Exploratory Study of the Safety, Tolerability and Efficacy of Multiple Regimens of Natalizumab in Adult Participants With Relapsing Multiple Sclerosis (MS)

This is a a dose and frequency (but not route of administration) blinded, prospective, randomized, dose-ranging study in patients with RRMS who have received natalizumab for at least 12 months according to the local prescribing guidelines. The study will explore dosing of natalizumab by subcutaneous and intravenous routes. Participants will be randomly assigned to 1 of 6 dosing regimens, blinded to natalizumab dose, but not route, for 60 weeks of treatment.