Leqembi (Lecanemab)

• Leqembi (lecanemab) is an anti‑amyloid monoclonal antibody used in the treatment of Alzheimer’s disease.
• Early symptomatic Alzheimer’s disease: improves clinical outcomes by reducing amyloid plaque burden.
• Mild cognitive impairment due to Alzheimer’s disease: may delay progression to dementia.
• Alzheimer’s disease (early stage): offers disease‑modifying therapy targeting amyloid pathology.

• Lecanemab is a humanized IgG1 monoclonal antibody that selectively binds soluble aggregated amyloid‑beta (Aβ) protofibrils and oligomers. By attaching to these soluble Aβ species, the antibody promotes their clearance via microglial phagocytosis and prevents further aggregation into insoluble plaques, thereby reducing cerebral amyloid burden and downstream neurotoxicity associated with Alzheimer’s disease. The reduction in plaque load is thought to translate into slower neurodegeneration and preservation of synaptic function.

Leqembi may cause a range of adverse reactions, most of which are often mild and transient, while some can be serious and require monitoring.

Common Side Effects

• Infusion‑related reactions: flushing, chills, shortness of breath, or rash occurring during or shortly after the IV infusion.
• Headache: mild to moderate headache that may appear within hours after treatment.
• Nausea: occasional nausea or upset stomach that may occur during the infusion period.

Serious or Rare Side Effects

• Amyloid‑related imaging abnormalities (ARIA): includes cerebral edema (ARIA‑E) or microhemorrhage (ARIA‑H) visible on MRI, potentially symptomatic.
• Severe hypersensitivity reactions: anaphylaxis, angioedema, or severe skin rash requiring immediate medical attention.
• Cerebral hemorrhage: rare intracerebral bleeding events that can be life‑threatening.

Leqembi requires careful monitoring and patient education to minimize risks.

• Monitor MRI for ARIA: baseline and periodic MRI scans are recommended.
• Assess renal function: adjust monitoring in patients with severe renal impairment.
• Avoid use in patients with known hypersensitivity to lecanemab or excipients.
• Educate patients about symptoms of ARIA: headache, confusion, visual changes.
• Concomitant anticoagulants: use caution due to bleeding risk.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Leqembi has a limited interaction profile, but certain co‑medications require attention.

Major Interactions (Avoid)

• Concurrent use with other amyloid‑targeting antibodies: increased risk of ARIA.
• Anticoagulants: heightened bleeding risk with ARIA‑H.
• Known hypersensitivity to lecanemab excipients: contraindicated.

Moderate Interactions (Monitor Closely)

• Antihypertensives: monitor blood pressure as infusion may cause transient changes.
• Non‑live vaccines: schedule at least 4 weeks apart from infusion.
• Other immunosuppressants: may affect immune response and infection risk.