A Prospective Biomarker Study in Active SPMS Subjects Treated With Cladribine Tablets

After being informed about the study and potential risks, all patients giving written informed consent will undergo a screening period. Maximum allowable time between first screening procedure and first administration of study treatment will be 42 days. Subjects will have a 28 day run-in period consisting of 2 visits at week -4 and week -2. Subjects will have a Baseline day 1 visit. Study medication will commerce on the day following this visit. Additional visits will be at the following time points: week 4, week 8, week 12, week 16, week 24, week 36, week 48, week 52, week 56, week 60, week 72, week 84 and week 96.