Phase II Study of GTx024 in Women With Metastatic Breast Cancer

This is an open label, multicenter study to assess the safety and efficacy of GTx-024 in female subjects who have estrogen receptor (ER) positive metastatic breast cancer and who have responded previously to hormone therapy. Subjects may have received up to 3 prior hormonal therapies for the treatment of breast cancer. Subjects must have responded to adjuvant hormonal therapy for \> 3 years or hormonal therapy for metastatic disease for \> 6 months before progression to be eligible for this study. The primary efficacy analysis will be the clinical benefit in subjects with AR positive breast cancer at 6 months as measured by a modified Response Evaluation Criteria In Solid Tumors (RECIST 1.1) classification. Key secondary endpoints of clinical benefit in all subjects and AR negative subjects, as well as objective response rate, progression free survival, time to progression, duration of response, incidence of SREs, and time to first SRE in subsets based on AR status will also be assessed.