Efficacy & Safety Evaluation of Enobosarm in Combo With Abemaciclib in Treatment of ER+HER2- Metastatic Breast Cancer

STAGE 1: To determine the safety of enobosarm 9 milligram (mg) once daily (QD) used in combination with a CDK 4/6 inhibitor \[Verzenio® (abemaciclib) tablets, for oral use, 150 mg twice daily (BID)\]. STAGE 2: To demonstrate the efficacy and safety of enobosarm 9 mg QD in combination with abemaciclib 150 mg BID (Enobosarm Combination Group) versus Estrogen Blocking Agent (Control Treatment Group) in the treatment of estrogen receptor positive (ER+), human epidermal growth factor receptor 2 negative (HER2-), androgen receptor positive (AR+) with a AR% nuclei staining ≥40% metastatic breast cancer that have previously experienced disease progression on an estrogen blocking agent plus (palbociclib) as measured by progression free survival (PFS) according to RECIST 1.1 criteria.