NASHVILLE, TENN. – Armed with new statistics, neurologist Joseph R. Berger, MD, has a message for colleagues about the widely feared risk of progressive multifocal leukoencephalopathy (PML) in multiple sclerosis: It’s not as inevitable as you might think.
“You can actually prevent this disease from occurring because we have risk-limiting strategies in many circumstances,” saidof the University of Pennsylvania, Philadelphia, in a presentation on PML at the annual meeting of the Consortium of Multiple Sclerosis Centers.
Unlike other conditions such as HIV, MS itself is not linked to a higher risk of PML, said Dr. Berger, a leading PML researcher. Instead, it’s the medications that spark the condition, he said, with at least three and possibly four drugs posing a risk to patients.
Natalizumab (Tysabri) is especially risky. “We know that the risk with natalizumab is incredibly high in the context of JC [John Cunningham] virus antibody positivity and prolonged therapy,” Dr. Berger said in an interview after his presentation.
Still, “you can safely give natalizumab for a short period of time when treating patients with aggressive MS,” he said. “I will frequently employ that strategy even in the context of JC virus antibody positivity.”
According to Dr. Berger, there’s no risk of PML when natalizumab is used for under 8 months ().
However, “if you leave people on the drug indefinitely, there is a substantial risk of developing PML,” he said. “Individuals who have been left on the drug for 2 years, who’ve seen prior immunosuppressant therapy, who are JC virus antibody positive – that group of individuals develops PML at rates of 1 in 50 to 1 in 100.”