REPORT FROM THE AMERICAN ACADEMY OF NEUROLOGY (AAN) ANNUAL MEETING, SAN DIEGO, CA, MARCH 16-23, 2013 – TOWER is the second of three phase III studies investigating the safety and efficacy of oral teriflunomide, the active metabolite of leflunomide which acts by inhibiting dihydroorotate dehydrogenase. The drug received FDA approval in September 2012 but has not yet been approved in Canada.