Preclinical development of a humanized chimeric antigen receptor against B cell maturation antigen for multiple myeloma.

Multiple myeloma is a prevalent and incurable disease, despite the development of new and effective drugs. The recent development of chimeric antigen receptor (CAR)-T cell therapy has shown impressive results in the treatment of patients with relapsed or refractory hematological B cell malignancies. In the recent years, B-cell maturation antigen (BCMA) has appeared as a promising antigen to target using a variety of immuno-therapy treatments including CART cells, for MM patients. To this end, we generated clinical-grade murine CART cells directed against BCMA, named ARI2m cells. Having demonstrated its efficacy, and in an attempt to avoid the immune rejection of CART cells by the patient, the single chain variable fragment was humanized, creating ARI2h cells. ARI2h cells demonstrated comparable in vitro and in vivo efficacy to ARI2m cells, and superiority in cases of high tumor burden disease. In terms of inflammatory response, ARI2h cells showed a lower TNFα production and lower in vivo toxicity profile. Large-scale expansion of both ARI2m and ARI2h cells was efficiently conducted following Good Manufacturing Practice guidelines, obtaining the target CART cell dose required for treatment of multiple myeloma patients. Moreover, we demonstrate that soluble BCMA and BCMA released in vesicles impacts on CAR-BCMA activity. In summary, this study sets the bases for the implementation of a clinical trial (EudraCT code: 2019-001472-11) to study the efficacy of ARI2h cell treatment for multiple myeloma patients.