Dual sEH/FAAH Inhibitors as a Promising Therapeutic Strategy for the Treatment of Chronic Pain

Abstract

<b>Abstract ID 21553</b> <b>Poster Board 90</b> Chronic pain is the primary cause of disability worldwide. According to the National Institutes of Health, nearly 25.3 million Americans suffer from daily pain, and another 23.4 million Americans report significant pain. In this project we developed dual inhibitors, single small molecules that simultaneously inhibit two enzymes: soluble epoxide hydrolase (sEH) and fatty acid amide hydrolase (FAAH), both playing significant roles in pain and inflammation. Using an environmentally friendly four steps synthetic route, we were able to identify several very potent dual inhibitors, and one was tested in a rat model of acute inflammatory pain. We established a structure-activity relationship and discovered that fluoro- and chloro- groups in the ortho position are important for potent inhibition and are well-tolerated in the binding site of both enzymes. All dual inhibitors were significantly less potent on the mouse sEH enzyme than on human and rat enzymes. The sequence alignment of human, mouse, and rat enzymes shows high sequence similarity and contains many conserved amino acid residues located in the catalytic site of sEH; thus, we believe the species selectivity might be due to the different shapes of active sites and binding modes of analogs. Nonetheless, our findings indicate that modeling pain and other behaviors in rats are the best models to evaluate these dual inhibitors given the similar potencies at inhibiting both rat and human sEH enzymes. Finally, we evaluated the most potent compounds in human, mouse, and rat microsomal liver assays (MLA), which is a good predictor of in&nbsp;vivo metabolism and is an important tool in drug development. All tested compounds showed poor metabolic profiles in human, mouse, and rat MLA. In future work, we will try to use various medicinal chemistry approaches, such as the inclusion of deuterium atom, modifying labile functional groups, and deactivating aromatic rings in order to improve the microsomal stability. Dual sEH/FAAH inhibitors described here have the potential to be used as a promising novel non-opioid therapeutic strategy in pain management and our studies may provide a foundation for the future investigation of the benefits of using the dual ligand strategy in analgesia. Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number SC2GM135020