News Brief: FDA Recommends Earlier MRI Monitoring for Alzheimer’s Patients Taking Lecanemab (LEQEMBI)

In August 2025 the Food and Drug Administration (FDA) recommended earlier magnetic resonance imaging (MRI) monitoring for patients with Alzheimer’s disease receiving lecanemab (LEQEMBI). The agency advised that an MRI be performed between the second and third infusions (between four and six weeks after treatment begins).[1] The purpose of the earlier monitoring is to identify people with amyloid-related imaging abnormalities with edema (ARIA-E), a condition involving brain swelling or fluid buildup.[2]

When ARIA-E is diagnosed, clinicians need to discuss with patients and caregivers whether lecanemab treatment should be delayed and discontinued. Although sometimes asymptomatic, ARIA-E can cause symptoms, including vision changes, headache, confusion, nausea, seizures and, in rare cases, death.

The FDA approved lecanemab in 2023 for Alzheimer’s disease patients with mild cognitive impairment or in the mild dementia stages. At best, the drug can modestly slow the progression of the disease; it does not reverse cognitive decline. The prescribing information for lecanemab includes a boxed warning (the strongest warning the FDA can require) about amyloid-related imaging abnormalities.

Public Citizen’s Health Research Group has designated lecanemab as a Do Not Use drug because its limited benefits do not outweigh its significant risks.[3] Nonetheless, clinicians are prescribing the drug, and some patients are taking it.

Initially approved in 2023 to slow the progression of Alzheimer’s disease in patients with mild cognitive impairment or dementia, lecanemab is an antibody infusion that removes beta-amyloid, a protein associated with Alzheimer’s disease, from the brain. The drug is administered intravenously every two weeks. In August 2025 the FDA approved a subcutaneous (under-the-skin) formulation, LEQEMBI IQLIK, as a maintenance treatment. The subcutaneous formulation is for patients who have completed at least 18 months of intravenous treatment.[4]

Previous prescribing information called for MRI scans before the fifth, seventh and 14th infusions. However, FDA post-market surveillance identified six fatal cases of ARIA-E early in treatment, before the fifth infusion.[5] A subsequent analysis of 101 serious ARIA-E cases found that 24% of patients developed symptomatic ARIA-E before the fourth infusion.[6] These findings prompted the agency to recommend additional and earlier MRI monitoring, and that this change should be reflected in the prescribing information.[7]
 

References

[1] Food and Drug Administration. FDA recommends additional earlier MRI monitoring for patients with Alzheimer’s disease taking Leqembi (lecanemab). August 28, 2025. https://www.fda.gov/drugs/drug-safety-and-availability/fda-recommend-additional-earlier-mri-monitoring-patients-alzheimers-disease-taking-leqembi-lecanemab. Accessed September 10, 2025.

[2] Ibid.

[3] Lecanemab for Alzheimer’s Disease: Do Not Use. Worst Pills, Best Pills News. October 2023. https://www.worstpills.org/newsletters/view/1556. Accessed September 10, 2025.

[4] Food and Drug Administration. FDA Drug Safety Communication: Leqembi (lecanemab). August 28, 2025. https://content.govdelivery.com/accounts/USFDA/bulletins/3f1d91a. Accessed September 10, 2025.

[5] Food and Drug Administration. FDA recommends additional earlier MRI monitoring for patients with Alzheimer’s disease taking Leqembi (lecanemab). August 28, 2025. https://www.fda.gov/drugs/drug-safety-and-availability/fda-recommend-additional-earlier-mri-monitoring-patients-alzheimers-disease-taking-leqembi-lecanemab. Accessed September 10, 2025.

[6] Ibid.

[7] Food and Drug Administration. Leqembi (lecanemab) prescribing information. August 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/761375s000lbl.pdf?utm_medium=email&utm_source=govdelivery. Accessed September 10, 2025.