Cladribine Tablets: Collaborative Study to Evaluate Impact On Central Nervous System Biomarkers in Multiple Sclerosis

All participants will receive cladribine 10 mg tablets at a cumulative dosage of 3.5 mg/kg divided into 2 treatment courses as per the United States Prescribing Information (USPI) (1.75 mg/kg per treatment course; Year 1 and Year 2 treatment). Patients will be randomized 1:2:2:1 to receive a total of 2 Lumbar Punctures at specific time points during the treatment cycle.