Gilead Sciences (GILD)' pill Truvada was safe and effective when used to protect uninfected people from getting HIV, U.S. regulators said in a report indicating the main concerns are when and how it should be used.

Truvada was "well tolerated" and its ability to reduce the risk of infection was backed by two studies, the Food and Drug Administration staff said in a report Tuesday. Gilead, based in Foster City, is seeking to sell the drug as the first pill to keep people from becoming infected.

The FDA asked its advisers to suggest who should get Truvada; what testing would be needed for administration; and what educational material should be used for patients and doctors. The advisers will meet Thursday to discuss the drug, the subject of debates over its appropriate use and cost.

Decisions to prescribe Truvada "should carefully weigh the individual risks for acquiring HIV, their understanding of the importance of adherence to medication, and their potential for development of renal toxicity," the FDA staff said Tuesday in a report on the agency's website. Education and counseling will be "critically important."

Gilead fell less than 1 percent to $49.46 at the close of New York trading. The FDA isn't required to follow what the advisory panel suggests.

Investors aren't counting on expanded use of Truvada to boost sales much, said Robyn Karnauskas, an analyst with Deutsche Bank in New York. Instead, they are focused on Gilead getting new products to market before facing the loss of half of its revenue from patent expirations beginning in 2018.

"Right now, the company is in a position where they have flat sales and Truvada isn't going to fix the patent cliff problem," Karnauskas said.

Debate over the appropriate use of the drug has divided the AIDS community. Some AIDS advocacy groups say the drug will be a valuable tool for reducing new cases, particularly within stable partnerships where one person has AIDS and the other doesn't. Others said it may lead to more infections, lower condom use and might build resistance to the medicine.

The population at high risk for contracting the disease includes at least 140,000 individuals whose spouses or partners have the disease, as well as 275,000 gay men who had more than two partners in the past year and didn't wear condoms during sex, according to the U.S. Centers for Disease Control and Prevention, based in Atlanta.

"Thirty years into the epidemic we can't dismiss any new options," James Loduca, a spokesman for the San Francisco AIDS Foundation, said in an interview. "This won't end AIDS by itself, but we can't end it without this."

Loduca said condoms aren't enough to stem the tide of new infections, and using Truvada as a preventative measure would help if taken correctly.

While the number of people infected with HIV rose to 34 million worldwide in 2009, the virus that leads to AIDS, once a death sentence, can be reduced to low levels in the blood with use of combination antiviral medicines such as Truvada.

Michael Weinstein, president of the AIDS Healthcare Foundation, said approval and prescription of Truvada as a preventative may lead to less condom use and more infections, as well as increased resistance to the drug.

"Why would you take this medication if you intended to use condoms?" he said. "You've got to be really paranoid about your pants falling down to wear a belt and suspenders."

His organization sued the FDA last year after the agency rejected its Freedom of Information act request for correspondence between regulators and Gilead. Weinstein said the studies don't prove that the pill is effective enough to warrant approval. The AIDS Healthcare Foundation has lined up speakers for the public hearing later this week to oppose its preventative use, Weinstein said.

Barry Zingman, medical director at the AIDS Center at Montefiore hospital in the Bronx, one of the largest treatment centers in New York, said he hopes the drug is approved and plans to offer it to some patients.

"If condoms were 100 percent effective and useful we wouldn't have HIV at all," Zingman said in an interview. "The reality is many people don't like to use condoms or won't, and taking a pill can be a lot more acceptable to them."

He said his big concern is the drug's more than $11,000 a year price tag.

"People are really interested in the concept, but there have been issues related to insurance coverage," Zingman said. "Approval would make a significant advance in insurance coverage."

Aetna spokeswoman Tammy Arnold and WellPoint's Lori McLaughlin said their companies would consider covering the treatment as a form of prophylaxis if approved by the FDA.

Medicare, the federal program for the elderly and disabled, and Medicaid, the joint state-federal plan for the poor, typically reimburse for all FDA-approved indications.

If approved, the drug would mostly be given to people at high risk for infection, like men who have sex with men, intravenous drug users and sex workers, said Ken Mayer, medical research director at the Fenway Institute, the largest AIDS treatment center in New England.