Gilead Sciences (GILD) cleared a hurdle Thursday as it seeks to market its top-selling HIV drug Truvada to help prevent infection of the virus. If approved for that use, Truvada would be the first drug sold to actually help reduce the risk of HIV.

A panel of Food and Drug Administration advisers were in favor of approval of the new use for individuals at the highest risk of becoming infected. The panel was overly supportive of approving the drug for men who have sex with other men and for partners in couples in which one person is infected with HIV. The panelists were split on whether other individuals should be prescribed the drug. The FDA, which will consider the advisers’ recommendations, is scheduled to make a decision on the new use of Truvada by June 15.

While investors expect hepatitis C treatments will be a big part of Gilead's future, the company can't take its eye off its biggest business. Gilead is the dominant player for HIV drug sales and it's important for the company to keep momentum as other companies test new treatments.

Gilead scored another victory Friday, when a separate FDA panel recommended a single pill that combines four medicines for HIV-infected patients. That drug, known as Quad, may be particularly important to Gilead's HIV program.

Truvada was approved by the FDA in 2004 to treat HIV infections. Sales of the drug rose 8% to about $2.9 billion last year.

Shares of the company rose more than 1% Friday to close at $51.84.

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