Identification, Optimization, and Pharmacology of Acylurea GHS-R1a Inverse Agonists

Ghrelin plays a major physiological role in the control of food intake, and inverse agonists of the ghrelin receptor (GHS-R1a) are widely considered to offer utility as antiobesity agents by lowering the set-point for hunger between meals. We identified an acylurea series of ghrelin modulators from high throughput screening and optimized binding affinity through structure-activity relationship studies. Furthermore, we identified specific substructural changes, which switched partial agonist activity to inverse agonist activity, and optimized physicochemical and DMPK properties to afford the non-CNS penetrant inverse agonist 22 (AZ-GHS-22) and the CNS penetrant inverse agonist 38 (AZ-GHS-38). Free feeding efficacy experiments showed that CNS exposure was necessary to obtain reduced food intake in mice, and it was demonstrated using GHS-R1a null and wild-type mice that this effect operates through a mechanism involving GHS-R1a.