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2022-8-8 6:33:16


Expert urges bird flu drug trials in HongKong
submited by kickingbird at Apr, 23, 2005 8:51 AM from The Standard

As scientists increasingly worry about an "imminent´´ bird flu pandemic which they say will kill millions around the globe, a local respiratory specialist says it is Hong Kong´s´ "scientific and moral responsibility´´ to conduct clinical trials on anti-viral drugs if avian flu breaks out in the SAR.

The suggestion comes from Dr Kenneth Tsang, a respiratory specialist at Hong Kong University. He spoke recently on an unpublished study about the possible use of clinical trials on avian flu patients in the light of discussion about the efficacy of the drug under consideration by health authorities here, Tamiflu.

The bird flu virus, H5N1, is continuing to claim human casualties at regular intervals, though it has apparently been waning in poultry.

The World Health Organization says bird flu is one of the world´s most pressing health problems. The H5N1 virus has killed 36 Vietnamese, 12 Thais and three Cambodians since 2003.

Hong Kong has 1.7 million Tamiflu tablets and plans to stockpile at least 20 million doses of the drug by next year for health-care workers who will be on the frontline should an outbreak occur.

The controller of the Centre for Health Protection, Dr Leung Pak-yin, said the center and Health Department would liaise with general practitioners on stockpiling sufficient doses for themselves, their staff and their immediate families.

The number of doses to be stockpiled is determined by using a 15 per cent ``attack rate´´ of the virus as well as calculations used by the United Kingdom and Australia, Leung said. Those countries stockpile pandemic drugs for about 20-30 per cent of the general population.

Questions lingered in the medical community about the possible ineffectiveness of Tamiflu after an August 28, 2004, article in the medical journal The Lancet, showed Japanese human type-A influenza had potential to develop drug-resistance.

However, that clinical trial only involved Tamiflu and did not test any other antivirals.

In Hong Kong, clinical drug trials on patients with H5N1 would help sort out what is known about drug effectiveness in Relenza and Tamiflu, said Tsang.

According to Tsang´s unpublished study, only patients with ``laboratory and clinical diagnosis of H5N1´´ who have given written consent and who have not undergone intubation or multiple organ failure would be slated for the studies.

The clinical trials would be used for developing ``the most efficacious treatment´´ for bird flu and stop doctors ``from giving potentially harmful treatments,´´ he said.

However, Dr Karen Hall, the WHO communicable diseases surveillance and response coordinator in China, said that the WHO Global Influenza Network has worked with research laboratories to make a prototype H5 virus strain.

``The prototype virus strain, which needs to undergo both animal and human trials before it could be used to produce a vaccine, has been made available free of charge to any country in the world which wishes to try and develop a pandemic vaccine using this prototype,´´ she said.

However, ``if an institute were to begin producing commercially a vaccine based on reverse genetic techniques, it is likely that the institute would have to comply with international patent laws and pay the patent holder,´´ she said.

And if bird flu did come to Hong Kong?

``Under World Trade Organization rules, patent rights can be set aside if the secretary-general of the United Nations declares a global emergency,´´ Hall said.

``So, if there were a pandemic, it is likely that patent rights would not apply.

``The WHO recommends that countries consider their individual needs to create a stockpile´´ of whatever antiviral drugs it considers to be most advantageous.

``The WHO does not recommend any particular drug - rather [it recommends] that countries consider their needs, make an assessment of which influenza strain(s) pose the greatest threat and take into account the latest findings on drug resistance.´´

She said that costs and ``individual country licensing practices and availability´´ are important considerations, as well.

The differences between the two drugs - Tamiflu and Relenza - are these: Tamiflu is in tablet form and easier to stockpile for longer periods of time.

Relenza is administered with an inhaler, ``hence,´´ wrote Hall. ``[It] is difficult to administer to children/elderly and causes broncospasms (acute breathing problems) in some patients.´´

According to the WHO Secretariat´s ``Influenza pandemic preparedness and response´´ paper issued January 20, two influenza epidemics, in 1957 and 1968, ``caused ... combined mortality estimated at more than three million deaths, mostly in the very young, the elderly and people with underlying chronic conditions.´´

Tsang offered evidence that Relenza ``can be taken in by low inhale flow rates,´´ meaning that only the very sick would have trouble inhaling the medicine. Relatively healthy individuals would presumably be able to take it in even without high lung power.

The center would offer GPs a health-care booklet and guidelines.

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