Studies directed toward the elucidation of the pharmacophore of steroid-based Sonic Hedgehog signaling inhibitors

Previous work from our laboratory has established that the readily available steroid-based analog 2 of cyclopamine 1 is, like 1, a highly potent inhibitor of Hedgehog signaling. The first structure-activity relationship studies on 2, i.e., the synthesis and biological evaluation of both the C-17 epi analog 4 and the C-3 deoxy analog 11, both of which are more potent than cyclopamine 1, are described. The implications of these results for the emerging pharmacophore of these Sonic Hedgehog signaling inhibitors are discussed.