The primary objective of this safety/mechanistic study is to determine the safety and tolerability of oral Cellcept when compared with weekly intramuscular Avonex in relapsing multiple sclerosis. Safety will be assessed by virtue of changes in size and number of lesions on MRI scans.

Sixty patients (20 patients at each recruiting center) with RR MS who satisfy both inclusion and exclusion criteria will be treated with CellCept® or Avonex® for the first 6 months of the study. Those patients will have a fifty-fifty chance of receiving either Avonex or Cellcept. Baseline data will be collected before treatment begins including MRIs, chest x-ray, EKG, and standard labwork, along with a blood test for HIV and Hepatitis B. Once enrolled, study visits include periodic MRI scans, a neurological exam by the examining neurologist every three months, frequent bloodwork, questionnaires, and eye-testing at month zero, six, and twelve months. Eye testing takes about one hour and requires dilation of pupils. All assessments are standard of care for ophthalmology with the exception of optical coherence tomography (OCT)-- a non-invasive procedural device that records graphical and numerical measurements of the optic nerve and macula.

All patients will begin active combination therapy on both CellCept® and Avonex® during the second 6 months of the study. During this second phase, MRI and clinical examinations will be performed.

Inclusion Criteria:

• Patient diagnosed with clinically definite MS according to McDonald criteria #1-#4
• Age 18-55
• Have a RR disease course
• Have EDSS scores less than or equal to 5.0
• Have a disease duration of one day to 20 years
• Have at least one medically documented clinical relapse within the 12 months prior to randomization (for eligibility, a pre-study relapse will be defined as neurologic symptoms and signs documented by review of the history with the subject or in the medical record, of sufficient severity and duration to be determined by the investigator as consistent with an acute MS relapse; the relapse does not need to have been treated to qualify) and/or have progression of ≥1.0 points in EDSS in the previous year
• Have ≥1 Gd-enhancing brain lesion on a monthly run-in baseline MRI and ≥2 T2 brain lesions consistent with MS on the screening scan
• Signed informed consent
• None of the exclusion criteria

Exclusion Criteria:

• Previous treatment 3 months prior to study entry with standard disease-modifying therapy (interferon-beta and glatiramer acetate, IVIG and plasmaphoresis).
• Previous treatment 12 months prior to study entry with immunosuppressant agents, e.g., mitoxantrone, cyclophosphamide, cladribine, fludarabine, cyclosporine or total body irradiation or any other concomitant immunomodulatory therapies (e.g., azathioprine, methotrexate,, CellCept®, natalizumab, and other immunomodulators/monoclonal agents).
• Patients who received steroid treatment 30 days prior to the MRI scan date
• Women who are pregnant, lactating or of childbearing age who do not consent to approved contraceptive use during the study.
• Abnormal blood tests, performed during the screening visit (see adverse events section)