A phase II study of obatoclax mesylate, a Bcl-2 antagonist, plus topotecan in relapsed small cell lung cancer.

Introduction: We previously reported data on the safety, tolerability, and recommended phase II dose of obatoclax mesylate in conjunction with topotecan in patients with advanced solid tumor malignancies. Preliminary efficacy data suggested activity in patients with recurrent small cell lung cancer (SCLC). Based on these data, we performed a phase II study of obatoclax mesylate plus topotecan in patients with relapsed SCLC to assess efficacy.

Methods: This was an open-label, single-arm, phase II extension of obatoclax mesylate plus topotecan in patients with relapsed SCLC. Obatoclax mesylate was given intravenously (IV) at a dose of 14mg/m(2) on days 1 and 3 with IV topotecan at 1.25mg/m(2) on days 1-5 of an every 3-week cycle. The primary end-point of this study was overall response rate.

Results: Nine patients with recurrent SCLC were enrolled into the first stage of the study. Patients received a median of 2 cycles of treatment. All patients were evaluable for the primary end-point of overall response. There were no partial or complete responses. Five patients (56%) had stable disease. The remaining four patients (44%) developed progressive disease. The most common grade 3 or 4 adverse events included thrombocytopenia (22%), anemia (11%), neutropenia (11%), and ataxia (11%).

Conclusion: Obatoclax mesylate added to topotecan does not exceed the historic response rate seen with topotecan alone in patients with relapsed SCLC following the first-line platinum-based therapy.