PDCD1 and neoplasm: Over the years, clinical trials involving these two checkpoint inhibitors (anti-PD-1/PD- L1 and CTLA-4) and CPI therapy as novel anticancer therapeutics have been undertaken, inducing lasting tumor regression in more than 14 malignancies, including metastatic lung cancer, melanoma, Hodgkin’s lymphoma, colon carcinoma, urothelial carcinoma, and many others.