Leqembi (lecanemab-irmb)

Reviewed by: HU Medical Review Board | Last reviewed: January 2024 | Last updated: February 2024

Leqembi™ (lecanemab-irmb) is a drug that can treat people in the early stages of Alzheimer's disease. This includes about 1.5 million of the 6 million people with Alzheimer's in the United States.1,2

Leqembi modestly slows cognitive decline (problems with thinking) when used early in Alzheimer's disease. It works by reducing amyloid-beta plaque, which is a feature of Alzheimer's. Serious side effects of Leqembi are possible. Talk to your doctor about whether Leqembi is right for you.3,4

What are the ingredients in Leqembi?

The active ingredient in Leqembi is lecanemab-irmb.1,4

How does Leqembi work?

Leqembi is a monoclonal antibody. Antibodies are proteins in our immune system. They target germs to help our immune system fight and destroy them. Antibodies used to treat diseases are made in a lab to target a certain protein. Monoclonal means all the antibodies are identical and target the same region of the protein of interest.4,5

Scientists designed Leqembi to target a protein called "amyloid beta." These proteins can clump together to form deposits or "plaques." Amyloid beta plaques in the brain are a feature of Alzheimer's disease. Many experts think amyloid beta plaques cause Alzheimer's to progress. But we do not yet know how plaques may lead to symptoms of Alzheimer's .2,6,7

Clinical trials tested Leqembi on people in the mild or early stages of Alzheimer's. For these people, Leqembi reduces amyloid beta plaques. It also modestly slowed down problems with thinking and carrying out daily activities. But we need more data to know how meaningful these changes are over a longer time. Ongoing clinical studies are trying to provide additional data about safety and effectiveness.3,4,8

What are the possible side effects?

The most common side effects of Leqembi include:3,4

  • Infusion-related reactions
  • Headache
  • Amyloid related imaging abnormalities (ARIA)

Leqembi and other antibodies that target amyloid beta can cause amyloid-related imaging abnormalities or "ARIA." These drugs can cause 2 types of ARIA:3,4

  1. ARIA with edema (ARIA-E): temporary brain swelling
  2. ARIA with microhemorrhages or hemosiderin deposition (ARIA-H): small areas of bleeding in the brain

ARIA usually does not cause noticeable symptoms. But some people experience:3,4,6

  • Headache
  • Confusion
  • Dizziness
  • Vision changes

ARIA may rarely cause life-threatening side effects, including seizures. Some people have a genetic factor that makes it more likely they will experience ARIA. Talk to your doctor about testing to see if you have this risk factor.4,6

Leqembi can cause infusion-related reactions. These are usually mild or moderate and happen with the first infusion. Symptoms of infusion-related reactions include:3,4

  • Fever
  • Flu-like symptoms (chills, aches, shakiness, joint pain)
  • Nausea and vomiting
  • Dizziness
  • Changes in your heart rate
  • Difficulty breathing

These are not all the possible side effects of Leqembi. Talk to your doctor about what to expect when taking Leqembi. You also should call your doctor if you have any changes that concern you when taking Leqembi.

Other things to know

Clinical trials showed benefits and safety only for certain people with Alzheimer's disease. Before taking Leqembi, you must be tested to show you may benefit. This includes visiting specialist doctors to show that you:2,4

Leqembi is given through an intravenous (into the vein) infusion every 2 weeks. Each infusion lasts about an hour. If you miss an infusion, you should receive your next dose as soon as possible. Your doctor will monitor you with certain tests during treatment. One of these tests is magnetic resonance imaging (MRI) of the brain to monitor for ARIA.4

Before starting Leqembi, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. Other drugs you take or medical conditions you have may make Leqembi less safe. This includes over-the-counter drugs. Tell your doctor about:4

  • Allergies
  • Prescription drugs you take, especially drugs to reduce blood clots
  • Pregnancy or plans to become pregnant

Leqembi costs about 26,500 dollars per year. This price is higher than experts recommended for it to be cost-effective. Many people with Alzheimer's will not be able to afford the drug on their own. So their access will depend on whether Medicare covers the drug. For now, Medicare has limited coverage for Leqembi. But Medicare may expand coverage if there is more evidence of Leqembi's benefits.2,9,10

For more information, read the full prescribing information of Leqembi.

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Treatment results and side effects can vary from person to person. This treatment information is not meant to replace professional medical advice. Talk to your doctor about what to expect before starting and while taking any treatment.