A Study of Abiraterone Acetate Plus Prednisone With or Without Abemaciclib (LY2835219) in Participants With Prostate Cancer

Inclusion Criteria:

- Histologically confirmed adenocarcinoma of the prostate.

- Metastatic prostate cancer documented by positive bone scan and/or measurable soft
tissue metastatic lesions by CT or magnetic resonance imaging (MRI).

- Progressive disease at study entry demonstrated during continuous androgen-deprivation
therapy (ADT)/post orchiectomy defined as one or more of the following:

- PSA progression

- Radiographic progression per Response Evaluation Criteria in Solid Tumors
(RECIST)1.1 for soft tissue and/or per Prostate Cancer Working Group 3 (PCWG3)
for bone, with or without PSA progression

- Be able and willing to undergo mandatory tumor biopsy of at least one metastatic site.

- Have adequate organ function.

- Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0-1.

Exclusion Criteria:

- Prior therapy with cytochrome P450 (CYP)17 inhibitors.

- Prior treatment with abemaciclib or any cyclin-dependent kinase (CDK) 4 & 6
inhibitors.

- Prior cytotoxic chemotherapy for metastatic castration resistant prostate cancer
(participants treated with docetaxel in the metastatic hormone-sensitive prostate
cancer [mHSPC are eligible]), prior radiopharmaceuticals for prostate cancer, or prior
enzalutamide, apalutamide, or sipuleucel-T. Participants who had prior radiation or
surgery to all target lesions.

- Currently enrolled in a clinical study involving an investigational product.

- Gastrointestinal disorder affecting the absorption or ability to swallow large pills.

- Clinically significant heart disease, active or chronic liver disease, moderate/severe
hepatic impairment (Child-Pugh Class B and C).