As filed with the Securities and Exchange Commission on June 14, 2024.

Registration No. 333-     

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

CARGO THERAPEUTICS, INC.

(Exact Name of Registrant as Specified in Its Charter)

835 Industrial Road, Suite 400

San Carlos, California 94070

(650) 445-8950

(Address, Including Zip Code, and Telephone Number, Including Area Code, of Registrant’s Principal Executive Offices)

Gina Chapman

Chief Executive Officer

CARGO Therapeutics, Inc.

835 Industrial Road, Suite 400

San Carlos, California 94070

(650) 379-6143

(Name, Address, Including Zip Code, and Telephone Number, Including Area Code, of Agent For Service)

Copies to:

Approximate date of commencement of proposed sale to the public: As soon as practicable after the effective date of this Registration Statement.

If any of the securities being registered on this form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box. ☒

If this form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

The Registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, or until the registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

The information in this preliminary prospectus is not complete and may be changed. These securities may not be sold until the registration statement filed with the Securities and Exchange Commission is effective. This preliminary prospectus is not an offer to sell these securities nor does it seek an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

Subject to Completion, dated June 14, 2024

6,471,000 shares of common stock

offered by the selling stockholders

This prospectus relates to the proposed resale or other disposition by the selling stockholders identified herein (the Selling Stockholders) of up to an aggregate of 6,471,000 shares of our common stock, par value $0.001 (the Resale Shares). We agreed to issue and sell the Resale Shares to the Selling Stockholders in a private placement pursuant to a securities purchase agreement (the Purchase Agreement) executed on May 28, 2024. We are registering the resale of these shares of common stock by the Selling Stockholders to satisfy registration rights we have granted to the Selling Stockholders.

We are not selling any common stock under this prospectus and will not receive any proceeds from the sale by the Selling Stockholders of the Resale Shares.

Sales of the Resale Shares by the Selling Stockholders may occur at fixed prices, at market prices prevailing at the time of sale, at prices related to prevailing market prices or at negotiated prices. The Selling Stockholders may sell shares to or through underwriters, broker-dealers or agents, who may receive compensation in the form of discounts, concessions or commissions from the Selling Stockholders, the purchasers of the Resale Shares, or both.

We do not know when or in what amount the Selling Stockholders may offer Resale Shares for sale. The Selling Stockholders may sell some, all or none of the Resale Shares offered by this prospectus. We will bear all costs, expenses and fees in connection with the registration of the Resale Shares, including with regard to compliance with state securities or “blue sky” laws. The Selling Stockholders will bear all commissions attributable to their sale of Resale Shares and all fees and expenses of legal counsel for any Selling Stockholder. See the section entitled “Plan of Distribution.”

Our common stock is listed on the Nasdaq Global Select Market (Nasdaq), under the symbol “CRGX.” The last reported sale price of our common stock on Nasdaq on June 13, 2024 was $17.18 per share.

We are an “emerging growth company” and a “smaller reporting company” as defined under the federal securities laws and, as such, have elected to comply with certain reduced public company reporting requirements.

Investing in our common stock involves a high degree of risk. See the section titled “Risk Factors” beginning on page 5.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the accuracy or adequacy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is    , 2024.

Table of contents

This prospectus is part of a registration statement on Form S-1 that we filed with the Securities and Exchange Commission (the SEC). Under this registration statement, the Selling Stockholders may sell from time to time the Resale Securities described in this prospectus in one or more offerings or otherwise as described in the section entitled “Plan of Distribution” beginning on page 16 of this prospectus.

We are responsible for the information contained in this prospectus. We have not, and the Selling Stockholders have not, authorized anyone to provide you with different information, and we take no, and the Selling Stockholders take no, responsibility for any other information others may give you. If anyone provides you with different or inconsistent information, you should not rely on it. We are not, and the Selling Stockholders are not, making an offer to sell the Resale Securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus, any prospectus supplement, the documents incorporated herein by reference and any related free writing prospectus is accurate only as of their respective dates. Our business, financial condition and results of operations may have changed since those dates.

For investors outside the United States: We have not, and the underwriters have not, done anything that would permit this offering or the possession or distribution of this prospectus or any free writing prospectus in connection with this offering in any jurisdiction where action for that purpose is required, other than in the United States. Persons outside the United States who come into possession of this prospectus must inform themselves about, and observe any restrictions relating to, the offering of the shares of common stock and the distribution of this prospectus outside the United States.

Unless otherwise indicated, information contained in this prospectus and the documented incorporated herein by reference concerning our industry and the markets in which we operate, including our general expectations and market position, market opportunity and market size, is based on information from various sources, on assumptions that we have made based on such information and other, similar sources and on our knowledge of, and expectations about, the markets for our products. In some cases, we do not expressly refer to the sources from which this data is derived. This information involves a number of assumptions and limitations, and you are cautioned not to give undue weight to such estimates. Projections, assumptions and estimates of our future performance and the future performance of the industry in which we operate is necessarily subject to a high

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degree of uncertainty and risk due to a variety of factors, including but not limited to those described in the section titled “Risk Factors” and elsewhere in this prospectus and the documents incorporated herein by reference. These and other factors could cause results to differ materially from those expressed in the estimates made by independent third parties and by us.

In this prospectus, “CARGO,” the “company,” “we,” “us” and “our” refer to CARGO Therapeutics, Inc. and, where appropriate, our subsidiaries.

“CARGO,” the CARGO logos and other trade names, trademarks or service marks of CARGO appearing in this prospectus are the property of CARGO. Other trade names, trademarks or service marks appearing in this prospectus are the property of their respective holders. Solely for convenience, trade names, trademarks and service marks referred to in this prospectus appear without the ^®, ^™ and ^SM symbols, but those references are not intended to indicate, in any way, that we will not assert, to the fullest extent under applicable law, our rights or that the applicable owner will not assert its rights, to these trade names, trademarks and service marks.

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Risk factors

Investing in our securities involves a high degree of risk. Prior to making a decision about investing in our securities, you should consider carefully the specific risk factors discussed under the heading “Risk Factors” in our most recent Annual Report on Form 10-K and subsequent Quarterly Reports on Form 10-Q, as filed with the SEC, which are incorporated herein by reference in their entirety, as well any amendment or updates to our risk factors reflected in subsequent filings with the SEC, including any applicable prospectus supplement hereto or any related free writing prospectus. These risks and uncertainties are not the only risks and uncertainties we face. Additional risks and uncertainties not presently known to us or that we currently believe to be immaterial also may materially and adversely affect our business, prospects, operating results and financial condition. For more information, see the section entitled “Where You Can Find Additional Information.” Please also read carefully the section entitled “Special Note Regarding Forward-Looking Statements.”

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Special note regarding forward-looking statements

This prospectus and the documents incorporated herein by reference contain forward-looking statements, particularly in the sections titled “Prospectus summary,” “Risk factors,” “Management’s discussion and analysis of financial condition and results of operations” and “Business.” In some cases, you can identify these statements by forward-looking words such as “aim,” “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “might,” “plan,” “potential,” “predict,” “should,” “would,” “will,” or the negative of these terms and other comparable terminology. These forward-looking statements, which are subject to risks, include, but are not limited to, statements about:

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We have based these forward-looking statements largely on our current expectations, estimates, forecasts and projections about future events and financial trends that we believe may affect our financial condition, results of operations, business strategy and financial needs. In light of the significant uncertainties in these forward-looking statements, you should not rely upon forward-looking statements as predictions of future events. Although we believe that we have a reasonable basis for each forward-looking statement contained in this prospectus, we cannot guarantee that the future results, levels of activity, performance or events and circumstances reflected in the forward-looking statements will be achieved or occur at all. You should refer to the section titled “Risk Factors” in this prospectus and the documented incorporated herein by reference for a discussion of important factors that may cause our actual results to differ materially from those expressed or implied by our forward-looking statements. Furthermore, if our forward-looking statements prove to be

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inaccurate, the inaccuracy may be material. Except as required by law, we undertake no obligation to publicly update any forward-looking statements, whether as a result of new information, future events or otherwise. The Private Securities Litigation Reform Act of 1995 and Section 27A of the Securities Act do not protect any forward-looking statements that we make in connection with this offering.

You should read this prospectus and the documented incorporated herein by reference completely and with the understanding that our actual future results may be materially different from what we expect. We qualify all of the forward-looking statements in this prospectus and the documented incorporated herein by reference by these cautionary statements.

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Use of proceeds

We will not receive any proceeds from the sale of the Resale Shares by the Selling Stockholders pursuant to this prospectus. The Selling Stockholders will pay any underwriting discounts and commissions and expenses they incur for brokerage, accounting, tax or legal services or any other expenses they incur in disposing of the Resale Shares. We will bear all other costs, fees and expenses incurred in effecting the registration of the Resale Shares covered by this prospectus, including, without limitation, all registration and filing fees and fees and expenses of our counsel and our accountants.

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Dividend policy

We have never declared or paid any cash dividends on our capital stock and do not anticipate paying any cash dividends in the foreseeable future. Any future determination as to the declaration or payment of dividends on our common stock will be made at the discretion of our board of directors and will depend upon, among other factors, our financial condition, results from operations, current and anticipated cash needs, plans for expansion and other factors that our board of directors may deem relevant.

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Selling stockholders

On May 28, 2024, we entered into the Purchase Agreement with the Selling Stockholders. The Purchase Agreement provides for the sale and issuance by us of 6,471,000 shares of our common stock. The Private Placement closed May 30, 2024 and we received gross proceeds of approximately $110.0 million. We are registering the Resale Shares pursuant to the registration rights granted to the Selling Stockholders as set forth in the Purchase Agreement to permit the Selling Stockholders to resell or otherwise dispose of the shares in the manner contemplated under “Plan of Distribution” below.

Except as otherwise disclosed herein and in the footnotes below with respect to the Selling Stockholder, the Selling Stockholders do not, and within the past three years have not had, any position, office or other material relationship with us.

The following table sets forth the name of each Selling Stockholder, the number of shares owned by such Selling Stockholder, the number of shares that may be offered under this prospectus and the number of shares of our common stock owned by the Selling Stockholders assuming all of the shares covered hereby are sold. The number of shares in the column “Number of Shares Being Offered” represents all of the shares that the Selling Stockholders may offer under this prospectus. The Selling Stockholders may sell some, all or none of their shares. We do not know how long the Selling Stockholders will hold the shares before selling them, and we currently have no agreements, arrangements or understandings with the Selling Stockholders regarding the sale or other disposition of any of the shares. The shares covered hereby may be offered from time to time by the Selling Stockholder. In computing the number of shares beneficially owned by a selling securityholder and their percentage ownership, shares of common stock subject to options, warrants or other rights held by such selling securityholder that are currently exercisable or will become exercisable within 60 days of June 13, 2024 are considered outstanding, although these shares are not considered outstanding for purposes of computing the percentage ownership of any other selling securityholder.

The information set forth below is based upon information obtained from the Selling Stockholders and upon information in our possession regarding the issuance of the Resale Shares sold to the Selling Stockholders in connection with the Private Placement. The percentages of shares owned after the offering are based on 45,861,750 shares of our common stock outstanding as of June 13, 2024, including the shares of common stock covered hereby.

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Plan of distribution

We are registering the Resale Shares issued to the Selling Stockholders to permit the resale of these shares of common stock from time to time after the date of this prospectus. We will not receive any of the proceeds from the sale by the Selling Stockholders of the Resale Shares. We will bear all fees and expenses incident to our obligation to register the Resale Shares (but excluding the fees of legal counsel for any Selling Stockholder).

The Selling Stockholders and any of their transferees, donees, pledgees or other successors in interest may, from time to time, sell all or a portion of the Resale Shares beneficially owned by the Selling Stockholders and offered hereby from time to time directly or through one or more underwriters, broker-dealers or agents. If the Resale Shares are sold through underwriters or broker-dealers, the Selling Stockholders will be responsible for underwriting discounts or commissions or agent’s commissions. The Resale Shares may be sold on any national securities exchange or quotation service on which the securities may be listed or quoted at the time of sale, in the over-the-counter market or in transactions otherwise than on these exchanges or systems or in the over-the-counter market and in one or more transactions at fixed prices, at prevailing market prices at the time of the sale, at varying prices determined at the time of sale, or at negotiated prices. These sales may be effected in transactions, which may involve crosses or block transactions. The Selling Stockholders may use any one or more of the following methods when selling the Resale Shares:

The Selling Stockholders also may resell all or a portion of the Resale Shares in open market transactions in reliance upon Rule 144 under the Securities Act, as permitted by that rule, or Section 4(a)(1) under the Securities Act, if available, rather than under this prospectus, provided that such Selling Stockholder meets the criteria and conforms to the requirements of those provisions.

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Broker-dealers engaged by the Selling Stockholders may arrange for other broker-dealers to participate in sales. If the Selling Stockholders effects such transactions by selling Resale Shares of common stock to or through underwriters, broker-dealers or agents, such underwriters, broker-dealers or agents may receive commissions in the form of discounts, concessions or commissions from the Selling Stockholders or commissions from purchasers of the shares of common stock for whom they may act as agent or to whom they may sell as principal. Such commissions will be in amounts to be negotiated, but, except as set forth in a supplement to this prospectus, in the case of an agency transaction will not be in excess of a customary brokerage commission in compliance with FINRA Rule 2121 (and any successor); and in the case of a principal transaction a markup or markdown in compliance with FINRA 2121.

In connection with sales of the Resale Shares or otherwise, the Selling Stockholders may enter into hedging transactions with broker-dealers or other financial institutions, which may in turn engage in short sales of the Resale Shares, or any other shares of our common stock such Selling Stockholder may hold, in the course of hedging in positions they assume. The Selling Stockholders may also sell shares of common stock short and if such short sale shall take place after the date that the registration statement of which this prospectus is a part is declared effective by the SEC, the Selling Stockholders may deliver shares of common stock covered by this prospectus to close out short positions and to return borrowed shares in connection with such short sales. The Selling Stockholders may also loan or pledge the Resale Shares to broker-dealers that in turn may sell such shares, to the extent permitted by applicable law. The Selling Stockholders may also enter into option or other transactions with broker-dealers or other financial institutions or the creation of one or more derivative securities which require the delivery to such broker-dealer or other financial institution of shares offered by this prospectus, which shares such broker-dealer or other financial institution may resell pursuant to this prospectus (as supplemented or amended to reflect such transaction).

The Selling Stockholders may, from time to time, pledge or grant a security interest in some or all of the shares of common stock owned by the Selling Stockholders (including the Resale Shares) and, if the Selling Stockholders defaults in the performance of its secured obligations, the pledgees or secured parties may offer and sell the shares of common stock from time to time pursuant to this prospectus or any amendment to this prospectus under Rule 424(b)(3) or other applicable provision of the Securities Act, as amended, amending, if necessary, the list of Selling Stockholders to include the pledgee, transferee or other successors in interest as a Selling Stockholders under this prospectus. The Selling Stockholders also may transfer and donate the shares of common stock in other circumstances in which case the transferees, donees, pledgees or other successors in interest will be the selling beneficial owners for purposes of this prospectus.

The Selling Stockholders and any broker-dealer or agents participating in the distribution of the shares of common stock may be deemed to be “underwriters” within the meaning of Section 2(11) of the Securities Act in connection with such sales. In such event, any commissions paid, or any discounts or concessions allowed to, any such broker-dealer or agent and any profit on the resale of the shares purchased by them may be deemed to be underwriting commissions or discounts under the Securities Act. If the Selling Stockholders is deemed to be an “underwriter” within the meaning of Section 2(11) of the Securities Act, it will be subject to the applicable prospectus delivery requirements of the Securities Act and may be subject to certain statutory liabilities of, including but not limited to, Sections 11, 12 and 17 of the Securities Act and Rule 10b-5 under the Exchange Act.

Each Selling Stockholder has informed us that it is not a registered broker-dealer and does not have any written or oral agreement or understanding, directly or indirectly, with any person to distribute the common stock. Upon our being notified in writing by the selling stockholder that any material arrangement has been entered into with a broker-dealer for the sale of common stock through a block trade, special offering, exchange

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distribution or secondary distribution or a purchase by a broker-dealer, a supplement to this prospectus will be filed, if required, pursuant to Rule 424(b) under the Securities Act, disclosing:

In no event shall any broker-dealer receive fees, commissions and markups, which, in the aggregate, would exceed eight percent (8%).

Under the securities laws of some states, the Resale Shares may be sold in such states only through registered or licensed brokers or dealers. In addition, in some states the Resale Shares may not be sold unless such shares have been registered or qualified for sale in such state or an exemption from registration or qualification is available and is complied with.

There can be no assurance that the Selling Stockholders will sell any or all of the Resale Shares.

Each Selling Stockholder and any other person participating in such distribution will be subject to applicable provisions of the Exchange Act and the rules and regulations thereunder, including, without limitation, Regulation M of the Exchange Act, which may limit the timing of purchases and sales of any of the shares of common stock by such Selling Stockholder and any other participating person. Regulation M may also restrict the ability of any person engaged in the distribution of the shares of common stock to engage in market-making activities with respect to the shares of common stock. All of the foregoing may affect the marketability of the shares of common stock and the ability of any person or entity to engage in market-making activities with respect to the shares of common stock.

To the extent required, this prospectus may be amended and/or supplemented from time to time to describe a specific plan of distribution.

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Legal matters

The validity of the issuance of the shares of common stock offered hereby will be passed upon for CARGO Therapeutics, Inc. by Latham & Watkins LLP, Menlo Park, California.

Experts

The financial statements of CARGO Therapeutics, Inc. as of December 31, 2023 and 2022, and for each of the two years in the period ended December 31, 2023, incorporated by reference in this prospectus have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their report. Such financial statements are incorporated by reference in reliance upon the report of such firm given their authority as experts in accounting and auditing.

Where you can find more information

We have filed with the Securities and Exchange Commission a registration statement on Form S-1 under the Securities Act with respect to the shares of common stock being offered by the Selling Stockholders named in this prospectus. This prospectus does not contain all of the information in the registration statement and its exhibits. For further information with respect to us and the common stock offered by this prospectus, we refer you to the registration statement and its exhibits. Where we make statements in this prospectus as to the contents of any contract or any other document, for the complete text of that document, we refer you to the copy of the contract or other document filed as an exhibit to the registration statement. Each of these statements is qualified in all respects by this reference. You can read our SEC filings, including the registration statement of which this prospectus is a part, over the Internet at the SEC’s website at www.sec.gov. We also maintain a website at www.cargo-tx.com, at which, you may access these materials free of charge as soon as reasonably practicable after documents are electronically filed with or furnished to the SEC. Our website and the information contained therein or connected thereto shall not be deemed to be incorporated into this prospectus or the registration statement of which it forms a part. We have included our website address as an inactive textual reference only.

Incorporation of information by reference

The SEC allows us to “incorporate by reference” information into this prospectus and the registration statement of which this prospectus is a part, which means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus, except for any information superseded by information contained directly in this prospectus, any prospectus supplement or any free writing prospectus prepared by or on behalf of us. This prospectus incorporates by reference the documents set forth below that we have previously filed with the SEC (other than information deemed furnished and not filed in accordance with SEC rules, including Items 2.02 and 7.01 of Form 8-K):

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These documents may also be accessed on our website at www.cargo-tx.com. Except as otherwise specifically incorporated by reference in this prospectus, information contained in, or accessible through, our website is not a part of this prospectus.

We will furnish without charge to you, upon written or oral request, a copy of any or all of the documents incorporated by reference, including exhibits to these documents by writing or telephoning us at the following address:

CARGO Therapeutics, Inc.

835 Industrial Road, Suite 400

San Carlos, California 94070

(650) 379-6143

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6,471,000 shares of common stock

offered by the selling stockholders

Prospectus

    , 2024

Part II

Information not required in prospectus

Item 13. Other expenses of issuance and distribution.

The following table sets forth the costs and expenses, other than underwriting discounts and commissions, payable by us in connection with the sale of the common stock being registered. All amounts are estimates except for the Securities and Exchange Commission (SEC) registration fee.

Item 14. Indemnification of directors and officers.

Section 145 of the Delaware General Corporation Law provides that a corporation may indemnify directors and officers as well as other employees and individuals against expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by such person in connection with any threatened, pending, or completed actions, suits, or proceedings in which such person is made a party by reason of such person being or having been a director, officer, employee, or agent to the registrant. The Delaware General Corporation Law provides that Section 145 is not exclusive of other rights to which those seeking indemnification may be entitled under any bylaw, agreement, vote of stockholders or disinterested directors or otherwise. Article 9 of the registrant’s amended and restated certificate of incorporation provides for indemnification by the registrant of its directors, officers and employees to the fullest extent permitted by the Delaware General Corporation Law. The registrant has entered into indemnification agreements with each of its current directors, executive officers and certain other officers to provide these directors and officers additional contractual assurances regarding the scope of the indemnification set forth in the registrant’s amended and restated certificate of incorporation and amended and restated bylaws and to provide additional procedural protections. There is no pending litigation or proceeding involving a director or executive officer of the registrant for which indemnification is sought.

Section 102(b)(7) of the Delaware General Corporation Law permits a corporation to provide in its certificate of incorporation that a director or an officer of the corporation shall not be personally liable to the corporation or its stockholders for monetary damages for breach of fiduciary duty as a director or an officer, except for liability (i) for any breach of the director’s or officer’s duty of loyalty to the corporation or its stockholders, (ii) for acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law, (iii) for unlawful payments of dividends or unlawful stock repurchases, redemptions, or other distributions, or (iv) for any transaction from which the director or officer derived an improper personal benefit. Delaware General Corporation Law also does not permit the limitation of monetary liability of officers in any action by or in the right of the corporation, such as a derivative claim. The registrant’s amended and restated certificate of incorporation provides for such limitation of liability.

The registrant maintains standard policies of insurance under which coverage is provided (i) to its directors and officers against loss rising from claims made by reason of breach of duty or other wrongful act and (ii) to the

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registrant with respect to payments that may be made by the registrant to such officers and directors pursuant to the above indemnification provision or otherwise as a matter of law.

Item 15. Recent sales of unregistered securities.

Since January 1, 2020, the registrant has sold the following securities without registration under the Securities Act of 1933:

Common stock issuances

From January 1, 2020 through the date of this registration statement, we issued and sold an aggregate of 1,169,853 shares of our common stock, par value $0.001 per share (Common Stock), for aggregate proceeds of approximately $0.3 million.

On May 30, 2024, we issued and sold 6,471,000 shares of our Common Stock for aggregate proceeds of approximately $110.0 million.

The offers, sales and issuances of the securities described above were exempt from registration under the Securities Act in reliance upon Section 4(a)(2) of the Securities Act or Regulation D promulgated thereunder as transactions by an issuer not involving any public offering. The recipients of the securities in each of these transactions represented their intentions to acquire the securities for investment only and not with a view to or for sale in connection with any distribution thereof, and appropriate legends were placed upon the stock certificates issued in these transactions. All recipients had adequate access, through their relationships with us, to information about our company.

Preferred stock issuances

In February 2021, we issued and sold an aggregate of 405,350 shares of our series seed convertible preferred stock, par value $0.001 per share (the Series Seed Preferred Stock), to (i) Samsara BioCapital, L.P. (Samsara), (ii) Red Tree Venture Fund, L.P. (Red Tree) and (iii) Emerson Collective Investments, LLC (Emerson and together with Samara and Red Tree, the Series Seed Investors) at a purchase price of $13.57 per share, for an aggregate price of approximately $5.5 million.

In January 2022, we issued and sold an aggregate of 405,350 shares of our Series Seed Preferred Stock to the Series Seed Investors at a purchase price of $13.57 per share, for an aggregate price of approximately $5.5 million.

In February 2023, we issued and sold an aggregate of 5,072,919 shares of our series A-1 convertible preferred stock, par value $0.001 per share (the Series A-1 Preferred Stock), to the purchasers listed on Exhibit A of the Series A Preferred Stock Purchase Agreement (the Series A Investors) at a purchase price of $13.57 per share, for an aggregate price of approximately $68.8 million (collectively, the Series A-1 Financing).

In February 2023, we issued and sold an aggregate of 3,229,851 shares of our series A-2 convertible preferred stock, par value $0.001 per share (the Series A-2 Preferred Stock), through the conversion of approximately $32.9 million aggregate principal amount of Convertible Notes outstanding at a conversion rate equal to the quotient obtained by dividing the (i) outstanding principal and unpaid accrued interest on the Convertible Notes converted, or portion thereof, on the date of conversion ($32.9 million), by (ii) the product of (A) seventy-five percent (75%) and (B) the lowest price paid per share of equity securities of the Company by investors in the Series A-1 Financing ($10.18), for a total of 3,229,851 shares of Series A-2 Preferred Stock to the Series Seed Investors at a purchase price of $10.18 per share, for an aggregate purchase price of approximately $32.9 million.

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In July 2023, we issued and sold an aggregate of 3,381,941 shares of our Series A-1 Preferred Stock to the Series A Investors at a purchase price of $13.57 per share, for an aggregate price of approximately $45.9 million (the Second Tranche Closing).

In October 2023, we issued and sold an aggregate of 6,341,148 shares of our Series A-1 Preferred Stock to the Series A Investors at a purchase price of $13.57 per share, for an aggregate price of approximately $86.0 million (the Third Tranche Closing).

The offers, sales and issuances of the securities described above were exempt from registration under the Securities Act in reliance upon Section 4(a)(2) of the Securities Act or Regulation D promulgated thereunder as transactions by an issuer not involving any public offering. The recipients of the securities in each of these transactions represented their intentions to acquire the securities for investment only and not with a view to or for sale in connection with any distribution thereof, and appropriate legends were placed upon the stock certificates issued in these transactions. All recipients had adequate access, through their relationships with us, to information about our company.

Equity awards

From January 1, 2020 through the date of this registration statement, we granted to our team members, officers and directors options to purchase an aggregate of 3,703,685 shares of common stock at per share exercise prices ranging from $1.09 to $9.50 under the CARGO Therapeutics, Inc. 2021 Stock Option and Grant Plan. From January 1, 2020 through the date of this registration statement, we issued an aggregate of 27,378 shares of common stock at per share purchase prices ranging from $1.09 to $9.50 pursuant to the exercise of options by our team members, officers and directors.

The offers, sales and issuances of the securities described above were exempt from registration under the Securities Act under either Rule 701, in that the transaction were under compensatory benefit plans and contracts relating to compensation, or under Section 4(a)(2) of the Securities Act in that the transactions were between an issuer and members of its senior executive management and did not involve any public offering within the meaning of Section 4(a)(2). The recipients of such securities were our employees, directors or consultants. Appropriate legends were affixed to the securities issued in these transactions.

Item 16. Exhibits and financial statement schedules.

Item 17. Undertakings.

II-3

II-4

Exhibit Index

II-5

II-6

Signatures

Pursuant to the requirements of the Securities Act of 1933, the registrant has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of San Carlos, State of California, on the 14th day of June, 2024.

Signatures and power of attorney

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below constitutes and appoints Gina Chapman and Anup Radhakrishnan and each of them, his or her true and lawful attorneys-in-fact and agents, with full power of substitution and resubstitution, for him or her and in his or her name, place and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments) to this registration statement and any and all additional registration statements pursuant to Rule 462(b) of the Securities Act of 1933, and to file the same, with all exhibits thereto, and all other documents in connection therewith, with the Securities and Exchange Commission, granting unto each said attorney-in-fact and agents full power and authority to do and perform each and every act in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or either of them or their or his or her substitute or substitutes may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed by the following persons in the capacities and on the dates indicated.

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II-8

Exhibit 5.1

Re: Registration Statement on Form S-1; 6,471,000 Shares of Common Stock, Par Value $0.001 Per Share

To the addressee set forth above:

We have acted as special counsel to CARGO Therapeutics, Inc., a Delaware corporation (the “Company”), in connection with the resale from time to time by the selling securityholders named in the Registration Statement (as defined below) of up to 6,471,000 shares (the “Shares”) of the Company’s common stock, par value $0.001 per share (the “Common Stock”). The Shares are included in a registration statement on Form S-1 under the Securities Act of 1933, as amended (the “Securities Act”), filed with the U.S. Securities and Exchange Commission (the “Commission”) on June 14, 2024 (the “Registration Statement”). This opinion is being furnished in connection with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act, and no opinion is expressed herein as to any matter pertaining to the contents of the Registration Statement or the prospectus contained therein, other than as expressly stated herein with respect to the issuance of the Shares.

As such counsel, we have examined such matters of fact and questions of law as we have considered appropriate for purposes of this letter. With your consent, we have relied upon certificates and other assurances of officers of the Company and others as to factual matters without having independently verified such factual matters. We are opining herein as to the General Corporation Law of the State of Delaware (the “DGCL”), and we express no opinion with respect to any other laws.

Subject to the foregoing and the other matters set forth herein, it is our opinion that, as of the date hereof:

1. The issuance of the Shares has been duly authorized by all necessary corporate action of the Company, and the Shares are validly issued, fully paid and non-assessable.

June 14, 2024

Page 2

This opinion is for your benefit in connection with the Registration Statement and may be relied upon by you and by persons entitled to rely upon it pursuant to the applicable provisions of the Securities Act. We consent to your filing this opinion as an exhibit to the Registration Statement and to the reference to our firm in the prospectus contained therein under the heading “Legal Matters.” In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission thereunder.

Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in this Registration Statement on Form S-1 of our report dated March 21, 2024 relating to the financial statements of CARGO Therapeutics, Inc. We also consent to the reference to us under the heading “Experts” in such Registration Statement.

/s/ Deloitte & Touche LLP

San Francisco, California

June 14, 2024

Exhibit 107

Calculation of Filing Fee Table

Registration Statement on Form S-1

(Form Type)

CARGO Therapeutics, Inc.

(Exact Name of Registrant as Specified in its Charter)

Table 1: Newly Registered and Carry Forward Securities