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Gene therapy with new medical device

First optogenetic trial for retinitis pigmentosa under way

Dermot McGrath

Posted: Tuesday, July 9, 2019

A novel optogenetic therapy for retinitis pigmentosa has commenced its first clinical trial in humans with early results of the initial cohort expected later this year, according to Barrett Katz MD.

“There is no therapy at the moment for this family of diseases and because of the multitude of genetic contributions the strategy for intervening has to be different than a treatment that is directed against any one gene,” he told delegates attending the 9th EURETINA Winter Meeting in Prague.

Dr Katz noted that this is the first ever study in humans of a combined gene therapy and medical device. The gene therapy is administered via a single intravitreal injection and then combined with special optronic goggles to enhance effects of the light sensitive protein encoded into the gene.

“The therapy transfers the ChrimsonR gene, which encodes for a light-sensitive protein into the retinal ganglion cells. It effectively changes the retinal ganglion cells into photoreceptors, thereby making them responsive to light and bypassing destroyed photoreceptors,” he said.

The special goggles are required because cells expressing optogenetic proteins are less light-sensitive than normal photoreceptors, explained Dr Katz.

“ChrimsonR would not be activated by usual ambient light, so we intensify the projection system focus using a wavelength of 590nm. The goggles also capture the visual scene in real-time, processes it on to a beam of amber light and projects this on to the transfected retina,” he said.

The open-label open-masked non-randomised dose escalation study is being conducted at three centres: Moorfields Eye Hospital in the UK, Quinze-Vingts Hospital in France and the University of Pittsburgh Medical Center in the United States.

Eligible patients in the three cohorts are all affected by end-stage non-syndromic retinitis pigmentosa with very severe vision loss. The patients will be administered an increasing dose of the therapy via a single intravitreal injection in their worse affected eye. The primary outcome analysis will be the safety and tolerability at one-year post-injection, noted Dr Katz.

Functional tests involving mobility and orientation tasks will also be performed as part of the trial.

“This is the first combined intervention of gene therapy and a medical device in humans. If this technology is shown to be effective it will be easily transferable to any disease in which the photoreceptors are gone but the ganglion cells are preserved. The compelling possibility and promise, of course, is to be able one day to use this therapy for a disease such as dry AMD,” concluded Dr Katz.

Barrett Katz: bkatz@gensight-biologics.com


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