HPI-1 is a hedgehog (Hh) signaling inhibitor without significantly effecting Wnt signaling. It inhibits Gli1 and Gli2 induced activation and the proliferation of SmoM2 expressing cell lines. Hedgehog (Hh) signaling inhibitor. Inhibits Sonic hedgehog (Shh)-, SAG- and Gli-induced Hh pathway activation in Shh-LIGHT2 cells (IC50 values are 1.5, 1.5, 4 and 6 μM for Shh-, SAG-, Gli2- and Gli1-induced activation). Also inhibits Hh pathway activation.