PHASE Ⅲ STUDY RESULTS SHOWED EISAI'S ERIBULIN MESYLATE SIGNIFICANTLY IMPROVED OVERALL SURVIVAL IN PATIENTS WITH LOCALLY RECURRENT OR METASTATIC BREAST CANCERGlobal EMBRACE Study Compared Eribulin to Treatment of Physician's Choice

Eisai Co., Ltd. (Headquarters: Tokyo, President & CEO: Haruo Naito, “Eisai”) announced that results of a Phase III study to be presented at the American Society of Clinical Oncology (ASCO) Annual Meeting showed that eribulin mesylate (“eribulin”), an investigational anticancer agent discovered and developed by the Company, statistically significantly improved median overall survival (OS) compared with treatment of physician's choice in heavily pre-treated locally recurrent and metastatic breast cancer patients.

Detailed results from this study will be presented in an oral session on the final day of the ASCO meeting on June 8, 2010 at 9:30 am. The study abstract has also been selected for presentation at the 2010 Best of ASCO® Meetings*, which will be held in San Francisco and Boston in the United States and in several countries around the world in the months following the ASCO Annual Meeting.

The Phase III “EMBRACE” Study (Eisai Metastatic Breast Cancer Study Assessing Physician's Choice Versus E7389) met its primary endpoint of overall survival, showing that patients who received eribulin survived a median of 2.5 months longer than patients who received treatment of physician's choice (13.12 months versus 10.65 months, respectively, p=0.04). Results from EMBRACE also showed that the secondary endpoints of progression free survival (PFS) and overall response rate (ORR) were consistent with the primary endpoints.

Patients in the study were randomized in a two-to-one ratio to receive either a 1.4 mg/m² dose of eribulin administered intravenously for two-to-five minutes on days 1 and 8 of a 21-day treatment cycle or treatment of physician's choice. Treatment of physician's choice was defined as any single agent chemotherapy, hormonal treatment or biological therapy approved for the treatment of cancer or palliative or radiotherapy administered according to local practice. Participants in the study ranged in age from 27 to 85, with a median age of 55. Of the 762 patients in the study, 16 percent of patients had HER2 positive breast cancer and 19 percent had breast cancer that was negative for estrogen, progesterone and HER2 receptors. The most common grade 3 or grade 4 adverse events experienced by eribulin treated patients were asthenia, or fatigue (7.6%), neutropenia, or low white blood cell counts (44%) and peripheral neuropathy, or numbness and tingling in different parts of the body (8.4%).

Worldwide, more than one million women are diagnosed with breast cancer every year. Approximately 50 percent of women worldwide initially diagnosed with breast cancer are expected to develop recurrent or metastatic disease within 15 years of their first diagnosis. Only one in five women with metastatic breast cancer survives longer than five years.

Eribulin is an investigational compound being evaluated as a potential treatment for locally recurrent or metastatic breast cancer. A microtubule dynamics inhibitor, eribulin is a synthetic analog of halichondrin B, which is derived from a natural product isolated from a marine sponge. On March 30, 2010, Eisai submitted regulatory applications for approval of eribulin for the treatment of locally recurrent or metastatic breast cancer to health authorities in Japan, the United States and the European Union (EU). The New Drug Application (NDA) was granted priority review status by the U.S. Food and Drug Administration (FDA) on May 28, 2010.

Eisai defines oncology as a therapeutic area of focus and is committed to developing novel anti-cancer agents such as eribulin and treatments for supportive care. Through these efforts, Eisai will make further contributions to addressing the diversified needs of and increasing the benefits to patients and families affected by cancer as well as healthcare professionals.