Gilead Receives Complete Response Letter from U.S. Food and Drug Administration for Aztreonam Lysine for Inhalation, an Investigational Treatment for Cystic Fibrosis

FOSTER CITY, Calif.--(BUSINESS WIRE)--Sept. 16, 2008--Gilead Sciences, Inc. (Nasdaq:GILD) today announced that the company has received a complete response letter from the U.S. Food and Drug Administration (FDA) for its New Drug Application (NDA) for aztreonam lysine for inhalation, an investigational therapy in development for people with cystic fibrosis who have Pseudomonas aeruginosa (P. aeruginosa).

In this letter, the FDA informed Gilead that the review of the company's NDA has been completed. The agency stated that they cannot approve the application in its current form and an additional clinical study will be required. Gilead will continue its dialogue with the FDA to determine whether further analyses of existing data could lead to approval, or whether the company will need to conduct the additional study as stated in the letter.

"Cystic fibrosis-related pseudomonal infections represent an area of significant and urgent unmet medical need. Our goal is to work with the FDA to deliver this product to the medical community and to people living with cystic fibrosis as quickly as possible," said John C. Martin, PhD, Chairman and CEO, Gilead Sciences. "The FDA has not raised any significant concerns regarding the safety profile of aztreonam lysine. Therefore, we will continue our expanded access program for those individuals who have limited treatment options and are at risk of disease progression."

Gilead submitted its NDA for aztreonam lysine for inhalation to the FDA on November 16, 2007. Marketing applications for aztreonam lysine for inhalation are under review by regulatory agencies in the European Union, Australia, Switzerland, Turkey and Canada.

About Aztreonam Lysine for Inhalation

Aztreonam lysine for inhalation is an antibiotic candidate for people with cystic fibrosis who have P. aeruginosa. Aztreonam has potent activity against Gram-negative bacteria such as P. aeruginosa. Aztreonam formulated with arginine is a FDA-approved agent for intravenous administration. Aztreonam lysine is a proprietary formulation of aztreonam developed specifically for inhalation. It has been designated with orphan drug status in the United States and Europe.

In August 2007, Gilead initiated an expanded access program (EAP) to provide aztreonam lysine for inhalation to people with cystic fibrosis and P. aeruginosa who have significantly compromised lung function despite currently available therapies.

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.

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 existing data from any ongoing or from any further clinical trials that we may commence to satisfy FDA concerns will not support FDA approval of aztreonam lysine for inhalation and that this may cause Gilead to incur considerable expense, would lead to further delays or cause the company to abandon further development of the product. In addition, any further clinical trials would cause Gilead to incur significant expense. There is also the risk that health authorities in other countries where new drug applications are pending will undertake similar additional reviews which would compound the risks described above. 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 its Quarterly Report on Form 10-Q for the second quarter of 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.

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.

CONTACT: Gilead Sciences, Inc. Susan Hubbard, 650-522-5715 (Investors) Patrick O'Brien, 650-522-1936 (Investors) Amy Flood, 650-522-5643 (Media) SOURCE: Gilead Sciences, Inc.