A Phase II Study Comparing Low- and High-Dose Alemtuzumab and High-Dose Rebif® in Patients With Early, Active Relapsing-Remitting Multiple Sclerosis

Inclusion Criteria: Signed informed consent form (ICF) Male or non-pregnant, non-lactating female participants, 18 to 50 years of age (inclusive) as of signing the ICF Diagnosis of MS per McDonald's update of the Poser criteria, including cranial MRI consistent with those criteria (McDonald, 2001, Ann Neurol) Onset of first MS symptoms within 3 years prior to Screening as of signing the ICF Expanded Disability Status Scale (EDSS) score 0.0 to 3.0 (inclusive) at the screening and Baseline visits At least 2 completed clinical episodes of MS in the 2 years prior to study entry (that is, the initial event if within 2 years of study entry plus at least 1 relapse, or at least 2 relapses if the initial event was between 2 and 3 years prior to study entry) In addition to the clinical criteria, at least 1 enhancing lesion on any 1 of up to 4 screening gadolinium-enhanced MRI brain scans during a maximum 3-month run-in period (inclusive of the Month 0 Baseline scan) Exclusion Criteria: Previous immunotherapy for MS other than steroids, including treatment with interferons, intravenous immunoglobulin (IVIG), glatiramer acetate, and mitoxantrone Personal history of thyroid autoimmune disease Personal history of clinically significant autoimmune disease (for example, inflammatory bowel disease, diabetes, lupus, severe asthma) History of thyroid carcinoma (previous thyroid adenoma was acceptable and was not considered an exclusion criterion) History of malignancy (except for basal cell skin carcinoma if disease-free for at least 5 years) Any disability acquired from trauma or another illness that, in the opinion of the Investigator, interfered with evaluation of disability due to MS Previous treatment with alemtuzumab History of anaphylaxis following exposure to humanized monoclonal antibodies Inability to undergo MRI with gadolinium administration Female participants of childbearing potential with a positive serum pregnancy test at screening or Baseline Male and female participants who did not agree to use effective contraceptive method(s) during the study Impaired renal function (that is, serum creatinine greater than or equal to 2 times the upper limit of normal [ULN]) Untreated, major depressive disorder Epileptic seizures that were not adequately controlled by treatment Suicidal ideation Major systemic disease or other illness that, in the opinion of the Investigator, have compromised participant safety or interfered with the interpretation of study results Abnormal CD4 count or significantly abnormal thyroid function; presence of anti-thyroid stimulating hormone (TSH) receptor antibodies; known seropositivity for human immunodeficiency (HIV) Intolerance of pulsed corticosteroids, especially a history of steroid psychosis Presence of a monoclonal paraprotein Participants who had any form of MS other than relapsing-remitting Participants currently participating in a clinical study of an experimental or unapproved/unlicensed therapy