• 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.

Is Tysabri an immunosuppressant?

Tysabri (natalizumab) is in a class of medications called immunomodulators and is an immunosuppressant. It is thought to work by stopping certain cells of the immune system from causing damage and inflammation to the body.

Due to its ability to suppress the immune system, Tysabri can increase your chances of getting a rare brain infection called progressive multifocal leukoencephalopathy (PML). PML often leads to death or severe disability and usually happens in people with a weakened immune system.

If you have or have had PML, you cannot use Tysabri.

What increases my risk of PML?

You have a higher risk of getting PML if:

• you have a weakened immune system and have been infected by the John Cunningham Virus (JCV+). Your doctor may check you for JCV virus before you start Tysabri treatment and may retest you periodically.
• you have taken Tysabri for a long time, especially over 2 years.
• you have received medicines that weaken your immune system (immunosuppressants) before you start treatment with Tysabri.

Your risk of getting PML is greatest if you have all 3 of the risk factors listed above.

There is no way to treat, prevent, or cure PML at this time. Your doctor will continue to monitor you for any new signs or symptoms of PML for at least 6 months after you stop taking Tysabri.

Each time you visit your doctor and pharmacist, take a list of the medicines you take. This includes prescription and over-the-counter medicines, vitamins and herbal supplements.

Especially tell your doctor if you take medicines that can weaken your immune system. You should not take certain medicines that weaken your immune system at the same time you are taking Tysabri. Ask your doctor if you are not sure if you medicine will weaken your immune system.

Tell your doctor if you have any medical conditions that may weaken your immune system such as:

• HIV infection or AIDS
• leukemia or lymphoma
• an organ transplant
• other medical conditions that can weaken your immune system

Tell your doctor if you have any new or worsening medical problems that have lasted several days.

Tell your doctor before you start treatment with Tysabri if you have cancer now or a history of cancer (for example, leukemia or lymphoma). Cancer and cancer treatments can weaken your immune system, which can make treatment with Tysabri dangerous.

Before using this medicine, you should talk to your doctor so you can understand the risks and benefits of Tysabri. You and your doctor will need to enroll in a special prescribing program called the TOUCH Prescribing Program. This allows you to have access to this medicine and to help manage your safety. Your doctor can explain this program to you and the requirements.

What is Tysabri approved to treat?

Tysabri is a prescription medicine approved by the FDA to treat adults with relapsing forms of multiple sclerosis (including clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease) or moderate-to-severe Crohn’s disease.

Learn more: Side effects with Tysabri (in more detail)

This is not all the information you need to know about Tysabri (natalizumab) for safe and effective use and does not take the place of talking to your doctor about your treatment. Review the full Tysabri information here, and discuss this information and any questions you have with your doctor or other health care provider.