The purpose of this study is to determine whether raising low levels of the natural antioxidant uric acid by the administration of a precursor, inosine, has any therapeutic effect on the progression of Relapsing Remitting Multiple Sclerosis (RRMS) and secondary progressive Multiple Sclerosis (MS).

Uric acid is a natural inhibitor of certain chemistries associated with peroxynitrite, a product of inflammation. In animal models of multiple sclerosis (MS), these chemical reactions have been associated with breakdown of the blood-brain barrier and CNS tissue damage. In addition, MS patients have serum uric acid levels that are lower than age- and sex- matched healthy individuals. The primary purpose of this study to determine whether raising low serum uric acid levels by daily oral administration of its precursor inosine has an effect on the cumulative number of newly active lesions on magnetic resonance imaging (MRI) and to evaluate the safety and tolerability of inosine in patients diagnosed with relapsing remitting and secondary progressive MS.

Inclusion Criteria:

• Nonpregnant, nonlactating females
• Females of child bearing potential must have a negative human chorionic gonadotropin (HCG) test result within 60 days before the first dose of study material.
• Males and females must practice adequate contraception, in the judgement of the investigator, during the course of the study.
• Subjects must have a diagnosis of clinically definite Relapsing Remitting Multiple Sclerosis based on medical history, physical examination, laboratory test results, and neurologic examination. Alternatively, subjects may have clinically probable MS characterized by 1 attack and the presence of at least 4 lesions on MRI within 12 months before the initial baseline evaluation.
• Subjects must have an Expanded Disability Status Scale (EDSS) test result of less than or equal to 5.0 within 60 days before the first dose of study material.
• Subjects will have serum uric acid levels less than 5 mg/dl.
• Have 1 clinical relapse in the last year

Exclusion Criteria:

• Presence of any medical disability or laboratory test result that, in the judgement of the investigator, would interfere with assessment of the tolerability, safety, or efficacy of study material or would compromise the subject's ability to provide informed consent.
• Evidence of active infection characterized by requiring treatment with antibiotics within 7 days before the first dose of study material.
• Treatment with interferons, glatiramer acetate, lymphoid irradiation, cyclophosphamide, or with other immune modifying treatments within 3 months, or corticosteroids within 1 month before the initial baseline MRI assessment in this trial.
• Recent history (within the previous 2 years) of drug or alcohol abuse.
• Known allergy to Inosine products or history of anaphylaxis.
• Previous randomization into this study.
• Treatment with an investigational agent within 30 days before the first dose of study material.