April 28, 2008 in Nation/World

Gene therapy aiding blind

Thomas H. Maugh II Los Angeles Times
 

At a glance

Leber’s congenital amaurosis affects about 3,000 people in the United States and perhaps 1 in every 50,000 worldwide. Children with the disorder are born with severely impaired vision that deteriorates until they are totally blind in childhood or adolescence. There is no treatment.

For the first time, researchers have used gene therapy to increase light sensitivity and improve vision in patients who were virtually blind, a finding that offers new hope to hundreds of thousands of patients with inherited forms of vision impairment.

Although the patients studied have an extremely rare form of blindness called Leber’s congenital amaurosis, researchers believe the approach ultimately could be used for a broader spectrum of disorders, including retinitis pigmentosa and macular degeneration.

The treatment, so far meant only to prove the safety of the technique, produced “real clinical benefit” and “made a real difference in patients’ lives,” said geneticist Robin R. Ali, of University College London, the senior author of one of two reports presented Sunday at a Fort Lauderdale, Fla., meeting of the Association for Research in Vision and Ophthalmology.

The reports were published online Sunday by the New England Journal of Medicine.

“The fact that they had patients who could now read lines on an eye chart … and one who could run an obstacle course – this is a really great advance,” said geneticist Stephen Rose, chief research officer of the Foundation Fighting Blindness, who was not involved in the research.

Added Dr. Morton F. Goldberg, an ophthalmologist at John Hopkins University’s Wilmer Eye Institute, “In the field of retinal dystrophies, this is, I believe, the most important therapeutic discovery” in four decades. “It’s a landmark.”

The results are particularly important because gene therapy, in which a good gene is substituted for a naturally occurring defective one, has been “a snake-bitten field,” with at least two subjects in other experiments dying and a handful of others developing cancer, said Dr. Albert M. Maguire of the University of Pennsylvania School of Medicine, lead author of the second report.

What makes Leber’s a good candidate for gene therapy is that most of the visual apparatus, including the retina, is intact. Typically, the defective gene that causes it is one of several in a biochemical pathway that produces chemicals necessary for the eye to generate an electrical signal for transmission to the brain.

If that gene could be replaced before the visual apparatus deteriorates from lack of use, vision could be restored, Maguire said.

That same basic strategy could be used to treat a variety of congenital retinal disorders. “With an aging population, one of the most serious problems that hinders old people is the loss of sight,” said Dr. Katherine A. High of Children’s Hospital of Philadelphia and a co-author of one of the studies.


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