Advance in Research on Treatment for Retinitis Pigmentosa—Knockdown & Replacement of Rhodopsin Gene in Dog Model

The last year has seen milestones in the gene therapy field, with FDA approvals to treat cancer and an inherited blinding disorder. New findings from a team led by University of Pennsylvania vision scientists, who have in the past taken gene therapies into clinical trials, are proving successful, this time treating a form of retinitis pigmentosa, a disease that progressively robs people of their night and peripheral vision before blindness develops. The researchers, from Penn's School of Veterinary Medicine and Perelman School of Medicine, in collaboration with University of Florida scientists, developed a therapy that effectively eliminates the abnormal copy of rhodopsin, a light-sensing molecule, and then restores it with a healthy copy of the protein. This knockdown and replacement approach preserved the retina's light-sensing photoreceptor cells in affected dogs, which can develop a very similar disease to affected humans. What's more, the scientists accomplished this using a single viral vector (AAV) to co-deliver the genetic material needed to achieve both the knockdown and replacement. Though more than 150 different mutations in rhodopsin have been identified to cause retinitis pigmentosa, this approach is intended to work regardless of the mutation or the mechanism by which rod photoreceptor cells, those responsible for vision in dim light, die. That means that a large percentage of patients with rhodopsin autosomal dominant retinitis pigmentosa could benefit if the therapy is found to be safe and effective in people. "It's a one treatment fits all," says Dr. William A. Beltran, Professor of Ophthalmology and Director of the Division of Experimental Retinal Therapies at Penn Vet and co-lead author of the study, which was published online on August 20, 2018 in PNAS.
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