December 22, 2005
Signs of Tamiflu Resistance No Cause for Alarm: WHO
By Stephanie Nebehay
GENEVA -- Signs that the H5N1 bird flu virus may be developing resistance to frontline drug Tamiflu in some patients are not necessarily a cause for alarm, a senior World Health Organization official said on Thursday.
"Whenever you use any kind of drugs, antivirals or antibiotics, you expect to see resistance develop in organs. Finding some resistance in and of itself is not surprising and is not necessarily alarming," Fukuda told Reuters.
But more research was needed on optimal doses and length of treatment for people infected with the deadly virus, to limit the chances of resistance becoming more widespread, he added.
Findings published in the New England Journal of Medicine showed that four of eight patients treated in Vietnam for bird flu infections had died despite the use of Tamiflu.
"It just points out the need for more information ... What really is critical is understanding whether the way we are using the drugs contributes to that (resistance)," Fukuda said.
According to the study, tests showed that in two of the patients, the virus had developed resistance to Tamiflu, which is made by Swiss drugs firm Roche. For the other two, treatment may simply have started too late.
Roche shares were down 0.8 percent at 1130g.
TOO SMALL DOSES
Using too small doses, or for too short a time, can contribute to resistance developing, according to Fukuda, who noted that the Vietnam study had been very small.
"Using an antiviral or antibiotic in doses that are less than optimal helps set up conditions which make it easier for the bugs we are targeting to become resistant," Fukuda said.
"We have to monitor the situation to see whether resistance becomes a big problem or not," the American added.
Tamiflu remained an "excellent choice" among a limited number of antivirals available against the deadly virus, the WHO official said.
GlaxoSmithKline and Biota's Relenza, known generically as zanamivir, is an alternative to Tamiflu and has been shown to be active against Tamiflu-resistant virus.
But Relenza must be inhaled, making it problematic for patients with respiratory conditions such as asthma.
Glaxo hopes eventually to develop an injectable form of the medicine to overcome this limitation, but a spokeswoman in London said it was unlikely to be ready for at least two years.
Two more human deaths from bird flu in Indonesia were confirmed on Thursday, taking the known global total to 73, while cases including survivors would rise to 141. All the deaths so far have been in Asia.
Experts fear the virus will mutate into one that can be passed from human to human, rather than from fowl to people, and that such a mutation might spark a pandemic killing millions.
"Given the current situation and the need to be as prepared as possible for the pandemic, antivirals remain a really important part of our preparations. This paper does not call into question whether we should be doing that," Fukuda said.
Options for antivirals, in terms of both stockpiling and treatment of patients infected with the virus, remain "relatively limited," according to Fukuda.
On balance, a class of drugs known as neuraminidase inhibitors is the best bet, with Tamiflu an "excellent choice" among them, he added.
Roche announced last August that the drugmaker was donating enough Tamiflu to WHO to threat three million people. About one million treatment courses are in place, with the remainder to follow in coming months, according to WHO officials.
--- with additional reporting by Ben Hirschler in London
(BIRDFLU-TAMIFLU-WHO; Reporting by Stephanie Nebehay; Editing by Patrick Worsnip; Reuters Messaging: [email protected]))