Inhibition of p38gamma MAPK (unknown origin) assessed as remaining activity at 100 uM by radioactive filter binding assay in presence of [33P]-ATP relative to control
Enzyme Inhibition Assay: The kinase enzyme binding activities of compounds disclosed herein were determined using a proprietary assay which measures active site-directed competition binding to an immobilized ligand (Fabian, M. A. et al., Nature Biotechnol., 2005, 23:329-336). These assays were conducted by DiscoverX (formerly Ambit; San Diego, Calif.). The Kd value (Dissociation constant value) was calculated as the index of affinity of the compounds to each kinase. The enzyme inhibitory activities of compounds disclosed herein were determined by FRET using synthetic peptides labelled with both donor and acceptor fluorophores (Z-LYTE, Invitrogen Ltd., Paisley, UK). The inhibitory activities of compounds of the invention against p38MAPKgamma (MAPK12: Invitrogen), were evaluated in a similar fashion to that described hereinabove. The enzyme (800 ng/mL, 2.5 uL) was incubated with the test compound (2.5 uL at either 4 ug/mL, 0.4 ug/mL, 0.04 ug/mL, or 0.004 ug/mL) for 2 hr at RT.
Kinase Screen Assay: KINOMEscan (Ambit Biosciences, San Diego, Calif.), a high-throughput method for screening small molecular agents against a large panel of human kinases, was utilized for compound 2. The technology is a competition binding assay that profiled the selectivity of compound 2 against 350 kinases, each fused to a proprietary tag. The quantity of each kinase bound to an immobilized, active site-directed ligand was measured in the presence and absence of compound 2.
Fluorescence Resonance Energy Transfer (FRET) Assay: The enzyme inhibitory activity of test compounds was determined by fluorescence resonance energy transfer (FRET) using synthetic peptides labelled with both donor and acceptor fluorophores (Z-LYTE, Invitrogen). Recombinant, phosphorylated p38 MAPK (MAPK12:Millipore) was diluted in HEPES buffer, mixed with compound at the desired final concentrations and incubated for 2 hr at RT. The FRET peptide (2 uM) and ATP (100 uM) were next added to the enzyme/compound mixture and incubated for 1 hr. Development reagent (protease) was added for 1 hr prior to detection in a fluorescence microplate reader. The site-specific protease only cleaves non-phosphorylated peptide and eliminates the FRET signal. Phosphorylation levels of each reaction were calculated using the ratio of coumarin emission (donor) over fluorescein emission (acceptor) with high ratios indicating high phosphorylation levels and low ratios indicating low phosphorylation levels.
Inhibition of N-terminal His6-tagged recombinant human SAPK3 expressed in baculovirus infected insect Sf9 cells assessed as remaining activity at 1 uM relative to control
Inhibition of human recombinant p38 gamma assessed as phosphorylation of MAPKAP-K2 preincubated for 2 hrs followed by FRET peptide and MAPKAP-K2 addition measured after 1 hr by Z-LYTE assay