Clinical trials of gene therapy for inherited blindness have shown promising results. Research from the Oxford University, published in the New England Journal of Medicine, has shown promising results for the use of gene therapy in treating choroideremia, a rare form of inherited blindness affecting around 1 in 50,000 people.
Choroideremia is caused by the mutation of a gene inherited from parents. It almost exclusively affects males. The trial involved inserting the correct version of the gene into the patients’ DNA using a virus. The virus, modified to carry and insert the gene in the correct location, was injected into the back of the patients’ eyes. Only one eye was treated for each participant, with the other serving as a comparison.
Although Gene therapy is the subject of much research, difficulty frequently arises from ensuring that the viral vector is delivered to the correct place and ensuring that the new gene is successfully incorporated into the patients’ DNA.
“Optimal design and the viral vector was delivered into the correct place using advanced surgical techniques.”
The viral vector used was the common adeno-associated virus but according to Professor Robert MacLaran, the lead investigator in the study, the success was down to “optimal design and the viral vector was delivered into the correct place, using advanced surgical techniques”.
The promise of the investigation is largely due to the fact results of the trial were achieved over a three and a half year period. Maclaran, who has a patent for ‘AVV – a vector for use in gene therapy of choroideremia’, has commented that“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.” While this trial is far off providing unequivocal proof, it does provide some hope for the future direction of similar trials.
A potential limitation of this trial is that choroideremia is a rare disease with a relatively simple pattern of inheritance. Whether, as reported elsewhere, this offers much hope for treatment of far more complex diseases such as muscular degeneration is uncertain.
Nonetheless, for some of the participants suffering from this disease it has improved their quality of life. According to the Daily Mail, Joe Pepper began to lose his sight in his early teens. After receiving the first injection at the John Radcliffe hospital in Oxford he is reported to have said “For the first time in my memory, I read on and on. I laughed and shed a tear. I will remember that day for the rest of my life.”