First-in-Human Trial of Photoswitch Drug Shows Promise for Restoring Vision in Retinitis Pigmentosa
核心洞察
Adelaide University researchers completed the first-in-human clinical trial of a photoswitch drug for retinitis pigmentosa (搜索), demonstrating safety and early signals of biological effect.
The small-molecule treatment revived damaged retinal cells and restored light sensitivity even after photoreceptor loss, with some participants reporting improved light perception within two days.
Unlike gene therapies targeting specific mutations, this photopharmacological approach could potentially treat many forms of retinal degeneration without genetic modification or implanted devices.
Adelaide University researchers have conducted the first-ever clinical trial of a photoswitch drug in humans, marking a significant milestone in the treatment of retinitis pigmentosa (搜索) (RP), a leading cause of blindness in working-age adults. The small pilot trial, published in Nature Medicine with industry support from Kiora Pharmaceuticals (搜索), found that the small-molecule therapy was well tolerated and produced early signals suggesting biological activity—including changes in light perception and brain imaging evidence of visual cortex activation.
"This is the first clinical trial of a photoswitch drug in humans. Unlike gene therapies, which target specific mutations, this approach could potentially be used across many different forms of retinal degeneration," said Robert Casson, Professor and Principal Investigator at the School of Medicine, Adelaide University. "It also avoids the need for genetic modification, which simplifies treatment and may reduce risks."
How the Photoswitch Approach Works
Retinitis pigmentosa (搜索) is a genetic condition in which the retinal cells responsible for detecting light progressively degenerate, resulting in blindness. Current treatment options for later-stage disease are limited, and no cure exists. The new approach relies on a small molecule that, when injected into the eye, revives damaged retinal cells and makes them sensitive to light again—even after the normal light-sensing photoreceptor cells have been lost.
The trial was originally designed as a small safety study. "What originally started as a very small trial to test the safety of the drug has now opened up the possibility of a completely new way of treating degenerative eye diseases," Casson noted.
Early Clinical Signals
Several participants reported short-term improvements in their ability to perform visual tests, including walking tasks. One participant with severely damaged retinal cells reported greater awareness of light perception within two days of receiving the treatment.
"We found that the treatment was well tolerated, with no serious adverse events and no evidence of harmful effects on the eye," said Professor Casson. "We also saw early signals suggesting the drug may be having a biological effect—some participants reported changes in light perception, and brain imaging showed activity in visual areas of the brain following treatment."
Casson cautioned that these are preliminary findings that need confirmation in larger studies. A larger Phase 2 trial is currently underway to more rigorously assess whether the treatment can improve vision.
Broader Implications for Retinal Disease
The clinical findings align with a growing body of preclinical research in photopharmacology. A separate study published in the Journal of the American Chemical Society (JACS), led by the Institute for Bioengineering of Catalonia (IBEC), demonstrated that a related class of photoswitchable small-molecule drugs called prosthe6 (搜索) could restore key visual functions in animal models of blindness, including age-related macular degeneration (搜索) (AMD) and RP.
These compounds target ON bipolar cells via the mGlu6 (搜索) receptor, effectively acting as "molecular prostheses" that take over the role of missing photoreceptors. In mouse models, treatment with prosthe6 (搜索) compounds restored innate light-avoidance behavior—blind mice once again showed a spontaneous preference for dark areas—without any training and under normal indoor lighting conditions. Notably, the effects were observed after both intraocular injection and topical administration as eye drops.
"These molecules do not cure blindness, because they do not address the cause of photoreceptor degeneration. But they are remarkably effective at restoring sight, and they do so using a very simple and potentially patient-friendly approach," said Pau Gorostiza, ICREA Research Professor at IBEC and co-leader of the preclinical study.
A New Platform for Vision Restoration
Blinding diseases caused by photoreceptor degeneration affect approximately 200 million people worldwide and represent the leading causes of visual impairment and blindness, with a global economic burden estimated at over US$400 billion per year. Current strategies—including gene therapy, electronic retinal prostheses, and optogenetics—each face limitations in patient eligibility, invasiveness, or cost.
"More broadly, this work establishes a new platform for vision restoration that could be developed further for retinal diseases beyond retinitis pigmentosa (搜索)," said Professor Casson. The prosthe6 (搜索) technology is protected by patent, and researchers are now evaluating its safety and formulation to extend the duration of visual rehabilitation, with a spin-off company, Eyelumina, in formation to support translational development and future clinical trials.