Timing is everything.
Nearly 20 years ago, gene therapy restored vision to Lancelot, a Briard dog who was born with a blinding disease. This ushered in a period of hope and progress for the field of gene therapy aimed at curing blindness, Penn Today reports.
In 2017 a gene therapy gained approval that improved vision in people with Leber congenital amaurosis (LCA), a rare, inherited form of blindness closely related to the condition seen in Lancelot. It was the first FDA-approved gene therapy for an inherited genetic disease.
The gene therapy has improved vision in patients, but questions remain about how long-lasting these improvements will be and whether degeneration of vision cells have been halted with the therapy.
In a new paper in the journal Molecular Therapy, researchers from the University of Pennsylvania returned to canines to learn more.
This time, they treated dogs at more advanced stages of the disease, when human patients are more likely to be treated. Therapy for dogs when more than 63% of their photoreceptor cells were still present but nonfunctional had great success. The effect of the treatment seemed lifelong, and degeneration was stopped.
But for dogs who had lost more than half of their photoreceptor cells before receiving the treatment, the disease seemed to continue to progress, despite a short-term restoration of sight.
“Earlier work by our group and others had suggested that if you treated the disease at a time when the retina was degenerating, that degeneration continued, in people and in dogs,” said Gustavo D. Aguirre of Penn’s School of Veterinary Medicine. “This was in spite of short-term gains in vision. We wanted to follow up to get details about the extent of retinal degeneration that would still be compatible with a lasting effect.”