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Tysabri (natalizumab) is a Multiple Sclerosis (MS) drug that has been linked PML, a rare but serious type of brain infection that can cause permanent disability or death. Drug-makers are now facing at least six Tysabri lawsuits from patients who allege that they were never warned that the risk of PML increases with longer Tysabri use.

FDA Safety Warnings for Tysabri and PML

Tysabri was approved by the U.S. Food and Drug Administration (FDA) in 2006 for the treatment of Multiple Sclerosis (MS). On January 20, 2012, the FDA issued this Tysabri Safety Communication to inform the public that Tysabri patients who are infected with the JC virus have a higher risk of PML, and they should undergo a blood test to check for anti-JC virus antibodies.

Older FDA Safety Warnings for Tysabri and PML:

  • February 5, 2010 — Tysabri PML Warning — 31 confirmed cases of PML in Tysabri patients.
  • April 22, 2011 — Tysabri PML Warning — FDA warns that the risk of PML increases with longer Tysabri treatment.

What is Progressive Multifocal Leukoencephalopathy (PML)?

Progressive Multifocal Leukoencephalopathy (PML) is an infection of the white matter in the brain that usually causes severe, life-threatening disability or death. It is caused by the JC virus, which damages myelin (the protective insulation around nerve cells). PML has a 50-60% mortality rate in the first few months after diagnosis, and there is no known cure.

Tysabri PML Risk-Factors

Tysabri patients who have all of the following risk-factors have an 11 in 1,000 risk of developing PML:

  • Treatment with Tysabri for more than two years.
  • Past or current treatment with immunosuppressive drugs (e.g., mitoxantrone, azathioprine, methotrexate, cyclophosphamide, or mycophenolate mofetil), which are often prescribed to people with cancer, organ transplants, HIV/AIDS, etc.
  • The presence of anti-JC virus antibodies, which can be detected in a blood test.

Symptoms of PML

The symptoms of PML vary depending on the part of the brain that is infected with the virus. Symptoms may also change over the course of several weeks or months. When symptoms appear, they typically worsen over time, and may include:

  • Clumsiness
  • Progressive weakness
  • Vision problems or blindness
  • Speech impairment
  • Personality changes
  • Disability
  • Death

Additional Information & Resources

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