Gene therapy brings the light to human eyes

A QUANTUM OF SCIENCE

Gene therapy delivers on promise of better sight for congenital degenerative eye disorder

A recent AQOS post described the landmark success of gene therapy in curing congenital color-blindness in monkeys – the first primate study to achieve that success. Now, researchers have concluded a two-year study following the effects of similar gene therapy treatments for a congenital degenerative eye condition... in humans.

Twelve human volunteers with a condition known as Leber's congenital amaurosis agreed to be given gene therapy in one eye. Though multiple genes are responsible for the development of amaurosis, this study chose to replace the patients’ own copy of a gene called RPE65. The protein encoded by the RPE65 gene is located in the retinal pigment epithelium and is involved in the conversion of trans-retinol to 11-cis retinal during phototransduction (the molecular perception of light), which is then used in visual pigment regeneration in photoreceptor cells. Without a functioning copy of RPE65, humans suffer a steady decrease in vision and are often legally blind by the age of five.

In this study, twelve volunteers – five of them children – received a new copy of RPE65 in the cells of one eye. Within two weeks, the treated eyes began to become more sensitive to light, and within a few more weeks, vision began to improve. The younger the patients were, the better they responded. The youngest patient (age 9) had been legally blind before the study, and afterwards experienced a sufficient increase in sightedness that he is able to ride a bicycle and play softball. Older patients had less improvement because their eyes had greater degeneration in their retinal cells. Still, the improvement is marked and has persisted for the duration of the two-year study. Yet to be answered questions are whether the change is permanent, and what happens if the same therapy is given to the patients’ other eye.

Gene therapy is a field rapidly outstripping medical practitioners’ ability to conduct relevant trials, but this success augurs well for medical and financial support for future studies.

For more information:

Gene therapy transforms eyesight of 12 born with rare defect (LA Times)

Safety and Efficacy of Gene Transfer for Leber's Congenital Amaurosis (New England Journal of Medicine, Maguire et al)

Leber’s congenital amaurosis (Wikipedia)

RPE65 gene (Wikipedia)

Adenovirus-based gene therapy (Wikipedia)

© AQOS / P. Smalley (2009)
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