BCMA-CAR Therapy for Multiple Myeloma in NOG Mice Prevents the Progression of Anemia and Bone Lesions.

Multiple myeloma (MM) is an incurable hematological malignancy of plasma cells. Myeloma cells interfere with hematopoietic activities of the bone marrow, often leading to anemia, and can cause the bones to develop osteoporotic and lytic lesions. Clinical experience with chimeric antigen receptor T-cell (CAR-T) therapy targeting B-cell maturation antigen (BCMA) has been promising, with good response rates, favorable safety profiles, and low incidences of severe cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome. However, CAR-T therapy in MM is accompanied by several new challenges, including therapeutic failure and relapse, and much attention has been paid to the further development of B-cell maturation antigen-chimeric antigen receptor (BCMA-CAR). Although most of the reported benefits of BCMA-CAR have been discussed, whether cancer can be eliminated, as well as the efficacy of CAR-T therapy for anemia and bone lesions, both myeloma-defining events, have not yet been reported in any animal model. In this study, we designed and verified a novel BCMA-specific chimeric antigen receptor (CAR). Our BCMA-CAR demonstrated the fundamental properties of CAR-T cells, including target-specific cytotoxic activity, cytokine production, and antitumor effects. In addition, we evaluated the therapeutic effect of BCMA-CAR in mice by imaging bone lesions and conducting blood examinations. Tumor mouse models showed systemic progression of MM in the bone marrow, and mice treated with saline or nongene modified T cells showed continued tumor progression, progressive bone lesions, and prolonged anemia. In contrast, all mice treated with gene modified T cells achieved a complete response, improved anemia to the level observed in normal mice, and suppressed progression of bone lesions. We concluded that anemia was improved with BCMA-CAR-T cell therapy. However, novel strategies to support the recovery of bone lesions by enhancing CAR-T cell function must be developed.