NEW YORK (AP) -- French drugmaker Sanofi said Monday that the Food and Drug Administration will review its experimental multiple sclerosis treatment Lemtrada.

Genzyme, Sanofi's U.S. biotech business, said the FDA will conduct a standard 10-month review and will make a decision on the drug in late 2013. Sanofi wants to market Lemtrada as a treatment for relapsing multiple sclerosis. German drugmaker Bayer will have an option to help market the drug in the U.S. if it is approved.

Genzyme filed for marketing approval of Lemtrada in June, but the FDA refused the application because it wanted Genzyme to make changes to its application. European Union regulators are also reviewing the drug.

Sanofi also gave an update on early sales of Aubagio, an MS drug that was approved in September 2012 and launched in October. The company said more than 80 percent of U.S. multiple sclerosis specialists have written a prescription for the drug. About half of the patients who are taking Aubagio were most recently treated with Teva Pharmaceutical Industries Ltd.'s drug Copaxone or Biogen Idec Inc.'s Avonex. About 20 percent of patients hadn't been treated before.

U.S shares of Sanofi fell 17 cents to $49.10 in morning trading.