Treatment discontinuations due to adverse events were reported in three percent of patients receiving 24 weeks of therapy and four percent of patients receiving 12 weeks of therapy. The most common side effects observed in the study were consistent with the safety profile of RBV and included fatigue, nausea, headache and insomnia.About PHOTON-1 PHOTON-1 is an ongoing open-label Phase 3 study being conducted at sites in the United States and Puerto Rico to evaluate the efficacy and safety of 12 or 24 weeks of sofosbuvir 400 mg once-daily plus weight-based RBV (1,000 or 1,200 mg/day) among HCV treatment-naïve patients with genotype 1, 2 or 3 HCV infection who are also HIV-positive. Ninety-five percent of PHOTON-1 patients were receiving antiretroviral therapy for their HIV infection. The HIV treatment regimens permitted in the study were based on the results of a separate Phase 2 drug-drug interaction study conducted by Gilead demonstrating that sofosbuvir did not significantly affect the pharmacokinetic parameters of drugs from various classes of antiretrovirals. The most common HIV treatment regimens taken by patients in PHOTON-1 were Gilead’s Truvada ® (emtricitabine/tenofovir disoproxil fumarate) administered with efavirenz, atazanavir/ritonavir, darunavir/ritonavir or raltegravir. Additional information about PHOTON-1 can be found at www.clinicaltrials.gov. Sofosbuvir is an investigational product and its safety and efficacy have not 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 and South 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 possibility of unfavorable longer-term resulting from clinical trials evaluating sofosbuvir, including in combination with other products and among patients with HCV/HIV co-infection or HCV monoinfection. In addition, regulatory authorities may not approve sofosbuvir for HCV-related indications and any marketing approval may have substantial limitations on its use. As a result, sofosbuvir may never be successfully commercialized. Further, Gilead may make a strategic decision to discontinue development of sofosbuvir if, for example, Gilead believes commercialization will be difficult relative to other opportunities in its pipeline. 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 Quarterly Report on Form 10-Q for the quarter ended September 30, 2013, 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.