Indexed on: 25 Jan '20Published on: 24 Jan '20Published in: Cancer Science
Adult patients with relapsed/refractory (R/R) B-precursor acute lymphoblastic leukemia (ALL) have a poor prognosis. Blinatumomab is a bispecific T-cell engager (BiTE ) immuno-oncology therapy with dual specificity for CD19 and CD3 that redirects patients' CD3-positive cytotoxic T cells to lyse malignant and normal B cells. We conducted an open-label, phase 1b/2 study to determine the safety, pharmacokinetics, efficacy, and recommended dose of blinatumomab in Japanese adults with R/R B-precursor ALL. Patients received 9 μg/day blinatumomab during week 1 and 28 μg/day during weeks 2-4 with a 2-week treatment-free interval (6-week cycle); patients received 28 μg/day blinatumomab in subsequent cycles. Primary endpoints were the incidence of dose-limiting toxicities (DLTs) in phase 1b and complete remission (CR)/CR with partial hematologic recovery (CRh) within the first 2 cycles in phase 2. Twenty-six patients enrolled and 25 (96%) reported grade ≥3 adverse events (mostly cytopenias). There were no DLTs. CR/CRh within 2 cycles was achieved by 4 of 5 patients (80%) in phase 1b and 8 of 21 patients (38%) in phase 2. Among patients with evaluable MRD, 4 (100%) in phase 1b and 3 (38%) in phase 2 had a complete MRD response. Median RFS for 8 patients who achieved CR/CRh in phase 2 was 5 (95% CI: 3.5-6.4) months; median OS was not estimable. There were no significant associations between maximum cytokine levels or percentage of specific cell types during cycle 1 and response. Consistent with global studies, blinatumomab appeared to be safe and efficacious in Japanese adults with R/R ALL. © 2020 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.