The U.S. Food and Drug Administration has notified drug maker Genzyme that its treatment for multiple sclerosis is not ready for approval for the American market.

The French pharmaceutical company Sanofi, which is the parent of Genzyme, said in a statement Monday that the FDA said the companies had not submitted sufficient evidence to show the benefits of Lemtrada. The drug was approved by the European Medicines Agency for use in the EU earlier this year.