Abstract
Objective: To observe the efficacy and safety of humanized anti-BCMA chimeric antigen receptor modified (BCMA CAR) -T cell therapy after disease progression with their murine BCMA CAR-T cell therapy in patients with relapsed/refractory multiple myeloma (MM) . Methods: Study participants underwent leukapheresis to collect T cells for BCMA CAR-T manufacturing. Patients were pretreated with intensive chemotherapy (fludarabine combined with cytarabine) before CAR-T therapy. Adverse events (AEs) , CAR DNA expansion, and cytokine were monitored. In vitro, transfection efficacy, specific cytotoxicity, and inflammatory response were detected when co-cultured with effector and target cells. Results: Patient (PT) 1 and 2 achieved complete remission (CR) and disease stability at 3 months post murine CAR-T therapy. However, 16 and 18 months later, they experienced progression of disease (PD) , and patient 1 presented with extramedullary disease at PD. Both of the patients received humanized CAR-T therapy and achieved partial remission (PR) and very good partial remission (VGPR) post humanized CAR-T therapy. PT1 achieved CR of the soft tissue masses at 4 months post humanized CAR-T therapy. Notably, the median peak of the BCMA CAR-T cells, copy of BCMA CAR gene, persistence of BCMA CAR-T, and the peak levels of IL-6, IL-8, IL-10, IFN-γ and TNF-α were higher in humanized CAR-T therapy than those in the murine CAR-T therapy. During the murine CAR-T therapy, both of the patients experienced grade 1 CRS and no ICANS. PT1 experienced grade 3 CRS and grade 2 ICANS during humanized CAR-T therapy, which were relieved by supportive care. Grade 2 CRS was observed for patient 2 during humanized CAR-T therapy. Humanized BCMA CAR-T cells showed a higher inflammatory response and in vitro cytotoxicity than that of murine BCMA CAR-T cells with effector/targets cells at 1∶1 over 48 hours (P<0.001) . The proportions of residual cells in humanized BCMA CAR-T and murine CAR-T were (17.38±5.18) % vs (28.27±4.58) %, (13.25±1.62) % vs (22.77±1.77) % for PT1 and PT2, respectively. Conclusions: The humanized BCMA CAR-T cell therapy was efficient and safe for patients who experienced progression of disease after the murine CAR-T therapy, especially for patients with extramedullary disease.