The Importance of Hydrogen Bonding and Aromatic Stacking to the Affinity and Efficacy of Cannabinoid Receptor CB₂Antagonist, 5-(4-chloro-3-methylphenyl)-1-[(4-methylphenyl)methyl]-N-[(1S,2S,4R)-1,3,3-trimethylbicyclo[2.2.1]hept-2-yl]-1H-pyrazole-3-carboxamide (SR144528)

Abstract

Despite the therapeutic promise of the sub-nanomolar affinity cannabinoid CB2 antagonist, N-[(1S)-endo-1,3,3-trimethylbicyclo[2.2.1]heptan2-yl]-5-(4-chloro-3-methylphenyl)-1-[(4-methylphenyl)methyl]-1H-pyrazole-3-carboxamide (SR144528, 1), little is known about its binding site interactions and no primary interaction site for 1 at CB2 has been identified. We report here the results of Glide docking studies in our cannabinoid CB2 inactive state model that were then tested via compound synthesis, binding and functional assays. Our results show that the amide functional group of 1 is critical to its CB2 affinity and efficacy and that aromatic stacking interactions in the TMH5/6 aromatic cluster of CB2 are also important. Molecular modifications that increased the positive electrostatic potential in the region between the fenchyl and aromatic rings led to more efficacious compounds. This result is consistent with the EC-3 loop negatively charged amino acid, D275 (identified via Glide docking studies) acting as the primary interaction site for 1 and its analogs.

Synthesis, biological activity and molecular modeling of new biphenylic carboxamides as potent and selective CB2 receptor ligands

“…As regards docking of SR144528, the selected binding mode resulted in a pose (Fig. 3a) in good agreement with that previously reported for the same compound [46], where the carboxamide oxygen hbonds to both K 3.28 and S 2.60 , the pyrazole ring N2 atom h-bonds to the S 7.39 side chain, the 3-methyl-4-chloro-phenyl establishes hydrophobic contacts with T 3.33 and W 5.43 residues, and the pmethyl-benzyl moiety forms further hydrophobic contacts with TM6 residues (V 6.51 , L 6.54 , M 6.55 ). Docking of the N-cycloheptyl-1- [32] showed a slight different binding mode (Fig.…”

Aromatic interactions at the ligand–protein interface: Implications for the development of docking scoring functions

“…For instance, docking of a series of agonists to the binding pocket of the homology model of the serotonin 5-HT 2C G protein-coupled receptor with the PatchDock server [67] produced ligand conformations interacting with tryptophan and phenylalanine residues through parallel and perpendicular aromatic stacking [68] . Another example is a molecular modeling study conducted with Glide [69] for subnanomolar affinity antagonists of the cannabinoid receptor CB 2 [70] . Docking calculations revealed a number of parallel and perpendicular aromatic contacts between chloromethylphenyl and methylbenzyl rings of the compounds and a cluster of aromatic residues in CB 2 , suggesting that π-π interactions are critical to the efficacy of these antagonists.…”

Synthesis, Pharmacological Evaluation, and Docking Studies of Novel Pyridazinone‐Based Cannabinoid Receptor Type 2 Ligands

“…[23] This study suggested that the SR144528 amide functional group is important for interacting with CB 2 R. In addition, aromatic stacking interactions in the transmembrane helix (TMH) 5-6 aromatic cluster werer evealed to be crucial to the SR144528-CB 2 Rc omplex. [23] This study suggested that the SR144528 amide functional group is important for interacting with CB 2 R. In addition, aromatic stacking interactions in the transmembrane helix (TMH) 5-6 aromatic cluster werer evealed to be crucial to the SR144528-CB 2 Rc omplex.…”

“…[23] This study suggested that the SR144528 amide functional group is important for interacting with CB 2 R. In addition, aromatic stacking interactions in the transmembrane helix (TMH) 5-6 aromatic cluster werer evealed to be crucial to the SR144528-CB 2 Rc omplex. [23][24][25][26] This homology model wasp re-equilibrated in as tearoyl-docosahexaenoylphosphatidylcholine( SDPC) bilayer for 300 ns to allow it to adjust in al ipidic environment [23] (see the Experimental Section). [24] In the current study,G lide docking studies revealed that the novel pyridazinones reported hereb ind in as imilar orientation as the 1,8-naphthyridin-2(1H)-one-3-carboxamides.…”

“…Here aT rp residue forms an aromatic stacking interaction with Y5.39, influencing the extracellular positions of TMH3-4-5. [23,24,26] Compound 22 was flexibly docked using Glide (version 7.5, Schrçdinger) and the dock with the best Glide score, as ranked by Emodel, was chosen. This CB 2 Rm odel has been tested using results from substituted cysteine-accessibility studies to identify bindingpocket-facing residues, [46,47] from mutation studies of key ligand interactions sites, [46][47][48][49] and from covalent labeling studies of CB 2 R that support al ipid-entry pathway for CB 2 Rl igands.…”