Common Stock $0.001 par value per share

Arcellx, Inc.

800 Bridge Parkway, Redwood City, CA, 94065

New Enterprise Associates 15, L.P. ("NEA 15"), NEA Partners 15, L.P. ("NEA Partners 15"), which is the sole general partner of NEA 15; and NEA 15 GP, LLC ("NEA 15 LLC" and, together with NEA Partners 15, the "Control Entities"), which is the sole general partner of NEA Partners 15; and Forest Baskett ("Baskett"), Anthony A. Florence, Jr. ("Florence"), Mohamad H. Makhzoumi ("Makhzoumi") and Scott D. Sandell ("Sandell") (together, the "Managers"). The Managers are the managers of NEA 15 LLC. The persons named in this Item 2 are referred to individually herein as a "Reporting Person" and collectively as the "Reporting Persons."

The address of the principal business office of NEA 15, each Control Entity and Sandell is New Enterprise Associates, 1954 Greenspring Drive, Suite 600, Timonium, MD 21093. The address of the principal business office of Baskett and Makhzoumi is New Enterprise Associates, 2855 Sand Hill Road, Menlo Park, CA 94025. The address of the principal business office of Florence is New Enterprise Associates, 104 5th Avenue, 19th Floor, New York, NY 10011.

The principal business of NEA 15 is to invest in and assist growth-oriented businesses located principally in the United States. The principal business of NEA Partners 15 is to act as the sole general partner of NEA 15. The principal business of NEA 15 LLC is to act as the sole general partner of NEA Partners 15. The principal business of each of the Managers is to manage the Control Entities and a number of affiliated partnerships with similar businesses.

During the five years prior to the date hereof, none of the Reporting Persons has been convicted in a criminal proceeding or has been a party to a civil proceeding ending in a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

NEA 15 LLC is a limited liability company organized under the laws of the State of Delaware. NEA 15 and NEA Partners 15 are limited partnerships organized under the laws of the State of Delaware. Each of the Managers is a United States citizen.

NEA 15 is the record owner of the NEA 15 Shares (as defined below). As the general partner of NEA 15, NEA Partners 15 may be deemed to own beneficially the NEA 15 Shares. As the sole general partner of NEA Partners 15, NEA 15 LLC may be deemed to own beneficially the NEA 15 Shares. As members of NEA 15 LLC, each of the Managers may be deemed to own beneficially the NEA 15 Shares. Each Reporting Person disclaims beneficial ownership of the NEA 15 Shares other than those shares which such person owns of record. The percentage of outstanding Common Stock of the Issuer which may be deemed to be beneficially owned by each Reporting Person is set forth on Line 13 of such Reporting Person's cover sheet. Such percentage was calculated based on 55,458,912 shares of Common Stock reported by the Issuer to be outstanding as of August 1, 2025, on the Issuer's Form 10-Q filed with the Securities and Exchange Commission on August 7, 2025.

Regarding the number of shares as to which such person has: (i) sole power to vote or to direct the vote: See line 7 of cover sheets (ii) shared power to vote or to direct the vote: See line 8 of cover sheets (iii) sole power to dispose or to direct the disposition: See line 9 of cover sheets (iv) shared power to dispose or to direct the disposition: See line 10 of cover sheets.

On August 12, 2025, NEA 15 made a pro rata distribution of 700,000 shares of Common Stock of the Issuer to its general partner and its limited partners for no consideration (the "NEA 15 Distribution"). NEA Partners 15 acquired 168,217 shares of Common Stock of the Issuer as a result of the NEA 15 Distribution and, subsequent to the NEA 15 Distribution, on August 12, 2025, made a pro rata distribution of 168,217 shares of Common Stock of the Issuer to its limited partners for no consideration (the "NEA Partners 15 Distribution"). NEA 15 now holds a total of 3,045,262 shares of Common Stock of the Issuer (the "NEA 15 Shares"). On August 12, 2025, Baskett, Florence, Makhzoumi and Sandell received shares in the NEA Partners 15 Distribution (either directly or indirectly via entities or trusts for which they may be deemed to have a beneficial ownership interest), certain of which shares were sold on August 13, 2025. Schedule A attached hereto as Exhibit 2 describes all transactions in the Issuer's Common Stock that were effected during the past 60 days by the Reporting Persons. As of August 14, 2025, the Blue Mountain Trust, dated April 29, 2019 (the "Blue Mountain Trust") is the record owner of 7,910 shares of Common Stock (the "Blue Mountain Trust Shares"). As trustee of the Blue Mountain Trust, Sandell may be deemed to own beneficially the Blue Mountain Trust Shares. As of August 14, 2025, Sandell may be deemed to own beneficially the 1,094 shares of Common Stock held by the Scott Sandell Rising River Trust, dated December 20, 2012 and the 1,094 shares of Common Stock held by the Jennifer Ayer Sandell Rising River Trust, dated December 20, 2012.

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, Common Stock beneficially owned by any of the Reporting Persons.

Not applicable.