A new study found gene therapy temporarily improved eyesight in patients suffering from Leber congenital amaurosis (LCA), which is an inherited disorder that causes vision loss starting in childhood.
Despite the initial success, the improvements in vision and retina sensitivity peaked one to three years after treatment and then subsided, the National Eye Institute reported.
"Gene therapy for LCA demonstrated we could improve vision in previously untreatable and incurable retinal conditions," said Samuel G. Jacobson, who led the clinical trial at the University of Pennsylvania's Scheie Eye Institute, Philadelphia. "Even though the current version of the therapy doesn't appear to be the permanent treatment we were hoping for, the gain in knowledge about the time course of efficacy is an opportunity to improve the therapy so that the restored vision can be sustained for longer durations in patients."
About 10 percent of patients suffering from LCA have a mutated form of the gene RPE65, which is responsible for the production of a protein found in the retinal pigment epithelium, which nourishes light sensors in the retina.To make their findings, the researchers looked at 15 people with LCA who received retinal injections of a benign virus that was engineered to carry healthy RPE65 genes.
"Within days of the injections, some patients reported increases in their ability to see dim lights they had never seen before. It was remarkable for us to get this feedback that things were indeed changing positively," Dr. Jacobson said.
The researchers observed four of the patients started to rely on an area of the retina near the injections site for seeing letters, fine details are usually seen through the photoreceptor-rich fovea. The findings also showed photoreceptors in the treated patients continued to die at the same rate as they did in typical LCA progression, explaining why the benefits were only seen in the short-term.
"We now have six years of data showing that a gene therapy approach is safe and that it successfully improves vision in people with this blinding disease," said Paul A. Sieving, director of NEI. "As with any application of a novel therapy, it now needs to be fine-tuned. More research is needed to understand the underlying biology and how we can preserve or restore photoreceptors for a lifetime. Restoring vision is at the heart of the NEI's Audacious Goals Initiative, an effort to strategically fund research aimed at developing the knowledge and technology to make this goal a reality."
The findings were published in a recent edition of the New England Journal of Medicine.
