Discovery of 4-Phenylpiperidine-2-Carboxamide Analogues as Serotonin 5-HT2C Receptor-Positive Allosteric Modulators with Enhanced Drug-like Properties

Targeting the serotonin (5-HT) 5-HT(2C) receptor (5-HT(2C)R) allosteric site to potentiate endogenous 5-HT tone may provide novel therapeutics to alleviate the impact of costly, chronic diseases such as obesity and substance use disorders. Expanding upon our recently described 5-HT(2C)R-positive allosteric modulators (PAMs) based on the 4-alkylpiperidine-2-carboxamide scaffold, we optimized the undecyl moiety at the 4-position with variations of cyclohexyl- or phenyl-containing fragments to reduce rotatable bonds and lipophilicity. Compound 12 (CTW0415) was discovered as a 5-HT(2C)R PAM with improved pharmacokinetics and reduced off-target interactions relative to our previous series of molecules. The in vivo efficacy of compound 12 to potentiate the effects of a selective 5-HT(2C)R agonist was established in a drug discrimination assay. Thus, 12 is reported as a 5-HT(2C)R PAM with characteristics suitable for in vivo pharmacological studies to further probe the biological and behavioral mechanisms of allosteric modulation of a receptor important in several chronic diseases.