Pre-transplant blinatumomab improves outcomes in B-cell acute lymphoblastic leukemia patients who undergo allogeneic hematopoietic cell transplantation

Background Blinatumomab, a bispecific monoclonal antibody, effectively controls refractory B-cell acute lymphoblastic leukemia (ALL) and promotes measurable residual disease (MRD) negativity. This study investigated the impact of pre-transplant blinatumomab on allogeneic hematopoietic cell transplantation (HCT) outcomes in B-cell ALL patients. Methods We analyzed the effect of pre-transplant blinatumomab on transplant outcomes of 117 adults undergoing allogeneic HCT for B-cell ALL at Princess Margaret Hospital, Toronto, between 2010 and 2021. Outcomes assessed included overall survival (OS), graft-vs-host disease and relapse-free survival (GRFS), cumulative incidences of relapse (CIR), and non-relapse mortality (NRM). Results The median follow-up was 36 months. Thirty-one participants (26.5%) received blinatumomab. Blinatumomab group had higher proportions of individuals with high disease risk index, primary induction failure and was more likely to receive dual T-cell depletion with anti-thymocyte globulin and post-transplant cyclophosphamide. Two-year OS, GRFS, NRM, and CIR in the blinatumomab and non-blinatumomab groups were, respectively: 65.4% vs. 45.6% (P=0.05), 42.2% vs. 17.3% (P=0.01), 3.2% vs. 43.0% (P=0.007) and 34.4% vs. 14.4% (P=0.02). Blinatumomab was associated with a lower incidence of day-100 grade 2-4 and grade 3-4 acute graft-vs-host disease (aGVHD): 27.5% vs. 56.7% (P=0.009], and 10.9% vs. 34.7% (P=0.04), respectively. Multivariate analysis confirmed the association between pre-transplant blinatumomab and improved OS and NRM. Conclusions Pre-transplant blinatumomab is associated with improved OS and lower risk of NRM in B-cell ALL patients undergoing allogeneic HCT, likely reflecting lower burden of treatment-related toxicity in this population. Larger prospective trials are warranted to validate our findings.