International symposium reports on the use of antivirals in patients with H5N1



    MISSISSAUGA, ON, March 4 /CNW/ - Physicians from countries affected by
the deadly H5N1 influenza virus (bird or avian flu) have presented case
reports about antiviral use in patients infected with H5N1, including
treatment with the oral antiviral TAMIFLU(R) (oseltamivir). The physicians'
reports were revealed this week at the International Symposium on Respiratory
Viral Infections (ISRVI) in Singapore.(1)
    TAMIFLU is approved for both the treatment and post-exposure prevention
(prophylaxis) of influenza in adults and in children one year and older.
Studies supporting the approval of TAMIFLU are based in seasonal influenza.
The magnitude of effect of TAMIFLU in treating and preventing novel strains of
influenza (such as those that may be involved in a pandemic or associated with
avian flu) cannot be predicted as it has not been studied or approved in a
pandemic scenario. The World Health Organization (WHO) has recommended that
higher doses and longer treatment durations may be required to combat novel
strains of influenza.
    According to the WHO, the H5N1 virus has already killed 234 people in 12
countries.(2) In the most recent clinical management guidelines issued by the
WHO, TAMIFLU remains the primary antiviral agent of choice for the treatment
of H5N1 virus infections.(3)

    Symposium findings

    In Indonesia, of the total of 119 H5N1 human cases reported, 22 survived
- an 18 per cent survival rate overall. Of the 119, 33 patients received no
TAMIFLU, all of whom died. TAMIFLU was administered to the other 86 patients,
with a 26 per cent survival rate overall. Time from onset of illness to
initiation of treatment appeared to influence survival. Of the two patients
who received TAMIFLU within 24 hours of illness onset, both survived. If given
the drug within four days, 55 per cent survived (6/11), and 35 per cent
survived if given TAMIFLU within six days (13/37).(4) The survival rate of
those receiving it later than six days after illness onset was 18 per cent
(9/49).(2)
    Recent information about eight Vietnamese patients infected with H5N1 was
also presented. All eight patients received TAMIFLU, however, all eight
patients presented to the hospital later than five days after onset of
illness. Only three of the eight patients survived reinforcing that treatment
benefit is reduced for patients that receive the drug later in the course of
illness.(4),(5) In two patients who were unable to take the drug orally due to
the severity of their illness, physicians administered the drug by nasogastric
tube and found it was well absorbed and there was a reduction in H5N1 virus in
these patients.

    Susceptibility of circulating H5N1 strains to TAMIFLU

    These clinical findings are supported by animal data, also presented at
ISRVI, which shows that oseltamivir treatment was effective against H5N1
influenza viruses representing different clades/subclades. However, higher
doses were required for the more pathogenic H5N1 viruses.(6)
    "Multiple factors can affect the susceptibility of antiviral therapy with
highly pathogenic H5N1 influenza viruses and it is reassuring that
oseltamivir, in mouse models, demonstrates activity even to the most
pathogenic circulating strains," comments study author Dr. Elena Govorkova,
St. Jude Children's Research Hospital, Memphis, US. "Antiviral drugs are an
essential component for the early control of an influenza pandemic."
    Data also confirms the low level of resistance reported to-date with
TAMIFLU to H5N1 avian influenza in the field; there are only five cases of
published reports of H5N1 resistance or reduced susceptibility to TAMIFLU to
date.(7),(8),(9) Laboratory results have shown 96 per cent of H5N1 strains (53
out of 55) tested in the laboratory were sensitive to TAMIFLU.(10)
    This compares to the around 14 per cent of isolates tested this year of
the seasonal influenza A H1N1 virus showing resistance to TAMIFLU, reported at
the conference.(11) It is important to note that these increased levels of
resistance have only been reported spontaneously in this year's H1N1 (Solomon
Islands) seasonal strain, and not an avian strain such as H5N1, and not in
patients who have been administered TAMIFLU.(12)
    "Currently, we are seeing that TAMIFLU has been used as part of the
clinical management of patients infected with H5N1 with only isolated cases of
resistance being reported," comments Dr. David Reddy, Global Pandemic Task
Force Leader at Roche. "This is reassuring for governments that have
stockpiled TAMIFLU for pandemic use. It is, however, critical that both Roche
and the medical community remain vigilant so that we can understand this
mutating virus and be best prepared for defence against a potential pandemic
strain."
    Roche has undertaken several research initiatives to study the use of
TAMIFLU against the evolving H5N1 avian influenza virus, including
collaborations with the National Institutes of Health (NIH), the Southeast
Asia Influenza Clinical Trials Research Network, and other research
institutions.

    Note to editors:

    Difference between a pandemic strain of influenza and seasonal influenza

    A pandemic strain of influenza is always of the A variety and is a
completely new strain to which there will be no immunity. A seasonal strain of
influenza is one that has previously been circulating, which may have changed
slightly (antigenic drift) and to which a level of immunity exists.

    About pandemic influenza

    An influenza pandemic occurs when a new strain of influenza A virus
appears, against which the human population has no immunity resulting in
several, simultaneous epidemics worldwide with enormous numbers of deaths and
illness. The most severe influenza pandemics to date include: 'Spanish flu' A
(H1N1): 1918 caused in excess of 30 million deaths worldwide; 'Asian flu' A
(H2N2): 1958 caused one million deaths worldwide; 'Hong Kong flu' A (H3N2):
1968 caused 800,000 deaths worldwide in six weeks. The WHO believes that we
are as close to the next pandemic as we have been at any time in the past 37
years, with two of the three widely-recognized prerequisites for a human
pandemic met to date in the avian influenza outbreak in East Asia. Firstly, a
new influenza virus strain has emerged (H5N1), and secondly, the virus has
spread to humans. The final barrier will be the effective transmission of the
virus from human to human.

    About TAMIFLU

    TAMIFLU is designed to be active against all clinically relevant
influenza viruses and works by blocking the action of the neuraminidase (NA)
enzyme on the surface of the virus. When neuraminidase is inhibited, the
spread of the virus to other cells in the body is inhibited. It is licensed
for the treatment and prophylaxis of influenza in children aged one year and
above and in adults. The most frequently reported adverse events in clinical
studies were nausea, vomiting, and diarrhea. TAMIFLU is available for the
treatment of influenza in more than 80 countries worldwide.
    TAMIFLU was approved based on studies in seasonal influenza. The
magnitude of effect of TAMIFLU in treating and preventing novel strains of
influenza (such as those that may be involved in a pandemic or associated with
avian flu) cannot be predicted. The WHO has recommended that higher doses and
longer duration may be required.

    Roche and Gilead

    TAMIFLU was invented by Gilead Sciences and licensed to Roche in 1996.
Roche and Gilead partnered on clinical development, with Roche leading efforts
to produce, register and bring the product to the markets. Under the terms of
the companies' agreement, amended in November 2005, Gilead participates with
Roche in the consideration of sub-licenses for the pandemic supply of TAMIFLU
in resource-limited countries. To ensure broader access to TAMIFLU for all
patients in need, Gilead has agreed to waive its right to full royalty
payments for product sold under these sub-licenses.

    About Roche

    Headquartered in Basel, Switzerland, Roche is one of the world's leading
research-focused healthcare groups in the fields of pharmaceuticals and
diagnostics. As the world's biggest biotech company and an innovator of
products and services for the early detection, prevention, diagnosis and
treatment of diseases, the Group contributes on a broad range of fronts to
improving people's health and quality of life. Roche is the world leader in
in-vitro diagnostics and drugs for cancer and transplantation, a market leader
in virology and active in other major therapeutic areas such as autoimmune
diseases, inflammation, metabolism and central nervous system.

    
    Additional information

    -   Roche Health Kiosk, Influenza: www.health-kiosk.ch/start_grip.htm
    -   About TAMIFLU: www.roche.com/med_mbTAMIFLU05e.pdf
    -   About influenza: www.roche.com/med_mbinfluenza05e.pdf
    -   WHO: Global influenza programme:
        www.who.int/csr/disease/influenza/en/
    -   WHO: Avian flu:
        www.who.int/mediacentre/factsheets/avian_influenza/en/

    References

    (1)  Antivirals and therapeutics session, X International symposium on
         Respiratory Viral infections, Singapore, Sunday 2nd March 2008
    (2)  World Health Organization. Cumulative Number of Confirmed Human
         Cases of Avian Influenza A/(H5N1) Reported to WHO. 28 February 2008
   
http://www.who.int/csr/disease/avian_influenza/country/cases_table_2008_02_28/
en/index.html
    (3)
   
http://www.who.int/csr/disease/avian_influenza/guidelines/ClinicalManagement07
.pdf
    (4)  Sedyaningsih ER. The Indonesian Experience, X International
         symposium on Respiratory Viral infections, Singapore, Sunday 2nd
         March 2008
    (5)  Wertheim HFI. The recent Vietnamese Experience, X International
         symposium on Respiratory Viral infections, Singapore, Sunday 2nd
         March 2008
    (6)  Govorkova E. Influenza Antivirals in H5N1 Disease, Animal Model, X
         International symposium on Respiratory Viral infections,
         Singapore, Sunday 2nd March 2008
    (7)  Writing Committee of the Second World Health Organization
         Consultation on Clinical Aspects of Human Infection with Avian
         Influenza A (H5N1) Virus. Update on Avian Influenza A (H5N1) Virus
         Infection in Humans. N Engl J Med 358;3
    (8)  de Jong MD, Thanh TT, Khanh TH, et al. Oseltamivir resistance
         during treatment of influenza A (H5N1) infection. N Engl J Med
         2005;353:2667-72
    (9)  Saad MD, Boynton BR, Earhart KC, et al. Detection of oseltamivir
         resistance mutation N294S in humans with influenza A H5N1. In:
         Program and abstracts of the Options for the Control of Influenza
         Conference, Toronto, June 17-23, 2007:228. abstract.
    (10) Hurt AC. et al. Susceptibility of highly pathogenic (H5N1) avian
         influenza viruses to the neuraminidase inhibitors and adamantanes.
         Antiviral Research 73 (2007) 228-231
    (11) World Health Organization. Influenza A (H1N1) virus resistance to
         oseltamivir - Last quarter 2007 to 28 February 2008. 28 February
         2008.
    http://www.who.int/csr/disease/influenza/H1N1ResistanceWeb20080228.pdf
    (12) World Health Organization. WHO/ECDC frequently asked questions for
         Oseltamivir Resistance. Last updated 15 February 2008.
    





For further information:

For further information: Rebecca Beitchman, Environics Communications
Inc., Phone: (416) 969-2744, E-mail: rbeitchman@environicspr.com

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