Arcellx is a clinical-stage biopharmaceutical company developing novel, adaptive and controllable cell therapies for the treatment of patients with cancer and autoimmune diseases. The Company's proprietary ARC-sparX platform separates the tumor-recognition and tumor-killing functions of conventional CAR-T cell therapies: (1) sparX (soluble protein antigen-receptor X-linkers) proteins recognize and bind specific antigens on diseased cells and flag those cells for destruction; and (2) ARC-T (Antigen Receptor Complex-T) cells bind the sparX proteins and kill the flagged cells. Arcellx has developed a collection of sparX proteins that bind different cell surface antigens. Administration of alternate sparX proteins can redirect ARC-T cells to different disease antigens to potentially address relapsed and refractory disease due to tumor heterogeneity or antigen escape. Additionally, ARC-T cell activity can be curbed as needed by controlling the dose and frequency of sparX administration.