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Pronunciation: leh-kem’-bee
Generic name: lecanemab-irmb
Dosage form: injection for intravenous use
Drug class: Miscellaneous central nervous system agents

Medically reviewed by Melisa Puckey, BPharm. Last updated on Aug 23, 2023.

What is Leqembi?

Leqembi (lecanemab-irmb) is used for Alzheimer’s disease to slow disease progression in patients who are at the stage of mild cognitive impairment or mild dementia, and also have a buildup of amyloid beta plaques in their brain. Leqembi works by reducing amyloid beta plaques in the brain and so slows the progression of Alzheimer’s disease. Leqembi helps control Alzheimer’s disease but does not cure it.

Leqembi (lecanemab-irmb) is from a class of medications called monoclonal antibodies.

Alzheimer’s disease is a type of dementia that affects memory, thinking, and behavior, which can eventually grow severe enough to interfere with daily tasks. One of the causes of Alzheimer’s disease is thought to be plaques of beta-amyloid that accumulate in the brain and damage nerve cells which results in the symptoms of Alzheimer’s. Leqembi reduces amyloid beta plaques, and so slows the decline of Alzheimer’s Disease.

Leqembi was originally FDA-approved on January 6, 2023, under the Accelerated Approval Pathway. On July 06, 2023, the FDA granted Leqembi traditional approval.

Who can use Leqembi?

Leqembi is FDA-approved to treat Alzheimer's disease in patients who have:

Leqembi side effects

Common Leqembi side effects include

Leqembi can cause serious side effects

Allergic reactions Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Amyloid Related Imaging Abnormalities or “ARIA” See Warnings below.

Infusion-related reactions may occur during the injection. Tell your medical caregiver  immediately if during your infusion you feel dizzy, nauseated, light-headed, itchy, sweaty, or have a headache, flu-like symptoms, fever, or vomiting; chest tightness, fast/slow heartbeats or pounding heartbeats, back pain, trouble breathing, or have swelling in your face.

This is not all the possible side effects. For more information, ask your healthcare provider or pharmacist, or click on the link below for more detailed information on side effects. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


Leqembi can cause serious side effects, including:

Amyloid Related Imaging Abnormalities or “ARIA”. Lecanemab can cause a condition called Amyloid Related Imaging Abnormalities or "ARIA" which is a temporary swelling or small spots of bleeding in the brain that usually clears up with time. Your doctor may perform an MRI of your brain before and during your treatment with lecanemab. Ask your doctor about your risk. If you have ARIA symptoms including confusion, difficulty walking, dizziness, headache, nausea, seizures, vision changes it is important to call your healthcare provider or go to the nearest hospital emergency room right away if you have any of the above symptoms.

Before receiving Leqembi

To make sure Leqembi is safe for you, tell your healthcare professional if you are allergic to any medicines, including lecanemab-irmb or the inactive ingredients contained in Leqembi.  Click here for a full list of Leqembi ingredients.


Tell your healthcare provider if you are pregnant, become pregnant or plan to become pregnant. It is not known if Leqembi will harm your unborn baby.


Tell your healthcare provider if you are breastfeeding or plan to breastfeed. It is not known if Leqembi, passes into your breast milk. Discuss with your healthcare provider the best way to feed your baby while receiving this medicine.

How will I receive Leqembi?

You will have your Leqembi treatment in a healthcare setting, it will be given to you by a doctor or nurse.

Dosing information

Usual Leqembi Adult Dose for Alzheimer’s Disease:

Leqembi is available as:

Monitoring for ARIA

Before starting treatment with this medicine, you should have a recent (within one year) brain magnetic resonance imaging (MRI), and another MRI should be done before the 5th, 7th, and 14th infusions.

What other drugs will affect Leqembi?

Tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.

It is important to tell your healthcare provider if you take medicines to reduce blood clots from forming (antithrombotic medicines, including aspirin). Ask your healthcare provider for a list of these medicines if you are not sure.

Know the name of the medicines you take and keep a list of them to show your healthcare provider and pharmacist when you get a new medicine.

To check for interactions with this medicine, click the link below.


Active ingredient: lecanemab-irmb.
Inactive ingredients: arginine hydrochloride, histidine, histidine hydrochloride monohydrate, polysorbate 80, and water for injection.


Unopened Vial

After dilution


Eisai Inc., Nutley, NJ 07110

Popular FAQ

Leqembi is manufactured by Eisai Inc. based in Nutley, NJ, USA. You can contact Eisai at 1-888-274-2378 or online at

Monoclonal antibodies (mAbs) are man-made proteins that mimic the natural antibodies produced by our immune systems. Monoclonal antibodies can be formulated into medicines to treat various types of illnesses, such as cancer, rheumatoid arthritis or psoriasis. Continue reading

Leqembi (lecanemab-irmb) is an anti-Aβ protofibril antibody and has been shown to reduce brain amyloid and modestly slow cognitive decline in adult patients with early Alzheimer disease. It is thought to slow down the progression of Alzheimer by neutralizing and eliminating the toxic amyloid-beta aggregates found in the brain. Continue reading

Yes, Leqembi received traditional (full) approval to treat early Alzheimer’s disease in patients with mild cognitive impairment or a mild dementia stage of disease on July 6, 2023. The FDA granted a traditional approval to Leqembi based on the Phase 3 CLARITY AD results and Advisory Committee unanimous recommendations. Continue reading

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.