[Allogeneic CAR-T for treatment of relapsed and/or refractory multiple myeloma: four cases report and literatures review].

Objective To investigate the safety and efficacy of allogeneic CAR-T cells in the treatment of relapsed/refractory multiple myeloma (RRMM) . Methods CAR-T cells were prepared from peripheral blood lymphocytes of HLA mismatch healthy donors. Median age was 55 (48-60) . Allogeneic cells were derived from 3 HLA haploidentical donors and 1 HLA completely mismatch unrelated donor. Four patients with RRMM were conditioned with FC regimen followed by CAR-T cell transfusion. They were infused into CART-19 (1×107/kg on day 0) and (4.0-6.8) ×107/kg CART-BCMA cells as split-dose infusions (40% on day 1 and 60% on day 2) . The adverse reactions and clinical efficacy were observed during follow-up after infusion, and the amplification and duration of CAR-T cells in vivo were monitored by PCR technique. Results CAR-T cells were successfully infused in 3 of the 4 RRMM patients according to the study plan, and the infusion in one patient was delayed by 1 day due to high fever and elevated creatinine levels on day 3. The side effects included hematological and non-hematological toxicity, grade 3 hematological toxicity in 2 patients, grade 3 CRS in 1 one, grade 1 CRES in 1 one, prolonged APTT in 3 ones, tumor lysis syndrome in 1 one, mixed chimerism detected STR and clinical GVHD manifestation in 1 one. According to the efficacy criterias of IMWG, 2 patients acquired PR, 1 MR, and 1 SD respectively. Progression-free survival was 4 (3-5) weeks and overall survival was 63 (3-81) weeks. CAR T cells were amplified 2.2 (2-14) times in the patients with a median survival time of 10 (8-36) days. Conclusions Small sample studies suggested that GVHD may be present in the treatment of RRMM with allogeneic CAR-T cells. There were early clinical transient events after transfusion. Low amplification and short duration of CAR-T cells in vivo may be the main factors affecting the efficacy. Key words: Multiple myeloma; Relapsed and/or refractory; Chimeric antigen receptor T cell immunotherapy