A new report outlines steps to bringing future regenerative therapies for blinding diseases of the retina to patients. The retina is the light-sensitive tissue in the back of the eye. When stimulated, retinal neurons send visual information to the brain. Diseases like age-related macular degeneration (AMD), glaucoma, and diabetic retinopathy can irreparably damage or destroy these neurons, which fail to regenerate on their own.
“Advances in stem cell technology and tissue engineering in the last several years have opened the possibility of replacing lost retinal neurons,” wrote Leonard Levin, M.D., Ph.D., McGill University, and co-authors in the report, published online April 6, 2017, in Ophthalmology.
The report considers characteristics that might make some retinal diseases more amenable to regenerative therapy than others. Such disease characteristics include genetic versus acquired, early onset versus late-onset, acute versus chronic, and one affected eye versus both. According to the authors, rare eye diseases caused by single mutations, such as retinitis pigmentosa, might be easier to test first because they follow a more predictable clinical course than common ones such as AMD, which have multiple genetic and environmental influences. People with early disease are likely to be easier to treat because the disease has inflicted less damage to the retina. People with acute disease often suffer less disease-related structural damage, such as scarring, which might interfere with regenerative therapies. And diseases that affect both eyes provide the opportunity to treat one eye and use the other as a control to measure treatment effect.
The report explores potential clinical endpoints to measure treatment success—for example, improvements in vision or observable regrowth of retinal cells. Along with considerations for establishing efficacy, the report addresses the safety and ethical challenges that are inherent with any highly experimental therapy that has minimal precedent. For example, while early stage disease might be more amendable to treatment, such patients are at risk of losing usable vision should treatment fail.
Finally, the report provides a status update on the approximately 20 ongoing clinical trials that use cell-based therapies for retinal disease.
The report is based on a town hall discussion convened during the 2016 Association for Research in Vision and Ophthalmology annual meeting in Seattle. The National Eye Institute organized the event as part of its Audacious Goals Initiative, a sustained effort to restore vision by regenerating neurons and neural connections in the eye and visual system.
Levin LA, Miller JW, Zack DJ, Friedlander M, Smith LEH. Special Commentary: Early Clinical Development of Cell Replacement Therapy: Considerations for the National Eye Institute Audacious Goals Initiative. Ophthalmology. April 6, 2017.