Anti-IL-6 Therapies for Neuromyelitis Optica Spectrum Disorders: A Systematic Review of Safety and Efficacy

BACKGROUND: Neuromyelitis Optica Spectrum Disorder (NMOSD) is a chronic autoimmune disease of the central nervous system that causes recurrent attacks of optic neuritis, myelitis, and brainstem symptoms, resulting in severe neurological disability. Preventive treatment with immunosuppressive agents reduces relapse rate and improves long-term prognosis. In recent years, the potential therapeutical effect of new agents has been investigated. Two of these, the anti-interleukin 6 (IL-6) agents tocilizumab and satralizumab, have been studied in active NMOSD. OBJECTIVE: To systematically review the current data regarding the efficacy and safety of anti-IL-6 agents in NMOSD. RESULTS: Fourteen case reports and 5 case series of intravenous tocilizumab have shown beneficial clinical and paraclinical effects compared to commonly used therapies, and another case series of subcutaneous tocilizumab has shown it is as effective as the IV formulation. A phase 2 comparative trial has shown tocilizumab IV to be more effective than azathioprine for relapse prevention. A phase 3 trial of subcutaneous satralizumab versus placebo, has shown a lower risk of relapse in the sartralizumab-treated group, both as add-on therapy to stable immunosuppressant and as monotherapy. Tocilizumab also reduced pain severity in two trials and fatigue scores in one trial, but satralizumab did not significantly improve pain and fatigue. Adverse events with both agents were relatively mild and comparable to placebo and azathioprine. CONCLUSION: The anti-Il-6 agents tocilizumab and satralizumab show promising results in active NMOSD. Further randomized, larger-scale trials are needed to better define the role of these agents in the growing arsenal of NMOSD treatments.