Main study: switch sub-study: switch-jcv

Treatment tested

• Teriflunomide

  Dihydroorotate dehydrogenase inhibitor

Other measures (3)

MAIN STUDY Inclusion Criteria: * Male and female patients, age 21 to 60 with relapsing forms of MS, treated with natalizumab for 12 consecutive months or longer with anti-JCV Ab positive during that time period. * Able to understand and sign Informed Consent Document. * Stable disease during treatment with natalizumab. No clinical relapses for at least 12 months. * Stable MRI on follow-up MRI scans for prior 12 months without evidence of new or enlarging T-2 hyperintensities or Gd+ lesions. * No clinical evidence by imaging or cerebrospinal fluid (CSF) for PML. * No evidence of significant cognitive limitation or psychiatric disorder. * Expanded Disability Status Scale (EDSS) of 1.0 to 6.0 inclusive. Exclusion Criteria: * Any mental condition of such that patient is unable to understand the nature, scope and possible consequences of the study. * Patients that are known HIV positive. * Patients with a known history of hepatitis. * Known history of active tuberculosis not adequately treated, or a positive ppd skin test or positive quantiferon gold. * Any persistent or severe infection. * Any malignancy within 5 years, except for Basal or Squamous cell skin lesions, which have been surgically excised, with no evidence of metastasis. * Clinically relevant or unstable cardiovascular, neurological (i.e. progressive weakness, increasing hypesthesia), endocrine, or other major systemic diseases. * History of drug or alcohol abuse within the past year. * Any significant depression or psychiatric disease (BDI II greater than 25) within the past year. * Any significant lab abnormality as deemed by the investigator including but not limited to the following: 1. Hypoproteinemia with serum albumin \< 3.0g/dl. 2. Serum creatinine >133umol/L (or >1.5 mg/dl) 3. Hematocrit \<24% and/or 4. Absolute white blood cell count \< 4,000 cells/mm3 (µl) and/or 5. Platelet Count \<150,000 cells/mm3 (µl) and /or 6. Absolute neutrophil \< 1,500 cells/mm3 (µl) 7. Liver function impairment or persisting elevations of serum glutamate pyruvate transaminase (SGPT)/ Alanine transaminase (ALT), serum glutamate oxaloacetate transaminase (SGOT)/ aspartate aminotransferase (AST), or direct bilirubin greater than 1.5 fold the upper limit of normal. * Any confounding illness or other diseases of the spine or bone that would impair evaluation of the patient or treatment effects. * Any clinical, CSF or MRI evidence for PML. * Prior treatment with immunosuppressive drugs except for past use of intravenous steroids to treat MS relapses. * Pregnant or breast feeding women. * Women of childbearing potential not protected by effective contraceptive method of birth control and/or are unwilling or unable to be tested for pregnancy. * In the conception of a child during the course of the trial. * Known history of hypersensitivity to teriflunomide or leflunomide. * Persisting elevations (confirmed by retest) of serum amylase or lipase greater than 2-fold the upper limit of normal. * Known history of chronic pancreatic disease or pancreatitis. * Prior use within 4 weeks before randomization or concomitant use of phenytoin, warfarin, tolbutamide, cholestyramine, or products containing St. John's Wort SUB-STUDY Eligibility Criteria for JCV sub-study: * Must have been enrolled in the SWITCH protocol and received at least 1 dose of 14mg TFM during the study period. * Must be willing to sign written, informed consent for this JCV sub-study and follow protocol requirements.

MAIN STUDY: The purpose of this study is to determine if teriflunomide will be safe and effective to prevent relapses in patients with relapsing types of MS when switching from natalizumab to teriflunomide in patients at risk for PML. This is a two center interventional study of patients who have had 12 or more continuous infusions of natalizumab , who are anti-JCV-ab positive, and who had been free of clinical relapses during prior 12 months of natalizumab therapy who will be switching to teriflunomide. SUB-STUDY: To study the number of patients experiencing a reduction in the anti-JCV antibody Index value in patients who had received at least one dose of teriflunomide during participation in the SWITCH protocol (main study).