ALK5-IN-82 is a potent and selective inhibitor against activin receptor-like kinase 5 ( ALK5 ) with an IC 50 value of 9.1 nM. ALK5-IN-82 inhibits 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. ALK5-IN-82 is promising for research of cardiac fibrosis.