Trials on MS drug Tysabri renews hope for sufferers

Mar 5 2006

According to the results of two new trials the multiple sclerosis (MS) drug Tysabri significantly reduces the progression of the disease.

Multiple sclerosis is a disease of the central nervous system, which afflicts about 350,000 Americans and is more common among women than men.

The disease is progressive, there is no cure and the cause is unknown.

Symptoms include trouble with vision and walking, and the most common form causes a periodic flare-ups of symptoms.

Tysabri produced by Cambridge-based Biogen IDEC and Elan Pharmaceuticals of Ireland, was originally approved by the U.S. Food and Drug Administration in November 2004 for the treatment of MS, but it was suspended in February 2005 after it was linked to a small risk of a serious neurological disease called progressive multifocal leukoencephalopathy (PML).

Three patients taking the drug developed PML and two of them died.

Following these events, questions were also raised about the drug's effectiveness, and Dr. Eugene O. Major, from the National Institute of Neurological Disorders and Stroke in Bethesda, Maryland, and colleagues set up an independent committee to evaluate suspected cases of PML in 3417 patients exposed to the drug in clinical trials.

Of the 44 patients with possible PML referred to the committee. PML was ruled out in 43, and 1 case was classified as indeterminate.

The three previously reported cases did seem to be actual PML.

In one of the two latest studies, Dr. Chris H. Polman, from the VU Medical Center in Amsterdam, and his team randomly assigned 942 patients with relapsing remitting MS, to receive either Tysabri or a placebo injection every four weeks.

The researchers discovered after 2 years of treatment, the patients on Tysabri had a 42 percent decrease in the risk of a sustained progression of disability and 59 percent reduction in the risk of relapse.

The active treatment also reduced the number of new or enlarging MS lesions in the brain by 83 percent in comparison to those on the placebo.

The second trial of 1171 MS patients who had at least one relapse during a 12-month period while they were being treated with Interferon, were randomly assigned by Dr. Rudick and his colleagues to receive Tysabri or a placebo every 4 weeks while continuing with the Interferon.

The combined treatment over a 2 year period resulted in a 24 percent decrease in the risk of sustained disability progression, a 55 percent reduction in rate of relapse, and an 83 percent reduction in new or enlarging lesions, compared with Interferon alone.

According to Dr. Rudick, Tysabri performed better in the two trials than the currently available drugs used to treat the disease, Interferon and Copaxone.

Rudick says the suspension of the drug in 2005 was devastating to many patients for whom current therapies are of little benefit.

The new studies found that Tysabri alone or with standard Interferon treatment could cut the rate of relapse by as much as two-thirds after two years and reduced the number of people whose MS worsened, compared to those on the placebo or Interferon alone.

Dr. Rudick hopes that the FDA will again approve the use of Tysabri with close monitoring by doctors, so that the early symptoms of PML can be recognized and the Tysabri stopped.

He believes patients should be fully informed before they make the decision to take Tysabri.

The trials are reported in the New England Journal of Medicine, March 2, 2006.