Ofatumumab combined with chlorambucil for previously untreated chronic lymphocytic leukemia: a phase I/II, open-label study in Japan.

Elderly/comorbid patients with chronic lymphocytic leukemia (CLL) require low-toxicity treatments. Internationally, the standard treatment for such patients is chlorambucil and an anti-CD20 therapy; however, chlorambucil is not approved in Japan. The aim of the present study was to evaluate the safety, efficacy and pharmacokinetics of ofatumumab in combination with chlorambucil in Japanese patients with previously untreated CLL who were inappropriate for fludarabine-based therapy. Ten patients were enrolled and treated in this study, all of whom received at least one dose of the study drugs. The tolerability of the treatment was confirmed initially with three patients. The overall response rate was 50%, as determined by the Independent Review Committee (IRC) with computerized tomography. All patients were alive at follow-up, and only one patient had progressive disease. The most common treatment-related adverse events (AEs) were thrombocytopenia (n = 10), neutropenia (n = 9) and rash (n = 6). One grade 3 serious AE related to the study drug occurred (hypoxia). The results indicate that ofatumumab combined with chlorambucil is an effective treatment for Japanese CLL patients, with a manageable safety profile.