Design, synthesis, and antifibrosis evaluation of 4-(benzo-[c][1,2,5]thiadiazol-5-yl)-3(5)-(6-methyl- pyridin-2-yl)pyrazole and 3(5)-(6-methylpyridin- 2-yl)-4-(thieno-[3,2,-c]pyridin-2-yl)pyrazole derivatives

Six series of 4-(benzo[ c ][1,2,5]thiadiazol-5-yl)-3(5)-(6-methylpyridin-2-yl)- pyrazoles 18a – d , 19a – d , 22a – d and 3(5)-(6-methylpyridin-2-yl)-4-(thieno[3,2,- c ]- pyridin-2-yl)pyrazoles 20a – d , 21a – d , 23c , 23d have been synthesized and evaluated for their activin receptor-like kinase 5 (ALK5) and p38α mitogen activated protein (MAP) kinase inhibitory activities in enzymatic assays. Among these compounds, the most active compound, 22c , inhibited ALK5 phosphorylation with an IC 50 value of 0.030 μM in the enzymatic assay. Compound 22c showed four-fold more potent activity against ALK5 kinase than the clinical candidate, compound LY-2157299 . The selectivity index of 22c against p38α MAP kinase is 235, which is much higher than that of LY-2157299 (4) and equally selective to that of EW-7197 (218). Compound 22c effectively suppressed protein and mRNA expression of collagen I and α-SMA in TGF-β-induced LX-2 human hepatic stellate cell (HSC), this result shows that compound 22c has the ability to inhibit the activation of HSC. Compound 22c is expected to be a preclinical candidate for the treatment of hepatic fibrosis .