<SEC-DOCUMENT>0001172661-18-000540.txt : 20180213
<SEC-HEADER>0001172661-18-000540.hdr.sgml : 20180213
<ACCEPTANCE-DATETIME>20180213164953
ACCESSION NUMBER:		0001172661-18-000540
CONFORMED SUBMISSION TYPE:	SC 13G/A
PUBLIC DOCUMENT COUNT:		1
FILED AS OF DATE:		20180213
DATE AS OF CHANGE:		20180213

SUBJECT COMPANY:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Xenon Pharmaceuticals Inc.
		CENTRAL INDEX KEY:			0001582313
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				980661854
		STATE OF INCORPORATION:			A1
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		SC 13G/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	005-88403
		FILM NUMBER:		18604280

	BUSINESS ADDRESS:	
		STREET 1:		200 - 3650 GILMORE WAY
		CITY:			BURNABY
		STATE:			A1
		ZIP:			V5G 48W
		BUSINESS PHONE:		(604) 484-3300

	MAIL ADDRESS:	
		STREET 1:		200 - 3650 GILMORE WAY
		CITY:			BURNABY
		STATE:			A1
		ZIP:			V5G 48W

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 13G/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 13G/A
<SEQUENCE>1
<FILENAME>xene123117a1.htm
<DESCRIPTION>13G/A
<TEXT>
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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: left"><B>&nbsp;</B></P>

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

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

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>SECURITIES AND EXCHANGE
COMMISSION<BR> Washington, DC 20549</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>SCHEDULE 13G/A<BR>
                   </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>Under the Securities Exchange Act of 1934</B></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>(Amendment No. 1)*</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><BR STYLE="mso-special-character: line-break">
<BR STYLE="mso-special-character: line-break">
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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

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    <TD STYLE="width: 100%; border-bottom: windowtext 1pt solid; font: bold 18pt Times New Roman, Times, Serif; padding-right: 5.4pt; padding-left: 5.4pt; text-align: center">Xenon Pharmaceuticals Inc.</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; padding-right: 5.4pt; padding-left: 5.4pt; text-align: center">(Name of Issuer)</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="padding-right: 5.4pt; padding-left: 5.4pt">
        <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: center">&nbsp;</P></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid; font: 10pt Times New Roman, Times, Serif; padding-right: 5.4pt; padding-left: 5.4pt; text-align: center"><B>Common Stock</TD></TR>
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    <TD STYLE="font: 10pt Times New Roman, Times, Serif; padding-right: 5.4pt; padding-left: 5.4pt; text-align: center">(Title of Class of Securities)</TD></TR>
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        <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: center">&nbsp;</P></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid; font: bold 10pt Times New Roman, Times, Serif; padding-right: 5.4pt; padding-left: 5.4pt; text-align: center">98420N105</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; padding-right: 5.4pt; padding-left: 5.4pt; text-align: center">(CUSIP Number)</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="padding-right: 5.4pt; padding-left: 5.4pt">
        <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">&nbsp;</P></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid; font: bold 10pt Times New Roman, Times, Serif; padding-right: 5.4pt; padding-left: 5.4pt; text-align: center">December
    31, 2017</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="font: 10pt Times New Roman, Times, Serif; padding-right: 5.4pt; padding-left: 5.4pt; text-align: center">(Date of Event Which Requires Filing of this Statement)</TD></TR>
</TABLE>
<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">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">Check the appropriate box to designate the
rule pursuant to which this Schedule is filed:</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 0 0 0.5in; text-align: justify"></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0 0 0 0.5in; text-align: justify"><FONT STYLE="font-family: Wingdings">x</FONT><FONT STYLE="font-size: 10pt">&#9;Rule
13d-1(b)</FONT></P>

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

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0 0 0 0.5in; text-align: justify"><FONT STYLE="font-family: Wingdings">o</FONT><FONT STYLE="font-size: 10pt">&#9;Rule
13d-1(c)</FONT></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0 0 0 0.5in; text-align: justify"><FONT STYLE="font-family: Wingdings">o</FONT><FONT STYLE="font-size: 10pt">&#9;Rule
13d-1(d)</FONT></P>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0 0 0 0.5in; text-align: justify">&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: justify">*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 the disclosures provided in a prior cover page.</P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">The information required in the remainder of
this cover page shall not be deemed to be &ldquo;filed&rdquo; for the purpose of Section 18 of the Securities Exchange Act of 1934
(&ldquo;Act&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>

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<td valign="top" width="40%">
<div style="TEXT-ALIGN: center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">&#160;<font style="DISPLAY: inline; FONT-WEIGHT: bold">SCHEDULE 13G/A</font></div>
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<td align="left" width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: medium none; BORDER-RIGHT: medium none"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">&#160;</font></td>
<td width="12%" style="BORDER-BOTTOM: black 2px solid"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">&#160;</font></td>
<td width="8%" style="BORDER-BOTTOM: black 2px solid">&#160;</td>
<td width="66%" style="BORDER-BOTTOM: black 2px solid">&#160;</td>
<td align="left" width="6%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: medium none">&#160;</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">1</font></div>
</td>
<td colspan="4" width="92%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 10pt">NAME OF REPORTING </font>PERSONS</FONT></DIV>

<DIV STYLE="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt; text-align: left"><FONT STYLE="display: inline; font: 10pt times new roman"></font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><FONT STYLE="font: 10pt times new roman">OrbiMed Capital GP VI LLC</FONT></DIV>

<DIV STYLE="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt; text-align: left"></DIV>

<DIV STYLE="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt; text-align: left"></DIV>

<DIV STYLE="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt; text-align: left"></div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">2</font></div>
</td>
<td colspan="3" width="86%" style="BORDER-BOTTOM: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP </font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">(a) <font style="DISPLAY: inline; FONT-FAMILY: wingdings">o</font></font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">(b) <font style="DISPLAY: inline; FONT-FAMILY: wingdings">o</font></font></div>
</td>
<td nowrap width="6%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">&#160;</font></div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">3</font></div>
</td>
<td colspan="4" width="92%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">SEC USE ONLY</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">&#160;</div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">4</font></div>
</td>
<td colspan="4" width="92%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">CITIZENSHIP OR PLACE OF ORGANIZATION</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">Delaware</div>
</td>
</tr><tr>
<td colspan="2" rowspan="4" width="20%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">NUMBER OF</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">SHARES</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">BENEFICIALLY</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">OWNED BY</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">EACH</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">REPORTING</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">PERSON</font></div>

<div style="TEXT-ALIGN: center; TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">WITH</font></div>
</td>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">5</font></div>
</td>
<td colspan="2" width="72%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">SOLE VOTING POWER</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">0</div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">6</font></div>
</td>
<td colspan="2" width="72%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">SHARED VOTING POWER</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">634,812</div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">7</font></div>
</td>
<td colspan="2" width="72%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">SOLE DISPOSITIVE POWER</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><FONT STYLE="font: 10pt times new roman">0</div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">8</font></div>
</td>
<td colspan="2" width="72%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">SHARED DISPOSITIVE POWER</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">
634,812</div>
</div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">9</font></div>
</td>
<td colspan="4" width="92%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">634,812</div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">10</font></div>
</td>
<td colspan="3" width="86%" style="BORDER-BOTTOM: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES </font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">&#160;</div>
</td>
<td valign="top" width="6%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt"><font style="DISPLAY: inline; FONT-FAMILY: wingdings; FONT-SIZE: 10pt">o</font></font></div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">11</font></div>
</td>
<td colspan="4" width="92%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">3.55%</div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">12</font></div>
</td>
<td colspan="4" width="92%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">TYPE OF REPORTING PERSON </font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">OO</div>
</td>
</tr></table>

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</P>
<table cellpadding="8" cellspacing="0" width="100%" style="FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">
<tr>
<td align="left" valign="top" width="30%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-TOP: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-WEIGHT: bold">CUSIP
No. 98420N105</div>
</td>
<td valign="top" width="40%">
<div style="TEXT-ALIGN: center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">&#160;<font style="DISPLAY: inline; FONT-WEIGHT: bold">SCHEDULE 13G/A</font></div>
</td>
<td align="left" valign="top" width="30%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-TOP: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: right; TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 9pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-WEIGHT: bold">Page&#160;3
of&#160;8 Pages</font></div>
</td>
</tr></table>

<table cellpadding="3" cellspacing="0" width="100%" style="FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">
<tr>
<td align="left" width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: medium none; BORDER-RIGHT: medium none"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">&#160;</font></td>
<td width="12%" style="BORDER-BOTTOM: black 2px solid"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">&#160;</font></td>
<td width="8%" style="BORDER-BOTTOM: black 2px solid">&#160;</td>
<td width="66%" style="BORDER-BOTTOM: black 2px solid">&#160;</td>
<td align="left" width="6%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: medium none">&#160;</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">1</font></div>
</td>
<td colspan="4" width="92%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 10pt">NAME OF REPORTING </font>PERSONS</FONT></DIV>

<DIV STYLE="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt; text-align: left"><FONT STYLE="display: inline; font: 10pt times new roman"></font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><FONT STYLE="font: 10pt times new roman">OrbiMed Advisors LLC</DIV>

<DIV STYLE="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt; text-align: left"></DIV>

<DIV STYLE="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt; text-align: left"></DIV>

<DIV STYLE="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt; text-align: left"></div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">2</font></div>
</td>
<td colspan="3" width="86%" style="BORDER-BOTTOM: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP </font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">(a) <font style="DISPLAY: inline; FONT-FAMILY: wingdings">o</font></font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">(b) <font style="DISPLAY: inline; FONT-FAMILY: wingdings">o</font></font></div>
</td>
<td nowrap width="6%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">&#160;</font></div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">3</font></div>
</td>
<td colspan="4" width="92%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">SEC USE ONLY</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">&#160;</div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">4</font></div>
</td>
<td colspan="4" width="92%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">CITIZENSHIP OR PLACE OF ORGANIZATION</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">Delaware</div>
</td>
</tr><tr>
<td colspan="2" rowspan="4" width="20%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">NUMBER OF</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">SHARES</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">BENEFICIALLY</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">OWNED BY</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">EACH</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">REPORTING</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">PERSON</font></div>

<div style="TEXT-ALIGN: center; TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">WITH</font></div>
</td>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">5</font></div>
</td>
<td colspan="2" width="72%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">SOLE VOTING POWER</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">0</div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">6</font></div>
</td>
<td colspan="2" width="72%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">SHARED VOTING POWER</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">634,812</div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">7</font></div>
</td>
<td colspan="2" width="72%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">SOLE DISPOSITIVE POWER</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><FONT STYLE="font: 10pt times new roman">0</div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">8</font></div>
</td>
<td colspan="2" width="72%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">SHARED DISPOSITIVE POWER</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"></div>
634,812</div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">9</font></div>
</td>
<td colspan="4" width="92%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">634,812</div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">10</font></div>
</td>
<td colspan="3" width="86%" style="BORDER-BOTTOM: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES </font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">&#160;</div>
</td>
<td valign="top" width="6%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt"><font style="DISPLAY: inline; FONT-FAMILY: wingdings; FONT-SIZE: 10pt">o</font></font></div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">11</font></div>
</td>
<td colspan="4" width="92%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)</font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">3.55%</div>
</td>
</tr><tr>
<td width="8%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: center"><font style="FONT-FAMILY: times new roman; FONT-SIZE: 14pt">12</font></div>
</td>
<td colspan="4" width="92%" style="BORDER-BOTTOM: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">TYPE OF REPORTING PERSON </font></div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="justify">&#160;</div>

<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left">IA</div>
</td>
</tr></table>


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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>
<table cellpadding="8" cellspacing="0" width="100%" style="FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-SIZE: 10pt; FONT-FAMILY: times new roman">
<tr>
<td align="left" valign="top" width="30%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-TOP: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-WEIGHT: bold">CUSIP No.&#160;&#160;98420N105</div>
</td>
<td valign="top" width="40%">
<div style="TEXT-ALIGN: center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">&#160;<font style="DISPLAY: inline; FONT-WEIGHT: bold">SCHEDULE 13G/A</font></font></div>
</td>
<td align="left" valign="top" width="30%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-TOP: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: right; TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 9pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-WEIGHT: bold">Page
4    of&#160;8 Pages</font></div>
</td>
</tr></table>
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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"></P>

<div align="left"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt"><TR STYLE="vertical-align: top; text-align: left">
<TD NOWRAP STYLE="width: 33pt; text-align: left"><FONT STYLE="letter-spacing: -0.15pt"><B>Item 1.</B></FONT></TD><TD STYLE="width: 5pt"></TD><TD STYLE="text-align: left"><FONT STYLE="letter-spacing: -0.15pt"><B>(a)&#9;Name of Issuer:</B></FONT></TD>
</TR></TABLE></div>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify">Xenon Pharmaceuticals Inc.</P>

<TABLE width="100%" CELLPADDING="0" CELLSPACING="0" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt"><TR STYLE="vertical-align: top; text-align: justify">
<TD STYLE="width: 33pt; text-align: right"><FONT STYLE="letter-spacing: -0.15pt"><B></B></FONT></TD><TD STYLE="width: 5pt"></TD><TD STYLE="text-align: justify"><FONT STYLE="letter-spacing: -0.15pt"><B>(b)&#9;Address of Issuer&rsquo;s Principal
Executive Offices:</B></FONT></TD>
</TR></TABLE>

<P STYLE="font: 12pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 1in"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify">200-3650 Gilmore Way</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify">Burnaby,
British Columbia, Canada V5G 4W8</P>

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<TD STYLE="width: 33pt; text-align: left"><FONT STYLE="letter-spacing: -0.15pt"><B>Item 2.</B></FONT></TD><TD STYLE="width: 5pt"></TD><TD STYLE="text-align: justify"><FONT STYLE="letter-spacing: -0.15pt"><B>(a)&#9;Name of Person Filing</B></FONT>:</TD>
</TR></TABLE>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 44pt; text-indent: 0pt; text-align: justify"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 44pt; text-indent: 0pt; text-align: justify">OrbiMed Capital GP VI LLC</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 44pt; text-indent: 0pt; text-align: justify">OrbiMed Advisors LLC</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 44pt; text-indent: 0pt; text-align: justify"></P>

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

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<TD STYLE="width: 33pt; text-align: left"><FONT STYLE="letter-spacing: -0.15pt"><B></B></FONT></TD><TD STYLE="width: 5pt"></TD><TD STYLE="text-align: justify"><FONT STYLE="letter-spacing: -0.15pt"><B>(b)&#9;Address
of Principal Business Office:</B></FONT></TD>
</TR></TABLE>

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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 44pt; text-indent: 0pt; text-align: justify">601 Lexington Avenue, 54th Floor</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 44pt; text-indent: 0pt; text-align: justify">New York, NY 10022</P>

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<TD STYLE="width: 33pt; text-align: left"><FONT STYLE="letter-spacing: -0.15pt"><B></B></FONT></TD><TD STYLE="width: 5pt"></TD><TD STYLE="text-align: justify"><FONT STYLE="letter-spacing: -0.15pt"><B>(c)&#9;Citizenship</B>:</FONT></TD>
</TR></TABLE>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify">Please
refer to Item 4 on each cover page for each Reporting Person</FONT>.</P>

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<TD STYLE="width: 33pt; text-align: left">&nbsp;</TD><TD STYLE="width: 5pt"></TD><TD STYLE="text-align: justify"><FONT STYLE="letter-spacing: -0.15pt"><B>(d)&#9;Title of Class of Securities:</B></FONT></TD>
</TR></TABLE>

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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify">Common Stock</P>

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

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

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<TD STYLE="width: 33pt; text-align: left"><FONT STYLE="letter-spacing: -0.15pt"><B>&nbsp;</B></FONT></TD><TD STYLE="width: 5pt"></TD><TD STYLE="text-align: justify"><FONT STYLE="letter-spacing: -0.15pt"><B>(e) CUSIP No.:</B></FONT></TD>
</TR></TABLE>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify">98420N105</P>

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</td>
<td valign="top" width="40%">
<div style="TEXT-ALIGN: center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">&#160;<font style="DISPLAY: inline; FONT-WEIGHT: bold">SCHEDULE 13G/A</font></font></div>
</td>
<td align="left" valign="top" width="30%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-TOP: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: right; TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 9pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-WEIGHT: bold">Page&#160;5
of&#160;8 Pages</font></div>
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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"></P>

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

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<TR STYLE="vertical-align: bottom; text-align: center">
    <TH>&nbsp;</TH></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD STYLE="width: 100%"><div align="center"><P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><FONT STYLE="letter-spacing: -0.15pt"><B></B></FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 12pt 1in; text-align: justify; text-indent: -1in"><B>Item
3.&#9;</B> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</P>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 44pt; text-indent: 0pt; text-align: justify">OrbiMed Capital GP VI LLC ("GP VI") is the sole general partner of OrbiMed Private Investments VI, LP ("OPI VI"). OrbiMed Advisors
LLC ("Advisors") is an investment advisor in accordance with ss.240.13d-1(b)(1)(ii)(E) and is the Managing Member of GP VI.
Samuel D. Isaly, who was previously identified as a reporting person eligible to report on Schedule 13G/A as a control person
in accordance with ss.240.13d-1(b)(1)(ii)(G), has ceased to be the beneficial owner of more than five percent of the
outstanding Common Stock.</P></TD></TR>
</TABLE><DIV STYLE="text-align: center"><P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 12pt 1in; text-align: justify; text-indent: -1in"></P></DIV>

<DIV STYLE="text-align: center"><P STYLE="font: 12pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify"></P> </P>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><FONT STYLE="letter-spacing: 0pt"></FONT></P></DIV>

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

<P STYLE="margin: 0"></P>
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<tr>
<td align="left" valign="top" width="30%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-TOP: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-WEIGHT: bold">CUSIP No.&#160;98420N105</div>
</td>
<td valign="top" width="40%">
<div style="TEXT-ALIGN: center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">&#160;<font style="DISPLAY: inline; FONT-WEIGHT: bold">SCHEDULE 13G/A</font></font></div>
</td>
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<div style="TEXT-ALIGN: right; TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 9pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-WEIGHT: bold">Page
6    of&#160;8 Pages</font></div>
</td>
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<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">&nbsp;</P>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><FONT STYLE="letter-spacing: -0.15pt"><B>Item
4.&#9;Ownership:</B></FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><FONT STYLE="letter-spacing: -0.15pt"></FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 44pt; text-indent: 0pt; text-align: justify"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 44pt; text-indent: 0pt; text-align: justify">Information
with respect to the Reporting Person&rsquo;s ownership as of December 31, 2017 is incorporated by reference to items (5)
- (9) and (11) of the cover page for the Reporting Person.</P>

</P>

<DIV STYLE="text-align: center"><P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><FONT STYLE="letter-spacing: -0.15pt"><B>Item
5.&#9;Ownership of Five Percent or Less of a Class.</B></FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 44pt; text-indent: 0pt; text-align: justify"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 44pt; text-indent: 0pt; text-align: justify">If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial
owner of more than five percent of the class of securities, check the following [X].</FONT></P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><FONT STYLE="letter-spacing: -0.15pt"><B>Item
6.&#9;Ownership of More Than Five Percent on Behalf of Another Person</B></FONT>.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><FONT STYLE="letter-spacing: -0.15pt">&nbsp;</FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 44pt; text-indent: 0pt; text-align: justify">Reporting
persons are holding 3.55% of the shares in the aggregate on
behalf of other persons who have the right to receive or the power to direct the receipt of dividends from, or proceeds from
the sale of, such securities. Advisors exercises investment and voting power over the shares through a
management committee comprised of Carl L. Gordon, Sven H. Borho and Jonathan T. Silverstein, each of whom
disclaims beneficial ownership of the Common Stock reported herein. </P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><FONT STYLE="letter-spacing: -0.15pt"></FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in; text-align: justify; text-indent: -1in"><FONT STYLE="letter-spacing: -0.15pt"><B>Item
7. Identification and Classification of the Subsidiary which Acquired the Security Being Reported on by the Parent
Holding Company or Control Person.</B></FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in; text-align: justify; text-indent: -1in"><FONT STYLE="letter-spacing: -0.15pt"><B>&nbsp;</B></FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify">Not Applicable.</FONT></P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in; text-align: justify; text-indent: -1in"><FONT STYLE="letter-spacing: -0.15pt"><B>Item
8. Identification and Classification of Members of the Group</B></FONT>.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in; text-align: justify; text-indent: -1in"><FONT STYLE="letter-spacing: -0.15pt"><B>&nbsp;</B></FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify"><FONT STYLE="letter-spacing: -0.15pt">Not Applicable.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><FONT STYLE="letter-spacing: -0.15pt"></FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in; text-align: justify; text-indent: -1in"><FONT STYLE="letter-spacing: -0.15pt"><B>Item
9. Notice of Dissolution of Group</B>.</FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in; text-align: justify"><FONT STYLE="letter-spacing: -0.15pt"><B>&nbsp;</B></FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 22pt; text-indent: 22pt; text-align: justify">Not Applicable.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><FONT STYLE="letter-spacing: -0.15pt"></FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in; text-align: justify; text-indent: -1in"><FONT STYLE="letter-spacing: -0.15pt"><B>Item
10. Certification.</B></FONT></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in; text-align: justify; text-indent: -1in"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in; text-align: justify; text-indent: -1in"></P></DIV>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 6pt; margin-left: 44pt; text-indent: 0pt; text-align: justify">By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and
held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing
or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as
a participant in any transaction having that purpose or effect.</P>

<DIV STYLE="text-align: center"><P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in; text-align: justify; text-indent: -1in"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in; text-align: justify; text-indent: -1in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in; text-align: justify; text-indent: -1in"></P>

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

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</td>
<td valign="top" width="40%">
<div style="TEXT-ALIGN: center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">&#160;<font style="DISPLAY: inline; FONT-WEIGHT: bold">SCHEDULE 13G/A</font></font></div>
</td>
<td align="left" valign="top" width="30%" style="BORDER-BOTTOM: black 2px solid; BORDER-LEFT: black 2px solid; BORDER-TOP: black 2px solid; BORDER-RIGHT: black 2px solid">
<div style="TEXT-ALIGN: right; TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 9pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-WEIGHT: bold">Page&#160;7
of&#160;8 Pages</font></div>
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<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">&nbsp;</P>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B><U>SIGNATURES</U></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: justify; 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: 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">Dated: February 13, 2018</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"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></P>

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

<TABLE CELLPADDING="0" CELLSPACING="0" STYLE="border-collapse: collapse; width: 100%">
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD COLSPAN="3"><FONT STYLE="font-family: Times New Roman, Times, Serif; font-size: 10pt"><B>OrbiMed Advisors LLC</B></FONT></TD></TR>

<TR STYLE="vertical-align: top; text-align: left">
    <TD STYLE="width: 52%"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD STYLE="width: 3%"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD STYLE="width: 2%"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD STYLE="width: 43%"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">By:</FONT></TD>
    <TD COLSPAN="2" STYLE="border-bottom: Black 1pt solid"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">/s/ Jonathan T. Silverstein</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Name:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Jonathan T. Silverstein</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Title:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Member of OrbiMed Advisors LLC</TD></TR>
    <TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">By:</FONT></TD>
    <TD COLSPAN="2" STYLE="border-bottom: Black 1pt solid"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">/s/ Sven H. Borho</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Name:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Sven H. Borho</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Title:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Member of OrbiMed Advisors LLC</TD></TR>
    <TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">By:</FONT></TD>
    <TD COLSPAN="2" STYLE="border-bottom: Black 1pt solid"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">/s/ Carl L. Gordon</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Name:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Carl L. Gordon</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Title:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Member of OrbiMed Advisors LLC</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD COLSPAN="3"><FONT STYLE="font-family: Times New Roman, Times, Serif; font-size: 10pt"><B>OrbiMed Capital GP VI LLC</B></FONT></TD></TR>

<TR STYLE="vertical-align: top; text-align: left">
    <TD>&nbsp;</TD>
    <TD COLSPAN="3"><FONT STYLE="font-size: 10pt">By: OrbiMed Advisors LLC, Its Managing Member</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    </TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">By:</FONT></TD>
    <TD COLSPAN="2" STYLE="border-bottom: Black 1pt solid"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">/s/ Jonathan T. Silverstein</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Name:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Jonathan T. Silverstein</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Title:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Member of OrbiMed Advisors LLC</TD></TR>
    <TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">By:</FONT></TD>
    <TD COLSPAN="2" STYLE="border-bottom: Black 1pt solid"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">/s/ Sven H. Borho</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Name:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Sven H. Borho</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Title:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Member of OrbiMed Advisors LLC</TD></TR>
    <TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">By:</FONT></TD>
    <TD COLSPAN="2" STYLE="border-bottom: Black 1pt solid"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">/s/ Carl L. Gordon</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Name:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Carl L. Gordon</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Title:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Member of OrbiMed Advisors LLC</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>



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<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-WEIGHT: bold">CUSIP No.&#160;&#160;98420N105</div>
</td>
<td valign="top" width="40%">
<div style="TEXT-ALIGN: center"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt">&#160;<font style="DISPLAY: inline; FONT-WEIGHT: bold">SCHEDULE 13G/A</font></font></div>
</td>
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<div style="TEXT-ALIGN: right; TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 9pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: times new roman; FONT-SIZE: 10pt; FONT-WEIGHT: bold">Page&#160;8
of&#160;8 Pages</font></div>
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<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">&nbsp;</P>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>EXHIBIT A</U></B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>JOINT FILING AGREEMENT</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: justify">The undersigned hereby agree that
the Statement on this Schedule 13G dated February 13, 2018 (the "Schedule 13G/A"), with respect to the Common Stock, without
par value, of Xenon Pharmaceuticals Inc. is filed on behalf of each of us pursuant to and in accordance with
the provisions of Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, and that this Agreement shall be
included as an Exhibit to this Schedule 13G/A. Each of the undersigned agrees to be responsible for the timely filing of the
Schedule 13G/A, 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.</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">IN WITNESS WHEREOF, the undersigned have executed this Agreement as of February 13, 2018.</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"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></P>

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

<TABLE CELLPADDING="0" CELLSPACING="0" STYLE="border-collapse: collapse; width: 100%">
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD COLSPAN="3"><FONT STYLE="font-family: Times New Roman, Times, Serif; font-size: 10pt"><B>OrbiMed Advisors LLC</B></FONT></TD></TR>

<TR STYLE="vertical-align: top; text-align: left">
    <TD STYLE="width: 52%"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD STYLE="width: 3%"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD STYLE="width: 2%"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD STYLE="width: 43%"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">By:</FONT></TD>
    <TD COLSPAN="2" STYLE="border-bottom: Black 1pt solid"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">/s/ Jonathan T. Silverstein</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Name:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Jonathan T. Silverstein</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Title:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Member of OrbiMed Advisors LLC</TD></TR>
    <TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">By:</FONT></TD>
    <TD COLSPAN="2" STYLE="border-bottom: Black 1pt solid"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">/s/ Sven H. Borho</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Name:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Sven H. Borho</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Title:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Member of OrbiMed Advisors LLC</TD></TR>
    <TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">By:</FONT></TD>
    <TD COLSPAN="2" STYLE="border-bottom: Black 1pt solid"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">/s/ Carl L. Gordon</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Name:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Carl L. Gordon</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Title:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Member of OrbiMed Advisors LLC</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD COLSPAN="3"><FONT STYLE="font-family: Times New Roman, Times, Serif; font-size: 10pt"><B>OrbiMed Capital GP VI LLC</B></FONT></TD></TR>

<TR STYLE="vertical-align: top; text-align: left">
    <TD>&nbsp;</TD>
    <TD COLSPAN="3"><FONT STYLE="font-size: 10pt">By: OrbiMed Advisors LLC, Its Managing Member</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    </TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">By:</FONT></TD>
    <TD COLSPAN="2" STYLE="border-bottom: Black 1pt solid"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">/s/ Jonathan T. Silverstein</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Name:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Jonathan T. Silverstein</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Title:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Member of OrbiMed Advisors LLC</TD></TR>
    <TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">By:</FONT></TD>
    <TD COLSPAN="2" STYLE="border-bottom: Black 1pt solid"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">/s/ Sven H. Borho</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Name:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Sven H. Borho</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Title:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Member of OrbiMed Advisors LLC</TD></TR>
    <TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">By:</FONT></TD>
    <TD COLSPAN="2" STYLE="border-bottom: Black 1pt solid"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">/s/ Carl L. Gordon</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Name:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Carl L. Gordon</TD></TR>
<TR STYLE="vertical-align: top; text-align: left">
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Title:</FONT></TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">&nbsp;Member of OrbiMed Advisors LLC</TD></TR>
</TABLE>
<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: justify"></P>

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