Study of Pembrolizumab (MK-3475) Plus Docetaxel Versus Placebo Plus Docetaxel in Chemotherapy-naïve Metastatic Castration-resistant Prostate Cancer (mCRPC) (MK-3475-921/KEYNOTE-921)

Exclusion Criteria

• •Has a known additional malignancy that is progressing or has required active treatment in the last 3 years
• •Has an active autoimmune disease that has required systemic treatment in past 2 years
• •Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy
• •Has undergone major surgery including local prostate intervention (excluding prostate biopsy) within 28 days prior to randomization and not recovered adequately from the toxicities and/or complications
• •Has a gastrointestinal disorder affecting absorption or is unable to swallow tablets/capsules
• •Has an active infection (including tuberculosis) requiring systemic therapy
• •Has a history of (non-infectious) pneumonitis that required steroids or current pneumonitis
• •Has known active human immunodeficiency virus (HIV), hepatitis B virus (HBV) or hepatitis C virus (HCV) infection
• •Has known active central nervous system (CNS) metastases and/or carcinomatous meningitis
• •Has severe hypersensitivity (≥Grade 3) to pembrolizumab and/or any of its excipients
• •Has symptomatic congestive heart failure (New York Heart Association Class III or IV heart disease)
• •Has had a prior anti-cancer monoclonal antibody (mAb) prior to randomization or who has not recovered (i.e., Grade ≤1 or at baseline) from AEs due to mAbs
• •Has used herbal products that may have hormonal anti-prostate cancer activity and/or are known to decrease PSA levels (e.g. saw palmetto) prior to randomization
• •Has received prior treatment with radium or other therapeutic radiopharmaceuticals for prostate cancer
• •Has received prior therapy with an anti-programmed cell death-1 (anti-PD-1), anti-programmed cell death-ligand 1 (anti-PD-L1), or anti PD-L2 agent or with an agent directed to another stimulatory or co-inhibitory T-cell receptor (e.g., cytotoxic T-lymphocyte-associated protein 4 \[CTLA-4\], OX-40, CD137)
• •Has received prior treatment with docetaxel or another chemotherapy agent for mCRPC
• •Has hypersensitivity to docetaxel or polysorbate 80
• •Is currently receiving either strong or moderate inhibitors of cytochrome P450 (CYP)3A4 that cannot be discontinued for the duration of the study
• •Has received prior targeted small molecule therapy or abiraterone acetate, enzalutamide, apalutamide, or darolutamide within 4 weeks prior to the first dose of study treatment, or has not recovered (i.e., Grade ≤1 or at baseline) from AEs due to a previously administered agent
• •Has received prior radiotherapy to within 2 weeks of start of study treatment. Participants must have recovered from all radiation-related toxicities, not require corticosteroids, and not have had radiation pneumonitis
• •Has received a live vaccine within 30 days prior to randomization
• •Has received treatment with 5α reductase inhibitors (eg, finasteride or dutasteride), estrogens, and/or cyproterone within 4 weeks prior to randomization
• •Has received prior treatment with ketoconazole for prostate cancer
• •Is currently participating in or has participated in a study of an investigational agent or has used an investigational device within 4 weeks prior to the first dose of study treatment
• •Has a "superscan" bone scan
• •Is expecting to conceive or father children within the projected duration of the study, starting with the screening visit through 120 days after the last dose of study treatment
• •Has had an allogenic tissue/solid organ transplant