SB-431542 is a potent and selective inhibitor of the TGF-β1 receptor ALK5 (IC50 = 94 nM). It is a less potent antagonist of ALK4 (IC50 = 140 nM) and ALK7. It does not affect the BMP receptors ALK2, ALK3, ALK6, or a panel of other kinases tested. SB-431542 specifically blocks Smad signaling, reducing gene expression relevant to fibrosis and cancer. Through its effects on ALK/Smad signaling, SB-431542 suppresses renewal in embryonic and induced pluripotent stem cells and promotes their differentiation.
