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Gene Therapy Shows Promise in Restoring Vision

November 3, 2009

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.

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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