Risk of Brain Infection
The risk of developing a potentially fatal brain infection is higher than previously thought for patients taking the genetically engineered multiple sclerosis drug Tysabri (natalizumab), scientists reported this week.
Tysabri, made by Biogen, is prescribed for patients with relapsing multiple sclerosis, the most common form of the disease. The drug is administered intravenously every 28 days, Newsday reports. In multiple sclerosis, the immune system assaults the protective coating (myelin) surrounding nerve fibers, damaging them, and causing patients to suffer weakness and lose vital functions. Tysabri helps to ward off attacks.
A new medical investigation reports that in some patients Tysabri can cause a tenfold risk of developing antibodies to the John Cunningham (JC) virus. The virus can lead to a potentially fatal brain disorder known as progressive multifocal leukoencephalopathy, or PML. A German research team, reporting in the journal Neurology Neuroimmunology and Neuroinflammation said the PML risk is higher than previously thought, Newsday reports. The study, led by Dr. Heinz Wiendl (University of Münster, Germany), was published online on January 27, 2016.
Physicians and advocacy groups said Tysabri is a good treatment option despite the findings and they emphasized the importance of routine screening of patients taking 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,” according to Newsday. Dr. Coyle said if any of her patients develop elevated antibody levels, she would advise them about other medication choices. But for those who remain free of JC virus-related antibodies and are doing well on Tysabri, she will continue the drug.
Dr. Coyle said the JC virus is present in a vast swath of people worldwide. According to the new research, Tysabri aids the virus’s capacity to breach the blood-brain barrier and cause PML, according to Newsday. There is no cure for PML. Dr. Paul Wright, who chairs the departments of neurology at North Shore University Hospital in Manhasset and Long Island Jewish Medical Center in New Hyde Park, explains, “We all harbor this virus and we all have the propensity to have the virus.” When the immune system is compromised, the virus can come out and be manifested.
Many people who take Tysabri had not fared well on other therapies for multiple sclerosis, doctors said. Biogen, maker of Tysabri, has posted a warning on its website about the medication’s propensity to induce PML.
“This study emphasizes the need for vigilant monitoring of people with MS taking natalizumab, including regular antibody testing, MRI monitoring to improve detection of PML, and clinical monitoring for early signs suggesting the possibility of PML,” noted Dr. Bruce A. Cohen, a professor in neurology and clinical neurosciences at Northwestern University’s Feinberg School of Medicine, and Chair of the National MS Society’s National Medical Advisory Committee. Dr. Cohen said natalizumab is a very effective therapy for relapsing MS, and the decision to discontinue this therapy needs to balance the risk of PML against their risk of worsening MS, and the potential adverse effects and efficacy of alternate therapies.