text: The first neuraminidase Inhibitors (NAIs) were synthesized  in the 1960s by Edmond et al., through an attempt to understand the catalytic mechanism of the neuraminidase enzyme. They discovered that N-substituted oxamic acids had enzyme inhibitory properties.  Then it was found that  the synthetic compound 2-deoxy-2,3-didehydro-N-acetylneuraminic acid (Neu5Ac2en or DANA) which is an analogue of N-acetylneuraminic acid (Neu5Ac), inhibits the release of virus progeny in tissue culture but no antiviral activity in animals was detected.
  In the early 1990s, the determination of biological crystal structure of influenza virus surface protein led to the discovery of the active site and provided the opportunities to discover and design new and specific inhibitors.