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Overview: Leqembi is used to treat early Alzheimer's disease in certain people. It works by helping remove amyloid plaques, which are abnormal deposits in the brain that are linked to Alzheimer's disease. Common side effects include infusion-related reactions, headache, and changes seen on brain scans. It can sometimes cause brain swelling or bleeding, which can be serious, so contact your health care provider right away if you have unusual symptoms such as severe headache, confusion, vision changes, dizziness, or seizures. Leqembi is given as an intravenous (IV) infusion or an injection under the skin.

Uses

What is Leqembi used for?

Leqembi (lecanemab-irmb) is commonly used to treat Alzheimer’s disease. Leqembi doesn’t cure Alzheimer’s disease, but it may help slow declines in memory and thinking.

Leqembi may also be used for other conditions as determined by your health care provider.

How does Leqembi work (mechanism of action)?

In people with Alzheimer's disease, a protein called amyloid beta builds up in the brain. These proteins form clumps known as plaques that cause memory and thinking problems. Leqembi is a medicine that targets and helps remove these amyloid beta plaques.

Learn more about How Leqembi Helps with Early Alzheimer's and What to Expect.

How is Leqembi supplied (dosage forms)?

Brands and other names

  • Leqembi
  • Leqembi Iqlik

Leqembi is given as an intravenous (IV infusion) by a health care provider for the first 18 months of therapy. After 18 months, you can continue IV infusions or switch to at home use of subcutaneous (under the skin) injections with Leqembi Iqlik autoinjector. The subcutaneous injection is available as 360 mg/1.8 mL (200 mg/mL) in a single-dose prefilled autoinjector. 

How should I store Leqembi?

Leqembi Iqlik should be stored in a refrigerator between 36 F and 46 F (2 C and 8 C). Keep in the original container protected from light. Do not freeze. You may store the autoinjector at room temperature up to 77 F (25 C) for up to 14 days. Do not return the autoinjector to the refrigerator after it has been stored at room temperature.

Side Effects

What are the most common side effects of Leqembi?

The most common side effects of Leqembi are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Infusion or injection-related reactions (see below)
  • Amyloid Related Imaging Abnormalities (ARIA) (see below)
  • Headache

There may be other side effects of Leqembi that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of Leqembi?

While less common, the most serious side effects of Leqembi are described below, along with what to do if they happen.

Severe Allergic Reactions. Leqembi may cause allergic reactions, which can be serious. Tell your health care provider right away or get emergency help if you have any of the following symptoms of a serious allergic reaction. Get emergency help if you are no longer where you received Leqembi.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Amyloid-Related Imaging Abnormalities (ARIA). Leqembi may cause a potentially serious side effect called amyloid-related imaging abnormalities (ARIA). Most people with ARIA don’t have any symptoms, but it involves abnormal changes seen on brain scans. If people do have symptoms of ARIA, they are often mild and go away on their own. However, sometimes ARIA can be serious or life-threatening. Stop using Leqembi and get help right away if you have any of the following symptoms of ARIA.

  • Headache
  • Nausea
  • Confusion
  • Trouble walking
  • Dizziness
  • Seizures
  • Vision changes

Infusion or Injection Reactions. Leqembi can cause reactions that can be serious. Tell your health care provider right away if you have any of the following symptoms when you get your injection.

  • Fever
  • Dizziness, lightheadedness, headache, or fatigue
  • Flu-like symptoms, like chills, body aches, feeling shaky, and joint pain
  • Changes in your heart rate, such as a fast, slow, or pounding heartbeat
  • Nausea or vomiting
  • Trouble breathing or shortness of breath
  • Redness, swelling, heat, pain, itching, rash, bruising and blood collection under the skin at the injection site

Warnings & Precautions

Who should not use Leqembi?

Allergies to Ingredients. People who are allergic to any of the following should not use Leqembi.

  • Leqembi
  • Lecanemab-irmb
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in Leqembi.

What should I know about Leqembi before using it?

Do not use Leqembi unless it has been prescribed to you by a health care provider. Use it as prescribed.

When given by a health care provider as an intravenous infusion, each infusion of Leqembi will last about 1 hour. 

After 18 months, you may switch to the subcutaneous form, Leqembi Iqlik. A health care provider will teach you or a caregiver how to use the Leqembi Iqlik autoinjector at home. The injection is given under your skin (subcutaneous), into the front of your thighs, stomach area, or the back of your upper arm. Rotate injection sites with each dose. Do not inject into moles, scars, bruises, tattoos, or into areas of red, hard, tender, or injured skin.

If you will store Leqembi at home, do not share it with other people, even if they have the same condition as you. It may harm them. Keep Leqembi out of the reach of children. Since this medicine should be kept in a refrigerator, take special precautions to keep it away from children who also use the refrigerator.

Some people have a genetic risk factor called homozygous apolipoprotein E gene carriers. This genetic risk factor may increase the risk of a serious possible side effect called amyloid-related imaging abnormalities (ARIA). Your health care provider may do genetic testing to see if you have this risk factor before prescribing Leqembi.

What should I tell my health care provider before using Leqembi?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if Leqembi is right for you.

In particular, make sure that you discuss any of the following.

Other Medicines and Supplements. Leqembi may interact with other medicines and supplements. Before using Leqembi, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how Leqembi could affect pregnancy or harm a fetus. Tell your health care provider if you are or plan to become pregnant.

Breastfeeding. It is not known if Leqembi passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does Leqembi interact with foods or drinks?

There are no known interactions between Leqembi and foods or drinks.

It is unknown if drinking alcohol will affect Leqembi.

Does Leqembi interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. In particular, make sure that you tell your health care provider if you take medicines to treat or prevent blood clots, such as aspirin, warfarin (Coumadin, Jantoven), or apixaban (Eliquis).

This may not be a complete list of medicines that can interact with Leqembi. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much Leqembi?

If you or someone else has used too much Leqembi, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of Leqembi?

If you miss an appointment to get your Leqembi intravenous infusion dose, call to make another appointment as soon as possible. If you miss a dose of Leqembi Iqlik, inject the missed dose as soon as possible up to 6 days after the missed dose. Take your next injection on your regular dosing schedule.