StemCell Therapy

Alberta has become the first province in Canada to use new gene therapy to treat a rare and debilitating genetic eye disease.

The first three patients two young children and an adult received the treatment Dec. 14 at the Royal Alexandra Hospital in Edmonton.

The Royal Alex is the first of four places in Canada that will offer the gene therapy.

It will give people who previously have been relegated to seeing life getting increasingly blurred and eventually dark a brighter future, said Dr. Matthew Tennant, a clinical professor at the department of ophthalmology and visual science at the University of Alberta.

Tennant was one of the doctors who conducted the surgeries.

"All those people who now are relegated to continue to lose vision throughout their lives they will have hope and they will have the possibility of stability," he said.

"The next generation of people with retinitis pigmentosa will have treatment when they're born, or early in their lives, so that their vision will be normal. They'll never have deterioration."

The gene therapy involves a drug called Luxturna, developed by the American biotech company Spark Therapeutics.

Luxturna treats an aggressive form of retinitis pigmentosa, a group of diseases caused by some 300 gene mutations that all involve the retina and cause progressive decline and loss of vision.

The type of retinitis pigmentosa treated by Luxturna is caused by a faulty gene called RPE65.

When the gene malfunctions, photoreceptors stop working over time.

Photoreceptors are the cells in the retina that convert light into electrical signals that get sent to the brain, which allows people to see.

Photoreceptors are kept alive by an underlying layer of cells called retinal pigment epithelium. When the RPE65 gene doesn't work properly,the cells in the retinal pigment epithelium and photoreceptors don't work correctly.

Photoreceptors don't get enough nutrition and can't process and eventually they die.

Luxturna helps replace the malfunctioning gene with a normal one.

"It involves delivery of a healthy copy of a gene like RPE65 into the retinas," said Shannon Boye, a professor and associate chief of the division of cellular and molecular therapy at the University of Florida.

"Once inside the retina, that healthy gene will go on to make a healthy protein that can then go on to interact properly with all of the other proteins in the retina and ultimately restore the patient's ability to process light into an electrochemical signal" and see normally, she said.

The healthy gene is delivered into the cell using a modified virus. Scientists have managed to rip the original DNA out of a virus and replace it with the healthy gene.

When the virus makes its way into the cell, the faulty gene is switched off. The cell begins to function normally and photoreceptors receive enough nutrients.

"There is some ability to save damaged cells that have not died, but we are not able to fix all that have already gone. It doesn't replace dead cells, so that means that early treatment is the way for maximum success," Tennant said.

The treatment is performed by injecting the modified therapeutic viruses between the retina and the retinal pigment epithelium. This requires significant surgical skills the space between the two is only two or three microns. There, the viruses are injected into the fluid pocket.

Gene therapy is expensive. It costs $1 million to treat both eyes with Luxturna. However, it is a one-time procedure, and the fix is permanent.

The disease that this gene therapy treats is extremely rare. There are probably just 300 people in Canada who have it, said Dr. Ian MacDonald, an ophthalmologist and AHS Edmonton Zone clinical chief of ophthalmology.

"We would estimate that we would treat one new Albertan every year," said MacDonald, who noted that patients from across Western Canada will be treated at the Royal Alex.

There is no waiting period for Albertans to receive Luxturna and there are no out-of-pocket expenses, said Charity Wallace, assistant director for communications at Alberta Health, in an email.

Using gene therapy to treat hereditary eye disease has shown the medical and commercial viability of gene therapies, Boye said.

"I think that every one of these therapies that gets approved is going to bring our regulatory agencies to a point where they're more and more comfortable with this type of medicine becoming mainstream."

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New gene therapy to treat rare eye disease now available in Alberta ...

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