Every person is different and may react to TYSABRI differently. For some people, TYSABRI may cause side effects. Some may be more serious than others. It is important to talk with your healthcare team about potential side effects with TYSABRI.
One possible side effect of taking TYSABRI is progressive multifocal leukoencephalopathy (PML). PML is a rare brain infection that usually leads to death or severe disability. Currently, there is no known treatment, prevention, or cure for PML.
The risk of getting PML is tied to multiple factors, including having antibodies to the John Cunningham (JC) Virus. The JC Virus is common and harmless in most people—about 50%-60% of the general public has antibodies to the JC Virus in their blood—but can cause PML in people who have weakened immune systems, such as people taking TYSABRI.
Today, there are 6 years of available data to help determine your estimated risk of PML while taking TYSABRI. Your doctor can help you understand your risk and make the right treatment decision for you.
No one can predict who will get PML, but we can estimate the risk based on 3 known factors:
Your risk of getting PML is greatest if you have all 3 risk factors listed above. There may be other risk factors for getting PML that we do not know about yet.
Because TYSABRI may increase your risk of developing PML, you can receive TYSABRI only through a restricted distribution program called TOUCH® Prescribing Program. TOUCH ensures that you communicate closely with your healthcare team to monitor PML risk over time, so you can decide whether TYSABRI remains right for you. You can read more about the TOUCH program here.
Biogen offers a free blood test to check for antibodies to the JC Virus. Your healthcare team may order this test before you start receiving therapy and throughout the course of your treatment. A positive test result indicates a higher risk of developing PML, while a negative test result indicates a lower risk.
It is recommended that you get tested for JC Virus antibodies periodically. Like any virus, it is possible to come in contact with the JC Virus and have it enter your body after you’ve been tested. There is also a potential for a false-negative test result.* You are advised to be proactive and have the test from time to time, based on your healthcare team’s recommendation.
*There’s a possibility (2.2%) of a false-negative test result, which occurs when the blood test wrongly indicates that JC Virus antibodies are not present.
Herpes Encephalitis and Meningitis. TYSABRI may increase your risk of getting an infection of the brain or the covering of your brain and spinal cord (encephalitis or meningitis) caused by herpes viruses that may lead to death. Infection of the eye caused by herpes viruses leading to blindness in some patients has occurred. Call your doctor right away if you have sudden fever, severe headache, or if you feel confused after receiving TYSABRI.
Liver damage. Symptoms may include:
Call your doctor right away if you have symptoms of liver damage. Your doctor can do blood tests to check for liver damage.
Allergic reactions. TYSABRI may cause allergic reactions, including serious allergic reactions (e.g., anaphylaxis). Symptoms can include:
Serious allergic reactions usually happen within 2 hours of the start of the infusion, but they can happen at any time after receiving TYSABRI. Tell your doctor or nurse right away if you have any symptoms of an allergic reaction, even if it happens after you leave the infusion center. You may need treatment if you are having an allergic reaction.
Infections. TYSABRI may increase your chance of getting an unusual or serious infection because TYSABRI can weaken your immune system.
If you experience any side effect that bothers you or does not go away, tell your doctor. While you receive TYSABRI, and for 6 months after you stop receiving TYSABRI, it is important that you call your doctor right away if you have any new or worsening medical problems (such as problems with your thinking, eyesight, balance, or strength; weakness on 1 side of your body; and using your arms and legs) that have lasted several days.
For medical advice about side effects, call your doctor. To report side effects, call FDA at 1-800-FDA-1088.