Gene Therapy One Year Later: Patients Healthy and Maintain Early Visual Improvement
News Aug 14, 2009
Three young adults who received gene therapy for a blinding eye condition remained healthy and maintained previous visual gains one year later, according to an August online report in Human Gene Therapy. One patient also noticed a visual improvement that helped her perform daily tasks, which scientists describe in an Aug. 13 letter to the editor in the New England Journal of Medicine.
These findings have emerged from a phase I clinical trial supported by the National Eye Institute (NEI) at the National Institutes of Health, and conducted by researchers at the University of Pennsylvania, Philadelphia, and the University of Florida, Gainesville.
This is said to be the first study that reports the one-year safety and effectiveness of successful gene therapy for a form of Leber congenital amaurosis (LCA), a currently untreatable hereditary condition that causes severe vision loss and blindness in infants and children.
"These results are very significant because they represent one of the first steps toward the clinical use of gene therapy for an inherited form of blindness," said NEI director Paul A. Sieving, M.D., Ph.D. "I anticipate that it is only a matter of time before similar techniques will be applied to other genetic diseases affecting vision."
The three patients in the study; aged 22, 24 and 25; have been legally blind since birth due to a specific form of LCA caused by mutations in the RPE65 gene. The protein made by this gene is a crucial component of the visual cycle. The RPE65 protein is necessary for the production of a retina-specific form of vitamin A that is required for the light-sensitive photoreceptor cells to function. Mutations in the RPE65 gene prevent this production, which halts the visual cycle and blocks vision.
The RPE65 disease offers an opportunity for treatment in that it leaves some photoreceptors intact. In this study, researchers pinpointed an area of intact photoreceptors in the retina of each patient. They injected healthy copies of the RPE65 gene under the retina in this area in an attempt to repair the visual cycle.
Researchers will continue to follow these patients over the next several years to monitor safety and to learn whether the visual benefits remain. This ongoing phase I trial also includes additional groups of LCA patients - children as well as adults - who are receiving different doses of the RPE65 gene therapy.