A Michigan State University veterinary ophthalmologist has modified a gene therapy that reverses blindness in dogs that have a certain form of a disease known as progressive retinal atrophy, or PRA, and is now looking to advance the treatment for human use.
In an earlier study, the treatment on dogs had a 100 percent success rate in helping them restore their night vision, as well as stop them from losing their daytime vision. The progressive disease, which is similar to a disease in humans, often leads to night blindness, followed by a loss of peripheral vision and eventually total blindness.
Simon Petersen-Jones in the College of Veterinary Medicine has received a five-year, $8.2 million grant from the National Institutes of Health to further the therapy for people who have a type of retinitis pigmentosa, or RP.
RP is one of the most common inherited diseases of the retina and is estimated to affect about one in every 3,500 people in the United States and in Europe.
PRA is an inherited condition in dogs that results from mutations in the same genes that cause RP. The retina - a thin tissue that lines the back of the eye - has cells that are light sensitive. These cells, called photoreceptors, convert light into signals, which are sent to the brain and give us information about visual images.
With RP, the photoreceptors, rods and cones of the eye are affected and progressively die.
"We know the disease in dogs looks like the disease in humans and progresses in a similar way," Petersen-Jones said, who is leading the project and is a Myers-Dunlap Endowed Chair in Canine Health. "We were able to identify a shared gene and create a new therapy that effectively helped dogs see again. This new grant will allow us to build on our primary studies in preparation for an eventual clinical trial in human patients."
Petersen-Jones and his team were the first to show that some dogs with PRA have a mutation involving a gene called cyclic nucleotide-gated channel b 1, or CNGB1, which also causes a form of RP in humans.
Their approach, which was based on a gene therapy that's been used to treat other inherited retinal degenerations, introduced a normal copy of the CNGB1 gene into the retina of affected dogs, restoring normal function and vision.
"The therapy works extremely well and we hope that this work will lead to an effective treatment for humans," Petersen-Jones said.
The team looks to obtain Food and Drug Administration approval to test the gene therapy as an investigational new drug.
Two groups of patients with RP that have the CNGB1 gene mutations, one in the United States and one in Europe, also will be enrolled as part of the project. During this time, researchers will track progressive changes in the patients' retinas that later will be used as baseline measurements to assess the effectiveness of the treatment when it enters a clinical trial.
"We have assembled an outstanding international team of top scientists and clinicians who will be able to collaborate to develop an effective treatment for this form of RP," Petersen-Jones said.