<SEC-DOCUMENT>0000899243-18-029744.txt : 20181128
<SEC-HEADER>0000899243-18-029744.hdr.sgml : 20181128
<ACCEPTANCE-DATETIME>20181128164332
ACCESSION NUMBER:		0000899243-18-029744
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20181126
FILED AS OF DATE:		20181128
DATE AS OF CHANGE:		20181128

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Snodgres Jon
		CENTRAL INDEX KEY:			0001613498

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-14656
		FILM NUMBER:		181206086

	MAIL ADDRESS:	
		STREET 1:		REPLIGEN CORPORATION, 41 SEYON STREET
		STREET 2:		BUILDING #1, SUITE 100
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02435

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
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc4.xml
<DESCRIPTION>FORM 4 SUBMISSION
<TEXT>
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    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-11-26</periodOfReport>

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        <issuerName>REPLIGEN CORP</issuerName>
        <issuerTradingSymbol>RGEN</issuerTradingSymbol>
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            <rptOwnerName>Snodgres Jon</rptOwnerName>
        </reportingOwnerId>
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            <rptOwnerStreet2>41 SEYON ST., BLDG 1, STE 100</rptOwnerStreet2>
            <rptOwnerCity>WALTHAM</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02453</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
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            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CFO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

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                <value>Common Stock</value>
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            <transactionDate>
                <value>2018-11-26</value>
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                <value></value>
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            <transactionAmounts>
                <transactionShares>
                    <value>11445</value>
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                <transactionPricePerShare>
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                <transactionAcquiredDisposedCode>
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                    <value>A</value>
                </transactionAcquiredDisposedCode>
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            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>52652</value>
                </sharesOwnedFollowingTransaction>
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                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2018-11-26</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>31753</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>63.4874</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>20899</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>26.20</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2018-11-26</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>11445</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
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            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2025-02-26</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
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                <sharesOwnedFollowingTransaction>
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                <value>2018-11-26</value>
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                <equitySwapInvolved>0</equitySwapInvolved>
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                <value></value>
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                <transactionShares>
                    <value>4000</value>
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                <transactionPricePerShare>
                    <value>0.00</value>
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                <transactionAcquiredDisposedCode>
                    <value>D</value>
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            <exerciseDate>
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            </expirationDate>
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                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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                <value></value>
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                <transactionShares>
                    <value>6055</value>
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                <transactionPricePerShare>
                    <value>0.00</value>
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                <transactionAcquiredDisposedCode>
                    <value>D</value>
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                <value>2027-02-23</value>
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                    <value>Common Stock</value>
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                    <value>6055</value>
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                    <value>12110</value>
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                <directOrIndirectOwnership>
                    <value>D</value>
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                <value>26.05</value>
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                <value>2018-11-26</value>
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                    <value>10253</value>
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                    <value>0.00</value>
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                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
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                <footnoteId id="F6"/>
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            <expirationDate>
                <value>2026-02-26</value>
            </expirationDate>
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                <underlyingSecurityTitle>
                    <value>Common Stock</value>
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                    <value>5127</value>
                </sharesOwnedFollowingTransaction>
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    <footnotes>
        <footnote id="F1">Sale of common stock was effective pursuant to a 10(b)5-1 trading plan adopted on September 19, 2018.</footnote>
        <footnote id="F2">$63.4874 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $63.18 to $64.71, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range.</footnote>
        <footnote id="F3">This option is currently exercisable.</footnote>
        <footnote id="F4">2,000 shares vest and become exercisable on each of the following dates: 7/14/2015, 7/14/2016, 7/14/2017, 7/14/2018 and 7/14/2019.</footnote>
        <footnote id="F5">6,055 shares vest and become exercisable on each of the following dates: 2/23/2018, 2/23/2019 and 2/23/2020.</footnote>
        <footnote id="F6">Shares vest and become exercisable as follows: 5,126 shares on 2/26/2017, 5,127 shares on 2/26/2018 and 5,127 shares on 2/26/2019.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Jeffrey P. Leduc (Attorney in Fact)</signatureName>
        <signatureDate>2018-11-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
