SC 13G: Arcellx, Inc.

AI Summary

SC 13G filing by Arcellx, Inc..

Risk Assessment

Risk Level: low

Key Financial Figures

• $0.001 — ame of Issuer) Common Stock, par value $0.001 per share (Title of Class of Securiti

Filing Documents

• tm2429234d1_sc13g.htm (SC 13G) — 74KB
• tm2429234d1_ex1.htm (EX-99.1) — 7KB
• 0001104659-24-122103.txt ( ) — 83KB

(a). Name of Issuer

Item 1(a). Name of Issuer: Arcellx, Inc. (the “ Issuer ”)

(b). Address of Issuer’s Principal Executive Offices

Item 1(b). Address of Issuer’s Principal Executive Offices: 800 Bridge Parkway, Redwood City, CA 94065

(a). Names of Persons Filing

Item 2(a). Names of Persons Filing: The names of the persons filing this report (collectively, the “ Reporting Persons ”) are: RA Capital Management, L.P. (“ RA Capital ”) Peter Kolchinsky Rajeev Shah RA Capital Healthcare Fund, L.P. (the “ Fund ”)

(b). Address of Principal Business Office or, if None, Residence

Item 2(b). Address of Principal Business Office or, if None, Residence: The address of the principal business office of each of the Reporting Persons is: c/o RA Capital Management, L.P., 200 Berkeley Street, 18th Floor, Boston MA 02116

(c). Citizenship

Item 2(c). Citizenship: RA Capital and the Fund are Delaware limited partnerships. Dr. Kolchinsky and Mr. Shah are United States citizens.

(d). Title of Class of Securities

Item 2(d). Title of Class of Securities: Common Stock, par value $0.001 per share (“ Common Stock ”)

(e). CUSIP Number

Item 2(e). CUSIP Number: 03940C100

If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c),

Item 3. If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a: Not applicable.

Ownership

Item 4. Ownership. 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 pages to this Schedule 13G. The ownership percentages reported are based upon 54,074,670 shares of Common Stock outstanding as of November 1, 2024, as reported in the Issuer’s Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (the “ SEC ”) on November 7, 2024. The Fund directly holds 2,787,327 shares of Common Stock. RA Capital Healthcare Fund GP, LLC is the general partner of the Fund. The general partner of RA Capital is RA Capital Management GP, LLC, of which Dr. Kolchinsky and Mr. Shah are the controlling persons. RA Capital serves as investment adviser for the Fund and may be deemed a beneficial owner, for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended (“ Act ”), of any securities of the Issuer held by the Fund. The Fund has delegated to RA Capital the sole power to vote and the sole power to dispose of all securities held in the Fund’s portfolio, including the shares of the Issuer’s Common Stock reported herein. Because the Fund has divested voting and investment power over the reported securities it holds and may not revoke that delegation on less than 61 days’ notice, the Fund disclaims beneficial ownership of the securities it holds for purposes of Section 13(d) of the Act and therefore disclaims any obligation to report ownership of the reported securities under Section 13(d) of the Act. As managers of RA Capital, Dr. Kolchinsky and Mr. Shah may be deemed beneficial owners, for purposes of Section 13(d) of the Act, of any securities of the Issuer beneficially owned by RA Capital. RA Capital, Dr. Kolchinsky, and Mr. Shah disclaim beneficial ownership of the securities reported in this Schedule 13G other than for the purpose of determining their obligations under Section 13(d) of the Act, and the filing

Ownership of Five Percent or Less of a Class

Item 5. Ownership of Five Percent or Less of a Class. 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 ¨

Ownership of More than Five Percent on Behalf of Another Person

Item 6. Ownership of More than Five Percent on Behalf of Another Person. Not applicable.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by

Item 7. Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person. Not applicable.

Identification and Classification of Members of the Group

Item 8. Identification and Classification of Members of the Group. Not applicable.

Notice of Dissolution of Group

Item 9. Notice of Dissolution of Group. Not applicable.

Certification

Item 10. Certification. 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. Exhibit List Exhibit 1: Joint Filing Agreement SIGNATURE After reasonable inquiry and to the best of its or his knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct. Dated: November 22, 2024 RA CAPITAL MANAGEMENT, L.P. By: /s/ Peter Kolchinsky Name: Peter Kolchinsky Title: Authorized Signatory PETER KOLCHINSKY /s/ Peter Kolchinsky RAJEEV SHAH /s/ Rajeev Shah RA CAPITAL HEALTHCARE FUND, L.P. By: RA Capital Healthcare Fund GP, LLC Its: General Partner By: /s/ Peter Kolchinsky Name: Peter Kolchinsky Title: Manager

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