High affinity and selective Smoothened (Smo) receptor antagonist (Ki = 4.6 nM). Exhibits >1000-fold selectivity for Smo over a panel of other receptors, ion channels and enzymes. Inhibits Shh-induced Hedgehog signaling in MEF cells. Induces tumor regression in a medulloblastoma allograft mouse model. Orally available and brain penetrant. Purity 98%. MW (observed): 473.42