Tysabri (natalizumab)

Reviewed by: HU Medical Review Board | Last Reviewed: April 2022 | Last updated: January 2023

Natalizumab is a medicine for adults with moderate or severe Crohn’s disease, one of the two main forms of inflammatory bowel disease (IBD). Natalizumab is sold in the United States under the brand name Tysabri®.1-3

Natalizumab is given by an injection into a vein (intravenous injection). It is usually recommended for adults who do not respond well enough or cannot take certain types of medicines for treating Crohn’s disease. These include aminosalicylates, antibiotics, immunosuppressants, and corticosteroids.1,3

Natalizumab is also an option for people who cannot take, or do not get benefits from, other types of biologic therapies called anti-tumor necrosis factor (anti-TNF) medicines. These include infliximab, adalimumab, and certolizumab pegol.1,3

What are the ingredients in natalizumab?

The active ingredient is natalizumab.3

How does natalizumab work?

Natalizumab is a type of biologic therapy called an integrin receptor antagonist. Integrin receptor antagonists contain special antibodies that are made in a lab to target cells involved in the process of inflammation.1,2

The antibodies in natalizumab target specific types of white blood cells that cause inflammation. The antibodies block a protein on the surface of the white blood cells. This prevents the cells from moving out of the blood vessels and into tissues. Preventing the white blood cells from moving into tissues helps stop the process that causes inflammation.1,2

People with Crohn’s disease and other forms of IBD have symptoms caused by too much inflammation in their digestive tracts. By blocking part of the process that causes inflammation in the body, natalizumab can help some people with moderate or severe Crohn’s disease. The drug may:1,2

  • Relieve symptoms
  • Help you enter remission more quickly
  • Help you stay in remission for a longer time

What are the possible side effects?

The most common side effects of natalizumab include:3

  • Headache
  • Upper respiratory tract infections
  • Nausea
  • Fatigue

Natalizumab has a boxed warning, the strictest warning from the US Food and Drug Administration (FDA). It has this warning because natalizumab increases the risk of a viral brain infection called progressive multifocal leukoencephalopathy (PML). PML is very serious and usually leads to death or severe disability.3

Other serious side effects may include:3

  • Herpes encephalitis and meningitis
  • Liver damage
  • Allergic reactions to the medicine
  • Weakened immune system, which may lead to infections
  • Low blood count (thrombocytopenia)

These are not all the possible side effects of natalizumab. Talk to your doctor about what to expect when taking natalizumab. Call your doctor if you have any changes that concern you when taking natalizumab.

Other things to know

Because of the risk of PML, natalizumab is available only through a restricted program called the TOUCH Prescribing Program. Your doctor will closely monitor you for any risk factors for the development of PML. They will stop use if any signs of PML arise.3

Natalizumab should not be used with immunosuppressant drugs or TNF inhibitor drugs when it is used for Crohn’s disease. Also, people with Crohn’s disease should stop taking the drug if it is not effective after 12 weeks of treatment.3

Do not take natalizumab if you are allergic to any of the drug’s ingredients.3

Natalizumab can harm an unborn baby. If you can become pregnant, you should use birth control during treatment and for some time after the last dose of natalizumab. You should also not breastfeed during treatment with natalizumab and for some time after the last dose. Talk to your doctor about your options for birth control and breastfeeding while taking natalizumab.3

Natalizumab lowers your body’s immune system response and ability to fight infections. This can be dangerous if your immune system is already affected. Tell your doctor if you have any of the following:3

  • Fever
  •  Infection
  • A medical condition that affects your immune system, such as HIV, AIDS, leukemia, or lymphoma
  • History of organ transplant

Before beginning treatment for IBD, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.

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