Assessing Changes in Multi-parametric MRI in Patients With Acute Demyelinating Lesions Taking Clemastine Fumarate as a Myelin Repair Therapy (ReINFORCE)

Inclusion Criteria: Written informed consent must be obtained prior to any assessment being performed. Patients diagnosed with relapsing remitting multiple sclerosis and a disease duration of < 15 years Male or female patients aged 18-55 years (inclusive) Use of appropriate contraception during period of trial (women). Before entry women must be: Post-menopausal for at least 1 year OR Surgically sterile (have had a hysterectomy or bilateral oophorectomy, tubal ligation, male partner vasectomy or otherwise incapable of pregnancy) OR Practicing a highly effective method of birth control if sexually active, including hormonal prescription oral contraceptives, contraceptive injections, contraceptive patch, intrauterine device, double barrier method (e.g., condoms, diaphragm or cervical cap with spermicidal foam, cream or gel), or male partner sterilization consistent with local regulations regarding use of birth control methods for patients participating in clinical trials, for the duration of their participation in the study OR Not heterosexually active (patients who are not heterosexually active at screening must agree to utilize a highly effective method of birth control if they become heterosexually active during their participation in the study) OR Practicing true abstinence (when this is in line with the preferred and usual lifestyle of the subject) Period abstinence (e.g., calendar, ovulation, symptothermal, post ovulation methods) is not an acceptable method. Exclusion Criteria: Radiologic identification of marked brain atrophy relative to patients age based on recent MRI and interpretation of expert neuroradiologist or PI New lesion in most recent MRI (within 3 months) Hypersensitivity to clemastine or other arylalkylamine antihistamines, or any of the excipients. Treatment with corticosteroids within 30 days prior to screening. Expanded Disability Status Scale (EDSS) ≥ 4.5 History of significant cardiac conduction block. History of cancer. Suicidal ideation or behavior in 6 months prior to baseline. Pregnancy, breastfeeding or planning to become pregnant. Involved with other study protocols simultaneously without prior approval. Concomitant use of any other putative remyelinating therapy as determined by the investigator. Prior treatment with total lymphoid irradiation, T cell or T cell receptor vaccination. Prior treatment with alemtuzumab, mitoxantrone, or cyclophosphamide. Serum creatinine > 1.5 mg/dL; aspartate transaminase (AST), alanine transaminase (ALT), or alkaline phosphatase > 2 times the upper limit of normal. (Reported within 72 hours) History of drug or alcohol abuse within the past year. Untreated B12 deficiency (as determined by B12 serological assessments and metabolites including methylmalonic acid [MMA] and homocysteine) or untreated hypothyroidism. Clinically significant cardiac, metabolic, hematologic, hepatic, immunologic, urologic, endocrinologic, neurologic, pulmonary, psychiatric, dermatologic, allergic, renal, or other major diseases that in the PI's judgment may affect the interpretation of study results or patient safety. History of or presence of clinically significant medical illness or laboratory abnormality that, in the opinion of the investigator would preclude participation in the study Inability to participate in MRI, including extreme claustrophobia. Any dental braces or permanent or undetachable metals in the jaw or face.