A selective inhibitor of TGF-β type I receptor ALK5 kinase, type I activin/nodal receptor ALK4 and type I nodal receptor ALK7 (IC₅₀ values are 12, 45 and 7.5 nM respectively). Blocks phosphorylation of Smad2 and inhibits TGF-β-induced epithelial-to-mesenchymal transition. Helps maintain homogeneity and long-term in vitro self-renewal of human induced pluripotent stem cells (iPSCs).