Long‐term efficacy and safety of idebenone in patients with Leber's hereditary optic neuropathy (LHON) in the chronic phase: Results from the prospective, natural history‐controlled LEROS study

Purpose: LHON is a rare mitochondrial disorder which results in bilateral vision loss. Idebenone is approved in Europe for the treatment of LHON, but relatively little controlled data exists to support use in chronic patients. Here, we report primary results from LEROS, a Phase 4, externally controlled interventional study in patients with chronic LHON (1 to ≤5 years since onset) treated with idebenone for up to 24 months. Methods: Patients with LHON onset ≤5 years prior were enrolled and stratified by time since onset: subacute/dynamic (≤1 year) and chronic (>1 but ≤5 years). Visual acuity (VA) outcomes from 181 patients, treated for up to 24 months were compared to retrospective data from an external natural history (NH) cohort (N = 372) matched by time since onset. Outcome measures, from baseline, were clinically relevant recovery (CRR): improvement from ‘off‐chart’ VA to at least 1.6 logMAR, or a ≥0.2 logMAR improvement if already ‘on‐chart’; clinically relevant stabilization (CRS): maintenance of VA