Chimeric antigen receptor (CAR) T-cell therapy exhibits desirable and robust efficacy in patients with acute lymphoblastic leukemia (ALL). Stimulated by the revolutionized progress in the use of FDA-approved CD19 CAR T cells, novel agents with CAR designs and targets are being produced in pursuit of superior performance. However, on the path from bench to bedside, new challenges emerge. Accessibility is considered the initial barrier to the transformation of this patient-specific product into a commercially available product. To ensure infusion safety, profound comprehension of adverse events and proactive intervention are required. Additionally, resistance and relapse are the most critical and intractable issues in CAR T-cell therapy for ALL, thus precluding its further development. Understanding the limitations through up-to-date insights and characterizing multiple strategies will be critical to leverage CAR T-cell therapy flexibly for use in clinical situations. Herein, we provide an overview of the application of CAR T-cell therapy in ALL, emphasizing the main challenges and potential clinical strategies in an effort to promote a standardized set of treatment paradigms for ALL.

BackgroundThis study aimed to systematically evaluate and compare the efficacy and safety of consolidative hematopoietic stem cell transplantation (HSCT) after CD19 chimeric antigen receptor T (CAR-T) therapy with non-HSCT in the treatment of acute lymphoblastic leukemia (ALL).MethodsThe PubMed, Embase, Cochrane Library and Web of Science databases were searched for clinical trials. Pooled hazard ratios (HRs) for overall survival (OS), relapse rate, and leukemia-free survival (LFS) as well as overall incidence rates for transplant-related mortality (TRM), acute graft-versus-host disease (aGVHD), chronic graft-versus-host disease (cGVHD), and infections were calculated using Stata software.ResultsWe screened 3,441 studies and identified 19 eligible studies with 690 patients. Among the patients who achieved complete remission (CR) after CD19 CAR-T therapy, consolidative HSCT was beneficial for OS (HR = 0.34, 95% CI, 0.17–0.68, P = 0.003), the relapse rate (HR = 0.16, 95% CI, 0.10–0.25, P < 0.001), and LFS (HR = 0.15, 95% CI, 0.08–0.28, P < 0.001). For patients who achieved MRD-negative (neg) CR after CD19 CAR-T therapy, consolidative HSCT was beneficial for OS (0.57, 95% CI, 0.33–0.99, P = 0.045), the relapse rate (0.14, 95% CI, 0.06–0.31, P < 0.001), and LFS (0.21, 95% CI, 0.12–0.35, P < 0.001). Regarding safety, we calculated pooled incidence rates for TRM (8%, 95% CI, 0.02–0.15), aGVHD (44%, 95% CI, 0.23–0.67), cGVHD (36%, 95% CI, 0.17–0.56), and infections (39%, 95% CI, 0.03–0.83).ConclusionsCompared with non-HSCT treatment, consolidative HSCT after CD19 CAR-T therapy for R/R B-ALL patients can prolong OS and LFS and reduce the risk of relapse. The incidence rates for adverse events are acceptable. More high-quality randomized controlled trials are required to avoid bias and further determine the efficacy of HSCT.