New millennium antivirals against pandemic and epidemic influenza: the neuraminidase inhibitors.

The mushroom shaped outer spike protein of influenza, neuraminidase, was first discovered nearly 60 years ago. Its importance in viral replication was soon recognised both at the point of viral release from the cell and also enabling passage of virus through nasal fluid to reach the cell. The enzyme active site was identified by x-ray crystallography, allowing an atomic study of interaction of enzyme with the sialic acid substrate. Analogues could then be identified and synthesized and became a focused target for antivirals. With the current threat of bioterrorism and the potential for the emergence of a new pandemic strain in the near future, efforts are underway to develop more potent second-generation anti-neuraminidase inhibitors with enhanced protective and therapeutic effects. Here we review older and newer neuraminidase inhibitors and the role that they will play in the fight against influenza in its epidemic and pandemic face.