Oral Cladribine in Early Multiple Sclerosis (MS)

This will be a randomized, double blind, three-arm, placebo-controlled, multi-center trial to evaluate the safety and efficacy of oral cladribine versus placebo in the treatment of participants who have sustained a first clinical demyelinating event within 75 days prior to the Screening. Participants must have a minimum of 2 clinically silent lesions on the Screening magnetic resonance imaging (MRI). The study will include a pre-study evaluation period (Screening period: between 10 and 28 days prior to the start of treatment with blinded study medication (oral cladribine or placebo). Depending upon the clinical course of their MS, participants will then proceed from the ITP to either the Maintenance Treatment Period (with open-label interferon-beta treatment) or LTFU period (with either open-label low-dose cladribine or no additional treatment (if no progression to MS has been noted after the initial treatment period). The single primary endpoint for the overall study, which will be determined during the ITP, is time to conversion to MS (from randomization), according to the Poser criteria. For every participants, eligibility for study enrollment and entry into each of the study periods, and diagnosis of conversion to either McDonald MS or CDMS must be confirmed and approved by a Sponsor appointed study Adjudication Committee.