LY364947 is a selective inhibitor of TGF-β RI (TGFR-I, TβR-I, ALK-5), with an IC₅₀ value of 59 nM. LY364947 only weakly inhibits TGF-β RII (IC₅₀ = 400 nM), p38 MAPK (IC₅₀ = 740 nM), and mixed lineage kinase-7 (MLK-7; IC₅₀ = 1,400 nM).It inhibits TGF-β-induced cell growth (IC₅₀ = 89 nM) in NIH 3T3 mouse fibroblasts and TGF-β-directed Smad phosphorylation, synthesis of fibronectin, PAI-1 and uPA protein, and matrigel invasion in MDA-MB-231 cells.