EDSS is an ordinal scale in half-point increments that qualifies disability in participants with MS. It assesses 7 functional systems (visual, brainstem, pyramidal, cerebellar, sensory, bowel/bladder and cerebral) as well as ambulation. EDSS total score: 0 (normal neurological examination) to 10 (death due to MS). As measured by EDSS score, SAD was defined as increase of at least 1.5 points for participants with Baseline score of 0 and increase of at least 1.0 point for participants with a Baseline score of 1.0 or more; and the increase persisted for at least the next 2 scheduled assessments, that is, 6 consecutive months. The onset date of SAD was date of first EDSS assessment that began 6 month consecutive period of SAD. Participants who did not reach SAD endpoint were censored at their last visit. Percentage of participants with SAD, estimated by Kaplan-Meier (KM) method, was reported.

FAS population included all randomized participants who received at least 1 dose of study drug as per initial randomization. Analysis was not performed for Alemtuzumab 24 mg as recruitment to this arm was closed early to reduce overall sample size, duration of enrollment period, overall duration of study.

Relapse was defined as new neurological symptoms or worsening of previous neurological symptoms with an objective change on neurological examination, attributable to multiple sclerosis that lasted for at least 48 hours, that were present at normal body temperature, and that were preceded by at least 30 days of clinical stability. Annualized relapse rate was estimated through negative binomial regression with robust variance estimation and covariate adjustment for geographic region using observed number of relapses as dependent variable, the log total amount of follow-up from date of first study treatment for each participant as an offset variable, and treatment group and geographic region as model covariates.

FAS population. Analysis was not performed for Alemtuzumab 24 mg as described in outcome measure 1.

Participants were considered relapse free at Year 2 if they did not experience a relapse from the date of first study treatment to study completion at 24 months. Percentage of participants who were relapse free at Year 2, estimated using the KM method, was reported.

FAS population. Analysis was not performed for Alemtuzumab 24 mg as described in outcome measure 1.

EDSS is an ordinal scale in half-point increments that qualifies disability in participants with multiple sclerosis (MS). It assesses the 7 functional systems (visual, brainstem, pyramidal, cerebellar, sensory, bowel/bladder and cerebral) as well as ambulation. EDSS total score ranges from 0 (normal neurological examination) to 10 (death due to MS). Change was calculated by subtracting Baseline value from value at Year 2.

FAS population. Here, number of participants analyzed was subset of FAS who had EDSS assessment at both Baseline and end-of-study (Year 2). Analysis was not performed for Alemtuzumab 24 mg as described in outcome measure 1.

MSFC is a multidimensional measure consisting of quantitative tests of ambulation (Timed 25-Foot Walk), manual dexterity (9-Hole Peg Test; 9HPT), and cognitive function (Paced Auditory Serial Addition Test; PASAT). The MSFC score was calculated as the mean of the Z-scores of the 3 components. A Z-score was calculated by subtracting the mean of the reference population from the test result, then dividing by the standard deviation of the reference population. Higher Z-scores reflected better neurological function and a positive change from Baseline indicates improvement. An increase in score indicated an improvement (Z-score range: -3 to +3). Acquisition of disability was measured by change from Baseline in MSFC score at Year 2.

FAS population. Here, number of participants analyzed signifies subset of FAS who had MSFC score assessment at Baseline; 'n' signifies participants who had MSFC score assessment at Baseline (for Baseline) and at both Baseline and Year 2 (for change at Year 2). Analysis was not performed for Alemtuzumab 24 mg as described in outcome measure 1.

Percent change in MS lesion volume as measured by MRI-T2 scan was calculated from MRI-T2-weighted scans as the following: (lesion volume at 2 years - lesion volume at Baseline)*100/ (lesion volume at Baseline).

FAS population. Here, number of participants analyzed was subset of FAS who had assessment for T2 volume at both Baseline and end-of-study (Year 2). Analysis was not performed for Alemtuzumab 24 mg as described in outcome measure 1.