Natalizumab linked to increased risk biomarkers for virus that can lead to potentially fatal condition.
A drug that treats multiple sclerosis (MS) may increase the risk of developing a virus that can cause a potentially fatal brain condition.
The drug natalizumab was associated with a 10 times greater chance of developing a risk biomarker for activity of a virus that can lead to progressive multifocal leukoencephalopathy (PML), a deadly brain infection that is fatal and damages the white matter in the brain
PML is caused by John Cunningham virus (JCV), which is common and can typically be controlled by the immune system.
In a study published in Neurology Neuroimmunology and Neuroinflammation, researchers evaluated 525 people in Germany over a 15-month period and 711 people in France over a 2-year period, all of whom had MS and were taking natalizumab. A blood test was used to monitor levels of anti-JCV antibodies.
Ten percent of patients in the German group and 9% of people in the French group converted from being anti-JCV negative to anti-JCV positive, which is higher than the rate of 1% per year for people with MS not treated with natalizumab and the rate among the general population.
Forty-three out of 339 people who were originally anti-JCV negative tested positive for JCV antibodies in the German group, while 41 of 243 people in the French group tested positive.
Patients who were anti-JCV positive at the start of the study had their levels rise over a period of time. Treatment with natalizumab was linked to a 13% annual increase in anti-JCV antibody levels in the blood.
Patients considered medium risk of PML in the German group increased by 7 patients, the high-risk group grew by 14 patients.
"Even though anti-JCV antibodies were present at a higher level, it does not necessarily mean that an individual will get PML," said Adil Javed, MD, PhD, a member of the American Academy of Neurology. "The risk of PML in JCV positive people being treated for multiple sclerosis with natalizumab without prior immunosuppressant therapy is 1 in 1000 people. The risk of a multiple sclerosis attack in untreated patients is 1 in every 2 people."
Researchers stress that although the study does not prove that natalizumab causes the virus to replicate at higher rates, it does show that there is an association.
"It is important that people with multiple sclerosis taking natalizumab speak with their doctor before making any changes to their treatment,” said study senior author Heinz Wiendl, MD. “Still, this study shows anti-JCV antibodies may serve as a useful biomarker. Natalizumab did appear to increase the levels of anti-JCV antibodies and this higher level may be associated with a higher risk of PML. The results of this study underscore the need for frequent monitoring of anti-JCV antibodies in people who are being treated with natalizumab for multiple sclerosis."