 Study Design Rationale An adaptive design was chosen to characterize the dose response curve of BAF312. In a first period of study Period 1, three doses of BAF312 and placebo are tested for MRI efficacy. Based on an interim analysis IA after 3 months of treatment, two additional active doses for period 2 have been selected , thus allowing to optimize the overall determination of the dose response curve with 5 data points of active treatment, and placebo. The doses are kept blinded. The use of Modeling and Simulation allows to establish the full range and dynamics of the dose-response curve in silico, and hence the definition of the optimal dose for later phase III studies. 