A phase I trial of pan-Bcl-2 antagonist obatoclax administered as a 3-h or a 24-h infusion in combination with carboplatin and etoposide in patients with extensive-stage small cell lung cancer

BACKGROUND: Bcl-2 family genes are frequently amplified in small cell lung cancer (SCLC). A phase I trial was conducted to evaluate the safety of obatoclax, a Bcl-2 family inhibitor, given in combination with standard chemotherapy. METHODS: Eligible patients (3–6 per cohort) had extensive-stage SCLC, measurable disease, ⩽1 before therapy, Eastern Cooperative Oncology Group performance status 0 or 1, and adequate organ function. Patients were treated with escalating doses of obatoclax, either as a 3- or 24-h infusion, on days 1–3 of a 21-day cycle, in combination with carboplatin (area under the curve 5, day 1 only) and etoposide (100 mg m(−2), days 1–3). The primary endpoint was to determine the maximum tolerated dose of obatoclax. RESULTS: Twenty-five patients (56% male; median age 66 years) were enrolled in three dose cohorts for each schedule. Maximum tolerated dose was established with the 3-h infusion at 30 mg per day and was not reached with the 24-h infusion. Compared with the 24-h cohorts, the 3-h cohorts had higher incidence of central nervous system (CNS) adverse events (AEs); dose-limiting toxicities were somnolence, euphoria, and disorientation. These CNS AEs were transient, resolving shortly after the end of infusion, and without sequelae. The response rate was 81% in the 3-h and 44% in the 24-h infusion cohorts. CONCLUSION: Although associated with a higher incidence of transient CNS AEs than the 24-h infusion, 3-h obatoclax infusion combined with carboplatin–etoposide was generally well tolerated at doses of 30 mg per day. Though patient numbers were small, there was a suggestion of improved efficacy in the 3-h infusion group. Obatoclax 30 mg infused intravenously over 3 h on 3 consecutive days will be utilised in future SCLC studies.