GTx, Inc. announced positive results from a Phase 2, proof-of-concept, open-label clinical study evaluating enobosarm, a selective androgen receptor modulator, for the treatment of patients with androgen receptor positive and estrogen receptorpositive metastatic breast cancer who have previously responded to hormonal therapy. The clinical data is being presented today during the Breast Cancer-HER2/ER poster session at the 50th Annual Meeting of the American Society of Clinical Oncolog in Chicago. The Phase 2 open-label study is evaluating 22 postmenopausal women with ER positive metastatic breast cancer, who had previously responded to adjuvant hormonal therapy for three years or longer, and women diagnosed with metastatic disease, who had been treated with hormonal therapy for at least six months, prior to disease progression. Study participants were heavily pretreated. The mean time from initial breast cancer diagnosis is 11 years and the mean age of patients is 64 years. Of the 22 patients enrolled in the study, a total of 20 patients had one or more scheduled assessments for determination of clinical benefit. The primary endpoint was assessed in 17 AR+ patients with 6 patients demonstrating clinical benefit at six months, exceeding the pre-defined statistical threshold requiring that at least 3 of 14 patients with an AR+ metastatic lesion demonstrate clinical benefit. Additionally, results showed that, after a median duration on study of 81 days, 41 percent of all patients achieved clinical benefit as best response and also had increased prostate specific antigen, which appears to be an indicator of AR activity.