rupintrivir and favipiravir

Enterovirus 71 (EV-A71) is a major causative pathogen of hand, foot, and mouth disease (HFMD) epidemics. No antiviral therapies are currently available for treating EV-A71 infections. Here, we selected five reported enterovirus inhibitors (suramin, itraconazole [ITZ], GW5074, rupintrivir, and favipiravir) with different mechanisms of action to test their abilities to inhibit EV-A71 replication alone and in combination. All selected compounds have anti-EV-A71 activities in cell culture. The combination of rupintrivir and ITZ or favipiravir was synergistic, while the combination of rupintrivir and suramin was additive. The combination of suramin and favipiravir exerted a strong synergistic antiviral effect. The observed synergy was not due to cytotoxicity, as there was no significant increase in cytotoxicity when compounds were used in combinations at the tested doses. To investigate the potential inhibitory mechanism of favipiravir against enterovirus, two favipiravir-resistant EV-A71 variants were independently selected, and both of them carried an S121N mutation in the finger subdomain of the 3D polymerase. Reverse engineering of this 3D S121N mutation into an infectious clone of EV-A71 confirmed the resistant phenotype. Moreover, viruses resistant to ITZ or favipiravir remained susceptible to other inhibitors. Most notably, combined with ITZ, rupintrivir prevented the development of ITZ-resistant variants. Taken together, these results provide a rational basis for the design of combination regimens for use in the treatment of EV-A71 infections.

Topics: Amides; Amino Acid Sequence; Animals; Antiviral Agents; Binding Sites; Cell Line, Tumor; Chlorocebus aethiops; Drug Combinations; Drug Resistance, Viral; Drug Synergism; Enterovirus A, Human; Humans; Indoles; Isoxazoles; Itraconazole; Molecular Docking Simulation; Mutation; Myoblasts; Phenols; Phenylalanine; Protein Binding; Protein Interaction Domains and Motifs; Protein Structure, Secondary; Pyrazines; Pyrrolidinones; Sequence Alignment; Sequence Homology, Amino Acid; Suramin; Valine; Vero Cells; Viral Nonstructural Proteins; Virus Replication

Potent and safe inhibitors of norovirus replication are needed for the treatment and prophylaxis of norovirus infections. We here report that the in vitro anti-norovirus activity of the protease inhibitor rupintrivir is extended to murine noroviruses and that rupintrivir clears human cells from their Norwalk replicon after only two passages of antiviral pressure. In addition, we demonstrate that rupintrivir inhibits the human norovirus (genogroup II [GII]) protease and further explain the inhibitory effect of the molecule by means of molecular modeling on the basis of the crystal structure of the Norwalk virus protease. The combination of rupintrivir with the RNA-dependent RNA polymerase inhibitors 2'-C-methylcytidine and favipiravir (T-705) resulted in a merely additive antiviral effect. The fact that rupintrivir is active against noroviruses belonging to genogroup I (Norwalk virus), genogroup V (murine norovirus), and the recombinant 3C-like protease of a GII norovirus suggests that the drug exerts cross-genotypic anti-norovirus activity and will thus most likely be effective against the clinically relevant human norovirus strains. The design of antiviral molecules targeting the norovirus protease could be a valuable approach for the treatment and/or prophylaxis of norovirus infections.

Topics: Amides; Antiviral Agents; Cell Line; Cysteine Endopeptidases; Cytidine; Drug Combinations; Drug Synergism; Hepatocytes; Humans; Isoxazoles; Molecular Docking Simulation; Norwalk virus; Papain; Phenylalanine; Pyrazines; Pyrrolidinones; Replicon; RNA-Dependent RNA Polymerase; Valine; Viral Proteins; Virus Replication