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Generic name: natalizumab
Brand name: Tysabri
Dosage form: intravenous (infusion) injection
Drug class: Selective immunosuppressants

Medically reviewed by Philip Thornton, DipPharm. Last updated on Apr 4, 2023.

What is natalizumab?

Natalizumab a type of biological medication called a monoclonal antibody. It is used to treat a disease of the central nervous system called multiple sclerosis and an inflammatory bowel condition known asCrohn's disease.

Natalizumab is an immunosuppressant that works by attaching itself to the surface of leukocytes, which are white blood cells that circulate in your blood and help you when you get injured or are ill. White blood cells are part of the immune system and levels of them tend to be higher in people with conditions such as multiple sclerosis and Crohn's disease.

Natalizumab is an integrin receptor antagonist that specifically binds to integrins, a type of protein found on the surface of white blood cells. This prevents the white blood cells from migrating from the blood stream into areas of inflamed tissue.

It's not known exactly how this helps people with multiple sclerosis and Crohn's disease, but it is thought that by stopping the migration of the white blood cells, natalizumab helps to prevent nerve damage and inflammation.

Natalizumab was approved by the US Food and Drug Administration (FDA) in 2004. No biosimilars of it have been approved. Biosimilars are highly similar versions of the drug that are designed to have the same effect on a person, but a biosimilar is not identical to the original version.

What is natalizumab used for?

Natalizumab is a prescription medicine used to treat adults with:

Important information

Who should not receive natalizumab?

Do not receive natalizumab if you:

Talk to your doctor before receiving natalizumab if you have any of these conditions.

What should I tell my doctor before receiving natalizumab?

Before you receive natalizumab, tell your doctor if you:

How should I receive natalizumab?

natalizumab is given 1 time every 4 weeks through a needle placed in your vein (IV infusion).

Before each natalizumab dose you will be asked questions to make sure natalizumab is still right for you.

Dosing information

What are the side effects of natalizumab?

Natalizumab may cause serious side effects, including:

The most common side effects of natalizumab include:

Tell your doctor about any side effect that bothers you or that does not go away.

These are not all the possible side effects of natalizumab. Ask your doctor for more information.

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


Tell your doctor about all the medicines you take, including prescription and over-the-counter medicines, vitamins and herbal supplements.

Especially tell your doctor if you take medicines that can weaken your immune system, such as 6-mercaptopurine, azathioprine, cyclosporine, methotrexate, or TNF-alpha inhibitors and corticosteroids. Ask your doctor if you are not sure.

Know the medicines you take. Keep a list of them to show your doctor and pharmacist when you get a new medicine.

Pregnancy and breastfeeding

Tell your doctor if you are pregnant or plan to become pregnant. Natalizumab may cause low platelets, and in some cases also low red blood cells (anemia), in your newborn baby if you take natalizumab while you are pregnant. It is not known if natalizumab can cause birth defects.

Tell your doctor if you are breastfeeding or plan to breastfeed. Natalizumab can pass into your breast milk. It is not known if the natalizumab that passes into your breast milk can harm your baby. Talk to your doctor about the best way to feed your baby while you receive natalizumab.


What are the ingredients in natalizumab?

Active ingredient: natalizumab

Inactive Ingredients: sodium chloride, sodium phosphate, monobasic, monohydrate; sodium phosphate, dibasic, heptahydrate; polysorbate 80, and water for injection

Natalizumab is manufactured under the name Tysabri by Biogen Inc.; Cambridge, MA 02142 USA.

Popular FAQ

Yes, treatment with Tysabri can weaken your immune system. This may increase your risk of getting an unusual or serious infection. Tysabri increases the risk of progressive multifocal leukoencephalopathy (PML), a rare brain infection. If you have or have had PML, you cannot use Tysabri. Continue reading

You can take Tysabri for as long as you want providing you tolerate it well, have not developed any serious side effects, and Tysabri is still preventing relapses if you have multiple sclerosis (MS) or reducing symptoms, if you have Crohn’s disease. For people with MS, some response is noted at 12 weeks, but it may take up to 2 years for the full effects to be seen. People with Crohn’s disease should discontinue Tysabri if there is no benefit after 12 weeks Continue reading

Tysabri is not chemotherapy, it is a targeted treatment that works by blocking the migration of lymphocytes (a type of immune cell) from the lymph nodes, across the epithelium, and into inflamed tissue. It binds to a receptor that is present on all leukocytes apart from neutrophils and prevents them from binding to their counter receptors. It may also act in several other ways to prevent the further recruitment and inflammatory activity of activated immune cells. Tysabri belongs to the class of medicines known as integrin receptor antagonists. It may also be called a selective immunosuppressant or a monoclonal antibody. Continue reading

Cancer has not been reported as a side effect of Tysabri (natalizumab) in clinical studies. You should tell your doctor if you have cancer now or a history of cancer (for example, leukemia or lymphoma) before you start treatment with Tysabri. Continue reading

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Further information

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