MAIN STUDY: SWITCH SUB-STUDY: SWITCH-JCV

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:
• Hypoproteinemia with serum albumin 133umol/L (or >1.5 mg/dl)
• Hematocrit <24% and/or
• Absolute white blood cell count < 4,000 cells/mm3 (µl) and/or
• Platelet Count <150, 000 cells/mm3 (µl) and /or
• Absolute neutrophil < 1,500 cells/mm3 (µl)
• 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.