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<SEC-DOCUMENT>0000950123-10-024970.txt : 20100316
<SEC-HEADER>0000950123-10-024970.hdr.sgml : 20100316
<ACCEPTANCE-DATETIME>20100316080019
ACCESSION NUMBER:		0000950123-10-024970
CONFORMED SUBMISSION TYPE:	8-K
PUBLIC DOCUMENT COUNT:		5
CONFORMED PERIOD OF REPORT:	20100315
ITEM INFORMATION:		Entry into a Material Definitive Agreement
ITEM INFORMATION:		Unregistered Sales of Equity Securities
ITEM INFORMATION:		Financial Statements and Exhibits
FILED AS OF DATE:		20100316
DATE AS OF CHANGE:		20100316

FILER:

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			LEXICON PHARMACEUTICALS, INC./DE
		CENTRAL INDEX KEY:			0001062822
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				760474169
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		8-K
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-30111
		FILM NUMBER:		10683701

	BUSINESS ADDRESS:	
		STREET 1:		8800 TECHNOLOGY FOREST PLACE
		CITY:			THE WOODLANDS
		STATE:			TX
		ZIP:			77381
		BUSINESS PHONE:		2818633000

	MAIL ADDRESS:	
		STREET 1:		8800 TECHNOLOGY FOREST PLACE
		CITY:			THE WOODLANDS
		STATE:			TX
		ZIP:			77381

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	LEXICON GENETICS INC/TX
		DATE OF NAME CHANGE:	20000126
</SEC-HEADER>
<DOCUMENT>
<TYPE>8-K
<SEQUENCE>1
<FILENAME>h70209e8vk.htm
<DESCRIPTION>FORM 8-K
<TEXT>
<HTML>
<HEAD>
<TITLE>e8vk</TITLE>
</HEAD>
<BODY bgcolor="#FFFFFF">
<!-- PAGEBREAK -->
<H5 align="left" style="page-break-before:always"><A HREF="#toc">Table of Contents</A></H5><P>
<DIV style="font-family: 'Times New Roman',Times,serif">


<DIV style="width: 100%; border-bottom: 2pt solid black; font-size: 1pt">&nbsp;</DIV>
<DIV style="width: 100%; border-bottom: 1pt solid black; font-size: 1pt">&nbsp;</DIV>






<DIV align="center" style="font-size: 14pt; margin-top: 12pt"><B>UNITED STATES<BR>
SECURITIES AND EXCHANGE COMMISSION</B>
</DIV>

<DIV align="center" style="font-size: 12pt"><B>Washington, D.C. 20549</B>
</DIV>

<DIV align="center" style="font-size: 10pt; margin-top: 12pt">
<DIV align="center"><DIV style="font-size: 3pt; margin-top: 16pt; width: 26%; border-top: 1px solid #000000">&nbsp;</DIV></DIV></DIV>


<DIV align="center" style="font-size: 18pt; margin-top: 12pt"><B>FORM 8-K</B>
</DIV>

<DIV align="center" style="font-size: 10pt; margin-top: 12pt">
<DIV align="center"><DIV style="font-size: 3pt; margin-top: 16pt; width: 26%; border-top: 1px solid #000000">&nbsp;</DIV></DIV></DIV>



<DIV align="center" style="font-size: 12pt; margin-top: 12pt"><B>CURRENT REPORT<BR>
Pursuant to Section&nbsp;13 or 15(d) of the Securities Exchange Act of 1934</B>
</DIV>

<!-- xbrl,dc -->
<DIV align="center" style="font-size: 10pt; margin-top: 12pt"><B>
Date of Report (Date of earliest event reported): March&nbsp;15, 2010</B>
</DIV>
<!-- /xbrl,dc -->
<DIV align="center" style="font-size: 24pt; margin-top: 12pt"><B>Lexicon Pharmaceuticals, Inc.</B>
</DIV>

<DIV align="center" style="font-size: 10pt">
<B>(Exact name of registrant as specified in its charter)</B></DIV>


<DIV align="center">
<TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
<!-- Begin Table Head -->
<TR valign="bottom">
    <TD width="30%">&nbsp;</TD>
    <TD width="5%">&nbsp;</TD>
    <TD width="30%">&nbsp;</TD>
    <TD width="5%">&nbsp;</TD>
    <TD width="30%">&nbsp;</TD>
</TR>
<!-- End Table Head -->
<!-- Begin Table Body -->
<TR valign="bottom">
    <TD align="center" valign="top"><B>Delaware<BR>
(State or other jurisdiction of <BR>
incorporation or organization)</B>
</TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top"><B>000-30111<BR>
(Commission File Number)</B>
</TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top"><B>76-0474169<BR>
(I.R.S. Employer<BR>
Identification Number)</B></TD>
</TR>
<!-- End Table Body -->
</TABLE>
</DIV>

<DIV align="center" style="font-size: 10pt; margin-top: 12pt">
<B>8800 Technology Forest Place<BR>

The Woodlands, Texas 77381<BR>

(Address of principal executive<BR>

offices and Zip Code)</B></DIV>


<DIV align="center" style="font-size: 10pt; margin-top: 12pt">
<B>(281)&nbsp;863-3000<BR>

(Registrant&#146;s telephone number,<BR>

including area code)</B></DIV>



<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Check the appropriate box below if the Form 8-K filing is intended to simultaneously
satisfy the filing obligations of the registrant under any of the following provisions:
</DIV>

<DIV style="margin-top: 6pt">
<TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt">

<TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
    <TD width="3%" nowrap align="left"><FONT face="Wingdings">&#111;</FONT></TD>
    <TD width="1%">&nbsp;</TD>
    <TD>Written communications pursuant to Rule&nbsp;425 under the Securities Act (17 CFR 230.425)</TD>
</TR>

<TR>
    <TD style="font-size: 6pt">&nbsp;</TD>
</TR><TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
    <TD width="3%" nowrap align="left"><FONT face="Wingdings">&#111;</FONT></TD>
    <TD width="1%">&nbsp;</TD>
    <TD>Soliciting material pursuant to Rule&nbsp;14a-12 under the Exchange Act (17 CFR 240.14a-12)</TD>
</TR>

<TR>
    <TD style="font-size: 6pt">&nbsp;</TD>
</TR><TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
    <TD width="3%" nowrap align="left"><FONT face="Wingdings">&#111;</FONT></TD>
    <TD width="1%">&nbsp;</TD>
    <TD>Pre-commencement communications pursuant to Rule&nbsp;14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))</TD>
</TR>

<TR>
    <TD style="font-size: 6pt">&nbsp;</TD>
</TR><TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
    <TD width="3%" nowrap align="left"><FONT face="Wingdings">&#111;</FONT></TD>
    <TD width="1%">&nbsp;</TD>
    <TD>Pre-commencement communications pursuant to Rule&nbsp;13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))</TD>
</TR>

</TABLE>
</DIV>

<DIV style="width: 100%; border-bottom: 1pt solid black; margin-top: 10pt; font-size: 1pt">&nbsp;</DIV>
<DIV style="width: 100%; border-bottom: 2pt solid black; font-size: 1pt">&nbsp;</DIV>







<P align="center" style="font-size: 10pt"><!-- Folio -->&nbsp;<!-- /Folio -->
</DIV>

<!-- PAGEBREAK -->
<P><HR noshade><P>

<DIV style="font-family: 'Times New Roman',Times,serif">






<!-- TOC -->
<A name="toc"><DIV align="CENTER" style="page-break-before:always"><U><B>TABLE OF CONTENTS</B></U></DIV></A>

<P><CENTER>
<TABLE border="0" width="90%" cellpadding="0" cellspacing="0">
<TR>
	<TD width="3%"></TD>
	<TD width="3%"></TD>
	<TD width="3%"></TD>
	<TD width="3%"></TD>
	<TD width="3%"></TD>
	<TD width="3%"></TD>
	<TD width="3%"></TD>
	<TD width="3%"></TD>
	<TD width="76%"></TD>
</TR>
<TR><TD colspan="9"><A HREF="#000">Item&nbsp;1.01 Entry into a Material Definitive Agreement</A></TD></TR>
<TR><TD colspan="9"><A HREF="#001">Item&nbsp;3.02 Unregistered Sales of Equity Securities</A></TD></TR>
<TR><TD colspan="9"><A HREF="#002">Item&nbsp;9.01 Financial Statements and Exhibits</A></TD></TR>
<TR><TD colspan="9"><A HREF="#003">Signatures</A></TD></TR>
<TR><TD colspan="9"><A HREF="#004">Index to Exhibits</A></TD></TR>
<TR><TD colspan="9"><A HREF="h70209exv1w1.htm">EX-1.1</A></TD></TR>
<TR><TD colspan="9"><A HREF="h70209exv5w1.htm">EX-5.1</A></TD></TR>
<TR><TD colspan="9"><A HREF="h70209exv10w1.htm">EX-10.1</A></TD></TR>
<TR><TD colspan="9"><A HREF="h70209exv99w1.htm">EX-99.1</A></TD></TR>
</TABLE>
</CENTER>
<!-- /TOC -->
<P><HR noshade><P>
<H5 align="left" style="page-break-before:always"><A HREF="#toc">Table of Contents</A></H5><P>




<!-- link1 "Item&nbsp;1.01 Entry into a Material Definitive Agreement" -->
<DIV align="left"><A NAME="000"></A></DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 12pt"><B>Item&nbsp;1.01 Entry into a Material Definitive Agreement</B>
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;On March&nbsp;15, 2010, Lexicon Pharmaceuticals, Inc. (the &#147;<U>Company</U>&#148;) entered into an
Underwriting Agreement with Morgan Stanley &#038; Co. Incorporated, J.P. Morgan Securities Inc., Cowen
and Company, LLC and Thomas Weisel Partners LLC for the public offering, issuance and sale of
87,717,391 shares of the Company&#146;s common stock, par value $0.001 per share (the &#147;<U>Common
Stock</U>&#148;) for aggregate proceeds to the Company of $100.9&nbsp;million, plus an additional 8,804,348
shares of Common Stock solely to cover over-allotments, if any. An affiliate of Invus, L.P.
(&#147;<U>Invus</U>&#148;), the Company&#146;s largest stockholder, has agreed to purchase from the underwriters
29,021,739 of such shares.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;On March&nbsp;15, 2010, the Company also entered into a Purchase Agreement with Invus for the
purchase of 59,296,749 shares of Common Stock in a concurrent private placement for aggregate
proceeds to the Company of approximately $68.2&nbsp;million. These shares were issued to Invus in
reliance upon the exemptions from the registration requirements under the Securities Act of 1933,
as amended, pursuant to Section&nbsp;4(2) thereof and Regulation&nbsp;D thereunder. In issuing the shares of
Common Stock to Invus, the Company relied upon the representations and warranties of Invus in
support of the satisfaction of the conditions contained in Section&nbsp;4(2) and Regulation&nbsp;D.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;On March&nbsp;16, 2010, the Company issued a press release announcing the public offering and the
concurrent private placement.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The Underwriting Agreement, Purchase Agreement, and press release are filed as Exhibits 1.1,
10.1 and 99.1 to this report, respectively, and are each incorporated herein by reference.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The Company and Invus are also parties to a Securities Purchase Agreement, dated June&nbsp;17, 2007
and amended October&nbsp;7, 2009 and March&nbsp;15, 2010, a Registration Rights Agreement, dated June&nbsp;17,
2007, and amended March&nbsp;15, 2010, and a Stockholders&#146; Agreement dated June&nbsp;17, 2007.
</DIV>
<!-- link1 "Item&nbsp;3.02 Unregistered Sales of Equity Securities" -->
<DIV align="left"><A NAME="001"></A></DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 12pt"><B>Item&nbsp;3.02 Unregistered Sales of Equity Securities</B>
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The information set forth in Item&nbsp;1.01 is incorporated herein by reference.
</DIV>
<!-- link1 "Item&nbsp;9.01 Financial Statements and Exhibits" -->
<DIV align="left"><A NAME="002"></A></DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 12pt"><B>Item&nbsp;9.01 Financial Statements and Exhibits</B>
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(d)&nbsp;Exhibits
</DIV>
<DIV align="center">
<TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
<!-- Begin Table Head -->
<TR valign="bottom">
    <TD width="8%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="88%">&nbsp;</TD>
</TR>
<TR style="font-size: 8pt" valign="bottom">
    <TD nowrap align="left" style="border-bottom: 1px solid #000000"><B>Exhibit No.</B></TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" style="border-bottom: 1px solid #000000"><B>Description</B></TD>
</TR>

<!-- End Table Head -->
<!-- Begin Table Body -->
<TR valign="bottom">
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">1.1
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&#151;
</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Underwriting Agreement with Morgan Stanley &#038; Co.
Incorporated, J.P. Morgan Securities Inc., Cowen and
Company, LLC and Thomas Weisel Partners LLC dated March
15, 2010</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">5.1
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&#151;
</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Opinion of Vinson &#038; Elkins L.L.P.</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">10.1
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&#151;
</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Purchase Agreement with Invus, L.P. dated March&nbsp;15, 2010</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">23.1
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&#151;
</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Consent of Vinson &#038; Elkins L.L.P. (included in Exhibit&nbsp;5.1)</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">99.1
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&#151;
</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Press Release dated March&nbsp;16, 2010</TD>
</TR>
<!-- End Table Body -->
</TABLE>
</DIV>


<P align="center" style="font-size: 10pt"><!-- Folio -->2<!-- /Folio -->
</DIV>

<!-- PAGEBREAK -->
<P><HR noshade><P>
<H5 align="left" style="page-break-before:always"><A HREF="#toc">Table of Contents</A></H5><P>

<DIV style="font-family: 'Times New Roman',Times,serif">



<!-- link1 "Signatures" -->
<DIV align="left"><A NAME="003"></A></DIV>

<DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>Signatures</B>
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has
duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.
</DIV>

<TABLE width="100%" border="0" cellspacing="0" cellpadding="0" style="font-size: 10pt">
<TR>
    <TD width="48%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="35%">&nbsp;</TD>
    <TD width="15%">&nbsp;</TD>
</TR>
<TR>
    <TD valign="top" align="left">&nbsp;</TD>
    <TD colspan="3" align="left"><B>Lexicon Pharmaceuticals, Inc.</B><BR>
&nbsp;</TD>
    <TD>&nbsp;</TD>
</TR><TR>
    <TD align="left">Date:  March 16, 2010&nbsp;</TD>
    <TD valign="top">By:&nbsp;&nbsp;</TD>
    <TD colspan="2" style="border-bottom: 1px solid #000000" align="left">/s/ <FONT style="font-variant: SMALL-CAPS">Jeffrey L. Wade</FONT>
&nbsp;</TD>
    <TD>&nbsp;</TD>
</TR><TR>
    <TD align="left">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD colspan="2" align="left">Jeffrey L. Wade&nbsp;</TD>
    <TD>&nbsp;</TD>
</TR><TR>
    <TD align="left">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD colspan="2" align="left"><I>Executive Vice President and<br>
General Counsel</I>&nbsp;</TD>
    <TD>&nbsp;</TD>
</TR>
<TR>
    <TD colspan="5">&nbsp;</TD>
</TR>
</TABLE>

<P align="center" style="font-size: 10pt"><!-- Folio -->3<!-- /Folio -->
</DIV>

<!-- PAGEBREAK -->
<P><HR noshade><P>
<H5 align="left" style="page-break-before:always"><A HREF="#toc">Table of Contents</A></H5><P>

<DIV style="font-family: 'Times New Roman',Times,serif">



<!-- link1 "Index to Exhibits" -->
<DIV align="left"><A NAME="004"></A></DIV>

<DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>Index to Exhibits</B>
</DIV>

<DIV align="center">
<TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
<!-- Begin Table Head -->
<TR valign="bottom">
    <TD width="8%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="88%">&nbsp;</TD>
</TR>
<TR style="font-size: 8pt" valign="bottom">
    <TD nowrap align="left" style="border-bottom: 1px solid #000000"><B>Exhibit No.</B></TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" style="border-bottom: 1px solid #000000"><B>Description</B></TD>
</TR>

<!-- End Table Head -->
<!-- Begin Table Body -->
<TR valign="bottom">
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">1.1
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&#151;
</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Underwriting Agreement with Morgan Stanley &#038; Co.
Incorporated, J.P. Morgan Securities Inc., Cowen and
Company, LLC and Thomas Weisel Partners LLC dated March
15, 2010</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">5.1
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&#151;
</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Opinion of Vinson &#038; Elkins L.L.P.</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">10.1
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&#151;
</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Purchase Agreement with Invus, L.P. dated March&nbsp;15, 2010</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">23.1
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&#151;
</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Consent of Vinson &#038; Elkins L.L.P. (included in Exhibit&nbsp;5.1)</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD align="center" valign="top"><DIV style="margin-left:0px; text-indent:-0px">99.1
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="center" valign="top">&#151;
</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Press Release dated March&nbsp;16, 2010</TD>
</TR>
<!-- End Table Body -->
</TABLE>
</DIV>



<P align="center" style="font-size: 10pt"><!-- Folio --><!-- /Folio -->
</DIV>



</BODY>
</HTML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-1.1
<SEQUENCE>2
<FILENAME>h70209exv1w1.htm
<DESCRIPTION>EX-1.1
<TEXT>
<HTML>
<HEAD>
<TITLE>exv1w1</TITLE>
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<DIV align="right" style="font-size: 10pt; margin-top: 12pt"><B>Exhibit&nbsp;1.1</B>
</DIV>


<DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>87,717,391 Shares</B>
</DIV>


<DIV align="Center" style="font-size: 10pt; margin-top: 6pt"><B>LEXICON PHARMACEUTICALS, INC.</B>
</DIV>

<DIV align="Center" style="font-size: 10pt; margin-top: 6pt"><B>COMMON STOCK, PAR VALUE $0.001 PER SHARE</B>
</DIV>

<DIV align="Center" style="font-size: 10pt; margin-top: 6pt"><B>UNDERWRITING AGREEMENT</B>
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 12pt">March&nbsp;15, 2010
</DIV>


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<DIV align="right" style="font-size: 10pt; margin-top: 12pt">March&nbsp;15, 2010
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">To the Managers named in Schedule&nbsp;I hereto<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for the Underwriters named in Schedule&nbsp;II hereto
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Ladies and Gentlemen:

</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Lexicon Pharmaceuticals, Inc., a Delaware corporation (the &#147;<B>Company</B>&#148;), proposes to issue and
sell to the several underwriters named in Schedule&nbsp;II hereto (the &#147;<B>Underwriters</B>&#148;), for whom you are
acting as managers (the &#147;<B>Managers</B>&#148;), the number of shares of its Common Stock, par value $0.001 per
share set forth in Schedule&nbsp;I hereto (the &#147;<B>Firm Shares</B>&#148;). The Firm Shares includes shares of
Common Stock, par value $0.001 per share set forth in Schedule&nbsp;I hereto that may be offered and
sold by and on behalf of the Underwriters to certain existing stockholders and their affiliated
entities (the &#147;<B>Stockholder Shares</B>&#148;). The Company also proposes to issue and sell to the several
Underwriters not more than the number of additional shares of its Common Stock, par value $0.001
per share set forth in Schedule&nbsp;I hereto (the &#147;<B>Additional Shares</B>&#148;) if and to the extent that you,
as Managers of the offering, shall have determined to exercise, on behalf of the Underwriters, the
right to purchase such shares of common stock granted to the Underwriters in Section&nbsp;2 hereof. The
Firm Shares and the Additional Shares are hereinafter collectively referred to as the &#147;<B>Shares.</B>&#148;
The shares of Common Stock, par value $0.001 per share of the Company to be outstanding after
giving effect to the sales contemplated hereby are hereinafter referred to as the &#147;<B>Common Stock.</B>&#148;
If the firm or firms listed in Schedule&nbsp;II hereto include only the Managers listed in Schedule&nbsp;I
hereto, then the terms &#147;Underwriters&#148; and &#147;Managers&#148; as used herein shall each be deemed to refer
to such firm or firms.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The Company has filed with the Securities and Exchange Commission (the &#147;<B>Commission</B>&#148;) a
registration statement, including a prospectus, (the file number of which is set forth in Schedule
I hereto) on Form S-3, relating to the securities (the &#147;<B>Shelf Securities</B>&#148;), including the Shares,
to be issued from time to time by the Company. The registration statement as amended to the date
of this Agreement, including the information (if any) deemed to be part of the registration
statement at the time of effectiveness pursuant to Rule&nbsp;430A or Rule&nbsp;430B under the Securities Act
of 1933, as amended (the &#147;<B>Securities Act</B>&#148;), is hereinafter referred to as the &#147;<B>Registration
Statement</B>&#148;, and the related prospectus covering the Shelf Securities dated September&nbsp;18, 2009 in
the form first used to confirm sales of the Shares (or in the form first made available to the
Underwriters by the Company to meet requests of purchasers pursuant to Rule&nbsp;173 under the
Securities Act) is hereinafter referred to as the &#147;<B>Basic Prospectus.</B>&#148;
</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">The Basic Prospectus, as supplemented by the prospectus supplement specifically relating to
the Shares in the form first used to confirm sales of the Shares (or in the form first made
available to the Underwriters by the Company to meet requests of purchasers pursuant to Rule&nbsp;173
under the Securities Act) is hereinafter referred to as the &#147;<B>Prospectus</B>,&#148; and the term &#147;<B>preliminary
prospectus</B>&#148; means any preliminary form of the Prospectus. For purposes of this Agreement, &#147;<B>free
writing prospectus</B>&#148; has the meaning set forth in Rule&nbsp;405 under the Securities Act, &#147;<B>Time of Sale
Prospectus</B>&#148; means the preliminary prospectus together with the free writing prospectuses, if any,
each identified in Schedule&nbsp;I hereto, and &#147;<B>broadly available road show</B>&#148; means a &#147;bona fide
electronic road show&#148; as defined in Rule&nbsp;433(h)(5) under the Securities Act that has been made
available without restriction to any person. As used herein, the terms &#147;Registration Statement,&#148;
&#147;Basic Prospectus,&#148; &#147;preliminary prospectus,&#148; &#147;Time of Sale Prospectus&#148; and &#147;Prospectus&#148; shall
include the documents, if any, incorporated by reference therein. The terms &#147;<B>supplement</B>,&#148;
&#147;<B>amendment</B>,&#148; and &#147;<B>amend</B>&#148; as used herein with respect to the Registration Statement, the Basic
Prospectus, the Time of Sale Prospectus, any preliminary prospectus or free writing prospectus
shall include all documents subsequently filed by the Company with the Commission pursuant to the
Securities Exchange Act of 1934, as amended (the &#147;<B>Exchange Act</B>&#148;), that are deemed to be
incorporated by reference therein.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.<I>&nbsp;Representations and Warranties</I>. The Company represents and warrants to and agrees with
each of the Underwriters that:
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(a)&nbsp;The Registration Statement has become effective; no stop order suspending the
effectiveness of the Registration Statement is in effect, and no proceedings for such purpose are
pending before or threatened by the Commission.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b)&nbsp;(i)&nbsp;Each document, if any, filed or to be filed pursuant to the Exchange Act and
incorporated by reference in the Time of Sale Prospectus or the Prospectus complied or will comply
when so filed in all material respects with the Exchange Act and the applicable rules and
regulations of the Commission thereunder, (ii)&nbsp;each part of the Registration Statement, when such
part became effective, did not contain, and each such part, as amended or supplemented, if
applicable, will not contain any untrue statement of a material fact or omit to state a material
fact required to be stated therein or necessary to make the statements therein not misleading,
(iii)&nbsp;the Registration Statement as of the date hereof does not contain any untrue statement of a
material fact or omit to state a material fact required to be stated therein or necessary to make
the statements therein not misleading, the Registration Statement and the Prospectus comply, and as
amended or supplemented, if applicable, will comply in all material respects with the Securities
Act and the applicable rules and regulations of the Commission thereunder, (iv)&nbsp;the Time of Sale
Prospectus does not, and at the time of each sale of the Shares in connection with the offering
when the Prospectus is not yet
</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">available to prospective purchasers and at the Closing Date (as defined in Section&nbsp;4), the
Time of Sale Prospectus, as then amended or supplemented by the Company, if applicable, will not,
contain any untrue statement of a material fact or omit to state a material fact necessary to make
the statements therein, in the light of the circumstances under which they were made, not
misleading and (v)&nbsp;the Prospectus does not contain and, as amended or supplemented, if applicable,
will not contain any untrue statement of a material fact or omit to state a material fact necessary
to make the statements therein, in the light of the circumstances under which they were made, not
misleading, except that the representations and warranties set forth in this paragraph do not apply
to statements or omissions in the Registration Statement, the Time of Sale Prospectus or the
Prospectus based upon information relating to any Underwriter furnished to the Company in writing
by such Underwriter through the Managers expressly for use therein.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(c)&nbsp;The Company is not an &#147;ineligible issuer&#148; in connection with the offering pursuant to
Rules&nbsp;164, 405 and 433 under the Securities Act. Any free writing prospectus that the Company is
required to file pursuant to Rule 433(d) under the Securities Act has been, or will be, filed with
the Commission in accordance with the requirements of the Securities Act and the applicable rules
and regulations of the Commission thereunder. Each free writing prospectus that the Company has
filed, or is required to file, pursuant to Rule 433(d) under the Securities Act or that was
prepared by or behalf of or used or referred to by the Company complies or will comply in all
material respects with the requirements of the Securities Act and the applicable rules and
regulations of the Commission thereunder. Except for the free writing prospectuses, if any,
identified in Schedule&nbsp;I hereto forming part of the Time of Sale Prospectus, and electronic road
shows, if any, each furnished to you before first use, the Company has not prepared, used or
referred to, and will not, without your prior consent, prepare, use or refer to, any free writing
prospectus.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(d)&nbsp;The Company has been duly incorporated, is validly existing as a corporation in good
standing under the laws of the jurisdiction of its incorporation, has the corporate power and
authority to own its property and to conduct its business as described in the Time of Sale
Prospectus and is duly qualified to transact business and is in good standing in each jurisdiction
in which the conduct of its business or its ownership or leasing of property requires such
qualification, except to the extent that the failure to be so qualified or be in good standing
would not have a material adverse effect on the Company and its subsidiaries, taken as a whole (a
&#147;<B>Material Adverse Effect</B>&#148;).
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(e)&nbsp;Each subsidiary of the Company has been duly incorporated, is validly existing as a
corporation in good standing under the laws of the jurisdiction of its incorporation, has the
corporate power and authority to own its property and to conduct its business as described in the
Time of Sale Prospectus and is duly qualified to transact business and is in good standing in each
jurisdiction in which the conduct of its business or its ownership or leasing of
</DIV>

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<DIV align="left" style="font-size: 10pt; margin-top: 6pt">property requires such qualification, except to the extent that the failure to be so qualified
or be in good standing would not have a Material Adverse Effect; all of the issued shares of
capital stock of each subsidiary of the Company have been duly and validly authorized and issued,
are fully paid and non-assessable and are owned directly by the Company, free and clear of all
liens, encumbrances, equities or claims.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(f)&nbsp;This Agreement has been duly authorized, executed and delivered by the Company.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(g)&nbsp;The authorized capital stock of the Company is as set forth in, and conforms as to legal
matters to the description thereof contained in, each of the Time of Sale Prospectus and the
Prospectus.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(h)&nbsp;The shares of Common Stock outstanding prior to the issuance of the Shares have been duly
authorized and are validly issued, fully paid and non-assessable.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(i)&nbsp;The Shares have been duly authorized and, when issued, delivered and paid for in
accordance with the terms of this Agreement, will be validly issued, fully paid and non-assessable,
and the issuance of such Shares will not be subject to any preemptive or similar rights except as
described in the Time of Sale Prospectus.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(j)&nbsp;The execution and delivery by the Company of, and the performance by the Company of its
obligations under, this Agreement will not contravene (i)&nbsp;any provision of applicable law, (ii)&nbsp;the
certificate of incorporation or by-laws of the Company, (iii)&nbsp;any agreement or other instrument
binding upon the Company or any of its subsidiaries that is material to the Company and its
subsidiaries, taken as a whole, or (iv)&nbsp;any judgment, order or decree of any governmental body,
agency or court having jurisdiction over the Company or any subsidiary, except with respect to
clauses (i), (iii)&nbsp;and (iv), for any contraventions that would not, singly or in the aggregate,
have a Material Adverse Effect. No consent, approval, authorization or order of, or qualification
with, any governmental body or agency is required for the performance by the Company of its
obligations under this Agreement, except such (i)&nbsp;as have been obtained under the Securities Act,
(ii)&nbsp;as may be required by the securities or Blue Sky laws of the various states in connection with
the offer and sale of the Shares and (iii)&nbsp;as may be required by the rules and regulations of the
Financial Industry Regulatory Authority (&#147;<B>FINRA</B>&#148;).
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(k)&nbsp;There has not occurred any material adverse change, or any development involving a
prospective material adverse change, in the condition, financial or otherwise, or in the earnings,
business or operations of the Company and its subsidiaries, taken as a whole, from that set forth
in the Time of Sale Prospectus.
</DIV>

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<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(l)&nbsp;There are no legal or governmental proceedings pending or, to the knowledge of the
Company, threatened to which the Company or any of its subsidiaries is a party or to which any of
the properties of the Company or any of its subsidiaries is subject (i)&nbsp;other than proceedings
accurately described in all material respects in the Time of Sale Prospectus and proceedings that
would not reasonably be expected to have a Material Adverse Effect, or on the power or ability of
the Company to perform its obligations under this Agreement or to consummate the transactions
contemplated by the Time of Sale Prospectus or (ii)&nbsp;that are required to be described in the
Registration Statement or the Prospectus and are not so described; and there are no statutes,
regulations, contracts or other documents that are required to be described in the Registration
Statement or the Prospectus or to be filed as exhibits to the Registration Statement that are not
described or filed as required.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(m)&nbsp;Each preliminary prospectus filed as part of the registration statement as originally
filed or as part of any amendment thereto, or filed pursuant to Rule&nbsp;424 under the Securities Act,
complied when so filed in all material respects with the Securities Act and the applicable rules
and regulations of the Commission thereunder, except that the representation and warranty set forth
in this paragraph does not apply to statements or omissions in the preliminary prospectus based
upon information relating to any Underwriter furnished to the Company in writing by such
Underwriter through you expressly for use therein.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(n)&nbsp;The Company is not, and after giving effect to the offering and sale of the Shares and the
application of the proceeds thereof as described in the Prospectus will not be, required to
register as an &#147;investment company&#148; as such term is defined in the Investment Company Act of 1940,
as amended.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(o)&nbsp;The Company and its subsidiaries (i)&nbsp;are in compliance with any and all applicable
foreign, federal, state and local laws and regulations relating to the protection of human health
and safety, the environment or hazardous or toxic substances or wastes, pollutants or contaminants
(&#147;<B>Environmental Laws</B>&#148;), (ii)&nbsp;have received all permits, licenses or other approvals required of
them under applicable Environmental Laws to conduct their respective businesses and (iii)&nbsp;are in
compliance with all terms and conditions of any such permit, license or approval, except where such
noncompliance with Environmental Laws, failure to receive required permits, licenses or other
approvals or failure to comply with the terms and conditions of such permits, licenses or approvals
would not, singly or in the aggregate, have a Material Adverse Effect.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(p)&nbsp;There are no costs or liabilities associated with Environmental Laws (including, without
limitation, any capital or operating expenditures required for clean-up, closure of properties or
compliance with Environmental Laws or any permit, license or approval, any related constraints on
operating activities and any potential liabilities to third parties) which would, singly or in the
aggregate, have a Material Adverse Effect.
</DIV>

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<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(q)&nbsp;Except as described in the Prospectus, there are no contracts, agreements or
understandings between the Company and any person granting such person the right to require the
Company to file a registration statement under the Securities Act with respect to any securities of
the Company or to require the Company to include such securities with the Shares registered
pursuant to the Registration Statement. All of such rights have been waived with respect to the
Registration Statement and the transactions contemplated hereunder.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(r)&nbsp;There are no contracts, other documents or other agreements required to be described in
the Registration Statement or to be filed as exhibits to the Registration Statement by the
Securities Act or by the rules and regulations thereunder which have not been described or filed as
required.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(s)&nbsp;Neither the Company nor any of its subsidiaries, nor any director or officer, nor, to the
Company&#146;s knowledge, any affiliate, employee, agent or representative of the Company or of any of
its subsidiaries or affiliates, has taken or will take any action in furtherance of an offer,
payment, promise to pay, or authorization or approval of the payment or giving of money, property,
gifts or anything else of value, directly or indirectly, to any &#147;government official&#148; (including
any officer or employee of a government or government-owned or controlled entity or of a public
international organization, or any person acting in an official capacity for or on behalf of any of
the foregoing, or any political party or party official or candidate for political office) to
influence official action or secure an improper advantage; and the Company and its subsidiaries and
affiliates have conducted their businesses in compliance with applicable anti-corruption laws and
have instituted and maintain and will continue to maintain policies and procedures designed to
promote and achieve compliance with such laws and with the representation and warranty contained
herein.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(t)&nbsp;The Company has good and marketable title in fee simple to all real property and good and
marketable title to all personal property owned by it which is material to the business of the
Company, in each case free and clear of all liens, encumbrances and defects except such as are
described in the Time of Sale Prospectus or such as do not materially affect the value of such
property and do not interfere in any material respect with the use made and currently proposed to
be made of such property by the Company; and any real property and buildings held under lease by
the Company or of its subsidiaries are held by them under valid, subsisting and enforceable leases
with such exceptions as are not material and do not interfere in any material respect with the use
made and currently proposed to be made of such property and buildings by the Company, in each case
except as described in the Time of Sale Prospectus.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(u)&nbsp;Except as described in the Time of Sale Prospectus, (i)&nbsp;the Company and its subsidiaries
own, possess, or have valid, binding and enforceable licenses or other rights to use the patents,
patent rights and patent applications, copyrights, trademarks, service marks, trade names, Internet
domain
</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">names, technology, confidential information, software, know-how, (including trade secrets and
other unpatented and/or unpatentable proprietary or confidential information, systems or
procedures) and other intellectual property and proprietary rights necessary or used in connection
with the conduct of their business in the manner in which it is presently being conducted and in
the manner set forth in the Time of Sale Prospectus (collectively, the &#147;<B>Company Intellectual
Property</B>&#148;), except as would not reasonably be expected to result in a Material Adverse Effect, and
to the extent that the Company Intellectual Property is not sufficient to so conduct their
business, including with respect to any products described in the Time of Sale Prospectus as being
under development, the Company believes it can acquire such rights on reasonable terms; (ii)&nbsp;to the
knowledge of the Company, (A)&nbsp;none of the patents and patent applications set forth on Appendix&nbsp;A
(collectively, the &#147;<B>Company Patents</B>&#148;) owned by the Company or its subsidiaries is invalid or
unenforceable and neither the Company nor any of its subsidiaries has received any challenge
(including without limitation, notices of expiration) to the validity or enforceability of Company
Patents from any third party or governmental authority and the Company and its subsidiaries have
made all filings and paid all fees necessary to maintain any Company Patents owned by any of them,
and (B)&nbsp;none of the Company Intellectual Property owned by the Company or its subsidiaries is
invalid or unenforceable and neither the Company nor any of its subsidiaries has received any
challenge (including without limitation, notices of expiration) to the validity or enforceability
of Company Intellectual Property from any third party or governmental authority and the Company and
its subsidiaries have made all filings and paid all fees necessary to maintain any Company
Intellectual Property owned by any of them, except as would not reasonably be expected to result in
a Material Adverse Effect for Company Intellectual Property other than Company Patents; (iii)&nbsp;the
Company and its subsidiaries have taken reasonable measures necessary to secure their interests in
Company Intellectual Property, including the confidentiality of all trade secrets and confidential
information which constitutes Company Intellectual Property, and to secure assignment of Company
Intellectual Property from its employees and contractors; (iv)&nbsp;the Company is not aware of any
Company Intellectual Property required to be described in the Time of Sale Prospectus; (v)&nbsp;neither
the Company nor any of its subsidiaries has received any claim of infringement or misappropriation
of (and the Company does not know of any infringement or misappropriation of) intellectual property
rights of others by the Company or any of its subsidiaries (A)&nbsp;with respect to the Company Patents
or (B)&nbsp;with respect to the Company Intellectual Property, except as would not reasonably be
expected to result in a Material Adverse Effect for Company Intellectual Property other than
Company Patents; (vi)&nbsp;the Company and its subsidiaries are not in breach of, and have complied with
all terms of, any license or other agreement relating to any Company Intellectual Property, and no
party to any such agreement has given the Company or its subsidiaries notice of its intention to
cancel, terminate, alter the scope of rights under or fail to renew any such agreement, except as
would not reasonably be expected to result in a
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<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Material Adverse Effect; and (vii)&nbsp;no suit or other proceeding is pending against the Company
or any of its subsidiaries concerning any agreement concerning the Company Intellectual Property,
including any proceeding concerning a claim that the Company or its subsidiaries or another person
has breached any such agreement.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(v)&nbsp;All patent applications owned by the Company and filed with the PTO or any foreign or
international patent authority (the &#147;Company Patent Applications&#148;) have been duly and properly
filed; the Company has complied with its duty of candor and disclosure to the PTO for the Company
Patent Applications; the Company is not aware of any facts required to be disclosed to the PTO that
were not disclosed to the PTO and which would preclude the grant of a patent for the Company Patent
Applications; and the Company has no knowledge of any facts which would preclude it from having
clear title to the Company Patent Applications that have been identified by the Company as being
exclusively owned by the Company.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(w)&nbsp;No material labor dispute with the employees of the Company exists, except as described in
the Time of Sale Prospectus, or, to the knowledge of the Company, is imminent; and the Company is
not aware of any existing, threatened or imminent labor disturbance by the employees of any of its
principal suppliers, manufacturers or contractors that could have a Material Adverse Effect.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(x)&nbsp;The Company is insured by insurers of recognized financial responsibility against such
losses and risks and in such amounts as are prudent and customary in the businesses in which it is
engaged. The Company has no reason to believe that it will not be able to renew its existing
insurance coverage as and when such coverage expires or obtain similar coverage from similar
insurers as may be necessary to continue its business at a cost that would not have a Material
Adverse Effect, except as described in the Time of Sale Prospectus.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(y)&nbsp;The Company possesses all certificates, authorizations and permits issued by the
appropriate federal, state or foreign regulatory authorities necessary to conduct its business as
presently conducted and in the manner set forth in the Time of Sale Prospectus, including without
limitation all such certificates, authorizations and permits required by the United States Food and
Drug Administration (the &#147;<B>FDA</B>&#148;) or any other federal, state or foreign agencies or bodies engaged
in the regulation of pharmaceuticals or biohazardous materials, except as would not reasonably be
expected to result in a Material Adverse Effect, and the Company has not received any notice of
proceedings relating to the revocation or modification of any such certificate, authorization or
permit which, singly or in the aggregate, if the subject of an unfavorable decision, ruling or
finding, would have a Material Adverse Effect, except as described in the Time of Sale Prospectus.
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(z)&nbsp;The studies, tests and preclinical and clinical trials conducted by or on behalf of the
Company that are described in the Registration Statement and the Prospectus were and, if still
pending, are, to the Company&#146;s knowledge, being conducted in all material respects in accordance
with experimental protocols, procedures and controls pursuant to, where applicable, accepted
professional and scientific standards for products or product candidates comparable to those being
developed by the Company; the descriptions of the results of such studies, tests and trials
contained in the Registration Statement and the Prospectus do not contain any misstatement of a
material fact or omit to state a material fact necessary to make such statements not misleading;
the Company has no knowledge of any studies, tests or trials not described in the Registration
Statement and the Prospectus the results of which reasonably call into question in any material
respect the results of the studies, tests and trials described in the Registration Statement or
Prospectus; and the Company has not received any notices or correspondence from the FDA or any
foreign, state or local governmental body exercising comparable authority or any Institutional
Review Board or comparable authority requiring the termination, suspension or material modification
of any studies, tests or preclinical or clinical trials conducted by or on behalf of the Company
which termination, suspension or material modification would reasonably be expected to have a
Material Adverse Effect.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(aa)&nbsp;Except as described in the Time of Sale Prospectus, the Company and its subsidiaries are
in compliance with, and conduct their respective businesses in conformity with, all applicable
federal, state and local laws and regulations, except where the failure to so comply or conform
would not reasonably be expected to have a Material Adverse Effect.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(bb)&nbsp;Ernst &#038; Young LLP, who have certified certain financial statements of the Company and its
subsidiaries, are independent public accountants as required by the Securities Act and the rules
and regulations of the Commission thereunder.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(cc)&nbsp;The Company maintains a system of internal accounting controls sufficient to provide
reasonable assurance that (i)&nbsp;transactions are executed in accordance with management&#146;s general or
specific authorizations; (ii)&nbsp;transactions are recorded as necessary to permit preparation of
financial statements in conformity with generally accepted accounting principles and to maintain
asset accountability; (iii)&nbsp;access to assets is permitted only in accordance with management&#146;s
general or specific authorization; and (iv)&nbsp;the recorded accountability for assets is compared with
the existing assets at reasonable intervals and appropriate action is taken with respect to any
differences. Except as described in the Time of Sale Prospectus, since the end of the Company&#146;s
most recent audited fiscal year, there has been (i)&nbsp;no material weakness in the Company&#146;s internal
control over financial reporting (whether or not remediated) and (ii)&nbsp;no change in the Company&#146;s
internal control over financial reporting that
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">has materially affected, or is reasonably likely to materially affect, the Company&#146;s internal
control over financial reporting.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(dd)&nbsp;Except as described in the Time of Sale Prospectus, the Company has not sold, issued or
distributed any shares of Common Stock during the six-month period preceding the date hereof,
including any sales pursuant to Rule&nbsp;144A under, or Regulation&nbsp;D or S of, the Securities Act, other
than (i)&nbsp;shares of Common Stock issued pursuant to the Underwriting Agreement, dated October&nbsp;8,
2009, between the Company and Morgan Stanley &#038; Co. Incorporated and Thomas Weisel Partners LLC,
(ii)&nbsp;shares of Common Stock issued pursuant to a Purchase Agreement, dated October&nbsp;8, 2009, and
Purchase Agreement Supplement, dated October&nbsp;14, 2009, between the Company and Invus, L.P., a
Bermuda limited partnership (&#147;<B>Invus, L.P.</B>&#148;), and (iii)&nbsp;shares issued pursuant to employee benefit
plans, qualified stock option plans or other employee compensation plans or pursuant to outstanding
options, rights or warrants.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(ee)&nbsp;Each material contract, agreement and license to which the Company is bound is valid,
binding, enforceable, and in full force and effect against the Company, and to the knowledge of the
Company, each other party thereto, except as enforceability may be limited by bankruptcy and other
similar laws affecting the rights of creditors generally and general principles of equity. Neither
the Company nor, to the Company&#146;s knowledge, any other party is in breach or default in any
material respect with respect to any such contract, agreement and license, and, to the Company&#146;s
knowledge, no event has occurred which with notice or lapse of time would constitute a material
breach or default, or permit termination, modification, or acceleration, under any such contract,
agreement or license. To the knowledge of the Company, no party has repudiated any material
provision of any such contract, agreement or license.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(ff)&nbsp;The operations of the Company and its subsidiaries are and have been conducted at all
times in material compliance with all applicable financial recordkeeping and reporting
requirements, including those of the Bank Secrecy Act, as amended by Title III of the Uniting and
Strengthening America by Providing Appropriate Tools Required to Intercept and Obstruct Terrorism
Act of 2001 (USA PATRIOT Act), and the applicable anti-money laundering statutes of jurisdictions
where the Company and its subsidiaries conduct business, the rules and regulations thereunder and
any related or similar rules, regulations or guidelines, issued, administered or enforced by any
governmental agency (collectively, the &#147;<B>Anti-Money Laundering Laws</B>&#148;), and no action, suit or
proceeding by or before any court or governmental agency, authority or body or any arbitrator
involving the Company or any of its subsidiaries with respect to the Anti-Money Laundering Laws is
pending or, to the best knowledge of the Company, threatened.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(gg)&nbsp;(i)&nbsp;The Company represents that neither the Company nor any of its subsidiaries
(collectively, the &#147;<B>Entity</B>&#148;) or , to the knowledge of the Entity, any
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">director, officer, employee, agent, affiliate or representative of the Entity, is an
individual or entity (&#147;<B>Person</B>&#148;) that is, or is owned or controlled by a Person that is:
</DIV>



<DIV align="left" style="font-size: 10pt; margin-top: 6pt; margin-left: 4%">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(A) the subject of any sanctions administered or enforced by the U.S.
Department of Treasury&#146;s Office of Foreign Assets Control (&#147;<B>OFAC</B>&#148;) , the United
Nations Security Council (&#147;<B>UNSC</B>&#148;), the European Union (&#147;<B>EU</B>&#148;), Her Majesty&#146;s
Treasury (&#147;<B>HMT</B>&#148;), or other relevant sanctions authority (collectively,
&#147;<B>Sanctions</B>&#148;), nor
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt; margin-left: 4%">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(B) located, organized or resident in a country or territory that is the
subject of Sanctions (including, without limitation, Burma/Myanmar, Cuba, Iran,
North Korea, Sudan and Syria).
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(ii)&nbsp;The Entity represents and covenants that it will not, directly or indirectly, use the
proceeds of the offering, or lend, contribute or otherwise make available such proceeds to any
subsidiary, joint venture partner or other Person:
</DIV>



<DIV align="left" style="font-size: 10pt; margin-top: 6pt; margin-left: 4%">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(A) to fund or facilitate any activities or business of or with any Person
or in any country or territory that, at the time of such funding or facilitation,
is the subject of Sanctions; or
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt; margin-left: 4%">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(B) in any other manner that will result in a violation of Sanctions by any
Person (including any Person participating in the offering, whether as
underwriter, advisor, investor or otherwise).
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(iii)&nbsp;The Entity represents and covenants that for the past 5&nbsp;years, it has not knowingly
engaged in, is not now knowingly engaged in, and will not engage in, any dealings or transactions
with any Person, or in any country or territory, that at the time of the dealing or transaction is
or was the subject of Sanctions.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(hh)&nbsp;The offer and sale of shares of Common Stock to Invus, L.P. pursuant to the Purchase
Agreement, dated March&nbsp;15, 2010, between the Company and Invus, L.P., will be a valid private
placement within the meaning of Section&nbsp;4(2) of the Securities Act and will not require
registration under the Securities Act.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2.&nbsp;<I>Agreements to Sell and Purchase. </I>The Company hereby agrees to sell to the several
Underwriters, and each Underwriter, upon the basis of the representations and warranties herein
contained, but subject to the conditions hereinafter stated, agrees, severally and not jointly, to
purchase from the Company the respective numbers of Firm Shares set forth in Schedule&nbsp;II hereto
opposite its name at the purchase price set forth in Schedule&nbsp;I hereto (the &#147;<B>Purchase Price</B>&#148;),
provided, that with respect to the Stockholder Shares, the
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">purchase price shall be the price set forth in Schedule&nbsp;I hereto as the &#147;<B>Stockholder Shares
Purchase Price</B>.&#148;
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;On the basis of the representations and warranties contained in this Agreement, and subject to
its terms and conditions, the Company agrees to sell to the Underwriters the Additional Shares, and
the Underwriters shall have the right to purchase, severally and not jointly, up to the number of
Additional Shares set forth in Schedule&nbsp;I hereto at the Purchase Price, provided, however, that the
amount paid by the Underwriters for any Additional Shares shall be reduced by an amount per share
equal to any dividends declared by the Company and payable on the Firm Shares but not payable on
such Additional Shares. You may exercise this right on behalf of the Underwriters in whole or from
time to time in part by giving written notice of each election to exercise the option not later
than 30&nbsp;days after the date of the Prospectus. Any exercise notice shall specify the number of
Additional Shares to be purchased by the Underwriters and the date on which such shares are to be
purchased. Each purchase date must be at least one business day after the written notice is given
and may not be earlier than the closing date for the Firm Shares nor later than ten business days
after the date of such notice. Additional Shares may be purchased as provided in Section&nbsp;4 hereof
solely for the purpose of covering over-allotments made in connection with the offering of the Firm
Shares. On each day, if any, that Additional Shares are to be purchased (an &#147;<B>Option Closing
Date</B>&#148;), each Underwriter agrees, severally and not jointly, to purchase the number of Additional
Shares (subject to such adjustments to eliminate fractional shares as you may determine) that bears
the same proportion to the total number of Additional Shares to be purchased on such Option Closing
Date as the number of Firm Shares set forth in Schedule&nbsp;II hereto opposite the name of such
Underwriter bears to the total number of Firm Shares.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3.<I>&nbsp;Public Offering</I>. The Company is advised by you that the Underwriters propose to make a
public offering of their respective portions of the Shares as soon after the Registration Statement
and this Agreement have become effective as in your judgment is advisable. The Company is further
advised by you that the Shares are to be offered to the public upon the terms set forth in the
Prospectus.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.<I>&nbsp;Payment and Delivery. </I>Payment for the Firm Shares shall be made to the Company by wire
transfer of immediately available funds on the closing date and time set forth in Schedule&nbsp;I
hereto, or at such other time on the same or such other date, not later than the fifth business day
thereafter, as may be designated in writing by you. The time and date of such payment are
hereinafter referred to as the &#147;<B>Closing Date</B>.&#148;
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Payment for any Additional Shares shall be made to the Company in Federal or other funds
immediately available by wire transfer of immediately available funds on the date specified in the
corresponding notice described in Section&nbsp;2 or at such other time on the same or on such other
date, in any event not
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">later than the tenth business day thereafter, as may be designated in writing by you.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The Firm Shares and the Additional Shares shall be registered in such names and in such
denominations as you shall request in writing not later than one full business day prior to the
Closing Date or the applicable Option Closing Date, as the case may be, for the respective accounts
of the several Underwriters, with any transfer taxes payable in connection with the transfer of the
Shares to the Underwriters duly paid, against payment of the Purchase Price or the Stockholder
Shares Purchase Price, as the case may be, therefor.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;5.<I>&nbsp;Conditions to the Underwriters&#146; Obligations</I>. The several obligations of the Underwriters
are subject to the following conditions:
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(a)&nbsp;Subsequent to the execution and delivery of this Agreement and prior to the Closing Date,
there shall not have occurred any change, or any development involving a prospective change, in the
condition, financial or otherwise, or in the earnings, business or operations of the Company and
its subsidiaries, taken as a whole, from that set forth in the Time of Sale Prospectus as of the
date of this Agreement that, in your judgment, is material and adverse and that makes it, in your
judgment, impracticable to market the Shares on the terms and in the manner contemplated in the
Time of Sale Prospectus.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b)&nbsp;The Underwriters shall have received on the Closing Date a certificate, dated the Closing
Date and signed by an executive officer of the Company, to the effect that the representations and
warranties of the Company contained in this Agreement are true and correct as of the Closing Date
and that the Company has complied with all of the agreements and satisfied all of the conditions on
its part to be performed or satisfied hereunder on or before the Closing Date.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The officer signing and delivering such certificate may rely upon the best of his or her
knowledge as to proceedings threatened.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(c)&nbsp;The Underwriters shall have received on the Closing Date an opinion of Vinson &#038; Elkins,
L.L.P., outside counsel for the Company, dated the Closing Date, in form and substance acceptable
to the Underwriters.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(d)&nbsp;The Underwriters shall have received on the Closing Date an opinion of Jeffrey L. Wade,
Executive Vice President and General Counsel of the Company, dated the Closing Date, in form and
substance acceptable to the Underwriters.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(e)&nbsp;The Underwriters shall have received on the Closing Date an opinion of Max Bachrach,
Ph.D., Associate General Counsel, Patents, of the
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Company, dated the Closing Date, in form and substance acceptable to the Underwriters.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(f)&nbsp;The Underwriters shall have received on the Closing Date an opinion of Ropes &#038; Gray LLP,
counsel for the Underwriters, dated the Closing Date, in form and substance acceptable to the
Underwriters.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(g)&nbsp;The Underwriters shall have received, on each of the date hereof and the Closing Date, a
letter dated the date hereof or the Closing Date, as the case may be, in form and substance
satisfactory to the Underwriters, from Ernst &#038; Young LLP, independent public accountants,
containing statements and information of the type ordinarily included in accountants&#146; &#147;comfort
letters&#148; to underwriters with respect to the financial statements and certain financial information
contained in, or incorporated by reference into, the Registration Statement, the Time of Sale
Prospectus and the Prospectus; <I>provided </I>that the letter delivered on the Closing Date shall use a
&#147;cut-off date&#148; not earlier than the date hereof.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(h)&nbsp;At the Closing Date, the Company shall have used its best efforts to list the Shares on
the NASDAQ Global Market.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(i)&nbsp;Payment for 59,296,749 shares of Common Stock offered and sold by the Company to Invus,
L.P., at the price to the public, as described in the Time of Sale Prospectus, shall have been
received by the Company, and such shares shall have been registered in the name of Invus, L.P.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(j)&nbsp;The &#147;lock-up&#148; agreements, each substantially in the form of Exhibit&nbsp;A hereto, between you
and certain shareholders, officers and directors of the Company relating to sales and certain other
dispositions of shares of Common Stock or certain other securities, delivered to you on or before
the date hereof, shall be in full force and effect on the Closing Date.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The several obligations of the Underwriters to purchase Additional Shares hereunder are
subject to the delivery to you on the applicable Option Closing Date of such documents as you may
reasonably request with respect to the good standing of the Company, the due authorization and
issuance of the Additional Shares to be sold on such Option Closing Date and other matters related
to the issuance of such Additional Shares.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;6.<I>&nbsp;Covenants of the Company</I>. The Company covenants with each Underwriter as follows:
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(a)&nbsp;To furnish to you, without charge, a signed copy of the Registration Statement (including
exhibits thereto and documents incorporated by reference therein) and to deliver to each of the
Underwriters during the period mentioned in Section 6(e) or 6(f) below, as many copies of the Time
of Sale
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Prospectus, the Prospectus, any documents incorporated by reference therein and any
supplements and amendments thereto or to the Registration Statement as you may reasonably request.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b)&nbsp;Before amending or supplementing the Registration Statement, the Time of Sale Prospectus
or the Prospectus, to furnish to you a copy of each such proposed amendment or supplement and not
to file any such proposed amendment or supplement to which you reasonably object unless advised in
writing by outside counsel reasonably acceptable to you that the filing of such amendment or
supplement is required by law, and to file with the Commission within the applicable period
specified in Rule 424(b) under the Securities Act any prospectus required to be filed pursuant to
such Rule.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(c)&nbsp;To furnish to you a copy of each proposed free writing prospectus to be prepared by or on
behalf of, used by, or referred to by the Company and not to use or refer to any proposed free
writing prospectus to which you reasonably object.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(d)&nbsp;Not to take, without the prior written consent of the Underwriters, which consent will not
be unreasonably withheld, any action that would result in an Underwriter or the Company being
required to file with the Commission pursuant to Rule 433(d) under the Securities Act a free
writing prospectus prepared by or on behalf of the Underwriter that the Underwriter otherwise would
not have been required to file thereunder.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(e)&nbsp;If the Time of Sale Prospectus is being used to solicit offers to buy the Shares at a time
when the Prospectus is not yet available to prospective purchasers and any event shall occur or
condition exist as a result of which it is necessary to amend or supplement the Time of Sale
Prospectus in order to make the statements therein, in the light of the circumstances, not
misleading, or if any event shall occur or condition exist as a result of which the Time of Sale
Prospectus conflicts with the information contained in the Registration Statement then on file, or
if, in the opinion of counsel for the Underwriters, it is necessary to amend or supplement the Time
of Sale Prospectus to comply with applicable law, forthwith to prepare, file with the Commission
and furnish, at its own expense, to the Underwriters and to any dealer upon request, either
amendments or supplements to the Time of Sale Prospectus so that the statements in the Time of Sale
Prospectus as so amended or supplemented will not, in the light of the circumstances when the Time
of Sale Prospectus is delivered to a prospective purchaser, be misleading or so that the Time of
Sale Prospectus, as amended or supplemented, will no longer conflict with the Registration
Statement, or so that the Time of Sale Prospectus, as amended or supplemented, will comply with
applicable law.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(f)&nbsp;If, during such period after the first date of the public offering of the Shares as in the
opinion of counsel for the Underwriters the Prospectus (or in
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">lieu thereof the notice referred to in Rule 173(a) of the Securities Act) is required by law
to be delivered in connection with sales by an Underwriter or dealer, any event shall occur or
condition exist as a result of which it is necessary to amend or supplement the Prospectus in order
to make the statements therein, in the light of the circumstances when the Prospectus (or in lieu
thereof the notice referred to in Rule 173(a) of the Securities Act) is delivered to a purchaser,
not misleading, or if, in the opinion of counsel for the Underwriters, it is necessary to amend or
supplement the Prospectus to comply with applicable law, forthwith to prepare, file with the
Commission and furnish, at its own expense, to the Underwriters and to the dealers (whose names and
addresses you will furnish to the Company) to which Shares may have been sold by you on behalf of
the Underwriters and to any other dealers upon request, either amendments or supplements to the
Prospectus so that the statements in the Prospectus as so amended or supplemented will not, in the
light of the circumstances when the Prospectus (or in lieu thereof the notice referred to in Rule
173(a) of the Securities Act) is delivered to a purchaser, be misleading or so that the Prospectus,
as amended or supplemented, will comply with applicable law.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(g)&nbsp;To endeavor to qualify the Shares for offer and sale under the securities or Blue Sky laws
of such jurisdictions as you shall reasonably request.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(h)&nbsp;To make generally available to the Company&#146;s security holders and to you as soon as
practicable an earning statement covering a period of at least twelve months beginning with the
first fiscal quarter of the Company occurring after the date of this Agreement which shall satisfy
the provisions of Section 11(a) of the Securities Act and the rules and regulations of the
Commission thereunder.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(i)&nbsp;Whether or not the transactions contemplated in this Agreement are consummated or this
Agreement is terminated, to pay or cause to be paid all expenses incident to the performance of its
obligations under this Agreement, including: (i)&nbsp;the fees, disbursements and expenses of the
Company&#146;s counsel and the Company&#146;s accountants in connection with the registration and delivery of
the Shares under the Securities Act and all other fees or expenses in connection with the
preparation and filing of the Registration Statement, any preliminary prospectus, the Time of Sale
Prospectus, the Prospectus, any free writing prospectus prepared by or on behalf of, used by, or
referred to by the Company and amendments and supplements to any of the foregoing, including the
filing fees payable to the Commission relating to the Shares (within the time required by Rule&nbsp;456
(b)(1), if applicable), all printing costs associated therewith, and the mailing and delivering of
copies thereof to the Underwriters and dealers, in the quantities hereinabove specified, (ii)&nbsp;all
costs and expenses related to the transfer and delivery of the Shares to the Underwriters,
including any transfer or other taxes payable thereon, (iii)&nbsp;the cost of printing or producing any
Blue Sky or Legal Investment memorandum in connection with the offer and sale of the Shares under
state securities laws and all expenses in connection with the
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">qualification of the Shares for offer and sale under state securities laws as provided in
Section 6(g) hereof, including filing fees and the reasonable fees and disbursements of counsel for
the Underwriters in connection with such qualification and in connection with the Blue Sky or Legal
Investment memorandum, (iv)&nbsp;all filing fees and the reasonable fees and disbursements of counsel to
the Underwriters incurred in connection with the review and qualification of the offering of the
Shares by FINRA, all costs and expenses incident to listing the Shares on the NASDAQ Global Market,
(v)&nbsp;the cost of printing certificates representing the Shares, (vi)&nbsp;the costs and charges of any
transfer agent, registrar or depositary, (vii)&nbsp;the costs and expenses of the Company relating to
investor presentations on any &#147;road show&#148; undertaken in connection with the marketing of the
offering of the Shares, including, without limitation, expenses associated with the preparation or
dissemination of any electronic road show, expenses associated with the production of road show
slides and graphics, fees and expenses of any consultants engaged in connection with the road show
presentations with the prior approval of the Company, travel and lodging expenses of the
representatives and officers of the Company and any such consultants, and the cost of any aircraft
chartered in connection with the road show, (viii)&nbsp;the document production charges and expenses
associated with printing this Agreement and (ix)&nbsp;all other costs and expenses incident to the
performance of the obligations of the Company hereunder for which provision is not otherwise made
in this Section. It is understood, however, that except as provided in this Section, Section&nbsp;8
entitled &#147;Indemnity and Contribution&#148; and the last paragraph of Section&nbsp;10 below, the Underwriters
will pay all of their costs and expenses, including fees and disbursements of their counsel, stock
transfer taxes payable on resale of any of the Shares by them and any advertising expenses
connected with any offers they may make.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(j)&nbsp;If the third anniversary of the initial effective date of the Registration Statement
occurs before all the Shares have been sold by the Underwriters, prior to the third anniversary to
file a new shelf registration statement and to take any other action necessary to permit the public
offering of the Shares to continue without interruption; references herein to the Registration
Statement shall include the new registration statement declared effective by the Commission;
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(k)&nbsp;To prepare a final term sheet relating to the offering of the Shares, containing only
information that describes the final terms of the offering in a form consented to by the Managers,
and to file such final term sheet within the period required by Rule&nbsp;433(d)(5)(ii) under the
Securities Act following the date the final terms have been established for the offering of the
Shares.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The Company also covenants with each Underwriter that, without the prior written consent of
each of the Managers identified in Schedule&nbsp;I with the authorization to release this lock-up on
behalf of the Underwriters, it will not, during the restricted period set forth in Schedule&nbsp;I
hereto, (1)&nbsp;offer, pledge, sell,
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">contract to sell, sell any option or contract to purchase, purchase any option or contract to
sell, grant any option, right or warrant to purchase, lend, or otherwise transfer or dispose of,
directly or indirectly, any shares of Common Stock or any securities convertible into or
exercisable or exchangeable for Common Stock or (2)&nbsp;enter into any swap or other arrangement that
transfers to another, in whole or in part, any of the economic consequences of ownership of the
Common Stock, whether any such transaction described in clause (1)&nbsp;or (2)&nbsp;above is to be settled by
delivery of Common Stock or such other securities, in cash or otherwise or (3)&nbsp;file any
registration statement with the Commission relating to the offering of any shares of Common Stock
or any securities convertible into or exercisable or exchangeable for Common Stock. The foregoing
sentence shall not apply to (a)&nbsp;the Shares to be sold hereunder, (b)&nbsp;the shares of Common Stock to
be offered and sold by the Company to Invus, L.P., at the price to the public, as described in the
Time of Sale Prospectus, provided, such offer and sale is not for more than Invus, L.P.&#146;s pro rata
portion of the public offering as described in the Time of Sale Prospectus, (c)&nbsp;the issuance by the
Company of shares of Common Stock upon the exercise of an option or warrant or the conversion of a
security outstanding on the date hereof of which the Underwriters have been advised in writing, (d)
the grant by the Company of options to purchase shares of Common Stock under the Company&#146;s Equity
Incentive Plan as in effect on the date hereof or the Company&#146;s Non-Employee Directors&#146; Stock
Option Plan as in effect on the date hereof, or (e)&nbsp;the establishment of a trading plan pursuant to
Rule&nbsp;10b5-1 under the Exchange Act for the transfer of shares of Common Stock, <I>provided </I>that such
plan does not provide for the transfer of Common Stock during the 90-day restricted period, except
as otherwise permitted herein, and no public announcement or filing under the Exchange Act
regarding the establishment of such plan shall be required of or voluntarily made by or on behalf
of the Company. Notwithstanding the foregoing, if (1)&nbsp;during the last 17&nbsp;days of the 90-day
restricted period the Company issues an earnings release or material news or a material event
relating to the Company occurs; or (2)&nbsp;prior to the expiration of the 90-day restricted period, the
Company announces that it will release earnings results during the 16-day period beginning on the
last day of the 90-day period, the restrictions imposed by this agreement shall continue to apply
until the expiration of the 18-day period beginning on the issuance of the earnings release or the
occurrence of the material news or material event. The Company shall promptly notify the Managers
of any earnings release, news or event that may give rise to an extension of the initial 90-day
restricted period.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;7.<I>&nbsp;Covenants of the Underwriters</I>. Each Underwriter severally covenants with the Company not
to take any action that would result in the Company being required to file with the Commission
under Rule 433(d) a free writing prospectus prepared by or on behalf of such Underwriter that
otherwise would not be required to be filed by the Company thereunder, but for the action of the
Underwriter.
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;8.<I>&nbsp;Indemnity and Contribution. </I>(a)&nbsp;The Company agrees to indemnify and hold harmless each
Underwriter, each person, if any, who controls any Underwriter within the meaning of either
Section&nbsp;15 of the Securities Act or Section&nbsp;20 of the Exchange Act and each affiliate of any
Underwriter within the meaning of Rule&nbsp;405 under the Securities Act from and against any and all
losses, claims, damages and liabilities (including, without limitation, any legal or other expenses
reasonably incurred in connection with defending or investigating any such action or claim) caused
by any untrue statement or alleged untrue statement of a material fact contained in the
Registration Statement or any amendment thereof, any preliminary prospectus, the Time of Sale
Prospectus, any issuer free writing prospectus as defined in Rule 433(h) under the Securities Act,
any Company information that the Company has filed, or is required to file, pursuant to Rule 433(d)
under the Securities Act, or the Prospectus or any amendment or supplement thereto, or caused by
any omission or alleged omission to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading, except insofar as such losses, claims,
damages or liabilities are caused by any such untrue statement or omission or alleged untrue
statement or omission based upon information relating to any Underwriter furnished to the Company
in writing by such Underwriter through you expressly for use therein.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b)&nbsp;Each Underwriter agrees, severally and not jointly, to indemnify and hold harmless the
Company, its directors, its officers who sign the Registration Statement and each person, if any,
who controls the Company within the meaning of either Section&nbsp;15 of the Securities Act or
Section&nbsp;20 of the Exchange Act to the same extent as the foregoing indemnity from the Company to
such Underwriter, but only with reference to information relating to such Underwriter furnished to
the Company in writing by such Underwriter through you expressly for use in the Registration
Statement, any preliminary prospectus, the Time of Sale Prospectus, any issuer free writing
prospectus or the Prospectus or any amendment or supplement thereto.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(c)&nbsp;In case any proceeding (including any governmental investigation) shall be instituted
involving any person in respect of which indemnity may be sought pursuant to Section 8(a) or 8(b),
such person (the &#147;<B>indemnified party</B>&#148;) shall promptly notify the person against whom such indemnity
may be sought (the &#147;<B>indemnifying party</B>&#148;) in writing and the indemnifying party, upon request of the
indemnified party, shall retain counsel reasonably satisfactory to the indemnified party to
represent the indemnified party and any others the indemnifying party may designate in such
proceeding and shall pay the fees and disbursements of such counsel related to such proceeding. In
any such proceeding, any indemnified party shall have the right to retain its own counsel, but the
fees and expenses of such counsel shall be at the expense of such indemnified party unless (i)&nbsp;the
indemnifying party and the indemnified party shall have mutually agreed to the retention of such
counsel or (ii)&nbsp;the named parties to any such proceeding (including any impleaded parties) include
both the indemnifying party and the
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">indemnified party and representation of both parties by the same counsel would be
inappropriate due to actual or potential differing interests between them. It is understood that
the indemnifying party shall not, in respect of the legal expenses of any indemnified party in
connection with any proceeding or related proceedings in the same jurisdiction, be liable for the
fees and expenses of more than one separate firm (in addition to any local counsel) for all such
indemnified parties and that all such fees and expenses shall be reimbursed as they are incurred.
Such firm shall be designated in writing by the Manager authorized to appoint counsel under this
Section set forth in Schedule&nbsp;I hereto, in the case of parties indemnified pursuant to
Section&nbsp;8(a), and by the Company, in the case of parties indemnified pursuant to Section&nbsp;8(b). The
indemnifying party shall not be liable for any settlement of any proceeding effected without its
written consent, but if settled with such consent or if there be a final judgment for the
plaintiff, the indemnifying party agrees to indemnify the indemnified party from and against any
loss or liability by reason of such settlement or judgment. Notwithstanding the foregoing
sentence, if at any time an indemnified party shall have requested an indemnifying party to
reimburse the indemnified party for fees and expenses of counsel as contemplated by the second and
third sentences of this paragraph, the indemnifying party agrees that it shall be liable for any
settlement of any proceeding effected without its written consent if (i)&nbsp;such settlement is entered
into more than 30&nbsp;days after receipt by such indemnifying party of the aforesaid request and (ii)
such indemnifying party shall not have reimbursed the indemnified party in accordance with such
request prior to the date of such settlement. No indemnifying party shall, without the prior
written consent of the indemnified party, effect any settlement of any pending or threatened
proceeding in respect of which any indemnified party is or could have been a party and indemnity
could have been sought hereunder by such indemnified party, unless such settlement includes an
unconditional release of such indemnified party from all liability on claims that are the subject
matter of such proceeding.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(d)&nbsp;To the extent the indemnification provided for in Section 8(a) or 8(b) is unavailable to
an indemnified party or insufficient in respect of any losses, claims, damages or liabilities
referred to therein, then each indemnifying party under such paragraph, in lieu of indemnifying
such indemnified party thereunder, shall contribute to the amount paid or payable by such
indemnified party as a result of such losses, claims, damages or liabilities (i)&nbsp;in such proportion
as is appropriate to reflect the relative benefits received by the Company on the one hand and the
Underwriters on the other hand from the offering of the Shares or (ii)&nbsp;if the allocation provided
by clause 8(d)(i) above is not permitted by applicable law, in such proportion as is appropriate to
reflect not only the relative benefits referred to in clause 8(d)(i) above but also the relative
fault of the Company on the one hand and of the Underwriters on the other hand in connection with
the statements or omissions that resulted in such losses, claims, damages or liabilities, as well
as any other relevant equitable considerations. The relative benefits received by the Company on
the one hand and the Underwriters
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">on the other hand in connection with the offering of the Shares shall be deemed to be in the
same respective proportions as the net proceeds from the offering of the Shares (before deducting
expenses) received by the Company and the total underwriting discounts and commissions received by
the Underwriters bear to the aggregate initial public offering price of the Shares set forth in the
Prospectus. The relative fault of the Company on the one hand and the Underwriters on the other
hand shall be determined by reference to, among other things, whether the untrue or alleged untrue
statement of a material fact or the omission or alleged omission to state a material fact relates
to information supplied by the Company or by the Underwriters and the parties&#146; relative intent,
knowledge, access to information and opportunity to correct or prevent such statement or omission.
The Underwriters&#146; respective obligations to contribute pursuant to this Section&nbsp;8 are several in
proportion to the respective number of Shares they have purchased hereunder, and not joint.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(e)&nbsp;The Company and the Underwriters agree that it would not be just or equitable if
contribution pursuant to this Section&nbsp;8 were determined by <I>pro rata </I>allocation (even if the
Underwriters were treated as one entity for such purpose) or by any other method of allocation that
does not take account of the equitable considerations referred to in Section&nbsp;8(d). The amount paid
or payable by an indemnified party as a result of the losses, claims, damages and liabilities
referred to in Section 8(d) shall be deemed to include, subject to the limitations set forth above,
any legal or other expenses reasonably incurred by such indemnified party in connection with
investigating or defending any such action or claim. Notwithstanding the provisions of this
Section&nbsp;8, no Underwriter shall be required to contribute any amount in excess of the amount by
which the total price at which the Shares underwritten by it and distributed to the public were
offered to the public exceeds the amount of any damages that such Underwriter has otherwise been
required to pay by reason of such untrue or alleged untrue statement or omission or alleged
omission. No person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of
the Securities Act) shall be entitled to contribution from any person who was not guilty of such
fraudulent misrepresentation. The remedies provided for in this Section&nbsp;8 are not exclusive and
shall not limit any rights or remedies which may otherwise be available to any indemnified party at
law or in equity.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(f)&nbsp;The indemnity and contribution provisions contained in this Section&nbsp;8 and the
representations, warranties and other statements of the Company contained in this Agreement shall
remain operative and in full force and effect regardless of (i)&nbsp;any termination of this Agreement,
(ii)&nbsp;any investigation made by or on behalf of any Underwriter, any person controlling any
Underwriter or any affiliate of any Underwriter or by or on behalf of the Company, its officers or
directors or any person controlling the Company and (iii)&nbsp;acceptance of and payment for any of the
Shares.
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;9.<I>&nbsp;Termination</I>. The Underwriters may terminate this Agreement by notice given by you to the
Company, if after the execution and delivery of this Agreement and prior to the Closing Date (i)
trading generally shall have been suspended or materially limited on, or by, as the case may be,
either of the New York Stock Exchange or the NASDAQ Global Market, (ii)&nbsp;trading of any securities
of the Company shall have been suspended on any exchange or in any over-the-counter market, (iii)&nbsp;a
material disruption in securities settlement, payment or clearance services in the United States
shall have occurred, (iv)&nbsp;any moratorium on commercial banking activities shall have been declared
by Federal or New York State authorities or (v)&nbsp;there shall have occurred any outbreak or
escalation of hostilities, or any change in financial markets or any calamity or crisis that, in
your judgment, is material and adverse and which, singly or together with any other event specified
in this clause (v), makes it, in your judgment, impracticable or inadvisable to proceed with the
offer, sale or delivery of the Shares on the terms and in the manner contemplated in the Time of
Sale Prospectus or the Prospectus.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;10.<I>&nbsp;Effectiveness; Defaulting Underwriters</I>. This Agreement shall become effective upon the
execution and delivery hereof by the parties hereto.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If, on the Closing Date or an Option Closing Date, as the case may be, any one or more of the
Underwriters shall fail or refuse to purchase Shares that it has or they have agreed to purchase
hereunder on such date, and the aggregate number of Shares which such defaulting Underwriter or
Underwriters agreed but failed or refused to purchase is not more than one-tenth of the aggregate
number of the Shares to be purchased on such date, the other Underwriters shall be obligated
severally in the proportions that the number of Firm Shares set forth opposite their respective
names in Schedule&nbsp;II bears to the aggregate number of Firm Shares set forth opposite the names of
all such non-defaulting Underwriters, or in such other proportions as you may specify, to purchase
the Shares which such defaulting Underwriter or Underwriters agreed but failed or refused to
purchase on such date; <I>provided </I>that in no event shall the number of Shares that any Underwriter
has agreed to purchase pursuant to this Agreement be increased pursuant to this Section&nbsp;10 by an
amount in excess of one-ninth of such number of Shares without the written consent of such
Underwriter. If, on the Closing Date, any Underwriter or Underwriters shall fail or refuse to
purchase Firm Shares and the aggregate number of Firm Shares with respect to which such default
occurs is more than one-tenth of the aggregate number of Firm Shares to be purchased on such date,
and arrangements satisfactory to you and the Company for the purchase of such Firm Shares are not
made within 36 hours after such default, this Agreement shall terminate without liability on the
part of any non-defaulting Underwriter or the Company. In any such case either you or the Company
shall have the right to postpone the Closing Date, but in no event for longer than seven days, in
order that the required changes, if any, in the Registration Statement, in the Time of Sale
Prospectus, in the Prospectus or in any other documents or arrangements may be effected. If, on an
Option Closing Date, any Underwriter or
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Underwriters shall fail or refuse to purchase Additional Shares and the aggregate number of
Additional Shares with respect to which such default occurs is more than one-tenth of the aggregate
number of Additional Shares to be purchased on such Option Closing Date, the non-defaulting
Underwriters shall have the option to (i)&nbsp;terminate their obligation hereunder to purchase the
Additional Shares to be sold on such Option Closing Date or (ii)&nbsp;purchase not less than the number
of Additional Shares that such non-defaulting Underwriters would have been obligated to purchase in
the absence of such default. Any action taken under this paragraph shall not relieve any
defaulting Underwriter from liability in respect of any default of such Underwriter under this
Agreement.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If this Agreement shall be terminated by the Underwriters, or any of them, because of any
failure or refusal on the part of the Company to comply with the terms or to fulfill any of the
conditions of this Agreement, or if for any reason the Company shall be unable to perform its
obligations under this Agreement, the Company will reimburse the Underwriters or such Underwriters
as have so terminated this Agreement with respect to themselves, severally, for all out-of-pocket
expenses (including the fees and disbursements of their counsel) reasonably incurred by such
Underwriters in connection with this Agreement or the offering contemplated hereunder.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;11.<I>&nbsp;Entire Agreement</I>. (a)&nbsp;This Agreement, together with any contemporaneous written
agreements and any prior written agreements (to the extent not superseded by this Agreement) that
relate to the offering of the Shares, represents the entire agreement between the Company and the
Underwriters with respect to the preparation of any preliminary prospectus, the Time of Sale
Prospectus, the Prospectus, the conduct of the offering, and the purchase and sale of the Shares.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b)&nbsp;The Company acknowledges that in connection with the offering of the Shares: (i)&nbsp;the
Underwriters have acted at arms length, are not agents of, and owe no fiduciary duties to, the
Company or any other person, (ii)&nbsp;the Underwriters owe the Company only those duties and
obligations set forth in this Agreement and prior written agreements (to the extent not superseded
by this Agreement), if any, and (iii)&nbsp;the Underwriters may have interests that differ from those of
the Company. The Company waives to the full extent permitted by applicable law any claims it may
have against the Underwriters arising from an alleged breach of fiduciary duty in connection with
the offering of the Shares.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;12.<I>&nbsp;Counterparts</I>. This Agreement may be signed in two or more counterparts, each of which
shall be an original, with the same effect as if the signatures thereto and hereto were upon the
same instrument.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;13.<I>&nbsp;Applicable Law</I>. This Agreement shall be governed by and construed in accordance with the
internal laws of the State of New York.
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;14.<I>&nbsp;Headings</I>. The headings of the sections of this Agreement have been inserted for
convenience of reference only and shall not be deemed a part of this Agreement.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;15.<I>&nbsp;Notices</I>. All communications hereunder shall be in writing and effective only upon receipt and
if to the Underwriters shall be delivered, mailed or sent to you at the address set forth in
Schedule&nbsp;I hereto; and if to the Company shall be delivered, mailed or sent to the address set
forth in Schedule&nbsp;I hereto.
</DIV>

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</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">

<TABLE width="100%" border="0" cellspacing="0" cellpadding="0" style="font-size: 10pt">
<TR>
    <TD width="48%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="35%">&nbsp;</TD>
    <TD width="15%">&nbsp;</TD>
</TR>
<TR>
    <TD valign="top" align="left">&nbsp;</TD>
    <TD colspan="3" align="left">Very truly yours,<BR>
<BR>
Lexicon Pharmaceuticals, Inc.<BR>
&nbsp;</TD>
    <TD>&nbsp;</TD>
</TR><TR>
    <TD align="left">&nbsp;</TD>
    <TD valign="top">By:&nbsp;&nbsp;</TD>
    <TD colspan="2" style="border-bottom: 1px solid #000000" align="left">/s/ Arthur T. Sands
&nbsp;</TD>
    <TD>&nbsp;</TD>
</TR><TR>
    <TD align="left">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD valign="top">Name:&nbsp;&nbsp;</TD>
    <TD align="left">&nbsp;</TD>
    <TD>&nbsp;</TD>
</TR><TR>
    <TD align="left">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD valign="top">Title:&nbsp;&nbsp;</TD>
    <TD align="left">&nbsp;</TD>
    <TD>&nbsp;</TD>
</TR>
<TR>
    <TD colspan="5">&nbsp;</TD>
</TR>
</TABLE>
<DIV align="center">
<TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
<!-- Begin Table Head -->
<TR valign="bottom">
    <TD width="1%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="37%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="60%">&nbsp;</TD>
</TR>
<!-- End Table Head -->
<!-- Begin Table Body -->
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Accepted as of the date hereof</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Morgan Stanley &#038; Co. Incorporated<br>
J.P. Morgan Securities Inc.</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Acting severally on behalf of themselves<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;and the several Underwriters named<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;in Schedule&nbsp;II hereto.</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">By:
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Morgan Stanley &#038; Co. Incorporated</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">By:
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">/s/ Ashwin A. Pai</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR style="font-size: 1px">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top" style="border-top: 1px solid #000000">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Name: Ashwin A. Pai</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Title: Vice President</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">By:
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">J.P. Morgan Securities Inc.</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">By:
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">/s/ Victoria Aparece</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR style="font-size: 1px">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top" style="border-top: 1px solid #000000">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Name: Victoria Aparece</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Title: Vice President</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<!-- End Table Body -->
</TABLE>
</DIV>


<P align="center" style="font-size: 10pt"><!-- Folio -->&nbsp;<!-- /Folio -->
</DIV>

<!-- PAGEBREAK -->
<P><HR noshade><P>
<H5 align="left" style="page-break-before:always">&nbsp;</H5><P>

<DIV style="font-family: 'Times New Roman',Times,serif">

<DIV align="right" style="font-size: 10pt; margin-top: 12pt"><B>SCHEDULE I</B>
</DIV>

<DIV align="center">
<TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
<!-- Begin Table Head -->
<TR valign="bottom">
    <TD width="1%">&nbsp;</TD>
    <TD width="3%">&nbsp;</TD>
    <TD width="40%">&nbsp;</TD>
    <TD width="3%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="49%">&nbsp;</TD>
</TR>
<!-- End Table Head -->
<!-- Begin Table Body -->
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Managers:</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Managers authorized to release
lock-up under Section&nbsp;6:</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">Morgan Stanley &#038; Co. Incorporated
J.P. Morgan Securities Inc.</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top" nowrap>Manager authorized to appoint
counsel under Section&nbsp;8(c):</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">Morgan Stanley &#038; Co. Incorporated</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Registration Statement File No.:</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">333-161696</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Time of Sale Prospectus</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">1.</TD>
    <TD align="right" valign="top"></TD>
    <TD nowrap valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Prospectus dated September&nbsp;18,
2009 relating to the Shelf Shares</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">2.</TD>
    <TD align="right" valign="top"></TD>
    <TD nowrap valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">the preliminary prospectus
supplement dated March&nbsp;8, 2010
relating to the Shares</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">3.</TD>
    <TD align="right" valign="top"></TD>
    <TD nowrap valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">the issuer free writing
prospectus attached as Exhibit&nbsp;B</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Lock-up Restricted Period:</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">90&nbsp;days</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Title of Shares to be purchased:</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">Common Stock, par value $0.001 per
share</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Number of Firm Shares (including the
Stockholder Shares):</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">87,717,391</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Number of Stockholder Shares:</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">29,021,739</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Number of Additional Shares:</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">8,804,348</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Purchase Price (which shall not apply
to the Stockholder Shares):</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">$1.08675 a share</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Stockholder Shares Purchase Price:</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">$1.15 a share</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Initial Public Offering Price:</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">$1.15 a share</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Selling Concession (which shall not
apply to the Stockholder Shares):</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">$0.03795 a share</TD>
</TR>
<!-- End Table Body -->
</TABLE>
</DIV>


<P align="center" style="font-size: 10pt"><!-- Folio -->I-1<!-- /Folio -->
</DIV>

<!-- PAGEBREAK -->
<P><HR noshade><P>
<H5 align="left" style="page-break-before:always">&nbsp;</H5><P>

<DIV style="font-family: 'Times New Roman',Times,serif">

<DIV align="center">
<TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
<!-- Begin Table Head -->
<TR valign="bottom">
    <TD width="1%">&nbsp;</TD>
    <TD width="3%">&nbsp;</TD>
    <TD width="40%">&nbsp;</TD>
    <TD width="3%">&nbsp;</TD>
    <TD width="0%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="0%">&nbsp;</TD>
    <TD width="3%">&nbsp;</TD>
    <TD width="49%">&nbsp;</TD>
</TR>
<!-- End Table Head -->
<!-- Begin Table Body -->
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Closing Date and Time:</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">March&nbsp;19, 2010 10:00&nbsp;a.m.</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Closing Location:</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">Vinson &#038; Elkins L.L.P.<br>
First City Tower<br>
101 Fannin Street, Suite&nbsp;2500<br>
Houston, Texas 77002-6760</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Address for Notices to Underwriters:</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">Morgan Stanley &#038; Co. Incorporated<br>
J.P. Morgan Securities Inc.<br>
Thomas Weisel Partners LLC<br>
Cowen and Company, LLC<br><br>
c/o Morgan Stanley &#038; Co. Incorporated<br>
1585 Broadway<br>
New York, NY 10036<br><br>
c/o J.P. Morgan Securities Inc.<br>
383 Madison Avenue<br>
New York, NY 10179<br>
Attention: Equity Syndicate<br>
Desk, 4th Floor<br><br>
With a copy to:<br><br>
Ropes &#038; Gray LLP<br>
Attention: Patrick O&#146;Brien<br>
One International Place<br>
Boston, MA 02110</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="right" valign="top">&nbsp;</TD>
    <TD align="right" valign="top">&nbsp;</TD>
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Address for Notices to the Company:</TD>
    <TD>&nbsp;</TD>
    <TD colspan="5" nowrap valign="top" align="left">Lexicon Pharmaceuticals, Inc.<br>
Attention: Jeff Wade<br>
8800 Technology Forest Place<br>
The Woodlands, TX 77381</TD>
</TR>
<!-- End Table Body -->
</TABLE>
</DIV>


<P align="center" style="font-size: 10pt"><!-- Folio -->I-2<!-- /Folio -->
</DIV>

<!-- PAGEBREAK -->
<P><HR noshade><P>
<H5 align="left" style="page-break-before:always">&nbsp;</H5><P>

<DIV style="font-family: 'Times New Roman',Times,serif">

<DIV align="right" style="font-size: 10pt; margin-top: 12pt"><B>SCHEDULE II</B>
</DIV>

<DIV align="center">
<TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
<!-- Begin Table Head -->
<TR valign="bottom">
    <TD width="64%">&nbsp;</TD>
    <TD width="5%">&nbsp;</TD>
    <TD width="3%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="3%">&nbsp;</TD>
    <TD width="5%">&nbsp;</TD>
    <TD width="3%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="3%">&nbsp;</TD>
    <TD width="5%">&nbsp;</TD>
    <TD width="3%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="3%">&nbsp;</TD>
</TR>
<TR style="font-size: 8pt" valign="bottom">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3"><B>Number of</B></TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3">&nbsp;</TD>
</TR>
<TR style="font-size: 8pt" valign="bottom">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3"><B>Firm Shares</B></TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3">&nbsp;</TD>
</TR>
<TR style="font-size: 8pt" valign="bottom">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3"><B>Number of</B></TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3"><B>To Be</B></TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3">&nbsp;</TD>
</TR>
<TR style="font-size: 8pt" valign="bottom">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3"><B>Stockholder</B></TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3"><B>Purchased</B></TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3">&nbsp;</TD>
</TR>
<TR style="font-size: 8pt" valign="bottom">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3"><B>Shares To</B></TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3"><B>(excluding</B></TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3"><B>Total</B></TD>
</TR>
<TR style="font-size: 8pt" valign="bottom">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3"><B>Be</B></TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3"><B>Stockholder</B></TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3"><B>Number of</B></TD>
</TR>
<TR style="font-size: 8pt" valign="bottom">
    <TD nowrap align="left" style="border-bottom: 1px solid #000000">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>Underwriter</B></TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3" style="border-bottom: 1px solid #000000"><B>Purchased</B></TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3" style="border-bottom: 1px solid #000000"><B>Shares)</B></TD>
    <TD>&nbsp;</TD>
    <TD nowrap align="center" colspan="3" style="border-bottom: 1px solid #000000"><B>Firm Shares</B></TD>
</TR>

<!-- End Table Head -->
<!-- Begin Table Body -->
<TR valign="bottom" style="background: #cceeff">
    <TD><DIV style="margin-left:15px; text-indent:-15px">Morgan Stanley &#038; Co. Incorporated</DIV></TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right">13,059,783</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right">26,413,043</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right">39,472,826</TD>
    <TD>&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD><DIV style="margin-left:15px; text-indent:-15px">J.P. Morgan Securities Inc.</DIV></TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right">10,157,609</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right">20,543,478</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right">30,701,087</TD>
    <TD>&nbsp;</TD>
</TR>
<TR valign="bottom" style="background: #cceeff">
    <TD><DIV style="margin-left:15px; text-indent:-15px">Thomas Weisel Partners LLC</DIV></TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right">1,451,087</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right">2,934,783</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right">4,385,870</TD>
    <TD>&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD><DIV style="margin-left:15px; text-indent:-15px">Cowen and Company, LLC</DIV></TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right">4,353,260</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right">8,804,348</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right">13,157,608</TD>
    <TD>&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
</TR>
<TR style="font-size: 1px">
    <TD><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right" style="border-top: 1px solid #000000">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right" style="border-top: 1px solid #000000">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right" style="border-top: 1px solid #000000">&nbsp;</TD>
    <TD>&nbsp;</TD>
</TR>
<TR valign="bottom" style="background: #cceeff">
    <TD><DIV style="margin-left:30px; text-indent:-15px">Total:</DIV></TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right">29,021,739</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right">58,695,652</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right">87,717,391</TD>
    <TD>&nbsp;</TD>
</TR>
<TR style="font-size: 1px">
    <TD><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right" style="border-top: 3px double #000000">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right" style="border-top: 3px double #000000">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="right" style="border-top: 3px double #000000">&nbsp;</TD>
    <TD>&nbsp;</TD>
</TR>
<!-- End Table Body -->
</TABLE>
</DIV>


<P align="center" style="font-size: 10pt"><!-- Folio -->II-1<!-- /Folio -->
</DIV>

<!-- PAGEBREAK -->
<P><HR noshade><P>
<H5 align="left" style="page-break-before:always">&nbsp;</H5><P>

<DIV style="font-family: 'Times New Roman',Times,serif">

<DIV align="right" style="font-size: 10pt; margin-top: 12pt"><B>Exhibit&nbsp;A</B>
</DIV>


<DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>LOCK-UP LETTER</B>
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt; margin-left: 50%">March&nbsp;8, 2010

</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Morgan Stanley &#038; Co. Incorporated<BR>
J.P. Morgan Securities Inc.<BR>
As Managers of the<BR>
several Underwriters listed<BR>
in Schedule&nbsp;II to the Underwriting<BR>
Agreement referred to below

</DIV>

<DIV align="left" style="margin-top: 12pt">
<TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt; background: transparent; color: #000000">
<TR>
    <TD width="3%"></TD>
    <TD width="1%"></TD>
    <TD></TD>
</TR>
<TR valign="top">
    <TD nowrap align="left">c/o</TD>
    <TD>&nbsp;</TD>
    <TD>Morgan Stanley &#038; Co. Incorporated<br>
1585 Broadway<br>
New York, NY 10036</TD>
</TR>
</TABLE>
</DIV>

<DIV align="left" style="margin-top: 12pt">
<TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt; background: transparent; color: #000000">
<TR>
    <TD width="3%"></TD>
    <TD width="1%"></TD>
    <TD></TD>
</TR>
<TR valign="top">
    <TD nowrap align="left">c/o</TD>
    <TD>&nbsp;</TD>
    <TD>J.P. Morgan Securities Inc.<br>
383 Madison Avenue<br>
New York, NY 10179</TD>
</TR>
</TABLE>
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Ladies and Gentlemen:

</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The undersigned understands that Morgan Stanley &#038; Co. Incorporated (&#147;<B>Morgan Stanley</B>&#148;) and J.P.
Morgan Securities Inc. (&#147;<B>J.P. Morgan</B>&#148;) propose to enter into an Underwriting Agreement (the
&#147;<B>Underwriting Agreement</B>&#148;) with Lexicon Pharmaceuticals, Inc., a Delaware corporation (the
&#147;<B>Company</B>&#148;), providing for the public offering (the &#147;<B>Public Offering</B>&#148;) by the several Underwriters,
including Morgan Stanley and J.P. Morgan (the &#147;<B>Underwriters</B>&#148;), of shares (the &#147;<B>Shares</B>&#148;) of the
common stock, par value $0.001 per share, of the Company (the &#147;<B>Common Stock</B>&#148;).
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;To induce the Underwriters that may participate in the Public Offering to continue their
efforts in connection with the Public Offering, the undersigned hereby agrees that, without the
prior written consent of Morgan Stanley and J.P. Morgan on behalf of the Underwriters, it will not,
during the period commencing on the date hereof and ending 90&nbsp;days after the date of the final
prospectus supplement relating to the Public Offering (the &#147;<B>Prospectus</B>&#148;), (1)&nbsp;offer, pledge, sell,
contract to sell, sell any option or contract to purchase, purchase any option or contract to sell,
grant any option, right or warrant to purchase, lend, or otherwise transfer or dispose of, directly
or indirectly, any shares of Common Stock beneficially owned (as such term is used in Rule&nbsp;13d-3 of
the Securities
</DIV>

<P align="center" style="font-size: 10pt"><!-- Folio -->&nbsp;<!-- /Folio -->
</DIV>

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<P><HR noshade><P>
<H5 align="left" style="page-break-before:always">&nbsp;</H5><P>

<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Exchange Act of 1934, as amended (the &#147;<B>Exchange Act</B>&#148;)), by the undersigned or any other
securities so owned convertible into or exercisable or exchangeable for Common Stock or (2)&nbsp;enter
into any swap or other arrangement that transfers to another, in whole or in part, any of the
economic consequences of ownership of the Common Stock, whether any such transaction described in
clause (1)&nbsp;or (2)&nbsp;above is to be settled by delivery of Common Stock or such other securities, in
cash or otherwise. The foregoing sentence shall not apply to (a)&nbsp;transactions relating to shares
of Common Stock or other securities acquired in open market transactions after the completion of
the Public Offering, provided that no filing under Section 16(a) of the Exchange Act, shall be
required or shall be voluntarily made in connection with subsequent sales of Common Stock or other
securities acquired in such open market transactions, (b)&nbsp;any surrender of shares of Common Stock
(or options to purchase shares of Common Stock) to the Company by the undersigned in satisfaction
of (i)&nbsp;any federal, state or local taxes required by law to be withheld with respect to the vesting
of shares of Common Stock or the exercise of stock options to purchase Common Stock and/or (ii)&nbsp;the
exercise price payable to the Company with respect to the exercise of stock options to purchase
Common Stock, in each case granted under a stock incentive plan or stock purchase plan of the
Company described in the Prospectus or any document incorporated by reference therein and in
accordance with the terms of any such instrument as in effect on or before the date hereof, (c)
transfers of shares of Common Stock or any security convertible into Common Stock as a bona fide
gift, (d)&nbsp;distributions of shares of Common Stock or any security convertible into Common Stock to
limited partners or stockholders of the undersigned, (e)&nbsp;transfers to immediate family of the
undersigned, to a trust all of the beneficiaries of which are the undersigned and/or members of his
or her immediate family or to a corporation, partnership, limited partnership or limited liability
company all of the stockholders, partners and members of which are the undersigned and/or members
of his or her immediate family, in each case for estate planning purposes; <I>provided </I>that (i)&nbsp;in the
case of any transfer or distribution pursuant to clause (c) &#151; (e)&nbsp;each donee or distributee shall
sign and deliver a lock-up letter substantially in the form of this letter and (ii)&nbsp;in the case of
any surrender, transfer or distribution pursuant to clause (b) &#151; (e), no filing under Section 16(a)
of the Exchange Act, reporting a reduction in beneficial ownership of shares of Common Stock, shall
be required or shall be voluntarily made during the restricted period referred to in the foregoing
sentence, or (f)&nbsp;the establishment of a trading plan pursuant to Rule&nbsp;10b5-1 under the Exchange Act
for the transfer of shares of Common Stock, <I>provided </I>that such plan does not provide for the
transfer of Common Stock during the restricted period, except as otherwise permitted herein, and no
public announcement or filing under the Exchange Act regarding the establishment of such plan shall
be required of or voluntarily made by or on behalf of the undersigned or the Company. For purposes
of this agreement, &#147;immediate family&#148; shall mean spouse, lineal descendant, father, mother, brother
or sister of the transferor.
</DIV>





<P align="center" style="font-size: 10pt"><!-- Folio -->A-2<!-- /Folio -->
</DIV>

<!-- PAGEBREAK -->
<P><HR noshade><P>
<H5 align="left" style="page-break-before:always">&nbsp;</H5><P>

<DIV style="font-family: 'Times New Roman',Times,serif">




<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In addition, the undersigned agrees that, without the prior written consent of Morgan Stanley
and J.P. Morgan on behalf of the Underwriters, it will not, during the period commencing on the
date hereof and ending 90&nbsp;days after the date of the Prospectus, make any demand for or exercise
any right with respect to, the registration of any shares of Common Stock or any security
convertible into or exercisable or exchangeable for Common Stock. The undersigned also agrees and
consents to the entry of stop transfer instructions with the Company&#146;s transfer agent and registrar
against the transfer of the undersigned&#146;s shares of Common Stock except in compliance with the
foregoing restrictions.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If:
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(1)&nbsp;during the last 17&nbsp;days of the restricted period the Company issues an earnings release or
material news or a material event relating to the Company occurs; or
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(2)&nbsp;prior to the expiration of the restricted period, the Company announces that it will
release earnings results during the 16-day period beginning on the last day of the restricted
period;
</DIV>
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">the restrictions imposed by this agreement shall continue to apply until the expiration of the
18-day period beginning on the issuance of the earnings release or the occurrence of the material
news or material event.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The undersigned shall not engage in any transaction that may be restricted by this agreement
during the 34-day period beginning on the last day of the initial restricted period unless the
undersigned requests and receives prior written confirmation from the Company or Morgan Stanley and
J.P. Morgan that the restrictions imposed by this agreement have expired.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The undersigned understands that the Company and the Underwriters are relying upon this
agreement in proceeding toward consummation of the Public Offering. The undersigned further
understands that this agreement is irrevocable and shall be binding upon the undersigned&#146;s heirs,
legal representatives, successors and assigns.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Notwithstanding the foregoing, this agreement shall terminate and have no further force or
effect if the Public Offering is not consummated by March&nbsp;31, 2010.
</DIV>

<P align="center" style="font-size: 10pt"><!-- Folio -->A-3<!-- /Folio -->
</DIV>

<!-- PAGEBREAK -->
<P><HR noshade><P>
<H5 align="left" style="page-break-before:always">&nbsp;</H5><P>

<DIV style="font-family: 'Times New Roman',Times,serif">

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Whether or not the Public Offering actually occurs depends on a number of factors, including
market conditions. Any Public Offering will only be made pursuant to an Underwriting Agreement,
the terms of which are subject to negotiation between the Company and the Underwriters.
</DIV>
<DIV align="center">
<TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
<!-- Begin Table Head -->
<TR valign="bottom">
    <TD width="45%">&nbsp;</TD>
    <TD width="5%">&nbsp;</TD>
    <TD width="35%">&nbsp;</TD>
    <TD width="5%">&nbsp;</TD>
    <TD width="10%">&nbsp;</TD>
</TR>
<!-- End Table Head -->
<!-- Begin Table Body -->
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Very truly yours,
</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR style="font-size: 1px">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top" style="border-top: 1px solid #000000">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">(Name)</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR style="font-size: 1px">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top" style="border-top: 1px solid #000000">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">(Address)</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<!-- End Table Body -->
</TABLE>
</DIV>


<P align="center" style="font-size: 10pt"><!-- Folio -->A-4<!-- /Folio -->
</DIV>

<!-- PAGEBREAK -->
<P><HR noshade><P>
<H5 align="left" style="page-break-before:always">&nbsp;</H5><P>

<DIV style="font-family: 'Times New Roman',Times,serif">

<DIV align="right" style="font-size: 10pt; margin-top: 12pt"><B>Exhibit&nbsp;B</B>
</DIV>


<DIV align="right" style="font-size: 10pt; margin-top: 12pt">Filed pursuant to Rule&nbsp;433<BR>
Registration No.: 333-161696<BR>
March&nbsp;15, 2010
</DIV>


<DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>Lexicon Pharmaceuticals, Inc.<BR>
$100,875,000<BR>
87,717,391 Shares of Common Stock</B>
</DIV>

<DIV align="center">
<TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
<!-- Begin Table Head -->
<TR valign="bottom">
    <TD width="20%">&nbsp;</TD>
    <TD width="5%">&nbsp;</TD>
    <TD width="75%">&nbsp;</TD>
</TR>
<!-- End Table Head -->
<!-- Begin Table Body -->
<TR valign="bottom">
    <TD><DIV style="margin-left:15px; text-indent:-15px">Issuer:</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Lexicon Pharmaceuticals, Inc.</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD><DIV style="margin-left:15px; text-indent:-15px">Symbol:</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">LXRX</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD><DIV style="margin-left:15px; text-indent:-15px">Size:</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">$100,875,000&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD><DIV style="margin-left:15px; text-indent:-15px">Total Shares Offered:</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">87,717,391 Shares of Common Stock</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD nowrap><DIV style="margin-left:15px; text-indent:-15px">Greenshoe Offered by Issuer:</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">8,804,348 Shares of Common Stock</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD><DIV style="margin-left:15px; text-indent:-15px">Price to Public:</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">$1.15 per share</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD><DIV style="margin-left:15px; text-indent:-15px">Trade Date:</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">March 15, 2010</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD><DIV style="margin-left:15px; text-indent:-15px">Closing Date:</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">March 19, 2010</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD><DIV style="margin-left:15px; text-indent:-15px">CUSIP No:</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">528872104&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD><DIV style="margin-left:15px; text-indent:-15px">Underwriters:</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Morgan Stanley &#038; Co. Incorporated<br></TD>
</TR>
<TR valign="bottom">
    <TD><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">J.P. Morgan Securities Inc.<br></TD>
</TR>
<TR valign="bottom">
    <TD><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Cowen and Company, LLC<br></TD>
</TR>
<TR valign="bottom">
    <TD><DIV style="margin-left:15px; text-indent:-15px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Thomas Weisel Partners LLC</TD>
</TR>
<!-- End Table Body -->
</TABLE>
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 12pt"><B>Invus Participation</B>
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">To maintain its pro rata ownership of the common stock of Lexicon Pharmaceuticals, Inc., Invus,
L.P., the largest shareholder of Lexicon, has agreed to separately purchase in a concurrent private
placement 59,296,749 shares of common stock offered directly from Lexicon at the per share price to
the public set forth above for proceeds to Lexicon of $68,191,261. Additionally, an affiliate of
Invus has agreed to purchase from the underwriters 29,021,739 shares of the 87,717,391 shares of
common stock offered pursuant to this offering at the per share price to the public set forth
above.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">To the extent the underwriters exercise their over-allotment option, Invus will have the right to
purchase up to an aggregate of 5,951,718 additional shares of common stock pursuant to Invus&#146; right
to purchase shares sufficient to maintain its pro rata ownership of Lexicon&#146;s common stock.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Following completion of this offering Invus and its affiliated entities will own approximately
49.3% of the outstanding shares of Lexicon&#146;s common stock, or 48.9% if the underwriters exercise
their over-allotment option in full and Invus exercises its right to purchase additional shares
sufficient to maintain its pro rata ownership of Lexicon&#146;s common stock.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 12pt"><B>Net Proceeds</B>
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Total net proceeds to Lexicon from this offering and the Invus private placement will be
approximately $164,953,761 following the deduction of underwriting discounts and commissions and
estimated expenses payable by Lexicon, or $181,366,361 if the
</DIV>


<P align="center" style="font-size: 10pt"><!-- Folio -->B-1<!-- /Folio -->
</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">underwriters exercise their
over-allotment option in full and Invus exercises its right to purchase additional shares
sufficient to maintain its pro rata ownership of Lexicon&#146;s common stock.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 12pt"><B>Dilution</B>
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">New investors purchasing shares of common stock in this offering will experience immediate dilution
in net tangible book value of $0.21 per share.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 12pt"><B>Supplements to Agreements with Invus</B>
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">In connection with this offering and the concurrent private placement, Lexicon entered into an
agreement with Invus and its affiliate supplementing the terms of the transaction agreements
between Lexicon and Invus, including the securities purchase and stockholders&#146; agreements with
Invus, dated June&nbsp;17, 2007, in the case of the securities purchase agreement, as previously
amended.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">The supplement to these transaction agreements:
</DIV>


<DIV style="margin-top: 6pt">
<TABLE width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 10pt">

<TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
    <TD width="2%" style="background: transparent">&nbsp;</TD>
    <TD width="3%" nowrap align="left"><B>&#149;</B></TD>
    <TD width="1%">&nbsp;</TD>
    <TD>Extends the period during which Invus may exercise its right to require Lexicon to
conduct the first rights offering under the securities purchase agreement from one year
beginning on November&nbsp;28, 2009 to fifteen months following November&nbsp;28, 2009.</TD>
</TR>

<TR>
    <TD style="font-size: 6pt">&nbsp;</TD>
</TR><TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
    <TD width="2%" style="background: transparent">&nbsp;</TD>
    <TD width="3%" nowrap align="left"><B>&#149;</B></TD>
    <TD width="1%">&nbsp;</TD>
    <TD>Provides that the 29,021,739 shares of common stock purchased from the underwriters in
this offering by Invus and its affiliates will not be restricted shares under the
stockholders&#146; agreement. As a result, the shares will not be subject to the voting
restrictions in the stockholders agreement and will be included in determining whether
Invus exceeds the 50% ownership threshold with respect to our common stock under the
stockholders agreement, thereby terminating certain rights thereunder.</TD>
</TR>

<TR>
    <TD style="font-size: 6pt">&nbsp;</TD>
</TR><TR valign="top" style="font-size: 10pt; color: #000000; background: transparent">
    <TD width="2%" style="background: transparent">&nbsp;</TD>
    <TD width="3%" nowrap align="left"><B>&#149;</B></TD>
    <TD width="1%">&nbsp;</TD>
    <TD>Reduces the maximum amount of the first and second rights offerings under the securities
purchase agreement by the net proceeds to Lexicon from this offering and the concurrent
private placement, or by approximately $165.0&nbsp;million. Pursuant to the securities purchase
agreement prior to giving effect to the supplement, Invus had the right to require Lexicon
to initiate the first rights offering to all of Lexicon&#146;s stockholders in an aggregate
amount to be designated by Invus not to exceed approximately $172.3&nbsp;million. As a result,
after giving effect to the supplement, the maximum amount subject to the first rights
offering will not exceed approximately $7.3&nbsp;million.</TD>
</TR>

</TABLE>
</DIV>

<DIV align="center" style="font-size: 10pt; margin-top: 18pt">* * * * *
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">The issuer has filed a registration statement (including a prospectus) with the SEC for the
offering to which this communication relates. Before you invest, you should read the prospectus in
that registration statement and other documents the issuer has filed with the SEC for more complete
information about the issuer and this offering. You may get these documents for free by visiting
EDGAR on the SEC Web site at <U>www.sec.gov</U>. Alternatively, the issuer, any underwriter or any
dealer participating in the offering will arrange to send you the prospectus if you request it by
calling toll-free 1-(866) 718-1649, or by emailing <U>prospectus@morganstanley.com</U>.
</DIV>


<P align="center" style="font-size: 10pt"><!-- Folio -->B-2<!-- /Folio -->
</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">




<DIV align="right" style="font-size: 10pt; margin-top: 12pt"><B>Appendix&nbsp;A</B>
</DIV>


<DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>COMPANY PATENTS</B>
</DIV>



<P align="center" style="font-size: 10pt"><!-- Folio -->A-1<!-- /Folio -->
</DIV>



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</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-5.1
<SEQUENCE>3
<FILENAME>h70209exv5w1.htm
<DESCRIPTION>EX-5.1
<TEXT>
<HTML>
<HEAD>
<TITLE>exv5w1</TITLE>
</HEAD>
<BODY bgcolor="#FFFFFF">
<!-- PAGEBREAK -->
<DIV style="font-family: 'Times New Roman',Times,serif">


<DIV align="right" style="font-size: 10pt; margin-top: 12pt"><B>Exhibit&nbsp;5.1</B>
</DIV>


<DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>&#091;Vinson &#038; Elkins L.L.P. Letterhead&#093;</B>
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">March&nbsp;15, 2010
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Lexicon Pharmaceuticals, Inc.<BR>
8800 Technology Forest Place<BR>
The Woodlands, Texas 77381

</DIV>
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Ladies and Gentlemen:
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We have acted as counsel for Lexicon Pharmaceuticals, Inc., a Delaware corporation (the
&#147;Company&#148;), in connection with the preparation of the prospectus dated September&nbsp;18, 2009 (the
&#147;Prospectus&#148;) and the prospectus supplement dated March&nbsp;15, 2010 (the &#147;Prospectus Supplement&#148;) with
respect to the Registration Statement on Form S-3 (Registration No.&nbsp;333-161696) (the &#147;Registration
Statement&#148;) filed by the Company with the Securities and Exchange Commission (the &#147;Commission&#148;)
under the Securities Act of 1933, as amended (the &#147;Securities Act&#148;), relating to the issuance and
sale of up to 96,521,739 shares of the Company&#146;s common stock, par value $0.001 per share (the
&#147;Shares&#148;). The Shares are being offered, issued and sold pursuant to an Underwriting Agreement,
dated March&nbsp;15, 2010, by and among the Company and the several underwriters named therein (the
&#147;Underwriting Agreement&#148;).
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In our capacity as your counsel for the matter referred to above, we have examined (i)&nbsp;the
Registration Statement; (ii)&nbsp;the Prospectus; (iii)&nbsp;the Prospectus Supplement; (iv)&nbsp;the Company&#146;s
Restated Certificate of Incorporation, dated April&nbsp;5, 2000, as amended to the date hereof; (v)&nbsp;the
Underwriting Agreement; (vi)&nbsp;resolutions of the Board of Directors of the Company dated March&nbsp;3,
2010 and the pricing committee thereof dated March&nbsp;15, 2010; and (vii)&nbsp;such statutes, including the
Delaware General Corporation Law, corporate records, documents, certificates of public officials
and other instruments and documents as we deemed necessary or advisable for purposes of this
opinion. In giving such opinions, we have relied upon certificates of officers of the Company with
respect to the accuracy of the material factual matters contained in such certificates. In making
our examination, we have assumed the authenticity of all documents submitted to us as originals and
the conformity with the original documents of all documents submitted to us as copies.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In connection with this opinion, we have assumed that the Shares will be issued and sold in
the manner set forth in the Prospectus Supplement and the Underwriting Agreement.
</DIV>

<P align="center" style="font-size: 10pt"><!-- Folio -->&nbsp;<!-- /Folio -->
</DIV>

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<P><HR noshade><P>
<H5 align="left" style="page-break-before:always">&nbsp;</H5><P>

<DIV style="font-family: 'Times New Roman',Times,serif">

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;On the basis of the foregoing, and subject to the assumptions, limitations and qualifications
set forth herein, we are of the opinion that the Shares, when issued and delivered in accordance
with the terms of the Underwriting Agreement, will be validly issued, fully paid and
non-assessable.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The opinions expressed herein are limited in all respects to the federal laws of the United
States, Constitution of the State of Delaware and the Delaware General Corporation Law, as
interpreted by the courts of the State of Delaware and the United States, and we are expressing no
opinion as to the effect of the laws of any other jurisdiction, domestic or foreign.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We hereby consent to references to this firm under the caption &#147;Legal Matters&#148; in the
Prospectus Supplement and to the filing of this opinion as an exhibit to a Current Report on
Form 8-K of the Company. In giving this consent, we do not admit that we are within the category
of persons whose consent is required under Section&nbsp;7 of the Securities Act and the rules and
regulations thereunder.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt; margin-left: 50%">Very truly yours,

</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt; margin-left: 50%">/s/ Vinson &#038; Elkins L.L.P.

</DIV>


<P align="center" style="font-size: 10pt"><!-- Folio -->&nbsp;<!-- /Folio -->
</DIV>




</BODY>
</HTML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-10.1
<SEQUENCE>4
<FILENAME>h70209exv10w1.htm
<DESCRIPTION>EX-10.1
<TEXT>
<HTML>
<HEAD>
<TITLE>exv10w1</TITLE>
</HEAD>
<BODY bgcolor="#FFFFFF">
<!-- PAGEBREAK -->
<DIV style="font-family: 'Times New Roman',Times,serif">


<DIV align="right" style="font-size: 10pt; margin-top: 12pt"><B>Exhibit&nbsp;10.1</B>
</DIV>


<DIV align="center" style="font-size: 10pt; margin-top: 18pt"><U><B>PURCHASE AGREEMENT</B></U>
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">March&nbsp;15, 2010
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Invus, L.P.<BR>
c/o The Invus Group, LLC<BR>
750 Lexington Avenue (30<SUP style="font-size: 85%; vertical-align: text-top">th</SUP> Floor)<BR>
New York, New York 10022

</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Lexicon Pharmaceuticals, Inc.<BR>
8800 Technology Forest Place<BR>
The Woodlands, Texas 77381<BR>
Attn: President and Chief Executive Officer

</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 12pt">Ladies and Gentlemen:
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Reference is made to (a)&nbsp;the Stockholders&#146; Agreement, dated as of June&nbsp;17, 2007 (as amended,
supplemented or otherwise modified, the &#147;<U>Stockholders&#146; Agreement</U>&#148;), by and between Invus,
L.P. (the &#147;<U>Investor</U>&#148;) and Lexicon Pharmaceuticals, Inc. (the &#147;<U>Company</U>&#148;), (b)&nbsp;the
Supplement to Transaction Agreements, dated as of March&nbsp;15, 2010 (the &#147;<U>Supplement</U>&#148;),
amending and/or supplementing the Stockholders&#146; Agreement, the Securities Purchase Agreement, dated
as of June&nbsp;17, 2007, by and between the Investor and the Company (as amended, supplemented or
otherwise modified, the &#147;<U>Securities Purchase Agreement</U>&#148;) and the Registration Rights
Agreement, dated as of June&nbsp;17, 2007, by and between the Investor and the Company, and (c)&nbsp;that
certain Underwriting Agreement being entered into by the Company with the representatives of the
underwriters concurrently with this Purchase Agreement (the &#147;<U>Underwriting Agreement</U>&#148;)
providing for the issuance by the Company to the underwriters of 87,717,391 shares of Company
Common Stock (the &#147;<U>Firm Shares</U>&#148;), without giving effect to any exercise of the
underwriters&#146; over-allotment option, for sale in a public offering at a price to the public of
$1.15 per share (the &#147;<U>Price to Public</U>&#148;). Capitalized terms used but not otherwise defined
herein shall have the meanings ascribed to them in the Stockholders&#146; Agreement.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Pursuant to Section&nbsp;4.02 of the Stockholders&#146; Agreement and Section&nbsp;5 of the Supplement, on
the terms and subject to the conditions set forth herein, the Investor hereby agrees to purchase
from the Company the number of shares specified below (collectively, the &#147;<U>Invus Shares</U>&#148;) of
Company Common Stock at a price per share equal to the Price to Public, for the total purchase
price specified below:
</DIV>
<DIV align="center">
<TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
<!-- Begin Table Head -->
<TR valign="bottom">
    <TD width="7%">&nbsp;</TD>
    <TD width="5%">&nbsp;</TD>
    <TD width="3%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="83%">&nbsp;</TD>
</TR>
<!-- End Table Head -->
<!-- Begin Table Body -->
<TR valign="bottom">
    <TD nowrap><DIV style="margin-left:15px; text-indent:-15px">Number of shares to be purchased by the Investor:&nbsp;&nbsp;</DIV></TD>

    <TD colspan="5" align="left">59,296,749 shares of Company Common Stock</TD>

</TR>

<tr>
    <TD>&nbsp;</TD>
</TR>

<TR valign="bottom">
    <TD><DIV style="margin-left:15px; text-indent:-15px">Total Purchase Price:</DIV></TD>
    <TD colspan="5" align="left">$ 68,191,261.35</TD>

</TR>
<!-- End Table Body -->
</TABLE>
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The Company hereby represents and warrants to and agrees with the Investor to all the same
representations and warranties contained in Section&nbsp;1 and the covenants contained in
</DIV>

<P align="center" style="font-size: 10pt"><!-- Folio -->&nbsp;<!-- /Folio -->
</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Section&nbsp;6 (other than the last paragraph thereof) of the Underwriting Agreement mutatis mutandis to
the same extent as if such representations and warranties and covenants were set forth herein for
the benefit of the Investor instead of the underwriters party to the Underwriting Agreement (except
that references to the Underwriting Agreement therein shall be references to this Agreement and
references to the Shares thereunder shall be references to the Invus Shares). The obligation of the
Investor to purchase the Invus Shares from the Company, and of the Company to sell the Invus Shares
to the Investor, will be subject to (i)&nbsp;the satisfaction of the conditions set forth in Section&nbsp;5
of the Underwriting Agreement (other than clauses (i)&nbsp;and (j)&nbsp;thereunder) and the concurrent
closing of the sale of the Firm Shares under the terms set forth in the Underwriting Agreement,
(ii)&nbsp;the delivery to the Investor of opinions of counsel to the Company by the same counsel as set
forth in Sections&nbsp;5(c), (d)&nbsp;and (e)&nbsp;of the Underwriting Agreement in the form and substance
acceptable to the Investor and (iii)&nbsp;the delivery to the Investor of the officer&#146;s certificate
contemplated by Section 5(b) of the Underwriting Agreement, and such obligations shall terminate in
the event the Underwriting Agreement is terminated. The Company shall use its best efforts to
cause the Invus Shares to be listed on the NASDAQ Global Market.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The Investor hereby represents and warrants to the Company that the Investor (i)&nbsp;is acquiring
the Invus Shares for its own account solely for the purpose of investment and not with a view to,
or for resale in connection with, any distribution of such Invus Shares or any interest therein,
(ii)&nbsp;is an &#147;accredited investor&#148; as defined in Rule&nbsp;501 of Regulation&nbsp;D promulgated under the
Securities Act, a sophisticated investor and, by virtue of its business or financial experience, is
capable of evaluating the merits and risks of the investment in the Invus Shares and (iii)&nbsp;has been
provided an opportunity to ask questions of and receive answers from representatives of the Company
concerning the terms and conditions of this Agreement and the purchase of the Invus Shares
contemplated hereby.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The closing of the sale of the Invus Shares shall take place concurrently with the closing of
the sale of the Firm Shares under the Underwriting Agreement, (i)&nbsp;with payment for the Invus Shares
to be made to the Company by wire transfer of immediately available funds on the closing date and
(ii)&nbsp;with delivery of the Invus Shares registered, as applicable, in the name of the Investor or
its respective designees and free and clear of all liens (other than those under applicable law,
the Stockholders Agreement and the &#147;lock-up&#148; agreement entered into between the Investor and the
underwriters party to the Underwriting Agreement), with any transfer or stamp taxes duly paid, to
the Investor.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This Agreement shall be deemed to satisfy the Company&#146;s obligations under the Stockholders&#146;
Agreement with respect to the delivery of a Notice of Issuance with respect to the Firm Shares and
shall constitute the Investor&#146;s notice of exercise pursuant to Section&nbsp;5(a)(i) of the Supplement.
</DIV>

<P align="center" style="font-size: 10pt"><!-- Folio -->&nbsp;<!-- /Folio -->
</DIV>

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<H5 align="left" style="page-break-before:always">&nbsp;</H5><P>

<DIV style="font-family: 'Times New Roman',Times,serif">

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This Agreement shall automatically terminate upon any termination of the Underwriting
Agreement. The provisions of Sections&nbsp;9.03 and 9.04 and Article&nbsp;X of the Securities Purchase
Agreement are incorporated herein by reference and shall apply to this Agreement mutatis mutandis.
</DIV>

<DIV align="center" style="font-size: 10pt; margin-top: 18pt"><I>&#091;Signature Page Follows&#093;</I>
</DIV>







<P align="center" style="font-size: 10pt"><!-- Folio -->&nbsp;<!-- /Folio -->
</DIV>

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<P><HR noshade><P>
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<DIV style="font-family: 'Times New Roman',Times,serif">



<DIV align="center">
<TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
<!-- Begin Table Head -->
<TR valign="bottom">
    <TD width="40%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="35%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="14%">&nbsp;</TD>
</TR>
<!-- End Table Head -->
<!-- Begin Table Body -->
<TR valign="bottom">
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD colspan="3" valign="top" align="left">Sincerely,</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD colspan="3" valign="top" align="left">INVUS, L.P.,</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD colspan="3" valign="top" align="left">a Bermuda limited partnership</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD colspan="3" valign="top" align="left">By: Invus Advisors, L.L.C., its general partner</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">By:<BR>
Name:
</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">/s/ Raymond Debbane
<DIV style="font-size: 1pt; border-top: 1px solid #000000">&nbsp;</DIV>
Raymond Debbane
</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">Title:
</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">President</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
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<DIV align="center">
<TABLE style="font-size: 10pt" cellspacing="0" border="0" cellpadding="0" width="100%">
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<TR valign="bottom">
    <TD width="1%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="35%">&nbsp;</TD>
    <TD width="1%">&nbsp;</TD>
    <TD width="60%">&nbsp;</TD>
</TR>
<!-- End Table Head -->
<!-- Begin Table Body -->
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">Accepted and agreed to:</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">LEXICON PHARMACEUTICALS, INC.,</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD colspan="3" valign="top" align="left">a Delaware corporation</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom"><!-- Blank Space -->
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">&nbsp;</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">By: <BR>
Name:
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">/s/ Arthur T. Sands
<DIV style="font-size: 1pt; border-top: 1px solid #000000">&nbsp;</DIV>
Arthur T. Sands, M.D., Ph.D.
</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<TR valign="bottom">
    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">Title:
</DIV></TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">President and Chief Executive Officer</TD>
    <TD>&nbsp;</TD>
    <TD align="left" valign="top">&nbsp;</TD>
</TR>
<!-- End Table Body -->
</TABLE>
</DIV>


<DIV align="center" style="font-size: 10pt; margin-top: 18pt"><I>&#091;Signature Page to Purchase Agreement&#093;</I>
</DIV>



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<SEQUENCE>5
<FILENAME>h70209exv99w1.htm
<DESCRIPTION>EX-99.1
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<DIV style="font-family: 'Times New Roman',Times,serif">


<DIV align="right" style="font-size: 10pt; margin-top: 12pt"><B>Exhibit&nbsp;99.1</B>
</DIV>


<DIV align="center" style="font-size: 10pt; margin-top: 18pt"><B>LEXICON ANNOUNCES PRICING OF COMMON STOCK<BR>
IN PUBLIC OFFERING</B>
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt"><B>The Woodlands, Texas, March&nbsp;16, 2010 </B>&#151; Lexicon Pharmaceuticals, Inc. (Nasdaq: LXRX) today
announced the pricing of a public offering and concurrent private placement of its common stock in
which the aggregate net proceeds to Lexicon will be approximately $165.0&nbsp;million. The public
offering consists of 87,717,391 shares of its common stock at a public offering price of $1.15 per
share. In connection with the public offering, Lexicon agreed to sell an additional 59,296,749
shares of its common stock at the public offering price to Invus, L.P., Lexicon&#146;s largest
stockholder, in a concurrent private placement upon Invus&#146; exercise of its right to purchase shares
sufficient to maintain its pro rata ownership of Lexicon&#146;s common stock.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">All of the shares subject to the public offering are being offered by Lexicon pursuant to an
effective shelf registration statement previously filed with the Securities and Exchange
Commission. Lexicon has also granted the underwriters a 30-day option to purchase up to an
aggregate of 8,804,348 additional shares of common stock to cover over-allotments, if any. To the
extent the underwriters exercise their over-allotment option, Invus may purchase up to an aggregate
of 5,951,718 additional shares of common stock in a private placement pursuant to its right to
purchase shares sufficient to maintain its pro rata ownership of Lexicon&#146;s common stock. Morgan
Stanley &#038; Co. Incorporated and J.P. Morgan Securities Inc. are acting as joint book-runners for the
public offering, with Cowen and Company, LLC and Thomas Weisel Partners LLC acting as co-managers.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">This press release does not constitute an offer to sell, or the solicitation of an offer to buy,
these securities, nor will there be any sale of these securities in any state or jurisdiction in
which such offer, solicitation or sale is not permitted. The offering of the securities in the
public offering will be made only by means of a final prospectus supplement and accompanying
prospectus, copies of which may be obtained from Morgan Stanley &#038; Co. Incorporated, Attn:
Prospectus Department, 180 Varick Street, 2nd Floor, New York, New York 10014, telephone: (866)
718-1649, or by emailing <U>prospectus@morganstanley.com</U>, or from J.P. Morgan Securities, Inc.,
Attention: Broadridge Financial Solutions at 1155 Long Island Avenue, Edgewood, New York 11717, or
by telephone at (866)&nbsp;803-9204.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">The issuer has filed a registration statement (including a base prospectus) with the Securities and
Exchange Commission, or SEC, for an offering to which this communication relates. Before you
invest, you should read the prospectus in that registration statement and related prospectus
supplements and other documents that the issuer has filed or will file with the SEC for more
complete information about the issuer and this offering. You may get these documents for free by
visiting EDGAR on the SEC website at <U>www.sec.gov</U>. Alternatively, you may obtain a final prospectus
supplement and accompanying prospectus as indicated above.
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt">The shares to be sold to Invus in the private placement have not been, and will not be, registered
under the Securities Act of 1933, as amended, or any state securities laws and may not be offered
or sold in the United States absent registration or applicable exemption from the registration
requirement of such Act and applicable state securities laws.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt"><B>About Lexicon</B><BR>
Lexicon is a biopharmaceutical company focused on discovering breakthrough treatments for human
disease. Lexicon currently has four drug candidates in mid-stage development for

</DIV>

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<DIV style="font-family: 'Times New Roman',Times,serif">
<DIV align="left" style="font-size: 10pt; margin-top: 6pt">diabetes, irritable bowel syndrome, carcinoid syndrome, and rheumatoid arthritis, all of which were
discovered by the company&#146;s research team.
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 12pt"><B>Safe Harbor Statement</B>
</DIV>

<DIV align="left" style="font-size: 10pt; margin-top: 6pt"><I>This press release contains &#147;forward-looking&#148; statements, including statements related to Lexicon&#146;s
expectations regarding the completion, timing and size of the public offering and concurrent
private placement. Any statements contained in this press release that are not statements of
historical fact may be deemed to be forward-looking statements. Words such as &#147;anticipated,&#148;
&#147;will,&#148; &#147;proposed,&#148; and similar expressions are intended to identify these forward-looking
statements. There are a number of important factors that could cause Lexicon&#146;s results to differ
materially from those indicated by these forward-looking statements, including risks and
uncertainties related to market conditions and the satisfaction of customary closing conditions
related to the public offering and concurrent private placement. There can be no assurance that
Lexicon will be able to complete the public offering or concurrent private placement on the
anticipated terms, or at all. Additional risks and uncertainties relating to the public offering
and concurrent private placement, Lexicon and its business can be found under the headings &#147;Factors
Affecting Forward-Looking Statements&#148; and &#147;Risk Factors&#148; in Lexicon&#146;s annual report on Form&nbsp;10-K
for the year ended December&nbsp;31, 2009, as filed with the Securities and Exchange Commission and
under the heading &#147;Risk Factors&#148; in the final prospectus supplement related to the public offering
to be filed with the Securities and Exchange Commission. Unless required by applicable law,
Lexicon undertakes no obligation to update or revise any such forward-looking statements, whether
as a result of new information, future events or otherwise.</I>
</DIV>


<DIV align="center" style="font-size: 10pt; margin-top: 18pt"><I># # #</I>
</DIV>


<DIV align="left" style="font-size: 10pt; margin-top: 6pt"><B>Contact for Lexicon:</B><BR>
D. Wade Walke<BR>
Senior Director, Corporate Communications<BR>
281/863-3046<BR>
<u>wwalke@lexpharma.com</u>

</DIV>


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