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News Release

March 18, 2005

Company Contact:
Craig Johnson
TorreyPines Therapeutics, Inc.

858-623-5665, x158
Company Contact:
Corporate Communications Department
Eisai Co., Ltd
Media Contact:
Kathy W. Sweeney Mentus
858-455-5500, x230

Eisai and TorreyPines Therapeutics Announces
Second Major Discovery Alliance

Focus on Development Candidates to Treat Alzheimer's Disease

Tokyo, Japan and San Diego, California, March 18, 2005 -- TorreyPines Therapeutics, Inc. (President & CEO: Neil Kurtz, M.D.) and Eisai Co., Ltd. (President & CEO: Haruo Naito) today announced the signing of a research agreement involving Alzheimer's disease drug discovery.

The goal of the research performed by TorreyPines Therapeutics is to discover novel Alzheimer's disease modifying agents based on the study of the mechanism of the disease's pathogenesis. Under this agreement, Eisai will have exclusive rights of first negotiation and refusal for validated compounds discovered through the research. Eisai and TorreyPines Therapeutics may enter into drug development agreements involving certain validated compounds that meet a pre-determined set of criteria defined in the current agreement.

"We are pleased to work with Eisai once again in the field of Alzheimer's disease therapeutics," said Neil Kurtz, MD, President and CEO of Torrey Pines Therapeutics. "We look forward to advancing this program with Eisai's support, as well as continuing to work with them on our first research collaboration to identify genetically-validated pharmaceutical targets for Alzheimer's disease"

About Eisai Co., Ltd.

Eisai Co., Ltd. is a research-based human health care company, which discovers, develops and markets products in more than 30 countries. Eisai is a global leader in Alzheimer's disease research and treatment. Aricept(R), a symptomatic Alzheimer's disease treatment launched by Eisai in the United States in 1997, is currently sold in more than 70 countries worldwide. Through a global network of research facilities, manufacturing sites and marketing subsidiaries, Eisai actively participates in all aspects of the worldwide health care system. Eisai employs more than 7,000 people worldwide. Eisai common stock is listed on the Tokyo Stock Exchange and the Osaka Securities Exchange. For additional information, visit Eisai's web site at

About TorreyPines Therapeutics

TorreyPines Therapeutics is a biopharmaceutical company that discovers and develops breakthrough small molecule drugs to treat diseases and disorders of the central nervous system. Led by an accomplished management team, the company is leveraging novel drug targets and technologies to deliver new therapies for migraine, neuropathic pain and neurodegenerative disorders such as Alzheimer's disease. Its breakthrough therapies are intended to offer significant advantages over current therapies. Further information is available at