Gene Therapy Promises Cure For Leber's Congenital Amaurosis

Gene Therapy Promises Cure For Leber's Congenital AmaurosisThe first gene therapy trials on people with a rare form of blindness have shown there a dramatic improvement in light sensitivity and vision, barely a week after treatment.  Two other trials involving three patients each with a rare, inherited form of blindness have also proven successful representing a triumph for gene therapy and for modern medicine, and giving hope to others suffering from similar blinding diseases for which there is no cure.

Caused by a mutation of certain genes, Leber's congenital amaurosis (LCA) is a rare type of inherited blindness. Babies born with limited sight find their vision deteriorating as they grow older, leading to total blindness by the time they reach adulthood.

Researchers use specially engineered viruses or vectors to deliver an injection of healthy gene copies of a gene known as RPE65 into the retina cells, thus stimulating dysfunctional cells to work better.  The insertion of normal versions of RPE65, restores a cycle of enzymes which regenerate vitamin A molecules that are essential for converting light into nerve signals in the retina, at the back of the eye.  The results of the study showed a 50-fold improvement in cone function responsible for colour and day vision, including a startling 63,000-fold improvement in rod function controlling night vision.

However, while night vision improved, there was a slight catch with patients taking eight hours or more to adjust to darkness, compared with the hour or less it takes people with normal sight.

About 3,000 Americans have Leber's congenital amaurosis, of which only 10% have the RPE65 gene mutation, which makes them perfect candidates for gene therapy under study.  However, it is possible that similar treatments could be developed for treating other inherited retinal conditions, including certain forms of macular degeneration.

Reporting their success in the Proceedings of the Natural Academy of Sciences, Dr. Artur Cideciyan, Prof. Samuel Jacobson and colleagues at the Scheie Eye Institute, University of Pennsylvania said the finding can help in preventing child blindness and restoring adult vision.

Prof. Robin Ali and his team at University College of London Institute of Ophthalmology and Moorfields Eye Hospital, who performed the world’s first gene transplant for blindness, firmly believe that in two years gene therapy will be ready for treating inherited diseases of the retina, including age related macular degeneration (AMD), a common condition affecting many.

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