We identified a lead series of p38 mitogen‐activated protein kinase inhibitors using a structure‐based design strategy from high‐throughput screening of hit compound 1. X‐ray crystallography of 1 with the kinase showed an infrequent flip of the peptide bond between Met109 and Gly110, which was considered to lead to high kinase selectivity. Our structure‐based design strategy was to conduct scaffold transformation of 1 with maintenance of hydrogen bond interactions with the flipped hinge backbone of the enzyme. In accordance with this strategy, we focused on scaffold transformation to identify imidazo[4,5‐b]pyridin‐2‐one derivatives as potent inhibitors of the p38 MAP kinase. Of the compounds evaluated, 21 was found to be a potent inhibitor of the p38 MAP kinase, lipopolysaccharide‐induced tumor necrosis factor‐α (TNF‐α) production in human monocytic leukemia cells, and TNF‐α‐induced production of interleukin‐8 in human whole blood cells. Herein we describe the discovery of potent and orally bioavailable imidazo[4,5‐b]pyridin‐2‐one‐based p38 MAP kinase inhibitors that suppressed cytokine production in a human whole blood cell‐based assay.

Cholesterol 24-hydroxylase (CH24H or CYP46A1) is a brainspecific cytochrome P450 enzyme that metabolizes cholesterol into 24Shydroxycholesterol (24HC) for regulating brain cholesterol homeostasis. For the development of a novel and potent CH24H inhibitor, we designed and synthesized 3,4-disubstituted pyridine derivatives using a structure-based drug design approach starting from compounds 1 (soticlestat) and 2 (thioperamide). Optimization of this series by focusing on ligand-lipophilicity efficiency value resulted in the discovery of 4-(4-methyl-1-pyrazolyl)pyridine derivative 17 (IC 50 = 8.5 nM) as a potent and highly selective CH24H inhibitor. The X-ray crystal structure of CH24H in complex with compound 17 revealed a unique binding mode. Both blood−brain barrier penetration and reduction of 24HC levels (26% reduction) in the mouse brain were confirmed by oral administration of 17 at 30 mg/kg, indicating that 17 is a promising tool for the novel and selective inhibition of CH24H.

We identified novel potent inhibitors of p38 mitogen-activated protein (MAP) kinase using a structure-based design strategy, beginning with lead compound, 3-(butan-2-yl)-6-(2,4-difluoroanilino)-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one (1). To enhance the inhibitory activity of 1 against production of tumor necrosis factor-α (TNF-α) in human whole blood (hWB) cell assays, we designed and synthesized hybrid compounds in which the imidazo[4,5-b]pyridin-2-one core was successfully linked with the p-methylbenzamide fragment. Among the compounds evaluated, 3-(3-tert-butyl-2-oxo-2,3-dihydro-1H-imidazo[4,5-b]pyridin-6-yl)-4-methyl-N-(1-methyl-1H-pyrazol-3-yl) benzamide (25) exhibited potent p38 inhibition, superior suppression of TNF-α production in hWB cells, and also significant in vivo efficacy in a rat model of collagen-induced arthritis (CIA). In this paper, we report the discovery of potent, selective, and orally bioavailable imidazo[4,5-b]pyridin-2-onebased p38 MAP kinase inhibitors.

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