Threshold Pharmaceuticals Provides Update on Continued Promising Data From a Phase 1/2 Clinical Trial of TH-302 at the American Society of Clinical Oncology Annual Meeting

Threshold Pharmaceuticals, Inc. THLD today announced clinical trial results related to Threshold's clinical stage hypoxia-activated prodrug, TH-302. The results were presented at the American Society of Clinical Oncology Annual Meeting in Chicago. The presentation summarized the Phase 2 experience from the ongoing single arm Phase 1/2 clinical trial, the 403 trial, which is investigating TH-302 in combination with doxorubicin in patients with soft tissue sarcoma. The Phase 2 analysis included patients with first-line soft tissue sarcoma (adjuvant and neoadjuvant therapy accepted) treated at the TH-302 maximum tolerated dose of 300 mg/m2 in combination with 75 mg/m2 doxorubicin. Sixty-two patients were included in the analyses including 60 patients with at least one evaluable post-treatment tumor assessment. Best responses were: 1 complete response, 18 partial responses and 32 patients with stable disease for an overall response rate of 32% and a stable disease or better rate of 85%. In addition to the reported response rates, median progression free survival was 6.4 months (95% confidence interval: 5.6 to 8.1 months). Six of the 60 patients continue on study after a median of 15 cycles. The median overall survival was 16.1 months (95% CI: 10.4 months to not reached). With the agreement in February with the U.S. Food and Drug Administration on a Special Protocol Assessment, the Company plans to initiate a Phase 3, randomized, controlled clinical trial comparing TH-302 in combination with doxorubicin with doxorubicin alone with a primary efficacy endpoint of overall survival. "The phase 2 study of TH-302 in combination with standard doxorubicin in soft tissue sarcoma patients provides a robust database supporting a pivotal phase 3 trial," said Lee Cranmer, M.D., Ph.D, Arizona Cancer Center, and a clinical investigator for the trial. "The data indicate improved efficacy over conventional doxorubicin, with excellent tolerability. This has the potential to establish a new standard-of-care for the treatment of soft tissue sarcomas. More broadly, the planned phase 3 trial could provide additional proof-of-principle regarding the use of tumor hypoxia as a cancer therapy target."