WHO wants to know more about Tamiflu

Sales of Tamiflu topped SFr1.5 billion in 2005 Keystone

The World Health Organization has called for urgent studies on Roche's flu drug Tamiflu to determine its effectiveness in the fight against bird flu in humans.

In a statement from its Geneva headquarters, the WHO said there was no clinical evidence of the anti-viral drug’s efficacy against the deadly H5N1 virus.

But it reaffirmed that Tamiflu should be used to treat suspected cases and to prevent the disease in healthcare workers or others who may have been exposed to infection.

The highly pathogenic strain of bird flu has killed about 100 people, more than half of those who have contracted it since late 2003.

Experts fear a pandemic if the disease evolves into a form that can be transmitted easily among humans.

Increased demand

Roche, which is based in the northern Swiss city of Basel, said on Thursday it was boosting output of Tamiflu, whose generic name is oseltamivir, by a third to meet increased demand from governments building stockpiles for a potential pandemic triggered by bird flu.

There is no direct clinical trial evidence that shows that oseltamivir is effective in human H5N1 disease because such studies have not yet been conducted, the WHO said in a statement.

Because the optimal dosage has not been resolved by clinical trials, and because H5N1 infections continue to have a high mortality rate, prospective studies are needed urgently to determine optimal dosing and duration of treatment for H5N1, it added.

The United Nations agency gave recommended doses for both treatment and prevention in adults and children above one year old. Its recommended treatment for adults suspected to have the disease is 75 mg twice a day for five days.

Studies required

The WHO commented that it was possible that severely ill patients might benefit from longer duration of therapy, for example 7-10 days, or perhaps higher doses (for example 300 mg/day), but prospective studies were required.

Children should be given the drug preventively for the same length of time in weight-adjusted doses.

For people with repeated or prolonged exposure such as healthcare workers or personnel involved in bird culls, pre-exposure courses, repeat post-exposure courses or continuous treatment may be necessary, it said.

The WHO recommendations are based on limited data from human outbreaks, animal models, and extrapolated results of trials in patients with ordinary influenza.

The agency said it would continue to monitor the situation but could not be held liable for damages arising from its advice.

In a related development, the Chinese government has given the go-ahead for clinical studies of Tamiflu produced by the Shanghai Pharmaceutical company.

Roche granted a licence to the firm for the complete production of the drug and the tests are to determine if the Chinese version is as effective as that produced by the Basel company.

swissinfo with agencies

Key facts

Roche produced 5.5 million treatments of Tamiflu in 1998.
Production rose to 27 million in 2004 and more than 50 million in 2005.
The forecast is for the number to rise to 150 million this year and 300 million in 2007.

In brief

The biotechnology company Gilead in the United States launched Tamiflu officially on the market in 1994.

Roche bought the production and marketing rights of the drug in 1996.

Tamiflu is an antiviral drug. It is currently considered the best defence against a human pandemic that could be started by avian flu. But its efficacy has not been proved clinically.

The medication could have secondary fatal consequences for children. The United States is to publish a study on this later in the year.