Eph-Ephrin Tetramerization Inhibitors Target Bidirectional Signaling to Combat Pain and Addiction

Eph receptors and Ephrin ligands are a large highly conserved family of interacting membrane-anchored molecules that form dimers, tetramers, and tetramer superclusters to become activated and signal upon cell-cell contact. While most noted for their ability to transduce bidirectional phosphotyrosine signals in development, certain Ephs and Ephrins also become overexpressed and participate in pathological situations, including EphB1 in chronic pain/addiction and EphB2 in fibroinflammatory disorders and cancer. We searched for small molecules that disrupt EphB-EphrinB receptor-ligand interactions and discovered compounds with submicromolar activity that specifically inhibit formation of the tetramer. Compounds effectively target tetramer-driven EphB1-EphrinB2 and EphB2-EphrinB2 interactions, while showing less action towards the more dimer-driven EphB4-EphrinB2 interaction. They are orally available, exhibit drug-like qualities to reduce both EphB forward and EphrinB reverse signaling, and act to blunt inflammatory pain and opioid withdrawal behaviors. Tetramer inhibitors thus present a novel way to target Eph-Ephrin macromolecular interactions and counter pathologies caused or exacerbated by excessive bidirectional signaling.