SAN FRANCISCO (San Francisco Chronicle) - A U.S. Food and Drug Administration advisory panel will vote on whether to recommend approval of an experimental AIDS drug designed to treat patients who've become resistant to other medicines.

If, as expected, the vote is favorable, the committee must also recommend whether the new drug should be approved only as a treatment of last resort or sanctioned for use as an early stage medicine as well.

The FDA usually follows the advice of its advisory committees, making Wednesday's vote a key hurdle for Gilead Sciences, a Foster City, Calif., biotech firm that hopes to get its AIDS drug, Viread, on the market in November.

Trading in Gilead shares was halted Tuesday after the FDA posted a staff report so favorable that it suggested the real question before the panel is whether Viread should be approved as a last resort treatment for drug-resistant patients, or as a first-line AIDS medicine for new HIV cases.

"We're asking that it be labeled for all HIV infections," said Carol Brosgart, Gilead's vice president for clinical affairs.

That position is supported by AIDS activist Martin Delaney of San Francisco's Project Inform.

"I'll be damned if we sit there and let them produce a narrow-label indication," he said. "This may well be the least toxic AIDS drug yet studied."

The 12-member FDA panel must draw conclusions from the clinical-trial data Gilead will present Wednesday. In its largest study to date, Gilead tested Viread on HIV-positive patients who had been taking other AIDS drugs for at least five years.

A majority of these patients were beginning to develop resistance to the medications. Their viral load - the concentration of HIV in their blood stream - was increasing and their CD-4 cell counts were declining, signs of immune systems susceptible to other infections.

The FDA staff report leaves little doubt that Viread reduced viral load by about 75 percent. Gilead's testing "provides clear evidence of (Viread's) antiviral activity," the report said.

That suggests Viread could easily win FDA approval for use on patients resistant to other HIV drugs.

But because the company wants permission to promote the medicine as a first-line treatment for new AIDS patients, the FDA said it is "convening this meeting to solicit the committee's comments."

The FDA is expected to make a final decision on Viread by Nov. 1.

If the FDA says Viread should only be used as a last resort, Gilead is prepared to submit new studies to support its case for early use.

Gilead has already identified 601 patients who have been newly diagnosed with HIV and are receiving AIDS drugs for the first time. Half of these volunteers are getting a cocktail of drugs that includes Viread. The other half are receiving standard AIDS drugs.

Brosgart said the company will see data from this study in the first half of 2002, and is confident it will show Viread is safe and effective in fighting new HIV infections.

Analyst Tom Dietz at Pacific Growth Equities in San Francisco issued a "strong buy" recommendation for Gilead on Tuesday, and Geoffrey Harris from UBS Warburg in New York set a target price of $70 a share. Gilead will open at $56.62 when trading resumes after the advisory panel's meeting.

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