Design, Synthesis, and Biological Evaluation of Novel Tri- and Tetrasubstituted Imidazoles as Highly Potent and Specific ATP-Mimetic Inhibitors of p38 MAP Kinase: Focus on Optimized Interactions with the Enzyme’s Surface-Exposed Front Region

The synthesis, biological testing, and SAR of novel 2,4,5- and 1,2,4,5-substituted 2-thioimidazoles are described. Amino, oxy, or thioxy substituents at the 2-position of the pyridinyl moiety were evaluated for their contributions to inhibitor potency and selectivity against p38 mitogen activated protein kinase (p38 MAPK) as well as for the ability to minimize cytochrome P450 (CYP450) inhibition. Incorporation of polar substituted (cyclo)aliphatic amino substituents (e.g., tetrahydropyranylamino), which positively interacted with the surface-exposed front region (hydrophobic region II) of the enzyme led to the identification of extremely potent p38 MAPK inhibitors with p38 IC50 values in the low nanomolar range. Approximately 90 pyridinylimidazole-based compounds with a range of potencies against p38α MAP kinase were further investigated for their ability to inhibit the release of tumor necrosis factor-α (TNFα) and/or interleukin-1β (IL-1β) from human whole blood. Some of the most promising drug candidates underwent selectivity profiling against a panel of 17 different kinases besides p38α and/or were tested for their interaction potential toward a number of metabolically relevant CYP450 isozymes.