Phase II study of the safety and antitumor activity of the hypoxia-activated prodrug TH-302 in combination with doxorubicin in patients with advanced soft tissue sarcoma

Abstract

Purpose: TH-302, a prodrug of the cytotoxic alkylating agent bromo-isophosphoramide mustard, is preferentially activated in hypoxic conditions. This phase II study investigated TH-302 in combination with doxorubicin, followed by single-agent TH-302 maintenance therapy in patients with first-line advanced soft tissue sarcoma (STS) to assess progression-free survival (PFS), response rate, overall survival, safety, and tolerability.

Patients and methods: In this open-label phase II study, TH-302 300 mg/m(2) was administered intravenously on days 1 and 8 with doxorubicin 75 mg/m(2) on day 1 of each 21-day cycle. After six cycles, patients with stable and/or responding disease could receive maintenance monotherapy with TH-302.

Results: Ninety-one patients initiated TH-302 plus doxorubicin induction treatment. The PFS rate at 6 months (primary efficacy measure) was 58% (95% CI, 46% to 68%). Median PFS was 6.5 months (95% CI, 5.8 to 7.7 months); median overall survival was 21.5 months (95% CI, 16.0 to 26.2 months). Best tumor responses were complete response (n = 2 [2%]) and partial response (n = 30 [34%]). During TH-302 maintenance (n = 48), five patients improved from stable disease to partial response, and one patient improved from partial to complete response. The most common adverse events during induction were fatigue, nausea, and skin and/or mucosal toxicities as well as anemia, thrombocytopenia, and neutropenia. These were less severe and less frequent during maintenance. There was no evidence of TH-302-related hepatic, renal, or cardiac toxicity.

Conclusion: PFS, overall survival, and tumor response compared favorably with historical outcomes achieved with other first-line chemotherapies for advanced STS. A phase III study of TH-302 is ongoing (NCT01440088).

Fig 1.

Kaplan-Meier plots of (A) progression-free survival on study (N = 91), (B) progression-free survival after initiating maintenance therapy (n = 48), and (C) overall survival on study (N = 91).

Fig 2.

Case study of patient with metastatic uterine leiomyosarcoma exhibiting partial response to treatment with doxorubicin plus TH-302. Comparison of computed tomography (CT) scans at baseline and at the end of four cycles of doxorubicin plus TH-302. Images provided courtesy of Fritz Eilber, MD, University of California at Los Angeles.