Will gene therapy be an effective treatment for blinding eye diseases? Many people who live with vision loss are waiting for an answer, while scientists and clinicians are testing a variety of different gene therapy approaches. The latest results, published in the reputable New England Journal of Medicine, provide the strongest evidence to date about the positive long-term effects of gene therapy.
There is tremendous potential for gene therapy and gene editing to treat a variety of blinding eye diseases (read this story for a general overview). Basically, gene therapy involves delivering healthy genes to the eye to replace the function of a mutated gene. In this study, the mutated gene (CHM) leads to the rare blinding eye disease, choroideremia.
These latest results examined the vision of six clinical trial participants, 3.5 years after they received the gene therapy. These pioneering participants were the first people in the world to undergo this procedure at Oxford’s John Radcliffe Hospital.
The clinical trial was designed to slow or stop vision loss in people living with choroideremia. Amazingly, two of the patients experienced significant and sustained improvement in their vision, despite a decline in their untreated eyes over the period. Three of the other trial participants maintained vision in their treated eyes throughout the period. However, it should be noted that these same patients also maintained vision in their untreated eyes. The sixth patient, who was given a lower dose, showed a slow decline in vision in both eyes.
Thanks to donors, the Foundation Fighting Blindness is proud to help support the Canadian arm of this trial, which is led by Dr. Ian MacDonald at the University of Alberta. The Canadian trial started last summer. Dr. MacDonald is planning to share the first-year result in July, 2016. Although, we are very hopeful, that the participants in Dr. MacDonald’s trial will also experience sustained visual gains, it is critically important to remember that a clinical trial is an experiment that is designed to test if a new treatment is safe and effective in people. Clinical trials are also designed very carefully to ensure that the results are reliable. This is critically important because reliable results help to ensure that promising new treatments can make their way through clinical trials and eventually into the marketplace where they can be accessed by the patients who need them.
Dr. MacDonald is ensuring that the Canadian trial learns from the Oxford study by collaborating closely with Professor Robert MacLaren, who leads the Oxford study. Indeed, Professor MacLaren traveled to Alberta to help with the Canadian clinical trial. Professor MacLaren explains that these latest clinical results are particularly meaningful because “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… this is the breakthrough we have all been waiting for.”
At the Foundation Fighting Blindness, we are certainly celebrating this latest breakthrough! Thank you to all of the donors who helped to bring this trial to Canada.