Lecanemab Safety Analysis in Korean Patients: "Most Adverse Reactions Are Mild or Asymptomatic"

Research Team Led by Professor Sung-Hoon Kang at Korea University Guro Hospital
"Pre-Treatment Risk Assessment and Regular MRI Monitoring Are Important"

An analysis of the real-world clinical safety and early treatment patterns of lecanemab (product name: Leqembi) in Korean patients with Alzheimer’s disease showed that most adverse reactions were mild or asymptomatic.

On September 21, Korea University Guro Hospital announced that a research team led by Professor Sung-Hoon Kang from the Department of Neurology had analyzed infusion-related reactions, amyloid-related imaging abnormalities (ARIA), ARIA risk factors, and early changes in cognitive function in 127 Korean patients who began lecanemab treatment at the Alzheimer's Disease Prevention Center of Korea University Guro Hospital between December 2024 and October 2025. The findings indicate that most adverse events were mild or had no symptoms.

From left, Professor Sung-Hoon Kang, Department of Neurology, Guro Hospital, Korea University; Resident Jae-Min Shin; Professor Sang-Il Seo, Department of Radiology; Professor Jae-Sun Uh, Department of Nuclear Medicine. Korea University Guro Hospital

This research was based on the K-LEARN study cohort, which tracks clinical outcomes, blood biomarkers, MRI, amyloid PET, and changes in cognitive function among lecanemab-treated patients.

Infusion-related reactions occurred in 21.3% of all patients, with fever, generalized weakness, and headache mostly appearing during or immediately after the first administration. Among 102 patients who underwent follow-up magnetic resonance imaging (MRI) after treatment, ARIA was detected in 8.8%, but most cases were mild on imaging or had no clinical symptoms.

Mini-Mental State Examination (MMSE) scores remained generally stable up to six months after treatment initiation. Patients with a higher number of cerebral microbleeds or severe white matter changes before treatment showed an increased risk of ARIA, indicating the need for risk assessment and regular MRI monitoring before and during treatment.

After publishing the findings, the research team expanded follow-up observations to 233 patients in actual clinical practice who received lecanemab. In this cohort, infusion-related reactions were observed in 25.3%, ARIA-E (cerebral edema or effusion) in 4.0%, and ARIA-H (cerebral microbleeds, etc.) in 8.5%. Compared to the initial analysis, no new safety signals were identified, and most adverse reactions remained mild or asymptomatic and manageable.

Professor Kang said, “This study is significant as it systematically analyzes the clinical course and safety of lecanemab in patients treated within the real-world clinical environment in Korea. If risk evaluation using brain MRI is performed before treatment and regular MRI monitoring is continued during treatment, safer application of the therapy can be expected.”

This research was based on the K-LEARN study cohort, which tracks clinical outcomes, blood biomarkers, MRI, amyloid PET, and cognitive function changes in lecanemab-treated patients. The research results were recently published in the international journal ‘Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring.’

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