Lecanemab (Leqembi)
Lecanemab is a humanized antibody. It binds soluble amyloid-beta 'protofibrils' (and, less so, fibrous plaques). In the phase 3 CLARITY-AD trial, it slowed decline on a standard dementia scale (CDR-SB) by 0.45 points over 18 months in early Alzheimer's, versus placebo. The FDA granted accelerated approval on 6 January 2023, and full approval on 6 July 2023. The European Medicines Agency first refused it in July 2024. But it reversed after a re-examination. The European Commission then approved it on 15 April 2025. The approval is restricted to people who are not APOE ε4 homozygotes. (So non-carriers and one-copy carriers only.) The main safety concern is 'ARIA': amyloid-related imaging abnormalities. These are either brain swelling (ARIA-E) or micro-bleeds (ARIA-H). They are much more frequent and severe in people with two ε4 copies. On 30 August 2025, the FDA approved a once-weekly at-home autoinjector (LEQEMBI IQLIK) for maintenance. It is the first anti-amyloid antibody you can give yourself at home. Cost-effectiveness bodies have pushed back. The UK's NICE issued final guidance on 19 June 2025 not recommending it for routine NHS use (a third consultation opened in 2026). And Germany's G-BA found no added benefit on 19 February 2026.
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