U.S. Patent Office Confirms First of Four Viread(R) Patents

Review Ongoing for Remaining Three Patents
FOSTER CITY, Calif., May 20, 2008 (BUSINESS WIRE) -- Gilead Sciences, Inc. (Nasdaq:GILD) today announced that the U.S. Patent & Trademark Office (PTO) has completed the first of four reexamination proceedings and has confirmed the patentability of U.S. Patent No. 6,043,230, which covers a method of use for Viread (tenofovir disoproxil fumarate). The U.S. PTO has not announced its ruling on the remaining three Viread patents under review.

The four U.S. PTO review proceedings were initiated July 2007 in response to a challenge issued by the Public Patent Foundation (PUBPAT) in March 2007 for U.S. Patents No. 5,922,695; 5,977,089; 5,935,946; and 6,043,230. In its request for the reexaminations, PUBPAT claimed that prior art existed that would have impacted the issuance of the original patents.

Upon completion of the first reexamination proceeding, the U.S. PTO has confirmed the patentability of U.S. Patent No. 6,043,230 with no reduction in the scope of the claims.

"We are pleased that the U.S. PTO, following a detailed and comprehensive analysis, has concluded this first reexamination," said Gregg Alton, Senior Vice President and General Counsel. "We have always believed that the U.S. PTO would recognize that Viread is a novel product, and we remain confident that the office will rule similarly on the remaining three patents under review."

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 Australia.

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 uncertainty related to the expected timing of the U.S. PTO's ruling on the remaining three Viread patents, the risk that the U.S. PTO may narrow or invalidate some or all of the original claims in such patents and the risk of the ultimate enforceability of this patent should it be challenged in a court of law. 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, 2007 and Quarterly Report on Form 10-Q for the quarter ended March 31, 2008, 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.

Viread is a registered trademark of Gilead Sciences, Inc.

For more information on Gilead, please call the Gilead Public Affairs Department at 1-800-GILEAD-5 (1-800-445-3235) or visit www.gilead.com

SOURCE: Gilead Sciences, Inc.

Gilead Sciences, Inc.
Patrick O'Brien, 650-522-1936, Investors
Amy Flood, 650-522-5643, Media