A Safety and Efficacy Study of Oral Cladribine in Subjects With Relapsing-remitting Multiple Sclerosis (RRMS)

This is a randomized, double-blind, three-arm, placebo-controlled, multi-center study. The study includes a pre-study evaluation period (up to 28 days prior to the start of treatment); an initial treatment period from Week 1 to 48; and a re-treatment period during Week 49 to 96. During the initial treatment period (Week 1 to 48), eligible subjects are equally randomized by a central randomization system to receive either a) cladribine at a low dose (0.875 milligram per kilogram per course \[mg/kg/course\] for two courses plus placebo for two courses); b) cladribine at a high dose (0.875 mg/kg/course for four courses); or c) placebo (four courses). During the re-treatment period (Weeks 49 to 96), subjects received either a) cladribine at a low dose (0.875 mg/kg/course for two courses); or b) placebo (two courses). For all randomized subjects, there is a rescue option of treatment with Rebif® (interferon beta-1a 44 microgram (mcg) given subcutaneously three times a week), if the subject experienced more than one qualifying relapse, and/or experienced a sustained increase in their EDSS score of greater than or equal to (\>=) 1 point, or \>=1.5 points if baseline EDSS score is 0, (over a period of three months or greater), during a calendar year beginning at Week 24. To maintain the blind, there is a treating physician who view clinical laboratory results and assess adverse events and safety information, and an independent blinded evaluating physician who will perform neurological exams. A central neuroradiology center, also blinded to treatment, will assess magnetic resonance imaging (MRI) evaluations.