Blinatumomab (CD19 BiTE) sees 28% attrition after toxic UK ALLR3 re‑induction in relapsed B‑ALL

Blinatumomab, a CD19‑directed bispecific T‑cell engager, was evaluated as post‑induction or salvage therapy in the Children’s Oncology Group Phase 3 AALL1331 trial (NCT02101853), which began with a UK ALLR3-inspired four-drug Block 1 re-induction—dexamethasone, vincristine, pegylated l-asparaginase (Pegaspargase) and mitoxantrone—in 661 children, adolescents and young adults with first‑relapse B‑cell ALL. This induction regimen produced an 80.3% complete‑remission rate but left 54.5% of marrow‑involved patients MRD‑positive; chemo-induced early deaths (3.6%) and severe infections drove grade 3/4/5 adverse events in 44.9/24.1/3.6% and prevented 190 patients (28.7%) from reaching blinatumomab or transplant randomization. Contemporary immunotherapies look gentler and more effective—single‑agent blinatumomab records ~56% CR with lower grade ≥3 toxicity, while CAR‑T tisagenlecleucel delivers 81% MRD‑negative remissions with almost no induction mortality—highlighting the gap between chemo‑based re‑induction and current standards.