Three more blind patients helped by gene therapy

WASHINGTON (Reuters) - Three more patients treated with an experimental gene therapy approach have reported better vision, U.S. researchers reported on Monday in a study that lends further support to the approach.

The patients, all in their early 20s, reported markedly better vision after getting the treatment, Artur Cideciyan and James Wilson of the University of Pennsylvania and colleagues reported.

"Day vision improvement could range up to 50-fold from pre-treatment levels. Night vision was quite dramatic and ranged up to 63,000 times" better, Cideciyan said in a telephone interview.

Their findings, published in the Proceedings of the National Academy of Sciences, lend weight to similar results from rival teams all treating the same condition -- Leber congenital amaurosis, or LCA.

The condition is caused by a mutation in a gene called RPE65, and experts have long thought it is a good target for gene therapy. Gene therapy is an experimental field of medicine that aims to correct diseases by replacing faulty genes.

LCA damages light receptors in the retina. It usually begins affecting sight in early childhood and causes total blindness by the time a patient is 30. There is no treatment.

All the teams used a virus called an adeno-associated virus to deliver a normal version of the damaged RPE65 gene into the eyes of patients. The virus itself causes no symptoms in people.

DAY AND NIGHT

"We checked whether it was day or night vision or both that was restored by this therapy," Cideciyan said. "We found that both are corrected or restored in this condition."

"The patients are saying, 'There is a difference in my vision -- things are looking brighter. The colors are more vivid and I am seeing colors,'" he added.

The patients were not entirely blind, he noted. "It's like ... wearing three deep dark sunglasses on top of each other," he said. "What our treatment does is it basically removes two of the three (pairs of) sunglasses in one part of eye."

The effects have lasted for as long as three months, Cideciyan said.

In April, two rival teams reported similar results in the New England Journal of Medicine.

The improvements were confined to the specific area of the eye where the new genes were injected, said Cideciyan, whose team is funded by the National Eye Institute, one of the U.S. National Institutes of Health.

"There are many steps to go," he said.

It will be difficult to treat the entire retina, he noted. And in LCA, some of the photoreceptor cells are completely destroyed. "The key question is how much and where the remaining photoreceptors are in the eye," Cideciyan said.

Some of the researchers own equity in a company called AGTC Inc that might commercialize some aspects of this work. Wilson, a gene therapy pioneer, has licensed patents related to gene therapy to a number of biopharmaceutical companies.

Both safety and efficacy have held back the field of gene therapy. One experiment cured two French boys with a rare immune disorder but gave them leukemia in 2002, and an Arizona teenager died in a 1999 gene therapy experiment.

(Editing by Will Dunham and Mohammad Zargham)