A phase I study of the safety and pharmacokinetics of the hypoxia-activated prodrug TH-302 in combination with doxorubicin in patients with advanced soft tissue sarcoma.

Purpose: The purpose of this study was to determine the dose-limiting toxicities (DLT), maximum tolerated dose (MTD), safety, pharmacokinetics and preliminary activity of TH-302, a hypoxia-activated prodrug, in combination with doxorubicin in patients with advanced soft tissue sarcoma.

Patients And Methods: TH-302 was administered intravenously on days 1 and 8 and doxorubicin 75 mg/m² on day 1 (2 h after TH-302) of every 3-week cycle. TH-302 starting dose was 240 mg/m² with a classic 3 + 3 dose escalation. Pharmacokinetics were assessed on days 1 and 8 of cycle 1. Tumor assessments were performed after every second cycle.

Results: Sixteen patients enrolled. Prophylactic growth factor support was added due to grade 4 neutropenia. The MTD was 300 mg/m². DLTs at 340 mg/m² were neutropenia-associated infection and grade 4 thrombocytopenia. Common adverse events included fatigue, nausea and skin rash. There was no evidence of pharmacokinetic interaction between TH-302 and doxorubicin. Five of 15 (33%) evaluable patients had a partial response by RECIST (Response Evaluation Criteria in Solid Tumors) criteria.

Conclusions: The hematologic toxicity of doxorubicin is increased when combined with TH-302. This can be mitigated by prophylactic growth factor support. Toxicities were manageable and there was evidence of antitumor activity.