Novel Electrophilic and Photoaffinity Covalent Probes for Mapping the Cannabinoid 1 Receptor Allosteric Site(s)

Abstract

Undesirable side effects associated with orthosteric agonists/antagonists of cannabinoid 1 receptor (CB1R), a tractable target for treating several pathologies affecting humans, have greatly limited their translational potential. Recent discovery of CB1R negative allosteric modulators (NAMs) has renewed interest in CB1R by offering a potentially safer therapeutic avenue. To elucidate the CB1R allosteric binding motif and thereby facilitate rational drug discovery, we report the synthesis and biochemical characterization of first covalent ligands designed to bind irreversibly to the CB1R allosteric site. Either an electrophilic or a photoactivatable group was introduced at key positions of two classical CB1R NAMs: Org27569 (1) and PSNCBAM-1 (2). Among these, 20 (GAT100) emerged as the most potent NAM in functional assays, did not exhibit inverse agonism, and behaved as a robust positive allosteric modulator of binding of orthosteric agonist CP55,940. This novel covalent probe can serve as a useful tool for characterizing CB1R allosteric ligand-binding motifs.

Novel analogs of PSNCBAM-1 as allosteric modulators of cannabinoid CB1 receptor

“…Since the discovery of PSNCBAM-1, some SAR studies 35–37 showed that CB1R allosteric modulators with improved affinity, efficacy and potency, could be generated from PSNCBAM-1 template. With the aim to extend the knowledge about the structural requirements of PSNCBAM-1 template as CB1R allosteric modulator, in this work we studied some derivatives designed by introducing various modifications on PSNCBAM-1 structure.…”

“…In an in vivo study of acute feeding model, PSNCBAM-1 showed to decrease food intake and body weight. 27 Several analogs of PSNCBAM-1 35–37 have been reported and structure-activity relationship studies showed that alkyl substitution at the 2-aminopyridine moiety is important for CB1R allosteric modulation; in particular, tertiary amine substitution is more favorable than secondary. Furthermore, the 4-position on the phenyl group tolerates structural modifications, but electron-withdrawing groups such as cyano or CF 3 are preferred, 35 and the substitution of the urea group with other spacers such as carbamate, methylated ureas or cyclic ureas, reduces the activity.…”

Synthesis and in vitro antiproliferative effect of isomeric analogs of cyclobrassinin phytoalexin possessing 1,3-thiazino[5,6-b]indole-4-one skeleton

“…4-(Ethoxycarbonyl)phenyl-substituted thiourea 9b gave the excepted 2-[4-(ethoxycarbonyl)phenylimino]-1,3-thiazino [5,6-b]indole-4-one (11) in good yield upon treatment with the bromide reagent applied above. For 3,4,5-trimethoxyphenyl-substituted 9c, the preferable reaction path in the Hugerschoff reaction was the formation of thiazole ring system 2-(indol-2-carbonylamino)-5,6,7-trimethoxy-benzothiazole (12). …”

“…The crystalline residues were triturated with acetone (9a-c), filtered off and purified as indicated. (12). To an intensively stirred suspension of thiourea derivatives 9a-c (0.7 mmol) in dichloromethane (20 mL), phenyltrimethylammonium tribromide (0.26 g, 0.69 mmol) was added in one portion at room temperature.…”

“…Compounds containing this pharmacophore, therefore, can be found in varied biologically active compounds. Certain derivatives, which target allosteric modulation of cannabnoid receptor 1 (CB1), 12 glycogene phosphorylase inhibitors, 13 neurotensin (NT) (8)(9)(10)(11)(12)(13) 31 ), may act as apoptosis inducers 32 and potential DNA-intercalating compounds 33 (like duocarmycin A). In addition, they exert promising and remarkable in vitro antiproliferative effects.…”