Deconstructing natural products to develop synthetic small molecule attachment inhibitors with broad spectrum antiviral activity

Abstract

The continuous emergence of new viruses and the number of viruses that are each highly consequential for few people raise a need for broad spectrum antivirals. Most human and emerging viruses first attach to cellular glycosaminoglycans (GAG) or sialylated glycans (SG), a potential target for broad spectrum antivirals. Attachment to the former is through polar interactions between the negatively charged glycans and positively charged domains in virion proteins and typically inhibited by negatively charged polymers. Attachment to the latter is through specific interactions at binding pockets and inhibited by molecules that bind to these pockets. Surprisingly, EGCG inhibits viruses that attach to GAG and SG. However, it does so with widely differing potencies, is not a pharmacologically desirable molecule, and is limited by solubility. We tested whether it was possible to develop small synthetic molecules to inhibit viruses that attach to SG or GAG. We first identified the EGCG moieties responsible for the antiviral activity. The two polyhydroxylated phenyl groups were essential while the central benzopyran linker was not. We thus designed a series of gallate compounds to explore the minimal pharmacophore required for broad-spectrum antiviral activity. By exploring the linkers and number of galloyls, we identified small molecule inhibitors of herpes simplex virus 1, influenza A virus, and the coronaviruses hCoV OC43 and SARS-CoV-2. These compounds have low micromolar to submicromolar potency and no limiting cytotoxicity. These molecules are still not pharmacologically optimized and limited by solubility, but they define a minimal pharmacophore that confers broad spectrum antiviral activity. ImportanceThe SARS-CoV-2 pandemic demonstrated the importance of antivirals in managing emerging viruses. Although vaccines were successfully developed in less than two years, there was resistance to vaccination while infected or sick people were far more willing to take antivirals. It is impossible to develop antivirals specific for unknown viruses, but broad spectrum antivirals could control viral spread until more specific and potent drugs are developed. Human pathogenic and emerging viruses commonly attach to glycans, providing a target for broad spectrum antivirals. However, inhibitors of attachment to glycosaminoglycans do not typically inhibit viruses attaching to sialylated glycans, and vice-versa. We had found that EGCG has the unique property of inhibiting viruses that attach both glycans, with quite different potencies. Here, deconstructed a natural compound, EGCG, to identify the moieties responsible for its antiviral activity to then produce broad spectrum antiviral compounds against established and emerging viruses that attach to either glycan.