A disease model was developed to understand the long-term benefits of eculizumab in patients with neuromyelitis optica spectrum disorder (NMOSD).

NMOSD is an autoimmune disease of the central nervous system characterized by unpredictable relapses and the accumulation of neurological disability, leading to reduced health-related quality of life (HRQoL). PREVENT, a randomized, double-blind, placebo-controlled, time-to-event trial, found eculizumab to be effective in reducing the risk of a first adjudicated relapse in patients with aquaporin-4 immunoglobulin G-positive NMOSD.

A Markov cohort model was developed using PREVENT data to estimate time to relapse over a 20-year time horizon, under the assumptions that risk of relapse varies by treatment but is constant over time (provided no change in treatment) and time-to-first-relapse curves are relevant for subsequent relapses. PREVENT data were also used to describe HRQoL based on the European Quality of Life 5-Dimension questionnaire (EQ-5D), allowing life years to be converted to quality-adjusted life years (QALYs). Each relapse was associated with both a short-term, temporary and a cumulative, permanent decline in HRQoL. The model assumed that mortality was 7% per year following the first relapse, incidence of long-term disability was 17.5% per relapse (accounting for a cumulative increase with each relapse), and disability related HRQoL data for multiple sclerosis could be used as a proxy for NMOSD.

Using this model, the proportion of patients who remained relapse free at 20 years was greater for eculizumab (66.2%) than placebo (0.0%). Patients receiving eculizumab were also estimated to experience 3.9 fewer relapses, 7.6 additional life years, and 7.7 additional QALYs compared with placebo; benefits associated with eculizumab were consistent across multiple sensitivity and scenario analyses.

The benefits associated with eculizumab in the PREVENT trial were extrapolated over a 20-year time horizon and demonstrated substantial, long-term improvements in clinical outcomes and HRQoL among patients with NMOSD.