Despite the unfavorable results in prostate cancer by current immune checkpoint inhibitors, PD-1 inhibitors including nivolumab and pembrolizumab, anti-PD-L1 inhibitors including atezolizumab and avelumab, and anti-CTLA4 inhibitor ipilimumab [58] continue to be rigorously tested in multiple clinical trials in CRPC patients (Table 2). Here, CTLA4 is linked to prostate cancer.