A Multicenter, Randomized, Double-blind, Parallel-group, Placebo-controlled Variable Treatment Duration Study Evaluating the Efficacy and Safety of Siponimod (BAF312) in Patients With Secondary Progressive Multiple Sclerosis Followed by Extended Treatment With Open-label BAF312.

Evaluate the safety and efficacy of Siponimod (BAF312) versus placebo in a variable treatment duration in patients with secondary progressive multiple sclerosis (Core Part) followed by extended treatment with open-label BAF312 to obtain data on long-term safety, tolerability and efficacy (Extension Part).