Synthesis and pharmacological characterization of UVI3502, a novel cannabinoid receptor 1 (CB1) antagonist/inverse agonist

The endocannabinoid (eCB) system regulates several brain functions and is implicated in neurological disorders. The pharmacological blockade of cannabinoid receptors has a therapeutic potential for various cognitive deficits, but also produces severe psychiatric side effects. Hence, new cannabinoid compounds that potentiate therapeutic effects, while minimizing toxicity, are required. In this study, we synthesized and characterized a novel antagonist/inverse agonist of CB 1 receptors. UVI3502 showed affinity for two [ 3 H]CP55,940 binding sites (IC 50Hi 0.47 ± 1.94 nM and IC 50Lo 1470 ± 1.80 nM). Subsequent binding assays performed in CB 1 and CB 2 overexpressing membranes determined that the low affinity binding site corresponded to CB 1 , but the high-affinity binding site of UVI3502 did not correspond to CB 2 and the possibility of it corresponding to GPR55 was analyzed. The affinity of UVI3502 for CB 1 receptors was further confirmed with neuroanatomical specificity by autoradiography in key brain areas, in which functional [ 35 S]GTPɣS assays demonstrated that UVI3502 behaved as an antagonist/inverse agonist of CB 1 receptors, blocking the stimulation evoked by potent cannabinoid receptor agonist CP55,940 and decreasing basal [ 35 S]GTPɣS binding. The in silico characterization of the binding to CB 1 receptor through molecular docking and molecular dynamics suggests that this activity is explained by the planar and rigid structure of UVI3502, which is optimal for interactions with the inactive state of the receptor. These results indicate that UVI3502 is a novel antagonist/inverse agonist of CB 1 receptors, making it a compelling candidate for pharmacologically blocking cannabinoid receptors in the central nervous system. Significance Statement UVI3502 is a novel antagonist/inverse agonist of CB 1 receptors, with almost no affinity for CB 2 receptors and an additional high-affinity binding site for a third, cannabinoid-like receptor, potentially GPR55. In relevant brain areas for learning and memory processes with a high expression of CB 1 , UVI3502 blocks the stimulation evoked by the cannabinoid receptor agonist CP55,940, rendering it as an interesting compound for the pharmacological blockade of cannabinoid receptors in the central nervous system.