UPDATE 1-Gilead says Quad pill suppresses HIV at 48 weeks

LOS ANGELES, Sept 13 (Reuters) - Gilead Sciences Inc said 48 week-data from a mid-stage trial of its closely watched four-medicine HIV pill known as the 'Quad' show the drug works as well as the company's widely used Atripla three-drug treatment.

Gilead began in April a large pivotal-stage trial of the drug, which combines experimental integrase inhibitor elvitegravir and a 'boosting agent' called cobicistat with its older HIV drugs, Emtriva and Viread.

Most of the company's current HIV drug sales come from Atripla -- which is composed of Emtriva, known generically as emtricitabine, Viread, or tenofovir, and Bristol-Myers Squibb Co's Sustiva, also known as efavirenz.

After 48 weeks of treatment in the Quad-Atripla study, 90 percent of patients taking the Quad achieved target reductions in levels of the HIV virus in the blood, known as viral load, compared with 83 percent of those who received Atripla -- matching results from earlier 24-week data from the trial.

Gilead said safety, tolerability and discontinuation rates were similar between both arms of the study, but fewer central nervous system problems, including abnormal dreams or nightmares, dizziness and anxiety occurred in patients receiving the Quad compared to those treated with Atripla.

The results were presented on Monday at the Interscience Conference on Antimicrobial Agents and Chemotherapy in Boston.

(Reporting by Deena Beasley; editing by Andre Grenon) Keywords: GILEAD HIV/ ([e-mail] [phone]) COPYRIGHT Copyright Thomson Reuters 2010. All rights reserved. The copying, republication or redistribution of Reuters News Content, including by framing or similar means, is expressly prohibited without the prior written consent of Thomson Reuters.