X0508 4 2026-01-02 0001786205 Arcellx, Inc. ACLX 0001789632 Heery Christopher C/O ARCELLX, INC. 800 BRIDGE PARKWAY REDWOOD CITY CA 94065 false true false false CHIEF MEDICAL OFFICER false Common Stock 2026-01-02 4 M false 13021 0 A 13615 D Common Stock 2026-01-03 4 M false 16520 0 A 30135 D Common Stock 2026-01-06 4 M false 13064 0 A 43199 D Restricted Stock Unit 2026-01-02 4 A false 67708 0 A Common Stock 67708 67708 D Restricted Stock Unit 2026-01-02 4 M false 13021 0 D Common Stock 13021 13021 D Restricted Stock Unit 2026-01-03 4 M false 16520 0 D Common Stock 16520 0 D Restricted Stock Unit 2026-01-06 4 M false 13064 0 D Common Stock 13064 39194 D Includes 284 shares acquired under the Issuer's 2022 Employee Stock Purchase Plan on May 14, 2025, and 310 shares acquired under the Issuer's 2022 Employee Stock Purchase Plan on November 14, 2024. Each restricted stock unit ("RSU") represents a contingent right to receive one share of the Issuer's Common Stock. Subject to the Reporting Person continuing to be a Service Provider (as defined in the Issuer's 2022 Equity Incentive Plan) through each applicable vesting date, one-fourth (1/4th) of the RSUs subject to the award will vest each year following the RSU Grant Date on the same day of the month as the RSU Grant Date (or, if there is no corresponding day in a particular month, then the last day of the month) over four (4) years. "RSU Grant Date" shall mean January 2, 2026. Subject to the Reporting Person continuing to be a Service Provider (as defined in the Issuer's 2022 Equity Incentive Plan) through each applicable vesting date, one-third (1/3rd) of the RSUs subject to the award will vest each year following the RSU Grant Date on the same day of the month as the RSU Grant Date (or, if there is no corresponding day in a particular month, then the last day of the month) over three (3) years. "RSU Grant Date" shall mean January 2, 2024. Subject to the Reporting Person continuing to be a Service Provider (as defined in the Issuer's 2022 Equity Incentive Plan) through each applicable vesting date, one-third (1/3rd) of the RSUs subject to the award will vest each year following the RSU Grant Date on the same day of the month as the RSU Grant Date (or, if there is no corresponding day in a particular month, then the last day of the month) over three (3) years. "RSU Grant Date" shall mean January 3, 2023. Subject to the Reporting Person continuing to be a Service Provider (as defined in the Issuer's 2022 Equity Incentive Plan) through each applicable vesting date, one-fourth (1/4th) of the RSUs subject to the award will vest each year following the RSU Grant Date on the same day of the month as the RSU Grant Date (or, if there is no corresponding day in a particular month, then the last day of the month) over four (4) years. "RSU Grant Date" shall mean January 6, 2025. /s/ Michelle Gilson, as Attorney-in-Fact 2026-01-06