Gene therapy helps deaf teen, 24-year-old hear for first time in new study
A new study has shown that gene therapy can restore hearing not just in children but also in teenagers and adults born with genetic deafness. The research was led by scientists from the Karolinska Institutet in Sweden, in collaboration with hospitals and universities in China.
“This is a huge step forward in the genetic treatment of deafness, one that can be life-changing for children and adults,” said Maoli Duan, a consultant and docent at the Department of Clinical Science, Intervention and Technology at the Karolinska Institutet, and one of the study’s corresponding authors.
The study focused on a rare type of congenital deafness caused by mutations in the OTOF gene. This gene is responsible for producing a protein called otoferlin, which plays a vital role in sending sound signals from the ear to the brain. Without it, affected individuals are born unable to hear.
To deliver a healthy version of the OTOF gene, researchers used a synthetic adeno-associated virus (AAV). The virus was injected through a membrane at the base of the cochlea, a key part of the inner ear. The effect was almost immediate. Most patients showed signs of hearing recovery within a month.
By six months, all ten patients had significantly improved. The average volume at which they could detect sound dropped from 106 decibels to 52—meaning they went from profound deafness to being able to hear sounds at a normal conversation level.
Best results seen in young children, but adults also benefit
Participants in the study ranged from one to 24 years old and were treated at five hospitals in China. While previous studies had shown good outcomes in children, this is the first trial to show that teenagers and adults can also benefit from the therapy.
Duan noted that the most remarkable results were observed in children aged five to eight. A seven-year-old girl who received the therapy in one ear—and had a cochlear implant in the other—recovered nearly all of her hearing. Within four months, she was talking with her mother daily. “The girl told her mother she could hear the sound of rain for the first time,” the researcher shared.
Even the oldest participants, aged 14 and 24, experienced notable improvements. That surprised Lawrence Lustig, a neurotologist at Columbia University Irving Medical Center who was not involved in the study.
“I think most of us thought going into this that the older you are, the worse the hearing results are going to be,” Lustig told Gizmodo. While earlier research had shown some gains in children up to 12, “I don’t think anyone’s seen anything [in patients] as old as 24 years,” he added.
A safe therapy and a hopeful future
Importantly, the treatment was well-tolerated by all participants. No serious side effects were reported during the six to twelve-month follow-up period. The only mild reaction noted was a temporary drop in neutrophils, a type of white blood cell.
“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,” said 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.”
Duan and his team plan to continue monitoring the patients for five to ten years to better understand the long-term durability of the treatment. While the therapy for OTOF-linked deafness is still in development, this study adds strong support for its clinical use.
“OTOF is just the beginning,” he emphasized. “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.”
Worldwide, approximately 200,000 people are estimated to be deaf due to mutations in the OTOF gene. Until recently, cochlear implants were the only option. This new approach could soon offer a powerful alternative, especially for young children just learning to speak. It may also help adults who have never heard a sound before.
Source: Interesting Engineering
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Gene therapy helps deaf teen, 24-year-old hear for first time in new study