'Despite side effects, Leqembi offers more benefits than risks for dementia patients’

Leqembi (lecanemab), developed for Alzheimer's disease, the most common form of dementia, is often hailed as a “dream treatment” for dementia.

Leqembi works by removing amyloid proteins, which accumulate in the brain and are believed to directly cause Alzheimer's disease, making it more effective than any other dementia-related medication developed to date.

However, behind Leqembi's remarkable efficacy lie various side effects.

The most serious side effect is ARIA (Amyloid-Related Imaging Abnormalities), which can cause abnormal brain imaging findings such as swelling or bleeding. As the name suggests, these side effects occur when amyloid proteins are removed, leading to abnormal brain imaging findings, such as brain swelling and bleeding.

“When Leqembi is administered, the removal of amyloid proteins may cause abnormal reactions on imaging,” said Professor Lee Sun-min of the Department of Neurology at Ajou University Hospital on the Ajou University Hospital TV. “These primarily manifest as brain swelling and bleeding. If symptoms occur due to ARIA, the most common ones include headaches, dizziness, sudden changes in vision that have never been experienced before, such as sudden loss of vision or confusion, which may persist. In severe cases, symptoms similar to a stroke or seizures may occur.”

If ARIA symptoms are severe, Leqembi administration may need to be discontinued. “If ARIA defined as moderate is observed on MRI, Leqembi treatment may need to be discontinued according to the criteria," Professor Lee said.

So, why does ARIA occur when Leqembi is administered?

"ARIA occurs during the process of removing amyloid proteins,” Lee explained. “It's like a very sticky tape that has been stuck to a desk surface for a long time. If you decide to remove it one day, it's not easy to peel it off all at once. It is known that amyloid proteins begin accumulating as early as 15 years before symptoms appear, and in some cases up to 30 years before. Therefore, ARIA may manifest as a therapeutic response during the process of removing amyloid that has been accumulated over a long period of time."

However, there is no need to be overly concerned about ARIA side effects when considering Leqembi administration.

“The actual experiences of doctors abroad who have used the medication indicate that these side effects are not as severe as expected,” Professor Lee noted. “While we do not downplay or overlook these side effects, if they reach a level that could offset the clinical benefits patients can gain from the medication, the treatment still holds significant meaning. When weighing the benefits and drawbacks for patients, the benefits far outweigh the risks, making Leqembi a meaningful treatment option.”

There are other potential side effects of Leqembi besides ARIA.

"When Leqembi is administered intravenously, injection-related reactions, such as fever, chills, nausea, and palpitations, may occur,” Lee noted. “Additionally, all protein-based medications require caution regarding allergic reactions. Rash or hives may occur, and allergic reactions, including swelling of the lips, tongue, or face, may occur. In rare cases, severe allergic reactions, including anaphylaxis, a type of shock reaction, have been reported."