Natalizumab (Tysabri)

Natalizumab (Tysabri) is in a class of medications called alpha 4 integrin inhibitors. It is approved as a treatment for moderate-to-severe cases of of Crohn’s disease in people who have stopped responding to at least one of the anti-TNF medications (Cimzia, Humira, or Remicade). It is administered intravenously.

Tysabri can cause the activation of latent infection with the polyomavirus JC (often called JC virus). Activated JC virus in people with suppressed immune systems can result in a brain infection called progressive multifocal leukoencephalopathy (PML).

People need to be tested for antibodies against the JC virus before and during Tysabri treatment.

Natalizumab (Tysabri) was approved by the FDA as a treatment for Crohn’s disease in 2008. It was first approved in 2004 as a treatment for multiple sclerosis. The drug was taken off the market in 2005 following cases of progressive multifocal leukoencephalopathy (PML) but was reintroduced in 2006 with a mandatory surveillance program.
How does Tysbari work?
Natalizumab (Tysbari) is an artificial antibody that binds to the surface of white blood cells so they can not pass through tissue layers and help cause inflammation.

The cell surface receptor that Tysbari binds to is called alpha 4 integrin, so Tysbari is in a class of medications called integrin inhibitors

How is it administered?

Natalizumab (Tysabri) is administered intravenously every four weeks. The infusions are given in a doctor’s office or at an infusion clinic.

When will I feel better?

Some people experience relief of symptoms after their first infusion with natalizumab (Tysabri). But it may take up to three infusions (or about 12 weeks because the infusions are given every four weeks) to feel a benefit. If you haven’t responded after three infusions, your care team will probably suggest that treatment with Tysabri should stop.

Studies have shown that about half (48%) of people treated with Tysabri respond to the drug within 12 weeks after the initial treatment. After 15 months, the response rate increases to 60%.

Side effects

  • Progressive multifocal leukoencephalopathy (PML) is a rare but serious brain infection. PML is caused activation by the polyomavirus JC virus. Many people are infected with the JC virus, but it is harmless because it is dormant. Suppressing the immune system can “wake up” the virus, and an activated JC virus can cause PML. Other drugs suppress the immune, but natalizumab (Tysbari) does it in a way that can activate the JC virus and increase the risk of PML.To guard against PML, people are tested for antibodies against the JC virus before they are treated with Tysabri.
  • Infections (17% to 22% of patients). As with with all medications that suppress the immune system, there is an increased risk of infection during treatment with Tysabri. If you have symptoms of an infection (fever, chills, sore threat, aches and pains), contact your care team. Your infusion of Tysabri need to be rescheduled.
  • Liver abnormalities (rare). People being treated with Tysabri have liver function tests every couple of months just to be on safe side.
  • Nausea (17%)
  • Headache (32% to 38%)
  • Achy joints (arthralgia (8%)
  • Depression (up to 19%)

How long do I need to take natalizumab (Tysabri)

Tysabri is designed to be taken as maintenance treatment to treat and prevent flares of Crohn’s disease. But the longer you are on Tysabri, the greater the risk of developing progressive multifocal leukoencephalopathy (PML), a rare brain disorder caused by the activation of the polyomavirus JC virus in people with suppressed immune systems.

You and your care team will need to weigh the risks and benefits of long-term use of Tysabri.

Taking probiotics while Pregnant

Women planning to become pregnant should discuss their treatment options with their care team in clinic. It is generally advised that you continue with maintenance treatment throughout pregnancy. An uncontrolled flare can be harmful to the fetus and increase the risk of miscarriage.

Yet the safety data on the use of natalizumab (Tysabri) during pregnancy and breastfeeding is limited.

A Tysabri pregnancy registry has been established to monitor maternal-fetal outcomes of pregnant women taking the drug. Ask your care team about any news about the risk and benefits from Tysabri from this registry.