I first learned about inherited blinding disorders as a freshman in college, when I got a summer job with Dr. David Birch, a leading scientist who has been studying retinitis pigmentosa (RP) for many years.
At that time, there were no treatments for genetic conditions like RP, which damage the eye’s light-sensing retina and cause progressive vision loss and blindness. Now, after working in this field for many years, it’s exciting to know we are at the cusp of sight-saving treatments for some of these degenerative diseases of the retina, which often appear at an early age.
What’s also exciting–and what many don’t realize–is that OHSU’s Casey Eye Institute is at the epicenter of many of these groundbreaking investigations, particularly in the promising field of gene therapy.
We are conducting more gene therapy trials than any other research center in the world, and are the first to test this novel approach for such inherited diseases as Usher syndrome and Stargardt disease. Usher syndrome is an especially devastating genetic disorder. Not only are patients born with deafness, they lose eyesight from RP as they grow older.
In the coming year, we also plan to launch the world’s first gene therapy studies for achromatopsia, which causes color blindness, daytime blindness and light sensitivity, and x-linked retinoschisis (XLRS), a disease that affects males and leads to retinal detachment and vision loss.
What has brought us to this point is the result of major technological advances and a robust infrastructure at Casey that enables us to recruit, test and treat study patients using cutting-edge approaches.
At the Oregon Retinal Degeneration Center, we’ve developed sophisticated diagnostic techniques that allow us to objectively measure whether the gene medication is working.
These capabilities are critical to a clinical trial’s success.
The human eye is ideal for testing novel treatments like gene therapy because it is accessible, yet segregated from the rest of the body. Moreover, since only one eye is treated, the fellow untreated eye serves as a valuable control. With gene therapy, our goal is to stabilize vision by replacing the targeted, malfunctioning gene with a single application of a healthy version.
The experimental medication is inserted into the eye by way of a non-active virus where healthy copies of the gene are delivered into eye cells. While it is too early to tell if these experimental treatments are effective, we are seeing beneficial effects from our first gene therapy study – for a rare childhood disorder called Leber congenital amaurosis (LCA). As we move forward, we hope to expand our investigations to include patients with less severe forms of these diseases as well as more common eye conditions, such as age-related macular degeneration.
Gene therapy won’t restore eye cells lost to disease, but if we can treat people in the early stages, we can help them face a future without ever-diminishing eyesight.
Mark Pennesi, MD, PhD, is assistant professor of ophthalmology at OHSU Casey Eye Institute, where he specializes in ophthalmic genetics. He also is director of Casey’s Visual Function Service and the Ophthalmic Genetics Fellowship Program.
In recognition of his work in the field of inherited retinal disease, he is the recipient of numerous awards, most recently the Foundation Fighting Blindness’s prestigious Enhanced Career Development Award. He is currently exploring the potential of a new class of drugs to up regulate protective growth factors in the retina.