The FDA advisory committee voted 13-1 to endorse the four-drugs-in-one treatment, but members said there should be effective monitoring for potential kidney problems among patients and urged further research to determine the drug's safety profile for women, who have been under-represented in clinical research.

The panel's recommendation will now be taken into account by agency regulators, who are expected to decide on final approval for Quad by August 27.

An overwhelming number of the experts said they were satisfied with Gilead's demonstration of safety and efficacy.

But Dr. Michelle Estrella of Johns Hopkins University School of Medicine, the panel's lone 'no' vote, said data on potential renal problems and women's health was too limited to justify her approval.

"There are plenty of alternatives to Quad," she said. "There's no huge hurry in approving this drug before the outstanding studies are completed."

Gilead shares closed 1.2 percent higher at $51.84 after the committee voted.

Wall Street analysts said the panel's action was expected and predicted more good news for Gilead on the FDA front.

"Approval of the Quad is likely with renal monitoring. Renal monitoring is not a particular concern," J.P. Morgan analysts said in a note to investment clients. "We believe the Quad will further strengthen Gilead's market leading HIV business."

In fact, the new drug is seen as key to Gilead's continued dominance of the market for HIV drugs. Most of the company's current drug sales, which totaled $8.1 billion last year, come from Atripla, a once-daily pill that combines Truvada with Bristol-Myers Squibb's Sustiva. Truvada consists of Gilead's older HIV drugs Emtriva and Viread.

On Thursday, the panel also recommended Gilead's Truvada pill as the first-ever drug for use in preventing HIV infections.

Nearly 1.2 Americans are infected with the human immunodeficiency virus that causes AIDS and the HIV epidemic grows by 50,000 new cases each year, according to the U.S. Centers for Disease Control and Prevention.

Company research shows Quad to be 88 percent effective at suppressing HIV infection, surpassing 84 percent efficacy for Atripla. But data also indicated a disproportionate number of kidney problems among the hundreds of patients who participated in clinical trials.

It combines the experimental integrase inhibitor elvitegravir with the boosting agent cobicistat and two older nucleotide reverse transcriptase inhibitors - emtricitabine and tenofovir.

If approved by the FDA, Gilead executives said Quad would provide HIV suffers with the first ever once-daily integrase inhibitor, a class of drug designed to block the spread of HIV by preventing the virus from binding with the DNA of host cells.

Advocates said the one-a-day regimen would encourage patients to adhere to the treatment with Quad, boosting the likelihood of high efficacy outside the clinical atmosphere.

But HIV activists who provided public testimony warned policymakers to be wary of new HIV drugs that provide only marginal improvements over current treatments but allow drug makers to charge significantly higher prices at a time when public assistance can be restricted by government budget constraints.

"Reduced access here in America is compelling AIDS activists to rethink the rules on drug pricing," said James Driscoll of the AIDS Healthcare Foundation, a Los Angeles-based nonprofit group that provides care for nearly 170,000 HIV and AIDS patients.

Gilead said it has yet to establish a price for Quad. Atripla currently costs about $20,000 a year.

(Reporting By David Morgan; Editing by Gerald E. McCormick, M.D. Golan, Gary Hill)

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