MX is considered an immune-mediated chronic disorder of the central nervous system (CNS), characterized by multiple areas of inflammation and demyelination. Several drugs such as steroids as well as immunomodulant and immunosuppressive agents have been used to treat the disease course. Among them, MX, an immunosuppressive agent widely used for treatment of breast cancer and leukaemia, has been tested in MS individuals. Two hundred seventy-five articles were identified by the search strategy up to May 2013. Three trials contributed to this review, comprising a total of 221 participants. Data show that MX was moderately effective in reducing the risk of MS progression and the frequency of relapses in short-term follow-up (up to two years) of patients affected by worsening relapsing-remitting MS (RRMS), progressive relapsing MS (PRMS) and secondary progressive MS (SPMS). However, caution must be exercised when interpreting these results because of the heterogeneous characteristics and quality of the included trials, which are different in terms of treatment schedules and types of enrolled patients.
The most frequent adverse effects were nausea and vomiting, alopecia, urinary tract infections and transitory leucopenia; 35% of MX-treated female participants developed transitory amenorrhoea, and almost 15% developed a persistent amenorrhoea which was still present at the end of the follow-up period. Data from studies with longer follow-up and out of included trials have raised concerns about cardiotoxicity and acute leukaemias, occurring in about 12% and 0.8% of MX-treated patients respectively.
For these reasons, MX treatment should be limited to patients with worsening RRMS and SPMS after a careful assessment of the individual patients’ risk and benefit profiles, also considering the present availability of alternative therapies with less severe adverse events. Moreover, MX-treated patients need to be followed-up after the end of treatment to control the risk of serious adverse events.