Tysabri (natalizumab) is a brand-name IV infusion prescribed for certain forms of multiple sclerosis, clinically isolated syndrome, and Crohn’s disease. Tysabri works to treat these conditions by binding to certain cells in your immune system.

Tysabri is a biologic drug that belongs to the drug class called integrin receptor antagonists. It’s approved to treat certain forms of multiple sclerosis (MS), clinically isolated syndrome (CIS), and Crohn’s disease.

MS and CIS

MS is a condition in which your immune system (your body’s defense against disease) attacks your central nervous system (CNS). (Your brain and spinal cord make up your CNS.)

With MS, your immune system destroys myelin, which is the covering that protects nerve fibers. Without this covering, your brain has difficulty sending messages to the rest of your body through your nerves. This can lead to permanent nerve damage and difficulty moving.

CIS is an episode of one or more symptoms similar to those caused by MS. This condition can be the first sign of MS.

How Tysabri treats MS and CIS

It’s not fully known how Tysabri works, but it’s thought that it works by binding (attaching) to the cells in your immune system that attack your CNS. The drug helps prevent the cells from moving to your brain and spinal cord, where they can cause nerve damage.

Crohn’s disease

Crohn’s disease is a kind of inflammatory bowel disease that causes inflammation (swelling) in your digestive tract. Cells in your immune system that usually fight disease mistakenly attack your digestive tract. This causes inflammation.

How Tysabri treats Crohn’s disease

It’s not fully known how Tysabri works, but it’s thought that it works by binding to these cells in your immune system. This helps prevent the cells from moving to your digestive tract, where they can cause inflammation.

For multiple sclerosis (MS) and clinically isolated syndrome, it’s hard to say how quickly Tysabri starts to work. This is because the drug is meant to help prevent relapses (flare-ups) and prevent MS from worsening.

For Crohn’s disease, you can expect to feel your symptoms ease within the first 8 weeks of taking Tysabri. In a clinical trial, after 8 weeks of treatment, Crohn’s disease symptoms eased significantly in more than half of the people who took Tysabri. And nearly a third of people who took the drug were in remission (free from symptoms).

If you’d like to learn more about Tysabri, talk with your doctor or pharmacist. They can help answer any questions you have about how the drug works in your body.

If you’d like to learn about other aspects of Tysabri, you can explore these articles:

  • More information about Tysabri. For details about other aspects of Tysabri, refer to this article.
  • Side effects. To learn about side effects of Tysabri, see this article. You can also look at the Tysabri prescribing information.
  • Cost. If you’d like to learn about Tysabri and cost, see this article.
  • Drug comparison. To learn how Tysabri compares with Kesimpta, read this article.
  • Dosage. For information about the dosage of Tysabri, view this article.
  • A look at multiple sclerosis. For details about multiple sclerosis, see our multiple sclerosis hub.

Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.