Identification of Spiro[chromene-2,4'-piperidine]s As Potent, Selective, and Gq-Biased 5-HT2C Receptor Partial Agonists.

A series of spiropiperidines was designed and synthesized by structural modifications based on our previous lead compound 1 and evaluated with cellular signaling assays for the discovery of 5-HT2C receptor (5-HT2CR) selective agonists with a G(q) bias. Structure-activity relationship (SAR) studies of spiropiperidines uncovered spiro[chromene-2,4 '-piperidine]s as a novel chemotype of 5-HT2CR selective agonists. Among this new series, the 7-chloro analogue 8 was identified as the most potent and selective 5-HT2CR partial agonist (E-max = 71.09%) with an EC50 value of 121.5 nM and no observed activity toward 5-HT2AR or 5-HT2BR. Moreover, compound 8 exhibited no recruitment activity for beta-arrestin and showed low inhibition of hERG at 10 mu M. These findings may pave the way to develop more potent G(q)-biased 5-HT2CR partial agonists as useful pharmacological tool compounds or potential drug candidates.