(UroToday.com) The CheckMate 9KD trial is a multi-arm open label phase 2 study evaluating the efficacy of the anti-PD-1 antibody nivolumab in combination with other therapies such as docetaxel, rucaparib or enzalutamide in metastatic castration-resistant prostate cancer (mCRPC). The rationale for the combination of nivolumab with docetaxel is that docetaxel is a standard of care therapy for mCRPC that may potentiate anti-tumor immune responses. Prior analysis of this combination at ESMO 2019 demonstrated a 37% overall response rate with one complete response and six partial responses. The study schema is shown below. The co-primary endpoints are overall response rate (investigator reports) and PSA response rate (>= 50% decrease).