A trial investigating the potential for a gene therapy to correct congenital deafness in children and young adults saw all 10 participants gain auditory ability, and allowed them to hear the sound of falling rain or their mother’s voice for the first time ever.
The younger patients, especially those between the ages of five and eight, responded best to the treatment. One of the participants, a seven-year-old girl, quickly recovered almost all her hearing and was able to hold daily conversations with her mother four months afterwards.
Roughly 200,000 people worldwide are deaf due to a mutation in a gene called OTOF, which was the target of the therapy. These mutations cause a deficiency of the protein otoferlin, which plays a critical part in transmitting auditory signals from the ear to the brain.
The gene therapy involved using a synthetic adeno-associated virus to deliver a functional version of the OTOF gene to the inner ear via a single injection through a membrane at the base of the cochlea called the round window.
Hearing improved in all 10 patients, aged between 1 and 24, and the treatment was well-tolerated. The study was conducted in collaboration with hospitals and universities in China and is published in the journal Nature Medicine.
“This is a huge step forward in the genetic treatment of deafness, one that can be life-changing for children and adults,” says Maoli Duan, consultant and docent at the Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Sweden, and one of the study’s corresponding authors.
The effect of the gene therapy was rapid and the majority of the patients recovered some hearing after just one month. A six-month follow-up showed considerable hearing improvement in all participants, the average volume of perceptible sound improving from 106 decibels to 52.
“Smaller studies in China have previously shown positive results in children, but this is the first time that the method has been tested in teenagers and adults, too,” says Dr. Duan. “Hearing was greatly improved in many of the participants, which can have a profound effect on their life quality. We will now be following these patients to see how lasting the effect is.”
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One 7-year-old girl who received a traditional cochlear implant in one ear and the gene therapy in another, went from being functionally deaf to having near-perfect hearing.
Speaking with Gizmodo, Dr. Duan recounts a day when the girl departed his office with her mother after a storm had rolled over the city during their appointment. Walking outside, the girl heard the sound of falling rain for the first time.
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The next part of the trial will be a 5-10 year follow-up to see how long the OTOF gene therapy lasts.
“OTOF is just the beginning,” Dr. Duan said in a statement. “We and other researchers are expanding our work to other, more common genes that cause deafness, such as GJB2 and TMC1. These are more complicated to treat, but animal studies have so far returned promising results. We are confident that patients with different kinds of genetic deafness will one day be able to receive treatment.”
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