Abstract: Three RCTs (1713 participants) fulfilled the selection criteria and we included them in the review. All three trials compared alemtuzumab versus subcutaneous interferon beta-1a for patients with relapsing–remitting MS. Patients were treatment-naive in the CARE-MS and CAMMS223 studies. The CARE-MS II study included patients with at least one relapse while being treated with interferon beta or glatiramer acetate. Alemtuzumab was given for 12 or 24 months; for some outcomes, the follow-up period reached 36 months. The regimens were (a) 12 mg or 24 mg per day administered intravenously, once a day for five consecutive days at month 0 and 12 or (b) 24 mg per day, intravenously, once a day for three consecutive days at month 12 and 24. The patients in the other arm of the trials received interferon beta-1a 44 μg subcutaneously three times weekly after dose titration. At 24 months, alemtuzumab 12 mg was associated with: (a) higher relapse-free survival (hazard ratio (HR) 0.50, 95% CI 0.41 to 0.60; 1248 participants, two studies, moderate quality evidence); (b) higher sustained disease progression-free survival (HR 0.62, 95% CI 0.44 to 0.87; 1191 participants; two studies; moderate quality evidence); (c) a slightly higher number of participants with at least one adverse event (RR 1.04, 95% CI 1.01 to 1.06; 1248 participants; two studies; moderate quality evidence); (d) a lower number of participants with new or enlarging T2-hyperintense lesions on magnetic resonance imaging (MRI) (RR 0.74, 95% CI 0.59 to 0.91; 1238 participants; two studies; I2 = 80%); and (e) a lower number of dropouts (RR 0.31, 95% CI 0.23 to 0.41; 1248 participants; two studies, I2 = 29%; low quality evidence). At 36 months, alemtuzumab 24 mg was associated with: (a) higher relapse-free survival (45 versus 17; HR 0.21, 95% CI 0.11 to 0.40; one study; 221 participants); (b) a higher sustained disease progression-free survival (HR 0.33, 95% CI 0.16 to 0.69; one study; 221 participants); and (c) no statistical difference in the rate of participants with at least one adverse event. We did not find any study that reported any of the following outcomes: rate of participants free of clinical disease activity, quality of life, fatigue or change in the numbers of MRI T2- and T1-weighted lesions after treatment. It was not possible to perform subgroup analyses according to disease type and disability at baseline due to lack of data. In patients with relapsing-remitting MS, alemtuzumab 12 mg was better than subcutaneous interferon beta-1a for the following outcomes assessed at 24 months: relapse-free survival, sustained disease progression-free survival, number of participants with at least one adverse event and number of participants with new or enlarging T2-hyperintense lesions on MRI. The quality of the evidence for these results was low to moderate. Alemtuzumab 24 mg seemed to be better than subcutaneous interferon beta-1a for relapse-free survival and sustained disease progression-free survival, at 36 months. More randomised clinical trials are needed to evaluate the effects of alemtuzumab on other forms of MS and compared with other therapeutic options. These new studies should assess additional relevant outcomes such as the rate of participants free of clinical disease activity, quality of life, fatigue and adverse events (individual rates, serious adverse events and long-term adverse events). Moreover, these new studies should evaluate other doses and durations of alemtuzumab course.

Plain-language summary: We found three studies (including 1713 participants) that fulfilled the review selection criteria. All studies compared alemtuzumab versus subcutaneous interferon beta-1a for people with relapsing–remitting MS. In two of the studies (CARE-MS and CAMMS223) the participants were being treated for the first time (treatment-naive). The third study (CARE-MS II) included participants with at least one relapse while being treated with interferon beta or glatiramer acetate for at least six months. The review of these comparative studies found that, compared to subcutaneous interferon beta-1a, alemtuzumab reduces the risk of relapse, improves function and seems not to increase the overall risk of adverse events. Additionally, alemtuzumab reduces the risk of new or enlarging lesions of MS detected using magnetic resonance imaging (MRI). However, there is a lack of information about the effects of alemtuzumab on several patient-related outcomes such as (a) quality of life, (b) the rate of each adverse events (separately) and (c) the frequency of long-term adverse events and serious adverse events. The overall methodological quality of the included studies was moderate to high. However, because of the small number of included studies and the low rate of events, we judged the overall quality of the evidence for the main outcomes as very low to moderate. This means that new studies are likely to have an important impact on our confidence in the estimate of effect and may change the estimate or that we are very uncertain about the estimate.