In a paper published Monday in the journal Nature Medicine, researchers working with the Paris-based company GenSight Biologics SA reported that a 58-year-old man who was diagnosed with retinitis pigmentosa 40 years ago was able to locate objects placed on a table after receiving an experimental therapy. And New York City-based company Bionic Sight LLC announced in March that four blind people in an early-stage clinical trial are now able to detect light and motion after undergoing a similar treatment. Those results haven’t yet been published.
The patients all had advanced cases of retinitis pigmentosa, which affects more than two million people world-wide. All underwent optogenetic therapy, in which an injection is used to deliver a gene into the eye to boost the light sensitivity of certain cells in the retina, a layer of tissue at the back of the eye. The companies are developing high-tech goggles that process and amplify light in a way that boosts the cells’ ability to send electrical signals to the brain.
The use of gene therapy to treat blindness isn’t new. Luxturna, a prescription medicine approved in 2017 by the U.S. Food and Drug Administration, is used in children and adults with a form of retinitis pigmentosa caused by a specific genetic mutation. Editas Medicine of Cambridge, Mass., is testing Crispr gene editing in retinitis pigmentosa patients with a different gene mutation.
But retinitis pigmentosa can be caused by mutations in more than 70 different genes, and doctors say it is too costly and difficult to develop a gene therapy for all of them.
Optogenetics offers the ability to treat blindness caused by retinitis pigmentosa regardless of the specific gene mutation that underlies it.
Optogenetic therapy gets around that problem by bypassing the photoreceptors, using the injected gene to confer light sensitivity to the ganglion cells that respond to light beamed into the eye by the goggles.
In the GenSight trial, an unnamed 58-year-old Frenchman received the optogenetic injection in one eye and was trained to use the goggles. In tests administered 4½ months after the injection, the man was able to perceive and count items placed before him on a table.
Only a small portion of the patients’ ganglion cells were treated, limiting the potential benefit. The treated patients aren’t expected to regain all of their lost eyesight—they can’t read, drive or recognize faces.
From A blind man can perceive objects after a gene from algae was added to his eye on MIT Technology Review:
Efforts to adapt the technique as a blindness cure began in 2016, when a Texas woman became the first person treated with optogenenetics by a small company, RetroSense, that was later acquired by Allergan. The results of that study were never publicly reported, although Allergan officials later said some patients claimed to see light, such as perceiving a bright window in a dark room.