New gene therapy improves colour blindness

A new study has found that a new genetic treatment for complete colour blindness is safe, while preliminary findings have also confirmed its efficacy.

German researchers have developed a new therapy for achromatopsia, a condition that renders patients completely colour blind and causes blurred vision and bright light sensitivity.

In about a third of achromatopsia patients, the defect lies in the CNGA3 gene.

A bed of colourful flowers as a person with normal sight sees it – sharply focused and in colour. A simulation of the same image in the eyes of a person with complete colourblindness. Photo and simulation: Stylianos Michalakis

A research team from the Institute for Ophthalmic Research (OIR) at the University Hospitals in Tübingen and the Departments of Pharmacy and Ophthalmology at Ludwig Maximilian University of Munich (LMU) have developed a potential treatment that introduces the correct version of the defective gene directly into the patient’s retina.

It is transported via an adeno-associated virus developed at LMU.

Results from the first clinical study into this approach have been published in the journal JAMA Ophthalmology. Nine achromatopsia patients aged between 24 and 59 years were treated in their more severely affected eye.

“The experimental subjects suffered no drug-related health problems as a result, nor did their retinas show any permanent changes,” Professor Dominik Fischer, who headed the clinical study, said.

There was also a clear positive effect in terms of efficacy. The patients’ visual function has improved somewhat, both in terms of focus and in relation to contrast and colour vision.

For safety purposes, the nine patients chosen were all adults – and their retinas had already been damaged to varying degrees.

“Furthermore, the parts of the brain that process vision increasingly lose plasticity in adulthood,” said Professor Marius Ueffing, director of IOR in Tübingen. “Since the brains of people with achromatopsia have never learned to process colour information, they need at least some plasticity to translate the retina’s newly acquired ability to respond to colours into a real visual impression.”

Now that the study has shown that the treatment is safe, the researchers believe it may be feasible to treat patients early enough to take advantage of higher brain plasticity and retinal tissue that is yet to suffer substantial damage.

In future, they say the treatment should be performed during childhood, as in the case of the recently approved gene therapy Luxturna, in order to achieve the best possible effect.

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