-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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<SEC-DOCUMENT>0000898432-09-000704.txt : 20090522
<SEC-HEADER>0000898432-09-000704.hdr.sgml : 20090522
<ACCEPTANCE-DATETIME>20090520165355
ACCESSION NUMBER:		0000898432-09-000704
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20090515
FILED AS OF DATE:		20090520
DATE AS OF CHANGE:		20090520

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			LAMPERT MARK N
		CENTRAL INDEX KEY:			0001233840

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-14656
		FILM NUMBER:		09843142

	MAIL ADDRESS:	
		STREET 1:		2415 GREEN ST
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94123

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			REPLIGEN CORP
		CENTRAL INDEX KEY:			0000730272
		STANDARD INDUSTRIAL CLASSIFICATION:	BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
		IRS NUMBER:				042729386
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0331

	BUSINESS ADDRESS:	
		STREET 1:		41 SEYON STREET
		STREET 2:		BUILDING 1, SUITE 100
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02453
		BUSINESS PHONE:		7814499560

	MAIL ADDRESS:	
		STREET 1:		41 SEYON STREET
		STREET 2:		BUILDING 1, SUITE 100
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02453

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BVF PARTNERS L P/IL
		CENTRAL INDEX KEY:			0001055947

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-14656
		FILM NUMBER:		09843146

	BUSINESS ADDRESS:	
		STREET 1:		ONE SANSOME ST
		STREET 2:		39TH FL
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94104
		BUSINESS PHONE:		3125066500

	MAIL ADDRESS:	
		STREET 1:		900 N. MICHIGAN AVENUE
		STREET 2:		SUITE 1100
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60611

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BIOTECHNOLOGY VALUE FUND L P
		CENTRAL INDEX KEY:			0000918923
		STANDARD INDUSTRIAL CLASSIFICATION:	INVESTMENT ADVICE [6282]
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-14656
		FILM NUMBER:		09843145

	BUSINESS ADDRESS:	
		STREET 1:		900 N. MICHIGAN AVENUE, SUITE 1100
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60611
		BUSINESS PHONE:		3125066500

	MAIL ADDRESS:	
		STREET 1:		900 N. MICHIGAN AVENUE, SUITE 1100
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60611

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BVF INC/IL
		CENTRAL INDEX KEY:			0001056807
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-14656
		FILM NUMBER:		09843141

	BUSINESS ADDRESS:	
		STREET 1:		ONE SANSOME ST
		STREET 2:		39TH FLOOR
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94104
		BUSINESS PHONE:		3125066500

	MAIL ADDRESS:	
		STREET 1:		C/O GROSVENOR CAPITAL MANAGEMENT
		STREET 2:		900 N. MICHIGAN AVENUE, SUITE 1100
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60611

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BIOTECHNOLOGY VALUE FUND II LP
		CENTRAL INDEX KEY:			0001102444
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-14656
		FILM NUMBER:		09843144

	BUSINESS ADDRESS:	
		STREET 1:		ONE SANSOME ST
		STREET 2:		39TH FL.
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94104
		BUSINESS PHONE:		3125066500

	MAIL ADDRESS:	
		STREET 1:		C/O GROSVENOR CAPITAL MANAGEMENT
		STREET 2:		900 N. MICHIGAN AVENUE, SUITE 1100
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60611

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BVF INVESTMENTS LLC
		CENTRAL INDEX KEY:			0001132245
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-14656
		FILM NUMBER:		09843143

	BUSINESS ADDRESS:	
		STREET 1:		ONE SANSOME ST. 39TH FL
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94104
		BUSINESS PHONE:		3125066500

	MAIL ADDRESS:	
		STREET 1:		C/O GROSVENOR CAPITAL MANAGEMENT LP
		STREET 2:		900 N. MICHIGAN AVENUE, SUITE 1100
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60611
</SEC-HEADER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>bvfrepligen-form3_ex.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0203</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2009-05-15</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000730272</issuerCik>
        <issuerName>REPLIGEN CORP</issuerName>
        <issuerTradingSymbol>RGEN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001055947</rptOwnerCik>
            <rptOwnerName>BVF PARTNERS L P/IL</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>900 N. MICHIGAN AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 1100</rptOwnerStreet2>
            <rptOwnerCity>CHICAGO</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60611</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Group Member</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000918923</rptOwnerCik>
            <rptOwnerName>BIOTECHNOLOGY VALUE FUND L P</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>900 N. MICHIGAN AVENUE, SUITE 1100</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>CHICAGO</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60611</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Group Member</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001102444</rptOwnerCik>
            <rptOwnerName>BIOTECHNOLOGY VALUE FUND II LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O GROSVENOR CAPITAL MANAGEMENT</rptOwnerStreet1>
            <rptOwnerStreet2>900 N. MICHIGAN AVENUE, SUITE 1100</rptOwnerStreet2>
            <rptOwnerCity>CHICAGO</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60611</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Group Member</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001132245</rptOwnerCik>
            <rptOwnerName>BVF INVESTMENTS LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O GROSVENOR CAPITAL MANAGEMENT LP</rptOwnerStreet1>
            <rptOwnerStreet2>900 N. MICHIGAN AVENUE, SUITE 1100</rptOwnerStreet2>
            <rptOwnerCity>CHICAGO</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60611</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Group Member</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001056807</rptOwnerCik>
            <rptOwnerName>BVF INC/IL</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O GROSVENOR CAPITAL MANAGEMENT</rptOwnerStreet1>
            <rptOwnerStreet2>900 N. MICHIGAN AVENUE, SUITE 1100</rptOwnerStreet2>
            <rptOwnerCity>CHICAGO</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60611</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Group Member</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001233840</rptOwnerCik>
            <rptOwnerName>LAMPERT MARK N</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2415 GREEN ST</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94123</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Group Member</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>825750</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>534400</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1856700</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F3"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3216850</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F4"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>General partner and manager of entities with direct ownership.</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3216850</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F5"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>General partner of entity with indirect ownership.</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3216850</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F6"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Sole shareholder and sole director of entity with indirect ownership.</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The shares of Common Stock are directly beneficially owned by Biotechnology Value Fund, L.P. (&quot;BVF&quot;), a Delaware limited
 partnership.</footnote>
        <footnote id="F2">The shares of Common Stock are directly beneficially owned by Biotechnology Value Fund II, L.P. (&quot;BVF2&quot;), a Delaware limited
 partnership.</footnote>
        <footnote id="F3">The shares of Common Stock are directly beneficially owned by BVF Investments, LLC (&quot;BVFLLC&quot;),   a Delaware limited liability
 company.  Pursuant to the operating agreement of BVFLLC, BVF Partners, L.P., a Delaware limited partnership (&quot;Partners&quot;) is
 authorized, among other things, to invest the contributed capital of Samana Capital, L.P., the majority member of BVFLLC, in
 the shares of Common Stock and other securities and to vote, exercise or convert and dispose of such securities and is
 entitled to receive fees based on assets under management and, subject to certain exceptions, allocations based on realized
 and unrealized gains on such assets.</footnote>
        <footnote id="F4">The shares of Common Stock are indirectly beneficially owned by Partners.  Partners is the general partner of BVF and BVF2
 and is the manager of BVFLLC.</footnote>
        <footnote id="F5">The shares of Common Stock are indirectly beneficially owned by BVF Inc., a Delaware corporation (&quot;BVF Inc.&quot;).  BVF Inc. is
 the general partner of Partners.</footnote>
        <footnote id="F6">Mark N. Lampert is the sole shareholder, sole director, and an officer of BVF Inc.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>BVF PARTNERS L.P., By: BVF Inc., its General Partner,  By: /s/ Mark N. Lampert, President</signatureName>
        <signatureDate>2009-05-20</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BIOTECHNOLOGY VALUE FUND, L.P., By: BVF Partners L.P.,  its General Partner, By: BVF Inc., its General Partner,  By: /s/ Mark N. Lampert, President</signatureName>
        <signatureDate>2009-05-20</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BIOTECHNOLOGY VALUE FUND II, L.P., By: BVF Partners L.P.,  its General Partner, By: BVF Inc., its General Partner,  By: /s/ Mark N. Lampert, President</signatureName>
        <signatureDate>2009-05-20</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BVF INVESTMENTS, L.L.C., By: BVF Partners L.P.,  its Manager, By: BVF Inc., its General Partner,  By: /s/ Mark N. Lampert, President</signatureName>
        <signatureDate>2009-05-20</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BVF INC., By: /s/ Mark N. Lampert, President</signatureName>
        <signatureDate>2009-05-20</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Mark N. Lampert, By: /s/ Mark N. Lampert</signatureName>
        <signatureDate>2009-05-20</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----
