresponding
thereto or other action which may impede the acquisition of control of the Issuer by any person; (h) causing a class of the Issuer&rsquo;s
securities to be deregistered or delisted from a national securities exchange or to cease to be authorized to be quoted in an inter-dealer
quotation system of a registered national securities association; (i) a class of equity securities of the Issuer becoming eligible
for termination of registration pursuant to Section&nbsp;12(g)(4) of the Act; or (j) any action similar to any of those enumerated
above.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 12pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 72px"><FONT STYLE="font-size: 10pt"><B>Item 5.</B></FONT></TD>
    <TD><FONT STYLE="font-size: 10pt"><B>Interest in Securities of the Issuer</B></FONT></TD></TR>
</TABLE>
<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>


<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in"><FONT STYLE="font-size: 10pt">(a)-(b)</FONT>&nbsp;&nbsp;&nbsp;<FONT STYLE="font-size: 10pt">As
of the date of this filing, the Reporting Persons may be deemed, for purposes of Rule 13d-3 of the Securities Exchange Act of 1934,
as amended, directly or indirectly, including by reason of their mutual affiliation, to be the beneficial owners of the Shares
described in Item 6 below&nbsp; Based upon information contained in the Issuer&rsquo;s Form 10-K, filed with the Securities and
Exchange Commission on March 25, 2021, such Shares deemed to be indirectly beneficially owned by the Reporting Persons constitutes
approximately 5.1% of the issued and outstanding Shares. Advisors, pursuant to its authority as the managing member of GP VI, the
general partner of OPI VI, may be deemed to indirectly beneficially own the Shares held by OPI VI.&nbsp; GP VI, pursuant to its
authority as the general partner of OPI VI, may be deemed to indirectly beneficially own the Shares held by OPI VI.&nbsp; As a
result, Advisors and GP VI share the power to direct the vote and to direct the disposition of the Shares held by OPI VI. Advisors
exercises this investment and voting power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and Jonathan
T. Silverstein, each of whom disclaims beneficial ownership of the Shares held by OPI VI.</FONT></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in">(c)</FONT>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<FONT STYLE="font-size: 10pt">The
Reporting Persons have not effected any transactions in the Shares during the past sixty (60) days.</FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in">(d)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Not
applicable.</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 12pt; text-align: justify; text-indent: 0.5in">(e)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Not
applicable.</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0"></P>

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    <DIV STYLE="break-before: page; margin-top: 6pt; margin-bottom: 6pt"><P STYLE="margin: 0pt">&nbsp;</P></DIV>
    <!-- Field: /Page -->

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 12pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 72px"><FONT STYLE="font-size: 10pt"><B>Item 6.</B></FONT></TD>
    <TD><FONT STYLE="font-size: 10pt"><B>Contracts, Arrangements, Understandings or Relationship with Respect to Securities of the Issuer</B></FONT></TD></TR>
</TABLE>
<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in">In addition to the relationships
between the Reporting Persons described in Items 2 and 5 above, GP VI is the general partner of OPI VI, pursuant to the terms of
the limited partnership agreement of OPI VI.&nbsp; Advisors is the managing member of GP VI, pursuant to the terms of the limited
liability company agreement of GP VI.&nbsp; Pursuant to these agreements and relationships, Advisors and GP VI have discretionary
investment management authority with respect to the assets of OPI VI.&nbsp; Such authority includes the power of GP VI to vote
and otherwise dispose of securities purchased by OPI VI.&nbsp; The number of Shares attributable to OPI VI is 2,029,996.&nbsp;
Advisors and GP VI may each be considered to hold indirectly 2,029,996 Shares.&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in">Chau Khuong (&ldquo;<U>Khuong</U>&rdquo;),
an employee at Advisors, has been a member of the Board of Directors of the Issuer since September 2013, and, accordingly, the
Reporting Persons may have the ability to affect and influence control of the Issuer. From time to time, Khuong may receive additional
stock options or other awards of equity-based compensation pursuant to the Issuer&rsquo;s compensation arrangements for non-employee
directors. Khuong is obligated to transfer any Shares issued under any such stock options or other awards, or the economic benefit
thereof, to the Reporting Persons, which will in turn ensure that such shares or economic benefits are provided to OPI VI.&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 12pt; text-align: justify">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 12pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 72px"><FONT STYLE="font-size: 10pt"><B>Item 7.</B></FONT></TD>
    <TD><FONT STYLE="font-size: 10pt"><B>Materials to Be Filed as Exhibits</B></FONT></TD></TR>
</TABLE>
<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 12pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 12%; border: black 1.5pt solid; padding: 2.25pt"><FONT STYLE="font-size: 10pt"><B>Exhibit</B></FONT></TD>
    <TD STYLE="width: 88%; border-top: black 1.5pt solid; border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 2.25pt"><FONT STYLE="font-size: 10pt"><B>Description</B></FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 2.25pt"><FONT STYLE="font-size: 10pt">1.</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; padding: 2.25pt"><FONT STYLE="font-size: 10pt">Joint Filing Agreement among OrbiMed Advisors LLC, and OrbiMed Capital GP VI LLC.</FONT></TD></TR>
</TABLE>
<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0"><B>&nbsp;</B></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B></B></P>

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    <DIV STYLE="break-before: page; margin-top: 6pt; margin-bottom: 6pt"><P STYLE="margin: 0pt">&nbsp;</P></DIV>
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<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>Signature</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in">After reasonable inquiry and to the best of
my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 12pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD><FONT STYLE="font-size: 10pt">Dated: March 29, 2021</FONT></TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">ORBIMED ADVISORS LLC</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 52%">&nbsp;</TD>
    <TD STYLE="width: 5%">&nbsp;</TD>
    <TD STYLE="width: 33%">&nbsp;</TD>
    <TD STYLE="width: 10%">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">By:</FONT></TD>
    <TD STYLE="border-bottom: black 1.5pt solid"><FONT STYLE="font-size: 10pt">/s/ Carl L. Gordon</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">Name: Carl L. Gordon</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">Title: Member</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">ORBIMED CAPITAL GP VI LLC</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">By:</FONT></TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">ORBIMED ADVISORS LLC, its managing member</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">Member of OrbiMed Advisors LLC</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD COLSPAN="2">&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">By:</FONT></TD>
    <TD STYLE="border-bottom: black 1.5pt solid"><FONT STYLE="font-size: 10pt">/s/ Carl L. Gordon</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">Carl L. Gordon</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">Member of OrbiMed Advisors LLC</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P></TD>
    <TD>&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 3.25in"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B></B></P>

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    <DIV STYLE="break-before: page; margin-top: 6pt; margin-bottom: 6pt"><P STYLE="margin: 0pt">&nbsp;</P></DIV>
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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>SCHEDULE I</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0.05in; text-align: justify; text-indent: 0.45in"><FONT STYLE="font-size: 10pt">The
names and present principal occupations of each of the executive officers and directors of OrbiMed Advisors LLC are set forth below.
Unless otherwise noted, each of these persons is a United States citizen and has a business address of 601 Lexington Avenue, 54</FONT><FONT STYLE="font-size: 8pt">th</FONT>
<FONT STYLE="font-size: 10pt">Floor, New York, NY 10022.</FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0.05in; text-align: justify; text-indent: 0.45in">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 12pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 34%; padding-right: 0.25in; text-align: center"><FONT STYLE="font-size: 10pt"><U>Name</U></FONT></TD>
    <TD STYLE="width: 33%; padding-right: 0.25in; text-align: center"><FONT STYLE="font-size: 10pt"><U>Position with Reporting Person</U></FONT></TD>
    <TD STYLE="width: 33%; padding-right: 0.25in; text-align: center"><FONT STYLE="font-size: 10pt"><U>Principal Occupation</U></FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="padding-right: 0.25in; text-align: justify"><FONT STYLE="font-size: 10pt">Carl L. Gordon</FONT></TD>
    <TD STYLE="padding-right: 0.25in; text-align: justify"><FONT STYLE="font-size: 10pt">Member</FONT></TD>
    <TD>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">Member</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">OrbiMed Advisors LLC</P></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">Sven H. Borho</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">German and Swedish Citizen</P></TD>
    <TD STYLE="padding-right: 0.25in; text-align: justify"><FONT STYLE="font-size: 10pt">Member</FONT></TD>
    <TD>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">Member</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">OrbiMed Advisors LLC</P></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="padding-right: 0.25in; text-align: justify"><FONT STYLE="font-size: 10pt">Jonathan T. Silverstein</FONT></TD>
    <TD STYLE="padding-right: 0.25in; text-align: justify"><FONT STYLE="font-size: 10pt">Member</FONT></TD>
    <TD>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">Member</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">OrbiMed Advisors LLC</P></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="padding-right: 0.25in; text-align: justify"><FONT STYLE="font-size: 10pt">W. Carter Neild</FONT></TD>
    <TD STYLE="padding-right: 0.25in; text-align: justify"><FONT STYLE="font-size: 10pt">Member</FONT></TD>
    <TD>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">Member</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">OrbiMed Advisors LLC</P></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="padding-right: 0.25in; text-align: justify"><FONT STYLE="font-size: 10pt">Geoffrey C. Hsu</FONT></TD>
    <TD STYLE="padding-right: 0.25in; text-align: justify"><FONT STYLE="font-size: 10pt">Member</FONT></TD>
    <TD>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">Member</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">OrbiMed Advisors LLC</P></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="padding-right: 0.25in; text-align: justify"><FONT STYLE="font-size: 10pt">C. Scotland Stevens </FONT></TD>
    <TD><FONT STYLE="font-size: 10pt">Member</FONT></TD>
    <TD>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">Member</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">OrbiMed Advisors LLC</P></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="padding-right: 0.25in; text-align: justify">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD STYLE="padding-right: 0.25in; text-align: justify">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="padding-right: 0.25in; text-align: justify"><FONT STYLE="font-size: 10pt">David P. Bonita</FONT></TD>
    <TD><FONT STYLE="font-size: 10pt">Member</FONT></TD>
    <TD>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">Member</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">OrbiMed Advisors LLC</P></TD></TR><TR STYLE="vertical-align: top">
    <TD STYLE="padding-right: 0.25in; text-align: justify">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD STYLE="padding-right: 0.25in; text-align: justify">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="padding-right: 0.25in; text-align: justify"><FONT STYLE="font-size: 10pt">Trey Block</FONT></TD>
    <TD><FONT STYLE="font-size: 10pt">Chief Financial Officer</FONT></TD>
    <TD>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">Chief Financial Officer</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0; text-align: justify">OrbiMed Advisors LLC</P></TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

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    <DIV STYLE="break-before: page; margin-top: 6pt; margin-bottom: 6pt"><P STYLE="margin: 0pt">&nbsp;</P></DIV>
    <!-- Field: /Page -->

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>SCHEDULE II</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0.25in 0 0.05in; text-align: justify; text-indent: 0.45in">The business
and operations of OrbiMed Capital GP VI LLC are managed by the executive officers and directors of its managing member, OrbiMed
Advisors LLC, set forth in Schedule I attached hereto.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

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    <DIV STYLE="break-before: page; margin-top: 6pt; margin-bottom: 6pt"><P STYLE="margin: 0pt">&nbsp;</P></DIV>
    <!-- Field: /Page -->

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>EXHIBIT INDEX</B></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 12pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 12%; border-top: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 4.5pt"><FONT STYLE="font-size: 10pt"><B>Exhibit</B></FONT></TD>
    <TD STYLE="width: 88%; border: black 1.5pt solid; padding: 4.5pt"><FONT STYLE="font-size: 10pt"><B>Description</B></FONT></TD></TR>
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    <TD STYLE="border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 4.5pt"><FONT STYLE="font-size: 10pt">1.</FONT></TD>
    <TD STYLE="border-right: black 1.5pt solid; border-bottom: black 1.5pt solid; border-left: black 1.5pt solid; padding: 4.5pt"><FONT STYLE="font-size: 10pt">Joint Filing Agreement among OrbiMed Advisors LLC and OrbiMed Capital GP VI LLC.</FONT></TD></TR>
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<TYPE>EX-99.1
<SEQUENCE>2
<FILENAME>ss195345_ex9901.htm
<DESCRIPTION>JOINT FILING AGREEMENT
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<P STYLE="margin: 0">&nbsp;</P>

<P STYLE="margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: right"><B><U>Exhibit 1</U></B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">JOINT FILING AGREEMENT</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-indent: 0.75in">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in">&nbsp;<FONT STYLE="background-color: white">The
undersigned hereby agree that the Amendment No. 4 to Schedule&nbsp;13D, dated March 29, 2021, with respect to the ordinary shares
of Synlogic, Inc. is filed on behalf of each of us pursuant to and in accordance with the provisions of Rule&nbsp;13d-1(k) under
the Securities Exchange Act of 1934, as amended. Each of the undersigned agrees to be responsible for the timely filing of this
Statement, and for the completeness and accuracy of the information concerning itself contained therein. This Agreement may be
executed in any number of counterparts, all of which taken together shall constitute one and the same instrument.</FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;&nbsp;&nbsp;&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in">IN WITNESS WHEREOF, the undersigned have executed
this Agreement as of the 29<SUP>th</SUP> day of March 2021.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 12pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">ORBIMED ADVISORS LLC</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 52%">&nbsp;</TD>
    <TD STYLE="width: 5%">&nbsp;</TD>
    <TD STYLE="width: 33%">&nbsp;</TD>
    <TD STYLE="width: 10%">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">By:</FONT></TD>
    <TD STYLE="border-bottom: black 1.5pt solid"><FONT STYLE="font-size: 10pt">&nbsp;/s/ Carl L. Gordon</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">Name: Carl L. Gordon</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">Title: Member</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">ORBIMED CAPITAL GP VI LLC</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">By:</FONT></TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">ORBIMED ADVISORS LLC, its managing member</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD COLSPAN="2">&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">By:</FONT></TD>
    <TD STYLE="border-bottom: black 1.5pt solid"><FONT STYLE="font-size: 10pt">/s/ Carl L. Gordon</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">Carl L. Gordon</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">Member of OrbiMed Advisors LLC</FONT></TD>
    <TD>&nbsp;</TD></TR>
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