Efficacy of Gene Therapy in Restoring Vision in Leber's Congenital Amaurosis
Leber’s congenital amaurosis (LCA) is a catastrophic hereditary disease caused by mutations in 14 genes. One of these mutations in RPE65 gene causes 6% of LCA cases. The RPE65 gene is needed for regeneration of visual pigment. Mutation in RPE65 gene results in severe visual impairment, retinal degeneration and blindness. Animal research and human clinical trials of gene therapy using recombinant adeno-associated virus (AAV) vectors have demonstrated safe and efficacious results.
This article reviews current knowledge of the genetic causes of LCA and the development of gene therapy. The efficacy as well as the limitations of this form of treatment are evaluated in detail and recommendations are made for the future directions of gene therapy for LCA.
The literature search involved searching databases including “Web of Science,” “Science Direct,” “Academic Search Complete,” “Combining keywords “Leber’s congenital amaurosis” AND “Gene therapy” and restricting dates to 1985 – 2014. Critically evaluating, mostly primary journal articles reporting animal study results and/or human clinical trial data. Secondary sources included a few review articles and clinicaltrials.gov
The data from pre-clinical and clinical trials indicates that gene therapy for LCA is safe and effective with significant visual improvements that remain stable over time. However evidence shows that photoreceptor degeneration continues progressively. Combinational therapies that deliver RPE65 gene in addition to anti-apoptotic, anti-oxidants and neurotrophic factors will improve photoreceptor survival long term. New challenges exist in applying gene therapy to clinical settings, improving vector systems that deliver genes to the retina without the need for high risk surgery. Also improved control of gene expression to maintain therapeutic levels without toxicity.
Gene therapy offers excellent potential in restoring vision in Leber’s congenital amaurosis. Further research and development is required to make gene therapy a clinical reality for the many sufferers worldwide.