CLARITY

Treatment tested

• Cladribine

  DNA inhibitor

Placebo or sham

• Placebo

Other measures (3)

Inclusion Criteria: * Male or female, between 18 and 65 years of age (inclusive, at time of informed consent) * Has definite MS according to the McDonald criteria * Has relapsing-remitting disease with 1 or more relapses within 12 months prior to Study Day 1 * Must have been clinically stable and not has a relapse within 28 days prior to Study Day 1 * Has MRI consistent with MS at the pre-study evaluation according to the Fazekas criteria * Has a EDSS score from 0 to 5.5, inclusive * Weighed between 40-120 kilogram (kg), inclusive * If female, she must: 1. be post-menopausal or surgically sterilized; or 2. uses a hormonal contraceptive, intra uterine device, diaphragm with spermicide, or condom with spermicide, for the duration of the study; and 3. be neither pregnant nor breast-feeding * If male, he must be willing to use contraception to avoid pregnancies * Be willing and able to comply with study procedures for the duration of the study * Voluntarily provides written informed consent, and for United states of America (USA) sites only, a subject authorization under Health Insurance Portability and Accountability Act (HIPAA) Exclusion Criteria: * Has secondary progressive MS (SPMS) or primary progressive MS (PPMS) * Prior use of disease modifying drugs (DMDs) within the last 3 months, or 2 or more prior treatment failures with DMDs on the basis of efficacy * Has significant leukopenia (white blood cell count less than 0.5 times the lower limit of normal of the central laboratory) within 28 days prior to Study Day 1 * Has received cladribine, mitoxantrone, total lymphoid irradiation, myelosuppressive therapy, campath-1h, cyclophosphamide, azathioprine, methotrexate or natalizumab * Has received oral or systemic corticosteroids or adrenocorticotropic hormone within 28 days prior to Study Day 1 * Has compromised immune function or infection * Has received oral or systemic corticosteroids or adrenocorticotropic hormone within 28 days prior to Study Day 1 * Has received cytokine-based therapy, intravenous immunoglobulin therapy, or plasmapheresis within 3 months prior to Study Day 1 * Has platelet and absolute neutrophil counts below the lower limit of normal range within 28 days prior to Study Day 1 * Has prior or current history of malignancy * Has a history of persistent anemia, leukopenia, neutropenia, or thrombocytopenia after immunosuppressive therapy * Has systemic disease that, in the opinion of the Investigator, might interfere with subject safety, compliance or evaluation of the condition under Study (for example, insulin-dependent diabetes, Lyme disease, clinically significant cardiac, hepatic, or renal disease, Human Immunodeficiency Virus, or Human T-Cell Lymphotrophic Virus Type-1) * Has a psychiatric disorder that, in the opinion of the Investigator, was unstable or would preclude safe participation in the study * Has allergy or hypersensitivity to gadolinium, to cladribine or any of its excipients * Has used any investigational drug or experimental procedure within 6 months prior to Study Day 1

The purpose of the study is to determine if cladribine tablets are a safe and effective treatment for relapsing-remitting multiple sclerosis (RRMS).