Structure-Based Tetravalent Zanamivir with Potent Inhibitory Activity against Drug-Resistant Influenza Viruses

Zanamivir and oseltamivir are principal
influenza antiviral drugs
that target viral neuraminidase (NA), but resistant viruses containing
mutant NAs with diminished drug affinity are increasingly emerging.
Using the structural knowledge of both drug-binding sites and their
spatial arrangement on the homotetrameric NA, we have developed a
tetravalent zanamivir (TZ) molecule that exhibited marked increases
in NA binding affinity, inhibition of NA enzyme activity, and in vitro
plus in vivo antiviral efficacy over zanamivir. TZ functioned against
both human seasonal H3N2 and avian H7N9 viruses, including drug-resistant
mutants. Crystal structure of a resistant N9 NA in complex with TZ
explained the function, which showed that four zanamivir residues
simultaneously bound to all four monomers of NA. The design method
of TZ described in this study may be useful to develop drugs or ligands
that target proteins with multiple binding sites. The potent anti-influenza
activity of TZ makes it attractive for further development.