Can gene therapy help restore sight? – new research
Gene therapy is a growing field of research but there are many challenges to overcome before research reaches patients as routine treatment. The Wellcome Trust’s Technology Transfer Division aims to help bridge the gap from concept to clinic by funding early stage trials that might not otherwise secure investment. The Wellcome Trust/Department of Health Health Innovation Challenge Fund (HICF) is one way we do this, and today’s publication of results from one of the funded trials show some exciting results.
Choroideraemia is an inherited form of blindness affecting 1 in 50,000 – 100,000 people. The limited occurrence of this disease leaves it somewhat neglected by pharmaceutical companies and larger funding bodies. Although uncommon, choroideraemia has a major impact on quality of life and is thought to account for four per cent of all blindness.
Results from an HICF-funded phase I clinical trial using gene therapy to treat patients with choroideraemia indicated that delivering healthy copies of the defective gene into the eyes of affected patients could restore their vision.
“I could see the digits on my wife’s phone” explains choroideraemia patient Jonathan Wyatt, 65. “I hadn’t been able to see them for years”.
Wyatt, a barrister from London, was diagnosed with the condition in his 20’s. Since then, both his vision, and ability to work, have deteriorated.
Choroideraemia is caused by a single-gene default in a gene located on the X chromosome. Men only have one X-chromosome so the condition mainly affects them since women can carry a healthy copy of the gene on their second X-chromosome. CHM/REP-1, the gene responsible, controls the health of light-sensing cells in the retina of the eye and if mutated, night vision can be impaired as early as childhood. Visual impairment then progresses to further narrow the field of vision.
“There was a watery blur in the centre of my vision” explains Wyatt. “So much so, that if I waved my hand down in front of my eyes I couldn’t see it anymore”. His only option for treatment was a gene therapy trial being conducted at the University of Oxford, funded by the HICF.
Professor Robert Maclaren, of the Nuffield Laboratory of Ophthalmology at the University of Oxford, tested a novel method of gene therapy. His team used adeno-associated viruses (AAV) to deliver healthy copies of the CHM/REP-1 gene to the deteriorated light-sensing cells of the retina. Delivery was achieved by detaching one of each patients’ retinas and injecting the DNA-carrying viruses underneath (the other retina acted as a control).
This phase I trial is very small, with twelve patients, only six of which are included in the initial results published in The Lancet, so although they are encouraging, the results should be interpreted with caution.
Participants in the trial had varying levels of visual acuity, measured by reading the lines of letters found on a sight chart. The results show that the choroideraemia patients who had excellent, or good, acuity at the start had no deterioration after therapy and their ability to see in the dark was improved.
The two patients with reduced acuity at the starts of the trial saw improvements in their vision. These improvements have been sustained for six months after initial therapy.
“We’ve only treated nine people altogether, so it’s right to have reservations. This is in no way a cure” warns Maclaren. “What’s really exciting is that the improvement seen in these two patients is not a blip that then drops. Their vision is maintained”.
There is still more work to be done and Maclaren’s team are now applying for funding to take the trial on to Phase II.
Dr Tim Knott, Business Development manager at the Wellcome Trust is delighted by the progress so far. “This was one of the first projects funded through THE HICF and it’s typified the goals and aims of that objective when it was set up”.
“Gene therapy was on the list of things that we probably wouldn’t consider funding under this scheme as it was deemed too long-term and too risky” adds Knott. “But Professor Maclaren convinced us it was doable, and the right time to take this risk, and he has proven to be correct”.
The Health Innovation Challenge Fund was set up by the Wellcome Trust and the Department of Health to invest in research that commercial companies won’t take a chance on. It has the specific intent of acting as a technology accelerator to move promising research projects form the laboratory into early clinical use.
39 funded projects are in the first phase with some already benefitting patients in the NHS. More information can be found at http://www.wellcome.ac.uk/funding/technology-transfer/awards/health-innovation-challenge-fund/index.htm.