New research shows that gene therapy can significantly improve hearing in people born with congenital hearing loss or severe hearing loss. Researchers at Karolinska Institutet, in collaboration with hospitals and universities in China, treated 10 patients and found improved hearing in all cases. Treatment was also well tolerated. The research results were published in a magazine natural medicine.
“This is a major advance in the genetic treatment of hearing loss and has the potential to change the lives of children and adults,” says Maori Duan, a consultant and PhD in the Department of Clinical Sciences, Interventions and Technology at Karolinska Institutet in Sweden and one of the study’s corresponding authors.
Targeting the OTOF gene
The trial involved 10 patients aged 1 to 24 who were treated at five hospitals in China. All had a genetic hearing loss linked to a mutation in a gene called OTOF. These mutations cause the body to not produce enough otoferrin, a protein essential for sending sound signals from the inner ear to the brain.
Get instant results with just one injection
To address this, researchers used a synthetic adeno-associated virus (AAV) to deliver a functional version of the OTOF gene directly into the inner ear. The treatment was given in a single injection through the membrane at the base of the cochlea, known as the round window.
The effects were immediate. Most patients begin to regain some hearing within a month. After six months, all participants showed clear improvement. On average, the level of detected sound increased from 106 decibels to 52 decibels.
Largest increase seen in younger patients
Children had the most dramatic reactions, especially those between the ages of 5 and 8. One 7-year-old girl regained almost full hearing just four months after treatment and was able to have daily conversations with her mother. At the same time, this treatment also produced meaningful improvements in adult patients.
“Small studies in China have previously shown positive results in children, but this is the first time this method has been tested in teenagers and adults,” Dr. Duan said. “Many of our participants experienced significant improvements in their hearing, which can have a significant impact on their quality of life. We now plan to follow these patients to see how long the effects last.”
Treatment found to be safe
This treatment was shown to be safe and well tolerated. The most commonly reported side effect was a decrease in neutrophils, a type of white blood cell. No serious side effects were observed during the 6-12 month follow-up period.
Expanding gene therapy for hearing loss
“OTOF is just the beginning,” says Dr. Duan. “We and other researchers are expanding our work to other common genes that cause hearing loss, such as GJB2 and TMC1. These are more complex to treat, but animal studies have shown promising results so far. We are confident that patients with many types of inherited hearing loss will one day have access to treatment.”
Multiple institutions participated in the study, including China’s Southeast University Zhongda Hospital. The funding came from several research programs in China as well as Otovia Therapeutics, which develops the gene therapy and employs many of the researchers involved. A complete list of disclosures and conflicts of interest is available in the published article.
