Retina UK’s Gene Team project, led by Profs Robin Ali and James Bainbridge and Dr Michael Michaelides at UCL, started in 2011 and set out to develop a pipeline of gene therapies for several inherited retinal conditions. A few of these therapies, including two targeting the achromatopsia genes CNGA3 and CNGB3, have reached clinical trials under the sponsorship of Meira GTx – Janssen Pharmaceuticals.
Dr Tessa Dekker and colleagues at UCL used the achromatopsia clinical trials as an opportunity to study the potential for gene therapy to impact neural connections between the eye and brain. The researchers have now demonstrated that the therapy partly restored the function of the retina’s colour-detecting cells (known as cone photoreceptors) in two children who were born completely colour-blind, and appeared to stimulate previously inactive eye-brain communication pathways.
Dr Dekker said: “Our study is the first to directly confirm widespread speculation that gene therapy offered to children and adolescents can successfully activate the dormant photoreceptor pathways and evoke visual signals never previously experienced by these patients. We are demonstrating the potential of leveraging the plasticity of our brains, which may be particularly able to adapt to treatment effects when people are young.”
The study involved four children between the ages of 10 and 15. Each of the four was treated with gene therapy in one eye, enabling doctors to compare the treatment’s effectiveness with the untreated eye.
For two of the four children, there was strong evidence for cone-mediated signals in the brain’s visual cortex coming from the treated eye, six to 14 months after treatment. Before the treatment, the patients showed no evidence of cone function on any tests. After treatment, their measures closely resembled those from normal sighted study participants.
The researchers say they cannot confirm whether the treatment was ineffective in the other two study participants, or if there may have been treatment effects that were not picked up by the tests they used, or if effects are delayed.
The results of the clinical trials as a whole have yet to be compiled, so the overall effectiveness of the treatments remains to be determined.
For more detail about Dr Dekker’s study, visit: https://www.ucl.ac.uk/news/2022/aug/gene-therapy-completely-colourblind-children-partly-restores-cone-function