The discovery of 12?-methyl-17-epi-18-nor-bile acids as potent and selective TGR5 agonists

Recent discoveries have demonstrated that the physiological function of bile acids extends to the regulation of diverse signaling processes through interactions with nuclear and G protein-coupled receptors, most notably the Farnesoid-X nuclear receptor (FXR) and the G protein-coupled bile acid receptor 1 (GPBAR1, also known as TGR5). Targeting such signaling pathways pharmacologically, i.e. with bile acid-derived therapeutics, presents great potential for the treatment of various metabolic, inflammatory immune, liver, and neurodegenerative diseases.Here we report the discovery of two potent and selective TGR5 agonists (NZP196 and 917). These compounds are the taurine conjugates of 6 alpha-ethyl-substituted 12 beta-methyl-18-nor-bile acids with the side chain being located on the alpha-face of the steroid scaffold. The compounds emerged from a screening effort of a diverse library of 12 beta- methyl-18-nor-bile acids that were synthesized from 12 beta-methyl-18-nor-chenodeoxycholic acid and its C17-epimer. Upon testing for FXR activity, both compounds were found to be inactive, thus revealing selectivity for TGR5.