Eisai Co., Ltd. (Headquarters: Tokyo, President and CEO: Haruo Naito) and Eisai Inc. (Headquarters: New Jersey, Chairman and CEO: Hajime Shimizu) (collectively "Eisai") filed a lawsuit in August 2006 against Mutual Pharmaceutical Co., Inc. and United Research Laboratories, Inc. (collectively "Mutual") claiming that its submission of an abbreviated new drug application (ANDA) to the U.S. Food and Drug Administration (FDA) for Aricept ODT® (donepezil hydrochloride orally disintegrating tablets) would infringe Eisai's composition of matter patent.

On December 20, 2007 (U.S. EST), the U.S. District Court for the District of New Jersey issued a ruling dismissing the lawsuit against Mutual on the procedural grounds that there is no case or controversy between the parties, because Mutual did not make a certification challenging the patent and does not yet have FDA approval to market its product. The Court recognized that Mutual is required, by a stipulation entered between the parties and signed by the Court, to give Eisai 45 days' notice of any launch of a generic version of Aricept ODT®, and Eisai may during that 45-day period bring an action against Mutual for patent infringement and seek injunctive relief against Mutual's sales of any such product. Therefore, Mutual cannot market the generic version of Aricept ODT® immediately.

The Court did not address the substantive merits of Eisai's infringement action against Mutual. Eisai believes that its donepezil composition of matter patent is valid and enforceable until its expiration date of November 25, 2010, and that Mutual would clearly infringe its donepezil composition of matter patent if Mutual were to launch a generic version of Aricept ODT® in the United States prior to the expiration. Eisai intends to vigorously enforce and defend that patent.

The Court's ruling has no impact on Eisai's ongoing infringement action against Teva Pharmaceuticals for its ANDA for generic Aricept® (donepezil hydrochloride).

About Aricept®

While there is no cure for Alzheimer's disease, Aricept® can help slow the progression of symptoms, including memory loss. Once-a-day prescription Aricept® is indicated for the treatment of dementia of the Alzheimer's type. Efficacy has been demonstrated in patients with mild, moderate and severe Alzheimer's disease. Aricept® 5 mg and 10 mg are approved for the treatment of mild to moderate Alzheimer's disease. Aricept® 10 mg (after four to six weeks at 5 mg) is approved for the treatment of severe Alzheimer's disease. Aricept® is an acetylcholinesterase inhibitor and is believed to work by inhibiting the breakdown of acetylcholine, thereby increasing available levels of this chemical in the brain. There is an established association between the loss of acetylcholine, a brain chemical involved in memory and thinking, and Alzheimer's disease.

Aricept® is well-tolerated, but may not be for everyone. People at risk for stomach ulcers or who take certain other medications should tell their doctors because serious stomach problems, such as bleeding, may get worse. Some people who take Aricept® may experience fainting. Some people may have nausea, vomiting, diarrhea, bruising or not sleep well. Some people may have muscle cramps or loss of appetite or may feel tired. In studies, these were usually mild and temporary.

In a progressively degenerative disease such as Alzheimer's, improvement, stabilization or a less-than-expected decline over time is considered a positive response to treatment. These types of responses have been observed in patients treated with Aricept® in clinical trials for Alzheimer's disease. Individual responses to treatment vary.

About Eisai Co., Ltd.

Eisai Co., Ltd. is a research-based human health care (hhc) company that discovers, develops and markets products throughout the world. 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 approximately 10,000 people worldwide.

About Eisai Inc.

Eisai Inc., a U.S. pharmaceutical subsidiary of Eisai Co., Ltd., focuses its efforts in three therapeutic areas: neurology, gastrointestinal disorders and oncology/critical care. Established in 1995 and ranked among the top-20 U.S. pharmaceutical companies (based on retail sales), Eisai Inc. began marketing its first product in the United States in 1997 and has rapidly grown to become an integrated pharmaceutical business with sales of approximately $2.6 billion in fiscal year 2006 (year ended March 31, 2007). Eisai Inc. employs approximately 1,500 people at its headquarters in Woodcliff Lake, NJ, at its state-of-the-art pharmaceutical production and formulation research and development facility in Research Triangle Park, NC, and in the field. For more information about Eisai, please visit www.eisai.com.

SOURCE: Eisai Co., Ltd.; Eisai Inc.

CONTACT: Corporate Communications Department of Eisai Co., Ltd.,
+81-3-3817-5120; or Judee Shuler of Eisai Inc., +1-201-746-2241

Web site: http://www.eisai.com/