Sonic hedgehog (Shh) is the most widely characterized of the three vertebrate Hedgehog homologs, and is essential for proper embryonic development. Shh binds to its receptor, Patched (Ptch1), resulting in the de-repression of Smoothened. This leads to the activation of Gli2, which regulates the transcription of target genes that include Gli1 and Ptch1. Robotnikinin is the first identified small molecule inhibitor of Shh signaling that acts upstream of Smo, binding directly to Shh with a Kd value of 3.1 μM. Robotnikinin represses Gli-mediated transcription in primary human keratinocytes and synthetic human skin in a concentration-dependent manner.
