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        <filer>
          <filerCredentials>
            <cik>0001867644</cik>
            <ccc>XXXXXXXX</ccc>
          </filerCredentials>
        </filer>
        <liveTestFlag>LIVE</liveTestFlag>
  
  
      </filerInfo>
    </headerData>
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      <issuerInfo>
        <issuerCik>0001786205</issuerCik>
        <issuerName>Arcellx, Inc.</issuerName>
        <secFileNumber>001-41259</secFileNumber>
        <issuerAddress>
          <com:street1>800 BRIDGE PARKWAY</com:street1>
          <com:city>REDWOOD CITY</com:city>
          <com:stateOrCountry>CA</com:stateOrCountry>
          <com:zipCode>94065</com:zipCode>
        </issuerAddress>
        <issuerContactPhone>240-327-0603</issuerContactPhone>
        <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>SR One Co-Invest II, LLC</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>Shareholder</relationshipToIssuer>
        </relationshipsToIssuer>
      </issuerInfo>
      <securitiesInformation>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>Merrill Lynch</name>
          <address>
            <com:street1>555 California Street, Suite 1800</com:street1>
            <com:city>San Francisco</com:city>
            <com:stateOrCountry>CA</com:stateOrCountry>
            <com:zipCode>94104</com:zipCode>
          </address>
        </brokerOrMarketmakerDetails>
        <noOfUnitsSold>295737</noOfUnitsSold>
        <aggregateMarketValue>21733712.13</aggregateMarketValue>
        <noOfUnitsOutstanding>52796618</noOfUnitsOutstanding>
        <approxSaleDate>03/21/2024</approxSaleDate>
        <securitiesExchangeName>NASDAQ</securitiesExchangeName>
      </securitiesInformation>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>02/08/2022</acquiredDate>
        <natureOfAcquisitionTransaction>Initial Public Offering</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>295737</amountOfSecuritiesAcquired>
        <paymentDate>02/08/2022</paymentDate>
        <natureOfPayment>CASH</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
      <noticeSignature>
        <noticeDate>03/21/2024</noticeDate>
        <signature>James Macadam</signature>
      </noticeSignature>
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text: 144
  0001867644
  XXXXXXXX
  LIVE
  0001786205
  Arcellx, Inc.
  001-41259
  800 BRIDGE PARKWAY
  REDWOOD CITY
  CA
  94065
  240-327-0603
  SR One Co-Invest II, LLC
  Shareholder
  Common
  Merrill Lynch
  555 California Street, Suite 1800
  San Francisco
  CA
  94104
  295737
  21733712.13
  52796618
  03/21/2024
  NASDAQ
  Common
  02/08/2022
  Initial Public Offering
  ISSUER
  N
  295737
  02/08/2022
  CASH
  Y
  03/21/2024
  James Macadam