A new drug to treat multiple sclerosis is showing hopeful results in clinical trial and could be on the market in Canada about a year.

Dr. Douglas Arnold of the Montreal Neurological Institute hails the result of the primary progressive study as a breakthrough.

Arnold was part of three large phase 3 clinical trials on the drug ocrelizumab conducted worldwide.

The studies were published Thursday in the New England Journal of Medicine.

The experimental drug was compared to a traditional MS therapy: interferon beta 1a.

“The new drug was much more effective than the comparator and it most importantly, slowed progression of the disease by about 25 per cent over the course of the trial,” he said.

In the two other studies involving patients who have the more common relapsing-remitting type of MS, the benefits were clear.

“In this case the progression was also slowed by an even greater amount, by about 40 per cent, and the relapses which are characteristic of that MS were also reduced by about 50 per cent,” said Arnold.

MRI scans demonstrated the drug stopped the formations of new lesions in the brain.

“When I see a drug that blocks 98 per cent of new lesion formation, I'm blown away by the efficacy of that drug,” said the doctor.

Arnold says the drug has been tested on thousands of patients, and so far has not caused any significant side effects.

The drug is now before Health Canada for regulatory approval.