Inclusion Criteria:

• Diagnosis of MS and MRI scan demonstrating white matter lesions attributable to MS
• Onset of MS symptoms within 10 years
• EDSS score 0.0 to 5.0
• ≥2 MS attacks within 24 months, with ≥1 attack within 12 months
• ≥1 MS attack (relapse)during treatment with a beta interferon therapy or glatiramer acetate after having been on that therapy for at least 6 months within 10 years

Exclusion Criteria:

• Previous treatment with alemtuzumab
• Previous treatment with any investigational drug (i.e. a medication that is not approved at any dose or for any indication)
• Treatment with natalizumab, methotrexate, azothioprine or cyclosporine in the past 6 months
• Previous treatment with mitoxantrone, cyclophosphamide, cladribine, rituximab, or any other immunosuppressive, or cytotoxic therapy (other than steroid treatment)
• Any progressive form of MS
• Any disability acquired from trauma or another illness that could interfere with evaluation of disability due to MS
• Major systemic disease that cannot be treated or adequately controlled by therapy
• Active infection or high risk for infection
• Autoimmune disorder (other than MS)
• Impaired hepatic or renal function
• History of malignancy, except basal skin cell carcinoma
• Medical, psychiatric, cognitive, or other conditions that compromise the patient's ability to understand the patient information, to give informed consent, to comply with the trial protocol, or to complete the study
• Known bleeding disorder
• Of childbearing potential with a positive serum pregnancy test, pregnant, or lactating
• Current participation in another clinical study or previous participation in CAMMS323
• Previous hypersensitivity reaction to any immunoglobulin product
• Known allergy or intolerance to interferon beta, human albumin, or mannitol
• Intolerance of pulsed corticosteroids, especially a history of steroid psychosis
• Inability to self-administer subcutaneous (SC) injections or receive SC injections from caregiver
• Inability to undergo MRI with gadolinium administration
• Unwilling to use a reliable and acceptable contraceptive method throughout the study period (fertile patients only)