Health authorities in Brazil have authorised the use of lecanemab, marketed as Leqembi, a biological medicine developed to treat patients in the early stages of Alzheimer’s disease. The decision, announced by the National Health Surveillance Agency (Anvisa), places Brazil among dozens of countries that have approved the drug, while also reigniting scientific and policy debates about effectiveness, safety and access.
Leqembi is indicated exclusively for individuals with mild cognitive impairment or mild dementia associated with Alzheimer’s disease. According to Brazilian specialists, this restriction reflects the mechanism of action of the drug and the clinical evidence available to date. Patients must still retain functional independence in daily activities, such as personal hygiene and basic self-care, despite experiencing noticeable memory and cognitive changes.
Targeting amyloid pathology
Lecanemab is a monoclonal antibody designed to bind to beta-amyloid, a protein that accumulates abnormally in the brains of people with Alzheimer’s disease. These deposits form plaques that are widely regarded as a hallmark of the condition. By targeting beta-amyloid, the therapy aims to reduce plaque burden and, in doing so, slow the underlying disease process rather than relieve symptoms.
The drug represents the second anti-amyloid antibody approved in Brazil, following the authorisation of donanemab in 2024. Although both medicines belong to the same therapeutic class, Brazilian neurologists note that they interact with beta-amyloid at different stages of its formation. At present, there are no direct comparative clinical trials between the two treatments.
Clinical outcomes and scientific debate
From a clinical perspective, lecanemab does not produce immediate or obvious improvements in memory or cognition. Instead, studies with follow-up periods of approximately 18 months indicate a modest but measurable reduction in the rate of cognitive and functional decline when compared with placebo groups.
This outcome has fuelled ongoing academic discussion. While numerous studies suggest that removing amyloid plaques can slow disease progression, the precise role of beta-amyloid in causing Alzheimer’s remains contested. Research published in journals such as The New England Journal of Medicine and Alzheimer’s Research & Therapy has shown that anti-amyloid therapies may alter disease trajectories, though the magnitude and long-term relevance of these effects continue to be evaluated.
Brazilian researchers involved in dementia studies emphasise that, although the clinical benefit is considered limited, the therapy represents an incremental advance rather than a cure.
Treatment protocol and diagnostic requirements
In Brazil, treatment with lecanemab must be administered in specialised clinical settings. The recommended dose is 10 mg per kilogram of body weight, delivered via intravenous infusion every two weeks, with each session lasting around one hour.
Before initiating therapy, patients are required to undergo confirmatory testing to demonstrate the presence of amyloid pathology. This can be achieved through amyloid PET imaging or analysis of cerebrospinal fluid. These assessments also help identify contraindications, including pre-existing brain haemorrhages or cerebral oedema.
Safety considerations and contraindications
Anvisa has highlighted important safety restrictions. Individuals who carry the APOE ε4 genetic variant, particularly those with two copies of the gene, face a higher risk of adverse neurological effects, such as brain swelling and microhaemorrhages. As a result, genetic testing is mandatory prior to treatment in Brazil, and patients with this profile are not eligible for lecanemab.
Other reported adverse events include headaches, imaging-detected cerebral oedema and small intracerebral bleeds. Patients using anticoagulant medication are also excluded due to increased bleeding risk. Brazilian guidelines further recommend a recent magnetic resonance imaging (MRI) scan to rule out vascular brain disease before treatment begins.
Challenges for public health adoption
Despite regulatory approval, the incorporation of lecanemab into Brazil’s public healthcare system remains unlikely in the near term. The combination of high costs, complex logistics and limited infusion infrastructure presents significant barriers. While pricing in Brazil has not yet been disclosed, annual treatment costs in the United States are reported at approximately US$26,000.
Specialists argue that, for now, the priority is to build clinical experience within specialised centres and ensure healthcare teams are adequately trained to monitor patients and manage potential complications.
In Brazil, the approval of Leqembi underscores both the progress and the limitations of current Alzheimer’s therapies. It reflects a cautious step forward in disease-modifying treatment, while highlighting the ongoing need for robust evidence, equitable access and sustained investment in dementia care and research.