Gilead Announces Data for Genotype 1 Null Responder Hepatitis C Patients Enrolled in ELECTRON Study

– Viral Relapse Seen Post Treatment with GS-7977 Plus Ribavirin –

– Awaiting Data for Treatment-Naïve Genotype 1 Patients –

FOSTER CITY, Calif.--(BUSINESS WIRE)--Feb. 17, 2012-- Gilead Sciences, Inc. (NASDAQ:GILD) announced today that the majority of hepatitis C genotype 1 patients with a prior “null” response to an interferon (IFN)-containing regimen enrolled in the ongoing ELECTRON study experienced viral relapse within four weeks of completing 12 weeks of treatment with GS-7977 plus ribavirin (RBV). Ten patients were randomized to this arm of the ELECTRON study and data are available for eight of the 10 patients at this time. Among these eight patients, six have experienced viral relapse. Two patients have not relapsed; however, they have only reached the two week post-treatment time point.

“These data answer an important question about the use of GS-7977 and ribavirin for the treatment of genotype 1 null responder patients, suggesting that additional direct acting antivirals may be necessary to effectively treat this patient population,” said Norbert Bischofberger, PhD, Executive Vice President of Research and Development and Chief Scientific Officer. “We will continue to explore a number of therapeutic approaches to address this significant unmet medical need, including combinations with other oral antivirals.”

GS-7977 is a nucleotide analog polymerase inhibitor that is currently being studied for the treatment of chronic hepatitis C. A number of ongoing Phase 2 and Phase 3 studies are evaluating the safety and efficacy of the compound with and without RBV and/or pegylated interferon (Peg-IFN) in patients with genotypes 1-6 who are treatment naïve, treatment experienced, or have had a “null” response to Peg-IFN.

Genotype 2 and 3 data from the ELECTRON study were presented at the 62nd annual meeting of the American Association for the Study of Liver Diseases (The Liver Meeting 2011). Data from the genotype 1 null responder arm of the study will be presented at an upcoming scientific conference.

Results from ongoing studies in genotype 1 treatment-naïve patients will be available in the coming months. The first data evaluating GS-7977 plus RBV for 12 weeks in genotype 1 naïve patients will come from an arm of the QUANTUM study with 25 patients at the end of the first quarter of 2012. This will be followed in the second quarter by data from the ELECTRON study involving 25 patients and, early in the third quarter, data on GS-7977 and RBV treatment for 24 weeks from an arm of the QUANTUM study will become available.

Conference Call

Gilead will host a conference call today, February 17, 2012 at 8:00 a.m. Eastern Time, to discuss these study results. To access the live call, please dial 1-866-825-1709 (U.S.) or 1-617-213-8060 (international). The conference passcode number is 71588571. Telephone replay is available approximately one hour after the call through 11:59 p.m. Eastern Time, February 20, 2012. To access, please call 1-888-286-8010 (U.S.) or 1-617-801-6888 (international). The conference passcode number for the replay is 64278864. The information provided on the teleconference is only accurate at the time of the conference call, and Gilead will take no responsibility for providing updated information.

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 possibility of unfavorable results from the ELECTRON and QUANTUM studies, including in genotype 1 treatment-naïve patients, as well as other clinical trials evaluating GS-7977 with or without RBV and/or Peg-IFN or in combination with other antivirals; the anticipated timing for receiving clinical data and making regulatory filings; and Gilead’s ability to develop an all-oral antiviral regimen for HCV genotype 1 patients or a pangenotypic regimen for all HCV patients. As a result, GS-7977 may never be successfully commercialized. Further, Gilead may make a strategic decision to discontinue development of GS-7977 if, for example, it 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, 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.

For more information on Gilead Sciences, please visit the company’s website at www.gilead.com or call Gilead Public Affairs at 1-800-GILEAD-5 or 1-650-574-3000.

Source: Gilead Sciences, Inc.

Gilead Sciences, Inc.Susan Hubbard, 650-522-5715 (Investors)Amy Flood, 650-522-5643 (Media)