Supplementary Material for: 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

Background The safety and efficacy of blinatumomab, a CD19/CD3 BiTE® (bispecific T-cell engager) 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). 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 one (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 two (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 five (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.