Patients (pts) in 6 cohorts received abemaciclib 150-200 mg every 12 hours (Q12H) with letrozole 2.5 mg/d (Part A), anastrozole 1 mg/d (Part B), tamoxifen 20 mg/d (Part C), exemestane 25 mg/d (Part D), exemestane 25 mg/d + everolimus 5 mg/d (Part E)...Combinations of abemaciclib with endocrine therapies demonstrate manageable safety and early clinical evidence of antitumor activity.