CHEMBL5730741

Raf IC50 Assay: Compounds disclosed herein were tested against B-Raf (V600E) (PV3849, from Invitrogen) or C-Raf (Y340D/Y341D) (PV3805, from Invitrogen) in a time-resolved fluorescence energy transfer assay. The assay was carried out in reactions (10 μL) containing 0.0625 nM B-Raf or 0.5 nM C-Raf, 25 mM Tris pH7.4, 10 mM MgCl2, 0.5 mM EGTA, 0.5 mM Na3VO4, 5 mM beta-glycerophosphate, 0.01% Triton X-100, 2.5 mM DTT, 0.1% BSA, 0.1 mM ATP, 13.7 nM GST-tagged MEK1 (Full-length protein with K97R mutation, recombinant protein purified from bacterial expression system) and 0-5 μM compounds disclosed herein (final concentration of 1% DMSO). The enzyme was incubated with the compounds at room temperature for 60 minutes and the reactions were initiated by the addition of ATP and GST-MEK1. After reaction at room temperature for 60 minutes, an equal volume of stop/detection solution was added according to the manufacture's instruction (CisBio Bioassays). The stop/detection solution contained Eu3+ cryptate-conjugated anti-phospho MEK1/2 (Ser217/221) rabbit polyclonal antibody and d2-conjugated anti-GST mouse monoclonal antibody in buffer containing 25 mM Tris pH7.4, 400 mM KF, 50 mM EDTA, 0.01% BSA and 0.01% Triton X-100. Plates were sealed and incubated at room temperature for 2 hours, and the TR-FRET signals (ratio of fluorescence emission at 665 nm over emission at 620 nm with excitation at 337 nm wavelength) were recorded on a PHERAstar FS plate reader (BMG Labtech). Phosphorylation of MEK1 led to the binding of anti-phospho-MEK1/2 antibody to GST-MEK1 protein that place fluorescent donor (Eu3+ crypate) in close proximity to the accepter d2 on the anti-GST antibody, thus resulting in a high degree of fluorescence resonance energy transfer from the donor fluorophore (at 620 nm) to the acceptor fluorophore (at 665 nm). Inhibition of RAF kinase activity resulted in decrease of the TR-FRET signal. The IC50 for each compound was derived from fitting the dose-response % inhibition data to the four-parameter logistic model by Graphpad Prism software.