# Synthesis and Pharmacological Characterization of a Novel Cannabinoid Receptor 1 Antagonist

## TL;DR

This study develops a new CB1 receptor antagonist, UVI3502, with potential for studying the endocannabinoid system and treating brain-related conditions.

## Contribution

The paper introduces UVI3502, a novel CB1 antagonist with a planar and rigid structure for improved pharmacological properties.

## Key findings

- UVI3502 showed high affinity for CB1 receptors in the rat cortex.
- UVI3502 acts as a CB1 antagonist, blocking agonist-evoked stimulation.
- Computational analysis supports UVI3502's interaction with the inactive state of CB1.

## Abstract

The endocannabinoid
(eCB) system regulates several brain functions
and is implicated in numerous conditions affecting the brain. Thus,
the pharmacological blockade of cannabinoid receptors has a therapeutic
potential but produces severe psychiatric side effects. Hence, new
cannabinoid compounds with different pharmacological profiles are
needed to potentially minimize this toxicity. The objective of this
study, featuring original chemical insights, pharmacological analysis,
and robust computational methods, was to synthesize and characterize
a series of novel antagonists/inverse agonists of cannabinoid receptors.
To do so, we first synthesized and then screened 11 novel compounds
for affinity for cannabinoid receptors. After that, we characterized
in depth the pharmacological profile of the most promising one, UVI3502,
which showed affinity for two [3H]­CP55,940 binding sites
(IC50Hi 0.026 ± 0.43 nM and IC50Lo 772
± 49.40 nM, R
2 = 0.59) in the rat
cortex. Binding assays performed in membranes overexpressing cannabinoid
receptors 1 and 2 (CB1 and CB2) confirmed moderate
affinity for both receptor subtypes, about 10-fold higher for the
first one, indicating limited receptor subtype specificity. In key
brain areas from the rodent brain, which have a much higher CB1 receptor density than CB2, the affinity of UVI3502
was further studied with neuroanatomical specificity by autoradiography.
Functional [35S]­GTPγS assays demonstrated that UVI3502
behaved as an antagonist of CB1 receptors, blocking the
stimulation evoked by the potent cannabinoid receptor agonist CP55,940.
The in silico characterization of the binding to the CB1 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. Hence, we synthesized and characterized UVI3502 as
a novel antagonist of CB1, making it a new pharmacological
tool for the study of the eCB system and for blocking cannabinoid
receptors in the central nervous system.