EXPLORING KAPPA OPIOID RECEPTOR MUTATIONS IN IBD: FROM MOLECULAR PHARMACOLOGY TO DRUG DISCOVERY

Abstract Inflammatory bowel disease (IBD) is associated with severe abdominal pain. The kappa opioid receptor (KOR) was identified as valuable drug target due to its analgesic and anti-inflammatory effects. We recently demonstrated that KOR mutants E209A and Y312A exhibited intriguing signaling profiles: in response to the peptide-drug conjugate DNCP-β-NalA, the variant E209A (Emax=87.3%, normalized to U50,488) increased and Y312A (Emax n.d.) lost efficacy for β-arrestin recruitment compared to the KOR wildtype protein (Emax=29.7%). Further, both mutants exhibit similar potency as full agonist for Gαi (E209A pEC50= 10.6; Y312A pEC50= 9.0) compared to KOR wildtype (pEC50= 9.6) and dynorphin A(1-13) (pEC50=10.3) (1). The impact of disease-associated KOR mutations and ligand-specific signaling profiles remains poorly understood. To explore signaling efficacy of KOR mutants, we will analyze whole-genome sequencing data including clinical phenotypes to identify KOR variants in health and disease, with particular focus on IBD patients. Identified variants will be cross-referenced with population databases such as gnomAD to prioritize clinically relevant substitutions. To determine whether these variants alter KOR pharmacology in the context of IBD, we will employ BRET biosensor assays to screen and assess G protein activation vs. β-arrestin recruitment. A focused ligand panel will include FDA-approved therapeutics (e.g. difelikefalin, anrikefon, nalfurafine), experimental drug candidates (e.g., sialorphin), and in-house designed peptides (e.g. helianorphin-19, DNCP-β-NalA). Overall, this project will provide mechanistic insight into ligand-dependent signaling of KOR (and its amino acid variants) and their impact on drug response in IBD. Moreover, it will strengthen KOR as therapeutic target and demonstrate its translational relevance for the treatment of abdominal pain in IBD patients. 1. Muratspahić E, Deibler K, Han J, Tomašević N, Jadhav KB, Olivé-Marti AL, et al. Design and structural validation of peptide-drug conjugate ligands of the kappa-opioid receptor. Nat Commun. 2023 Dec 6;14(1):8064.