Table 1.

Clinical studies of checkpoint inhibitors in prostate cancer

Drug/reference	Phase/disease/(n)	Dose	Results
Ipilimumab (post-chemo) (13)	Phase III, mCRPC (799)	8 Gy EBRT to one bone lesion followed by ipilimumab 10 mg/kg or placebo for 4 doses, then maintenance every 3 months	Median OS 11.2 vs.10.0 months (HR = 0.85; P = 0.053)
Ipilimumab (chemo-naïve) (12)	Phase III, mCRPC (799)	Ipilimumab 10 mg/kg or placebo every 3 weeks for 4 doses, then maintenance every 3 months	Median OS 28.7 vs. 29.7 months (HR = 1.11; P = 0.3667)
Nivolumab (14)	Phase I, mCRPC (17)	Nivolumab 0.1–10 mg/kg i.v. every 2 weeks	No objective responses, one patient sustained > 50% PSA decline
Pembrolizumab (15)	Phase I, mCRPC (23)	Pembrolizumab 10 mg/kg every 2 weeks up to 24 months	3 patients with confirmed PR (ORR 13%) and 9 with SD (39%)
Tremelimumab (54)	Phase I, BCR (11)	Tremelimumab with high-dose bicalutamide	3 patients with prolonged PSA doubling time

EBRT: external beam radiation therapy; HR: hazard ratio; mCRPC: metastatic castration-resistant prostate cancer; ORR: overall response rate; OS: overall survival; PR: partial response; PSA: prostate-specific antigen; SD: stable disease; BCR: biochemical recurrence (PSA-only disease)