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Gene therapy looking good for inherited blindness

16 January 2014
Appeared in BioNews 738

Gene therapy for an eye condition called choroideremia is safe and has improved the vision of six patients, says a study in the Lancet.

'This trial is the first application of gene therapy to neurons in the retina', said Robert MacLaren, professor of ophthalmology at the University of Oxford, who led the study. 'Our findings hold great promise for gene therapy to prevent loss of sight in other retinal diseases'.

Choroideremia is a condition where the retina degenerates and vision gets progressively worse, and it affects one in 50,000 people. It is caused by mutations in a single gene, CHM, which is present on the X chromosome, meaning the condition affects mostly men.

In this study, the CHM gene was carried into the body using a harmless virus, where it then produced the REP1 protein necessary for retinal cells to function properly.

In an operation that took less than an hour, surgeons carefully detached the retina from the back of the eye before injecting the virus underneath it.

The first person to undergo the procedure, Jonathan Wyatt, 65, had lived with worsening vision for more than 40 years. 'My eyesight has improved enormously after the operation', he said.

'Before the operation, I had to work hard to read 17 letters on the Snellen [eyesight] chart. Six months afterwards, I could manage 42 letters', Wyatt said.

Toby Stroh, 56, received treatment in February 2012. 'Immediately after the operation, I could see another couple of lines on the sight chart', he said.

'For the last 30 years, I'd been living under the awful, insidious inevitability of going blind, and now as a result of this work, there's a very real prospect that I will continue to be able to see', Stroh added.

In people with choroideremia, the retina gradually gets smaller as cells die off. Light-sensing cells in the retina cannot divide, so new cells cannot be made. However, this could be an advantage in gene therapy, as genes from the one-off injection will remain within their target cells, meaning effects should be long-lasting.

'It is still too early to know if the gene therapy treatment will last indefinitely, but we can say that the vision improvements have been maintained for as long as we have been following up the patients, which is two years in one case', said Professor MacLaren.

The researchers are now testing a higher dose of the gene-carrying virus in a further six patients.

There are 195 known genes linked to retinal degeneration, and around one-third of eye disorders are genetic in nature. The researchers hope that similar therapies can be developed for more complex eye disorders such as age-related macular degeneration and retinitis pigmentosa.

'This is an exciting scientific development and a step in the right direction for treating retinal diseases with gene therapy; however, it is early days yet', Clara Eaglen, eye health campaigns manager at the Royal National Institute for the Blind told BioNews.

'The findings are positive and do support the case for conducting more research in this area but extensive trials would be needed to establish efficacy and safety', she added.

21 November 2016 - by Paul Waldron 
Scientists in the US have used a genome-editing technique to partially restore vision in blind rats...
3 May 2016 - by Sarah Gregory 
A trial of gene therapy for choroideremia, a rare form of inherited blindness, has partially restored the vision of several patients...
15 December 2014 - by Dr Rosie Morley 
Scientists have used gene therapy to restore some sight to animals with visual impairment similar to retinosa pigmentosa, a type of human blindness...
20 October 2014 - by Jenny Sharpe 
Retinal cells derived from human embryonic stem cells have been safely transplanted into the eyes of patients with currently incurable sight loss...
16 June 2014 - by Alice Plein 
In a research first, a section of light-sensing tissue, closely resembling the human retina, has been grown in the laboratory from human stem cells...
29 July 2013 - by Dr Greg Ball 
Light-sensitive cells found in the retina have been grown from mouse embryonic stem cells (ESCs) and successfully transplanted into the eyes of visually impaired mice, restoring some vision...
17 June 2013 - by Rhys Baker 
A 'non-invasive' method for delivering gene therapy into the eye has been developed by US researchers...
13 February 2012 - by Dr Maria Botcharova 
Three women have reported a significant improvement in sight following gene therapy in both their eyes. Initially, they received the therapy in just one eye, but this latest study demonstrates the treatment was also successful in the other...
31 October 2011 - by Victoria Kay 
A British man has become the first person to receive an advanced gene therapy treatment in a bid to save his sight. Jonathan Wyatt, aged 63, is the first of 12 patients to have the experimental procedure to try and halt the progression of his genetic eye disorder, choroideraemia. While he still has some sight, if left untreated, he would eventually become blind...
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