Lecanemab

Lecanemab is indicated for the treatment of Alzheimer's disease in people who have mild cognitive impairment or mild dementia, but not in people who already have moderate or severe dementia. == Adverse effects ==

Lecanemab may cause harmful adverse effects. Lecanemab may cause amyloid-related imaging abnormalities (ARIA). ARIA is often asymptomatic, but serious and life-threatening events rarely may occur. ARIA most commonly presents as temporary swelling of the brain that usually resolves over time and may be accompanied by small spots of bleeding in or on the surface of the brain, though some people may have symptoms such as headache, confusion, dizziness, vision changes, nausea and seizure. However, one study indicates the brain volume reductions are consistent with amyloid plaque removal. == Pharmacology ==

Mechanism of action Lecanemab is a humanized monoclonal antibody consisting of a humanized version of a mouse antibody, mAb158, that recognizes protofibrils and prevents amyloid beta deposition in animal models of Alzheimer's disease. == History ==

In July 2022, the US Food and Drug Administration (FDA) accepted an application for accelerated approval for lecanemab. positive results from an ongoing phase III clinical trial. In November 2022, it was announced that the drug was a success in clinical trials and exceeded its goal in reaching primary endpoints. The efficacy of lecanemab was evaluated in a double-blind, placebo-controlled, parallel-group, dose-finding study of 856 participants with Alzheimer's disease. == Society and culture ==

Legal status Lecanemab was granted accelerated approval for medical use in the United States in January 2023, and traditional approval in July 2023. Lecanemab was approved for medical use in South Korea in May 2024, Mexico in December 2024,, the EU in April 2025, and Canada in October 2025. Australia In October 2024, the Australian Therapeutic Goods Administration (TGA) decided not to register lecanemab. In December 2024, Eisai requested reconsideration of the decision, and the TGA confirmed its decision to not register lecanemab in March 2025. Canada In October 2025, lecanemab was authorized in Canada. European Union In July 2024, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency recommended the refusal of the marketing authorization for lecanemab. The manufacturer requested re-examination. In November 2024, after re-examining its initial opinion, the CHMP recommended granting a marketing authorization to lecanemab (Leqembi) for treating mild cognitive impairment (memory and thinking problems) or mild dementia due to Alzheimer's disease (early Alzheimer's disease) in people who have only one or no copy of ApoE4, a certain form of the gene for the protein apolipoprotein E. Lecanemab was authorized for medical use in the European Union in April 2025. United Kingdom In August 2024, the Medicines and Healthcare products Regulatory Agency (MHRA) granted marketing authorization for England, Scotland, and Wales. It may not be used in people with two copies of the ApoE4 allele. Statistically, these people develop Alzheimer's disease more frequently and earlier, but also have a particularly high incidence of ARIA when treated with lecanemab. According to the MHRA, the risk outweighs the benefit for these people and genetic testing is recommended before starting treatment. The English branch of the National Health Service (NHS) announced it would not cover the costs of treatment, as according to draft guidance from the National Institute for Health and Care Excellence (NICE), the small benefit does not justify the cost of treatment. In July 2023, the FDA converted lecanemab to traditional approval. Reception In October 2023, lecanemab was designated as a "Do Not Use" drug by Public Citizen's Health Research Group. It had urged the FDA not to approve it, arguing that there were serious safety concerns and very small treatment benefits. with a company-estimated "per-patient societal value" of $37,600. After reviewing the clinical evidence and considering the treatments' other potential benefits, disadvantages, and contextual considerations noted above, the California Technology Assessment Forum unanimously concluded that lecanemab represents "low" long-term value of money. Names Lecanemab is the international nonproprietary name. == Research ==

Lecanemab was jointly developed by the companies Eisai, Biogen, BioArctic and is in clinical trials for the treatment of Alzheimer's disease. It has shown statistically significant but minor effectiveness, with studies suggesting a modest decrease in cognitive decline in Alzheimer's participants compared with a control group given a placebo instead. According to a phase III clinical trial (n = 1795), lecanemab has been associated with both ARIA-E (cerebral edema) and ARIA-H (microhaemorrhages, or small haemorrhages, and hemosiderosis) sub-types. Mild to moderate infusion-related reactions may also occur. == References ==