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Photo by: PAUL SAKUMA

In a May 2006 file photo, Gilead Sciences Inc. Chief Executive John Martin holds a Truvada pill bottle in a lab in Foster City, Calif. Scientists have an exciting breakthrough in the fight against AIDS. Daily doses of Truvada, a pill already used to treat infection with HIV, the virus that causes the disease, helped prevent healthy gay men from catching it through sex with an infected partner. (AP Photo/Paul Sakuma, File)

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