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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>0000950127-05-000798.txt : 20051110
<SEC-HEADER>0000950127-05-000798.hdr.sgml : 20051110
<ACCEPTANCE-DATETIME>20051110144650
ACCESSION NUMBER:		0000950127-05-000798
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20051108
FILED AS OF DATE:		20051110
DATE AS OF CHANGE:		20051110

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			REGENERON PHARMACEUTICALS INC
		CENTRAL INDEX KEY:			0000872589
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				133444607
		STATE OF INCORPORATION:			NY
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		777 OLD SAW MILL RIVER RD
		CITY:			TARRYTOWN
		STATE:			NY
		ZIP:			10591-6707
		BUSINESS PHONE:		9143477000

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			NOVARTIS PHARMA AG
		CENTRAL INDEX KEY:			0001030617

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-19034
		FILM NUMBER:		051193371

	BUSINESS ADDRESS:	
		STREET 1:		LICHTSTRASSE 35
		STREET 2:		CH-4002
		CITY:			BASEL
		STATE:			V8
		BUSINESS PHONE:		212-830-2474

	MAIL ADDRESS:	
		STREET 1:		LICHTSTRASSE 35
		STREET 2:		CH-4002
		CITY:			BASEL
		STATE:			V8

	FORMER NAME:	
		FORMER CONFORMED NAME:	NOVARTIS INC
		DATE OF NAME CHANGE:	19970114
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>a5-365_ex.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-11-08</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0000872589</issuerCik>
        <issuerName>REGENERON PHARMACEUTICALS INC</issuerName>
        <issuerTradingSymbol>REGN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001030617</rptOwnerCik>
            <rptOwnerName>NOVARTIS PHARMA AG</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>LICHTSTRASSE 35</rptOwnerStreet1>
            <rptOwnerStreet2>CH-4002</rptOwnerStreet2>
            <rptOwnerCity>BASEL</rptOwnerCity>
            <rptOwnerState>V8</rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription>SWITZERLAND</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-11-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>7527050</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>11.06</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <valueOwnedFollowingTransaction>
                    <value>0</value>
                </valueOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <remarks>Novartis Pharma AG was formerly referred to as Novartis Inc.</remarks>

    <ownerSignature>
        <signatureName>Joseph E. Mamie, Head of Operational Treasury and Christina Ackermann, Head of Legal General Medicine, on behalf of Novartis Pharma AG</signatureName>
        <signatureDate>2005-11-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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