Researchers from Karolinska Institutet and hospitals in China have successfully restored hearing in patients with congenital deafness using gene therapy. Published in Nature Medicine, the study reports improvement in all ten participants with OTOF gene mutations.
“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.
How the Gene Therapy Procedure Works
The patients, aged between one and 24 years, were treated at five hospitals in China. Each had a mutation in the OTOF gene, which causes a deficiency in the protein otoferlin — a key element in transmitting sound signals from the ear to the brain.
The treatment involved a single injection of a functional OTOF gene, delivered using a synthetic adeno-associated virus (AAV). The injection was administered through the round window, a membrane at the base of the cochlea.
According to researchers, the delivery method was precise, minimally invasive, and marked by rapid results.
Rapid Hearing Gains Within Weeks Post-Treatment
The effects of the gene therapy were seen quickly. Most patients had regained some hearing within one month. All participants demonstrated substantial progress, with average sound perception improving from 106 decibels to 52 decibels by the six-month mark.
“Hearing was greatly improved in many of the participants, which can have a profound effect on their life quality,” said Dr Duan. “We will now be following these patients to see how lasting the effect is.”
Children Show Best Outcomes and Adults Benefit Too
The study found that children aged 5 to 8 responded best to the therapy. One particularly notable case involved a seven-year-old girl who recovered almost all her hearing within four months. She is now able to engage in daily conversations with her mother.
“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,” Dr Duan added.
The study’s success in adults is a pioneer for this type of therapy and broadens its future applicability.
Positive Safety Profile and Minimal Side Effects
The treatment was found to be safe and well-tolerated. The most common side effect reported was a temporary reduction in neutrophils, a type of white blood cell. Importantly, no serious adverse reactions were observed during the 6 to 12-month follow-up.
Expanding to Treat Other Genetic Causes of Deafness
“OTOF is just the beginning,” said Dr Duan. “We and other researchers are expanding our work to other, more common genes that cause deafness, such as GJB2 and TMC1.”
While the other genes are more complex to treat, early results from animal studies have been encouraging. Researchers emphasise that human applications will require rigorous trials. The study was supported by several Chinese research programmes and Otovia Therapeutics Inc., the company that developed the gene therapy and employs many of the scientists involved.