A Smoothened (Smo) antagonist. SA1 inhibits Hh pathway by interacting directly with Smo. Inhibits SAG (Smoothened agonist) activation of Hh signaling in Shh-LIGHT 2 cells (IC₅₀ = 3.1 µM). Also inhibits the localization of Smo to cilia. Treatment of Ptch1-/- MEFs with SA1 suppresses the β-galactosidase activity (IC₅₀ = 3.8 µM) and inhibits the expression of Gli1 and Ptch1 in ASZ1 cells.