The clinical data surrounding inhibition of PD-1/PD-L1 in prostate cancer is evolving. In the past, I have written a couple of articles about both single-agent and combination approaches for metastatic castration-resistant prostate cancer (mCRPC).1, 2 The field has evolved to the point where we recognize that single-agent PD-1/PD-L1 inhibition is unlikely to yield a major benefit for an unselected population. In the KEYNOTE-199 trial, pembrolizumab yielded 5% and 3% objective response rates in patients with PD-L1 positive and negative tumors, respectively.3