Kim et al. reported that entinostat reduces the MDSC population and the combination of entinostat with PD-1 and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibodies resulted in an elimination of approximately 80% of the tumor, whereas the use of immune checkpoint inhibitors against PD-1 and CTLA-4 alone did not provide an anti-tumor immune response [113]. The gene discussed is PDCD1; the disease is neoplasm.