A Two Year, Multicenter, Randomized, Double-Blind, Placebo-Controlled, Parallel Group Trial to Evaluate Efficacy, Safety, Tolerability, and Pharmacokinetics of Teriflunomide Administered Orally Once Daily in Pediatric Patients With Relapsing Forms of Multiple Sclerosis Followed by an Open-Label Extension

Primary Objective: To assess the effect of teriflunomide in comparison to placebo on disease activity measured by time to first clinical relapse after randomization in children and adolescents 10 to 17 years of age with relapsing forms of multiple sclerosis (MS). Secondary Objective: - To assess the effect of teriflunomide in comparison to placebo on disease activity/progression measured by brain magnetic resonance imaging (MRI) and on cognitive function. - To evaluate the safety and tolerability of teriflunomide in comparison to placebo. - To evaluate the pharmacokinetics (PK) of teriflunomide.