Outcomes of Hematopoietic Stem Cell Transplantation Following the Use of Blinatumomab in Pediatric Relapsed B-Cell Acute Lymphoblastic Leukemia: A Single-Center Experience.

Background: Relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL) remains associated with poor outcomes in children. Achieving measurable residual disease (MRD) negativity prior to allogeneic hematopoietic stem cell transplantation (HSCT) is critical for durable remission. Blinatumomab, a bispecific CD19-CD3 T-cell engager, induces deep remissions with minimal myelosuppression and is increasingly utilized as a bridge to HSCT. We describe our institutional experience with HSCT following blinatumomab-induced remission in pediatric R/R B-ALL. Methods: This retrospective single-center study included five pediatric patients with R/R B-ALL who received blinatumomab bridging therapy prior to allogeneic HSCT between January 2020 and June 2025. Clinical data included demographics, prior therapies, blinatumomab dosing and duration, MRD status, conditioning regimen, donor source, stem cell dose, engraftment kinetics, donor chimerism, and complications. The endpoints included MRD clearance before HSCT, engraftment kinetics, donor chimerism, viral reactivation, bacterial infections post-transplant, and overall and failure-free survival at last follow-up. Results: All five patients completed one to two 28-day cycles of blinatumomab and achieved MRD negativity (< 0.01%) prior to HSCT. Donor sources comprised one matched sibling and four haploidentical family donors. The median interval between blinatumomab completion and HSCT was 32 days. Median neutrophil and platelet engraftment occurred on days +12 and +9, respectively. Full donor chimerism was achieved within 1 - 3 months and sustained throughout follow-up. Post-transplant complications included engraftment syndrome (n = 4), cytomegalovirus (CMV) reactivation (n = 4), Epstein-Barr virus (EBV) reactivation (n = 1), Conclusions: In this single-center experience from a low-/middle-income country (LMIC), blinatumomab served as an effective bridge to HSCT, enabling MRD-negative remissions with favorable post-transplant outcomes. Viral reactivations and steroid-refractory GVHD were reported, underlining the need for robust surveillance. Broader access to blinatumomab and prospective studies are needed to validate these findings and to evaluate cost-effectiveness in LMICs.