IDO-1 expression by the cancer cell was associated with immunosuppressive function through inhibition of T-cell receptor expression and induction of Treg [for review see (83)] andhigh IDO-1 activity was linked with ICB refractoriness in NSCLC (84), therefore making it a very attractive target and multiple inhibitors have been developed and are under evaluation in multiple cancer types. The gene discussed is IDO1; the disease is cancer.