Bird flu pandemic seen needing multiple drugs Posted on May 16th
sorts of flu drugs — not just Roche Holding AG’s Tamiflu — to
counter the danger of resistance in a pandemic triggered by
bird flu, British experts said on Wednesday.
The warning could boost demand for GlaxoSmithKline Plc’s
inhaled medicine Relenza, which has been largely overlooked in
favor of Roche’s more convenient pill.
Scientists analyzing the structure of a key flu virus
protein found that both H5N1 and seasonal flu could develop
resistance to Tamiflu, while still remaining highly susceptible
to Relenza.
“What this research shows is that stockpiling any one drug
to prepare for a potential H5N1 pandemic is unlikely to provide
adequate cover,” said Steve Gamblin of the National Institute
for Medical Research in London.
“In order not to be outflanked by the virus, it will be
necessary to have stocks of both existing drugs.”
There is a also “a huge imperative” to develop further
drugs since the best way to treat patients in the long term is
likely to be a three- or four-pronged approach, similar to the
multi-drug cocktails used to fight HIV and AIDS, Gamblin said.
A new influenza drug, peramivir, is being developed by
Biocryst Pharmaceuticals Inc but it must be injected and it has
not performed well in clinical trials. Two older flu drugs are
available but flu viruses have quickly developed resistance to
them, although some experts believe they may be useful in
cocktails with newer drugs.
Both flu viruses and HIV have a high rate of mutation,
which allows them to adapt to the treatments devised to tackle
them.
To date, H5N1 remains mainly a virus affecting birds,
although it has killed more than 200 people since 2003. But
scientists say it is the most likely source of the next deadly
flu pandemic in humans, since it may soon mutate into a form
transmitted easily from person to person.
Tamiflu, known generically as oseltamivir, and Relenza, or
zanamivir, target the viral protein neuraminidase, which helps
release newly made viruses so that they can spread infection.
Using a technique called X-ray crystallography, Gamblin and
colleagues examined the exact mutation in protein structure
that can make some flu virus resistant to Tamiflu and showed
the different nature of Relenza meant it was still effective.
Their results were published in the journal Nature.
The main seasonal flu virus circulating this year in the
United States and Canada as well as parts of Europe has shown
higher resistance to Tamiflu. But cases of resistance remain
relatively rare.
Tamiflu, which was originally developed by Gilead Sciences
Inc, had sales of 1.9 billion Swiss francs ($1.8 billion) in
2007, making it a major profit driver for the Swiss group.
Relenza, which Glaxo licensed from Australia’s Biota Holdings
Ltd, sold 262 million pounds ($510 million) last year.
(Editing by David Holmes)
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