A pill for multiple sclerosis reduces the relapse rates and slows progression of the disease, a safety study suggests.

The trial included 1,088 people with MS between the ages of 18 and 55 who were randomly assigned to take a high or low dose of the experimental pill, called teriflunomide, or a placebo. Participants were followed for two years.

The relapse rate for a year with the drug was better than with a placebo, Dr. Paul O'Connor and his co-authors said in Wednesday's online issue of the New England Journal of Medicine.

"The magnitude of the benefits observed in patients receiving teriflunomide was modest but similar to those reported for the existing injectable disease-modifying therapies approved for use in patients with multiple sclerosis," the study's authors concluded.

Most MS drugs are given by injection. There is only one licensed MS drug that is given in pill form.

Since teriflunomide works differently in the body than MS drugs already licensed, it might be possible to use in combination with other treatments if safety hurdles are cleared, said Tim Coetzee, chief research officer for the U.S. National Multiple Sclerosis Society.

"We're not there yet," Coetzee said in an interview with The Canadian Press.

"But I'm a natural optimist who would say that, if approved, having this along with the other agents on the market allows you to think about new ways of treating the disease."

"One of the challenges of MS is that it's widely variable. And consequently some individuals respond differently than others. And so having another treatment option available that would show effectiveness for relapsing forms of the disease would be an important step forward."

In the study, a relapse was defined as either the appearance of a new symptom of the disease or a worsening of symptoms that had previously been stable. Symptoms include physical weakness or numbness, extreme fatigue, loss of vision and cognitive impairment.

The results included:

• Reduced rates of clinical relapse and a reduced risk of disease progression with the drug.
• Improved MRI measures of disease activity at both doses of the drug.
• No differences for fatigue, a common problem for people with MS.

There were no deaths. Serious infections were reported in 1.6 per cent in the placebo group, 2.5 per cent in the low-dose group, and 2.2 per cent in the high-dose group.

Diarrhea, nausea, and hair thinning were more common with teriflunomide than with placebo.

The drug's manufacturer, Sanofi-Aventis, funded the study, analyzed the data, and paid for a medical-writing service to help the authors prepare the manuscript.

With files from The Canadian Press