A research team based at the Rotterdam Eye Hospital, the University of Groningen and University Eye Clinic, Maastricht, has reported that idebenone (known as Raxone), for the treatment of Leber’s Hereditary Optic Neuropathy (LHON), may help to restore or maintain visual function among a national cohort of patients in the Netherlands. However, the authors of the study also stated that “whether this effect will persist is still unknown. Thinning of retinal neural tissue appears to be permanent”. The treatment, approved in 2014 in the Netherlands, introduced a synthetic analog of co-enzyme Q10, with an oral medication originally authorized at a daily dose of 900 mg for the treatment of visual impairment in LHON adolescent and adult patients.
LHON is a rare progressive disease with an estimated European prevalence of between 1 in 30,000 and 1 in 50,000 patients, it has a a peak age of onset between 15 and 35 years, and a large male predominance. Over >90% of LHON patients carry one of three pathogenic mutations in their mtDNA causing a defect in the complex I subunit of the mitochondrial respiratory chain, causing a progressive loss of visual acuity and blindness. These three prevalent mtDNA point mutations include m.3460G>A (MT-ND1), m.11778G>A (MT-ND4) and m.14484T>C (MT-ND6). Of these, m.11778G>A is considered the most common mutation worldwide.
In the Dutch cohort of patients with LHON treated with idebenone, the study assessed 72 patients with 33.0 years ±21.6, predominantly 74% male. Treatment duration was 23.8 ± 14.4 (mean ± SD) months and the outcome war reported on visual function and on thickness of the retinal ganglion cell layer. The researchers reported that a positive response, (defined as either a clinically relevant recovery (CRR) outcome, or a clinically relevant stabilization (CRS)) occurred in 53% and 11% of the patients, respectively. The magnitude of CRR was 0.41 ± 1.54 logMAR and CRR of visual acuity is associated with recovery of colour discrimination. The researchers also reported that thickness of both the ganglion cell complex (GCC) and the retinal nerve fibre layer (RNFL) is irreversibly reduced. Commenting on their analyses, the researchers stated that, “In spite of the poor consistency among studies of the efficacy of idebenone treatment for LHON and among natural history studies, it is concluded that treatment may enhance the proportion of patients with some degree of (maintained or recovered) visual function. Whether these structural changes have any bearing on the prognosis of visual function, or whether the beneficial effect of idebenone will be preserved over a longer period of time, remains, as yet, to be elucidated”.