Zanamivir is a potent and selective inhibitor of influenza A and B virus neuraminidases with IC50 values of 0.95 nM and 2.7 nM, respectively. It interacts with a group of amino acids in the active site of neuraminidase, that are conserved in all influenza A and B strains. Zanamivir blocks the action of neuraminidase, which blocks the cleavage of sialic acid on the cell receptors, thus preventing release and spread of the newly formed virions. MW: 332.31. Purity ≥98% by HPLC