a SLACK Incorporated newspaper
March 1999
GAITHERSBURG, Md. - An advisory panel to the Food and Drug Administration (FDA) recently recommended against approval of the influenza drug zanamivir (Relenza, Glaxo Wellcome).
Members of the Antiviral Drugs Advisory Committee said the drug's safety was not the issue, but rather that the drug was not effective enough. The vote was 13 to four against FDA approval.
Although the FDA is not bound to follow the committee's recommendation, it usually does. If the FDA does approve the product, zanamivir would be the first new influenza drug approved in 10 years.
Panel members said the company had not answered many questions, including whether the drug worked in high-risk populations such as the elderly, and if it actually halted viral shedding. In addition, the panelists asked for further studies in children and those with weakened immune systems or chronic respiratory disease, and to determine optimal time for dosing.
The FDA said the results from U.S. studies did not prove efficacy. The largest U.S. study of zanamivir showed that those with influenza who took the drug felt better in five days, compared to six days for those who took the placebo.
The randomized, placebo-controlled study involved 1,117 healthy college students, 86% of whom had not been vaccinated against influenza during an outbreak of influenza A. Zanamivir reduced the risk of influenza illness by 67% and reduced the risk of influenza with fever by 84%, compared with placebo.
A study conducted in Europe and Australia showed the drug brought relief 1.5 to 2.5 days earlier than the placebo. The randomized, placebo-controlled study included 321 patients with confirmed influenza A or B. Results indicated that when zanamivir was inhaled through the mouth within 36 hours of symptom onset, fever, cough, muscle aches and fatigue were alleviated faster than with placebo (4.5 days with zanamivir vs. six days for placebo).
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Zanamivir is the first drug in a new class, with a novel mechanism of action and a unique delivery mode. The drug inhibits neuraminidase, an enzyme crucial to replication of influenza A and B, according to Glaxo. To take zanamivir, patients would insert a disc-shaped blister pack into an inhaler. The device's lid is used to puncture the blister and then the drug, released in a dry powder form, is inhaled.
Glaxo officials said the company would include detailed instructions in prescriptions, and would provide to pharmacists and physicians placebo-loaded devices to help train patients.
Zanamivir is delivered directly to the respiratory tract, where it can best stop viral replication, the company said. However, the FDA said it is not clear that the device would be easy to use, especially when patients are sick and weak. Panelists agreed there were some drawbacks to learning how to use the inhaler.
The labeling before the FDA is two puffs twice daily for five days.
In February the Australian Drug Evaluation Committee recommended zanamivir for approval, and Glaxo is also seeking approval in Europe. The drug was developed by the Australian company Biota Holdings.
Hoffman LaRoche is also developing a neuraminidase inhibitor for lessening duration of influenza. The drug, GS4104, discovered by Gilead Sciences, is in clinical trials.
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