After more than 2 decades of recommending an escalating strategy for the treatment of most patients with multiple sclerosis, there has recently been considerable interest in the use of high-efficacy therapies in the early stage of the disease. Early intervention with induction/high-efficacy disease-modifying therapy may have the best risk-benefit profile for patients with relapsing-remitting multiple sclerosis who are young and have active disease, numerous focal T2 lesions on spinal and brain magnetic resonance imaging, and no irreversible disability. Although we have no curative treatment, at least seven classes of high-efficacy drugs are available, with two main strategies. The first strategy involves the use of high-efficacy drugs (e.g., natalizumab, sphingosine 1-phosphate receptor modulators, or anti-CD20 drugs) to achieve sustained immunosuppression. These can be used as a first-line therapy in many countries. The second strategy entails the use of one of the induction drugs (short-term use of mitoxantrone, alemtuzumab, cladribine, or autologous hematopoietic stem cell transplant) that are mainly recommended as a second-line or third-line treatment in patients with very active or aggressive multiple sclerosis disease. Early sustained immunosuppression exposes patients to heightened risks of infection and cancer proportionate to cumulative exposure, and induction drugs expose patients to similar risks during the initial post-treatment period, although these risks decrease over time. Their initial potential safety risks should now be revisited, taking account of long-term data and some major changes in their regimens: natalizumab with the long-term monitoring of John Cunningham virus; use of monthly courses of mitoxantrone with maximum cumulative doses of 36-72 mg/m2, followed by a safer disease-modifying drug; cladribine with only 2-weekly treatment courses required in years 1 and 2 and no systematic treatment for the following 2 years; alemtuzumab, whose safety and clinical impacts have now been documented for more than 6 years after the last infusion; and autologous haematopoietic stem cell transplant, which dramatically reduces transplantation-related mortality with a new regimen and guidelines. Escalation and induction/high-efficacy treatments need rigorous magnetic resonance imaging monitoring. Monitoring over the first few years, using the MAGNIMS score or American Academy of Neurology guidelines, considerably improves prediction accuracy and facilitates the selection of patients with relapsing-remitting multiple sclerosis requiring aggressive treatment.
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