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.