NEW YORK — Scientists for the first time have used gene therapy to significantly improve sight in people with a rare form of blindness, a development experts called a major advance for the experimental technique.
Some vision was restored in four of the six young people who got the treatment, teams of researchers in the United States and Britain reported Sunday. Two of the volunteers who could see only hand motions were able to read a few lines of an eye chart within weeks.
“It’s a phenomenal breakthrough,” said Stephen Rose, chief research officer of the Foundation Fighting Blindness, which helped pay for one study done at Children’s Hospital of Philadelphia.
If successful in larger numbers, experts said, the technique has the potential to reverse blindness from other kinds of inherited eye diseases.
The research was published online Sunday by the New England Journal of Medicine in conjunction with presentations at a meeting in Florida.
The two teams of scientists, working separately, each tested gene-replacement therapy in three patients with a form of a rare hereditary eye disease called Leber’s congenital amaurosis. There’s no treatment for the disease, which appears early in infancy and causes severe vision loss, especially at night. An estimated 2,000 Americans have the specific form of the disease that the researchers targeted.
Each of the study participants had mutations in a gene that makes a protein needed by the retina, which senses light and sends images to the brain. Those without the gene gradually lose sight until they are blind in early adulthood.
The retina itself stays in relatively good shape for a while, making it a good candidate for gene therapy, said Robin Ali, a professor at University College London who led the British team. He likened the defective gene to a missing spark plug in a car engine.
“The whole engine can be absolutely fine, but if it doesn’t have a spark plug, the car’s not going to work,” Ali said.
For the experiment, the scientists injected millions of copies of a working gene beneath the retina in the back of the eye. Only one eye was treated — the worst one — in case anything went wrong; the untreated eye was used for comparison. After the treatment, the patients’ eyesight and light sensitivity were measured periodically; mobility was tested in a maze or an obstacle course.
All three of those treated in Philadelphia showed significant improvement in their vision, the researchers said. The volunteers — two women, 19 and 26, and a man, 26 — were from Italy. The longest follow-up was six months.
Besides reading lines on an eye chart, they could see better in dim light, said Dr. Jean Bennett, a professor of ophthalmology at the University of Pennsylvania and a leader of the Philadelphia study.
In the British group, the treatment worked only for 18-year-old Steven Howarth, whose disease was less advanced than the other two — a girl, 17; and a man, 23, who was followed for a year.
Howarth said he used to rush home from school because he was worried about getting around in the dark, according to remarks issued by the university.
“Now, my sight when it’s getting dark or it’s badly lit is definitely better. It’s a small change — but it makes a big difference to me,” Howarth said.
There were no serious side effects reported in either group. The researchers said there was no evidence that the altered virus used to ferry the gene into the retina’s cells had traveled outside the eye to other areas of the body.
The National Eye Institute is funding a third similar study at the University of Florida.
