Purity >98%. Smoothened (Smo) is a cell surface receptor that, with Patched, mediates sonic hedgehog (Shh) signaling to regulate gene expression through the Gli transcription factors. BMS 833923 is an orally bioavailable inhibitor of Smo. It blocks binding of BODIPY cyclopamine (IC50 = 21 nM) and inhibits Gli activation in cell lines that express wild-type Smo or activated mutant forms of Smo (IC50 s = 6-35 nM). BMS 833923 robustly inhibits Shh pathway activity and prevents tumor growth in medulloblastoma and pancreatic carcinoma xenograft models.