“We are trying to treat people who do not have any photoreceptors left”

Scientists from GenSight Biologics shared details of two projects to treat inherited eye disease at the annual meeting of the American Academy of Ophthalmology (12–15 October, San Francisco). The company’s chief medical officer, Magali Taiel (pictured), discusses the development of a gene therapy for Leber hereditary optic neuropathy (LHON) and applying optogenetics to retinitis pigmentosa.

Can you tell OT about the development of a treatment for LHON by GenSight?

We have a gene therapy called GS010 which is in the late stages of development. We are going to submit applications to the European Medicines Agency and Food and Drug Administration for registration of the treatment next year.

GenSight has completed clinical trials showing a bilateral improvement in visual acuity among LHON patients when injected in one eye with the gene therapy. This was unexpected. We did not think we would see an improvement in the sham eyes.

As a result, we launched a non-human primate study to try and understand why we were seeing this effect of a gene therapy in one eye benefitting the contralateral eye, which was not injected. We injected monkeys unilaterally with gene therapy before searching for GS010 DNA in their visual systems. We found GS010 in the injected eyes but what is really great news is that we also found GS010 in the contralateral eyes of these monkeys.

If we can help patients who are at a late stage of disease and currently have no options for treatment, that is a great motivation to continue with our work

This is really important news because it means that when you inject one eye with GS010, there is a probable anatomic route for the transfer of GS010 DNA from the injected eye through the optic nerve to the contralateral optic nerve and the non-injected eye.

What work is GenSight doing to develop a treatment for retinitis pigmentosa?

We are developing a gene therapy, GS030, which is combined with goggles that project a specific type of light back onto the retina. We are at the beginning of that development and have our first in-human study that is ongoing. We have five subjects injected with the gene therapy in the UK, US and France.

So far, the safety of the treatment has been really good. There was mild inflammation in two patients that was resolved with treatment. We do not have efficacy results right now because it is in the very early stages, but we are expecting preliminary results in the middle of next year.

The beauty of this is that we are trying to treat people who do not have any photoreceptors left. We are using a technique where we stimulate the retinal ganglion cells to transform their function into that of photoreceptors by encoding a light-sensitive protein. If we can help patients who are at a late stage of disease and currently have no options for treatment, that is a great motivation to continue with our work.