A phase 3 trial of Threshold Pharma’s (THLD) hypoxia-targeting therapeutic, TH-302, in soft-tissue sarcoma will continue as planned following an interim analysis of the ongoing study. The company (and investors) will remain blinded to the data, but final results from the study are due in the second half of next year.
The interim analysis was conducted after 256 deaths in the study – final analysis requires 434. The company now expects to hit this threshold and release topline results in the “latter half of 2015.” Previous guidance was for topline results at mid-2015.
The interim efficacy analysis was designed to allow for early termination of the study if a pre-specified improvement in overall survival was met; if the Independent Data Monitoring Committee determined that the study was unlikely to meet its primary endpoint; or if safety were an issue. An early efficacy stop, according to CEO Barry Selick, would have required a hazard ratio of 0.69 or less (a 45% improvement in overall survival). Next year, THLD is looking for an HR of less than 0.825 (a 21% improvement in OS) at final analysis. Clearly, the 0.69 threshold for an early efficacy stop was a high hurdle.
The study is a randomized pivotal phase 3 clinical trial being conducted under a Special Protocol Assessment (SPA) agreement with the FDA. The trial is designed to investigate the efficacy and safety of TH-302 in combination with doxorubicin compared to doxorubicin alone, in first-line patients with metastatic STS. Overall survival is the trial’s primary endpoint.
