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        <filerInfo>
            <filer>
                <filerCredentials>
                    <cik>0001174475</cik>
                    <ccc>XXXXXXXX</ccc>
                </filerCredentials>
            </filer>
            <liveTestFlag>LIVE</liveTestFlag>



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    <formData>
        <issuerInfo>
            <issuerCik>0000872589</issuerCik>
            <issuerName>REGENERON PHARM</issuerName>
            <secFileNumber>000-19034</secFileNumber>
            <issuerAddress>
                <ns2:street1>777 Old Saw Mill Parkway</ns2:street1>
                <ns2:city>Tarrytown</ns2:city>
                <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                <ns2:zipCode>10591</ns2:zipCode>
            </issuerAddress>
            <issuerContactPhone>9148477468</issuerContactPhone>
            <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>Michael S. Brown</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <relationshipsToIssuer>
                <relationshipToIssuer>Officer</relationshipToIssuer>
            </relationshipsToIssuer>
        </issuerInfo>
        <securitiesInformation>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <brokerOrMarketmakerDetails>
                <name>Morgan Stanley Smith Barney LLC Executive Financial Services</name>
                <address>
                    <ns2:street1>1 New York Plaza</ns2:street1>
                    <ns2:street2>38th Fl.</ns2:street2>
                    <ns2:city>New York</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10004</ns2:zipCode>
                </address>
            </brokerOrMarketmakerDetails>
            <noOfUnitsSold>3070</noOfUnitsSold>
            <aggregateMarketValue>2450167.00</aggregateMarketValue>
            <noOfUnitsOutstanding>107507000</noOfUnitsOutstanding>
            <approxSaleDate>04/21/2023</approxSaleDate>
            <securitiesExchangeName>NASDAQ</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>04/21/2023</acquiredDate>
            <natureOfAcquisitionTransaction>Exercise of Stock Options</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>3070</amountOfSecuritiesAcquired>
            <paymentDate>04/21/2023</paymentDate>
            <natureOfPayment>Cash</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>10b5-1 Sales Plan for MICHAEL S BROWN MD</name>
                <address>
                    <ns2:street1>777 Old Saw Mill Parkway</ns2:street1>
                    <ns2:city>Tarrytown</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10591</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <saleDate>02/06/2023</saleDate>
            <amountOfSecuritiesSold>500</amountOfSecuritiesSold>
            <grossProceeds>398500.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>10b5-1 Sales Plan for MICHAEL S BROWN MD</name>
                <address>
                    <ns2:street1>777 Old Saw Mill Parkway</ns2:street1>
                    <ns2:city>Tarrytown</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10591</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <saleDate>02/06/2023</saleDate>
            <amountOfSecuritiesSold>3071</amountOfSecuritiesSold>
            <grossProceeds>2450658.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>10b5-1 Sales Plan for MICHAEL S BROWN MD</name>
                <address>
                    <ns2:street1>777 Old Saw Mill Parkway</ns2:street1>
                    <ns2:city>Tarrytown</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10591</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <saleDate>01/27/2023</saleDate>
            <amountOfSecuritiesSold>1</amountOfSecuritiesSold>
            <grossProceeds>747.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <noticeSignature>
            <noticeDate>04/21/2023</noticeDate>
            <planAdoptionDates>
                <planAdoptionDate>02/22/2023</planAdoptionDate>
            </planAdoptionDates>
            <signature>/S/ Michael Brown</signature>
        </noticeSignature>
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144
0001174475
XXXXXXXX
LIVE
0000872589
REGENERON PHARM
000-19034
777 Old Saw Mill Parkway
Tarrytown
NY
10591
9148477468
Michael S. Brown
Officer
COMMON
Morgan Stanley Smith Barney LLC Executive Financial Services
1 New York Plaza
38th Fl.
New York
NY
10004
3070
2450167.00
107507000
04/21/2023
NASDAQ
Common
04/21/2023
Exercise of Stock Options
Issuer
N
3070
04/21/2023
Cash
N
10b5-1 Sales Plan for MICHAEL S BROWN MD
777 Old Saw Mill Parkway
Tarrytown
NY
10591
Common
02/06/2023
500
398500.00
10b5-1 Sales Plan for MICHAEL S BROWN MD
777 Old Saw Mill Parkway
Tarrytown
NY
10591
Common
02/06/2023
3071
2450658.00
10b5-1 Sales Plan for MICHAEL S BROWN MD
777 Old Saw Mill Parkway
Tarrytown
NY
10591
Common
01/27/2023
1
747.00
04/21/2023
02/22/2023
/S/ Michael Brown