Safety and Efficacy of Blinatumomab in Japanese Adult and Pediatric Patients with Relapsed/Refractory B-Cell Precursor Acute Lymphoblastic Leukemia: Final Results from an Expansion Cohort

Introduction: The safety and efficacy of blinatumomab, a CD19/CD3 bispecific T-cell engager (BiTE®) molecule, was evaluated in an expansion cohort of the phase 1b/2 study (NCT02412306) in Japanese adult (n = 14) and pediatric (n = 17) patients with relapsed/refractory Philadelphia-negative B-cell precursor (BCP) acute lymphoblastic leukemia (ALL). Materials and methods: Globally recommended blinatumomab doses were administered to adult (9-28 μg/day) and pediatric (5-15 μg/m2/day) patients. Primary endpoint was the incidence of treatment-emergent adverse events (TEAEs) and treatment-related AEs. Results: All adult and pediatric patients experienced ≥1 TEAE. Grade ≥3 TEAEs were observed in 11 (79%) adult and 15 (88%) pediatric patients. Blinatumomab was discontinued in 1 (6%) pediatric patient due to treatment-related grade 4 cytokine release syndrome. Fatal AEs such as disease progression and multiple-organ dysfunction syndrome, which were not treatment-related, were reported in 2 (12%) pediatric patients. Eleven (79%) adults achieved complete remission (CR)/CR with partial hematological recovery (CRh) within the first two blinatumomab cycles. Nine of 10 adult patients with CR/CRh and evaluable minimal residual disease (MRD) achieved MRD response. CR/CRh was achieved by 5 (29%) pediatric patients, of which two had MRD response. Conclusion: In conclusion, blinatumomab was safe and efficacious in Japanese patients with relapsed/refractory BCP ALL.