More evidence bird flu can evade drug:
report
Wed Dec 21, 2005 6:21 PM ET
By Maggie Fox, Health and Science Correspondent
WASHINGTON (Reuters) - Doctors in Vietnam reported on Wednesday
they had found more evidence that the H5N1 bird flu virus can
quickly mutate into a form that resists the effect of Roche AG's
frontline drug Tamiflu.
Four of eight patients treated in Vietnam for bird flu infections
died despite the use of Tamiflu, Dr. Menno de Jong of the Oxford
University Clinical Research Unit at the Hospital for Tropical
Diseases in Ho Chi Minh City and colleagues wrote in the New
England Journal of Medicine.
Tests showed that in two of the patients, the virus had become
resistant to Tamiflu. And in one patient, the drug was used very
early on, as is recommended.
"It is becoming clear that to treat avian flu with neuraminidase
inhibitors (such as Tamiflu) we are going to need higher doses and
longer course of treatment for it to work," said Dr. Anne Moscona,
an expert in pediatric viral diseases at Weill Medical College of
Cornell University, New York.
She and other experts said the findings showed that such drugs must
be preserved carefully and used properly.
The H5N1 influenza virus has killed 71 people in Indonesia,
Thailand, Vietnam, China and Cambodia since 2003.
The H5N1 strain is difficult for people to catch. However, experts
fear it could evolve into a form that could pass easily from human
to human, causing a pandemic that could kill millions.
The researchers and outside experts said the report concerned only
a few people and stressed that more study is needed. Of the 138
people known to have been infected with H5N1, 31 have been treated
with Tamiflu, Roche says.
"This currently is not a pandemic strain," Dr. David Reddy,
Influenza Pandemic Taskforce Leader for Roche, told reporters in a
telephone briefing.
A MUTATING VIRUS
"As it becomes a human pandemic it must change. It must shift. That
may lead to a loss of virulence. However, we are dealing with a
worst-case scenario today and we have to learn how to best manage
it," Reddy added.
The findings add to a report published in October about a
14-year-old Vietnamese girl who survived an H5N1 infection after
being treated with Tamiflu, but who had a drug-resistant virus
strain in her body.
Four drugs treat influenza, but H5N1 already resists two older
drugs, amantadine and rimantadine.
Countries have been stockpiling the newer drugs, known as
neuraminidase inhibitors -- Roche and Gilead Science's Tamiflu,
known generically as oseltamivir, and GlaxoSmithKline and Biota's
Relenza, known generically as zanamivir.
De Jong and Moscona agreed that Relenza is a good alternative to
Tamiflu.
"Furthermore, Relenza is active against Tamiflu-resistant virus,"
De Jong said in an e-mail.
But Relenza currently must be inhaled and may not be useful in
patients with respiratory conditions such as asthma, and it might
not spread past the lungs to protect other organs.
There is not enough of either drug to treat more than a fraction of
patients should a bird flu pandemic erupt this year. Roche is
trying to license a generic process and step up its own production
to 600 million treatment courses by 2007.
There is an H5N1 vaccine but it is experimental and is unlikely to
work well against whatever pandemic strain may eventually
emerge.
De Jong said Tamiflu must be used early on in infection to do any
good against any type of influenza. As with AIDS, a cocktail
approach may be needed.
There are few options now. De Jong said one possibility to add to a
cocktail is an antiviral used against hepatitis called ribavirin.
BioCryst Pharmaceuticals, Inc. has a new neuraminidase inhibitor in
the works called peramivir, which "may be an option in the future",
De Jong said.
