Epacadostat, also known as INCB024360 or INCB24360, is a potent and selective IDO1 inhibitor with IC50 of 71.8 nM±17.5 nM, with potential immunomodulating and antineoplastic activities. It has been shown to promote T and natural killer-cell growth, to increase IFN-γ production, and to reduce conversion to regulatory T (Treg)-like cells in a coculture system of human allogeneic lymphocytes with either dendritic cells or tumor cells.