General Inclusion Criteria:
- Male participants; age ≥ 18 years
- Metastatic castrate-resistant prostate cancer while on anti-androgen treatment with castrate levels of testosterone (≤1.7 nanomoles per liter [nmol/L] or 50 nanograms per deciliter [ng/dL])
- Measurable or non-measurable disease as per radiographic evaluation
- Participants with measurable disease may require a fresh tumor biopsy at study entry
- Eastern Cooperative Oncology Group (ECOG) Performance status of 0 or 1
- Life expectancy of at least 3 months
- Adequate hematologic and end-organ function
- Human immunodeficiency virus (HIV), Hepatitis B, and C test results negative prior to first study treatment
Inclusion Criteria for Participants receiving an enzalutamide-containing treatment
- Disease progression after prior treatment with abiraterone
Inclusion Criteria for Participants receiving a docetaxel-containing treatment
- Disease progression after prior androgen synthesis inhibitor therapy
Inclusion Criteria for all other Participants
- Disease progression after prior androgen synthesis inhibitor treatment and up to 2 prior lines of taxane chemotherapy
General Exclusion Criteria:
- Prior treatment with immune checkpoint blockade therapy
- Prior anticancer treatment including approved agents, systemic radiotherapy, or investigational therapy, within 2-4 weeks prior first study treatment
- Corrected QT interval (QTc) ≥480 msec using Fredericia's QT correction formula (based on an average of triplicate recordings)
- Prior allogeneic stem cell or solid organ transplantation
- Prior treatment with drugs that stimulate the immune system within 4 weeks prior to first study treatment
- Prior treatment with drugs that suppress the immune system within 2 weeks prior to first study treatment
- Received a live, attenuated vaccine within 4 weeks prior to first study treatment, or may need to receive a vaccine during study treatment
- Presence of metastases in the brain or cancer spreading into the cerebrospinal fluid - CSF (leptomeningeal disease)
- Prior pulmonary fibrosis, pneumonia, or pneumonitis
- Cancer other than prostate within 2 years prior to study entry, except for some cancers with a low risk of spreading like non-melanoma skin
- Prior treatment with an agent targeting the adenosine pathway
- No oral or IV antibiotics within 2 weeks prior to first study treatment
- No severe infection within 4 weeks prior to first study treatment
- No clinically significant cardiac disease
- Inability to swallow medications
Exclusion Criteria for Participants receiving an enzalutamide-containing treatment
- Prior treatment with docetaxel, cabazitaxel, or other taxane chemotherapy (prior docetaxel [up to 6 cycles] for hormone-sensitive prostate cancer is allowed if the last dose was at least 6 months prior to study treatment initiation)
- Prior treatment with enzalutamide or similar therapy other than abiraterone
- Active or history of autoimmune disease or immune deficiency
- History of severe allergic reactions to antibody therapy
- Concomitant use of a medication prohibited by the protocol (including certain transporter substrates as well as known strong CYP3A4 inducers and CYP3A4 inhibitors) within 4 weeks prior to and throughout study treatment
Exclusion Criteria for Participants receiving a docetaxel-containing treatment
- Prior treatment with docetaxel, cabazitaxel, or other taxane chemotherapy
- Active or history of autoimmune disease or immune deficiency
- History of severe allergic reactions to antibody therapy
- Concomitant use of a medication prohibited by the protocol (including certain transporter substrates as well as known strong CYP3A4 inducers and CYP3A4 inhibitors) within 4 weeks prior to and throughout study treatment
Exclusion Criteria for all other Participants
- Prior treatment with docetaxel, cabazitaxel, topoisomerase 1 inhibitors, or other taxane chemotherapy
- Active or history of autoimmune disease or immune deficiency
- History of severe allergic reactions to antibody therapy
- Concomitant use of a medication prohibited by the protocol (including certain transporter substrates as well as known strong CYP3A4 inducers and CYP3A4 inhibitors) within 4 weeks prior to and throughout study treatment