Immune checkpoint inhibitors targeting the PD-1/PD-L1 pathway and the cytotoxic T-lymphocyte antigen-4 (CTLA-4) have shown impressive rates of durable clinical responses in patients with melanoma, renal cell carcinoma, non-small lung cancer [6] but administration of these agents as monotherapy in PDAC failed to demonstrate anti-tumor activity [7, 8] despite initially promising preclinical findings [9]. The gene discussed is PDCD1; the disease is melanoma.