A Randomized Phase 3 Trial of Blinatumomab Vs. Chemotherapy As Post-Reinduction Therapy in High and Intermediate Risk (HR/IR) First Relapse of B-Acute Lymphoblastic Leukemia (B-ALL) in Children and Adolescents/Young Adults (AYAs) Demonstrates Superior Efficacy and Tolerability of Blinatumomab: A Report from Children's Oncology Group Study AALL1331

First relapse of B-ALL in children and AYAs is a vexing clinical problem with high rates of subsequent relapse and death using conventional treatment approaches. This is especially true in patients with early relapse [high risk (HR), defined as marrow relapse A total of 208 HR/IR patients were randomized (Arm A: 103, Arm B: 105). Baseline characteristics were comparable between arms (Table 1). With median follow up of 1.4 years, the intent-to-treat (ITT) 2-year DFS (% ± standard error) was 41.0 ± 6.2% for Arm A vs. 59.3 ± 5.4% for Arm B (p=0.05, 1-sided per pre-specified statistical plan)(Figure 1A). The ITT 2-year OS was 59.2 ± 6.0% for Arm A vs. 79.4 ± 4.5% for Arm B (p=0.005, 1-sided)(Figure 1B). Among patients with detectable MRD (≥0.01%) at the completion of Block 1 chemotherapy, the proportion that achieved undetectable MRD ( In conclusion, for children and AYA patients with HR/IR first relapse of B-ALL, blinatumomab is superior to standard chemotherapy as post-reinduction consolidation prior to HSCT, resulting in fewer and less severe toxicities, higher rates of MRD response, greater likelihood of proceeding to HSCT and improved disease-free and overall survival. Patients remain in follow up, and prospectively defined analyses of longer-term outcomes will be forthcoming. Disclosures Brown: Jazz: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Borowitz:Beckman Coulter: Honoraria. Raetz:Pfizer: Research Funding. Zugmaier:Amgen: Employment, Other: holds stock, Patents & Royalties: & other intellectual property. Gore:Amgen: Consultancy, Equity Ownership, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel expenses; Novartis: Consultancy, Other: Service on Data Safety Monitoring Committee; travel, accommodations, expenses; Roche/Genentech: Consultancy, Honoraria, Other: travel expenses; Anchiano: Equity Ownership, Other: spouse employment and company leadership; Blueprint Medicines: Equity Ownership; Celgene: Equity Ownership, Other: DSMC member; Clovis: Equity Ownership; Mirati: Equity Ownership; Sanofi Paris: Equity Ownership. Pulsipher:Medac: Honoraria; Miltenyi: Research Funding; Bellicum: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz: Other: Education for employees; Adaptive: Membership on an entity's Board of Directors or advisory committees, Research Funding; CSL Behring: Membership on an entity's Board of Directors or advisory committees; Amgen: Other: Lecture. Hunger:Amgen: Consultancy, Equity Ownership; Bristol Myers Squibb: Consultancy; Jazz: Honoraria; Novartis: Consultancy. Loh:Medisix Therapeutics, Inc.: Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: Investigational use of blinatumomab