An inhibitor of IDO-1 (IC50 = 0.15 μM); selective for IDO-1 over IDO-2 up to a concentration of 200 μM; inhibits IDO-1-mediated production of kynurenine induced by IFN-γ in HeLa cells (IC50 = 1.8 μM); inhibits IDO-1-mediated production of kynurenine induced by LPS and IFN-γ in THP-1 cells and human-derived whole blood ex vivo (IC50s = 1.7 and 4.7 μM, respectively)