First Canadian gene therapy trial for blindness sees positive results

WATCH ABOVE: A trial by Edmonton doctors hopes to transfer human genes to help those with choroideremia. Su-Ling Goh reports.

EDMONTON – The first four patients in Canada’s only gene therapy trial for blindness say their vision has improved. All four of the Edmonton-area men have choroideremia, an inherited disorder that usually leads to legal blindness by the age of 40.

Ken Ross, 43, underwent the procedure on his right eye on May 25, after what he describes as decades of “looking through a pinhole.” He says when doctors removed the bandage two days later the room seemed instantly brighter. And the view outside was better than ever.

“You can actually see the different colours, especially in the flowers and grass,” says Ross, smiling.

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Ocular gene therapy involves replacing the patient’s faulty gene with a functional copy of it. The new gene is carried inside a harmless virus, and injected to the back of the eye. That’s where the virus injects its DNA into the retinal cells, causing them to produce the protein needed for a healthy retina.

For clinical research team leader Dr. Ian MacDonald, the goal was to preserve any remaining vision in patients. But the results have been even better than expected.

“To date, we’ve been told by the patients that they actually see sharper, using the eye that’s been treated,” says MacDonald, an ophthalmologist with Alberta Health Services.

Two more patients will undergo the procedure at the Royal Alexandra Hospital next week.

The team’s genetic counsellor, Stephanie Chan, says choroideremia affects about one in every 50,000 people, about 90 per cent of whom are men. Patients have been asking for gene therapy for years.

“They start thinking about all the things that they might be missing out on in the future,” explains Chan. “If they have families, they might not be able to see their loved ones anymore.”

Ross’ mother Judy broke the news that he was going blind at age 12. Both hope future choroideremia patients won’t have to experience similar heartbreak.

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“I’m doing [the trial] so that any mother doesn’t have to sit down and have that conversation with their child, saying, ‘Your life is going to change drastically. You might not be able to do what you think you’re going to be able to do,'” says Ross.

The Edmonton study was phase one of a clinical trial to prove the technique is safe, the third study of its kind in the world.

Gene therapy also has potential to treat age-related macular denegeration, retinitis pigmentosa and Usher syndrome.

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