[CAS NO. 139110-80-8]  Zanamivir

Zanamivir, a novel neuraminidase inhibitor, is effective at decreasing replication of the virus in vitro. Zanamivir results in reduced sensitivity in influenza A/H1N1 variant His274Asn, as well as His274Gly, His274Ser, and His274Gln. Zanamivir blocks influenza neuraminidase and prevents the cleavage of sialic acid residues, thus interfering with progeny virus dispersement within the mucosal secretions and reducing viral infectivity. Zanamivir prevents hemadsorption and fusion of persistently infected cells with uninfected cells. Zanamivir reduces the number (but not the area) of plaques if present only during the adsorption period and reduces plaque area (but not number) if added only after the 90-min adsorption period in plaque assays. Zanamivir also reduces the area of plaques formed by a neuraminidase-deficient variant, confirming that its interference with cell-cell fusion is unrelated to inhibition of neuraminidase activity. Zanamivir has no effect on hemadsorption but does inhibit HA2b-red blood cell fusion, as judged by both lipid mixing and content mixing.