Exhibit 99.1 Arcellx Provides First Quarter 2024 Financial Results REDWOOD CITY, Calif., May 9, 2024 (BUSINESS WIRE) — Arcellx, Inc. (NASDAQ: ACLX), a biotechnology company reimagining cell therapy through the development of innovative immunotherapies for patients with cancer and other incurable diseases, today reported business highlights and financial results for the first quarter ended March 31, 2024. First Quarter 2024 Financial Highlights Cash, cash equivalents, and marketable securities: As of March 3 ...