To determine whether eculizumab’s beneficial effect in reducing relapse risk in patients with neuromyelitis optica spectrum disorder (NMOSD) is associated with time since diagnosis, relapse history, disability burden or prior immunosuppressant therapy (IST) use, based on data from the phase 3 trial PREVENT (NCT01892345).

Antibodies to the aquaporin-4 (AQP4) water channel in NMOSD are reported to trigger the complement cascade, which is implicated in neuronal injury. The terminal complement inhibitor eculizumab is the first treatment approved for use in patients with AQP4-immunoglobulin G-positive NMOSD, based on PREVENT data.

In PREVENT, patients received eculizumab (maintenance dose, 1200 mg/2 weeks) or placebo, with stable-dose concomitant IST (except rituximab and mitoxantrone) permitted. PREVENT was not powered for subgroup analyses; post hoc descriptive analysis was performed on subgroups defined by time since diagnosis, total number of historical relapses, baseline Expanded Disability Status Scale (EDSS) score and prior IST use.

The proportions of patients experiencing an adjudicated relapse were lower with eculizumab than with placebo in all subgroups. Proportions for eculizumab and placebo, respectively, were: 2/31 versus 6/12 for < 1 year since diagnosis and 1/65 versus 14/35 for ≥ 1 year since diagnosis; 1/39 versus 10/24 for 2–4 historical relapses and 2/57 versus 10/23 for ≥ 5 historical relapses; 0/14 versus 3/6 for baseline EDSS scores ≤ 2.0 and 3/82 versus 17/41 for baseline EDSS scores ≥ 2.5 to ≤ 7.0; 0/15 versus 2/5 for no prior IST use (except corticosteroids alone) and 3/81 versus 18/42 for prior IST use. Relapse risk reductions were consistent and statistically significant in all subgroups.

The data from this post hoc subgroup analysis suggest that eculizumab reduced relapse risk in PREVENT compared with placebo, regardless of time since NMOSD diagnosis, relapse history, disability burden or prior IST use.