The nation's largest AIDS organization on Tuesday asked federal regulators to withdraw approval for GlaxoSmithKline's drug Trizivir in light of a study showing it was inferior to other treatment combinations. The AIDS Healthcare Foundation said keeping the drug on the market may be dangerous because some doctors may be unaware of the new findings and continue to prescribe Trizivir alone.

Trizivir is a single pill combining three HIV drugs - AZT, 3TC and abacavir - into one twice-daily regimen.

The National Institutes of Health said in March it had halted part of a trial comparing Trizivir alone to other drug combinations because Trizivir by itself was less effective at suppressing HIV.

AHF said it was "apparent that Trizivir may be effective only if it is taken with other HIV/AIDS drugs." "Trizivir's lack of effectiveness renders it unsafe," the group wrote in a letter to the Food and Drug Administration.

GlaxoSmithKline spokesperson Nancy Pekarek said AHF was "acting irresponsibly" by seeking Trizivir's withdrawal. "What they are trying to do is deny patients and physicians an important weapon" against HIV, she said, adding that patients should not stop treatment prescribed by their doctors. Pekarek said the NIH study should be considered "in the context of total available data, which proves the effectiveness of Trizivir." She also said that a Department of Health and Human Services expert panel had issued guidelines in July recommending Trizivir as a first-choice option.

AHF said GlaxoSmithKline continues to aggressively market Trizivir as a stand-alone treatment despite the NIH trial. Trizivir is the fifth most-prescribed HIV medication, AHF said. An FDA spokesperson said the agency will review the request to pull Trizivir from the market. AHF provides HIV- related medical care to some 12,000 patients in the United States.

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