The purpose of this study is to see if the study drug abemaciclib in combination with other anti-cancer therapies is safe in Japanese participants with advanced cancer.

Inclusion Criteria:

• Participant with histologically confirmed adenocarcinoma of the prostate.
• Participant with metastatic disease documented by positive bone scan and/or measurable soft tissue metastatic lesions by computed tomography (CT) or magnetic resonance imagining (MRI).
• Participant who has serum testosterone level is ≤1.73 nanomoles per liter (nmol/L) (50 nanograms per deciliter).
• Participant who has progressive disease at study entry demonstrated during continuous androgen-deprivation therapy (ADT)/post orchiectomy.
• Participant with adequate organ function.
• Participant with Eastern Cooperative Oncology Group (ECOG) performance status of 0-1.

Exclusion Criteria:

• Participant who was treated with cytochrome P450 (CYP)17 inhibitors (including abiraterone acetate, TAK-700, TOK-001, and ketoconazole).
• Participant who was treated with abemaciclib or any cyclin dependent kinase 4 and 6 (CDK4 and 6) inhibitors.
• Participant who has prior cytotoxic chemotherapy for metastatic castration-resistant prostate cancer (mCRPC), prior radiopharmaceuticals for prostate cancer (PCa), or prior sipuleucel-T.
• Participant who has gastrointestinal disorder affecting absorption or inability to swallow large pills.
• Participant who has clinically active or chronic liver disease, moderate/severe hepatic impairment, ascites, or bleeding disorders secondary to hepatic dysfunction.
• Participant who has known or suspected central nervous system metastatic disease.
• Participant who was treated with drugs known to be strong inhibitors, or strong or moderate inducers of cytochrome P450 3A4 (CYP3A4) and the treatment cannot be discontinued or switched prior to starting study treatment.