Tri- and Tetrasubstituted Pyridinylimidazoles as Covalent Inhibitors of c‑Jun N‑Terminal Kinase 3

The
concept of covalent inhibition of c-Jun N-terminal kinase 3
(JNK3) was successfully transferred to our well validated pyridinylimidazole
scaffold varying several structural features in order to deduce crucial
structure–activity relationships. Joint targeting of the hydrophobic
region I and methylation of imidazole-N1 position increased the activity
and reduced the number of off-targets. The most promising covalent
inhibitor, the tetrasubstituted imidazole 3-acrylamido-N-(4-((4-(4-(4-fluorophenyl)-1-methyl-2-(methylthio)-1H-imidazol-5-yl)­pyridin-2-yl)­amino)­phenyl)­benzamide (7) inhibits the JNK3 in the subnanomolar range (IC50 =
0.3 nM), shows high metabolic stability in human liver microsomes,
and displays excellent selectivity in a screening against a panel
of 410 kinases. Covalent bond formation to Cys-154 was confirmed by
incubation of the inhibitors with wild-type JNK3 and JNK3-C154A mutant
followed by mass spectrometry.