San Francisco, 28 September, 1999: The targeted delivery of Relenza results in high concentrations of the drug in the primary site of viral replication, the lungs, up to 24 hours after inhalation. It is also effective against A& B strain influenza, and reduces complications requiring antibiotics. These are the conclusions from three studies of Relenza (zanamivir), the new anti-flu treatment, being presented to physicians at a major anti-viral conference.
The data presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), September 26-29, in San Francisco, USA, provide further evidence of the effectiveness of Relenza, and its highly targeted mode of administration, against both A & B strains of influenza.
Results from a laboratory study, presented at ICAAC1, showed that the inhalation of Relenza resulted in a high concentration of the drug in the lungs. These levels of the drug allow for continued anti-viral activity at the major site of viral replication and were retained up to 24 hours after a single 10mg inhaled dose. These data strongly support the use of an inhaled therapy that delivers its effect direct to the site of major viral replication.
A further benefit of the high concentrations achieved in the respiratory tract is that the possibility of development of resistance to the drug is reduced. Other influenza anti-virals have been of limited clinical use because the virus can often develop resistance to them rapidly.
The efficacy of the drug against influenza B was demonstrated by a meta-analysis of 220 patients, with confirmed B strain flu, from a total of 1,572 patients involved in five placebo-controlled studies. Using a regimen of 10mg twice daily (bid) for five days2, time to alleviation of symptoms (the primary endpoint) was reduced by 25 per cent to 4.5 days for those taking Relenza, down from 6.0 days for those on placebo.
The results of this analysis confirm the efficacy of Relenza in the treatment of influenza B which is similar to that already observed against influenza A. Amantadine is only active against influenza A.
In another reported study, the effect of Relenza treatment on the incidence of complications and antibiotic prescriptions was determined3. Analysis of three phase III studies revealed that among 609 patients receiving 10mg of active drug (bid), there was a 28 per cent drop in the incidence of complications requiring the use of antibiotics.
Relenza is the first in a new generation of specific treatments against the influenza virus, called neuraminidase inhibitors, which work by interfering with the life cycle of the influenza virus, in both influenza A and B types. It blocks the neuraminidase enzyme on the surface of the virus, thus preventing its release from the cell, which means that spread to neighbouring cells within the respiratory tract is inhibited.
Approved in the US in July, Relenza has also received approval in Australia, where it is currently being used for the first time in the clinical setting. In addition, it has recently been approved in the EU, under the mutual recognition process, and is under regulatory review in many other countries. Further product licences are expected over the coming year.
Relenza has been developed by Glaxo Wellcome under licence from the Australian company, Biota Holdings, giving Glaxo Wellcome the rights to develop and market it world-wide. Glaxo Wellcome is a research-based company whose people are committed to fighting disease by bringing innovative medicines and services to patients throughout the world and the healthcare providers that serve them.
Relenza is a trademark of the Glaxo Wellcome group of companies.
References
1. Peng AW et al. Sustained concentration in respiratory tract after 10 mg
zanamivir inhalation. Abstract No 1921 39th Annual Meeting of the Interscience
Conference on Antimicrobial Agents and Chemotherapy (ICAAC, September 26-29),
San Francisco, CA, USA.
2. Osterhaus ADME et al. The efficacy of inhaled zanamivir in the treatment of
influenza B. Abstract No 0281 39th Annual Meeting of the Interscience
Conference on Antimicrobial Agents and Chemotherapy (ICAAC, September 26-29),
San Francisco, CA, USA.
3. Kaiser, Hayden, Hammond, Keene. Efficacy of inhaled zanamivir in reducing
complications and antibiotic use in influenza -- results of Phase II and III
clinical studies. Abstract No 1903 39th Annual Meeting of the Interscience
Conference on Antimicrobial Agents and Chemotherapy (ICAAC, September 26-29),
San Francisco, CA, USA.