Early trials show hearing improvements in teens and adults born deaf due to rare OTOF gene mutation
Gene therapy has, for the first time, restored hearing in adolescents and adults born with congenital deafness caused by OTOF gene mutations, in what researchers are calling a major advance beyond cochlear implants. OTOF is short for otoferlin, a protein involved in the conversion of sound into the electrical signals of hearing.
Congenital hearing loss affects around three in every 1,000 newborns. While cochlear implants offer an effective intervention, they cannot fully replicate natural hearing and require invasive surgery. This new approach instead targets the root genetic cause.
How the therapy works
The breakthrough centres on OTOF-related deafness, a rare inherited disorder caused by mutations in the OTOF gene.
This gene is responsible for producing otoferlin, a protein essential for converting sound vibrations into electrical signals that travel to the brain. Individuals with OTOF mutations have structurally intact ears, but their ability to transmit sound is impaired.
In the trial, scientists delivered a working copy of the OTOF gene directly into the inner ear using a modified adeno-associated virus (AAV) vector. Once inside the sensory hair cells, the gene instructs the body to produce otoferlin again, restoring the sound signal chain.
Success in teens and adults
The approach has already shown success in children, but this latest development goes further. In a trial involving 10 participants aged 1 to 24 years, brainstem response tests improved by an average of 62%, and behavioural hearing assessments rose by 78%.
Some participants could detect speech sounds within weeks. Side effects were minimal, mostly involving temporary drops in white blood cell counts.
Dr Yu Sun, a leading otolaryngologist involved in the trial, said the results challenge long-held assumptions that hearing restoration is only possible in infancy. “The auditory system may retain more plasticity into adolescence and adulthood than previously believed,” he said.
Global momentum and ethical questions
Trials in China and the United States have also shown success in young children with OTOF mutations, restoring 60–70% of normal hearing in some cases. A separate gene therapy developed by a pharmaceutical firm helped 10 of 11 children aged 10 months to 16 years achieve near-normal hearing.
Yet as results accumulate, so do ethical questions. Some in the deaf community argue that interventions risk undermining Deaf culture and identity. These discussions are ongoing and will likely grow as the therapies move toward broader clinical use.
Future gene editing
In parallel, researchers are exploring gene editing techniques such as CRISPR-Cas9. Animal studies have shown success in correcting hearing loss caused by other mutations, though safety concerns around off-target effects must be resolved before human trials.
“Gene therapy is showing promise as a viable cure for hearing loss, with the potential to restore hearing to near-normal levels,” said Eva Opitz, a Clinical Audiologist at Hearology®. “As the field progresses, continued trials, early diagnosis and careful ethical engagement will be essential. For now, though, we should applaud the researchers’ pioneering work.”
