<SEC-DOCUMENT>0001140361-13-043498.txt : 20131119
<SEC-HEADER>0001140361-13-043498.hdr.sgml : 20131119
<ACCEPTANCE-DATETIME>20131119160909
ACCESSION NUMBER:		0001140361-13-043498
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		2
CONFORMED PERIOD OF REPORT:	20131115
FILED AS OF DATE:		20131119
DATE AS OF CHANGE:		20131119

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:			1231

	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:			Cox John
		CENTRAL INDEX KEY:			0001498428

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-14656
		FILM NUMBER:		131230087

	MAIL ADDRESS:	
		STREET 1:		C/O BIOGEN IDEC INC.
		STREET 2:		133 BOSTON POST ROAD
		CITY:			WESTON
		STATE:			MA
		ZIP:			02493
</SEC-HEADER>
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<SEQUENCE>1
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<DESCRIPTION>FORM 3
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    <periodOfReport>2013-11-15</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

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        <issuerCik>0000730272</issuerCik>
        <issuerName>REPLIGEN CORP</issuerName>
        <issuerTradingSymbol>RGEN</issuerTradingSymbol>
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        <reportingOwnerId>
            <rptOwnerCik>0001498428</rptOwnerCik>
            <rptOwnerName>Cox John</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O REPLIGEN CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>41 SEYON ST, BLDG 1, STE 100</rptOwnerStreet2>
            <rptOwnerCity>WALTHAM</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02453</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
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        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
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    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes></footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>William J. Kelly (Attorney in Fact)</signatureName>
        <signatureDate>2013-11-19</signatureDate>
    </ownerSignature>
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<DOCUMENT>
<TYPE>EX-24
<SEQUENCE>2
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<DESCRIPTION>POWER OF ATTORNEY
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<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt">Exhibit 24</font></div>

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<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="center"><font style="DISPLAY: inline; FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt">POWER OF ATTORNEY</font></div>

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<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt">KNOW ALL MEN BY THESE PRESENTS, that the undersigned hereby constitutes and </font><font style="DISPLAY: inline; FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt">appoints William J. Kelly the true and lawful attorney-in-fact and agent, with full power of substitution and resubstitution, for the undersigned and in the undersigned's name, place and stead, in any and all capacities (until revoked in writing) to execute for and on behalf of the undersigned, in any and all of the undersigned's capacities, any and all statements on Forms 3, 4 and 5 with respect to the undersigned's holdings of and transactions in securities issued by Repligen Corporation (the "Company") in accordance with Sections 16(a) of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), and any and all regulations promulgated thereunder, and to file the same, with all exhibits thereto, and any other documents in connection therewith, with the Securities and Exchange Commission, and with any other entity when and if such is mandated by the Exchange Act or by the By-laws of the Financial Industry Regulatory Authority, granting unto said attorney-in-fact and agent full power and authority to do and perform each and every act and thing requisite and necessary fully to all intents and purposes as the undersigned might or could do in person thereby ratifying and confirming all that said attorney-in-fact and agent, or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.</font></div>

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<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt">This Power of Attorney shall remain in full force and effect until the undersigned is no longer required to file Forms 3, 4 and 5 with respect to the undersigned's holdings of and transactions in securities issued by the Company, unless earlier revoked by the undersigned in a signed writing delivered to the foregoing attorney-in-fact.</font></div>

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<div style="TEXT-INDENT: 0pt; DISPLAY: block; MARGIN-LEFT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-FAMILY: Times New Roman; FONT-SIZE: 10pt">IN WITNESS WHEREOF, this Power of Attorney has been signed as of November 19, 2013.</font></div>

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