Jian Zhang, Shengliang Shi, Yueling Zhang, Jiefeng Luo, Yousheng Xiao, Lian Meng, Xiaobo Yang

Alemtuzumab is a humanised monoclonal antibody that alters the circulating lymphocyte pool, causing prolonged lymphopenia, thus remoulding the immune repertoire that accompanies homeostatic lymphocyte reconstitution. It has been proved more effective than interferon (IFN) 1a for the treatment of relapsing-remitting multiple sclerosis (RRMS). To compare the efficacy, tolerability and safety of alemtuzumab versus interferon beta 1a in the treatment of people with RRMS to prevent disease activity. We searched the Cochrane Multiple Sclerosis and Rare Diseases of the CNS Group Trials Register (1 February 2017) which, among other sources, contains records from CENTRAL, MEDLINE, Embase, CINAHL, LILACS, PEDRO and the trial registry databases Clinical Trials.gov and WHO International Clinical Trials Registry Platform for all prospectively registered and ongoing trials. All double-blind, randomised, controlled trials comparing intravenous alemtuzumab (12 mg per day or 24 mg per day on five consecutive days during the first month and on three consecutive days at months 12 and 24) versus subcutaneous IFN beta 1a (22 μg or 44 μg three times per week (Rebif) or intramuscular injection 30 μg once a week (Avonex)) in people of any gender and age with RRMS. We used standard methodological procedures expected by Cochrane. We included three trials involving 1694 participants. All trials compared alemtuzumab 12 mg per day or 24 mg per day versus IFN beta 1a for treating RRMS. In CAMMS223, participants received either subcutaneous IFN beta 1a 44 μg three times per week or annual intravenous cycles of alemtuzumab (at a dose of 12 mg per day or 24 mg per day) for 36 months. In CARE-MS I and CARE-MS II, participants received subcutaneous IFN beta 1a 44 μg three times per week or annual intravenous cycles of alemtuzumab 12 mg per day for 24 months. The methodological quality was good for all three studies.In the alemtuzumab 12 mg per day group, the results showed statistically significant difference in reducing relapses (risk ratio (RR) 0.60, 95% confidence interval (CI) 0.52 to 0.70), preventing disease progression (RR 0.60, 95% CI 0.45 to 0.79) and developing new T2 lesions on magnetic resonance imaging (RR 0.75, 95% CI 0.61 to 0.93) after 24 and 36 months' follow-up, but found no statistically significant difference in the changes of Expanded Disability Status Scale (EDSS) score (mean difference (MD) -0.35, 95% CI -0.73 to 0.03). In the alemtuzumab 24 mg per day group, the results showed statistically significant differences in reducing relapses (RR 0.38, 95% CI 0.23 to 0.62), preventing disease progression (RR 0.42, 95% CI 0.21 to 0.84) and the changes of EDSS score (MD -0.83, 95% CI -1.17 to -0.49) after 36 months' follow-up.All three trials reported adverse events and serious adverse events. There was no statistically significant difference in the number of participants with at least one adverse event (RR 1.03, 95% CI 0.97 to 1.08) and the number of participants who experienced serious adverse events (RR 1.03, 95% CI 0.83 to 4.54). There is low- to moderate-quality evidence that annual intravenous cycles of alemtuzumab at a dose of 12 mg per day or 24 mg per day reduces the proportion of participants with relapses, disease progression, change of EDSS score and developing new T2 lesions on MRI over 24 to 36 months in comparison with subcutaneous IFN beta-1a 44 μg three times per week.Alemtuzumab appeared to be relatively well tolerated. The most frequently reported adverse events were infusion-associated reactions, infections and autoimmune events. The use of alemtuzumab requires careful monitoring so that potentially serious adverse effects can be treated early and effectively.