A new study published July 2, 2025, in the journal Nature Medicine (via Gizmodo) has shown that gene therapy effectively restores hearing in adolescents and adults with congenital deafness caused by mutations in the OTOF gene. This gene is responsible for producing the protein otoferrin, which is needed to transmit sound signals to the brain. An estimated 200,000 people worldwide are deaf due to OTOF mutations.
Researchers at the Karolinska Institute in Sweden conducted an experiment involving 10 patients aged 1 to 24 years at five hospitals in China. All of them had deafness or severe hearing impairment due to OTOF mutations. The therapy consisted of a single injection of a functional version of the OTOF gene through the cochlear membrane of the ear using a modified virus.
A month after treatment, most patients began to hear sounds, and six months later, all 10 showed significant improvement in their hearing: the average level of sound perception decreased from 106 dB to 52 dB. No side effects were recorded during the first year. The best results were observed in children aged 5 to 8. In particular, a 7-year-old girl who received therapy in one ear and had a cochlear implant in the other ear regained almost full hearing and was able to carry on everyday conversations. She heard the sound of rain for the first time, the researchers said.
"These are very encouraging results," said Maoli Duan, a co-author of the study from Karolinska Institutet. The improvement in hearing in the 14- and 24-year-old participants was particularly impressive, as gene therapy had previously been thought to be less effective in older patients.
The researchers plan to follow patients for 5 to 10 years to assess long-term effectiveness. They are currently working on therapies for other genes linked to deafness, such as GJB2 and TMC1. Duan says this is just the beginning for treatments for various forms of genetic deafness.