Sec Form 4 Filing - Radhakrishnan Anup @ CARGO Therapeutics, Inc. - 2025-08-18

FORM 4 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 Radhakrishnan Anup 2. Issuer Name and Ticker or Trading Symbol CARGO Therapeutics, Inc. [ CRGX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) See Remarks (Last) (First) (Middle) C/O CARGO THERAPEUTICS, INC., 835 INDUSTRIAL ROAD, SUITE 400 3. Date of Earliest Transaction (MM/DD/YY) 08/18/2025 (Street) SAN CARLOS, CA94070 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 Common Stock 08/18/2025 U 57,345 ( 1 ) ( 2 ) D $ 4.379 63,436 D Common Stock 08/19/2025 D 63,436 ( 3 ) ( 4 ) D $ 4.379 0 D

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 Stock Option (Right to Buy) $ 1.09 08/19/2025 D 14,679 ( 5 )( 6 ) 10/06/2032 Common Stock 14,679 ( 5 ) ( 6 ) 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Radhakrishnan Anup C/O CARGO THERAPEUTICS, INC. 835 INDUSTRIAL ROAD, SUITE 400 SAN CARLOS, CA94070 See Remarks Signatures /s/ Halley Gilbert, as attorney-in-fact for Anup Radhakrishnan 08/19/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Disposed of pursuant to the Agreement and Plan of Merger (the "Merger Agreement"), dated as of July 7, 2025, by and among CARGO Therapeutics, Inc. (the "Issuer"), Concentra Biosciences, LLC ("Parent") and Concentra Merger Sub VII, Inc., a wholly owned subsidiary of Parent ("Merger Sub"). On August 18, 2025, Parent and Merger Sub completed a tender offer (the "Tender Offer") pursuant to the terms of the Merger Agreement for all outstanding shares of common stock of the Issuer (each, a "Share") for an offer price of (i) $4.379 per Share in cash (the "Cash Amount"), and (ii) one non-transferable contractual contingent value right (each, a "CVR"), subject to and in accordance with the terms of the Contingent Value Rights Agreement (the "CVR Agreement"), in each case, without interest, and subject to any applicable withholding taxes (the Cash Amount plus one CVR, collectively, the "Offer Price"). [continues to Footnote 2] ( 2 )[continues from Footnote 1] Merger Sub thereafter merged with and into the Issuer, effective as of August 19, 2025 (the "Effective Time"), with the Issuer continuing as the surviving corporation and a wholly owned subsidiary of Parent (the "Merger"). ( 3 )Pursuant to the terms of the Merger Agreement, immediately prior to the time at which Parent first irrevocably accepts for purchase the Shares tendered in the Tender Offer, each restricted stock unit award with respect to Shares that is, at the time of determination, subject to vesting or forfeiture conditions ("RSU Award") that is outstanding as of immediately prior thereto, shall (a) accelerate and become fully vested, and (b) by virtue of the Merger automatically (except as otherwise provided in the Merger Agreement) and without any action on the part of the Issuer, Parent or the holder thereof, be canceled and terminated and converted into the right to receive [continues to Footnote 4] ( 4 )[continues from Footnote 3] (i) an amount in cash without interest, subject to any applicable tax withholding, equal to the product of the number of Shares underlying such RSU Award immediately prior to the Effective Time and $4.379 in cash, plus (ii) one CVR with respect to each Share subject to such RSU Award immediately prior to the Effective Time. ( 5 )As of immediately prior to and conditioned upon the Effective Time, pursuant to the Merger Agreement, each outstanding option to purchase Shares (each, an "Option") became fully vested and exercisable, and to the extent not exercised prior to the Effective Time of the Merger, was canceled and converted into the right to receive (a) an amount in cash (without interest and subject to deduction for any required withholding tax) equal to the product of (1) the excess, if any, of the Cash Amount over the exercise price per share of each such Option and (2) the number of Shares underlying such Option immediately prior to the Effective Time [continues to Footnote 6] ( 6 )[continues from Footnote 5] and (b) one CVR in respect of each Share underlying such Option; provided, however, that if the exercise price per Share of any Option was equal to or greater than the Cash Amount that was then outstanding it was canceled for no consideration.

Remarks: Title: Interim Chief Executive Officer, Chief Financial Officer and Chief Operating Officer

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