In vitro and in vivo pharmacology of CP-945,598, a potent and selective cannabinoid CB1 receptor antagonist for the management of obesity

Cannabinoid CB1 receptor antagonists exhibit pharmacologic properties favorable for the treatment of metabolic disease. CP-945,598 (1-[9-(4-chlorophenyl)-8-(2-chlorophenyl)-9H-purin-6-yl]-4-ethylamino piperidine-4-carboxylic acid amide hydrochloride) is a recently discovered selective, high affinity, competitive CB1 receptor antagonist that inhibits both basal and cannabinoid agonist-mediated CB1 receptor signaling in vitro and in vivo. CP-945,598 exhibits sub-nanomolar potency at human CB1 receptors in both binding (Ki=0.7nM) and functional assays (Ki=0.2nM). The compound has low affinity (Ki=7600nM) for human CB2 receptors. In vivo, CP-945,598 reverses four cannabinoid agonist-mediated CNS-driven responses (hypo-locomotion, hypothermia, analgesia, and catalepsy) to a synthetic cannabinoid receptor agonist. CP-945,598 exhibits dose and concentration-dependent anorectic activity in two models of acute food intake in rodents, fast-induced re-feeding and spontaneous, nocturnal feeding. CP-945,598 also acutely stimulates energy expenditure in rats and decreases the respiratory quotient indicating a metabolic switch to increased fat oxidation. CP-945,598 at 10mg/kg promoted a 9%, vehicle adjusted weight loss in a 10day weight loss study in diet-induced obese mice. Concentration/effect relationships combined with ex vivo brain CB1 receptor occupancy data were used to evaluate efficacy in behavioral, food intake, and energy expenditure studies. Together, these in vitro, ex vivo, and in vivo data indicate that CP-945,598 is a novel CB1 receptor competitive antagonist that may further our understanding of the endocannabinoid system.