Important note: Information in this article was accurate in 1998. The state of the art may have changed since the publication date.
The Associated Press - Friday, December 18, 1998
Lauran Neergaard, AP Medical Writer
The Food and Drug Administration approved Ziagen, known chemically as abacavir, late Thursday.
Glaxo says Ziagen, part of a class of AIDS drugs known as nucleoside analogues, is valuable because its portion of the drug cocktail requires swallowing just one tablet twice a day without the dietary restrictions of some other drugs.
Scientists have been working to lower the large number of pills HIV patients must swallow each day. Missing even a few doses can encourage the AIDS virus to mutate into harder-to-treat strains.
But Ziagen comes with a big safety warning: About 5 percent of patients can suffer a hypersensitivity reaction to the drug that can be lifethreatening, said FDA's antiviral chief Dr. Heidi Jolson.
Symptoms include fever, fatigue, nausea-vomiting and rash, and usually occur within the first six weeks of therapy.
But they can be confused with side effects from other HIV drugs.
"Physicians and patients would have to be very, very suspicious that the symptoms are likely to be due to Ziagen and err on the side of caution" by immediately stopping the drug, Jolson stressed.
The FDA mandated that every patient receive a detailed notice explaining the reaction and what to do if they experience symptoms, plus a wallet-sized card to carry that describe symptoms in layman's terms.
"It's guilty 'til proven innocent," agreed Glaxo's Dr. Lynn Smiley. When symptoms occur, "stop the drug and call the doctor."
Anyone who suspects they have a reaction should not try to resume Ziagen later, because a second reaction will be much more severe, Jolson said. Scientists have probed eight deaths associated with the drug, although there is no way to prove causation, she said.
Glaxo's testing showed Ziagen was most effective when used by patients who hadn't yet tried other AIDS drugs. When HIV mutates against other nucleoside analogues, it can prove resistant to Ziagen, too.
In a study of Ziagen plus AZT and 3TC, 75 percent of never-treated adult HIV patients saw their HIV plummet to undetectable levels vs. 35 percent who took the older drugs alone. In a study of children who had taken multiple other AIDS drugs before trying Ziagen, 13 percent responded to Ziagen therapy vs. 2 percent taking older drugs.
Glaxo is studying whether Ziagen can be as effective as protease inhibitors, the landmark medicines that have helped thousands of HIV patients rebound from their disease. While Glaxo terms preliminary results promising, the FDA stressed Friday that there is too little data to determine if the drugs are comparable.
Ziagen will be on pharmacy shelves next month, both tablets for adults and a liquid for children, Glaxo said. The wholesale price for a year's supply will be $3,540, almost $500 cheaper than a recently approved once-a-day AIDS drug -- although that competing medicine was deemed comparable to protease inhibitor therapy.
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