Peripheral blood immune cell profiling and response to BCMA CAR-T cell therapy in relapsed refractory multiple myeloma

Chimeric antigen receptor T cell (CAR-T) therapy has revolutionized the treatment of relapsed/refractory multiple myeloma (RRMM) [ 1 , 2 ]. Although BCMA CAR-T cell therapy induces deep and durable responses in most patients with RRMM, disease progression ultimately occurs in most cases. Studies in B-cell acute lymphoblastic leukemia and non-Hodgkin lymphoma have demonstrated that distinct CAR-T cell subsets exhibit differential functions in antitumor efficacy and toxicity profiles [ 3 , 4 ]. Peripheral blood and bone marrow immune profiling of multiple myeloma (MM) patients treated with CAR-T cell therapy and bispecific T-cell engagers has revealed enrichment of CD4+ T cells and memory T-cell populations, along with elevated CD4+ /CD8+ ratios, in treatment responders compared to non-responders [ 5 ]. The association between pre-treatment circulating immune cell populations and therapeutic efficacy of BCMA CAR-T-cell therapy in RRMM remains inadequately characterized.