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) --The success of a small, mid-stage study of

Gilead Sciences'

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experimental all-in-one "Quad" treatment for HIV was confirmed Wednesday at a closely watched meeting of HIV researchers.

After 24 weeks, 90% of HIV patients treated with the Gilead's Quad pill achieved a significant decline in the level of virus in their bloodstream compared to 83% of patients treated with Gilead's currently marketed HIV pill Atripla, Gilead said.

Detailed results from the phase II study are being presented Wednesday at 2:45 pm EST at the 17th Conference on Retroviruses and Opportunistic Infections (CROI). Gilead had previously disclosed on Jan. 6 that the

Quad study was a success

, but details were withheld so they could be presented formally at the CROI meeting, which is considered the most important annual gathering of HIV drug researchers.

Gilead shares were up 3% to $48.33 in recent trading.

The Quad pill is the most important drug in Gilead's pipeline and a key component of the company's plans to grow and extend its dominance in the HIV treatment market.

The Quad consists of four drugs combined into a single, once-daily treatment for HIV. Two of the Quad's components are unapproved, experimental drugs -- elvitegravir and GS9350. They are combined with Truvada, itself a two-drug combination currently marketed by Gilead and a mainstay of HIV treatment.

The Quad is expected to be much more profitable for Gilead because the company will own all four of the drugs that make up the pill. Gilead's current HIV treatment Atripla is made up of three drugs, one of which, Sustiva, is owned by

Bristol-Myers Squibb

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The Quad pill outperformed Atripla even with the former being dosed in patients with lower levels of immune-boosting CD4 cells at the study's start. From a statistical perspective, the Quad and Atripla were non-inferior to each other, which is what Gilead hoped to demonstrate with the study from the outset.

Discontinuation rates due to adverse events were similar in both arms of the study.

Over the past week, the Wall Street worry mill has churned with talk that GS9350 -- the "boosting" agent in the Quad that increases the blood level of the other HIV medicines -- might decrease kidney function. The issue is potential important because Viread, one of the other drugs in both the Quad and Atripla, does cause kidney problems in a small number of patients.

Gilead tried to refute any safety concerns Wednesday. In two phase II studies involving GS9350, also known as cobicistat, small increases in serum creatinine (a surrogate value used to measure kidney function) were observed in patients, but in a separate study of healthy volunteers dosed with cobicistat, kidney function was not adversely affected, Gilead said.

In an email to clients Wednesday, Deutsche Bank biotech analyst Mark Schoenebaum said Gilead confirmed to him that additional testing of GS9350/cobicistat was done, which "definitely established there was no kidney damage at all."

Investors are paying close attention to the Quad's clinical progress because of concerns that Gilead's growth will be pinched in the coming years when generic versions of Truvada become commercially available.

-- Reported by Adam Feuerstein in Boston.

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Adam Feuerstein writes regularly for In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback;

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