Discovery and Development of Small-molecule Direct-acting Antivirals Targeting Ebola and Sudan Filoviruses

Project Summary Ebola virus (EBOV) and Sudan virus (SUDV) in the ebolavirus genus of filovirus family are highly dangerous pathogens that cause periodic outbreaks with death rates around 50%, threatening both global health and national security. While two drugs have been developed to treat EBOV, both are monoclonal antibodies that come with challenges, including high costs, limited effectiveness, and the need for injection and refrigeration. These requirements make it difficult to use these treatments effectively during outbreaks. Unfortunately, there are no approved treatments for SUDV. Developing oral medications for both viruses would be a game-changer, making treatments more accessible, cost-effective, and easier to distribute during emergencies. This research focuses on developing orally available small-molecule inhibitors that block the entry of EBOV and SUDV into human cells. The target for these inhibitors is the ebolavirus glycoprotein (GP), which guides the viruses to infect cells. Our team started by screening 4.7 billion chemical compounds and identified one that significantly blocked EBOV infection in laboratory tests. Using cryo-EM, we studied how this compound interacts with GP. We then improved the compound's effectiveness through structural modifications, creating versions that are 50 times more potent than the antiviral drug remdesivir. One of these compounds also showed promise against SUDV. The next step is to further improve these inhibitors and identify candidates that could become safe and effective treatments for both viruses. The project has three main goals: (i) Optimizing the compounds: We will refine two lead compounds to enhance their drug-like properties, such as improving their stability in the body, increasing their solubility, and ensuring they are safe for use in animals. These optimized compounds will then be tested for their ability to block EBOV and SUDV in laboratory settings, with the goal of preparing them for animal studies. (ii) Understanding how the compounds work: We will study how the compounds interact with GP to prevent viral entry into cells. Using cryo-EM and biochemical experiments, we will identify the mechanism by which these inhibitors block infection. We will also investigate whether the viruses could develop resistance to these drugs. (iii) Testing in animal models: Finally, we will evaluate the safety and effectiveness of the compounds in animal studies. This includes analyzing how the drugs are processed in the body, determining safe dosage levels, and testing whether they reduce mortality in mice infected with EBOV or SUDV. Successful candidates will then move on to larger preclinical trials in non- human primates, with the goal of eventually reaching human clinical trials. The ultimate goal of this research is to develop the first oral drug for EBOV, the first effective treatment for SUDV, and potentially a drug that works against all ebolaviruses. These advancements could transform how these deadly diseases are treated and significantly improve global outbreak response efforts.