Sec Form 3 Filing - Carroll Jill @ Arcellx, Inc. - 2022-02-03

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Carroll Jill 2. Issuer Name and Ticker or Trading Symbol Arcellx, Inc. [ ACLX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O ARCELLX, INC., 25 WEST WATKINS MILL ROAD, SUITE A 3. Date of Earliest Transaction (MM/DD/YY) 02/03/2022 (Street) GAITHERSBURG, MD20878 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Series A Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 1,550,309 I See footnote( 2 ) Series B-1 Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 666,651 I See footnote( 2 ) Series B-2 Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 533,389 I See footnote( 2 ) Series C Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 1,082,991 I See footnote( 3 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Carroll Jill C/O ARCELLX, INC. 25 WEST WATKINS MILL ROAD, SUITE A GAITHERSBURG, MD20878 X Signatures /s/ Lance Thibault, as Attorney-in-Fact 02/03/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )All shares of Series A Preferred Stock, par value $0.001 per share, Series B-1 Preferred Stock, par value $0.001 per share, Series B-2 Preferred Stock, par value $0.001 per share, and Series C Preferred Stock, par value $0.001 per share, of the Issuer will automatically be converted on a one-for-one basis to shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") prior to the closing of the Issuer's initial public offering of its Common Stock, and have no expiration date. ( 2 )Shares directly held by SR One Capital Fund I Aggregator, L.P. SR One Capital Partners I, LP serves as the general partner of SR One Capital Fund I Aggregator, LP and SR One Capital Management, LLC serves as the general partner of SR One Capital Partners I, LP. The Reporting Person, a member of the Issuer's board of directors, is a partner of SR One Capital Management, LP, an entity affiliated with SR One Capital Fund I Aggregator, L.P. and, therefore, may be deemed to have a pecuniary interest over these shares. The Reporting Person disclaims beneficial ownership of the shares held of record by SR One Capital Fund I Aggregator, L.P. except to the extent of her pecuniary interest therein. ( 3 )Consists of 649,795 shares held by SR One Capital Fund I Aggregator, L.P. and 433,196 shares held by SR One Co-Invest II, LLC. SR One Capital Partners I, LP serves as the general partner of SR One Capital Fund I Aggregator, LP and SR One Capital Management, LLC serves as the general partner of SR One Capital Partners I, LP. SR One Co-Invest Manager II, LLC serves as the manager of SR Co-Invest II, LLC, and SR One Capital Management, LLC serves as the managing member of SR Co-Invest Manager II, LLC. The Reporting Person, a member of the Issuer's board of directors, is a partner of SR One Capital Management, LP, an entity affiliated with SR One Capital Fund I Aggregator, L.P. and SR One Co-Invest II, LLC and, therefore, may be deemed to have a pecuniary interest over these shares. The Reporting person disclaims beneficial ownership of the shares held of record by SR One Capital Fund I Aggregator, L.P. and SR One Co-Invest II, LLC except to the extent of her pecuniary in

Remarks: Exhibit 24 - Power of Attorney

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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