Efficacy and safety of blinatumomab: Post hoc pooled analysis in Asian adults with relapsed/refractory B-cell precursor acute lymphoblastic leukemia

Background: Global studies have demonstrated the efficacy and safety of blinatumomab—a BiTE^® (bispecific T-cell engager) targeted immuno-oncology therapy that mediates the lysis of cells expressing CD19 in patients with relapsed/refractory acute lymphoblastic leukemia (R/R ALL). Because limited data are available in Asian patients, we conducted a post hoc pooled analysis in 45 Asian adult patients with R/R ALL—19 from the blinatumomab arm of TOWER (NCT02013167) and 26 from Study 265, a phase 1b/2 study in Japanese adults (NCT02412306). Methods: Patients received a maximum of two cycles of induction blinatumomab for 4 weeks by continuous intravenous infusion (cycle 1/week 1: 9 μg/day; cycle 1/weeks 2–4: 28 μg/day) followed by 2 weeks of no blinatumomab (each 6-week cycle); patients received 28 μg/day blinatumomab in subsequent cycles. Results: Twenty of 45 patients enrolled (44%) achieved complete remission with full or partial hematologic recovery compared with 44% in TOWER and 80% and 38% in phase 1b and phase 2, respectively, of Study 265. The Kaplan–Meier (KM) median overall survival was 11.9 months (95% confidence interval [CI], 9.9–17.1) and the KM median duration of relapse-free survival was 8.9 months (95% CI, 3.8–10.7). Ninety-three percent of patients had grade ≥ 3 treatment-emergent adverse events (AEs) compared with 87% in TOWER and 80% and 100% in phase 1b and phase 2, respectively, of Study 265. Five patients (11.4%) had fatal AEs. Conclusions: The safety and efficacy of blinatumomab in Asian patients were comparable with those reported in previous global studies with no new safety signals.