Epacadostat (INCB 024360) is an oral-available inhibitor of indoleamine 2, 3-dioxygenase (IDO1), increasing the proliferation and activation of various immune cells and reducing tumor-associated regulatory T cells.

IDO1:10 nM

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. [1]

INCB024360 (100 mg/kg, p.o.), via IDO1 inhibition, suppresses kyn generation and tumor growth in immunocompetent, but not immunodeficient, mice. [1] In mice bearing CT26 colon carcinoma, INCB024360 (100 mg/kg, p.o.) also inhibits the growth of IDO-expressing tumors by reducing kynurenine. [2]

INCB 024360 (INCB024360) is dissolved in DMSO and stored, and then diluted with appropriate media before use[1]. To determine INCB 024360 activity against IDO in recombinant cells, HEK293/MSR cells are transiently transfected with full-length human or mouse IDO1, or mouse IDO2 cDNA, with Transit-293 transfection reagent or Lipofectamine 2000 reagents. INCB 024360 at different concentrations is added to the recovered transfected cells seeded at 2×104 cells per well in a 96-well plate (200 μL/well). The cells are incubated for 2 days, and kyn in the supernatants is measured as described in the HeLa cell assay. The tryptophan 2,3-dioxygenase (TDO) assay is performed similarly with HEK293/MSR cells transfected with a human TDO expression vector[1].