Published on: May 12, 2025
The FDA’s 2023 approval of lecanemab — a novel Alzheimer’s treatment shown in clinical trials to modestly slow disease progression — was met with optimism, as it marked the first therapy of its kind to directly impact the disease. However, concerns about side effects such as brain swelling and bleeding observed during trials have made some patients and physicians hesitant.
Medications often behave differently when used in broader, real-world populations. To better understand lecanemab’s safety outside of clinical trials, researchers at Washington University School of Medicine in St. Louis conducted a study on patients receiving the drug at their Memory Diagnostic Center. They found that serious adverse events were rare and generally manageable.
In alignment with earlier clinical trial findings, only 1% of patients in the study experienced severe side effects that required hospitalization. Those in the very early stages of Alzheimer’s, with only mild symptoms, had the lowest risk of complications — an important insight for patients and clinicians considering the therapy.
Published May 12 in JAMA Neurology, the retrospective study examined data from 234 patients with very mild or mild Alzheimer’s who received lecanemab infusions at WashU’s Memory Diagnostic Center, which specializes in dementia care.
This new class of Alzheimer’s drugs is the only approved treatment that slows disease progression, said Barbara Joy Snider, MD, PhD, professor of neurology and co-senior author of the study. Concerns over side effects can lead to treatment delays. But our findings show that with the right clinical infrastructure and expertise — like we have at WashU — lecanemab can be administered safely, even for those who experience more serious side effects.
Lecanemab is a monoclonal antibody that targets and clears amyloid plaques, potentially extending a patient’s ability to live independently by about 10 months, according to a recent WashU-led study. Since amyloid buildup is an early step in Alzheimer’s, the drug is recommended for those with very mild or mild symptoms. The researchers reported that only 1.8% of patients with very mild symptoms developed any adverse effects, compared to 27% of those with mild Alzheimer’s.
Patients in the earliest stages of Alzheimer’s tend to gain the most benefit and face the lowest risk from treatment, said Snider, who also led clinical trials of lecanemab at WashU. “Delaying treatment can actually increase the likelihood of side effects. We hope our results help patients and physicians have better-informed conversations about the risks and benefits.
One of the key concerns with lecanemab is amyloid-related imaging abnormalities (ARIA), which are brain changes visible on scans and may indicate swelling or bleeding. In earlier trials, 12.6% of participants developed ARIA, though most cases were symptomless and resolved without treatment. About 2.8% experienced symptoms like headaches, nausea, dizziness, or confusion. Fatal complications were extremely rare, affecting about 0.2% of treated patients.
WashU’s Memory Diagnostic Center began administering lecanemab in 2023 following its full FDA approval. Patients receive biweekly infusions, and their care includes regular, advanced brain imaging to monitor for signs of ARIA. Treatment is stopped in patients who show symptoms or significant signs of ARIA, and severe cases are treated with steroids in a hospital setting.
In reviewing patient outcomes, researchers found that the occurrence and severity of side effects closely mirrored those seen in trials. Most ARIA cases were asymptomatic and identified only through routine brain scans. Among the 11 patients who did show symptoms, most recovered within a few months, and no deaths were reported.
Overall, most patients tolerate lecanemab well, said Suzanne Schindler, MD, PhD, associate professor of neurology and co-senior author of the study. These findings can help patients and healthcare providers better understand the risks — which are especially low for those with very mild Alzheimer’s symptoms.
Back to News
Empowering Innovation Through Global Conferences and Events.
© 2025 SciInov. All Rights Reserved.