Benefits Of Gene Therapy For Blindness May Fade, Study Shows

A new study has shown that gene therapy can help to temporarily improve eyesight in patients who are suffering from Leber congenital amaurosis (LCA), an inherited disorder that results in vision loss beginning in childhood.

However, the improvements aren't quite permanent. They found that they began to subside after one to three years, according to the National Eye Institute.

"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, in a news release. "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."

Statistics show that about 10 percent of patients dealing with LCA also have a mutated form of the gene RPE65 that's responsible for the production of a protein found in the retinal pigment epithelium; this nourishes the light sensors found in the retina.

During the study, researchers looked at 15 people with LCA who received retinal injections of a benign virus that was engineered to carry healthy RPE65 genes.

Four patients in particular started to rely on an area of the retina near where the injection had been made during the study, specifically using the area to see letters, fine details and photoreceptor-rich fovea.

The findings showed how the photoreceptors in treated patients continued to die at the same rate they typically did in LCA progression, which may explain why the benefits were only 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," concluded 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."