|National Eye Institute's Neeraj Agarwal|
Using an AAV vector, a scientific team funded by the NIH has developed a gene therapy that preserved the vision of a group of dogs which share a malfunctioning retinitis pigmentosa GTPase regulator (RPGR) gene. And they believe the same type of treatment will also work in the human eye.
Researchers from the University of Pennsylvania and the University of Florida, Gainesville, reported several key findings from the 2.5-year-long study, which used a viral vector to insert correct copies of the gene into the eye. The therapy appeared to prevent cell death among the animals over at least the length of the study, promising to work for an even longer period. They also determined that the treated canines' eyes retained retinal thickness and that even in dogs at a late stage of the disease they found that the treatment had helped preserve vitally needed photoreceptors. The work was published in the Proceedings of the National Academy of Sciences.
The RPGR gene encodes a protein that plays a big role in maintaining the health of photoreceptors, which converts light into electrical signals that are dispatched to the brain.
A large percentage of people suffering from retinitis pigmentosa share a common mutation that may be corrected by the same gene therapy approach.
"The study shows that a corrective gene can stop the loss of photoreceptors in the retina, and provides good proof of concept for gene therapy at the intermediate stage of the disease, thus widening the therapeutic window," said Neeraj Agarwal, a program director at the National Eye Institute.
About one in every 4,000 people, mostly men, suffer from retinitis pigmentosa. The disease causes night blindness early in life and the progressive loss of the visual field by around the age of 45.
Gene therapy has become an increasingly popular research field in recent years as more and more biotechs jump into it. Spark Therapeutics recently reported a successful late-stage study, which could lead to the first approval for a gene therapy in the U.S.
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