CHEMBL5736516

In Vitro Assays for IDH2m R140Q Inhibitors: Compounds are assayed for IDH2 R140Q inhibitory activity through a cofactor depletion assay. Compounds are preincubated with enzyme, then the reaction is started by the addition of NADPH and α-KG, and allowed to proceed for 60 minutes under conditions previously demonstrated to be linear with respect for time for consumption of both cofactor and substrate. The reaction is terminated by the addition of a second enzyme, diaphorase, and a corresponding substrate, resazurin. Diaphorase reduces resazurin to the highly fluorescent resorufin with the concomitant oxidation of NADPH to NADP, both halting the IDH2 reaction by depleting the available cofactor pool and facilitating quantitation of the amount of cofactor remaining after a specific time period through quantitative production of an easily detected fluorophore.Specifically, into each of 12 wells of a 384-well plate, 1 μl of 100× compound dilution series is placed, followed by the addition of 40 μl of buffer (50 mM potassium phosphate (K2HPO4), pH 7.5; 150 mM NaCl; 10 mM MgCl2, 10% glycerol, 0.05% bovine serum albumin, 2 mM beta-mercaptoethanol) containing 0.25 μg/ml IDH2 R140Q protein. The test compound is then incubated for one hour at room temperature with the enzyme; before starting the IDH2 reaction with the addition of 10 μl of substrate mix containing 4 μM NADPH and 1.6 mM α-KG in the buffer described above. After a further 16 hours of incubation at room temperature, the reaction is halted and the remaining NADPH measured through conversion of resazurin to resorufin by the addition of 25 μl Stop Mix (36 μg/ml diaphorase enzyme and 60 μM resazurin; in buffer). After one minute of incubation the plate is read on a plate reader at Ex544/Em590.For determination of the inhibitory potency of compounds against IDH2 R140Q in an assay format similar to the above, a similar procedure is performed, except that the final testing concentration is 0.25 μg/ml IDH2 R140Q protein, 4 μM NADPH and 1.6 mM α-KG.For determination of the inhibitory potency of compounds against IDH2 R140Q in a high throughput screening format, a similar procedure is performed, except that 0.25 μg/ml IDH2 R140Q protein is utilized in the preincubation step, and the reaction is started with the addition of 4 μM NADPH and 8 μM α-KG.