FDA to Recommend Additional, Earlier MRI Monitoring for Patients with Alzheimer’s Disease Taking Leqembi (Lecanemab)

Why It Matters

Earlier MRI monitoring can reduce fatal ARIA‑E events, improving the safety profile of Leqembi and influencing its adoption in Alzheimer’s care.

Key Takeaways

• FDA adds MRI before third Leqembi infusion
• 101 serious ARIA‑E cases identified; six deaths
• Early detection may prevent fatal brain swelling
• Updated label mandates monitoring schedule change
• Clinicians must counsel patients on ARIA‑E symptoms

Pulse Analysis

Leqembi (lecanemab) entered the U.S. market in 2023 as the first disease‑modifying antibody approved for early Alzheimer’s. By targeting amyloid‑beta plaques, it promises to slow cognitive decline in patients with mild cognitive impairment or mild dementia, a segment that represents a multibillion‑dollar opportunity for biotech firms. However, the drug’s safety profile has been shadowed by amyloid‑related imaging abnormalities with edema (ARIA‑E), a brain‑swelling phenomenon that can be asymptomatic yet occasionally fatal. The FDA’s ongoing pharmacovigilance has therefore become a critical factor in how clinicians and payers evaluate Leqembi’s risk‑benefit balance.

In its August 2025 safety communication, the agency disclosed 101 serious ARIA‑E reports, including six deaths, with a notable cluster occurring before the fifth infusion. The analysis showed that 24 cases manifested prior to the fourth dose, two of them between the second and third infusion. Based on this distribution, the FDA now requires an additional MRI between the second and third administrations, expanding the existing schedule of scans before the fifth, seventh and fourteenth doses. For neurologists, this means an earlier imaging appointment, tighter coordination with infusion centers, and a new decision point for pausing or stopping therapy when edema is detected.

The earlier imaging mandate could reshape the commercial trajectory of Leqembi. Payers may view the added monitoring as a cost offset to mitigate catastrophic events, while providers will need to integrate MRI scheduling into treatment pathways, potentially influencing patient adherence. Moreover, the FDA’s proactive stance signals heightened regulatory scrutiny for emerging neuro‑degenerative therapies, prompting sponsors to embed robust safety monitoring into trial designs from the outset. As the Alzheimer’s market matures, transparent risk‑management strategies like this one will be pivotal in sustaining clinician confidence and ensuring that innovative antibodies reach patients safely.