The first clinical trial using gene therapy to treat a vision disorder has begun, involving 12 patients with an inherited condition that causes childhood blindness. The treatment, which is taking place in London, UK, hopes to restore vision in patients who have a genetic defect that causes degeneration of the retina.Robin Ali at Moorfields Eye Hospital in London and colleagues are treating adults and children with Leber’s congenital amaurosis (LCA), caused by an abnormality in the RPE65 gene. This gene is important in recycling retinol, a molecule that helps the retina detect light. People with LCA usually lose vision from infancy. Ali's team are inserting healthy copies of RPE65 into cells in the retina, using a viral vector. Previously, dogs with LCA have had their vision restored in this way, allowing them to walk through a maze for the first time without difficulty.

Leonard Seymour, who leads the Gene Delivery Group at the University of Oxford in the UK, and is not involved in the current trial, says the retina is a good place for gene therapy because it can be accessed by injection to overcome the problem of delivery. "The retina is also good because it is relatively immune-privileged, meaning that the vector (in this case a virus) should not be neutralised immediately upon administration," he says.

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