Efficacy and safety of tocilizumab treatment in refractory MOG-IgG related optic neuritis

Background: Myelin oligodendrocyte glycoprotein (MOG) IgG related optic neuritis (ON) which manifests as recurrent episodes and severe visual impairment remains a challenging issue in relapse prevention. Tocilizumab (TCZ), a human monoclonal antibody against IL-6R, may be an alternative treatment for the prevention of relapse in refractory MOG-ON patients. Objectives: To investigate the efficacy and safety of Tocilizumab (TCZ) in patients with recurrent myelin oligodendrocyte glycoprotein IgG related optic neuritis (MOG-ON). Design: We conducted an open-label, single-arm, nonrandomized, uncontrolled clinical trial at a tertiary neuro-ophthalmology center between April 1, 2021, and April 1, 2022. Methods: Participants with relapsed MOG-ON, whose disease had been resistant to previous immunotherapies, received tocilizumab as monotherapy or as an add-on therapy and were followed up for at least 12 months. Annual recurrence rate (ARR), best corrected visual acuity (BCVA), and adverse events were recorded for analyses. Result: Ten patients (7 females and 3 males) with relapsed MOG-ON were included with a mean (SD) ages of 28.6 (20.5) years old at disease onset and 30.9 (19.7) years at first TCZ administration, with a mean disease duration of 26.6 (11.3) months. Seven (70%) patients remained relapse-free, and the median (range) ARR dropped significantly from 1.9 (0.4–3.5) to 0.0 (0–4.0) during TCZ treatment ( p = 0.006). Three patients experienced a relapse of ON at 2, 3, and 7 months after TCZ therapy. The median BCVA improved from 2.7 (2.0–3.0) logMAR at the nadir to 0.2 (0–2.0) logMAR at the last follow-up. Adverse effects included transient diarrhea ( n = 1) and upper respiratory infection ( n = 1). Conclusion: This study supports that Tocilizumab therapy, with or without concomitant immunosuppression, is safe and effective in reducing relapses in MOG-ON patients who have failed immunosuppressive therapy or targeted B-cell therapy. Trial registration: This trial is registered with the Chinese Clinical Trial Registry, number ChiCTR2100045273. (URL: https://www.chictr.org.cn/showproj.html?proj=124810 )