| 1950 |
Nihon Eisai Co., Ltd.'s contraceptive suppository : Sampoon : , researched and developed during Japan's postwar baby boom, receives official approval from the Japanese government. |
| 1950 |
Nihon Eisai Co., Ltd. launches cardiotonic : Neophyllin : in Japan. |
| 1952 |
Nihon Eisai Co., Ltd. launches high-dosage vitamin B1 and B2 product : Chocola BB Tablets : in Japan. |
| 1952 |
Nihon Eisai Co., Ltd. launches motion sickness remedy : Travelmin : in Japan. |
| 1955 |
The company changes its name from Nihon Eisai Co., Ltd. to Eisai Co., Ltd., as it is known today. |
| 1957 |
Eisai rolls out its first three-year mid-term plan. |
| 1957 |
Eisai's Head Office building is completed in Tokyo. |
| 1961 |
Eisai opens its Taipei Office (now part of Eisai Taiwan Inc.), the company's first overseas branch, in Taiwan. |
| 1961 |
Eisai is publicly listed in the First Section of both the Tokyo and Osaka Stock Exchanges. |
| 1961 |
Gastrointestinal remedies : Saclon : and : Saclon Tablets : , recognizable for their distinct green hue even today, are launched in Japan. |
| 1964 |
Toyoji Naito receives the Japan Marketing Award, which recognizes people who have made a significant contribution to marketing and advertising in Japan. |
| 1966 |
The Kawashima Plant is completed in Gifu, central Japan. |
| 1966 |
Kawashima Plant opening ceremony. |
| 1966 |
Founder Toyoji Naito is appointed as chairman and Yuji Naito as company president. |
| 1966 |
A three-tier representative director system is introduced: Chairman Toyoji Naito, President Yuji Naito, and Executive Vice President Tatsuo Naito. |
| 1969 |
Youda Co., Ltd. is established as a pharmaceutical imports subsidiary in Taiwan. |
| 1970 |
PT Eisai Indonesia is established as a pharmaceutical manufacturing and sales subsidiary in Indonesia. |
| 1970 |
Toyoji Naito resigns as representative director and chairman to assume director and honorary chairman roles. |
| 1971 |
Toyoji opens the Naito Museum of Pharmaceutical Science and Industry, Japan's first pharmaceutical museum, in Gifu. |
| 1974 |
Eisai (Malaysia) Sdn. Bhd. and Hi-Eisai Pharmaceutical Inc. are established as pharmaceutical sales subsidiaries in Malaysia and the Philippines, respectively. |
| 1974 |
Metabolic cardiotonic : Neuquinon : is launched in Japan. |
| 1977 |
Naturally derived vitamin E product : Juvelux : is launched in Japan. |
| 1978 |
Eisai's founder Toyoji Naito passes away at age 89. |
| 1978 |
Peripheral neuropathy treatment : Methycobal : is launched in Japan. |
| 1979 |
Eisai Asia Regional Services Pte. Ltd. is established as a sales support and management services subsidiary in Singapore. |
| 1988 |
Eisai America, Inc. is established as a clinical research subsidiary in New Jersey, the United States. |
| 1997 |
Eisai Inc. North Carolina Plant is established as a pharmaceutical manufacturing and formulation R&D facility at Research Triangle Park in North Carolina, the United States. |
| 1997 |
Anti-Alzheimer's agent : Aricept : is launched in the United States, the United Kingdom and Germany. |
| 1999 |
Pariet : is launched under the brand name : AcipHex : in the United States. |
| 2002 |
Eisai Medical Research Inc. is established as a clinical research subsidiary in New Jersey, the United States. |
| 2006 |
Eisai acquires four anticancer agents from Ligand Pharmaceuticals Inc. in the United States. |
| 2007 |
Eisai acquires Morphotek Inc., a bioventure specialized in antibody research, in the United States. |
| 2008 |
Eisai acquires MGI Pharma Inc., an oncology biopharmaceutical company in the United States. |
| 2010 |
Halaven is launched in the United States. |
| 2010 |
H3 Biomedicine Inc. is established as a research subsidiary in the United States. |
| 2014 |
Fycompa is launched in the United States. |
| 2015 |
Lenvima is launched in the United States, Japan and Europe. |
| 2017 |
Collaboration agreement with Biogen to develop and commercialize investigational Alzheimer's disease treatments including aducanumab expanded. |
| 2018 |
Eisai agrees upon a strategic collaboration for Lenvima with Merck & Co., Inc., Kenilworth, N.J., U.S.A. |
| 2019 |
Eisai Center for Genetics Guided Dementia Discovery (G2D2) in Massachusetts, U.S., commences full-scale operation. |
| 2020 |
DAYVIGO (insomnia treatment) is launched in the United States and Japan. |
| 2023 |
Alzheimer’s disease treatment LEQEMBI is granted accelerated approval and launched in the United States. |
| 2023 |
LEQEMBI is granted traditional approval by the FDA. |
