Successful arrest of photoreceptor and vision loss expands the therapeutic window of retinal gene therapy to later stages of disease

Corrective gene therapies for inherited retinal degenerations are being developed with the expectation that even patients in later stages of the disease will benefit from such intervention. Evidence in animal models for a rescue after the onset of photoreceptor loss is scarce, and recent results from patients enrolled in two of the gene therapy clinical trials for a congenital form of blindness (RPE65-LCA) show that, despite transient improvement in visual function, photoreceptor cell death remains unabated. Here we show in a canine model for a common and severe form of X-linked retinal degeneration that gene therapy successfully stops photoreceptor cell death, improves the structure of retinal cells, and prevents vision loss for more than 2 y.