Magazine article Drug Topics

On Bugs and Drugs

Magazine article Drug Topics

On Bugs and Drugs

Article excerpt

Flu agents take center stage at 1998 ICAAC conference

As this year's influenza season was about to get under way, there was some good news about the prophylaxis and treatment of both Types A and B influenza at the Interscience Conference on Antimicrobial Agents & Chemotherapy (ICAAC), held recently in San Diego. But there was also bad news-that neither the investigational pill GS4104 (Hoffmann-La Roche and Gilead Sciences) nor the nasal spray zanamivir (Relenza, Glaxo Wellcome) is likely to be available until the 1999 flu season.

The new agents attack neuraminidase, a protein on the surface of the flu virus. They are expected to have broad-spectrum activity against various influenza strains, since this enzyme is similar for all strains of influenza.

In a randomized, placebo-controlled, double-blind phase III study involving 629 patients, GS4104 lessened the severity of flu symptoms, such as fever and cough, by 40% and reduced the duration of flu symptoms by 30%. More important, the drug reduced the incidence of complications such as bronchitis and sinusitis by 50% in a group of healthy adults, according to Frederick Hayden, M.D., professor of internal medicine and pathology at the University of Virginia. In another study of its efficacy for prophylaxis, GS4104 prevented influenza in 76% of those exposed to flu during the course of the winter flu season. Another study showed it prevented influenza in 84% of those treated during a local epidemic.

Testing a once- or twice-daily dose of zanamivir in a randomized, double-blind, placebo-controlled study of 1,107 healthy U.S. college students during an outbreak of influenza Type

A also produced favorable results. The drug reduced the risk of any flurelated illness by 67% and of a feverish influenza illness by 84%, compared with placebo, Arnold Monto, M.D., of the University of Michigan's School of Public Health, reported at the meeting. Zanamivir is administered by a special spray device, first in one nostril, then in the other; it can be self-administered by adults.

An application for yet another nasal spray flu vaccine (FluMist, Aviron) has been submitted to the Food & Drug Administration, but licensure has been held up pending "lack of data on manufacturing, validation, and stability." These developments make it unlikely that FluMist will be available for even the 1999/2000 flu season, the company said.

In studies reported here by lead investigator Robert Belshe, M.D., FluMist provided 87% protection from all strains of culture-confirmed influenza among the 1,358 participants. And it provided 100% protection against the strains incorporated in the 1997-98 flu vaccines when administered to the upper airway. Belshe is director of infectious diseases and immunology at the Center for Vaccine Development at St. Louis University in Missouri.

Neither spray nor pill, however, is expected to replace the need for the current type of influenza vaccine for certain groups such as health-care workers, teachers, and others in contact with the public. Also advised by investigators to get their flu shots are those over 65 years of age as well as younger individuals who are immunosuppressed for any reason. Immunosuppression puts patients at high risk of morbidity or possible mortality from complications like pneumonia.

In the meantime, however, other agents for prophylaxis and treatment are currently available. …

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