CD7 Chimeric Antigen Receptor T-Cell Therapy Bridging to Allogeneic Hematopoietic Stem Cell Transplantation Remarkably Improved Long-Term Disease-Free Survival in Refractory/Relapsed T-Cell Acute Lymphoblastic Leukemia/Lymphoma

Introduction: The prognosis of refractory/relapsed T-cell acute lymphoblastic leukemia/lymphoma (r/r T-ALL/LBL) is poor, and salvaged allogeneic hematopoietic stem cell transplantation (allo-HSCT) can only result in 20%-30% disease-free survival (DFS). Our previous clinical trials have shown that the patients with r/r T-ALL have achieved 90% complete remission (CR) with CD7 chimeric antigen receptor T cell (CART) therapy (Pan J. et al. JCO 2021), then quick received allo-HSCT to obtain 57% of 1-year DFS in 12 patients (Li ZH. et al. Transplantation and Cellular Therapy 2022). Objectives : In current study, the long-term outcomes of allo-HSCT in r/r T-ALL/LBL after CD7 CART therapy in larger cohort are investigated, and compared with that chemotherapy only before allo-HSCT simultaneously. The risk factors for prognosis after allo-HSCT in this setting are also analyzed. Methods: Between February 2018 and January 2023, total 90 patients with r/r T-ALL/LBL who underwent allo-HSCT in our hospital were included. The median age was 14 (2-65) years old. Somatic and germline gene mutations were detected by sequencing pre-transplant. Thirty-two (35.6%) patients were sensitive to chemotherapy and achieved CR before transplant (group A), and 58 (64.4%) cases were resistant to chemotherapy and in non-remission (NR) pre-HSCT. Forty-one of 58 patients in NR received CD7 CART before allo-HSCT (group B) and the rest 17 patients in NR underwent salvaged transplant (group C). Donor types included haploidential (60, 66.7%), unrelated (16, 17.8%) and identical sibling (14, 15.6%). Myeloablative conditioning regimens with either total body irradiation (TBI)/fludarabine (51, 56.7%) based or busulfan/fludarabine (39, 43.3%) based were applied. Antithymocyte globulin was used for haploidentical and unrelated transplants. Cyclosporine, mycophenolate mofetil and short-term methotrexate were employed for graft-versus-host disease (GVHD) prophylaxis. Results: All patients achieved durable engraftment. No significant difference was found in the incidences of acute GVHD (aGVHD), chronic GVHD (cGVHD) and infections in 3 groups (p=0.612, p=0.091, p=0.649). With a median follow-up of 25.5 (19.6-32) months, 2-year overall survival (OS) in group B was similar to that in group A (54.4% vs. 69.9%, p=0.33) and much higher than that in group C (35.3%, p=0.0065), and 2-year DFS in group B was similar to that in group A (51.0% vs. 61.1%, p=0.24) and much higher than that in group C (17.6%, p=0.002