A newly published report indicates that patients taking the multiple sclerosis drug Tysabri have a higher risk of developing a potentially fatal brain infection than previously thought.
German and French researchers found that Tysabri (natalizumab), used to treat patients with relapsing multiple sclerosis, the most common form of the condition, can cause a tenfold risk of developing antibodies to the JC (John Cunningham) virus, Newsday reports. The JC virus can lead to a potentially fatal brain disorder known as progressive multifocal leukoencephalopathy (PML). The drug is linked to approximately 600 PML cases nationwide, with a 23 percent mortality rate.
The study, led by Dr. Heinz Wiendl (University of Münster, Germany), was published online on January 27 in Neurology: Neuroimmunology and Neuroinflammation.
In multiple sclerosis, the immune system assaults the protective coating surrounding nerve fibers, damaging them and causing the patient to lose vital functions and suffer weakness. Symptoms vary and can include dizziness and vertigo, vision problems, muscle spasms, and bladder and bowel problems. Tysabri, made by Biogen, is administered intravenously every 28 days to help ward off MS attacks.
Physicians and advocacy groups emphasize that Tysabri is a good option for many patients despite the findings and they say it may be necessary to increase the amount of routine screening of patients on the drug.
Dr. Patricia K. Coyle, vice chair of neurology at Stony Brook University Hospital and director of the hospital’s MS Comprehensive Care Center said, “Whenever you manipulate the immune system, then theoretically the person may be at risk for PML.” She said if any of her patients develop elevated antibody levels, she would consider other medications, Newsday reports. But for patients who helped by Tysabri and who remain free of the JC virus antibodies, Dr. Coyle would have them continue with Tysabri.
The authors of the new article say Tysabri helps the virus to breach the blood-brain barrier and cause PML. The symptoms of PML are diverse, depending on the location and amount of damage to the brain, and symptoms may evolve over the course of several weeks to months. The most prominent symptoms are clumsiness; progressive weakness; and visual, speech, and sometimes personality changes. The progression of these deficits leads to life-threatening disability and (frequently) death, according to the National Institute of Neurological Disorders and Stroke.
Many people taking Tysabri had not fared well with other therapies for multiple sclerosis, Newsday reports. Dr. Paul Wright, chair of the departments of neurology at North Shore University Hospital and Long Island Jewish Medical Center, said, “I don’t want people to say, ‘Well, that’s it. I am not taking the medication,’ because these are the people who need it most.”
The National Multiple Sclerosis Society, headquartered in Manhattan, said that Tysabri is one of several medications that help patients who have episodic attacks of multiple sclerosis. Arney Rosenblatt, spokeswoman for the society, said, “If you are taking this medication you need to be diligent about following the directions.”