New trial hopes to restore sight of severe-stage retinitis pigmentosa patients

A virus will introduce instructions to make remaining retinal cells light sensitive in 15 patients

24 Feb 2016 by Olivia Wannan

Zeiss Circus OCT advertA “life-changing” injection could restore sight to people left largely blind by retinitis pigmentosa.

The intravitreal injection will contain a modified virus, which will carry the genetic instructions for a light-reactive protein from the Chlamydomonas reinhardtii algae into one eye in each patient.

The 15-person trial, sponsored by RetroSense Therapeutics, will be conducted in Texas and begin in March, RetroSense chief medical officer, Dr Peter Francis, told OT.

“The study will last 18 months … [however] it should be a long-term treatment,” he said.

Dr Francis said the patients enrolled in the gene therapy trial all had severe vision loss from retinitis, with high degradation of their rods and cones.

He explained that the virus would insert the instructions for the light-sensitive protein into the genes of the eye’s surviving ganglion cells: “The remaining cells send signals back to the brain … They themselves will become light sensitive. We hope [these signals] will be decoded as vision,” he said.

The animal gene therapy trials have yielded positive results, Dr Francis noted, adding: “We know the signal is getting back to the brain.”

However, he emphasised what this meant for sight restoration is not yet clear: “What we know is very limited because we can’t really ask them [the animals] if they can see but … the data suggests not only can they see light, but they modify their behaviour. They are getting some sort of meaningful vision.”

Dr Francis said it would be massively exciting for the late-stage retinitis patients to have even moderate or minor improvements in vision, such as the ability to see shapes or figures.

“It would be a life-changing result for these patients … They might be able to live independently,” he said.

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