Reviewed by: HU Medical Review Board | Last reviewed: April 2023
Tysabri® (natalizumab) is an injectable prescription drug approved to treat adults with relapsing forms of multiple sclerosis (MS). Tysabri is a disease-modifying treatment (DMT), which can slow the progression of MS and reduce the number of relapses or flares.1
Tysabri increases the risk of developing a rare brain infection known as progressive multifocal leukoencephalopathy (PML). PML is a viral infection of the brain that has no known treatment, prevention, or cure. PML can lead to severe disability or death. Because of the risk of PML, Tysabri is only used in people that have not been helped enough by or cannot tolerate another treatment for MS.1
Because of the risk of PML, Tysabri is only available through a special program called the TOUCH® Prescribing Program. Only doctors, infusion centers, and infusion center pharmacies registered with the program can prescribe, distribute, or infuse Tysabri. In order to receive Tysabri, you must talk to your doctor and understand the benefits and risks of the drug, and agree to all of the instructions in the TOUCH Prescribing Program.1
What are the ingredients in Tysabri?
The active ingredient in Tysabri is natalizumab.1
How does Tysabri work?
The exact way Tysabri works is not fully understood. Researchers think it binds to a specific receptor on the surface of certain white blood cells. Blocking this receptor may stop them from crossing into the central nervous system (brain, spinal cord and optic nerve) and reduce the inflammation in the brain that is overactive in MS.1
What are the possible side effects of Tysabri?
The most common side effects of Tysabri include:1
- Joint pain
- Urinary tract infection
- Lower respiratory tract infection
- Stomach pain or nausea
- Vaginal infection
- Pain in the arms or legs
- Abdominal pain or discomfort
Tysabri may cause other serious side effects, including:1
- Increased risk of herpes infections, which may cause blindness, brain or spinal cord infection, and may lead to death
- Liver damage, which may appear as yellowing of the skin or eyes, darkening of the urine, nausea, fatigue, vomiting, and may lead to liver failure requiring a liver transplant
- Serious allergic reactions, which can cause hives, itching, or difficulty breathing
- Weakened immune system, which could increase the risk of getting infections
- Thrombocytopenia, or low levels of platelets in the blood
Tysabri has a boxed warning, the strictest warning from the U.S. Food and Drug Administration (FDA). It has this warning because it increases the risk of developing the rare brain infection PML. PML is a viral infection that can lead to significant disability or death. The risk of PML is increased with:1
- Long-term use of Tysabri, especially longer than 2 years
- Prior use of drugs that suppress the immune system (immunosuppressants)
- Previous infection of the John Cunningham virus (human polyomavirus 2)
While taking Tysabri and for 6 months after treatment, people who experience any of the following symptoms should report them to their doctor right away:1
- Any new or worsening medical problems such as difficulty with thinking, eyesight, balance, or strength
- Weakness on one side of the body
- Difficulty using arms or legs
These are not all the possible side effects of Tysabri. Talk to your doctor about what to expect when taking Tysabri. You also should call your doctor if you have any changes that concern you when taking Tysabri.
Other things to know about Tysabri
You should not take Tysabri if you:1
- Have PML
- Are allergic to Tysabri
- Have a medical condition that can weaken your immune system, such as HIV, AIDS, leukemia, lymphoma, or an organ transplant
- Are taking medicines that can weaken your immune system
Before receiving an infusion of Tysabri, tell your doctor if you:1
- Have any new or worsening medical problems that have lasted several days, such as changes in your eyesight, balance, thinking, or strength
- Have had hives, itching, or trouble breathing during or after an infusion of Tysabri
- Have a fever or infection
Tysabri can harm an unborn baby. It can also pass into breastmilk. Talk to your doctor about your options for birth control and breastfeeding while taking Tysabri.1
Before beginning treatment for MS, 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 Tysabri.