The Committee considered the advantages and disadvantages of alemtuzumab treatment. The clinical specialists described advantages to alemtuzumab treatment, including that it is highly effective, does not cause the flu-like symptoms associated with beta interferons, and does not need to be discontinued by patients planning a pregnancy, although the Committee was aware that effective contraceptive measures should be taken when receiving alemtuzumab and for 4 months following a course of treatment according to the summary of product characteristics. This was seen as important, because multiple sclerosis affects women and men during the years when they are most likely to have children, and all other multiple sclerosis treatments, according to their summary of product characteristics, must be stopped for a person to have children. The clinical specialists explained that the main disadvantages of alemtuzumab treatment are the possible serious adverse effects observed during the trials, including idiopathic thrombocytopenic purpura, kidney disease or failure, thyroid disease and death. The clinical specialists stated that thyroid disease is the most common complication, affecting one-third of patients with multiple sclerosis treated with alemtuzumab. In response to a comment made by a consultee that patients treated with alemtuzumab were at risk for papillary thyroid cancer, a clinical specialist suggested that this could be related to increased detection following routine screening as required by the marketing authorisation for alemtuzumab. The clinical specialists and the manufacturer explained that patients need monthly platelet and white cell counts and quarterly assessment of thyroid and renal function for 4 years after the last treatment, and that patients are monitored even more often than this immediately after treatment with alemtuzumab. The clinical specialists stated that alemtuzumab permanently changes a person's immune system because it alters the numbers, proportions and properties of some lymphocyte subsets, and acknowledged that ongoing monthly monitoring might be an obstacle for some patients, particularly for those who feel well. The Committee expressed concern about the methods used to ensure that people treated with alemtuzumab would comply with monitoring requirements. The Committee heard from the clinical specialists that there are standard monitoring systems in place at the specialist centres that administer alemtuzumab and patients are contacted by a variety of methods if they miss a monthly monitoring visit. The Committee was aware that even when adverse events related to alemtuzumab were identified during regular monitoring, there could still be problems with follow-up actions when the results are received. The clinical specialists commented that idiopathic thrombocytopenic purpura associated with alemtuzumab responds to treatment with corticosteroids and immunoglobulin G, and patients would be unlikely to need treatment with thrombopoietin agonists. The clinical specialists and patient experts acknowledged the risk of renal disease for which some patients need renal replacement therapy but stated that people with active relapsing–remitting multiple sclerosis may be willing to accept the risks of serious adverse events associated with alemtuzumab treatment, because the potential benefits to quality of life are considerable. The clinical specialists acknowledged uncertainty about how prior treatment with alemtuzumab might change the adverse event profile of other monoclonal antibodies used for the treatment of multiple sclerosis, such as natalizumab. The Committee concluded that alemtuzumab is associated with significant benefits, but also significant harms, that some people with active relapsing–remitting multiple sclerosis are willing to accept the disadvantages of alemtuzumab treatment, and that adhering to the recommended monitoring schedule is important.