Gilead Announces Preliminary Results From Phase II/III Studies for New Product to Treat or Prevent Influenza

Final Results to be Presented in the Fall

Foster City, CA -- June 30, 1998

Gilead Sciences, Inc. (Nasdaq: GILD) announced today the preliminary results of four Phase II/III clinical trials to test the efficacy and safety of GS 4104, the first oral neuraminidase inhibitor for influenza A and B, developed jointly by Gilead and F. Hoffmann-La Roche. GS 4104 was evaluated in international Phase II/III field trials, which enrolled over 2,900 people, during the 1997-1998 Northern Hemisphere flu season.

Preliminary data show that the trials appear to have met clinical expectations for the treatment and prevention of influenza. Early results indicate statistically significant differences between active and placebo arms for all primary endpoints, which included time to resolution of clinical symptoms in each of two treatment studies and the incidence of laboratory confirmed clinical influenza in two combined prophylaxis studies. The drug was well tolerated by the patients enrolled in these studies.

Based upon these encouraging results, Roche and Gilead are continuing the development program to support registration filings, anticipated in 1999. Final data are currently being analyzed. The companies plan to submit the complete results of the trials for presentation at the Interscience Conference on Antimicrobial Agents and Chemotherapy (September 24 - 26, San Diego), and the Infectious Diseases Society of America Conference (November 11 - 14, Denver).

Hoffmann-La Roche is a leading research-intensive pharmaceutical company with headquarters in Basel, Switzerland. It discovers, develops, manufactures and markets numerous important prescription drugs that improve, prolong and save the lives of patients with serious illnesses. Among the company's areas of therapeutic interest are virology, including HIV and AIDS, infectious diseases, cardiology, neurology, oncology, transplantation, dermatology and obesity.

Gilead Sciences is an independent biopharmaceutical company that seeks to provide accelerated treatment solutions for patients and the people who care for them. The Company discovers, develops and commercializes proprietary therapeutics for important viral diseases, including a currently marketed product for the treatment of CMV retinitis, a sight-threatening viral infection in patients with AIDS. In addition, the Company is developing products to treat diseases caused by HIV, hepatitis B virus and influenza virus. Gilead common stock is traded on The Nasdaq Stock Market under the symbol GILD.

This press release contains forward-looking statements, within the meaning of the Private Securities Litigation Reform Act of 1995, concerning the timing of potential registration filings for GS 4104 and presentation of clinical data at scientific conferences. Such statements are subject to certain risks and uncertainties, particularly those inherent in the process of discovering, developing and commercializing drugs that are safe and effective as human therapeutics. Actual results could differ materially from those projected in this release. 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, 1997 on file with the U.S. Securities and Exchange Commission, copies of which are available from Gilead.