Discovery of 1-[9-(4-Chlorophenyl)-8-(2-chlorophenyl)-9H-purin-6-yl]-4-ethylaminopiperidine-4-carboxylic Acid Amide Hydrochloride (CP-945,598), a Novel, Potent, and Selective Cannabinoid Type 1 Receptor Antagonist

We report the structure-activity relationships, design, and synthesis of the novel cannabinoid type 1 (CB1) receptor antagonist 3a (CP-945,598). Compound 3a showed subnanomolar potency at human CB1 receptors in binding (Ki = 0.7 nM) and functional assays (Ki = 0.12 nM). In vivo, compound 3a reversed cannabinoid agonist-mediated responses, reduced food intake, and increased energy expenditure and fat oxidation in rodents.