A selective inhibitor of TGF-β RI, with an IC₅₀ value of 59 nM; poorly inhibits TGF-β RII (IC₅₀ = 400 nM), p38 MAPK (IC₅₀ = 740 nM), and MLK7 (IC₅₀ = 1,400 nM); inhibits TGF-β-induced cell growth (IC₅₀ = 89 nM) and Smad phosphorylation.