Structure-Based Design, Synthesis, and Biological Evaluation of Imidazo[4,5-b]Pyridin-2-one-Based p38 MAP Kinase Inhibitors: Part†2.

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-one-based p38 MAP kinase inhibitors.

Structure-Based Design, Synthesis, and Biological Evaluation of Imidazo[4,5-b]pyridin-2-one-Based p38 MAP Kinase Inhibitors: Part 1.

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.

Structure-based design, synthesis, and biological evaluation of imidazo[1,2-b]pyridazine-based p38 MAP kinase inhibitors.

We identified novel potent inhibitors of p38 MAP kinase using structure-based design strategy. X-ray crystallography showed that when p38 MAP kinase is complexed with TAK-715 (1) in a co-crystal structure, Phe169 adopts two conformations, where one interacts with 1 and the other shows no interaction with 1. Our structure-based design strategy shows that these two conformations converge into one via enhanced protein-ligand hydrophobic interactions. According to the strategy, we focused on scaffold transformation to identify imidazo[1,2-b]pyridazine derivatives as potent inhibitors of p38 MAP kinase. Among the herein described and evaluated compounds, N-oxide 16 exhibited potent inhibition of p38 MAP kinase and LPS-induced TNF-α production in human monocytic THP-1 cells, and significant in vivo efficacy in rat collagen-induced arthritis models. In this article, we report the discovery of potent, selective and orally bioavailable imidazo[1,2-b]pyridazine-based p38 MAP kinase inhibitors with pyridine N-oxide group.

Synthesis and biological activities of 4-phenyl-5-pyridyl-1,3-thiazole derivatives as selective adenosine A3 antagonists.

To investigate the potency of an adenosine A3 receptor (A3AR) antagonist as an anti-asthmatic drug, a novel series of 4-phenyl-5-pyridyl-1,3-thiazole derivatives was synthesized and evaluated in human adenosine A1, A2A and A3 receptor and rat adenosine A3 receptor binding assays. From investigation of the SAR study, compound 7af was identified as a highly potent human and rat A3AR antagonist. This compound inhibited IB-MECA-induced plasma protein extravasation in the skin of rats and showed good oral absorption. Also, compound 7af significantly inhibited antigen-induced hyper-responsiveness to acetylcholine in actively sensitized Brown Norway rats. These results show that 4-phenyl-5-pyridyl-1,3-thiazole derivatives are potential candidates to enable the evaluation of A3AR antagonists. Further evaluation of this class of compounds may afford a novel anti-inflammatory agent such as an anti-asthmatic drug.

Novel inhibitor of p38 MAP kinase as an anti-TNF-alpha drug: discovery of N-[4-[2-ethyl-4-(3-methylphenyl)-1,3-thiazol-5-yl]-2-pyridyl]benzamide (TAK-715) as a potent and orally active anti-rheumatoid arthritis agent.

The p38 mitogen-activated protein (MAP) kinase has been implicated in the proinflammatory cytokine signal pathway, and its inhibitors are potentially useful for the treatment of chronic inflammatory diseases such as rheumatoid arthritis (RA) and inflammatory bowel disease. To develop a new drug for RA, we synthesized a novel series of 4-phenyl-5-pyridyl-1,3-thiazoles and evaluated their inhibition of p38 MAP kinase, lipopolysaccharide (LPS)-stimulated release of tumor necrosis factor-alpha (TNF-alpha) from human monocytic THP-1 cells in vitro, and LPS-induced TNF-alpha production in vivo in mice. During the course of the study, we found that these compounds risk the inhibition of cytochrome P450 (CYP) isoforms by coordination of the 4-pyridyl nitrogen with heme iron. We therefore investigated the effects of substitution at the 2-position of the pyridyl ring on the inhibitory activity of p38 MAP kinase and CYPs in more detail. As a result, N-[4-[2-ethyl-4-(3-methylphenyl)-1,3-thiazol-5-yl]-2-pyridyl]benzamide (8h, TAK-715) exhibited potent inhibitory activity in these assays (inhibition of p38alpha, IC50 = 7.1 nM; LPS-stimulated release of TNF-alpha from THP-1, IC50 = 48 nM; LPS-induced TNF-alpha production in mice, 87.6% inhibition at 10 mg/kg, po) and no inhibitory activity for major CYPs, including CYP3A4. This compound also showed good bioavailability in mice and rats and significant efficacy in a rat adjuvant-induced arthritis model. Compound 8h was selected as a clinical candidate and is now under clinical investigation for the treatment of RA.

Synthesis and biological activities of 4-phenyl-5-pyridyl-1,3-thiazole derivatives as p38 MAP kinase inhibitors.

A novel series of 4-phenyl-5-pyridyl-1,3-thiazole analogues possessing potent in vitro inhibitory activity against p38 mitogen-activated protein kinase and the release of tumor necrosis factor-alpha (TNF-alpha) from human monocytic THP-1 cells stimulated by lipopolysaccharide has been identified. Subsequent structure-activity relationship (SAR) studies and optimization for absorption, distribution, metabolism, and elimination (ADME) profiles led to the identification of compounds 7 g and 10b as orally active lead candidates that block the in vivo production of proinflammatory cytokine (TNF-alpha). In pharmacokinetic studies, compound 10b showed good oral administration in mice and demonstrated significant in vivo anti-inflammatory activity in an anti-collagen monoclonal antibody-induced arthritis mouse model (minimum effective dose (MED)=30 mg/kg). Further elucidation of this class of compounds may provide novel anti-inflammatory agents, such as anti-rheumatoid arthritis drugs.