Optogenetic therapy increased light sensitivity in 7 of 10 people blind from retinitis pigmentosa

What happened

Ten people blind from advanced retinitis pigmentosa each received one injection into the worse-seeing eye of a viral vector carrying the gene for ChrimsonR, a red-shifted channelrhodopsin, targeted at retinal ganglion cells. The aim is to make retinal ganglion cells respond to light directly. Participants used goggles that deliver light suited to activating ChrimsonR. The study was open-label and its primary outcome was safety.

Thirty-four ocular adverse events occurred in 9 of the 10 participants: 23 mild, 10 moderate and one severe. The severe event was a transient blockage of the central retinal artery immediately after the injection, which resolved within minutes of treatment. Light sensitivity increased in 7 of the 10 participants, by factors of 2.0 to 62.3, and 6 had an increase the investigators classed as clinically meaningful.

Why it matters

Optogenetic therapy makes cells electrically responsive to light by adding a light-gated ion channel, and had already shown potential for restoring visual function in late-stage disease. This study adds safety data and a measurable gain in light sensitivity in a group of ten people.

Caveats

The study was open-label and had ten participants. The threshold for a clinically meaningful improvement was taken from the literature and was not prespecified in the protocol. The measured outcome is sensitivity to light, which is not the same as useful vision. The authors themselves say more research is needed on safety and efficacy. The study was funded by GenSight Biologics, and one co-author is affiliated with the company. This entry is based on the abstract.