Most current approaches for antiviral therapeutics target the virus specifically and directly, but that strategy can be difficult in the face of a rapdly evolving viral genome and consequent pathogen resistance. An alternative approach would be to enhance the host innate immune response, which should prove efficacious to a broad range of viruses, including new and emergent strains. Based on clinical and pre-clinical observations, we provided evidence that the interferon (IFN) signaling system could be genetically engineered for increased efficiency and thereby better protect against RNA virus infection in vitro and in viv without toxicity. We therefore proceeded to identify small molecules that interact with the IFN signaling system to mimic this antiviral benefit and thereby provide therapeutic leads for further development. We developed a high- throughput screening (HTS) strategy using a cell-based phenotypic screen for increased IFN-stimulated response element (ISRE) activity to identify small molecules that enhance the IFN signaling pathway. A pilot screen against a collection of already approved or approvable compounds provided proof-of-concept by yielding hit compounds that enhanced the IFN signaling pathway and controlled viral level in vitro. We subsequently screened two other chemical libraries, and the high resolution and reproducibility of the data allowed for a novel combined analysis with the eventual selection and validation of 75 confirmed hits. Structural analysis showed 11 clusters, including one containing several statins. Functional analysis showed that statins indeed possess potent IFN enhancing and antiviral activity (including common RNA respiratory viruses), and this action may be independent of 3-hydroxy-3methylglutaryl-CoA (HMG-CoA) reductase (HMGCR) inhibition to explain why statin potency on sterol synthesis does not correlate with antiviral potency. We therefore hypothesize that developing compounds to enhance endogenous IFN signaling will lead to next- generation antiviral drugs with a novel mechanism of action and propose to achieve this goal with the following specific aims: 1. Determine whether the IFN-enhancing property of statins is independent of their conventional role in blocking the sterol synthesis pathway. 2. Determine the target of statins within the IFN signaling pathway that is required for an antiviral effect to further define structure-activity relationship (SAR) and further optimize analog selection. 3. Define and validate statin effect on RNA virus infection in cell and in animal models. 4. Use our established drug discovery and development system to discover and develop additional types of compounds with IFN signal enhancing and antiviral activity. We expect these studies to provide pre-clinical candidates for use as next-generation antiviral therapeutics, particularly targeting common RNA respiratory viruses.
Viral infections are a leading cause of new, emergent, and epidemic infectious diseases and a primary candidate for bioterrorist threats. However, there is an extremely limited capability for antiviral therapeutics that act rapidly and effectively to trea and/or prevent these types of infections. The present project aims to develop the next generation of antiviral drugs with the capability of broad and safe effectiveness against viral infections.