Impact of Previous Allogeneic Hematopoietic Stem Cell Transplantation on Chimeric Antigen Receptor (CAR) T Cell Treatment for Relapsed/Refractory Multiple Myeloma

Background Anti-BCMA-directed chimeric antigen receptor (CAR) T cells are effective treatment for patients with refractory/relapsed multiple myeloma (RRMM). However, little is known about the impact of previous allogeneic hematopoietic stem cell transplantation (allo-HSCT) on lymphocyte collection for production of CAR T cells and subsequent treatment with CAR T cells. Patients and Methods We performed a retrospective analysis of cellular composition of lymphocyte collections, CAR T cell expansion and treatment outcomes of RRMM patients undergoing therapy with idecabtagene vicleucel (ide-cel) with and without history of allo-HSCT.27 patients (11/27 female) with median age 63 (range 39-75) years were analyzed. Five patients (19%) had the history of allo-HSCT median of 5.5 years before ide-cel. Results Prior to apheresis, the white blood cell, absolute lymphocyte counts, CD3+ cells and monocytes did not differ in patients with and without prior allo-HSCT. We also noticed no differences in the collected CD3+ yields or cellular compositions of lymphocyte collections.One year after ide-cel infusion, the progression-free survival and overall survival of patients with and without previous allo-HSCT did not differ with 60% and 45% respectively (p=.58) and 66.7% and 74% respectively (p=.84).The highest expansion of CAR T was detected between day 7 after infusion and showed no difference regarding previous allo-HSCT (p=.71).No graft-versus-host disease during the follow-up was detected. Conclusion Our data confirm that the treatment with ide-cel is feasible for patients with prior allo-HSCT. Furthermore, allo-HSCT did not influence cellular composition of lymphocyte collections, clinical outcome or in vivo expansion of ide-cel. Micro Abstract Anti-BCMA-directed chimeric antigen receptor (CAR) T cells are effective treatment for patients with refractory/relapsed multiple myeloma (RRMM). The experience regarding the impact of previous allogeneic hematopoietic stem cell transplantation (allo-HSCT) on treatment with CAR T is limited.We reported about impact of previous allo-HSCT on cellular composition of lymphocyte collections, CAR T expansion and treatment outcomes of patients with RRMM undergoing treatment with idecabtagene-autoleucel (ide-cel).The treatment with ide-cel is feasible in patients with history of allo-HSCT. We noticed no negative impact of allo-HSCT on cellular composition or outcomes of the patients.