Five children with hereditary deafness have had their hearing restored in both ears through gene therapy in a breakthrough clinical trial.

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The study is the world’s first clinical trial to administer the gene therapy to both ears. It has shown additional benefits from what was observed in the first phase of the trial when children were treated in one ear.

Published in Nature Medicine, the results show that all five children had gained hearing with drastic improvements in speech perception and the ability to locate the source of sounds.

The children participating in the trial were born deaf due to mutations in both copies of the gene for a protein called otoferlin. According to Nature Medicine, the condition known as autosomal recessive deafness 9 (DFNB9) is thought to account for between two and eight percent of children born deaf around the world.

A report from the New Scientist states that the five children’s hearing was at around 50 to 60 per cent of normal levels after six months. Zheng-Yi-Chen of the Mass Eye and Ear hospital in Boston, which led the study, also said as part of this report: “When we whisper, they have a difficult time, but normal conversation is fine.”

The gene therapy works by using a virus called AAV to deliver a working version of the otoferlin gene to the hair cells in the ear. The treatment is administered in one ear at a time, since injecting double doses of the AAV virus into the body could invite greater potential for adverse effects.

The first part of this trial began in 2022, when a separate group of six children were given the gene therapy in one ear only. This resulted in five of the six gaining hearing in the treated ear. They are still continuously improving and the team now plans to treat the other ear of the children in this group.

The trial in China is the first of many taking place around the world, with a child in the UK reported to have gained hearing in one ear after receiving the gene therapy. Further trials are being planned for paediatric patients in the US and Spain.


Further reading

New Scientist: Gene therapy enables five children who were born deaf to hear

Nature Medicine: Bilateral gene therapy in children with autosomal recessive deafness 9: single-arm trial results

The Lancet: Gene therapy proves successful in treating hereditary deafness