New gene therapy improves vision in patients with incurable form of blindness
Published Wednesday, January 15, 2014 10:01PM EST
Researchers in the U.K. have used an experimental gene therapy to restore some vision in patients who are progressively going blind due to a genetic eye disease called "choroideremia."
Researchers at the University of Oxford have treated nine patients who suffer from choroideremia with a new therapy that's designed to replace a defective gene with a healthy one in a single injection.
The results of the first six patients are set to be published Thursday in The Lancet medical journal.
Choroideremia is caused by defects in the CHM gene found on the X chromosome, Oxford's Clinical Ophthalmology group said in a statement.
The missing gene causes the pigment cells in the retina to stop working and eventually die. As the disease progresses, the retina begins to shrink, which causes vision loss.
There is no treatment for choroideremia -- which primarily affects men -- meaning patients progressively lose their vision until they go completely blind. It is estimated that the disease affects 1 in every 50,000 people.
In the published study, six patients with varying levels of vision were injected with a genetically engineered virus carrying a healthy copy of the missing gene. The virus acts as a delivery vehicle, carrying the missing gene to the retina to replace the defective one.
Six months after the treatment, all of the patients had their vision tested.
All the treated patients showed improvements in their vision in dim light, and one-third of the patients were able to read more lines on an eye chart, the researchers found.
Dr. Robert MacLaren, the study's lead researcher, said the initial findings are groundbreaking and can help researchers studying other eye diseases.
"This has huge implications for anyone with a genetic retinal disease such as age-related macular degeneration or retinitis pigmentosa, because it has for the first time shown that gene therapy can be applied safely before the onset of vision loss," he said in a statement.
And while it's too soon to say if the benefits of the gene therapy will last indefinitely, the vision improvements in the six patients have so far been maintained for two years without any side effects, he said.
MacLaren said the research group believes additional treatments may be more effective, and is currently testing higher doses on three patients.
Jonathan Wyatt, 65, was the first patient to receive the gene therapy. He says that since having the treatment, the vision in his left eye has improved.
"Now when I watch a football match on the TV, if I look at the screen with my left eye alone, it is as if someone has switched on the floodlights," Wyatt said in a statement. "The green of the pitch is brighter, and the numbers on the shirts are much clearer."
The results from the Oxford study are giving hope to Canadian researchers, who are getting ready to start their own gene therapy trials.
"There has, to this point, been no other treatment available for these individuals," University of Alberta professor of ophthalmology Dr. Ian MacDonald told CTV News. "We now have something to offer, so it's very exciting."
MacDonald is leading his own gene therapy trial, which will be based in Alberta and will involve 12 patients.
Brantford, Ont. resident Robert Hillier, 63, has choroideremia. He has slowly been losing his eyesight over the past decade and is now considered legally blind.
"Bright sunlight's a problem, glary days are a problem and that small island of sight gets smaller every year," he told CTV News. "(There's) good days, bad days… some days it seems terribly small."
He said he'd be willing to travel anywhere to get the gene therapy, which may be his one hope at recovering some of his vision.
"This treatment has the potential to stop the disease in its tracks," he said. "This gives me hope because it provides the potential that I might not be totally blind in five years."
With a report by CTV News' Medical Correspondent Avis Favaro and Elizabeth St. Phillip