Eisai Co., Ltd. (Headquarters: Tokyo, CEO: Haruo Naito, “Eisai”) and Biogen Inc. (Nasdaq: BIIB, Corporate headquarters: Cambridge, Massachusetts, CEO: Christopher A. Viehbacher, “Biogen”) announced that the humanized anti-soluble aggregated amyloid-beta (Aβ) monoclonal antibody “LEQEMBI®” has been launched in South Korea. LEQEMBI received the Ministry of Food and Drug Safety (MFDS) approval in May 2024 for treatment in adult patients with mild cognitive impairment due to Alzheimer’s disease (AD) or mild AD dementia (early AD).

LEQEMBI selectively binds to soluble Aβ aggregates (protofibrils*), as well as insoluble Aβ aggregates (fibrils) which are a major component of Aβ plaques in AD, thereby reducing both Aβ protofibrils and Aβ plaques in the brain. LEQEMBI is the first approved treatment shown to reduce the rate of disease progression and to slow cognitive and functional decline through this mechanism.

It is estimated there were approximately 900,000 dementia patients in South Korea in 2021,1 with one in ten people over the age of 65 suffering from dementia,1 and one in five from mild cognitive impairment (MCI).2 It is reported that Alzheimer’s dementia patients account for about 70% of all dementia patients.2 The average annual nursing care/medical costs per dementia patient is estimated to be 21.1 million South Korean Won (KRW), while the cost for patients with severe dementia reaches 33.1 million KRW.1

Eisai serves as the lead of LEQEMBI development and regulatory submissions globally with both Eisai and Biogen co-commercializing and co-promoting the product and Eisai having final decision-making authority. In South Korea, Eisai Korea Inc. will distribute the product and conduct information provision activities.

Eisai Korea Inc. has been a pioneer in the field of dementia for many years, focusing on activities such as raising disease awareness. In recent years, Eisai Korea Inc. has been working with various stakeholders, including healthcare professionals, academic societies, patient groups, care centers, health checkup companies, and diagnostic companies, to create a dementia ecosystem that promotes AD awareness and early diagnosis/treatment. Eisai Korea Inc. will first launch this drug in the private market, including the establishment of a Patient Assistance Program, to deliver lecanemab to patients awaiting the treatment, aiming to make an impact not only on patients but also on their caregiving families and South Korean society.

* Protofibrils are believed to contribute to the brain injury that occurs with AD and are considered to be the most toxic form of Aβ, having a primary role in the cognitive decline associated with this progressive, debilitating condition.3 Protofibrils cause injury to neurons in the brain, which in turn, can negatively impact cognitive function via multiple mechanisms, not only increasing the development of insoluble Aβ plaques but also increasing direct damage to brain cell membranes and the connections that transmit signals between nerve cells or nerve cells and other cells. It is believed the reduction of protofibrils may prevent the progression of AD by reducing damage to neurons in the brain and cognitive dysfunction.