Gene Therapy Breakthrough Could 'Cure' Blindness
Patients suffering from an inherited form of blindness
have for the first time had their vision dramatically improved by gene
therapy.
The first six patients to be given the experimental injections into the
back of the eye were all able to see better in dim light.And two of them were able to read more lines on an eye chart.
The patients were born with a genetic form of blindness called choroideremia, which affects 1 in 50,000 people, most of them boys, who start to lose their vision in late childhood.
But in a groundbreaking clinical trial, doctors at the Oxford Eye Hospital injected a harmless virus that had been engineered to carry a working copy of the gene that sufferers lack.
The trial was intended to confirm that the injections did not damage the delicate light-sensing cells in the retina.
But the gene therapy had an unexpected therapeutic benefit - and three more patients have now been treated with a higher dose.
Professor Robert MacLaren of Oxford University, who led the trial, said: "In truth we did not expect to see such dramatic improvements in visual acuity.
"It is still too early to know if the gene therapy treatment will last indefinitely, but we can say that the vision improvements have been maintained as long as we have been following up the patients, which is two years in one case."
The patients were treated in one eye only so doctors could accurately assess the effects of treatment. Results are published in The Lancet medical journal.
Other, more common, genetic causes of blindness, including macular degeneration retinitis pigmentosa, could be treated using the same technique.
Jonathan Wyatt, 65, had his weaker left eye treated as part of the trial and began to notice an improvement in his vision within days.
"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," he said.
"The green of the pitch is greener and the numbers on the shirts are much clearer."
The new procedure involved detaching the retina at the back of the eye and then using a fine needle to inject the genetically modified virus underneath it.
The virus-infected light sensing cells delivered a working copy of the 'CHM' gene. A protein produced by the gene stops the cells dying off.
Professor MacLaren said: "If we were able to treat people early, get them in their teens or late childhood, we'd be getting the virus in before their vision is lost.
"If the treatment works, we would be able to prevent them from going blind."
Wayne Thompson, 43, was treated in April with a higher gene therapy dose as part of a new trial.
He said: "One night in the summer, my wife called me outside as it was a particularly starry evening.
As I looked up, I was amazed that I was able to see a few stars. I hadn't seen stars for a long, long time.
"For a long time I lived with the certainty of losing vision. Now I have uncertainty of whether the trial will work, but it is worth the risk."
The trial was funded by the Health Innovation Challenge Fund, a partnership between the Wellcome Trust and the Department of Health.
Further funds were raised by the Tommy Salisbury Choroideremia Fund through the charity Fight for Sight.
Tommy, now 13, was diagnosed with the condition at the age of five. His family have raised £360,000 to fund research.
His mum Emma said: "It's a mother's worst fear to know that your child has an eye condition that's currently incurable and will cause them to lose their sight."
