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In experiments with rats, pigs and monkeys, Johns Hopkins Medicine researchers have developed a way to deliver sight-saving gene therapy to the retina. If proved safe and effective in humans, the technique could provide a new, more permanent therapeutic option for patients with common diseases such as wet age-related macular degeneration (AMD), and it could potentially replace defective genes in patients with inherited retinal disease.
The new approach, described in the Aug. 13 issue of The Journal of Clinical Investigation, uses a small needle to inject harmless, genetically engineered viruses into the space between the white of the eye and the eye's vascular layer, called the suprachoroidal space. From there, the virus can spread throughout the eye to deliver therapeutic genes to cells in the retina. The gene therapy approach currently used to treat Leber congenital amaurosis, an inherited eye disorder, involves a surgical procedure to inject the gene-carrying virus under the retina. This procedure carries a high risk of patients developing cataracts, and a low but significant risk of retinal detachment and other vision-threatening complications.
Though only tested in animals up to this point, the new suprachoroidal injection technique is less invasive because it does not involve detaching the retina, and theoretically, it could be done on an outpatient basis, marking a major step toward making permanent vision-saving gene therapies safer and more accessible. A subretinal injection gene therapy approach is also being tested in clinical trials for age-related macular degeneration, which is among the leading causes of irreversible and disabling vision loss in people over age 50, according to the National Eye Institute. An estimated 10 million Americans have age-related macular degeneration. In the disease's more common "wet" form, abnormal blood vessels grow under the retina and leak vision-blocking fluids into the eye. The growth and leakage of the abnormal blood vessels is caused by excess production of a cell signal called vascular endothelial growth factor (VEGF).
Currently, eye specialists can stave off vision loss by injecting a protein into the eye that blocks VEGF, but these treatments have a limited life span, so patients must return to the clinic every four to six weeks for more injections to maintain their vision. Missed appointments can allow the abnormal blood vessels to grow, causing further vision loss. "We find that repeated treatments, although effective, can be hard for patients to keep up with, and over time, they lose vision," says Campochiaro. However, a gene therapy could turn each cell in the retina into a little pharmaceutical factory that constantly produces anti-VEGF proteins, thereby continuously maintaining vision without repeated injections.....
Study published on August 13 in the Journal of Clinical Investigation:
https://doi.org/10.1172/JCI129085
