B cell maturation antigen-specific chimeric antigen receptor T cells for relapsed or refractory multiple myeloma: A meta-analysis

Introduction Chimeric antigen receptor (CAR) T cells targeting B cell maturation antigen (BCMA) have shown impressive results in clinical studies for relapsed/refractory multiple myeloma (RRMM). We performed a systematic literature review to summarize the current body of evidence on the role of anti-BCMA CAR T cells for RRMM. Objectives and Methods Fifteen studies comprising a total of 285 patients with heavily pretreated RRMM were included using a conventional meta-analysis. Main efficacy outcomes were response, relapse, and survival. Safety outcomes were cytokine release syndrome (CRS) and neurotoxicity. Results Anti-BCMA CAR T cells resulted in a pooled overall response of 82% (95% confidence interval [CI], 74%-88%) and complete response of 36% (24%-50%). Higher CAR(+) cell doses were associated with higher response rates. The pooled relapse rate of responders was 45% (27%-64%), and median progression-free survival was 10 months. Present extramedullary disease did not show worse outcome. Severe CRS grades 3-4 and neurotoxicity occurred in 15% (10%-23%) and 18% (10%-31%). Conclusion Anti-BCMA CAR T cells showed high response rates, even in patients with present extramedullary disease, while relapse occurred in half of the patients who achieved a response. Larger studies with longer follow-up especially evaluating the association of response and survival are needed.