Synthesis and biological evaluation of 4(5)-(6-alkylpyridin-2-yl)imidazoles as transforming growth factor-beta type 1 receptor kinase inhibitors

A series of 4(5)-(6-alkylpyridin-2-yl)imidazoles 13a-p, 17a, and 17b have been synthesized and evaluated for ALK5 inhibitory activity in an enzyme assay and in cell-based luciferase reporter assays. The quinoxalinyl analogue 13e inhibited ALK5 phosphorylation with an IC50 of 0.012 muM and showed more than 90% inhibition at 0.05 muM in a luciferase reporter assay using HaCaT cells transiently transfected with p3TP-luc reporter construct. The binding mode of 13e generated by flexible docking studies shows that 13e fits well into the active site cavity of ALK5 by forming several tight interactions.