Alireza Sharafshah - Cellular and Molecular Research Center, Faculty of Medicine, Guilan University of Medical Sciences, Rasht, Iran.
Parvaneh Keshavarz - Cellular and Molecular Research Center, Faculty of Medicine, Guilan University of Medical Sciences, Rasht, Iran.

Introduction: Previous studies demonstrated that the AM-251 directly bind to Mu-Opioid Receptors (MORs). Here, we developed an analog of AM-251 through in silico procedures to find a more effective compound with better affinity for future studies of MOR inhibitors in analgesia.Methods: The tertiary structures of human MOR protein was modeled by Swiss Model, PS2, and Phyre2 online softwares (template PDB ID: 4DJH). Then, best models (from Phyre2) were built after energy minimization by Swiss-PdbViewer DeepView ver. 4.1.0 software. The structures of designed models were then validated using RAMPAGE (95.7% in favored and allowed regions) and ProSA softwares (z-score=-2.33). 45 new analogs of AM-251 were created by adding OH and CH3 substituents to various atoms of AM-251. To prepare the ligand for docking, energy minimization of ligands was performed using Hyperchem ver. 8.0.8. Active site of OPRM1 was predicted by COACH. First, all 45 molecules were docked through Autodock vina in PyRx tool, and then best molecule with lowest energy binding docked again by Autodock vina ver. 4.2. Results: We found that C27 had potential role to be changed by substituents like CH3 and OH. The best conformation was CH3 substituent added to the C27 of AM-251 with binding energy of -9.05 kcal/mol and 2 hydrogen bonds with ASN371 compared to AM-251 Energy binding of -7.9 kcal/mol and no H-bond formation.Conclusion: Suggested in silico synthesized (1‐(2,4‐dichloro‐3‐methylphenyl)‐5‐(4‐iodophenyl)‐4‐methyl‐N‐(piperidin‐1‐yl)‐1H‐pyrazole‐3‐carboxamide) can be an analog candidate of AM-251 as a specific inhibitor of MOR but this needs both chemical and clinical validations.

MOR, AM-251, Homology Modeling, Docking.