Last reviewed 2026-04-25 · How we verify

Leqembi (LECANEMAB)

Leqembi works by binding to and removing amyloid beta A4 protein from the brain, which is thought to contribute to the progression of Alzheimer's disease.

Leqembi (LECANEMAB) is a small molecule amyloid beta-directed antibody developed by Eisai Inc. It targets the amyloid beta A4 protein, a key component in the development of Alzheimer's disease. Leqembi is FDA-approved for the treatment of Alzheimer's disease, with a commercial status as a patented product. Key safety considerations include the potential for amyloid-related imaging abnormalities (ARIA) and infusion-related reactions. Eisai Inc. remains the current owner of Leqembi.

At a glance

Mechanism of action

Lecanemab-irmb is humanized immunoglobulin gamma (IgG1) monoclonal antibody directed against aggregated soluble and insoluble forms of amyloid beta. The accumulation of amyloid beta plaques in the brain is defining pathophysiological feature of Alzheimers disease. LEQEMBI reduces amyloid beta plaques, as evaluated in Study and Study [see Clinical Studies (14) ].

Approved indications

• Alzheimer's disease

Boxed warnings

• WARNING: AMYLOID RELATED IMAGING ABNORMALITIES Monoclonal antibodies directed against aggregated forms of beta amyloid, including LEQEMBI, can cause amyloid related imaging abnormalities (ARIA), characterized as ARIA with edema (ARIA-E) and ARIA with hemosiderin deposition (ARIA-H). Incidence and timing of ARIA vary among treatments. ARIA usually occurs early in treatment and is usually asymptomatic, although serious and life-threatening events can occur. ARIA can be fatal. Serious intracerebral hemorrhage s > 1 cm, some of which have been fatal, have been observed in patients treated with this class of medications. Because ARIA-E can cause focal neurologic deficits that can mimic an ischemic stroke, treating clinicians should consider whether such symptoms could be due to ARIA-E before giving thrombolytic therapy to a patient being treated with LEQEMBI [see Warnings and Precautions ( 5.1 ), Adverse Reactions ( 6.1 )]. ApoE ε4 Homozygotes Patients who are apolipoprotein E ε4 (ApoE ε4) homozygotes (approximately 15% of Alzheimer’s disease patients) treated with this class of medications, including LEQEMBI, have a higher incidence of ARIA, including symptomatic, serious, and severe radiographic ARIA, compared to heterozygotes and noncarriers. Testing for ApoE ε4 status should be performed prior to initiation of treatment to inform the risk of developing ARIA. Prior to testing, prescribers should discuss with patients the risk of ARIA across genotypes and the implications of genetic testing results. Prescribers should inform patients that if genotype testing is not performed they can still be treated with LEQEMBI; however, it cannot be determined if they are ApoE ε4 homozygotes and at higher risk for ARIA [see Warnings and Precautions ( 5.1 )]. Consider the benefit of LEQEMBI for the treatment of Alzheimer’s disease and potential risk of serious adverse events associated with ARIA when deciding to initiate treatment with LEQEMBI [see Warnings and Precautions ( 5.1 ) and Clinical Studies ( 14 )]. WARNING: AMYLOID RELATED IMAGING ABNORMALITIES See full prescribing information for complete boxed warning. Monoclonal antibodies directed against aggregated forms of beta amyloid, including LEQEMBI, can cause amyloid related imaging abnormalities (ARIA), as ARIA with edema (ARIA-E) and ARIA with hemosiderin deposition (ARIA-H). ARIA is usually asymptomatic, although serious and life-threatening events can occur. ARIA can be fatal. Serious intracerebral hemorrhages > 1 cm have occurred in patients treated with this class of medications. ARIA-E can cause focal neurologic deficits that can mimic ischemic stroke. ( 5.1 , 6.1 ) ApoE ε4 Homozygotes Patients treated with this class of medications, including LEQEMBI, who are ApoE ε4 homozygotes have a higher incidence of ARIA, including symptomatic and serious ARIA, compared to heterozygotes and noncarriers. Testing for ApoE ε4 status should be performed prior to initiation of treatment to inform the risk of developing ARIA. Prior to testing, the risk of ARIA across genotypes and implications of genetic testing results should be discussed with patients. ( 5.1 ) Consider the benefit for the treatment of Alzheimer’s disease and risk of ARIA when deciding to treat with LEQEMBI. ( 5.1 , 14 )

Common side effects

• Infusion-related reactions
• ARIA-H microhemorrhages
• Headache
• Diarrhea
• Cough
• Nausea/Vomiting
• Rash
• Superficial siderosis of central nervous system
• Atrial fibrillation
• Lymphopenia or decreased lymphocyte count
• ARIA-E
• Erythema

Key clinical trials

• AHEAD 3-45 Study: A Study to Evaluate Efficacy and Safety of Treatment With Lecanemab in Participants With Preclinical Alzheimer's Disease and Elevated Amyloid and Also in Participants With Early Preclinical Alzheimer's Disease and Intermediate Amyloid (PHASE3)
• Georgia Memory Net Anti-Amyloid Monoclonal Antibody Registry
• Making Antibody Treatments More Effective in Early Alzheimer's Disease Using 3Tesla Magnetica Resonance (NA)
• DIAN-TU Amyloid Removal Trial (ART) in Dominantly Inherited Alzheimer's Disease (PHASE3)
• A Study to Evaluate Safety, Tolerability, and Efficacy of Lecanemab in Subjects With Early Alzheimer's Disease (PHASE2)
• Dominantly Inherited Alzheimer Network Trial: An Opportunity to Prevent Dementia. A Study of Potential Disease Modifying Treatments in Individuals at Risk for or With a Type of Early Onset Alzheimer's Disease Caused by a Genetic Mutation. Master Protocol DIAN-TU-001 (PHASE2,PHASE3)
• Dominantly Inherited Alzheimer Network Trial: An Opportunity to Prevent Dementia. A Study of Potential Disease Modifying Treatments in Individuals With a Type of Early Onset Alzheimer's Disease Caused by a Genetic Mutation (DIAN-TU) (PHASE2,PHASE3)
• A Study of E2814 With Concurrent Lecanemab Treatment in Participants With Early Alzheimer's Disease (PHASE2)

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

• Leqembi CI brief — competitive landscape report
• Leqembi updates RSS · CI watch RSS
• Eisai portfolio CI