Press Releases

November 29, 2004

Gilead and Achillion Announce Collaboration for the Development and Commercialization of Achillion's Hepatitis C Compounds

FOSTER CITY, Calif. & NEW HAVEN, Conn.--(BUSINESS WIRE)--Nov. 29, 2004--Gilead Sciences (Nasdaq:GILD) and Achillion Pharmaceuticals today announced that the companies have signed an exclusive agreement granting Gilead worldwide rights for the research, development and commercialization of certain Achillion compounds for the treatment of infection with the hepatitis C virus (HCV). The compounds, small molecule inhibitors of HCV replication, are believed to act through a novel mechanism of action involving HCV protease. In this collaboration, Achillion will continue development of the compounds, according to a mutually agreed upon development plan, through completion of a proof-of-concept clinical study in HCV-infected patients. Following the proof-of-concept study, Gilead will assume full responsibilities and costs associated with development and commercialization for compounds warranting further development.

Under the terms of the agreement, Gilead will pay to Achillion a $5 million upfront license payment and will purchase $5 million of equity. In addition, Gilead will provide partial funding through the completion of the proof-of-concept study. Achillion could also earn milestone payments in excess of $100 million under the agreement, based upon the achievement of certain development, regulatory and commercial goals, and will have the option to participate in U.S. commercialization efforts for any future products arising from this collaboration. Achillion's milestone payments could increase substantially assuming progress is made on multiple related compounds. Gilead will receive exclusive worldwide license rights and will pay Achillion a royalty on net sales of future products arising from the collaboration.

"Gilead and Achillion share a commitment to developing advanced therapeutics for the treatment of significant unmet medical needs, such as HCV," said John C. Martin, Ph.D., President and Chief Executive Officer of Gilead Sciences. "Achillion's drug discovery and development expertise, particularly in identifying unique drug targets with the potential to address drug resistance, makes the company an ideal partner for Gilead. We believe Achillion's compounds work through a novel mechanism, making them excellent potential candidates for HCV combination therapy regimens. We look forward to collaborating with Achillion to rapidly advance new compounds for the treatment of HCV."

"This collaboration highlights the strength of Achillion's discovery and development capabilities and its ability not only to create important new compounds for treatment of life-threatening infectious diseases, but also to advance such compounds into clinical proof-of-concept studies. Gilead's commercial franchise and expertise in antiviral drug development has made the company our strongly preferred partner to advance and commercialize compounds from our exciting HCV program," stated Michael Kishbauch, Chief Executive Officer of Achillion. "We believe that this agreement provides an important catalyst to this program while also freeing up resources to advance our own HIV and antibacterial programs."

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 3 million Americans are now estimated to be chronically infected with the hepatitis C virus. HCV 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, Inc. is a biopharmaceutical company that discovers, develops and commercializes therapeutics to advance the care of patients suffering from life-threatening diseases worldwide. The company has seven marketed products, and focuses its research and clinical programs on anti-infectives. Headquartered in Foster City, CA, 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.

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 the companies' ability to move compounds into the clinic and to successfully discover, develop and/or commercialize any compounds under the agreement. 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, 2003 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 Pharmaceuticals, please visit the company's web site at www.achillion.com or call Achillion at 1-203-624-7000.

CONTACT:
Gilead
Amy Flood, 650-522-5643 (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