Chimeric antigen receptor (CAR) T-cell therapy for multiple myeloma targeting B-cell maturation antigen (BCMA) induces high overall response rates. However, relapse still occurs and novel strategies for targeting multiple myeloma cells using CAR T-cell therapy are needed. SLAMF7 (also known as CS1) and CD38 on tumor plasma cells represent potential alternative targets for CAR T-cell therapy in multiple myeloma, but their expression on activated T cells and other hematopoietic cells raises concerns about the efficacy and safety of such treatments. Here, we used CRISPR/Cas9 deletion of the CD38 gene in T cells and developed DCAR, a double CAR system targeting CD38 and CS1 through activation and costimulation receptors, respectively. Inactivation of CD38 enhanced the anti-multiple myeloma activity of DCAR T in vitro. Edited DCAR T cells showed strong in vitro and in vivo responses specifically against target cells expressing both CD38 and CS1. Furthermore, we provide evidence that, unlike anti-CD38 CAR T-cell therapy, which elicited a rapid immune reaction against hematopoietic cells in a humanized mouse model, DCAR T cells showed no signs of toxicity. Thus, DCAR T cells could provide a safe and efficient alternative to anti-BCMA CAR T-cell therapy to treat patients with multiple myeloma.
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