Patient description: The patient is a 20 year old Caucasian female presents to the clinic with one-sided vision lost and facial weakness, dysarthria and numbness lasting for 1 day. She visited her PCP and underwent brain MRI which revealed a single plaque in the brainstem. After few months, she experienced lower extremities weakness led to balance problem. The second MRI revealed another lesion in the left cerebral hemisphere. The diagnosis of Relapsing Remitting Multiple Sclerosis (RRMS) is confirmed after the second MRI. Her past surgical history is significant for a C-section 2 years ago and she has a one child. She is divorced and is not currently in any sexual relationship. She smokes 10 cigarettes per day and drinks alcohol occasionally. She is working as an editor in a publisher company and she is happy that she can keep working from home most of the time. She is under the treatment of RRMS from 7 months ago.

Clinical trial eligibility criteria: eligible ages (years): 18.0-60.0,  Relapsing Remitting Multiple Sclerosis (RRMS) Key Must give written informed consent and provide all authorizations required by local law (for example, Protected Health Information [PHI]) Men or women between 18 and 60 years of age, inclusive Must have Expanded Disability Status Scale (EDSS) less than or equal to 5.5 at baseline Must be able to walk at least 100 m without assistive devices Must be natalizumab-naïve Must have a documented diagnosis of a relapsing remitting form of multiple sclerosis (MS0 as defined by the revised McDonald Committee (Polman et al., 2005) Must have had a recent (within 3 months from baseline) magnetic resonance imaging (MRI) Must have had at least 1 relapse in the previous year and must satisfy the locally approved therapeutic indications for Tysabri. If Tysabri is not yet approved in a specific country, patients must fulfill the following Patients with high disease activity despite treatment with a beta-interferon defined as patients who have failed to respond to a full and adequate course of a beta-interferon  Unless otherwise specified, candidates will be excluded from study entry if any of the following exist at the time of the Screening Visit Onset of a relapse within 50 days prior to first infusion Considered by the Investigator to be immunocompromised, based on medical history, physical examination, or laboratory testing or due to prior immunosuppressive treatment History of, or available abnormal laboratory results indicative of, any significant cardiac, endocrinologic, hematologic, hepatic, immunologic, metabolic, urologic, pulmonary, gastrointestinal, dermatologic, psychiatric (including major depression), renal, and/or other major disease that would preclude the administration of a recombinant humanized antibody immunomodulating agent. The Investigator must re-review the subject's medical fitness for participation and consider any diseases that would preclude treatment History of malignancy (subjects with basal cell carcinoma that has been completely excised prior to study entry remain eligible) Known history of human immunodeficiency virus infection or hematological malignancy History of organ transplantation (including anti-rejection therapy) A clinically significant infectious illness (cellulitis, abscess, pneumonia, septicemia) within 30 days prior to the Screening Visit Treatment with immunosuppressant medications (mitoxantrone, cyclophosphamide, cyclosporine, azathioprine, methotrexate) within 6 months prior to Screening