Development of a Small Molecule Inhibitor of Interleukin-18 for the Prevention of Vein Graft Failure or Other Inflammatory Diseases

Abstract

Overexpression of Interleukin-18 (IL18), a pleiotropic pro-inflammatory cytokine has been implicated in the early pathogenesis of intimal hyperplasia (IH), the leading cause of delayed graft failure. IL18 Binding Protein (IL18BP) is the natural inhibitor of IL18. Although recombinant IL-18BP is being clinically tested as a potential therapy to treat IL-18 associated conditions, a small molecule inhibitor of IL-18 may be clinically more amenable and feasible as a potential therapy to prevent IH development or other chronic inflammatory diseases. Fellow collaborators had previously performed comprehensive in silico screening of over 100,000 molecule fragments capable of binding IL18. Sixteen compounds were predicted to stably bind to either IL18 receptor binding sites on the IL18 molecule or other allosteric sites. For this study, in vitro IL18 signaling inhibition assays and microscale thermophoresis (MST) protein/ligand binding assays were conducted to discern which of those compounds most effectively bind and inhibit IL18 cell signaling, so that they may be used in further preclinical drug development. Results from the signaling inhibition assays indicated that 6 of the 16 compounds inhibit IL18 signaling comparably to the positive control IL18BP. Through a series of MST trials, these six also demonstrated significant binding affinity (Kd) with IL18. Interestingly the data suggest that some compounds interact with IL18 not only at different binding sites from one another, but some interact at multiple sites as well. The results provide evidence for the design of future toxicity and efficacy studies in vitro and in vivo focused on the most promising inhibitors.