content: <?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
    <!-- Generated by Workiva -->
    <headerData>
      <submissionType>144</submissionType>
      <filerInfo>
        <filer>
          <filerCredentials>
            <cik>0001853723</cik>
            <ccc>XXXXXXXX</ccc>
          </filerCredentials>
        </filer>
        <liveTestFlag>LIVE</liveTestFlag>
  
  
  
      </filerInfo>
    </headerData>
    <formData>
      <issuerInfo>
        <issuerCik>0001786205</issuerCik>
        <issuerName>Arcellx, Inc.</issuerName>
        <secFileNumber>001-41259</secFileNumber>
        <issuerAddress>
          <com:street1>25 West Watkins Mill Rd,</com:street1>
          <com:city>Gaithersburg</com:city>
          <com:stateOrCountry>MD</com:stateOrCountry>
          <com:zipCode>20878</com:zipCode>
        </issuerAddress>
        <issuerContactPhone>240-723-6641</issuerContactPhone>
        <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>SR ONE CAPITAL MANAGEMENT LLC</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>affiliate</relationshipToIssuer>
        </relationshipsToIssuer>
      </issuerInfo>
      <securitiesInformation>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>J.P. Morgan Securities LLC</name>
          <address>
            <com:street1>360 Madison Avenue - 6th Floor</com:street1>
            <com:city>New York</com:city>
            <com:stateOrCountry>NY</com:stateOrCountry>
            <com:zipCode>10017</com:zipCode>
          </address>
        </brokerOrMarketmakerDetails>
        <noOfUnitsSold>666000</noOfUnitsSold>
        <aggregateMarketValue>31175460</aggregateMarketValue>
        <noOfUnitsOutstanding>47993520</noOfUnitsOutstanding>
        <approxSaleDate>05/11/2023</approxSaleDate>
        <securitiesExchangeName>Nasdaq</securitiesExchangeName>
      </securitiesInformation>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>03/21/2021</acquiredDate>
        <natureOfAcquisitionTransaction>Series C converted to Common at IPO</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>433196</amountOfSecuritiesAcquired>
        <paymentDate>03/21/2021</paymentDate>
        <natureOfPayment>Cash</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>02/08/2022</acquiredDate>
        <natureOfAcquisitionTransaction>IPO</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>1600000</amountOfSecuritiesAcquired>
        <paymentDate>03/21/2021</paymentDate>
        <natureOfPayment>Cash</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
      <noticeSignature>
        <noticeDate>05/11/2023</noticeDate>
        <signature>/s/ JPMS LLC as agent and attorney-in-fact for SR ONE CO-INVEST II, LLC</signature>
      </noticeSignature>
    </formData>
  </edgarSubmission>
metadata_documents: [{"type": "144", "sequence": "1", "filename": "primary_doc.xml", "secsgml_size_bytes": 3350}]
text: 144
  0001853723
  XXXXXXXX
  LIVE
  0001786205
  Arcellx, Inc.
  001-41259
  25 West Watkins Mill Rd,
  Gaithersburg
  MD
  20878
  240-723-6641
  SR ONE CAPITAL MANAGEMENT LLC
  affiliate
  Common
  J.P. Morgan Securities LLC
  360 Madison Avenue - 6th Floor
  New York
  NY
  10017
  666000
  31175460
  47993520
  05/11/2023
  Nasdaq
  Common
  03/21/2021
  Series C converted to Common at IPO
  Issuer
  N
  433196
  03/21/2021
  Cash
  Common
  02/08/2022
  IPO
  Issuer
  N
  1600000
  03/21/2021
  Cash
  Y
  05/11/2023
  /s/ JPMS LLC as agent and attorney-in-fact for SR ONE CO-INVEST II, LLC