CHEMBL5739376

RET and KDR Enzyme Assay: Kinase activity was detected using CisBio HTRF kinEASE kit based on time-resolved fluorescence transfer (FRET). The assay was performed in 384-well white plates (Corning #3574) in a reaction volume of 10 μL containing 1×CisBio enzymatic buffer supplemented with a final concentration of 5 mM MgCl2, 1 mM DTT, 10 nM SEB and 0.01% Triton X100 for RET. The same buffer was used for the KDR biochemical assay with the addition of 2 mM MnCl2. Inhibitors were pre-incubated in the plate for 15 mins with 5 μL kinase and assay buffer at the following concentrations; 13 pM RET (Carna Biosciences; 08-159) and 150 pM KDR (Millipore; 14-630). The reaction was initiated by the addition of 5 μL ATP and substrate at 2× final reaction concentrations. For RET, this was 18 μM and 2 μM; for KDR, this was 16 μM and 1 μM, respectively. Reactions were performed at ATP Km for each target. The assay was allowed to proceed at room temperature for 20 mins before terminating with the addition of 10 μL HTRF detection buffer containing EDTA supplemented with TK-antibody labelled with Eu3+-Cryptate (1:100 dilution) and streptavidin-XL665 (128 nM). Following incubation at room temperature for 1 hour, FRET signal was measured using the Pherastar FS Microplate Reader.