A Study of Abemaciclib (LY2835219) With Abiraterone in Men With Prostate Cancer That Has Spread to Other Parts of the Body and is Expected to Respond to Hormonal Treatment (Metastatic Hormone-Sensitive Prostate Cancer)

Open to males ages 18 years and up

• Adenocarcinoma of the prostate.
• High-risk metastatic disease defined as:
• Greater than or equal to (≥)4 bone metastases and/or
• ≥1 visceral metastases
• Androgen deprivation therapy (either medical with a luteinizing hormone-releasing hormone [LHRH] analogue or surgical castration) must have been started prior to randomization and continued throughout the study.
• Adequate organ function
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

• Prior treatment with abemaciclib or any other cyclin dependent kinase 4 and 6 (CDK4 & 6) inhibitor
• Development of metastatic prostate cancer in the context of castrate levels of testosterone (≤50 ng/dL)
• Received any prior systemic therapy for metastatic prostate cancer (including investigational agents), the following exceptions are permitted:
• Up to 3 months of androgen deprivation therapy (ADT) (when given without docetaxel) AND absence of radiographic or prostate specific antigen (PSA) progression prior to randomization
• Up to 6 cycles of docetaxel with ADT AND absence of radiographic or PSA progression prior to randomization
• Clinically significant cardiovascular disease as evidenced by myocardial infarction, arterial thrombotic events, or severe/unstable angina in the past 6 months, or New York Heart Association Class II to IV heart failure
• History of syncope of cardiovascular etiology, ventricular arrhythmia of pathological origin, or sudden cardiac arrest. Chronic and hemodynamically stable atrial arrhythmia well-controlled on medical therapy is permitted
• Uncontrolled hypertension
• Clinically active or chronic liver disease, moderate/severe hepatic impairment
• Known untreated central nervous system (CNS) metastasis. Patients with a history of treated brain metastases are eligible provided that disease is stable following treatment for at least 8 weeks prior to randomization and no requirement for corticosteroid use