Cobicistat is Gilead’s proprietary potent mechanism-based inhibitor of cytochrome P450 3A (CYP3A), an enzyme that metabolizes drugs in the body. In addition to studying the agent as part of the Quad, Gilead is also examining cobicistat’s potential in boosting commercially available HIV protease inhibitors.The Quad, elvitegravir and cobicistat are investigational products and their safety and efficacy have not yet been established. About Gilead Sciences Gilead Sciences is a biopharmaceutical company that discovers, develops and commercializes innovative therapeutics in areas of unmet medical need. The company’s mission is to advance the care of patients suffering from life-threatening diseases worldwide. Headquartered in Foster City, California, Gilead has operations in North America, Europe and Asia Pacific. Forward-Looking Statement This press release includes forward-looking statements, within the meaning of the Private Securities Litigation Reform Act of 1995, that are subject to risks, uncertainties and other factors, including the risk that the FDA, the European Medicines Agency and other regulatory agencies may not approve the Quad and risks related to the anticipated timelines for any regulatory review and approval. In addition, any marketing approval, if granted, may have significant limitations on its use. Further, even if approved, physicians may not see advantages of the Quad over other therapies and may therefore be reluctant to prescribe the product. These risks, uncertainties and other factors could cause actual results to differ materially from those referred to in the forward-looking statements. The reader is cautioned not to rely on these forward-looking statements. These and other risks are described in detail in Gilead’s Annual Report on Form 10-K for the year ended December 31, 2011, as filed with the U.S. Securities and Exchange Commission. All forward-looking statements are based on information currently available to Gilead, and Gilead assumes no obligation to update any such forward-looking statements.