<SEC-DOCUMENT>0001144204-13-008965.txt : 20130214
<SEC-HEADER>0001144204-13-008965.hdr.sgml : 20130214
<ACCEPTANCE-DATETIME>20130214150940
ACCESSION NUMBER:		0001144204-13-008965
CONFORMED SUBMISSION TYPE:	SC 13G/A
PUBLIC DOCUMENT COUNT:		1
FILED AS OF DATE:		20130214
DATE AS OF CHANGE:		20130214
GROUP MEMBERS:		PETER KOLCHINSKY
GROUP MEMBERS:		RA CAPITAL HEALTHCARE FUND, L.P.

SUBJECT COMPANY:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			XOMA Corp
		CENTRAL INDEX KEY:			0000791908
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				942756657
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		SC 13G/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	005-38028
		FILM NUMBER:		13612600

	BUSINESS ADDRESS:	
		STREET 1:		2910 SEVENTH ST
		CITY:			BERKELEY
		STATE:			CA
		ZIP:			94710
		BUSINESS PHONE:		5106441170

	MAIL ADDRESS:	
		STREET 1:		2910 SEVENTH ST
		CITY:			BERKLEY
		STATE:			CA
		ZIP:			94710

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	XOMA LTD /DE/
		DATE OF NAME CHANGE:	19990107

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	XOMA CORP /DE/
		DATE OF NAME CHANGE:	19920703

FILED BY:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			RA CAPITAL MANAGEMENT, LLC
		CENTRAL INDEX KEY:			0001346824
		IRS NUMBER:				830406777
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		SC 13G/A

	BUSINESS ADDRESS:	
		STREET 1:		20 PARK PLAZA, SUITE 1200
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116
		BUSINESS PHONE:		617-778-2500

	MAIL ADDRESS:	
		STREET 1:		20 PARK PLAZA, SUITE 1200
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116
</SEC-HEADER>
<DOCUMENT>
<TYPE>SC 13G/A
<SEQUENCE>1
<FILENAME>v335102_sc13ga.htm
<DESCRIPTION>SC 13G/A
<TEXT>
<HTML>
<HEAD>
     <TITLE></TITLE>
</HEAD>
<BODY STYLE="font: 10pt Times New Roman, Times, Serif">

<P STYLE="margin: 0"></P>

<P STYLE="margin: 0"></P>

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

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

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><B>SCHEDULE 13G</B>&nbsp;</P>

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

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center; text-indent: 0in"><B>(Amendment No. 1)*</B></P>

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

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 100%; text-align: center; font-size: 10pt; font-weight: bold">XOMA Corporation</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid; text-align: center; font-size: 10pt; font-weight: bold">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="font-size: 10pt; text-align: center">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="font-size: 10pt; text-align: center">(Name of Issuer)</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="font-size: 10pt; font-weight: bold; text-align: center">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="font-size: 10pt; font-weight: bold; text-align: center"><FONT STYLE="color: black"><B>Common shares, $0.0075 par value</B></FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid; font-size: 10pt; font-weight: bold; text-align: center">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="font-size: 10pt; text-align: center">(Title of Class of Securities)</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="font-size: 10pt; font-weight: bold; text-align: center">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="font-size: 10pt; font-weight: bold; text-align: center">98419J107</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid; font-size: 10pt; font-weight: bold; text-align: center">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="font-size: 10pt; text-align: center">(CUSIP Number)</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="font-size: 10pt; font-weight: bold; text-align: center">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="font-size: 10pt; font-weight: bold; text-align: center">December 31, 2012</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid; font-size: 10pt; font-weight: bold; text-align: center">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="font-size: 10pt; 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: 0pt 0">&nbsp;</P>

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

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%">
<TR>
    <TD STYLE="vertical-align: top; width: 5%; font-family: Times New Roman, Times, Serif">&nbsp;</TD>
    <TD STYLE="width: 5%; font-family: Wingdings"><FONT STYLE="font: 10pt Wingdings">&uml;</FONT></TD>
    <TD STYLE="width: 90%">Rule 13d-1(b)</TD></TR>
<TR>
    <TD STYLE="vertical-align: top; font-family: Times New Roman, Times, Serif">&nbsp;</TD>
    <TD STYLE="font-family: Wingdings"><FONT STYLE="font: 10pt Wingdings">x</FONT></TD>
    <TD>Rule 13d-1(c)</TD></TR>
<TR>
    <TD STYLE="vertical-align: top; font-family: Times New Roman, Times, Serif">&nbsp;</TD>
    <TD STYLE="font-family: Wingdings"><FONT STYLE="font: 10pt Wingdings">&uml;</FONT></TD>
    <TD>Rule 13d-1(d)</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

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

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


<!-- Field: Page; Sequence: 1 -->
    <DIV STYLE="margin-top: 12pt; margin-bottom: 6pt; border-bottom: Black 1pt solid"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="width: 100%; font: 10pt Times New Roman, Times, Serif"><TR><TD STYLE="text-align: center; width: 100%">&nbsp;</TD></TR></TABLE></DIV>
    <DIV STYLE="page-break-before: always; margin-top: 6pt; margin-bottom: 12pt"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="width: 100%; font: 10pt Times New Roman, Times, Serif"><TR><TD STYLE="text-align: center; width: 100%">&nbsp;</TD></TR></TABLE></DIV>
    <!-- Field: /Page -->

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

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

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

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 45%; font-size: 10pt"><FONT STYLE="font-size: 10pt">CUSIP No. <B>98419J107</B></FONT></TD>
    <TD STYLE="width: 10%; font-size: 12pt; font-weight: bold; text-align: center"><FONT STYLE="font-size: 12pt"><B>13G</B></FONT></TD>
    <TD STYLE="width: 45%; font-size: 10pt; text-align: right"><FONT STYLE="font-size: 10pt">Page <U> <B>2</B> </U> of <U><B>7</B></U> Pages</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid; font-size: 10pt">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid; font-size: 12pt; font-weight: bold; text-align: center">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid; font-size: 10pt; text-align: right">&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">1.</FONT></TD>
    <TD COLSPAN="3"><FONT STYLE="font-size: 10pt">Names of Reporting Persons.</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="3"><FONT STYLE="font-size: 10pt">I.R.S. Identification Nos. of above persons (entities only).</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="3">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="3" STYLE="font-weight: bold; padding-left: 0.25in"><FONT STYLE="font-size: 10pt"><B>RA Capital Management, LLC</B></FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="3" STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="3">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">2. </FONT></TD>
    <TD COLSPAN="3"><FONT STYLE="font-size: 10pt">Check the Appropriate Box if a Member of a Group (See Instructions)</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">(a)</FONT></TD>
    <TD COLSPAN="2" STYLE="font-family: Wingdings"><FONT STYLE="font: 10pt Wingdings">&uml;</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">(b)</FONT></TD>
    <TD COLSPAN="2" STYLE="font-family: Wingdings"><FONT STYLE="font: 10pt Wingdings">&uml;</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="3" STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="3">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">3.</FONT></TD>
    <TD COLSPAN="3"><FONT STYLE="font-size: 10pt">SEC Use Only </FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="2" STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid; font-weight: bold">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2">&nbsp;</TD>
    <TD STYLE="font-weight: bold">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">4.</FONT></TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">Citizenship or Place of Organization</FONT></TD>
    <TD STYLE="font-weight: bold"><FONT STYLE="font-size: 10pt"><B>Massachusetts</B></FONT></TD></TR>
<TR>
    <TD STYLE="width: 5%">&nbsp;</TD>
    <TD STYLE="width: 5%">&nbsp;</TD>
    <TD STYLE="width: 5%">&nbsp;</TD>
    <TD STYLE="width: 35%">&nbsp;</TD>
    <TD STYLE="width: 50%">&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"></P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 13%; border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 4%; border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 31%; border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 13%; border-top: windowtext 1pt solid; font-weight: bold; text-align: right">&nbsp;</TD>
    <TD STYLE="width: 39%; border-top: Black 1pt solid">&nbsp;</TD></TR>
<TR>
    <TD ROWSPAN="10"><FONT STYLE="font-size: 10pt">Number of</FONT><BR>
<FONT STYLE="font-size: 10pt">Shares</FONT><BR>
<FONT STYLE="font-size: 10pt">Beneficially</FONT><BR>
<FONT STYLE="font-size: 10pt">Owned by</FONT><BR>
<FONT STYLE="font-size: 10pt">Each Reporting</FONT><BR>
<FONT STYLE="font-size: 10pt">Person With</FONT></TD>
    <TD STYLE="vertical-align: top"><FONT STYLE="font-size: 10pt">5.</FONT></TD>
    <TD STYLE="vertical-align: top"><FONT STYLE="font-size: 10pt">Sole Voting Power</FONT></TD>
    <TD STYLE="vertical-align: top; font-weight: bold; text-align: right"><P STYLE="margin-top: 0pt; text-align: right; margin-bottom: 0pt">6,698,558</P>


<FONT STYLE="font-size: 10pt"><B></B></FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: right">&nbsp;</TD>
    <TD STYLE="border-bottom: Black 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid; text-align: right">&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD><FONT STYLE="font-size: 10pt">6.</FONT></TD>
    <TD><FONT STYLE="font-size: 10pt">Shared Voting Power</FONT></TD>
    <TD STYLE="font-weight: bold; text-align: right"><FONT STYLE="font-size: 10pt"><B>0</B></FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: right">&nbsp;</TD>
    <TD STYLE="border-bottom: Black 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid; text-align: right">&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD><FONT STYLE="font-size: 10pt">7.</FONT></TD>
    <TD><FONT STYLE="font-size: 10pt">Sole Dispositive Power</FONT></TD>
    <TD STYLE="font-weight: bold; text-align: right"><P STYLE="margin-top: 0pt; text-align: right; margin-bottom: 0pt">6,698,558</P>


<FONT STYLE="font-size: 10pt"><B></B></FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: right">&nbsp;</TD>
    <TD STYLE="border-bottom: Black 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid; text-align: right">&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD><FONT STYLE="font-size: 10pt">8.</FONT></TD>
    <TD><FONT STYLE="font-size: 10pt">Shared Dispositive Power</FONT></TD>
    <TD STYLE="font-weight: bold; text-align: right"><FONT STYLE="font-size: 10pt"><B>0</B></FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid; font-weight: bold; text-align: right">&nbsp;</TD>
    <TD STYLE="border-bottom: Black 1pt solid">&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">9.</FONT></TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">Aggregate Amount Beneficially Owned by Each Reporting Person </FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2" STYLE="padding-left: 0.25in; font-weight: bold"><FONT STYLE="font-size: 10pt"><B>6,698,558</B></FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 5%; border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 5%; border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 60%; border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 30%; border-bottom: windowtext 1pt solid; font-family: Times New Roman, Times, Serif">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD STYLE="font-family: Times New Roman, Times, Serif">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">10.</FONT></TD>
    <TD><FONT STYLE="font-size: 10pt">Check if the Aggregate Amount in Row (9) Excludes</FONT></TD>
    <TD STYLE="font-family: Wingdings"><FONT STYLE="font: 10pt Wingdings">&uml;</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">Certain Shares (See Instructions)</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="2" STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">11.</FONT></TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">Percent of Class Represented by Amount in Row (9) </FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2" STYLE="padding-left: 0.25in; font-weight: bold"><FONT STYLE="font-size: 10pt"><B>8.2%</B></FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="2" STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">12.</FONT></TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">Type of Reporting Person (See Instructions)</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2" STYLE="padding-left: 0.25in; font-weight: bold"><FONT STYLE="font-size: 10pt"><B>IA</B></FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="2" STYLE="border-bottom: windowtext 1pt solid; padding-left: 0.25in; font-weight: bold">&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

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

<!-- Field: Page; Sequence: 2 -->
    <DIV STYLE="margin-top: 12pt; margin-bottom: 6pt; border-bottom: Black 1pt solid"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="width: 100%; font: 10pt Times New Roman, Times, Serif"><TR><TD STYLE="text-align: center; width: 100%">&nbsp;</TD></TR></TABLE></DIV>
    <DIV STYLE="page-break-before: always; margin-top: 6pt; margin-bottom: 12pt"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="width: 100%; font: 10pt Times New Roman, Times, Serif"><TR><TD STYLE="text-align: center; width: 100%">&nbsp;</TD></TR></TABLE></DIV>
    <!-- Field: /Page -->
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>



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

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

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

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 45%; font-size: 10pt"><FONT STYLE="font-size: 10pt">CUSIP No. <B>98419J107</B></FONT></TD>
    <TD STYLE="width: 10%; font-size: 12pt; font-weight: bold; text-align: center"><FONT STYLE="font-size: 12pt"><B>13G</B></FONT></TD>
    <TD STYLE="width: 45%; font-size: 10pt; text-align: right"><FONT STYLE="font-size: 10pt">Page <U> <B>3</B> </U> of <U> <B>7</B> </U> Pages</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid; font-size: 10pt">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid; font-size: 12pt; font-weight: bold; text-align: center">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid; font-size: 10pt; text-align: right">&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">1.</FONT></TD>
    <TD COLSPAN="3"><FONT STYLE="font-size: 10pt">Names of Reporting Persons.</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="3"><FONT STYLE="font-size: 10pt">I.R.S. Identification Nos. of above persons (entities only).</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="3">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="3" STYLE="font-weight: bold; padding-left: 0.25in"><FONT STYLE="font-size: 10pt"><B>Peter Kolchinsky</B></FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="3" STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="3">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">2. </FONT></TD>
    <TD COLSPAN="3"><FONT STYLE="font-size: 10pt">Check the Appropriate Box if a Member of a Group (See Instructions)</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">(a)</FONT></TD>
    <TD COLSPAN="2" STYLE="font-family: Wingdings"><FONT STYLE="font: 10pt Wingdings">&uml;</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">(b)</FONT></TD>
    <TD COLSPAN="2" STYLE="font-family: Wingdings"><FONT STYLE="font: 10pt Wingdings">&uml;</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="3" STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="3">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">3.</FONT></TD>
    <TD COLSPAN="3"><FONT STYLE="font-size: 10pt">SEC Use Only </FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="2" STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid; font-weight: bold">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2">&nbsp;</TD>
    <TD STYLE="font-weight: bold">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">4.</FONT></TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">Citizenship or Place of Organization</FONT></TD>
    <TD STYLE="font-weight: bold"><FONT STYLE="font-size: 10pt"><B>United States</B></FONT></TD></TR>
<TR>
    <TD STYLE="width: 5%">&nbsp;</TD>
    <TD STYLE="width: 5%">&nbsp;</TD>
    <TD STYLE="width: 5%">&nbsp;</TD>
    <TD STYLE="width: 35%">&nbsp;</TD>
    <TD STYLE="width: 50%">&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"></P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 13%; border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 4%; border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 31%; border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 13%; border-top: windowtext 1pt solid; font-weight: bold; text-align: right">&nbsp;</TD>
    <TD STYLE="width: 39%; border-top: Black 1pt solid">&nbsp;</TD></TR>
<TR>
    <TD ROWSPAN="10"><FONT STYLE="font-size: 10pt">Number of</FONT><BR>
<FONT STYLE="font-size: 10pt">Shares</FONT><BR>
<FONT STYLE="font-size: 10pt">Beneficially</FONT><BR>
<FONT STYLE="font-size: 10pt">Owned by</FONT><BR>
<FONT STYLE="font-size: 10pt">Each Reporting</FONT><BR>
<FONT STYLE="font-size: 10pt">Person With</FONT></TD>
    <TD STYLE="vertical-align: top"><FONT STYLE="font-size: 10pt">5.</FONT></TD>
    <TD STYLE="vertical-align: top"><FONT STYLE="font-size: 10pt">Sole Voting Power</FONT></TD>
    <TD STYLE="vertical-align: top; font-weight: bold; text-align: right"><P STYLE="margin-top: 0pt; text-align: right; margin-bottom: 0pt">6,698,558</P>


<FONT STYLE="font-size: 10pt"><B></B></FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: right">&nbsp;</TD>
    <TD STYLE="border-bottom: Black 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid; text-align: right">&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD><FONT STYLE="font-size: 10pt">6.</FONT></TD>
    <TD><FONT STYLE="font-size: 10pt">Shared Voting Power</FONT></TD>
    <TD STYLE="font-weight: bold; text-align: right"><FONT STYLE="font-size: 10pt"><B>0</B></FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: right">&nbsp;</TD>
    <TD STYLE="border-bottom: Black 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid; text-align: right">&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD><FONT STYLE="font-size: 10pt">7.</FONT></TD>
    <TD><FONT STYLE="font-size: 10pt">Sole Dispositive Power</FONT></TD>
    <TD STYLE="font-weight: bold; text-align: right"><P STYLE="margin-top: 0pt; text-align: right; margin-bottom: 0pt">6,698,558</P>


<FONT STYLE="font-size: 10pt"><B></B></FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: right">&nbsp;</TD>
    <TD STYLE="border-bottom: Black 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid; text-align: right">&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD><FONT STYLE="font-size: 10pt">8.</FONT></TD>
    <TD><FONT STYLE="font-size: 10pt">Shared Dispositive Power</FONT></TD>
    <TD STYLE="font-weight: bold; text-align: right"><FONT STYLE="font-size: 10pt"><B>0</B></FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid; font-weight: bold; text-align: right">&nbsp;</TD>
    <TD STYLE="border-bottom: Black 1pt solid">&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">9.</FONT></TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">Aggregate Amount Beneficially Owned by Each Reporting Person </FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2" STYLE="padding-left: 0.25in; font-weight: bold"><FONT STYLE="font-size: 10pt"><B>6,698,558</B></FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 5%; border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 5%; border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 60%; border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 30%; border-bottom: windowtext 1pt solid; font-family: Times New Roman, Times, Serif">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD STYLE="font-family: Times New Roman, Times, Serif">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">10.</FONT></TD>
    <TD><FONT STYLE="font-size: 10pt">Check if the Aggregate Amount in Row (9) Excludes</FONT></TD>
    <TD STYLE="font-family: Wingdings"><FONT STYLE="font: 10pt Wingdings">&uml;</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">Certain Shares (See Instructions)</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="2" STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">11.</FONT></TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">Percent of Class Represented by Amount in Row (9) </FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2" STYLE="padding-left: 0.25in; font-weight: bold">8.2<FONT STYLE="font-size: 10pt"><B>%</B></FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="2" STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">12.</FONT></TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">Type of Reporting Person (See Instructions)</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2" STYLE="padding-left: 0.25in; font-weight: bold"><FONT STYLE="font-size: 10pt"><B>IN</B></FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="2" STYLE="border-bottom: windowtext 1pt solid; padding-left: 0.25in; font-weight: bold">&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

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

<!-- Field: Page; Sequence: 3 -->
    <DIV STYLE="margin-top: 12pt; margin-bottom: 6pt; border-bottom: Black 1pt solid"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="width: 100%; font: 10pt Times New Roman, Times, Serif"><TR><TD STYLE="text-align: center; width: 100%">&nbsp;</TD></TR></TABLE></DIV>
    <DIV STYLE="page-break-before: always; margin-top: 6pt; margin-bottom: 12pt"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="width: 100%; font: 10pt Times New Roman, Times, Serif"><TR><TD STYLE="text-align: center; width: 100%">&nbsp;</TD></TR></TABLE></DIV>
    <!-- Field: /Page -->

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

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

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

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 45%; font-size: 10pt"><FONT STYLE="font-size: 10pt">CUSIP No. <B>98419J107</B></FONT></TD>
    <TD STYLE="width: 10%; font-size: 12pt; font-weight: bold; text-align: center"><FONT STYLE="font-size: 12pt"><B>13G</B></FONT></TD>
    <TD STYLE="width: 45%; font-size: 10pt; text-align: right"><FONT STYLE="font-size: 10pt">Page <U> <B>4</B> </U> of <U> <B>7</B> </U> Pages</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid; font-size: 10pt">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid; font-size: 12pt; font-weight: bold; text-align: center">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid; font-size: 10pt; text-align: right">&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">1.</FONT></TD>
    <TD COLSPAN="3"><FONT STYLE="font-size: 10pt">Names of Reporting Persons.</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="3"><FONT STYLE="font-size: 10pt">I.R.S. Identification Nos. of above persons (entities only).</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="3">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="3" STYLE="font-weight: bold; padding-left: 0.25in"><FONT STYLE="font-size: 10pt"><B>RA Capital Healthcare Fund, L.P.</B></FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="3" STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="3">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">2. </FONT></TD>
    <TD COLSPAN="3"><FONT STYLE="font-size: 10pt">Check the Appropriate Box if a Member of a Group (See Instructions)</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">(a)</FONT></TD>
    <TD COLSPAN="2" STYLE="font-family: Wingdings"><FONT STYLE="font: 10pt Wingdings">&uml;</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">(b)</FONT></TD>
    <TD COLSPAN="2" STYLE="font-family: Wingdings"><FONT STYLE="font: 10pt Wingdings">&uml;</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="3" STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="3">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">3.</FONT></TD>
    <TD COLSPAN="3"><FONT STYLE="font-size: 10pt">SEC Use Only </FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="2" STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid; font-weight: bold">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2">&nbsp;</TD>
    <TD STYLE="font-weight: bold">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">4.</FONT></TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">Citizenship or Place of Organization</FONT></TD>
    <TD STYLE="font-weight: bold"><FONT STYLE="font-size: 10pt"><B>Delaware</B></FONT></TD></TR>
<TR>
    <TD STYLE="width: 5%">&nbsp;</TD>
    <TD STYLE="width: 5%">&nbsp;</TD>
    <TD STYLE="width: 5%">&nbsp;</TD>
    <TD STYLE="width: 35%">&nbsp;</TD>
    <TD STYLE="width: 50%">&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"></P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 13%; border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 4%; border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 31%; border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 13%; border-top: windowtext 1pt solid; font-weight: bold; text-align: right">&nbsp;</TD>
    <TD STYLE="width: 39%; border-top: Black 1pt solid">&nbsp;</TD></TR>
<TR>
    <TD ROWSPAN="10"><FONT STYLE="font-size: 10pt">Number of</FONT><BR>
<FONT STYLE="font-size: 10pt">Shares</FONT><BR>
<FONT STYLE="font-size: 10pt">Beneficially</FONT><BR>
<FONT STYLE="font-size: 10pt">Owned by</FONT><BR>
<FONT STYLE="font-size: 10pt">Each Reporting</FONT><BR>
<FONT STYLE="font-size: 10pt">Person With</FONT></TD>
    <TD STYLE="vertical-align: top"><FONT STYLE="font-size: 10pt">5.</FONT></TD>
    <TD STYLE="vertical-align: top"><FONT STYLE="font-size: 10pt">Sole Voting Power</FONT></TD>
    <TD STYLE="vertical-align: top; font-weight: bold; text-align: right"><P STYLE="margin-top: 0pt; text-align: right; margin-bottom: 0pt">3,921,042</P>


<FONT STYLE="font-size: 10pt"><B></B></FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: right">&nbsp;</TD>
    <TD STYLE="border-bottom: Black 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid; text-align: right">&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD><FONT STYLE="font-size: 10pt">6.</FONT></TD>
    <TD><FONT STYLE="font-size: 10pt">Shared Voting Power</FONT></TD>
    <TD STYLE="font-weight: bold; text-align: right"><FONT STYLE="font-size: 10pt"><B>0</B></FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: right">&nbsp;</TD>
    <TD STYLE="border-bottom: Black 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid; text-align: right">&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD><FONT STYLE="font-size: 10pt">7.</FONT></TD>
    <TD><FONT STYLE="font-size: 10pt">Sole Dispositive Power</FONT></TD>
    <TD STYLE="font-weight: bold; text-align: right"><P STYLE="margin-top: 0pt; text-align: right; margin-bottom: 0pt">3,921,042</P>


<FONT STYLE="font-size: 10pt"><B></B></FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: right">&nbsp;</TD>
    <TD STYLE="border-bottom: Black 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-top: windowtext 1pt solid; text-align: right">&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD><FONT STYLE="font-size: 10pt">8.</FONT></TD>
    <TD><FONT STYLE="font-size: 10pt">Shared Dispositive Power</FONT></TD>
    <TD STYLE="font-weight: bold; text-align: right"><FONT STYLE="font-size: 10pt"><B>0</B></FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid; font-weight: bold; text-align: right">&nbsp;</TD>
    <TD STYLE="border-bottom: Black 1pt solid">&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">9.</FONT></TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">Aggregate Amount Beneficially Owned by Each Reporting Person </FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2" STYLE="padding-left: 0.25in; font-weight: bold"><FONT STYLE="font-size: 10pt"><B>3,921,042</B></FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 5%; border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 5%; border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 60%; border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="width: 30%; border-bottom: windowtext 1pt solid; font-family: Times New Roman, Times, Serif">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD STYLE="font-family: Times New Roman, Times, Serif">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">10.</FONT></TD>
    <TD><FONT STYLE="font-size: 10pt">Check if the Aggregate Amount in Row (9) Excludes</FONT></TD>
    <TD STYLE="font-family: Wingdings"><FONT STYLE="font: 10pt Wingdings">&uml;</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">Certain Shares (See Instructions)</FONT></TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="2" STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">11.</FONT></TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">Percent of Class Represented by Amount in Row (9) </FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2" STYLE="padding-left: 0.25in; font-weight: bold">4<FONT STYLE="font-size: 10pt"><B>.8%</B></FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="2" STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2">&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">12.</FONT></TD>
    <TD COLSPAN="2"><FONT STYLE="font-size: 10pt">Type of Reporting Person (See Instructions)</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD COLSPAN="2" STYLE="padding-left: 0.25in; font-weight: bold"><FONT STYLE="font-size: 10pt"><B>PN</B></FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">&nbsp;</TD>
    <TD COLSPAN="2" STYLE="border-bottom: windowtext 1pt solid; padding-left: 0.25in; font-weight: bold">&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

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

<!-- Field: Page; Sequence: 4 -->
    <DIV STYLE="margin-top: 12pt; margin-bottom: 6pt; border-bottom: Black 1pt solid"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="width: 100%; font: 10pt Times New Roman, Times, Serif"><TR><TD STYLE="text-align: center; width: 100%">&nbsp;</TD></TR></TABLE></DIV>
    <DIV STYLE="page-break-before: always; margin-top: 6pt; margin-bottom: 12pt"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="width: 100%; font: 10pt Times New Roman, Times, Serif"><TR><TD STYLE="text-align: center; width: 100%">&nbsp;</TD></TR></TABLE></DIV>
    <!-- Field: /Page -->
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 66%; font-size: 10pt"><FONT STYLE="font-size: 10pt">CUSIP No. <B>98419J107</B></FONT></TD>
    <TD STYLE="width: 34%; font-size: 10pt; text-align: right">Page 5 of 7</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>&nbsp;</B></P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>Item 1.</B></P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">(a)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>Name
of Issuer:</B> XOMA Corporation (the &ldquo;Issuer&rdquo;).</P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">(b)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>Address
of the Issuer&rsquo;s Principal Executive Offices:</B> 2910 Seventh Street, Berkeley, California 94710.</P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>Item 2.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</B></P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0in">(a)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>Name
of Person Filing: </B> This joint statement on Schedule 13G is being filed by Peter Kolchinsky, RA Capital Management, LLC, and
RA Capital Healthcare Fund, L.P., who are collectively referred to herein as the &ldquo;Reporting Persons.&rdquo; Mr. Kolchinsky
(the &ldquo;Manager&rdquo;) is the manager of RA Capital Management, LLC (&ldquo;Capital&rdquo;), which is the investment adviser
and sole general partner of RA Capital Healthcare Fund, L.P. (&ldquo;Fund&rdquo;) and serves as the investment adviser to a separate
discretionary account. The Reporting Persons have entered into a Joint Filing Agreement, dated as of the date hereof, a copy of
which is filed with this Schedule 13G as <U>Exhibit 1</U> (which is incorporated herein by reference), pursuant to which the Reporting
Persons have agreed to file this statement jointly in accordance with the provisions of Rule 13d-1(k) under the Act.</P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0in">(b)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>Address
of Principal Business Office:</B> The principal business office of the Reporting Persons with respect to the shares reported hereunder
is 20 Park Plaza, Suite 1200, Boston, MA 02116.</P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0in">(c)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>Citizenship:
</B>Capital is a Massachusetts limited liability company. The Fund is a Delaware limited partnership. The Manager is a United
States citizen.</P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0in">(d)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>Title
and Class of Securities: </B>Common stock (&ldquo;Common Stock&rdquo;).</P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0in">(e)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>CUSIP
Number:</B> 98419J107.</P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>Item 3.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If
this statement is filed pursuant to &sect;&sect;240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:</B></P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">Not applicable.</P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>Item 4.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</B><B>Ownership:</B></P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">As of January 31, 2013, the Reporting Persons, in the aggregate,
beneficially own 6,698,558 shares of the Common Stock of the Issuer, representing approximately 8.2% of such class of securities.
The Reporting Persons have the right to purchase an additional 687,879 shares of Common Stock pursuant to the terms<B> </B>of the
Warrant to Purchase Common Stock issued on March 09, 2012, which are not exercisable to the extent that, following such exercise,
the total number of shares of Common Stock then beneficially owned by the Reporting Persons does not exceed 4.999% of the total
number of then issued and outstanding shares of Common Stock (including for such purpose the shares of Common Stock issuable upon
such exercise). This 4.999% limitation shall cease to apply from and after the date fourteen days prior to the Expiration Date.
The beneficial ownership of each Reporting Person is as follows: (i) Fund beneficially owns 3,921,042 shares of Common Stock, representing
approximately 4.8% of the class and (ii) Capital, as the investment adviser and sole general partner of the Fund <FONT STYLE="font-style: normal">and&nbsp;investment
adviser to an account owned by a separate investment vehicle which holds shares of the Issuer's Common Stock, and </FONT>Mr. Kolchinsky
as the manager of Capital, each beneficially own 6,698,558 shares of Common Stock of the Issuer, representing approximately 8.2%
of the class. The percentage of Common Stock beneficially owned by each Reporting Person is based on a total of 81,555,931 shares
of Common Stock of the Issuer outstanding as reported on Issuer&rsquo;s Form 10-Q filed with the SEC on November 07, 2012.</P>

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


<!-- Field: Page; Sequence: 5 -->
    <DIV STYLE="margin-top: 12pt; margin-bottom: 6pt; border-bottom: Black 1pt solid"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="width: 100%; font: 10pt Times New Roman, Times, Serif"><TR><TD STYLE="text-align: center; width: 100%">&nbsp;</TD></TR></TABLE></DIV>
    <DIV STYLE="page-break-before: always; margin-top: 6pt; margin-bottom: 12pt"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="width: 100%; font: 10pt Times New Roman, Times, Serif"><TR><TD STYLE="text-align: center; width: 100%">&nbsp;</TD></TR></TABLE></DIV>
    <!-- Field: /Page -->

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

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 66%; font-size: 10pt"><FONT STYLE="font-size: 10pt">CUSIP No. <B>98419J107</B></FONT></TD>
    <TD STYLE="width: 34%; font-size: 10pt; text-align: right">Page 6 of 7</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">The Fund has the power to vote and dispose of the shares of
Common Stock beneficially owned by such entity (as described above). Capital, as the investment adviser and sole general partner
of the Fund and as the investment adviser&nbsp;to&nbsp;an account owned by a separate investment vehicle which holds<FONT STYLE="color: blue"><B><I>
</I></B></FONT>shares of the Issuer&rsquo;s Common Stock, has the sole authority to vote and dispose of all of the shares of Common
Stock reported in this Schedule 13G. The Manager, by virtue of his position as manager of Capital, has the sole authority to vote
and dispose of all of the shares of Common Stock reported in this Schedule 13G.</P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>Item 5.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#9;Ownership
of Five Percent or Less of a Class:</B></P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">Not applicable.</P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0 0pt 1in; text-indent: -1in"><B>Item 6.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Ownership
of More than Five Percent on Behalf of Another Person:</B></P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">Not applicable.</P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>Item 7.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Identification and Classification of the Subsidiary
Which Acquired the Security Being Reported on By the Parent Holding Company or Control Person:</B></P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">Not applicable.</P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>Item 8.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#9;Identification
and Classification of Members of the Group:</B></P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">Not applicable.</P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"><B>Item 9.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#9;Notice
of Dissolution of Group:</B></P>

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">Not applicable.</P>

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

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

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">By signing below I hereby certify that, to the best of my knowledge
and belief, the securities referred to above 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>

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


<!-- Field: Page; Sequence: 6 -->
    <DIV STYLE="margin-top: 12pt; margin-bottom: 6pt; border-bottom: Black 1pt solid"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="width: 100%; font: 10pt Times New Roman, Times, Serif"><TR><TD STYLE="text-align: center; width: 100%">&nbsp;</TD></TR></TABLE></DIV>
    <DIV STYLE="page-break-before: always; margin-top: 6pt; margin-bottom: 12pt"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="width: 100%; font: 10pt Times New Roman, Times, Serif"><TR><TD STYLE="text-align: center; width: 100%">&nbsp;</TD></TR></TABLE></DIV>
    <!-- Field: /Page -->

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

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 66%; font-size: 10pt"><FONT STYLE="font-size: 10pt">CUSIP No. <B>98419J107</B></FONT></TD>
    <TD STYLE="width: 34%; font-size: 10pt; text-align: right">Page 7 of 7</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><I>&nbsp;</I>&nbsp;</P>

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

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

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

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 50%">&nbsp;</TD>
    <TD STYLE="width: 50%"><FONT STYLE="text-transform: uppercase">Date: February 14, 2013</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>RA CAPITAL HEALTHCARE FUND, L.P.</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>By: RA Capital Management, LLC</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD STYLE="padding-left: 0.4in">General Partner</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">By: /s/ Peter Kolchinsky</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>Peter Kolchinsky</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>Manager</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>RA CAPITAL MANAGEMENT, LLC</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">By: /s/ Peter Kolchinsky</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>Peter Kolchinsky</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>Manager</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>PETER KOLCHINSKY</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid">/s/ Peter Kolchinsky</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0pt; text-align: left; margin-bottom: 0pt">&nbsp;</P>

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

<!-- Field: Page; Sequence: 7 -->
    <DIV STYLE="margin-top: 12pt; margin-bottom: 6pt; border-bottom: Black 1pt solid"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="width: 100%; font-size: 10pt"><TR><TD STYLE="text-align: center; width: 100%">&nbsp;</TD></TR></TABLE></DIV>
    <DIV STYLE="page-break-before: always; margin-top: 6pt; margin-bottom: 12pt"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="width: 100%"><TR><TD STYLE="text-align: center; width: 100%">&nbsp;</TD></TR></TABLE></DIV>
    <!-- Field: /Page -->
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0pt; text-align: left; margin-bottom: 0pt">&nbsp;</P>

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

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

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

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

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

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0; text-indent: 0.5in">Pursuant to Rule 13d-1(k)(1) under the Securities
Exchange Act of 1934, as amended, the undersigned hereby agrees, as of February 14, 2013, that only one statement containing the
information required by Schedule 13G, and each amendment thereto, need be filed with respect to the ownership by each of the undersigned
of shares of Common Stock of XOMA Corporation, and such statement to which this Joint Filing Agreement is attached as <U>Exhibit
1</U> is filed on behalf of each of the undersigned.</P>

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

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 50%">&nbsp;</TD>
    <TD STYLE="width: 50%"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">RA CAPITAL HEALTHCARE FUND, L.P.</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">By: RA Capital Management, LLC</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD STYLE="padding-left: 0.4in"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">General Partner</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">By: /s/ Peter Kolchinsky</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Peter Kolchinsky</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Manager</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">RA CAPITAL MANAGEMENT, LLC</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">By: /s/ Peter Kolchinsky</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Peter Kolchinsky</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">Manager</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD><FONT STYLE="font: 10pt Times New Roman, Times, Serif">PETER KOLCHINSKY</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD STYLE="border-bottom: windowtext 1pt solid"><FONT STYLE="font: 10pt Times New Roman, Times, Serif">/s/ Peter Kolchinsky</FONT></TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>

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

<!-- Field: Page; Sequence: 8; Options: Last -->
    <DIV STYLE="margin-top: 12pt; margin-bottom: 6pt; border-bottom: Black 1pt solid"><TABLE CELLPADDING="0" CELLSPACING="0" STYLE="width: 100%; font-size: 10pt"><TR><TD STYLE="text-align: center; width: 100%">&nbsp;</TD></TR></TABLE></DIV>
    <!-- Field: /Page -->
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0">&nbsp;</P>




</BODY>
</HTML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
