Investigating if Interferon-Beta Can be Used in Patients With MS After They Have Developed Neutralizing Antibodies

Inclusion Criteria: * Relapsing remitting Multiple Sclerosis according to Poser criteria (CDMS or LDMS) or Multiple Sclerosis according to McDonald criteria * Disability equivalent to EDSS of 6.0 or less * Clinical activity defined as at least one relapse rate within the last 12 months * NAb titre \>20 (measured at least 48 hours after last interferon-beta injection * has been treated with subcutaneously administered interferon-beta-1b or interferon-beta-1a (Rebif) for at least 24 hours before enrollment Exclusion Criteria: * Any condition that might give rise to similar symptoms as MS * Immunomodulatory therapy other than interferon-beta-1a or interferon-beta-1b or any immunosuppressive treatment six months prior to inclusion into the trial * Treatment with glucocorticoids or ACTH less than one month prior to inclusion into the trial * History of major depression * Alcohol or drug dependency * Cardiac insufficiency, cardiomyopathy, significant cardiac dysrhythmia, unstable or advanced ischemic heart disease (NYHA III or IV) * hypertension (BP \> 180/110 mmHg) * Renal insufficiency defined as serum creatinine \> 1.5 times the upper normal reference limit * Any systemic disease that can influence the patient's safety and compliance, or the evaluation of the disability * Gastro-intestinal ulcers, gastritis, or dyspepsia * Women who are pregnant, breast-feeding or have the possibility for pregnancy during the trial. To avoid pregnancy, women have to be postmenopausal, surgical sterile, sexually inactive or practice reliable contraceptives