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Optogenetic therapy partially recovered visual function in a blind patient

The patient, suffering from retinitis pigmentosa, is a participant in the ongoing PIONEER Phase I/II clinical trial of GenSight Biologics’ GS030 optogenetic therapy.

These groundbreaking results, from among others biopharma company GenSight Biologics, the Institute of Molecular and Clinical Ophthalmology Basel and the Institut de la Vision at Sorbonne Université/Inserm/CNRS), Paris, were published in Nature Medicine.

Retinitis pigmentosa is a progressive, inherited neurodegenerative eye disease where loss of photoreceptors can lead to complete blindness.

Light stimulation via engineered goggles

The optogenetic therapy, GS030, uses an optimized viral vector (GS030-DP) to express the light-sensitive opsin ChrimsonR in retinal ganglion cells and light-stimulating goggles (GS030-MD) to project the right wavelength and intensity of light onto the treated retina. GS030-DP is administered via an intravitreal injection.

In the open-label phase 1/2a PIONEER study, the researchers injected the adeno-associated viral vector encoding the optogenetic sensor ChrimsonR into one eye of the 58-year old male patient, combined with light stimulation via the engineered goggles. The goggles detect local changes in light intensity and project corresponding light pulses onto the retina in real time to activate optogenetically transduced retinal ganglion cells, states the scientists in their article (J.-A. Sahel et al. Partial recovery of visual function in a blind patient after optogenetic therapy. Nat Med, published online May 24, 2021).

Improvements in his ability to conduct day-to-day activities

The patient’s gene therapy injection was followed four and a half months later by training on the use of the GS030-MD device. Seven months after the start of his training, he began to report signs of visual improvement. Visual function tests showed he acquired the ability to perceive, locate, count and touch objects when his treated eye was stimulated with the GS030-MD goggles. Without the goggles, he could not perform the tasks.

While the patient performed vision-oriented tasks, recordings were taken using extracranial multi-channel electroencephalography (EEG). The EEG signals suggest that the act of carrying out the visual perception tests was accompanied by neurophysiological activity in the visual cortex.

In addition, the patient also reported significant improvements in his ability to conduct day-to-day activities such as navigating in outdoor and indoor environments and detecting household objects and furniture.

A promising way to partially restore vision

Now, further results from the PIONEER trial are needed for a clearer picture of the safety and efficacy of this approach, states the scientists.

“Taken together, the psychophysical and neurophysiological evidence presented in our article suggest that the optogenetic stimulation of human retinal ganglion cells by a light-projection system linked to a camera is a promising way to partially restore vision in blind patients affected with advanced retinitis pigmentosa,” the authors said.

Optogenetics

Optogenetics is a technique to control or to monitor neural activity with light which is achieved by the genetic introduction of light-sensitive proteins.

Optogenetics may enable mutation-independent, circuit-specific restoration of neuronal function in neurological diseases.

Several groups are trying to develop optogenetics as a treatment for blindness because nerve cells in the eye are exposed to outside light.

“I think that optogenetics, applied to animal brains, will reveal new targets for drugs to be developed against, as well as new patterns of activity that, if induced through noninvasive means, will help heal the brain. One of my favorite examples is from Li-Huei Tsai, who discovered, using optogenetics, a pattern of activity – a 40 Hz brainwave – that in mice cleans up the molecular problems in Alzheimer’s disease. Her team went on to figure out that you could induce this pattern effectively by having the mice watch a movie,” said Ed Boyden, a Y Eva Tan Professor in Neurotechnology and Professor of Biological Engineering and Brain and Cognitive Sciences at the MIT Media Lab and MIT McGovern Institute, USA, in a previous interview with NLS.

Read more: Making the invisible visible

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