Section 05 · Monograph

Lecanemab

Reviewed Nov 2026FDA label

LeqembiAnti-amyloid mAb

Black Box Warning

Amyloid Related Imaging Abnormalities (ARIA): can occur as ARIA-E (edema/effusion) and ARIA-H (hemosiderin deposition/microhemorrhage)
ARIA usually occurs early in treatment and is usually asymptomatic, although serious and life-threatening events including seizure and status epilepticus can occur; ARIA can be fatal
Serious intracerebral hemorrhages greater than 1 cm in diameter have been observed
ApoE ε4 homozygotes have a higher incidence of ARIA, including symptomatic and serious ARIA, compared with heterozygotes and noncarriers (~15% of AD patients are homozygotes)
Test patients for ApoE ε4 status prior to initiation to inform ARIA risk
Obtain baseline brain MRI before initiating; enhanced clinical vigilance for ARIA recommended during the first 14 weeks of treatment
Additional caution when considering antithrombotic or thrombolytic medications given increased intracerebral hemorrhage risk

Treatment of Alzheimer's disease, in patients with mild cognitive impairment (MCI) or mild dementia stage of disease with confirmed presence of amyloid beta pathologyFDA-labeled

Humanized IgG1 monoclonal antibody directed against aggregated soluble (protofibril) and insoluble forms of amyloid beta
Preferentially binds large, soluble amyloid-beta protofibrils, thought to be highly neurotoxic species implicated in Alzheimer's pathogenesis
Reduces amyloid beta plaques in the brain, as demonstrated by amyloid PET imaging
Does not directly address tau pathology, neurodegeneration, or other downstream drivers of Alzheimer's dementia

Confirm amyloid beta pathology and ApoE ε4 genotype prior to starting treatment
Obtain baseline brain MRI within one year prior to initiating treatment
IV route: 10 mg/kg administered as an IV infusion over approximately 1 hour, once every 2 weeks
Subcutaneous (autoinjector) route: 500 mg once weekly (co-formulated with hyaluronidase)
Obtain MRIs prior to the 5th, 7th, and 14th infusions/doses to monitor for ARIA
After approximately 18 months, patients may transition to maintenance dosing: 10 mg/kg IV every 4 weeks, or 360 mg subcutaneously once weekly

No dosage adjustment required for mild-to-moderate renal or hepatic impairment; not studied in severe impairment

Serious hypersensitivity to lecanemab-irmb or to any excipients; reactions have included anaphylaxis and angioedema

No formal drug-drug interaction studies have been conducted
Concomitant antithrombotic therapy (anticoagulants, antiplatelet agents) may increase risk of intracerebral hemorrhage in the setting of ARIA
Use with thrombolytic agents carries increased hemorrhagic risk given possible ARIA-related microhemorrhages
As a monoclonal antibody, no CYP450-mediated interactions are expected

Infusion-related reactions (~26%): fever, chills, flushing, nausea, vomiting, blood pressure changes, most common with the first infusion
ARIA-H (microhemorrhage/hemosiderosis) in ~14% of treated patients
ARIA-E (edema/effusion) in ~13% of treated patients (vs ~2% placebo)
Headache (~11%)
Symptomatic ARIA can present as headache, confusion, visual disturbance, dizziness, gait disturbance, or seizure
Injection-site reactions with the subcutaneous autoinjector
Hypersensitivity reactions, including anaphylaxis (rare)

ApoE ε4 genotype testing prior to treatment initiation to stratify ARIA risk
Baseline brain MRI before starting therapy
Follow-up MRIs prior to the 5th, 7th, and 14th doses to screen for ARIA
Additional MRI at any time symptoms suggestive of ARIA occur
Clinical assessment for infusion-related reactions during and after each infusion
Review of concomitant antithrombotic/anticoagulant use
Periodic cognitive/functional assessment to gauge ongoing treatment benefit

No adequate human data available to establish drug-associated risk of major birth defects or miscarriage
No animal reproductive/developmental toxicity studies have been conducted
Alzheimer's disease typically does not occur in women of reproductive potential
No data on presence in human milk, effects on the breastfed infant, or on milk production