Novel Mu Opioid Receptor Modulators to Counteract Synthetic Opioids - PROJECT SUMMARY/ABSTRACT The current opioid crisis in the United States is primarily fueled by synthetic opioids such as fentanyl, its analogs, and non-fentanyl novel synthetic opioids (NSOs). These substances are highly potent mu opioid receptor (MOR) agonists, often labeled as super agonists, and are linked to side effects including euphoria, tolerance, constipation, and respiratory depression leading to opioid use disorders (OUD). Standard treatments, like naloxone (NLX), frequently prove insufficient, highlighting the pressing need for new and more effective treatments for OUD. However, a significant gap in knowledge remains regarding the behavioral pharmacology and activation mechanisms contributing to the extreme potency of these synthetic opioids. For the Avenir Award, I propose to develop MOR selective bitopic ligands that bind to both orthosteric and allosteric sites of the MOR. These ligands will serve as novel pharmacological probes and tools, potentially offering improved therapeutic outcomes. Our focus is on the 2-benzylbenzimidazole scaffold, also known as nitazene, whose derivatives were initially developed in the 1950s as potent analgesics but later abandoned due to their high addictive potential. Applying computational chemistry and molecular modeling, we demonstrated that nitazene agonists may bind to a novel positive allosteric site in addition to the orthosteric site in the active MOR, explaining their ultra-high potency at the MOR. We have designed, synthesized and characterized a series of nitazene analogs and identified novel chemical entities capable of antagonizing morphine, fentanyl, and the nitazene agonist etonitazene. Computational studies of these antagonists revealed that they may bind to a novel negative allosteric site as well as the orthosteric site in the inactive MOR. These interactions differ from the binding mode observed with NLX and explain at least in part NLX’s sub-optimal efficacy in counteracting the ultra-high potency synthetic opioids. Thus, our pilot studies have established the proof-of-concept that the 2-benzylbenzimidazole (nitazene) scaffold can be adapted to modulate the MOR function. This project aims to comprehensively investigate the nitazene scaffold by integrating computational modeling, synthetic chemistry, and cellular and behavioral pharmacology. The study will focus on understanding the structure-activity relationships (SAR) that govern the binding and function of nitazenes. This research represents a pioneering effort to study bitopic ligands as a strategic molecular approach. The outcomes of this project will establish the nitazene pharmacophore as a foundation for refining MOR function and deliver transformative insights and knowledge to the field. The project aligns well with the Avenir Award's goal of fostering forward-looking research, as it seeks to address urgent needs, including enhancing our understanding of novel mechanisms of receptor activation and inhibition, supporting the development of novel therapeutics for OUD, safer analgesics and proactive harm reduction strategies. Furthermore, the research holds the potential for broad applicability of bitopic ligand development across other class A G-protein coupled receptors (GPCRs).
