Phase I study of obinutuzumab ( GA 101) in J apanese patients with relapsed or refractory B ‐cell non‐ H odgkin lymphoma

As CD 20 has become an established target for treating B ‐cell malignancies, there is interest in developing anti‐ CD 20 antibodies with different functional activity from rituximab that might translate into improved efficacy. Obinutuzumab ( GA 101) is a glycoengineered, humanized type II anti‐ CD 20 monoclonal antibody that has demonstrated superior activity to type I antibodies in preclinical studies and is currently being investigated in phase III trials. In this phase I dose‐escalating study in Japanese patients with relapsed/refractory B ‐cell non‐ H odgkin lymphoma, the primary endpoint was to characterize the safety of GA 101; secondary endpoints were efficacy, pharmacokinetics and pharmacodynamics. Patients received up to nine doses of GA 101 with up to 52 weeks' follow up. Most adverse events were grade 1 or 2 infusion‐related reactions, and 10 grade 3/4 adverse events occurred. No dose‐limiting toxicities were observed and the maximum tolerated dose was not identified. Out of 12 patients, 7 responded (end‐of‐treatment response rate 58%), with 2 complete responses and 5 partial responses. Responses were observed from low to high doses, and no dose‐efficacy relationship was observed. B‐cell depletion occurred in all patients after the first infusion and was maintained for the duration of treatment. Serum levels of GA 101 increased in a dose‐dependent fashion, although there was inter‐patient variability. This phase I study demonstrated that GA 101 has an acceptable safety profile and offers encouraging activity to J apanese patients with relapsed/refractory B ‐cell non‐ H odgkin lymphoma. ( Cancer Sci 2013; 104: 105–110)