lecanemab, human monoclonal antibody used for the treatment of Alzheimer disease. Lecanemab clears away and blocks the formation of a sticky protein in the brain known as amyloid beta. Abnormal deposits of amyloid, called amyloid plaques, are toxic to neurons and eventually cause neuronal death and a loss of neuronal connections, which affects cognition and memory. By reducing amyloid levels, lecanemab can slow disease progression in some patients with mild cognitive impairment or early-stage Alzheimer disease.
Monoclonal antibodies are a type of antibody produced from the cloning of a single immune cell via artificial means, such as genetic engineering and related techniques. Such antibodies are typically engineered to target a single antigen (foreign entity), making them highly specific. Lecanemab was developed as a humanized version of a mouse monoclonal antibody known as mAb158, which targets soluble amyloid beta deposits. The mouse version, originally generated at Uppsala University, was developed by scientists at Swedish biotechnology company BioArctic AB and its partner, Japanese pharmaceutical company Eisai Co., Inc., into a humanized form that has a high affinity for soluble amyloid beta protofibrils. (Of the various forms of amyloid beta in the human body, the soluble and protofibril forms are the most neurotoxic.)
Lecanemab was approved under the name Leqembi in 2023 by the U.S. Food and Drug Administration (FDA) for use in patients with mild cognitive impairment or early-stage Alzheimer disease, which is characterized by mild dementia. The approval was based on evidence from clinical trials, in which treatment with lecanemab was associated with significant reductions in amyloid levels in the blood, brain, and cerebrospinal fluid. Moreover, patients given lecanemab experienced less decline in cognitive function than patients who were given a placebo.
Lecanemab can produce side effects: mainly headache, infusion-related reactions, and amyloid-related imaging abnormalities (ARIA). Infusion-related reactions are usually evident in the emergence of flulike symptoms. Compared with other side effects, ARIA is far more rare but also more serious and potentially life-threatening. It is characterized by temporary swelling in the brain and, in some instances, by minor bleeding in or on the brain surface. It may be accompanied by such symptoms as confusion, dizziness, nausea, and seizure.