Gene treatment promising in fight against degenerative blindness

LOS ANGELES (KABC) -- People with choroideremia are born with perfect vision and then begin to lose their sight, sometimes as kids or teens. Researchers in the United States are now building on the success of a clinical trial overseas and are about to test a therapy designed to halt the progression of the disease and maybe even reverse some of the damage.

In bright daylight, 10-year-old Mark Devoe has no trouble seeing his friends. But inside or even in the shade, Mark's eyes sometimes don't work.

"I have trouble seeing like, trees, when the road ends, and when there's like a drop there," said Mark.

At age 6, Mark's doctors diagnosed him with the genetic condition choroideremia, which causes people to progressively lose vision until they are completely blind.

"I don't know what it's like to live in darkness, but I've seen it," said Susan Devoe, Mark's mother.

Susan is a carrier of the blindness gene. Mark's grandfather has the condition.

"Watching my father go blind was devastating," said Susan. "I was a little girl. You know, you count on daddy to do things, and daddy couldn't do them."

Dr. Jean Bennett is one of two U.S. researchers preparing to test a gene therapy for choroideremia in humans.

"I think gene therapy holds a huge promise for developing treatments for blinding diseases," said Bennett.

Researchers will use a virus carrying a small choroideremia gene and inject the virus just under the retina. The gene should begin to work in a few weeks.

In a trial of six patients in the United Kingdom, all six had better low-light vision six months after the therapy. Two of the six could read more lines on an eye chart.

Dr. Bennett says early success in the U.K. is encouraging.

"If we can prevent the disease there from continuing, it would change people's lives," said Bennett.

"I want my son cured. I want to see all these guys who it breaks my heart to see walking around a conference with white canes," said Susan Devoe. "I want them to have freedom."

Bennett says the first U.S. clinical trial will enroll 12 adults and is designed to test the safety of the gene therapy. Bennett says she hopes to expand the trial to include children and teens.