MYO7A is a large gene that encodes myosin VIIA, a protein that helps maintain stereocilia in the inner ear and the retinal pigment epithelium in the retina. MYO7A gene mutations are responsible for Usher syndrome type 1B, which accounts for more than 50% of all Usher syndrome type 1 cases.
In prior studies, researchers at the Telethon Institute of Genetics and Medicine (TIGEM) and AAVantgarde in Italy demonstrated successful gene therapy replacement of the defective MYO7A with a healthy copy using dual adeno-associated vector (AAV) viral delivery using mice and pigs. To be considered for human clinical trials, this dual AAV8.MYO7A gene therapy treatment must be found safe and effective. Using mouse and primate models, subretinal injections of this treatment were administered in various dosages to determine effectiveness and safety. The dual AAV8.MYO7A treatment demonstrated improved MYO7A gene expression, confirming the gene was delivered to the retina and incorporated into the DNA. There were only minor post-injection alterations that were negligible and inflammation that improved over time. These results reflect a positive risk/benefit ratio and confirm the treatment is safe and effective for testing in human clinical trials.
What this means for Usher syndrome: If this dual AAV8.MYO7A gene therapy treatment is FDA-approved for testing in human clinical trials, USH1B patients may be one step away from a therapy.
