Anti-CD19 chimeric antigen receptor-modified T-cell therapy bridging to allogeneic hematopoietic stem cell transplantation for relapsed/refractory B-cell acute lymphoblastic leukemia: An open-label pragmatic clinical trial.

Chimeric antigen receptor-modified T-cell (CAR-T) therapy is effective and safe for patients with relapsed/refractory B-cell acute lymphoblastic leukemia (r/r B-ALL), but its value has been limited in terms of long-term leukemia-free survival. New strategies that can help CAR-T therapy achieve lasting effect are urgently warranted. This non-randomized interventional pragmatic clinical trial had a particular aim. It explored whether consolidative allogeneic hematopoietic stem cell transplantation (allo-HSCT) could improve the long-term prognosis of the minimal residual disease-negative complete remission (MRD- CR) patients after CAR-T therapy. In the first stage, 58 r/r B-ALL patients received split doses of CAR-T cells after lymphodepleting chemotherapy, and 51 (87.9%) achieved CR. In the second stage, 21/47 MRD- CR patients without previous allo-HSCT and contraindications or other restrictions, on their own accord, received consolidative allo-HSCT within three months after CAR-T therapy. There was no difference in overall survival (OS) between the MRD- CR patients who received allo-HSCT and those who did not. However, event-free survival (EFS) and relapse-free survival (RFS) were significantly prolonged by allo-HSCT in the subgroups. This was with either high (≥5%) pre-infusion bone marrow MRD assessed by flow cytometry (BM-FCM-MRD) or poor prognostic markers (P < .05). However, no difference was found in EFS and RFS for patients with pre-infusion BM-FCM-MRD <5% and without poor prognostic markers (P > .05). To conclude, CAR-T therapy bridging to allo-HSCT is a safe and effective therapeutic strategy for r/r B-ALL patients, and may prolong their EFS and RFS, especially when they have high pre-infusion BM-FCM-MRD or poor prognostic markers.