GTx, Inc. (Nasdaq: GTXI) today announced that enobosarm achieved the pre-specified primary efficacy endpoint in the 9 mg dose cohort from patients in both stage 1 and the ongoing stage 2 of its Phase 2 clinical trial in women with advanced, estrogen receptor positive (ER+), androgen receptor positive (AR+) breast cancer. The primary efficacy endpoint requires at least nine patients (out of a total of 44 evaluable patients) to achieve clinical benefit, defined as either a complete response, partial response or stable disease, as measured by Response Evaluation Criteria in Solid Tumors (RECIST) at 24 weeks of treatment. In this ongoing trial, the efficacy endpoint was achieved in the first 22 confirmed evaluable patients, and the trial will continue enrolling and treating eligible patients with enobosarm until 44 evaluable patients have completed the trial. Enobosarm has been well tolerated among patients treated to date in the 9 mg dose cohort with the majority of adverse events being either grade 1 or 2. The Company plans to report top-line clinical results from these 22 evaluable patients from the 9 mg dose cohort in December 2016, and expects to report top-line clinical results from the full study by the middle of 2017, following completion of the clinical trial. "Demonstrating success with the 9 mg dose cohort sooner than expected in 22 patients is a significant milestone for the enobosarm program and GTx, and we look forward to seeing top-line response data in all 44 evaluable patients," said Robert J. Wills, Ph.D., Executive Chairman of GTx. "In addition, with these results in hand, we will be discussing how best to advance the development of enobosarm with potential partners." About the Phase 2 Clinical Trial in ER+/AR+ Breast Cancer The open-label, multi-center, multinational Phase 2 clinical trial (NCT02463032) will assess the efficacy and safety of orally administered enobosarm in up to 88 evaluable patients with metastatic or locally advanced, ER+/AR+ breast cancer. Patients will receive orally-administered enobosarm (9 mg or 18 mg) daily for up to 24 months. The two dose cohorts in the trial will be treated independently for the purpose of assessing efficacy. The first stage of evaluation will be assessed among the first 18 evaluable patients for each cohort. If at least 3 of 18 patients achieve clinical benefit at week 24, then the trial will proceed to the second stage of enrollment for that cohort to assess clinical benefit in a total of 44 evaluable patients per arm. As reported in September and November, 2016, respectively, patients in both the 9 mg and 18 mg cohorts demonstrated sufficient clinical benefit among the first 18 evaluable patients in each such cohort to advance to the second and final stage of the clinical trial. Clinical benefit is defined as a complete response, partial response, or stable disease, as measured by Response Evaluation Criteria in Solid Tumors (RECIST) at 24 weeks. The lead investigator for the trial is Dr. Beth Overmoyer from the Dana Farber Cancer Institute and the Harvard Medical School.