Synthesis of amide derivatives containing the imidazole moiety and evaluation of their anti-cardiac fibrosis activity

Three series of N -{[4-([1,2,4]triazolo[1,5- α ]pyridin-6-yl)-5-(6-methylpyridin-2-yl)-1 H -imidazol-2-yl]methyl}acetamides ( 14a – d , 15a – n , and 16a – f ) were synthesized and evaluated for activin receptor-like kinase 5 (ALK5) inhibitory activities in an enzymatic assay. The target compounds showed high ALK5 inhibitory activity and selectivity. The half maximal inhibitory concentration (IC 50 ) for phosphorylation of ALK5 of 16f (9.1 nM), the most potent compound, was 2.7 times that of the clinical candidate EW-7197 (vactosertib) and 14 times that of the clinical candidate LY-2157299. The selectivity index of 16f against p38α mitogen-activated protein kinase was >109, which was much higher than that of positive controls (EW-7197: >41, and LY-2157299: 4). Furthermore, a molecular docking study provided the interaction modes between the target compounds and ALK5. Compounds 14c , 14d , and 16f effectively inhibited the protein expression of α-smooth muscle actin (α-SMA), collagen I, and tissue inhibitor of metalloproteinase 1 (TIMP-1)/matrix metalloproteinase 13 (MMP-13) in transforming growth factor-β-induced human umbilical vein endothelial cells. Compounds 14c and 16f showed especially high activity at low concentrations, which suggests that these compounds could inhibit myocardial cell fibrosis. Compounds 14c , 14d , and 16f are potential preclinical candidates for the treatment of cardiac fibrosis.