A second influenza drug, GlaxoSmithKline’s Relenza, should be stockpiled in readiness for a feared global pandemic of avian flu, researchers said Thursday.
The drug, known generically as zanamivir, is inhaled and some doctors have worried that patients may not be able to use it correctly, but the team of Asian doctors said it will be important to have as many antivirals on hand as possible.
The H5N1 bird flu virus has killed 62 people since late 2003 and is affecting flocks from Vietnam to Kazakhstan. Although it is not yet easily transmitted from birds to people or from person to person, experts fear it will acquire this ability and cause a worldwide disaster.
So health officials are scrambling to come up with a plan for dealing with it.
A dozen Asian nations agreed Thursday to build a regional stockpile of drugs, mostly oseltamivir, made by Swiss drugs giant Roche under the brand name Tamiflu.
Roche said last week it was considering donating a "substantial amount" of Tamiflu to the World Health Organization. Countries in North America and Europe are also stockpiling as much of the drug as they can, although production is limited.
Work is also underway to develop a vaccine to protect against H5N1.
More antiviral drugs needed
But this is not enough, argued Kenneth Tsang of the University of Hong Kong and colleagues.
“A vaccine for H5N1 will not be available in the foreseeable months,” they wrote in a commentary in the Lancet medical journal.
“Even if pharmaceutical manufacturing begins soon after an outbreak, there would not be a sufficient supply for the countries most in need — i.e., the Asian nations,” they added.
“Antiviral drugs are consequently the only specific treatment, pending availability of effective vaccines.”
There are four influenza drugs — amantadine and rimantadine, which do not help fight H5N1 infections, and Tamiflu and Relenza, which are both drugs in a class called neuraminidase inhibitors.
Both reduce the severity of a flu infection and can help patients recover more quickly, and both have also been shown to prevent infection in some cases.
“Although both have similar efficacy, zanamivir has fewer adverse reactions, and a favorable resistance profile,” Tsang and colleagues wrote.
Resistance a factor
All viruses eventually develop resistance to drugs, and influenza viruses are especially quick to do so.
“The resistance factor would be an important consideration in a pandemic situation,” the researchers wrote.
“The reasons for zanamivir not being chosen for stockpiling might include concern that young children and patients with intellectual or coordination impairments would not be able to inhale zanamivir properly, although there are novel ways of giving the drug to children.”
They said airway spasm can occur when zanamivir is inhaled but this is rare.
Tsang and colleagues also called for clinical trials combining Relenza and Tamiflu to see if the combination works better than either drug alone.
They also suggested local manufacture of both vaccines and the antivirals.
“Perhaps vaccine and neuraminidase inhibitor manufacturing activities should also begin in Asia,” they wrote.
“The ethics of maintaining drug patents in a potential worldwide catastrophe is questionable.”
The Australian maker of the drug, research group Biota Holdings Ltd., has sued GlaxoSmithKline for what it says is the international pharmaceutical company’s failure to promote Relenza properly.