Disease Activity Increases After MS Patients Stop Natalizumab (Tysabri) Treatment
ST. PAUL, MN -- September 12, 2007 -- People with multiple sclerosis (MS) who stop taking the drug natalizumab may experience a rebound increase in disease activity, according to a study published in the online edition of the journal Neurology.
The study involved 21 people who had brain magnetic resonance imaging (MRI) scans taken before they started taking natalizumab and again an average of 15 months after receiving the last infusion of the drug.
Participants received natalizumab by IV infusion once a month and were divided into two groups: one continued treatment for an average of 3 years, the other for an average of 2 months.
Results show three times as many brain lesions -- markers of MS disease activity -- in the 15-month period after discontinuing the drug than they had in the baseline MRI. The results were most pronounced for those who stopped taking the drug after a treatment period; these patients developed five times as many brain lesions after stopping the drug than they had at baseline.
More research needs to be done with larger numbers of patients before any recommendations can be made about use of the drug, said study author Machteld Vellinga, MD, of VU University Medical Center in Amsterdam, the Netherlands. "For now the recommendations remain the same -- patients and their doctors should choose the most applicable treatment for them," she said.
Dr. Vellinga said it's not clear why discontinuing the drug would lead to increased disease activity, although an earlier animal study showed a similar result when rats with an animal model of multiple sclerosis were given a drug that suppresses the immune system.
The study was conducted because use of natalizumab was suspended in 2005 after three people participating in clinical trials of the drug developed progressive multifocal leukoencephalopathy -- a rare, often fatal condition.
"All of our patients had an MRI shortly after the drug was suspended, and our neuroradiologist noticed that in some patients a considerable number of new lesions developed on their MRIs in the following year," said Dr. Vellinga. "We decided to do a formal analysis to see if this was actually the case."
She noted that the results need to be confirmed in independent groups of patients.
The drug was reintroduced in 2006 with specific guidelines for its use and to monitor patients for signs of progressive multifocal leukoencephalopathy.
SOURCE: American Academy of Neurology