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RandomFactor writes:

A clinical trial designed to test safety has been successful in stopping, and even reversing, visual degeneration associated with mutations in the gene RPGR (Retinitis Pigmentosa GTPase Regulator).

This month, K.L. became one of the first patients to receive a new experimental gene therapy for children with a severe form of inherited vision loss. The treatment, currently not yet named, targets young men who are susceptible to a particularly vicious genetic disorder that gradually destroys the light-sensing portion of their eyes.

Within a month following a single injection, “my vision was beginning to return in the treated eye. The sharpness and depth of colors I was slowly beginning to see were so clear and attractive,” said K.L.

The treatment targets the difficult condition which leaves most affected legally blind by the age of 20, and yielded improvements in participant vision in as little as two weeks following treatment.

It is based on the gene therapy 'Luxturna' introduced in 2017, but which is only able to help one out of 80 afflicted with inherited RP (Retinitis Pigmentosa) related vision degradation.

Unfortunately, the RPGR gene also happens to be quite temperamental and prone to genetic shifts that cause disease. It makes the gene a terrible test subject in the lab, where it tends to be unstable and difficult to work with.

After years of wrangling in animal models, however, the Oxford team was able to increase its “stability and fidelity,” so much so that when given to animal models with retinal disease, the stabilized, healthy version was able to restore visual properties.

In this first human trial, the healthy gene was packaged with a virus carrier and injected into the eyes of 18 patients included in the trial. All patients, except the three who received the lowest dose, saw noticeable improvements.

"The results will next be validated in a broader population."

For K.L., however, the trial has already revamped his life for the better.

“The results have been nothing short of astonishing and life changing for me, I really hope this trial is approved and they can treat what once was my better eye,” said K.L.

Safety results were also promising with only those receiving the highest dosages experiencing some mild initial inflammation (treated with steroids).

Journal Information: Initial results from a first-in-human gene therapy trial on X-linked retinitis pigmentosa caused by mutations in RPGR, Nature Medicine (DOI: doi:10.1038/s41591-020-0763-1)

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