Worldwide, there are up to 500,000 flu related deaths annually. In 1919, the Spanish flu pandemic killed more people than World War I.
The most commonly used anti-viral drugs in use currently are Tamiflu and Relenza. Their effectiveness in combatting flus are however, debatable. Having come to market in the 1990s, they are very widely implemented. Tamiflu was used during the Swine flu pandemic of a few years ago. This however, is precisely the problem. These two treatments are rapidly losing their effectiveness. The more a virus is exposed to a drug, the better it gets at resisting it. Scientists are always on the look-out for an anti-viral which works by a different mechanism, therefore by-passing the resistance of the virus.
In the last few weeks however, there have been reports that researchers in Canada, the USA and Australia have discovered a new class of anti-flu drug. Neuraminadase is an enzyme responsible for severing the connection between virus and human cell, so that it can move on and infect others.
Tamiflu and Relenza both work by inhibiting this. The new drugs would act in a similar, but more permanent fashion. It has been described like a ‘broken key stuck in a lock’ by Steve Withers of the University of British Columbia.
The natural substrate of neuraminidase is sialic acid, which it binds to in order to activate this transmission mechanism. The new drugs are said to act like a ‘trojan horse’ in that they would closely resemble sialic acid, thereby blocking the activity of the enzyme once bound. The virus cannot mutate to prevent this inhibition because it would hamper the essential catalytic work of the enzyme.
Scientists are also looking into making the new drugs more orally available – in other words, retaining function while allowing the drug to be swallowed and pass through the GI tract.
These new developments are still 6-7 years from the market, but the prospect of having another line of attack in the battle against flu is a welcome one. These new developments could be an excellent last resort.