LEQEMBI

What it is

Lecanemab is a recombinant monolonal humanised antibody produced in Chinese Hamster Ovary (CHO) cells and has a molecular weight of approximately 150 kDa. Lecanemab is a humanised immunoglobulin gamma 1 (IgG1) monoclonal antibody that preferentially binds to large soluble amyloid beta (Aβ) protein aggregates, known as protofibrils, while still maintaining high affinity for fibrillar Aβ, which comprises amyloid plaques. LEQEMBI 100 mg/mL concentrated injection is a sterile, preservative-free, clear to opalescent, colourless to pale yellow solution.

Approved indications

— Adult patients with a diagnosis of mild cognitive impairment due to Alzheimer's disease — Adult patients with a diagnosis of mild dementia due to Alzheimer's disease LEQEMBI is indicated in patients who are apolipoprotein E ε4 (ApoE ε4) non-carriers or heterozygotes. Beta amyloid evidence consistent with Alzheimer's disease should be confirmed using a validated test prior to initiating treatment.

Dosing overview

The recommended dose of LEQEMBI is 10 mg/kg, administered as an intravenous infusion over approximately one hour, once every 2 weeks. LEQEMBI must be diluted in 250 mL of 0.9% Sodium Chloride Injection. LEQEMBI should be administered by a healthcare professional.

Key safety warnings

Monoclonal antibodies directed against aggregated forms of beta amyloid, including LEQEMBI, can cause amyloid related imaging abnormalities (ARIA), characterised as ARIA with oedema (ARIA-E) and ARIA with hemosiderin deposition (ARIA-H). ARIA usually occurs early in treatment and is usually asymptomatic, although serious and life-threatening events rarely can occur. Serious intracerebral haemorrhages, some of which have been fatal, have been observed in patients treated with this class of medications. ARIA-E can cause focal neurologic deficits that can mimic ischaemic stroke. LEQEMBI is not indicated in apolipoprotein E ε4 (ApoE ε4) homozygous patients. Patients who are ApoE ε4 homozygotes (approximately 15% of Alzheimer's disease patients) treated with this class of medications, including LEQEMBI, have a higher incidence of amyloid-related imaging abnormalities (ARIA) in the brain, including symptomatic, serious, and severe radiographic ARIA, compared to heterozygotes and non-carriers. Testing for ApoE ε4 status is required prior to initiation of treatment to inform the risk of developing ARIA. Hypersensitivity reactions, including angioedema, bronchospasm, and anaphylaxis, have occurred in patients who were treated with LEQEMBI. Promptly discontinue the infusion upon the first observation of any signs or symptoms consistent with a hypersensitivity reaction and initiate appropriate therapy. Infusion-related reactions have been observed with administration of LEQEMBI. The majority of these were mild to moderate. These reactions may be severe or life-threatening. This medicinal product is subject to additional monitoring in Australia. This will allow quick identification of new safety information.

Contraindications

Hypersensitivity to the active substance or to any of the excipients. Pre-treatment MRI findings of prior intracerebral haemorrhage greater than 1 cm, more than 2 microhaemorrhages, superficial siderosis or vasogenic oedema (ARIA-E), which are suggestive of cerebral amyloid angiopathy (CAA). Severe white matter disease. Any finding that could prevent a satisfactory MRI evaluation for safety monitoring. Treatment with LEQEMBI should not be initiated in patients receiving ongoing anticoagulant therapy.

Regulatory history

LEQEMBI lecanemab 200 mg/2 mL concentrated injection vial and LEQEMBI lecanemab 500 mg/5 mL concentrated injection vial were first listed on the Australian Register of Therapeutic Goods on 24 September 2025. The Pharmaceutical Benefits Scheme outcome in July 2024 was a withdrawal of the application for early Alzheimer disease.