Blinatumomab Bridging Therapy for BALL

The investigator is testing the ability of a biologically active therapy in blinatumomab, an anti-CD19/CD3 bispecific T-cell engager, to further reduce residual leukemia immediately prior to HCT to improve post-HCT outcomes. This Phase 2 study will determine the effectiveness of delivering 1 to 2 cycles of blinatumomab (Days 1-28) as bridging therapy in children, adolescent and young adults with relapse or persistent MRD B-ALL. Eligible subjects will receive 1 or 2, 28-day cycles of blinatumomab prior to proceeding to HCT. Centralized MRD assessment will be performed after completion of the 28-days of blinatumomab using both flow cytometry (University of Washington, Brent Wood, MD) and High-Throughput Deep Sequencing (HTS) MRD technologies (Adaptive Technologies, Seattle, WA). Subjects who achieve flow cytometry negative MRD (\<0.01%) after a single cycle of blinatumomab can proceed directly to HCT whereas subjects who remain MRD positive by flow cytometry may receive a 2nd cycle of blinatumomab. Subjects who remain MRD positive by flow cytometry after a 2nd cycle of blinatumomab will come off study.