Gilead and Achillion Announce Initiation of Phase I Clinical Trial Evaluating GS 9132 for the Treatment of Hepatitis C

FOSTER CITY, Calif. and NEW HAVEN, Conn.--(BUSINESS WIRE)--Aug. 15, 2005--Gilead Sciences (Nasdaq:GILD) and Achillion Pharmaceuticals today announced that the companies have begun dosing patients in a Phase I study of GS 9132, also known as ACH-806. Gilead and Achillion are investigating GS 9132 for the treatment of hepatitis C.

The Phase I trial is a double-blind, randomized, placebo-controlled dose-escalation study. The goal of the trial is to evaluate the pharmacokinetics, tolerability and safety of single escalating doses of GS 9132 in healthy volunteers. The study will take place in the United States and will enroll approximately 20 subjects.

In November 2004, Gilead and Achillion established an agreement granting Gilead worldwide rights for the research, development and commercialization of certain Achillion compounds for the treatment of hepatitis C. GS 9132 is a small molecule inhibitor of hepatitis C virus (HCV) replication, which works through a novel mechanism of action involving HCV protease. GS 9132 was discovered by Achillion, and the company completed the initial work necessary to move the compound into clinical development.

"Gilead and Achillion share a commitment to advancing novel compounds with the potential to address the unmet medical need that exists for patients chronically infected with hepatitis C," said Norbert Bischofberger, PhD, Executive Vice President, Research and Development, Gilead Sciences. "Achillion's leadership in the early clinical development of this compound, and work to ensure rapid progress toward the Investigational New Drug application filing earlier this summer, has allowed us to advance this important clinical program. We look forward to our continued collaboration."

"We are excited about the novel mechanism of action of GS 9132 involving HCV protease, and we are looking forward to establishing the safety profile of this compound in humans," stated Milind Deshpande, PhD, Chief Scientific Officer of Achillion. "Gilead has been a tremendous partner through the early part of our agreement and we look forward to benefiting from their clinical experience and building upon our relationship as Achillion brings GS 9132 through proof of concept studies."

About Hepatitis C

Hepatitis C is a viral liver disease, caused by infection with the hepatitis C virus. Globally, more than 170 million people have chronic hepatitis C. About three million Americans are now estimated to be chronically infected with HCV. Chronic hepatitis C is a leading cause of cirrhosis, a common cause of hepatocellular carcinoma, and is the leading cause of liver transplantation in the United States.

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.

About Achillion

Achillion is an innovative pharmaceutical company dedicated to bringing important new treatments to patients with infectious disease. The company's proven discovery and development teams have advanced multiple product candidates with novel mechanisms of action. Achillion is focused on solutions for the most challenging problems in infectious disease -- HIV, hepatitis and resistant bacterial infections.

As an investigational compound, GS 9132 has not yet been determined safe or efficacious in humans for its ultimate intended use.

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 risks related to Gilead's ability to develop and commercialize this product. For example, the data from this trial may not warrant further development of this compound and initiating and completing clinical trials may take longer or cost more than expected. 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 the Gilead Annual Report on Form 10-K for the year ended December 31, 2004 and in the company's Quarterly Reports on Form 10-Q, which are on file with the U.S. Securities and Exchange Commission. All forward-looking statements are based on information currently available to Gilead, and neither company assumes any obligation to update any such forward-looking statements.

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

For more information on Achillion, please visit the company's web site at www.achillion.com or call Achillion at 1-203-624-7000.

CONTACT: Gilead Sciences
Erin Edgley, 650-522-5635 (Media)
Susan Hubbard, 650-522-5715 (Investors)
or
Achillion
Kari Lampka, 508-647-0209 (Media)
Mary Kay Fenton, 203-624-7000 (Investors)

SOURCE: Gilead Sciences