PDCD1 and neoplasm: During the last decade, a great number of monoclonal antibodies have been generated and tested in vitro and in vivo for their ability to counteract the immune escape of tumor cells, and some of them have been approved by the FDA for clinical use in different types of tumors, for instance, Atezolizumab (an anti-PD-L1 mAb) for the treatment of non-small-cell lung cancer (NSCLC), Pembrolizumab (an anti-PD-1 mAb) for triple-negative breast cancer (TNBC), and, more recently, Relatlimab (an anti-LAG-3 mAb) for metastatic or unresectable melanoma [13,14,15].