U.S. approves new multiple sclerosis drug

A new but potentially costly treatment for multiple sclerosis has received fast-track approval from the U.S. Food and Drug Administration.

The drug Tysabri, formally called Antegren, prevents white blood cells from migrating to the central nervous system and flooding the brain, where the cells can cause damage.

The FDA approved the drug based on the results of a study on 942 patients with relapsing-remitting MS, the earliest phase of the disease.

After one year of the study, patients on Tysabri had two-thirds fewer relapses or attacks compared to patients given a placebo.

"In general, you can say that this is the greatest therapeutic effects ever seen in year one for a trial of a multiple sclerosis drug," said Dr. Paul O'Connor, the lead Canadian investigator for the trial.

Doctors also saw fewer brain lesions in the MRI scans of those taking Tysabri, and those in the drug group reported few side effects.

Like the FDA, Health Canada found the results impressive enough to give the drug priority for review. It will make its decision about the drug in the new year.

All patients in the trial now receive monthly treatments of Tysabri as investigators study the long-term effects of the drug.

Until Tysabri has gone through several years of testing, no one can say if the therapy achieves its goal of stopping the early form of MS from progressing to a more disabling phase.

When the drug is approved in Canada, it is likely to be expensive.

"It will be a significant cost for those that do not have proper drug coverage," said Mel Grant of Toronto, one of the patients in the drug trial. "There is some talk that it could cost up to $20,000 a year."