SR One Capital Management SC 13D/AArcellx / SR ONE CAPITAL MANAGEMENT ownership change

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 2)*

Arcellx, Inc.

(Name of Issuer)

Common Stock, par value $0.0001

(Title of Class of Securities)

03940C 10 0

(CUSIP Number)

Sasha Keough

c/o SR One Capital Management, LP

985 Old Eagle School Road, Suite 511

Wayne, PA 19087

410-800-7503

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

May 11, 2023

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box  ☐.

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See § 240.13d-7 for other parties to whom copies are to be sent.

The information required on 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)

Item 1 of the Schedule 13D is hereby amended and supplemented as follows:

This Amendment No. 2 (this “Amendment No. 2”) to Schedule 13D amends and supplements the statements on the Schedule 13D originally filed with the SEC by the Reporting Persons on February 17, 2022, and Amendment No. 1 filed with the SEC by the Reporting Persons on June 27, 2022, relating to the common stock, $0.0001 par value per share (the “Common Stock”) of Arcellx, Inc., a Delaware corporation (the “Issuer”). The address of the Issuer’s principal executive offices is 25 West Watkins Mill Road, Suite A, Gaithersburg, Maryland 20878.

Certain terms used but not defined in this Amendment No. 2 have the meanings assigned thereto in the Schedule 13D (including Amendment No. 1 thereto). Except as specifically provided herein, this Amendment No. 2 does not modify any of the information previously reported on the Schedule 13D (including Amendment No. 1 thereto).

N/A. The Reporting Persons sold Common Stock.

The response set forth in Item 4 of the Schedule 13D is hereby supplemented as follows:

On May 11, 2023, SR One Fund I Aggregator LP (“Aggregator”) and SR One Co-Invest II, LLC (“Co-Invest II”) each filed a Notice on Form 144 pursuant to Rule 144(h) under the Securities Act of 1933, as amended, stating their intention to sell up to 1,200,000 shares and 666,000 shares, respectively, of the Issuer’s Common Stock. On May 11, 2023, (1) Aggregator sold in the aggregate 638,417 shares of the Issuer’s Common Stock and (2) Co-Invest II sold in the aggregate 374,416 shares of the Issuer’s Common Stock (collectively, the “Transactions”). The Transactions were comprised of a block trade and various open market transactions at prices that ranged from $45.00 to $46.56 per share. Depending on market conditions, their continuing evaluation of the business and prospects of the Issuer and other factors, Aggregator, Co-Invest II and other Reporting Persons may dispose of or acquire additional shares of the Issuer.

Except as set forth above, none of the Reporting Persons has any present plans which relate to or would result in:

(a) The acquisition by any person of additional securities of the Issuer, or the disposition of securities of the Issuer;

(b) An extraordinary corporate transaction, such as a merger, reorganization or liquidation, involving the Issuer or any of its subsidiaries;

(c) A sale or transfer of a material amount of assets of the Issuer or any of its subsidiaries;

(d) Any change in the present board of directors or management of the Issuer, including any plans or proposals to change the number or term of directors or to fill any existing vacancies on the board;

(e) Any material change in the present capitalization or dividend policy of the Issuer;

(f) Any other material change in the Issuer’s business or corporate structure;

(g) Changes in the Issuer’s charter, bylaws or instruments corresponding thereto or other actions which may impede the acquisition of control of the Issuer by any person;

(h) Causing a class of securities of the Issuer to be delisted from a national securities exchange or to cease to be authorized to be quoted in an inter-dealer quotation system of a registered national securities association;

(i) A class of equity securities of the Issuer becoming eligible for termination of registration pursuant to Section 12(g)(4) of the Securities Exchange Act of 1934; or

(j) Any action similar to any of those enumerated above.

The response set forth in Item 5 of the Schedule 13D is hereby amended by deleting the previous response in its entirety and replacing it with the following:

(a), (b) The information contained in rows 7, 8, 9, 10, 11, and 13 on each of the cover pages of this Amendment No. 2 is incorporated by reference in its entirety into this Item 5.

(c) Except as described herein, no transactions in shares of Common Stock were effected during the past 60 days by the Reporting Persons.

(d) No other person is known to have the right to receive or the power to direct the receipt of dividends from, or any proceeds from the sale of, Shares beneficially owned by any of the Reporting Persons.

SIGNATURES

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

Dated: May 19, 2023

This Amendment No. 2 was executed by Sasha Keough on behalf of the entities and individual listed above pursuant to a Power of Attorney a copy of which is attached as Exhibit 2.