• To evaluate the efficacy of cladribine versus placebo in the reduction of qualifying relapse rate during 96 weeks of treatment in subjects with RRMS. [ Time Frame: During 96 weeks ] [ Designated as safety issue: Yes ]
  

• To assess the effect of cladribine on progression of disability in subjects with RRMS [ Time Frame: At 96 weeks ] [ Designated as safety issue: Yes ]
  

This was a randomized, double-blind, three-arm, placebo-controlled, multi-center study. The study included a pre-study evaluation period (up to 28 days prior to the start of treatment); an initial treatment period during weeks 1 to 48; and a retreatment period during weeks 49 to 96.

During the initial treatment period, weeks 1 to 48, eligible subjects were equally randomised by a central randomisation system to receive either a) cladribine at a low dose (0.875 mg/kg/course for two courses + 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 retreatment period in 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 was a rescue option of treatment with Rebif® (interferon beta-1a 44 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 =/>1 point, or =/>1.5 points if baseline EDSS score was 0, (over a period of three months or greater), during a calendar year beginning at Week 24.

To maintain the blind, there was a Treating Physician who viewed clinical laboratory results and assess adverse events and safety information, and an independent blinded Evaluating Physician who performed neurological exams. A central neuroradiology center, also blinded to treatment, assessed MRI evaluations.