A Phase 2 Study of Cladribine Add-on to Interferon-beta (IFN-beta) Therapy in Multiple Sclerosis (MS) Subjects With Active Disease (ONWARD) (ONWARD)

Inclusion Criteria:

• Be male or female, 18 to 65 years of age (inclusive)
• Weigh between 40 to 120 kilogram (kg), (inclusive)
• Have definite MS, as confirmed by the revised McDonald criteria 2005, and have relapsing forms of MS, such as relapsing-remitting multiple sclerosis (RRMS) or SPMS with superimposed relapses
• Have experienced at least one relapse within 48 weeks prior to Screening, while receiving IFN-beta treatments (Rebif® 44mcg three times a week, subcutaneously; Avonex®30 mcg every week, intramuscular; or Betaseron® 250 mcg every other day, subcutaneously)
• Have a minimum time on IFN-beta therapy of 48-consecutive weeks prior to Screening. Participants who switched from one IFN-beta therapy to another in the 48 weeks preceding Screening may be entered into the study if they have been on a stable regimen of their current IFN-beta therapy for a minimum of 3 months prior to Screening
• Be clinically stable (other than MS relapse) during the 28 days preceding Screening

• The following hematological parameters must be normal (as defined below, inclusively) within 28 days of first dosing of blinded study medication at study day 1 (SD 1)

  • Hemoglobin=11.6 to 16.2 gram per deciliter (g/dL)
  • Leukocytes (total white blood cells [WBC])=4.1 to 12.3*10^3 per microliter (/UL)
  • Absolute lymphocytes count (ALC)= 1.02 to 3.36*10^3/UL
  • Absolute neutrophil count (ANC)=2.03 to 8.36*10^3/UL
  • Platelet count=140 to 450*10^3/UL
• Have no medical history or evidence of latent tuberculosis infection (LTBI) or active tubercular disease (TB), as evidenced by TB skin test or chest X-ray
• Have an expanded disability status scale (EDSS) from 1.0-5.5, inclusive
• Have no prior exposure to immunosuppressive or cytotoxic agents (with the exception of steroids for MS flare management, or intravenous immunoglobulin-G [IVIG] after allowed wash-out periods

• If female, must:

  • be neither pregnant nor breast-feeding, nor attempting to conceive, and
  • use a highly effective method of contraception throughout the entire duration of the study and for 6 months (6 menstrual cycles) following completion of the last dose of study medication. A highly effective method of contraception is defined as one which result in a low failure rate (that is, less than 1 percent per year) when used consistently and correctly, such as implants, injectables, combined oral contraceptives, some intrauterine devices (IUDs), sexual abstinence or a vasectomized partner. For the purpose of this trial, women of childbearing potential are defined as: All female participants after puberty unless they are post-menopausal for at least 2 years, or are surgically sterile
• If male, must be willing to use contraception to avoid pregnancies throughout the entire duration of the study and for 90 days following the last dose of study medication
• Be willing and able to comply with study procedures for the duration of the study
• Have not met any of the exclusion criteria outlined below; and
• Have voluntarily provided written informed consent, including, for United states of America (USA), participant authorization under Health Insurance Portability and Accountability Act (HIPAA), prior to any study-related procedure that is not part of normal medical care, and with the understanding that the participant may withdraw consent at any time without prejudice to future medical care
• Other protocol defined inclusion criteria may apply

Exclusion Criteria:

• Has primary progressive multiple sclerosis (PPMS) or SPMS without relapses forms
• Has prior or current malignancy other than medically documented complete excision of basal cell skin cancer no less than 5 years prior to Screening
• Has a history of chronic or clinically significant hematological abnormalities
• Prior use of cladribine, fingolimod, teriflunimide, laquinimod, mitoxantrone, campath-1h, cyclophosphamide, azathioprine, methotrexate, daclizumab, natalizumab, lymphoid irradiation, bone marrow transplantation or myelosuppressive/cytotoxic therapy
• Use of cytokine or anti-cytokine therapy or plasmapheresis within 3 months prior to SD 1
• Treatment with IVIG within 30 days of Screening
• Treatment with oral or parenteral corticosteroids 30 days of Screening
• Treatment with adrenocorticotropic hormone within 28 days prior to SD 1
• Use of any investigational drug (other than Rebif® New Formulation [RNF], Avonex® or Betaferon®) or experimental procedure within 6 months prior to SD 1
• Has inadequate liver function, defined by a total bilirubin, aspartate aminotransferase (AST), alanine aminotransferase (ALT) or alkaline phosphatase greater than 2.5 times the upper limit of the normal values
• Suffers from major medical illness such as cardiac, endocrinologic, hepatic, immunologic (other than MS), metabolic, renal, pulmonary, gastrointestinal, dermatologic, or other major disease that would preclude the administration of oral cladribine
• Suffers from major psychiatric illness (including history of, or current, severe depressive disorders and/or suicidal ideation) that in the opinion of the investigator creates undue risk to the participant or could affect compliance with the study protocol
• Has history of active or chronic infectious disease or any disease which compromises immune function (for example, human immunodeficiency virus [HIV]+, human T-lymphotropic virus [HTLV-1], Lyme disease, LTBI or TB)
• Has an allergy or hypersensitivity to gadolinium, to cladribine or any of its excipients, or IFN-beta or any of its excipient(s)
• Has any renal condition that would preclude the administration of gadolinium (for example, acute or chronic severe renal insufficiency [glomerular filtration rate less than 30 milliliter per minute {mL/min} per 1.73 square meter {m^2}])
• Has a positive stool hemoccult test at Screening
• Has a history of seizures not adequately controlled by treatment