The study is divided into a Core Phase, which includes the Double-Blind Treatment Period, and an Extension Phase in which all patients will be treated with fingolimod. The Core Phase is a 24-month, double-blind, randomized, active-controlled, parallel-group multicenter study phase to evaluate the efficacy and safety of fingolimod compared to IFN β-1a in children/adolescent patients aged 10-17 years old with MS. The Extension Phase is a 60-month (5 year) study phase for patients who complete the Core Phase of the study and meet all inclusion/exclusion criteria and for patients who will be recruited in the younger cohort to participate in the Extension Phase. The 'younger cohort' refers to the population of pediatric patients fulfilling any single one or a combination of the following criteria: being ≤12 years of age, or weighing ≤40 kg, or being prepubertal (i.e. pubertal status of Tanner stage \<2). The recruitment of the younger cohort (up to 25 patients) was requested as a post- approval health authority commitment
