Jul 10, 2023

Using gene therapy to treat genetic eye disease aniridia

In 2020, Fighting Blindness Canada awarded Dr. Elizabeth Simpson at the University of British Columbia a research grant of $297,000 to support the development of a potential gene therapy for the inherited eye disease, aniridia. As this research grant comes to an end in 2023, we are happy to share how this investment has helped bring hope for individuals with aniridia and other eye diseases.

What is Aniridia

Aniridia is an inherited eye disease where the iris, the coloured part of the eye, is partially or completely absent. Individuals with aniridia usually have low vision from birth and develop glaucoma and cataracts, which can lead to blindness. Most cases are caused by a mutation in the PAX6 gene and while current treatments may slow the progression, there are no cures or treatments to maintain vision long-term.

With Fighting Blindness Canada funding, Dr. Simpson’s team has been developing a minimally invasive gene therapy for aniridia which they are testing in an animal model.

Gene Therapies for Eye Diseases

Most current gene therapies for inherited eye diseases deliver the new gene directly into the eye, often using a subretinal injection which is a very delicate process. Injecting the gene therapy into the eye, ensures that target cells in the eye receive a large enough dose of the gene therapy, while also reducing the amount of gene therapy that reaches other parts of the body, hopefully reducing the potential for side effects. Dr. Simpson is testing if gene therapy for an eye disease can be delivered without injections into the eye.

Image is of Dr. Elizabeth Simpson

Dr. Simpson’s Project

In this project, Dr. Simpson’s team tested an intravenous injection, which is an injection into a vein directly into the bloodstream, to deliver the gene therapy. Not only is this less invasive than a subretinal injection, but because PAX6 mutations can impact other parts of the body, a treatment that delivers the gene therapy around the body may be able to improve symptoms in multiple parts of the body, including the eye.

Over the course of the research grant, Dr. Simpson’s team produced and tested multiple PAX6 gene therapies in an animal model to identify the optimized approach. This included testing different doses of the gene therapy to identify the highest dose that was safe, and injecting the gene therapy in young and old animals to identify when the treatment might be most effective.

After these experiments, Dr. Simpson was excited to show for the first time using an intravenous injection, that the PAX6 gene therapy was delivered to cells in the retina. Importantly, there was no “toxicity” or negative side effects from the treatment. The delivery of the gene therapy was most efficient in young animals, which is equivalent to a childhood age in humans. Up to five months after injection, Dr. Simpson could show that the PAX6 gene therapy was still present in retinal cells.

The team did not see any strong impact on vision after the gene therapy and they think that a greater number of cells will need to receive the gene therapy for improvement to occur. Dr. Simpson will continue this work hopefully bringing a new gene therapy to a clinical trial in the future.

As more innovative treatments are being developed for eye diseases, it is interesting to see not only gene therapies for more and more genes, but also different and potentially less invasive ways of delivering the therapies. We look forward to seeing where this research goes!

Dr. Simpson’s grant was generously funded by the estate of Doreen Powles.

Learn about more research Fighting Blindness Canada is funding.

Image is of a mother holding her child, smiling, with text overlaid on the image that states, "Your gift brings hope to over 8 million living with a blinding eye disease."

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