To examine the long-term efficacy and safety of eculizumab monotherapy in patients with aquaporin-4 immunoglobulin G-positive (AQP4+) neuromyelitis optica spectrum disorder (NMOSD) during PREVENT and/or its ongoing open-label extension (OLE).

In PREVENT, eculizumab was well tolerated and significantly reduced relapse risk versus placebo in patients with AQP4+ NMOSD with or without concomitant immunosuppressive therapy (IST).

During PREVENT (NCT01892345) and its OLE (NCT02003144), adults with AQP4+ NMOSD received eculizumab (maintenance dose, 1200 mg/2 weeks) or placebo (PREVENT only) with or without concomitant IST. Relapses, hospitalizations, IST changes and adverse events (AEs) with eculizumab monotherapy (PREVENT and its OLE; interim data cut-off, July 31, 2019) or with placebo alone (PREVENT) were descriptively analyzed post hoc.

During PREVENT and/or its OLE, 33 patients received eculizumab monotherapy for 85.3 patient-years (PY). Adjudicated relapses occurred in 1/33 patients (annualized relapse rate, 0.012; 95% confidence interval [CI]: 0.002–0.082) versus 7/13 with placebo alone in PREVENT. At 192 weeks, 96.2% of patients receiving eculizumab monotherapy were relapse-free (95% CI: 0.757–0.994) versus 93.8% of patients receiving eculizumab with concomitant IST (95% CI: 0.867–0.972). No patients receiving eculizumab monotherapy required hospitalization for a relapse and none started an IST. The treatment-related AE rate with eculizumab monotherapy in PREVENT and/or its OLE was similar to that with placebo alone in PREVENT (181.0 versus 186.0 events/100 PY), the infection rate was similar between these groups (174.1 versus 186.0 events/100 PY), and the treatment-related serious AE rate was lower with eculizumab monotherapy than with placebo alone (5.7 versus 23.3 events/100 PY). No meningococcal infections or deaths occurred among these patients.

A very high proportion of patients who had experienced 1–2 relapses in the pre-study year remained relapse-free through 192 weeks of eculizumab monotherapy. Long-term eculizumab monotherapy was well tolerated and effective in reducing relapse risk in AQP4+ NMOSD.