Definition and Overview
Anti-amyloid antibody therapy is a monoclonal antibody treatment designed to target and remove beta-amyloid protein, the core pathology of Alzheimer's disease. Unlike existing treatments that relieve symptoms, it is a disease-modifying therapy that directly reduces the causative agent of the disease.
In Alzheimer's disease, beta-amyloid aggregates in the brain, forming amyloid plaques and causing nerve damage. Anti-amyloid antibodies bind to this amyloid and promote immune-mediated clearance, ultimately lowering the amyloid burden in the brain. Representative drugs include lecanemab and donanemab and are administered by intravenous injection.
Mechanism of Action
Lecanemab binds first to soluble amyloid protofibrils in the aggregation stage, and donanemab binds to amyloid in deposited senile plaques. When the antibody binds to amyloid, its removal through microglia is promoted and the brain amyloid PET signal decreases. It is based on the hypothesis that amyloid clearance leads to delayed clinical progression, and in a phase 3 trial, delayed cognitive decline was observed along with amyloid reduction on PET.
Indications
The target is early-stage Alzheimer's disease, which ranges from mild cognitive impairment to mild dementia. Before treatment, brain amyloid positivity must be confirmed using amyloid PET or cerebrospinal fluid biomarkers, and amyloid-negative or moderately advanced dementia is not an indication. Appropriate use recommendations include baseline MRI, APOE genotyping, and review of bleeding risk.
clinical evidence
In the CLARITY-AD phase 3 trial of lecanemab, the deterioration of the Clinical Dementia Scale Total Score (CDR-SB) at 18 months was approximately 27% slower than placebo, and significant differences were also seen in cognitive and daily function auxiliary indicators. In the TRAILBLAZER-ALZ 2 trial of donanemab, cognitive and functional deterioration was significantly delayed compared to placebo in the Integrated Alzheimer's Disease Rating Scale (iADRS) and CDR-SB.
The effect of both tests is to slow the progression and does not restore damaged cognitive function to normal. A decision must be made that considers the benefits of treatment, the risk of side effects, and the burden of regular injections and imaging tests.
side effects
The most noteworthy side effect is amyloid-related imaging abnormalities (ARIA). ARIA is divided into cerebral edema due to increased vascular permeability (ARIA-E) and microhemorrhage/superficial iron deposition (ARIA-H). It is mostly asymptomatic, but may be accompanied by headache, dizziness, confusion, and visual symptoms, and rarely has a severe course. Therefore, regular MRI monitoring is necessary during treatment.
ARIA risk is high in APOE ε4 carriers, especially homozygotes. The risk of bleeding increases if you are taking anticoagulants, have multiple microbleeds, or have cerebral amyloid angiopathy. Infusion reactions related to injections may also occur.
Limitations and Considerations
This treatment is limited to early-stage patients and requires confirmation of amyloid biomarkers for diagnosis and repeated MRI surveillance during treatment. The effect is a mild delay in progress, and comes with the burden of cost, accessibility, and safety monitoring. Decisions based on appropriate target selection, risk assessment, and sufficient explanation are important.