CHEMBL5736508

Assay for IDO1 Enzymatic Activity Determination: To measure enzymatic activity of human IDO1, the reaction mixture contained (final concentrations) potassium phosphate buffer (50 mM, pH 6.5), ascorbic acid (10 mM), methylene blue (5 μM) and human recombinant IDO1 enzyme (prepared as described in Rohrig et al. J Med Chem, 2012, 55, 5270-5290; final concentration 5 μg/mL) without or with the IDO1 inhibitory compounds provided herein at the indicated concentrations (total volume 112.5 μL). The reaction was initiated by the addition of 37.5 μL of L-Trp (final concentration 100 μM) at room temperature. The reaction was conducted at room temperature during 15 minutes and stopped by the addition of 30 μL of 30% (w/v) trichloroacetic acid.To convert N-formylkynurenine into kynurenine, the reaction mixture was incubated at 65° C. for 30 min. Then 120 μL of 2.5% (w/v) 4-(dimethylamino)-benzaldehyde in acetic acid were added and the mixture incubated for 5 min at room temperature. Kynurenine concentrations were determined by measuring the absorbance at 480 nm. A standard curve was made with pure kynurenine. The IDO1 activity was measured as described above using ten serial concentrations of the IDO1 inhibitory compounds provided herein. Data were fitted using the Prism software (GraphPad Software, Inc.).