Gene therapy shows long-term efficacy in clinical trial for rare cause of blindness

Written by Elena Conroy

The results of the trial provide strong evidence that the effects of gene therapy could be permanent and could potentially lead to a single treatment cure for many types of inherited blindness in the future

A team of doctors from the University of Oxford have published the positive results of a clinical trial involving gene therapy for choroideremia, a condition that causes loss of vision in humans. The treatment may pave the way for a cure that could permanently restore sight in people with inherited blindness. The results were recently published in the New England Journal of Medicine.

The therapy involved injecting a virus into the eye to deliver billions of healthy genes to replace the missing gene in the retina that causes choroideremia, a condition characterized by progressive loss of the visual field in young people.

The team examined the vision of six patients up to four years after receiving the therapy at Oxford’s John Radcliffe Hospital. These patients were the world first in getting the procedure for choroideremia in a trial funded by the Department of Health and the Wellcome Trust.

The clinical trial provides strong evidence that the effects of gene therapy could be potentially permanent and could pave the way for a single treatment cure for numerous types of inherited blindness in humans, including retinitis pigmentosa and age-related macular degeneration.

‘There have recently been questions about the long term efficacy of gene therapy, but now we have unequivocal proof that the effects following a single injection of viral vector are sustained. Even sharpening up the little bit of central vision that these patients have can give them considerable independence,” explained Robert MacLaren, lead investigator of the study. ‘Gene therapy is a new technique in medicine that has great potential. As we learn more about genetics we realise that correcting faulty genes even before a disease starts may be the most effective treatment. Gene therapy uses the infectious properties of a virus to insert DNA into a cell, but the virial DNA is removed and replaced with DNA that is reprogrammed in the lab to correct whichever gene is faulty in the patient.”

“In this case, success in getting a treatment effect that lasts at least several years was achieved because the viral DNA had an optimal design and the viral vector was delivered into the correct place, using advanced surgical techniques. In brief, this is the breakthrough we have all been waiting for” added MacLaren.

The treatment was designed to slow and even stop sight loss. Two of the patients successfully experienced a significant improvement in vision that was sustained for at least four years with a decline in their untreated eyes over the same period. A further three patients maintained their vision in their treated eyes throughout this period, whilst a sixth patient who obtained a lower dose experienced a slow decline in vision in both eyes.

Given the long lasting effects of the treatment, it is hoped that patients will be able to undergo the gene therapy during the early stages of the disease to prevent sight loss.

“To permanently restore sight to people with inherited blindness would be a remarkable medical achievement,” commented Stephen Caddick, Director of Innovation at the Wellcome Trust. “This is the first time we’ve seen what appears to be a permanent change in vision after just one round of treatment. It’s a real step forwards towards an era where gene therapy is part of routine care for these patients.”


Thomas L. Edwards, Jasleen K. Jolly, Markus Groppe et al. Visual Acuity after Retinal Gene Therapy for Choroideremia. New England Journal of Medicine, doi: (2016) (Online before print);