A Phase 3, Randomized, Double-blind Study of Pembrolizumab (MK-3475) Plus Docetaxel Plus Prednisone versus Placebo Plus Docetaxel Plus Prednisone in Participants with Chemotherapy-naïve Metastatic Castration-Resistant Prostate Cancer (mCRPC) who have Progressed on a Next Generation Hormonal Agent (NHA) (KEYNOTE-921)

INTERVENTION: Group 1: 1 Xper 3 weeks 200 mg pembroluzimab and 75mg/m2 docetale Xby IV Infusion and twice a day 5mg prednison taken orally Groep 2: 1 Xper 3 weeks placebo and 75mg/m2 docetale Xby IV Infusion and twice a day 5mg prednison taken orally CONDITION: ; Castration‐Resistant metastatic Prostate Cancer 10036958 PRIMARY OUTCOME: To evaluate; ; ‐ overall survival (OS) ; ‐ radiographic progression‐free survival (rPFS); SECONDARY OUTCOME: To evaluate: ; ‐ the first subsequent anti‐cancer therapy or death (TFST) ; ‐ Prostate‐specific antigen (PSA) response rate ; ‐ Objective response rate (ORR) and the duration of response (DOR) ; ‐ Time to pain progression (TTPP) ; ‐ Time to first symptomatic skeletal‐ related event (SSRE) ; ‐ Time to PSA progression ; ‐ Time to radiographic soft tissue progression ; ‐ the safety and tolerability ; INCLUSION CRITERIA: 1. Have histologically‐ or cytologically‐confirmed (if acceptable according to local health authority regulations) adenocarcinoma of the prostate without small cell histology. Diagnosis must be stated in a pathology report and confirmed by the investigator 2. Have prostate cancer progression while on androgen deprivation therapy (or post bilateral orchiectomy) within 6 months prior to screening, as determined by the investigator, by means of one of the following: a. PSA progression using local laboratory values as defined by a minimum of 2 consecutive rising PSA levels with an interval of >=1 week between each assessment where the PSA value at screening should be >=1 ng/mL b. Radiographic disease progression in soft tissue based on RECIST 1.1 criteria with or without PSA progression c. Radiographic disease progression in bone based on PCWG, defined as the appearance of 2 or more new bone lesions on bone scan with or