 The main objectives of Part 1 are as follows: To evaluate the safety, tolerability, and efficacy of BG00012 in pediatric subjects with RRMS, as compared with a disease-modifying treatment and to assess health outcomes and evolution of disability. The primary objective of Part 2 is to evaluate the long-term safety of BG00012 in subjects who completed Week 96 in Part 1 of Study 109MS306. The secondary objective of Part 2 is to describe the long-term MS outcomes of BG00012 in subjects who completed Week 96 in Part 1 of Study 109MS306. 