Old Flu Drug, New Hope

A QUANTUM OF SCIENCE

When vaccines fail, antiviral drugs might make the difference between life and death

The seasonal flu vaccine is already being administered and a special vaccine targeting H1N1 will soon follow, but for some people a vaccine may not be enough. Children, the elderly and immunocompromised individuals are at high risk for complications from influenza. For those already infected a vaccine does no good, but fortunately, antiviral medications are available when the flu turns life-threatening.

The most well-known anti-influenza drug is TamiFlu (its official name is Oseltamivir). TamiFlu is taken orally, usually for a five-day course of treatment. Approved in 1999, it has been used to treat 50 million people to date. Currently, TamiFlu is usually reserved for serious, potentially life-threatening cases in an attempt to prevent the flu virus from mutating into a form resistant to the drug. Indeed, five cases of TamiFlu-resistant H1N1 have already been reported but overall the rate of resistance flu cases remains low (around 1.2%).

Recently, a drug called Peramivir has been developed and is on the fast track to approval by the FDA. This is not a new drug – it was abandoned in 2001 by Johnson and Johnson due to low oral availability – but in 2005 concerns over Avian flu caused drug-makers to reexamine the compound and begin testing it as an intravenous medication. Recent studies show a single intravenous dose of Peramivir is as effective as the full five-day course of oral treatment with TamiFlu. Additionally, adverse drug reactions were less common with Peramivir.

Both TamiFlu and Peramivir act by inhibiting the same viral enzyme, neuraminidase. This enzyme allows viral particles to escape infected cells and go out in the bloodstream where they can find new cells to infect. When TamiFlu or Peramivir inhibit the viral neuraminidase, viral particles remain trapped inside infected cells until the body’s immune system can respond, usually with macrophages (literally "big eaters") that engulf the infected cell and digest it, destroying the viral particles along with the cell.

Additional advantages of Peramivir include its single-dose effectiveness. There have been reports of individuals hoarding TamiFlu pills and threatening the supply of the drug, but that cannot happen with a drug which can only be administered intravenously.


For more information:

Study: New Drug Fights Flu as Well as TamiFlu

TamiFlu (Wikipedia article)

TamiFlu-resistant H1N1 cases reported


© AQOS / P. Smalley (2009)
Reproduction with attribution is appreciation