Histamine-3 Receptor Inverse Agonists for the Treatment of Obesity: Validation of the Target and Identification of Novel Series

Obesity is a major risk factor for the development of conditions such as hypertension, hyperglycemia, dyslipidemia, coronary artery disease and cancer. Several pieces of evidence, including data in primates, have demonstrated the beneficial effects of histamine-3 receptor (H 3 R) inverse agonists in the regulation of food intake and body weight. A pharmacophore model based on selected published H 3 R ligands and validated by previ- ous investigations, was used to identify the 5-oxy-2-carboxamide-indole core as a novel series of H 3 R inverse agonists. Extensive structure-activity relationship (SAR) investigations were rewarded by the identification of several compounds reversing ( R )- α -methyl-histamine-induced water intake increase and reducing food intake/ body weight in rodent models of obesity. Among those compounds, (4,4-difluoro-piperidin-1-yl)-[1-isopropyl-5- (1-isopropyl-piperidin-4-yloxy)-1 H -indol-2-yl]-methanone, selected as a lead compound, was exhibiting a prom- ising profile, including excellent pharmacokinetic properties, good in vitro safety profile and high efficacy in a chronic rodent model of obesity.