X0508 4 2026-02-17 0001786205 Arcellx, Inc. ACLX 0001930862 Gilson Michelle C/O ARCELLX, INC. 800 BRIDGE PARKWAY REDWOOD CITY CA 94065 false true false false CHIEF FINANCIAL OFFICER false Common Stock 2026-01-02 4 M false 20496 0 A 28962 D Common Stock 2026-02-17 4 S false 7141 69.2103 D 57691 D Common Stock 2026-02-17 4 S false 4150 70.0125 D 53541 D Each restricted stock unit ("RSU") represents a contingent right to receive one share of the Issuer's Common Stock. Vesting of these RSUs previously reported in the Form 4 filed January 2, 2026. Represents a broker-assisted sale to satisfy the Reporting Person's tax withholding obligations in connection with the vesting of restricted stock units. Represents the weighted average share price of an aggregate total of 7,141 shares sold in the price range of $68.69 to $69.68 by the Reporting Person. The Reporting Person undertakes to provide upon request by the Commission staff, the issuer or a security holder of the issuer, full information regarding the number of shares sold at each separate price. Represents the weighted average share price of an aggregate total of 4,150 shares sold in the price range of $69.69 to $70.55 by the Reporting Person. The Reporting Person undertakes to provide upon request by the Commission staff, the issuer or a security holder of the issuer, full information regarding the number of shares sold at each separate price. /s/ Michelle Gilson 2026-02-18