Tiller, K. | bioRxiv Science

bioRxiv2026

Development of semisynthetic blasticidin S analogs with potent and fast-killing anti-malarial activity

Protein synthesis represents an attractive target space for the development of anti-malarials with novel modes of action. Natural-product inhibitors of the eukaryotic 80S ribosome can have potent anti-malarial activity but are often poorly selective due to mammalian cytotoxicity. Blasticidin S (BlaS) is a microbially-produced natural product that broadly inhibits prokaryotic and eukaryotic protein synthesis by binding to the ribosomal peptidyl transferase center. In this study, we explored the potential for improving the anti-malarial potency and selectivity of the blasticidin S scaffold with semi-synthetic analogs that are modified at the C6 and C4 sites. The two best analogs were two orders of magnitude more potent than BlaS against Plasmodium falciparum drug-sensitive and -resistant lines while displaying low cytotoxicity towards mammalian cells. These analogs exhibited improved kinetics of inhibition of protein synthesis in cultured parasites and blocked the development of asexual stages expressing the plasmodial surface anion channel, a transporter required for nutrient acquisition and BlaS uptake. They also exhibited a dramatically improved speed of killing over BlaS. Molecular docking analysis revealed that these analogs are able to form more interactions with the P. falciparum ribosomal peptidyl transferase center than is BlaS, which is consistent with their increased potency. Together, these studies demonstrate the feasibility of generating BlaS analogs with potent anti-malarial activity and provide a roadmap for further development.

microbiology↗

bioRxiv2025

Auranofin Inhibits Hepatitis E Virus Replication Via Reactive Oxygen Species

Hepatitis E virus (HEV) causes roughly 20 million yearly global infections, and is associated with chronic hepatitis, neurological sequelae and pregnancy-related adverse outcomes that require antiviral therapeutic intervention. While there are currently no approved HEV-specific therapeutics, ribavirin and pegylated interferon, prescribed off-label, are the current standard of care. However, ribavirin resistance and toxicity highlight the unmet clinical need to identify safer, HEV-specific antivirals. Auranofin, an FDA-approved anti-rheumatic drug, displays antiviral activity against several viruses. Therefore, we investigated auranofins potential as an antiviral and its mechanism of action against HEV. We demonstrated that auranofin displays dose-dependent antiviral activity against two genotypes of HEV that cause a significant proportion of human disease, as well as against a ribavirin treatment failure-associated mutant. Because auranofin is known to increase reactive oxygen species (ROS), we investigated the antiviral mechanism of action via treatment with ROS inhibitors. ROS inhibitors reversed auranofin-mediated ROS promotion and antiviral activity, suggesting the observed antiviral effects are mediated by ROS. Furthermore, treatment with a different ROS promotor, D-amino acid oxidase (DAAO), also displays antiviral activity against HEV, which was also reversed by treatment with a ROS inhibitor, suggesting that ROS accumulation alone is antiviral. We also demonstrated that combined treatment with auranofin and ribavirin exhibits synergistic antiviral activity in vitro, which supports repurposing auranofin as an antiviral against HEV, potentially in combination with ribavirin. Overall, this study has important implications in repurposing auranofin as an antiviral against HEV and in delineating the mechanism of action against HEV via ROS. ImportanceHepatitis E virus (HEV) lacks approved antiviral therapies, and off-label treatments are limited by toxicity and emerging resistance. This study identifies the FDA-approved drug auranofin as an effective in vitro inhibitor of HEV, including two globally relevant human-associated genotypes and a ribavirin treatment failure-associated mutant. Auranofins activity highlights the therapeutic potential of host-targeting antivirals, particularly those that promote the generation of reactive oxygen species, in treating HEV infection. These findings support further in vivo investigations of auranofin as a treatment for HEV and suggest that modulating host redox pathways by promoting reactive oxygen species may represent a promising strategy for broad-spectrum antiviral development.

microbiology↗