GenSight's mutation-agnostic gene therapy triggers partial vision recovery

GenSight Biologics has reported the partial recovery of the vision of a retinitis pigmentosa patient treated with its mutation-independent approach to the restoration of visual function.

Spark Therapeutics, now part of Roche, won FDA approval for its retinitis pigmentosa gene therapy Luxturna in 2017. However, the approval only covered the use of Luxturna in patients with confirmed biallelic RPE65 mutation-associated retinal dystrophy. As retinitis pigmentosa is caused by changes to more than 70 genes, it is questionable whether mutation-specific approaches can cover all patients. 

Recognizing that, GenSight is developing GS030, an optogenetic therapy. The drug component of the intervention consists of a viral vector designed to cause the expression of the light-sensitive opsin ChrimsonR in retinal ganglion cells.

In a phase 1/2 clinical trial, physicians administered the gene therapy via a single intravitreal injection to the worse-seeing eye of a 58-year-old man who was diagnosed with retinitis pigmentosa 40 years ago and was unable to detect objects visually. The patient was still unable to detect objects visually after the injection.

However, the patient could perceive, locate, count and touch different objects using his treated eye while wearing a pair of goggles. The goggles detect changes in light intensity and send pulses of light to the retina in real time, effectively amplifying the signal sent to the ChrimsonR-expressing cells.

Writing in Nature Medicine, the investigators said the patient “is the first reported case of partial functional recovery in a neurodegenerative disease after optogenetic therapy.” The claim is based on three visual tests, the last of which was performed five months after the others, that took place in an indoor laboratory, but there is also patient-reported evidence of real-world benefits.

“The patient spontaneously reported identifying crosswalks and he could count the number of white stripes. Subsequently, the patient testified to a major improvement in daily visual activities, such as detecting a plate, mug or phone, finding a piece of furniture in a room or detecting a door in a corridor but only when using the goggles,” the authors of the research paper wrote. 

The paper only describes the experience of one patient, and the recovery in his vision was partial. GenSight recruited six patients across the first two cohorts of the dose-escalation trial before putting enrollment on hold in response to the pandemic. Enrollment in the third cohort is now complete, and GenSight expects to recruit an extension cohort that will get the optimal dose by the end of 2021.

A clearer picture of the efficacy of GS030 will emerge as GenSight shares data on other recipients of the treatment. Other companies are pursuing the same opportunity. Novartis, for example, bought optogenetic gene therapy startup Vedere Bio for $150 million upfront last year.