Immune reconstitution and clinical outcomes in B-ALL patients with versus without pre-HSCT Immunotherapy

Relapsed or refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL) continues to have a relatively high treatment-failure rate, and patients with high-risk relapse often require HSCT to achieve durable remission [ 1 , 2 ]. Although HSCT offers curative potential, post-HSCT relapse and transplant-related complications continue to limit long-term survival [ 2 ]. Immunotherapy has emerged as a novel treatment approach and has improved outcomes in patients with R/R B-ALL [ 3 , 4 , 5 ]. CD19-directed CAR-T therapy can induce deep minimal residual disease–negative remissions and has become an effective bridge to HSCT in children and young adults with B-ALL [ 3 ]. Antibody-based immunotherapies, including blinatumomab and inotuzumab ozogamicin, have likewise demonstrated substantial antileukemic activity and have enabled many heavily pretreated patients to proceed to HSCT [ 4 , 5 ]. As a result, disease control before HSCT is increasingly achieved with immunotherapy rather than chemotherapy alone in patients with high-risk or R/R disease.