Lecanemab (Leqembi)
Lecanemab is the first anti-amyloid monoclonal antibody to receive full FDA approval for early Alzheimer disease, based on the Clarity AD trial. Its 2026 role is as disease-modifying therapy for patients with biomarker-confirmed amyloid pathology in the MCI or mild-dementia stage of AD, requiring structured MRI monitoring for ARIA.
- Mechanism of action
- Humanized IgG1 monoclonal antibody that binds soluble amyloid-beta protofibrils, promoting clearance of amyloid plaques.
- Administration route
- Intravenous infusion every 2 weeks (SC weekly formulation under review 2026)
FDA-approved indications (2026)
Early Alzheimer disease
Mild cognitive impairment or mild dementia stage of AD with confirmed amyloid pathology (PET or CSF).
Dosing: adult, renal, and hepatic
| Population | Dose |
|---|---|
| Standard | 10 mg/kg IV every 2 weeks. Consider maintenance every 4 weeks after 18 months (emerging 2025–2026 data). |
| Hepatic / renal impairment | No specific adjustment; limited data in advanced disease. |
| Subcutaneous weekly (investigational) | SC autoinjector under regulatory review in 2026 (flagged: 2026-uncertain). |
Contraindications and boxed warnings
Contraindications
- Serious hypersensitivity (including anaphylaxis/angioedema) to lecanemab.
Boxed warnings
- Amyloid-related imaging abnormalities (ARIA-E edema, ARIA-H hemorrhage) — can be serious or life-threatening, including intracerebral hemorrhage in patients on anticoagulants.
2026 guideline and pivotal trial position
The AAN 2024 appropriate-use recommendations and Alzheimer Association 2025 position limit lecanemab to adults with biomarker-confirmed early AD and reasonable ARIA surveillance capacity. Pre-treatment MRI and APOE4 genotyping are advised. APOE4 homozygotes have the highest ARIA risk and require explicit shared decision-making. 2026 guidance continues to discourage routine anticoagulant co-administration.
Clarity AD (CLARITY AD, 2023)
27% slowing of clinical decline (CDR-SB) at 18 months in early AD.
Clarity AD open-label extension (2025–2026)
Continued benefit over 3 years; no new safety signals (flagged: 2026 data continuing to mature).
Cross-system reasoning
Lecanemab introduces neurology-hematology coordination previously uncommon in dementia care: anticoagulation status, recent major stroke, cerebral microbleeds on MRI, and APOE4 status all modify ARIA risk. In a patient on warfarin or a DOAC with atrial fibrillation, the decision to start lecanemab becomes a multi-specialty discussion between neurology and cardiology, with meaningful implications for stroke prevention strategy. Infusion-reaction management and MRI infrastructure are practical prerequisites.
Key references
Related clinical reading
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This reference is for US-licensed physicians and is not a substitute for the full FDA prescribing information. Dosing in special populations, drug interactions, and emerging safety information should be verified against the current manufacturer label and society guidelines before prescribing.