Stopping Tysabri May Worsen MS

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According to the U.S. National Institutes of Health, multiple sclerosis is an unpredictable disease of the central nervous system that can range from relatively benign to somewhat disabling, to devastating, as communication between the brain and other parts of the body is disrupted.

Many researchers believe MS to be an autoimmune disease, one in which the body, through its immune system, launches a defensive attack against its own tissues. In the case of MS, it is nerve-insulating myelin tissue that is under assault.

This trial was initiated after a neuroradiologist noticed that some patients were developing new lesions (as evidenced on MRI) after their Tysabri was discontinued.

All participants in this trial had had MRIs of their brains taken before starting Tysabri. They then had another such scan taken an average of 15 months after receiving the last infusion of the drug.

Participants were divided into two groups -- one which had taken the drug for an average of three years and one which had taken Tysabri for an average of only two months.

MRI scans revealed that participants developed more than triple the number of brain lesions (damaged areas) in the 15-month period since stopping the drug than they had developed before starting it. Those who had taken the drug for the shorter interval showed the most disease activity.

"Virtually all of the high-rebound figure came from the group that had a mean duration of therapy of only two months. I think that's relatively reassuring for the drug," Richert said.

MS symptoms did not show any sign of relapse, the team added.

The findings are in conflict with a previous study which found that people who had come off Tysabri did not show any rebound, Richert added. But the studies were a little different.

"They varied enough that both might be right, but we just don't know that yet," Richert added. "Nevertheless, this is something that needs further study. I don't think that at this point it changes the way physicians and people with MS should be using the drug. We continue to need to be vigilant in the use of Tysabri."

More information

The National Multiple Sclerosis Society can tell you more about multiple sclerosis.