UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 13G/A

Under the Securities Exchange Act of 1934

(Amendment No. 1)*

CARGO Therapeutics, Inc.

(Name of Issuer)

Common Stock, $0.001 par value per share

(Title of Class of Securities)

14179K 10 1

(CUSIP Number)

December 31, 2023

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

☐ Rule 13d-1(b)

☒ Rule 13d-1(c)

☐ Rule 13d-1(d)

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No. 14179K 10 1

CUSIP No. 14179K 10 1

CUSIP No. 14179K 10 1

CUSIP No. 14179K 10 1

CARGO Therapeutics, Inc. (the “Issuer”)

1900 Alameda De Las Pulgas, Suite 350

San Mateo, California 94403

The names of the persons filing this report (collectively, the “Reporting Persons”) are:

Perceptive Advisors LLC (“Perceptive Advisors”)

Joseph Edelman (“Mr. Edelman”)

Perceptive Life Sciences Master Fund, Ltd. (the “Master Fund”)

Perceptive Xontogeny Venture Fund II, L.P. (“PXV II”)

The address of the principal business office of each of the Reporting Persons is:

51 Astor Place, 10th Floor

New York, NY 10003

Perceptive Advisors is a Delaware limited liability company

Mr. Edelman is a United States citizen

The Master Fund is a Cayman Islands corporation

PVX II is a Delaware limited partnership

Common Stock, $0.001 par value per share (“Common Stock”)

14179K 10 1

Not applicable.

The information required by this item with respect to each Reporting Person is set forth in Rows 5 through 9 and 11 of the cover page to this Schedule 13G. The ownership percentages reported are based on 41,205,142 shares of Common Stock outstanding as reported by the Issuer in its Form 10-Q filed with the Securities and Exchange Commission on December 13, 2023.

The Master Fund directly holds 523,765 shares of Common Stock and PXV II directly holds 2,912,835 shares of Common Stock. Perceptive Advisors serves as the investment manager to the Master Fund and may be deemed to beneficially own shares held by the Master Fund. Perceptive Venture Advisors, LLC is the investment manager of PXV II and is controlled by Perceptive Advisors, who may be deemed to beneficially own the shares held by PXV II. Perceptive Xontogeny Ventures II GP, LLC is the general partner of PXV II. Mr. Edelman is the managing member of Perceptive Advisors and may be deemed to beneficially own the shares held by the Master Fund and PXV II.

If this statement is being filed to report the fact that as of the date hereof the Reporting Persons have ceased to be the beneficial owner of more than five percent of the class of securities, check the following ☐.

Not applicable.

Not applicable.

Not applicable.

Not applicable.

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of its knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

Date: February 14, 2024

EXHIBIT 1

AGREEMENT

The persons below hereby agree that the Schedule 13G to which this agreement is attached as an exhibit, as well as all future amendments to such Schedule 13G, shall be filed on behalf of each of them. This agreement is intended to satisfy the requirements of Rule 13d-1(k)(1)(iii) under the Securities Exchange Act of 1934.

Date: February 14 2024