The vision of a man who lost his sight because of retinitis pigmentosa (RP) has been partially restored with optogenetic therapy in the first reported case of functional recovery in a neurodegenerative disease following this novel treatment.
“It was breathtaking to witness the first recovery of some visual function in a blind patient,” Botond Roska, MD, PhD, said in a news release.
“We have worked on optogenetic therapy in the lab for 16 years, and now seeing the proof of concept in a patient is a unique experience,” added Roska, founding director of the Institute of Molecular and Clinical Ophthalmology, Basel, Switzerland, and co-founder of GenSight Biologics, the company developing the therapy.
The case was reported online May 24 in Nature Medicine.
Significant Milestone
The 58-year-old man’s blindness was caused by retinitis pigmentosa (RP), a neurodegenerative eye disease in which loss of photoreceptors can lead to complete blindness.
As part of the phase 1/2a PIONEER study, the patient received an intraocular injection of an adeno-associated viral vector encoding the optogenetic sensor ChrimsonR into one blind eye. The team also engineered light stimulation goggles outfitted with a camera that captures and projects visual images onto the retina.
Training with the goggles began nearly 5 months after the injection, thereby giving ChrimsonR expression time to stabilize in ganglion cells. Seven months later, the patient began to report signs of visual improvement.
“In this type of study, we are really learning from the patients themselves. They are really like experimentalists telling us what they are seeing with restored vision,” lead investigator José-Alain Sahel, MD, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, said during a press briefing.
The patient was able to perceive, locate, count, and touch different objects using the vector-treated eye alone while wearing the goggles, the team reports. The patient could not visually detect any objects before injection with or without the goggles or after injection without the goggles.
The patient also reported significant improvements in his ability to conduct day-to-day activities, such as navigating in outdoor and indoor environments.
During visual perception, multichannel electroencephalographic recordings showed object-related activity above the visual cortex.
“So it was possible to show in this patient that visual behavior was correlated with brain activation corresponding to visual function,” Rosko said.
A video of the patient performing the tests, which was submitted as supplementary material to Nature Medicine, can be viewed at www.gensight-biologics.com.
“This is a significant milestone, and undoubtedly further refinements will make optogenetic therapy a viable option for many patients in future,” Robert MacLaren, MBChB, DPhil, professor of ophthalmology, University of Oxford, Oxford, United Kingdom, said in a statement from the nonprofit UK Science Media Center.
Also weighing in, James Bainbridge, MBChB, PhD, professor of retinal studies, University College London, London, United Kindgom, said, “This exciting new technology might help people whose eyesight is very severely impaired. It is a high-quality study. It is carefully conducted and controlled.
“The findings are based on laboratory tests in just one individual. Further work will be needed to find out if the technology can be expected to provide useful vision,” Bainbridge noted.
The study was funded by GenSight. Several authors have disclosed financial relationships with the company. MacLaren is a scientific advisor to NICE on retinal gene therapy. Bainbridge has disclosed no relevant financial relationships.
Nat Med. Published online May 24, 2021. Full text
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