Nihon Eisai Co. Ltd. is a Japanese pharmaceutical company established in 1941. In 1944, merger with Sakuragaoka Research Laboratory resulted in creation of Eisai Co. Ltd. The American subsidiary of the company, Eisai Inc., was established in 1995.
In 1996, Eisai received approval from the United States Food and Drug Administration (USFDA) for Aricept (donepezil), a drug discovered in the company's labs and co-marketed with Pfizer. Three years later in 1999, the company received USFDA approval for Aciphex (rabeprazole), a drug co-marketed with Johnson & Johnson.
In September 2006, the company acquired four oncology products from Ligand Pharmaceuticals. In April 2007, Eisai acquired Exton, Pennsylvania-based Morphotek, a company developing therapeutic monoclonal antibodies for the treatment of cancer, rheumatoid arthritis, and infectious diseases.
In December 2007, Eisai acquired MGI Pharma, a company specializing in oncology, for $3.9 billion USD. This event brought Dacogen (decitabine), Aloxi (palonosetron), Hexalen (altretamine) for ovarian cancer, and the Gliadel Wafer (carmustine) for brain tumors into the Eisai product portfolio.
In 2009, Eisai received the Corporate Award from the National Organization for Rare Disorders (NORD) for the development of Banzel.