Information Epacadostat (INCB024360) Epacadostat (INCB024360) is a potent and selective indoleamine 2,3-dioxygenase (IDO1) inhibitor with IC50 of 10 nM and displays high selectivity over other related enzymes such as IDO2 or tryptophan 2,3-dioxygenase (TDO). Targets IDO1 (immune cells) 10 nM In vitro In IFN-γ–treated human HeLa cells, INCB024360 potently inhibits kynurenine production. INCB024360 also promotes T and natural killer (NK)-cell growth, increases IFN-gamma production, and reduces conversion to regulatory T (T(reg))-like cells. In vivo INCB024360 (100 mg/kg, p.o.), via IDO1 inhibition, suppresses kyn generation and tumor growth in immunocompetent, but not immunodeficient, mice. In mice bearing CT26 colon carcinoma, INCB024360 (100 mg/kg, p.o.) also inhibits the growth of IDO-expressing tumors by reducing kynurenine.