The U.S. Food and Drug Administration announced Thursday it is requiring additional brain monitoring for Alzheimer's patients receiving Leqembi after identifying six deaths early in treatment that prompted an in-depth safety analysis of the groundbreaking therapy.
The FDA is mandating earlier MRI scans between the second and third infusions to detect amyloid-related imaging abnormalities with edema (ARIA-E), a serious side effect characterized by brain swelling or fluid buildup. This represents a significant change from current prescribing information, which recommends MRI imaging before the fifth, seventh and 14th infusions.
Safety Concerns Drive Enhanced Monitoring
The regulatory action follows the FDA's analysis of serious and fatal outcomes related to ARIA-E occurring before the fifth Leqembi infusion. The six deaths identified early in treatment highlighted the need for more vigilant monitoring to identify at-risk patients before complications develop.
"The earlier monitoring can identify individuals with amyloid-related imaging abnormalities with edema (ARIA-E), which is characterized by brain swelling or fluid buildup," the FDA stated in its announcement.
The enhanced monitoring protocol brings Leqembi closer to the requirements for Eli Lilly's competing Alzheimer's drug Kisunla, which requires brain MRI scans prior to the second, third, fourth and seventh infusions.
Clinical Impact and Therapeutic Promise
Leqembi, developed jointly by Eisai and Biogen, received FDA approval in 2023 as the first therapy targeting an underlying cause of Alzheimer's disease. The anti-amyloid beta monoclonal antibody has demonstrated significant clinical benefits, showing a 31% reduction in clinical decline compared to placebo over 18 months in clinical trials.
The drug is approved for patients with mild cognitive impairment or mild dementia stage of Alzheimer's disease and works by targeting amyloid beta plaques, a hallmark of the neurodegenerative condition. Currently administered by intravenous infusion, an injectable version is under U.S. regulatory review.
Expanding Global Reach Despite Safety Considerations
Despite the safety concerns, Leqembi continues its global expansion. The drug received European Commission approval in April 2025 and has launched in Austria and Germany as of August 2025, marking significant milestones for Alzheimer's treatment in Europe.
The FDA's recommendation underscores the complex balance between providing access to breakthrough therapies and ensuring patient safety. As Biogen, a leading manufacturer of therapeutic products with significant revenue from medicine sales and royalties, continues to expand Leqembi's availability, the enhanced monitoring requirements will be crucial for maintaining the drug's safety profile while preserving its therapeutic benefits for Alzheimer's patients.
