Background:

SB431542 is a selective ATP-competitive inhibitor of ALK5 (activin receptor-like kinase 5) with an IC50 value of 94 nM [1].

SB431542 showed most potent efficacy among the series of hits screened out. It inhibited TGF-β1-induced mRNA formation in A498 cells with IC50 value of 50 nM. It also markedly reduced TGF-β-induced nuclear accumulation of Smad proteins with IC50 value of 40 nM. SB431542 was found to be a selective inhibitor for ALK4, ALK5 and ALK7, suppresses the phosphorylation of Smad2. It showed no significant inhibition of ALK1, ALK2, ALK6 and showed weak effect on ALK3 at concentration of 10 μM [1, 2].

参考文献:
[1] Callahan J F, Burgess J L, Fornwald J A, et al. Identification of novel inhibitors of the transforming growth factor β1 (TGF-β1) type 1 receptor (ALK5). Journal of medicinal chemistry, 2002, 45(5): 999-1001.
[2] Inman G J, Nicolás F J, Callahan J F, et al. SB-431542 is a potent and specific inhibitor of transforming growth factor-β superfamily type I activin receptor-like kinase (ALK) receptors ALK4, ALK5, and ALK7. Molecular pharmacology, 2002, 62(1): 65-74.