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Gene therapy holds hope for blindness

Sun, 28th Sep 2008

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This week researchers have taken a step closer to using gene therapy for treating a type of inherited blindness.

Adeno Associated VirusesArtur Cideciyan from the University of Pennsylvania led a team who have been looking at therapies that aim to treat a rare form of blindness called Leber congenital amaurosis or LCA. Studies in animals have shown that it is a mutation in a particular gene called RPE65 that causes this disease. What it does is knock out part of a process in the eye called the retinoid cycle, which regenerates vitamin A, a critical step for converting light hitting the retina into nerve signals that are sent to the brain.

By using gene therapy to replace the RPE65 gene, researchers have been able to restore the vision in animals suffering from LCA. The therapy is based on a genetically modified virus which is injected into the eye and essentially delivers a “good” version of the gene that fills in the missing link of the retinoid cycle.

And the encouraging news is these Cideciyan and his team have started trying out this gene therapy on people. These are just early stage clinical trials, but they have already shown that the treatment is safe to use and can lead to moderate improvement in vision.

Three patients with LCA were injected with the treatment and after 30 days all three had shown improvement in their eyesight.

It seems the therapy is increasing the activity of cone cells, the parts of the eye responsible for seeing colour, by up to 50 times. And that the activity of rods, the parts responsible for night vision, could increase by 63 thousand times.

While this is encouraging news, the results of the treatment are still far from perfect. One problem was that it took the patients a very long time to get accustomed to the dark. For people with normal vision it takes less than an hour to adapt to low light levels – but in the treated patients it took them up to eight hours.

So this might not be perfect, but it already holds some hope for the development of future treatments.


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