Gene therapy to be trialled against hereditary blindness at Addenbrooke’s in Cambridge and Moorfields in London
Addenbrooke’s doctors are leading efforts to trial gene therapy against hereditary blindness.
They are recruiting patients with a disease called Leber hereditary optic neuropathy (LHON), which is caused by a gene mutation in the mitochondrial genome.
It triggers the rapid loss of vision, and primarily affects young adults.
Although classified as a rare disease, it is estimated to affect at least 1 in 30,000 people in the UK. Women and children can be affected, but the majority of cases occur in young men between the ages of 15 and 35.
Dr Patrick Yu Wai Man, Addenbrooke’s honorary consultant ophthalmologist, and his team are planning a trial in Cambridge and at Moorfields Eye Hospital in London that is designed to help us understand the disease better and determine whether gene therapy can restore some sight in people affected by it.
“Your eyes are the greatest camera you’ll ever own and this disease is a devastating blow to people,” he said.
“You can go from being fit and well and then suddenly, within weeks, your vision deteriorates rapidly, and you are told you can be registered as blind.
“We know that this disease is hereditary and affects mostly young men. But there are still so many unanswered questions about this condition and we need to find out more in order to identify suitable treatments.
“Our recent research, published in Science Translational Medicine, is promising, indicating that patients with LHON who have experienced loss of vision for up to one year can benefit from gene therapy.
“We now want to focus on people who have had this condition for more than one year and that is the basis of our trial.”
The mitochondrial genome is a unique piece of circular DNA that we inherit from our mother.
It is mutations in this that cause LHON, leading to the loss of healthy cells in the retina, optic nerve damage and severe loss of vision.
Most people are unaware that they carry a LHON mutation until they develop symptoms, beginning with blurred vision, or if a family member is diagnosed with the condition.
It is currently a mystery why it starts so abruptly and why it mostly affects young men.
There are limited existing treatment options for patients.
Funded by an NIHR Moorfields Eye Charity Advanced Fellowship and supported by the NIHR Cambridge Biomedical Research Centre (BRC), the new trial will use a form of gene therapy in patients with chronic LHON, who have lost their vision for between one and five years.
The gene therapy will involve inserting a healthy version of the gene into cells in the retina using a harmless virus.
Dr Yu Wai Man said: “We know the disease quickly kills off healthy cells in the retina and we want to try and bring as many cells as possible from the brink to prevent further sight loss and potentially improve vision. In the pilot phase, we plan to recruit 30 patients who will be split into two equal groups.
“One group will receive the gene therapy injections in both eyes whereas the second group will not receive the treatment. The patients will then be closely monitored over two years to see if the treatment improves their eyesight.
“If we are successful, this breakthrough could be life-changing and it will also provide hope to people with visual impairment from other genetic diseases that affect the optic nerve.”
Dr Yu Wai Man said the funding for the project was invaluable.
“Without this level of commitment for rare diseases from the NIHR, we wouldn’t be able to conduct this kind of trial to try and save people’s sight,” he said.
“I’m very excited about what we’re going to learn and achieve in the next few years working closely with patient organisations.
“We may not be able to restore normal sight 100 per cent, but if we could improve vision enough to have a positive impact on someone’s quality of life, that is the most important thing.”
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