Hope on the Horizon: New Gene Therapy Strategy for a Common Form of Retinitis Pigmentosa

For individuals and families living with inherited retinal diseases (IRDs), particularly those affected by autosomal dominant retinitis pigmentosa (adRP), news of potential new therapies offers a beacon of hope. A study funded by the National Eye Institute (NEI), part of the National Institutes of Health (NIH), reported a novel gene therapy strategy that successfully halted vision loss in a canine model of adRP. This research, published in the Proceedings of the National Academy of Sciences in August 2018, could pave the way for future treatments aimed at slowing or preventing vision deterioration in humans.

Key Findings from the Research

Retinitis pigmentosa (RP) encompasses a group of genetic disorders that cause damage to the retina's light-sensing photoreceptor cells. Rod photoreceptors, crucial for low-light vision, rely on a protein called rhodopsin. In adRP linked to rhodopsin gene mutations, individuals typically have one normal copy of the gene and one mutated copy that produces an abnormal, often toxic, rhodopsin protein. This toxic protein gradually kills rod cells, leading to progressive vision loss over years or decades. Over 150 rhodopsin mutations have been identified as causes of adRP, presenting challenges for therapy development.

The research team, led by William Beltran, D.V.M., Ph.D., from the University of Pennsylvania School of Veterinary Medicine, developed a gene therapy construct. This construct utilizes shRNA (short-hairpin RNA) interference to reduce the rod cells' ability to produce rhodopsin. Gene therapy involves introducing genetic material into cells to address abnormal genes or to produce beneficial proteins. The researchers tested this construct in dogs with a rhodopsin mutation, which, similar to humans with adRP, experience a gradual loss of rod photoreceptors. The therapy successfully reduced rhodopsin production (both mutated and normal) by approximately 98-99 percent in the dogs' retinas. This proof-of-concept demonstrates a potential strategy for one of the most common forms of retinitis pigmentosa.

What This Means for Patients and Families

This study represents an important step forward in understanding and potentially treating adRP. While the findings are from a canine model, they provide valuable insights into a novel therapeutic approach that could one day translate to human patients. The ability to