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Gene therapy raises hopes for the blind

Latest update : 2008-04-28

Scientists in Philadelphia and London injected solutions containing healthy genes into the eyes of patients affected by degenerative diseases that lead to blindness. They say first results provide encouraging evidence of restoring partial vision.

An experimental gene therapy has helped restore partial vision to people with congenital retinal disease, according to breakthrough studies which provides hope for treating various eye illnesses.

Clinical trials showed success on three young adults at Children’s Hospital of Philadelphia who suffered from a rare and as yet incurable form of congenital blindness, according to studies published Sunday.

The retinal degenerations include Leber congenital amaurosis, or LCA, a group of diseases that affect light receptors in the retina beginning in early childhood and often causing total blindness in patients in their twenties or thirties.

"This result is important for the entire field of gene therapy," study leader Katherine High was quoted as saying in the New England Journal of Medicine whose website reported the findings by a collection of international doctors and scientists.

"Gene transfer has been in clinical trials for over 15 years now, and although it has an excellent safety record, examples of therapeutic effect are still relatively few," High said.

"The results in this study provide objective evidence of improvement in the ability to perceive light, and thus lay the groundwork for future studies in this and other retinal disorders."

Scientists used a genetically engineered virus as a vector to carry millions of copies of a normal version of the gene known as RPE65 to the patients'retina via surgical procedures performed between October 2007 and January 2008.

A mutation of this gene that normally makes a protein needed by the retina which senses light and sends images to the brain, is responsible for a gradual lost of sight until the patients are blind.

About two weeks after the surgery all three patients, age 19, 26 and 26, reported improved vision in the injected eye, and became approximately three times more sensitive to light than in the other eye, according to study co-author Albert Auricchio from the Second University of Naples, in Italy.

"Standard vision tests showed significantly improved vision in the patients," Auricchio said.

Their vision "improved from detecting hand movements to reading lines on an eye chart," said Albert Maguire, associate professor of opthalmology at the University of Pennsylvania School of Medicine.

In 2001 Maguire and his wife Jean Bennett were part of a team which reported successfully using gene therapy to reverse blindness in dogs affected by the same congenital blindness.

A separate clinical trial parralel to the Philadelphia study was conducted at Britain's University College London, also on three young adults, with one 18-year-old patient showing improved visual function.

Researchers of that study concluded that there were no major adverse effects of the so-called Adeno-Associated Virus (AAV) treatment.

"Of course, additional studies are needed in order to assess this approach fully, including the expansion of the study to include younger children, but these initial results suggest that AAV-based delivery of genes in the eye can be accomplished," said research co-author Barrie Carter, executive vice president of Targeted Genetics.

Researchers said they expect more pronounced improvements if treatment occurs in childhood before the disease progresses.

Bennett said on the grounds of its initial success, the clinical trial will continue with additional patients and follow-up study of the results.

Date created : 2008-04-28