Up-front blinatumomab improves MRD clearance and outcome in adult Ph– B-lineage ALL: the GIMEMA LAL2317 phase 2 study

The Gruppo Italiano Malattie EMatologiche dell'Adulto (GIMEMA) Leucemia Acuta Linfoblastica (LAL) 2317 protocol investigated the frontline chemotherapy-blinatumomab combination in adult Philadelphia chromosome/BCR::ABL1 rearrangement-negative (Ph-) CD19+ B-lineage acute lymphoblastic leukemia (B-ALL) to improve minimal residual disease (MRD) response and clinical outcome. Two cycles of IV blinatumomab were administered after chemotherapy cycles 3 and 6. The primary end point was the rate of molecular MRD negativity after blinatumomab 1. One hundred forty-nine patients were enrolled (median age, 41 years [range, 18-65]); 132 entered remission, 122 received blinatumomab, and 109 had a pre- and post-blinatumomab 1 MRD assessment. MRD negativity increased from 72% to 93% (P < .001) after blinatumomab, with 23 of 30 MRD-positive patients (73%) becoming MRD negative, fulfilling the primary end point. At a median follow-up of 38.1 months (range, 0.5-62.8), the median overall survival (OS) and disease-free survival (DFS) were not reached, and the estimated 3-year OS and DFS were 71% and 65%, respectively, with an excellent outlook for the patients aged 18 to 40 years who achieved an early MRD negativity (DFS, 92%). Pre-blinatumomab MRD predicted a worse outcome, especially in genetically high-risk patients. Notably, the 3-year survival of blinatumomab-treated patients was 82%. Survival and relapse rates were 91% and 15% in patients assigned to standard chemotherapy, 59% and 35% in patients assigned to hematopoietic stem cell transplantation, and 69% and 19% in transplant recipients, respectively. Blinatumomab toxicity was manageable, with only 8 permanent discontinuations. This chemotherapy-blinatumomab risk-oriented program yielded remarkable results that need further improvement in higher-risk patients displaying early MRD persistence. Blinatumomab should be considered as a standard component of induction/consolidation for adult Ph- B-ALL. This trial was registered at www.ClinicalTrials.gov as #NCT03367299.