A US Food and Drug Administration (FDA) advisory panel will decide this week whether to recommend for the first time that certain healthy but at-risk people take a drug to help prevent them from contracting the virus that causes AIDS.

Approval by the agency would mark another milestone in the three-decade effort to combat HIV and AIDS. Huge advances in drugs to treat infection and its symptoms have allowed patients to live significantly longer and healthier lives for a disease that in the 1980s was a death sentence.

On Thursday, an FDA panel will weigh whether Gilead Sciences, which makes the HIV treatment drug Truvada, should be allowed to market the drug to help prevent high-risk patients from contracting HIV in the first place. It is the first time a company asked the FDA for approval of an HIV drug as a prevention tool.

The FDA does not comment on pending drug applications, and there is too much disagreement over the drug studies to predict whether the agency will sign off on the new use. The FDA does not have to follow the recommendations of its expert panels, but usually does.

Some research has shown that taking the drug can materially lower a person's risk of HIV infection, and most doctors support using it this way in limited circumstances. Truvada -- a combination of two medicines that makes it harder for HIV to multiply in the body -- is one of the most widely-used HIV drugs. It costs about $14,000 a year.

But medical experts and AIDS activists are divided over whether the agency should approve Gilead's application.

Some doctors argue the clinical data are not strong enough and that approval could undermine other HIV prevention efforts like condom use. Others fear an FDA rejection might stall additional research into new HIV-prevention efforts.

The AIDS Healthcare Foundation is leading efforts against FDA approval of Truvada. The organization filed a petition with FDA in March urging the agency to reject the application, saying the data were not strong enough to show the drug prevents HIV in healthy people.

The group also cited concerns about drug side effects, the estimated annual cost of the drug and the difficulty of sticking with a daily pill regimen.

But another organization, called AVAC, a group that advocates for HIV prevention methods, is leading efforts in support of Truvada and was among 14 organizations that last week submitted a letter to the FDA urging approval.

In the US, about 1.2 million people are infected with HIV, and about 50,000 new infections are diagnosed each year.

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