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A new study, published in PNAS, reports the use of gene therapy to improve visual function in a mouse model of retinal degeneration.
Prof. Ian Jackson, Joint Section Head of Disease Mechanisms, MRC Institute of Genetics & Molecular Medicine, University of Edinburgh, said:
“The authors are building on work which aims to treat genetic diseases which cause blindness, by converting cells in the retina which normally have other roles into light-sensing cells. They treat a mouse model of the disease using methods which could be used in humans, and show that there is a some, limited, rescue of vision. Encouragingly this rescue lasts for over a year; most of the lifetime of a mouse.”
Prof. Alan Boyd, President of the Faculty of Pharmaceutical Medicine, said:
“The use of gene therapies to treat inherited genetic diseases of the eye, which cause blindness in children, has seen significant success in recent years. This is shown by one such gene therapy from Spark Therapeutics Inc in the USA, being the subject of applications to both the FDA in the USA and to European Medicines Agency in the EU to be considered for approval as a prescription medicine to treat these childhood eye diseases. However, the gene therapies being developed to treat these terrible eye diseases both in children and adults are of little use once these patients have little sight left and are almost totally blind. This stage of a patients deteriorating eye sight is known as end-stage retinal degeneration and at the moment there are no satisfactory treatments available for them.
“Gene therapies that are currently being developed to treat inherited genetic diseases of the eye, depend upon the presence of particular structures in the eye called rods and cones. These structures act as photoreceptors at the back of the eye in the retina and sense both light and colours, which in turn helps generate electrical signals via the nerves from the eye back to the brain that they help humans see. If patients with genetic diseases of the eye are left untreated, over time, this results in blindness as the rods and the cones deteriorate. In contrast, in this new work done by Professor MacLaren and colleagues, they have identified a possible approach to treating end-stage retinal degeneration using a gene therapy that produces a natural photosensitive protein in the eye, called melanopsin, which does not rely on the presence of rods or cones to be active and could help restore the lost sight in a patient with end-stage retinal degeneration.
“The work performed to date with melanopsin has only involved mice and it will probably take another two to three years at a minimum before a clinical study in humans could be undertaken. However, the work in mice who had end-stage retinal degeneration used the human version of melanopsin and the results showed that its use restored the visual function of the affected mice and it was also restored over a prolonged period up to 13 months. As part of the studies, it was also shown that the nerve pathways from the eye to the brain and, in particular the visual cortex, were stimulated when light was shone in the mouse eyes. These results are very encouraging and could lead to a potential treatment for end-stage blindness in humans.”
* ‘Long-term restoration of visual function in end-stage retinal degeneration using subretinal human melanopsin gene therapy’ by Samantha R. De Silva et al. published in PNAS on Monday 2 October 2017.
Declared interests
Prof. Alan Boyd: “As well as being the President of the Faculty of Pharmaceutical Medicine, Professor Boyd is also the CEO of Boyd Consultants Ltd and provides consultancy advice to several companies and university departments who are undertaking research and development of cell and gene therapies.”
None others received.