Zanamivir is a selective inhibitor of influenza A and B virus neuraminidases with IC50 values of 0.64-7.9nM [1].
Influenza A and B viruses are negative-strand RNA viruses. Neuraminidase is one of the two glycoproteins present on the surface of the virus. It is important to the pathogenicity and infectivity of the virus. The neuraminidases inhibitor, zanamivir, is a sialic acid analogue. It inhibits neuraminidases to cleave sialic acid on the surface of host cells and influenza viral envelope. In the in vitro assay, zanamivir suppresses the growth of influenza A and B viruses with IC50 values ranging from 5nM to 14nM for laboratory-passaged strains and from 20nM to 16μM for clinical isolates. In animal models infected with influenza A and B, treatment of zanamivir reduces the mortality and viral titres in lung homogenates and improves lung consolidation scores [1].
References:
[1] Elliott M. Zanamivir: from drug design to the clinic. Philos Trans R Soc Lond B Biol Sci, 2001, 356(1416): 1885-93.