NIH researchers have discovered that reserpine, a blood pressure medication first approved in 1955, may prevent vision loss in patients with inherited retinal dystrophies, particularly retinitis pigmentosa. The findings, published in eLife, reveal that the drug's neuroprotective effects work independently of specific genetic mutations, offering a potential breakthrough for treating a range of blinding diseases.
"The discovery of reserpine's effectiveness may greatly speed therapeutics for retinitis pigmentosa and many other inherited retinal dystrophies, which can be caused by one of more than a thousand possible mutations affecting more than 100 genes," said Dr. Anand Swaroop, senior investigator at NIH's National Eye Institute and lead investigator of the study.
Broad Potential for Multiple Genetic Conditions
Inherited retinal dystrophies cause degeneration of the retina, the light-sensing tissue at the back of the eye. These conditions can manifest at birth or develop in early adulthood, with progression varying based on the specific genetic defect. Current treatment approaches like gene therapy, while promising, are limited by their gene-specific nature, lengthy development timelines, and high costs.
Reserpine's mechanism appears to improve survival of photoreceptor cells—the light-detecting retinal neurons that die in retinitis pigmentosa and other retinal dystrophies. This builds on the Swaroop Lab's 2023 findings that demonstrated reserpine's potential for preventing vision loss from LCA10, a retinal dystrophy caused by mutations in the CEP290 gene.
Sex-Specific Protection Observed
In their latest work, researchers tested reserpine in a rat model of a dominant form of retinitis pigmentosa caused by a mutation in the rhodopsin gene—a mutation commonly found in Irish Americans with the condition. The results showed that reserpine preserved phototransduction, the process by which photoreceptors convert light into electrical signals for the brain.
Notably, the study revealed unexpected sex-specific differences in treatment response. Female rats showed significantly better protection of both rod photoreceptors (responsible for low-light vision) and cone photoreceptors (enabling color vision in bright light) compared to males.
"We can only speculate about these sex-specific differences. However, future research would benefit from teasing out these differences and understanding them to lay a foundation for personalized approaches to retinal disease therapy," Dr. Swaroop explained.
Practical Advantages for Treatment
While reserpine is no longer commonly used for treating high blood pressure due to its side effects, the researchers note that treating retinal degeneration would require very low dosages delivered directly to the eye. As a small molecule therapy, reserpine offers advantages in terms of delivery to target tissues in the eye.
The Swaroop lab is already developing additional, more potent reserpine-related drugs. Their strategy involves using such treatments for late-onset or slowly progressing inherited retinal dystrophies, or to temporarily halt vision loss in aggressive forms of retinitis pigmentosa until more effective treatments can be developed.
Future Directions
This research, supported by the NEI Intramural Research Program, represents a significant step toward addressing the unmet needs of patients with inherited retinal diseases. The repurposing of an existing drug could potentially accelerate the path to clinical applications, offering hope to patients who currently have limited treatment options.
The researchers' next steps will include further investigation of the sex-specific differences in treatment response, which could lead to more personalized therapeutic approaches for patients with inherited retinal diseases.
For the thousands of patients affected by various forms of inherited retinal dystrophies, this repurposing of reserpine offers a promising new avenue for treatment that works across multiple genetic mutations—potentially providing a more accessible and affordable option than gene-specific therapies.
