Tysabri® (natalizumab)


Tysabri® (natalizumab) is a prescription medicine used to treat adults with relapsing forms of multiple sclerosis (MS) to slow the worsening of symptoms common in people with MS and to decrease the number of flare-ups (relapses).  Natalizumab was approved in 2004 by the U.S. Food and Drug Administration (FDA).

Tysabri is administered by intravenous infusion every 28 days. The drug is believed to work by reducing the ability of inflammatory immune cells to attach and pass through the cell layers lining the intestines and blood–brain barrier. Natalizumab has proven effective in treating the symptoms of both diseases, preventing relapse, vision loss, cognitive decline and significantly improving quality of life in people with multiple sclerosis.

TYSABRI is an infusion taken every 4 weeks (for a total of 2 hours), and can deliver results in many people with relapsing MS.


Tysabri is an intravenous infusion of 15ml of 300mg of natalizumab taken every 4 weeks (for a total of 2 hours), and can deliver results in many people with relapsing MS.

  • If you have a medical condition that can weaken your immune system, such as HIV infection or AIDS, leukemia or lymphoma, organ transplant, or others, or if you have any new or worsening medical problems that have lasted several days.
  • If you are pregnant or plan to become pregnant or if you are breastfeeding or plan to breastfeed. It is not known if Tysabri can harm your unborn baby or if the Tysabri that passes into your breast milk can harm your baby.
  • About all of the medicines and supplements you take, especially medicines that can weaken your immune system. If you are not sure, ask your doctor.

Efficacy Results:

  1. Reduces the number of flare-ups per year
    • More than 6 out of 10 people taking Tysabri had no flare-ups at all in a 2-year study
      • Out of 627 people taking Tysabri, 67% were flare-up free vs 41% of 315 people who were not taking treatment (placebo) at 2 years
  2. Slows physical disability progression
    • Tysabri slowed physical disability progression by nearly half vs people not taking treatment (placebo) in the 2-year study
      • People who were treated with Tysabriwere 42% less likely to develop worsening physical disability after 12 weeks than those not taking treatment (placebo)
    • More than 8 out of 10 people experienced no physical disability progression in the 2-year study
      • 29% of people who received no treatment (placebo) had their physical disability worsen, vs 17% of those who were treated with Tysabri
  3. Impacts the number of active brain lesions
    • More than 9 out of 10 people had no lesions that showed disease activity in the two-year study
      • 97% of people taking Tysabri had no brain lesions that showed disease activity on an MRI, compared with 72% of people not on treatment (placebo)

Side Effects:

Most people taking Tysabri tolerate it well, but there can be side effects – including a very rare, but potentially fatal infection called PML.

  • Common side effects include joint pain, fever, tiredness, a runny or blocked nose, sore throat, feeling or being sick, headache or dizziness.
  • Urinary tract infection, lung infection, pain in your arms and legs, vaginitis, stomach-area pain, feeling tired, joint pain, depression, diarrhea, rash, and nausea.
  •  During the infusion of Tysabri, and up to an hour afterwards, some people shiver, or feel sick or dizzy.
  •  Around one in 25 people who take Tysabri have a more serious allergic reaction to taking it, either during the infusion or in the hour following
  • In addition, people might have skin reactions to the infusion.

If you experience any side effect that bothers you or does not go away, tell your doctor.

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Important Safety Information

Tysabri increases your risk of getting a rare brain infection—called progressive multifocal leukoencephalopathy (PML)—that usually leads to death or severe disability.

  • There is no known treatment, prevention, or cure for PML.
  • You should not take certain medicines that weaken your immune system at the same time you are taking Tysabri. Even if you use  ysabri alone to treat your MS, you can still get PML.
  • Your risk of getting PML is higher if you:
    • have received Tysabri for a long time, especially for longer than 2 years
    • have received certain medicines that can weaken your immune system before you start receiving Tysabri
    • have been infected by the John Cunningham Virus (JCV). Before or while you receive Tysabri, your doctor may do a blood test to check if you have been infected by JCV. JCV is a common virus that can cause PML in people who have weakened immune systems, such as people taking Tysabri.
  • Your risk of getting PML is greatest if you have all 3 risk factors listed above. There may be other risk factors that have not yet been identified.
    • There have been over 100 cases of PML with Tysabri.
  • Patients who are anti–JCV antibody negative are still at the risk for the development of PML due to the potential for a new JCV infection or a false negative test result. Therefore, patients with a negative test result should be retested periodically.
  • 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. Tell all of your doctors that you are getting treatment with Tysabri.
  • Because of your risk of getting PML while you receive Tysabri, Tysabri is available only through a restricted distribution program called the TOUCH® Prescribing Program.
  • If you have PML or are allergic to Tysabri or any of its ingredients, you should not receive Tysabri.

Tysabri can cause serious side effects. If you have any of the symptoms listed below, call your doctor right away:

  • 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. Symptoms include sudden fever, severe headache, or confusion.
  • Liver damage. Symptoms of liver damage include yellowing of the skin and eyes (jaundice), unusual darkening of the urine, nausea, feeling tired or weak, or vomiting.
  • Allergic reactions (eg, hives, itching, trouble breathing, chest pain, dizziness, wheezing, chills, rash, nausea, flushing of skin, low blood pressure), including serious allergic reactions (eg, anaphylaxis). Serious allergic reactions usually happen within 2 hours of the start of the infusion, but they can happen any time after receiving TYSABRI.
  • Weakened immune system. TYSABRI may increase your risk of getting an unusual or serious infection.

Biogen LogoBiogen is one of the world’s leading biotechnology companies, with a focus on developing therapies for neurodegenerative, hematologic and autoimmune disorders. Founded in 1978, our work in biologics and small-molecule drug discovery has led to the world’s most extensive portfolio of multiple sclerosis therapies and innovative new treatments for hemophilia patients. Our experience, capabilities and passion for innovation have enabled us to build a pipeline and develop advanced research programs that include exploration of potential candidates for serious and difficult-to-treat neurodegenerative diseases and fibrotic and nonmalignant blood disorders.

We are committed to research that uncovers the underlying biology of complex diseases. Our focus is on illnesses with few, if any, treatment options. Biogen’s success will always be measured by the answer to a simple question: Have we truly made a difference in the lives of patients?


Tysabri Patient Guide: