Epacadostat (INCB 024360) is an oral, potent and selective IDO1 inhibitor with IC50 value of 71.8 nM.

IDO1 (HeLa cells):7.4 nM, IDO1 (P1.HTR cells):54.46 nM ± 11.18 nM, IDO1:10 nM, IDO1 (HEK293 cells):52.4 nM ± 15.7 nM

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].