Gene therapy, light stimulation combination tolerated, safe
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A combination of optogenetic gene therapy and the use of a light stimulation medical device for the treatment of retinitis pigmentosa was well-tolerated among the first cohort of patients enrolled in the PIONEER study, according to data reported at the Association for Research in Vision and Ophthalmology annual meeting. The phase 1/2a open-label PIONEER study evaluated the tolerability and safety of the optogenetic treatment GS030 among patients with non-syndromic RP.

The study included three dose-escalation cohorts – 5E10, 1.5E11, 5E11 VG/eye, – with each consisting of three patients.
In the first cohort, the researchers reported no serious adverse events or study discontinuations up to 1 year after treatment administration. Mild anterior chamber inflammation responsive to corticosteroid treatment and mild sensitivity to light starting after drug product administration but before light stimulation by the goggles were the most commonly reported adverse events. Two months after patients received the gene therapy, the light stimulating medical device was used to stimulate ChR-tdT.

In the second cohort, which is ongoing, two patients received 1.5E11 vg/eye, and no serious or unexpected adverse events were reported. Treatment with the highest dose will occur during the third cohort, which the researchers said is planned for some time in Q1 of 2020. The therapy is minimally invasive, as it is delivered via an intravitreal injection instead of surgery, and it is not an ongoing therapy, occurring only one time.

The therapy itself is a gene that was isolated from green algae. Its channelrhodopsin (ChR-tdT), which is a light-sensitive protein. The target cell is an inter retinal cell called retinal ganglion cell, and retinal ganglion cells normally are not light-sensitive cells in the retina. But the objective of this therapy is to transform these retinal ganglion cells to confer some light sensitivity so that they behave like the photoreceptors that are lost in patients with RP.