Take-home message: The advent of gene therapy poses a new area of drug development for inherited and acquires ocular disorders.
New York—Ophthalmologists are about to get a new tool to treat a broad range of inherited and acquired ocular disorders.
Gene therapy could be approved as early as 2016 or 2017 to treat inherited disorders such as Leber’s congenital amaurosis (LCA) and retinitis pigmentosa (RP). Gene therapies for acquired disorders, such as diabetic retinitis and neovascular age-related macular degeneration, could follow in short order.
“Gene therapy is already a reality,” said Szilárd Kiss, MD, director of clinical research and associate professor of ophthalmology, Weill Cornell Medical College, New York. “The first gene therapy was approved in the European Union (EU) in 2013. The eye is a unique space, small and confined with well-defined genetic disorders that can be treated with a single protein delivered using a non-replicating viral vector.”
Dr. Kiss explored the coming upheaval in ocular disease treatment. Human gene therapy trials have been carried out at more than a dozen different sites involving more than 270 eyes. Researchers have reported no serious adverse events associated with the viral vectors and some significant success in treating inherited conditions such as LCA and RP.
The concept behind gene therapy is straightforward: deliver a gene that is designed to produce a therapeutic protein. In the case of Glybera, the gene therapy approved by the EU, a viral vector delivers a gene that produces a protein to treat lipoprotein lipase deficiency. In the case of LCA, a genetically modified adeno-associated virus (AAV) delivers a gene that produces a missing protein responsible for the disease.
One form of LCA is caused by a mutation to the RPE65 gene, resulting in childhood blindness. RPE65 is expressed in the retinal pigment epithelium, which plays a role in the development and maintenance of photoreceptors. The gene also encodes a protein that helps to convert light striking the retina into electrical signals transmitted by the optic nerve. Lack of the protein disrupts the visual cycle, resulting in progressive visual impairment and ultimately to blindness.