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November 03, 2009

Gene Therapy Shows Promise in Restoring Vision


There is an interesting article in this month's Lancet:  Age-dependent effects of RPE65 gene therapy for Leber's congenital amaurosis: a phase 1 dose-escalation trial.    Results were also reported in yesterday's New York Times.


According to the Lancet article:

Gene therapy has the potential to reverse disease or prevent further deterioration of vision in patients with incurable inherited retinal degeneration. We therefore did a phase 1 trial to assess the effect of gene therapy on retinal and visual function in children and adults with Leber's congenital amaurosis.

AAV2-hRPE65v2 was well tolerated and all patients showed sustained improvement in subjective and objective measurements of vision.  The greatest improvement was noted in children, all of whom gained ambulatory vision. 

The safety, extent, and stability of improvement in vision in all patients support the use of AAV-mediated gene therapy for treatment of inherited retinal diseases, with early intervention resulting in the best potential gain.

Leber congenital amaurosis (LCA) is an inherited retinal degenerative disease characterized by severe loss of vision at birth.  Scientists have identified 14 genes with mutations that can each cause LCA.  These genes account for approximately 75 percent of all cases of LCA.  This is the basis of this clinical trial.

According to the Times article:

The researchers injected into the eyes of the patients a virus with the normal version of the gene REP65 inserted into its genome. When the virus invaded the light-sensing cells in the eye and inserted its own DNA into the cells’ DNA, the crucial human gene was included.

Starting at about two weeks, “all 12 had significant improvement,” said Stephen Rose, chief research officer at the Foundation Fighting Blindness, which helped finance the study. That meant the inserted gene was functioning. “You’re not returning 20-20 vision, let’s be real,” Dr. Rose said, “but you’re returning a tremendous amount of vision.”

Dr. Jean Bennett, an ophthalmology professor at University of Pennsylvania who was a leader of the study, said participants could “read signs or see numbers on their cellphones, stripes on their clothes, patterns on furniture, wood on a violin or marble on a table.” Some read several more lines on eye charts.

Children improved the most, perhaps because fewer photoreceptors had decayed. But even the oldest patient, Tami Morehouse, 44, who was sometimes housebound, now walks to meet her children coming from school and “saw her daughter hit a home run,” Dr. Bennett said.

The Times article is accompanied by a video of a child treated in the trial.  The video shows a marked improvement in his ability to navigate an obstacle course.  It is well worth watching.

Although this is the early results of one clinical trial, it is exciting news.  Gene therapy may hold promise for many other retinal diseases, including Retititis Pigmentosa (RP)!


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