One of the world’s longest and largest trials to date has shown remarkable success with an experimental gene therapy that has restored a level of hearing in 90 per cent of people with congenital hearing loss.
The trial, which was carried out across eight centres in China, has treated 42 children (aged between 9 months and 18 years old) and three adults, all with total hearing loss to begin with.
Beginnings of improvement were seen within weeks of the treatment, and progressed slowly, stabilising after around a year.
So far, 10 participants have been tracked for two years or more. All can now hear sounds at normal conversation volume, with some moving onto whispers.
While the treatment was most effective for children, it worked for two of the three adults, indicating that it could be widely effective.
The therapy corrects mutations in the OTOF gene, which makes otoferlin, a protein that translates sound waves into electrical signals for the brain.
By injecting the inner ear with harmless viruses carrying the gene into the hair cells, the researchers were able to reactivate the hearing cells.
This one-time treatment eliminates the need for an external device and regular maintenance, as is the case with cochlear implants.
The majority of individuals had treatment in only one ear, either because they already had an implant in the other ear or because the researchers were unable to treat both ears due to the time constraints of the study.
There were no major safety issues. There were also some minor temporary side effects, such as dizziness or inflammation.
In one case, an 11-year-old girl who had never used an implant was able to speak simple words following treatment.
The researchers now hope to conduct longer studies and test if further doses would improve results.
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