In 2016, the European Commission granted market approval to GlaxoSmithKline ( GSK) for ex vivo hematopoietic stem cell ( HSC) gene therapy for the treatment of adenosine deaminase ( ADA)‐deficient severe combined immunodeficiency ( SCID), a very rare congenital disorder of the immune system. Journal reference: The Lancet, DOI: 10.Gene and cell therapy research recently reached a fundamental milestone toward the goal to deliver new medicines for orphan diseases. “The early results of this clinical trial add to the expanding body of experience on the safety of AAV vectors in the eye,” says Bainbridge. Specifically, the new results boost knowledge about the effects of the viral vector used, adeno-associated virus, which has been successfully used in gene therapy for the eye since 2008. The first people to be treated with a gene therapy had ADA-SCID, also called “bubble boy disease”, and some later got leukaemia, probably because the virus carrying the new genes also switched on cancer genes. MacLaren’s work is part of a broader trend in the success of gene therapy, which got off to a bad start. That’s one of the distinguishing features between stem cell therapy, which is to regenerate lost tissue, and gene therapy, which at the moment is there to sustain cells that would otherwise die.” “What we can’t do is bring back the cells that have already gone. “We’re trying to rescue the cells that are there already, to return the function of those cells to normal,” says MacLaren. The treatment also can’t replace cells that have been completely destroyed. “Given the relatively slow degeneration in this condition, longer-term studies will be required,” says James Bainbridge of the Institute of Ophthalmology at University College London. Wyatt had the treatment first, so can reveal that the benefits seem to last two years, but he’s just one case. Still, the long-lasting effects of the treatment remain unknown. By contrast, the MacLaren team’s therapy targets photoreceptors that are neurons lasting for life – so in principle patients need only have the treatment once. However, in this case the target cells were pigment ones, which eventually die off to be replaced by new ones. It’s not the first time gene therapy has been used to improve vision: it has also been used to restore vision in people with the retinal disease Leber’s congenital amaurosis, for example. However, MacLaren is hopeful that the therapy could also be used to stop choroideremia before there is any significant loss of vision. “The very next day I saw a mobile phone and I said ‘I can read the digits!’ I hadn’t been able to read the digits on a mobile phone for five years,” says Wyatt.Īll the people in this trial had varying levels of degeneration before the treatment. Today the team reports that of the six people who received the treatment six months ago or longer, all have described improvements in their vision. Starting two years ago with Wyatt, they injected a virus carrying a corrective copy of the CHM gene into the retinas of people with choroideremia. Robert MacLaren of the University of Oxford and his colleagues decided to see if it could correct choroideremia. Neurons for lifeĮnter gene therapy, which uses a vector – usually a virus – to insert a functioning copy of a gene into cells with a gene defect and could in principle be used to treat many genetic conditions. When he was in his twenties, doctors told Wyatt that he would be blind by the time he was 50 – and that there was no cure. In those who have the disease, a lack of REP-1 means that cells in the retina stop working and slowly begin to die off, causing blindness. Choroideremia is caused by defects in the CHM gene, which produces a protein called REP-1 and affects one in 50,000 people.
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