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            <secFileNumber>000-19034</secFileNumber>
            <issuerAddress>
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                <ns2:city>Tarrytown</ns2:city>
                <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                <ns2:zipCode>10591-6707</ns2:zipCode>
            </issuerAddress>
            <issuerContactPhone>(914) 847-7000</issuerContactPhone>
            <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>GEORGE L. SING</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>8th Floor</ns2:street2>
                    <ns2:city>New York</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10004</ns2:zipCode>
                </address>
            </brokerOrMarketmakerDetails>
            <noOfUnitsSold>1000</noOfUnitsSold>
            <aggregateMarketValue>992500.00</aggregateMarketValue>
            <noOfUnitsOutstanding>107943750</noOfUnitsOutstanding>
            <approxSaleDate>02/26/2024</approxSaleDate>
            <securitiesExchangeName>NASDAQ</securitiesExchangeName>
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            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>02/06/2024</acquiredDate>
            <natureOfAcquisitionTransaction>Exercise of options under a registered plan</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>1000</amountOfSecuritiesAcquired>
            <paymentDate>02/06/2024</paymentDate>
            <natureOfPayment>Cash</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
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                <name>GEORGE L. SING</name>
                <address>
                    <ns2:street1>777 Old Saw Mill River Road</ns2:street1>
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                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10591-6707</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <saleDate>02/23/2024</saleDate>
            <amountOfSecuritiesSold>500</amountOfSecuritiesSold>
            <grossProceeds>492500.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>GEORGE L. SING</name>
                <address>
                    <ns2:street1>777 Old Saw Mill River Road</ns2:street1>
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                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10591-6707</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <saleDate>02/22/2024</saleDate>
            <amountOfSecuritiesSold>3000</amountOfSecuritiesSold>
            <grossProceeds>1925000.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>GEORGE L. SING</name>
                <address>
                    <ns2:street1>777 Old Saw Mill River Road</ns2:street1>
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                    <ns2:zipCode>10591-6707</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <saleDate>02/09/2024</saleDate>
            <amountOfSecuritiesSold>500</amountOfSecuritiesSold>
            <grossProceeds>477500.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>GEORGE L. SING</name>
                <address>
                    <ns2:street1>777 Old Saw Mill River Road</ns2:street1>
                    <ns2:city>Tarrytown</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10591-6707</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <saleDate>02/08/2024</saleDate>
            <amountOfSecuritiesSold>500</amountOfSecuritiesSold>
            <grossProceeds>472500.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <noticeSignature>
            <noticeDate>02/26/2024</noticeDate>
            <planAdoptionDates/>
            <signature>/s/ George L Sing</signature>
        </noticeSignature>
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144
0001225471
XXXXXXXX
LIVE
0000872589
REGENERON PHARMACEUTICALS INC.
000-19034
777 Old Saw Mill River Road
Tarrytown
NY
10591-6707
(914) 847-7000
GEORGE L. SING
Officer
Common
Morgan Stanley Smith Barney LLC Executive Financial Services
1 New York Plaza
8th Floor
New York
NY
10004
1000
992500.00
107943750
02/26/2024
NASDAQ
Common
02/06/2024
Exercise of options under a registered plan
Issuer
N
1000
02/06/2024
Cash
N
GEORGE L. SING
777 Old Saw Mill River Road
Tarrytown
NY
10591-6707
Common
02/23/2024
500
492500.00
GEORGE L. SING
777 Old Saw Mill River Road
Tarrytown
NY
10591-6707
Common
02/22/2024
3000
1925000.00
GEORGE L. SING
777 Old Saw Mill River Road
Tarrytown
NY
10591-6707
Common
02/09/2024
500
477500.00
GEORGE L. SING
777 Old Saw Mill River Road
Tarrytown
NY
10591-6707
Common
02/08/2024
500
472500.00
02/26/2024
/s/ George L Sing