A new gene therapy trial conducted by the Eye & ENT Hospital of Fudan University in China has brought hearing to both children and adults born profoundly deaf due to mutations in the OTOF gene, which prevents the production of otoferlin—a protein essential for transmitting sound signals from the inner ear to the brain. The treatment used a single injection of a synthetic adeno-associated virus (AAV) through a membrane at the base of the cochlea, delivering a healthy OTOF gene directly into inner-ear cells. Within a month, most participants began hearing; by six months, all ten had seen their audible thresholds drop from 106 dB to around 52 dB—a level compatible with everyday speech, according to the full study published in Nature Medicine.
The ten-patient trial took place across five hospitals in China and included two individuals aged 14 and 24, marking the first time gene therapy of this kind restored hearing in older patients. One striking case involved a 7-year-old girl who received the therapy in one ear and relied on a cochlear implant in the other—within four months, she could hold conversations and even heard the sound of rain for the first time.
Why treating older patients is a breakthrough—and what remains uncertain
Historically, gene therapy for hearing loss has focused on very young children, where the inner ear remains most responsive. While previous studies have demonstrated restored hearing in infants, the success in patients over 12 was unexpected. Adults were assumed to have less capacity for recovery—yet the 14- and 24-year-olds in the study showed clear hearing improvement. Lawrence Lustig, a neurotologist at Columbia University who was not involved in the trial, said that hearing gains at age 24 were unprecedented and showed how gene therapy might one day benefit people who missed early intervention.
That said, researchers caution that wider application requires more data. The study reported no serious side effects within the six- to twelve-month window, though one participant had a temporary drop in white blood cell count. The team will monitor participants for up to ten years to better understand safety and long-term effectiveness. The trial was designed specifically for patients with the rare OTOF mutation, which affects an estimated 200,000 people worldwide. Whether this approach will be effective for more common genetic causes of deafness—such as mutations in GJB2 or TMC1—remains to be seen.
A quiet revolution in gene-based hearing restoration
The success of this trial aligns with a broader push into gene-based therapies for hearing restoration. Regeneron recently reported positive results from its own AAV-based OTOF gene therapy trial, where 10 of 11 children treated between 10 months and 16 years old regained hearing, with some reaching near-normal speech detection levels, according to a recent report in Reuters. Meanwhile, companies like Refreshgene and Eli Lilly are pursuing treatments for other types of genetic deafness, potentially expanding access to a wider range of patients.
The appeal of gene therapy is that it goes beyond symptom management. While cochlear implants can help people interpret sound, they don’t restore natural hearing and involve external hardware. Gene therapy addresses the biological cause directly, potentially offering a lifelong solution with a single treatment. In the UK, genetic therapies are being trialled within the NHS, including a 2023 pilot at Cambridge University Hospitals where a toddler with auditory neuropathy received gene therapy. That child began using words like “bye-bye” and “Dada” just months after treatment.
The long road ahead: scaling treatment and ensuring access
Despite these promising developments, the road to mainstream availability will be slow. Gene therapy requires specialised delivery methods, tight quality control in manufacturing, and long-term follow-up to ensure lasting benefit. Regulatory bodies will also need to assess cost, effectiveness, and safety before approving the therapies for wider use.
Still, scientists behind the current trial remain hopeful. Maoli Duan, a co-author from Karolinska Institute who worked closely with the Chinese team, called the results very exciting and believes this delivery method could be adapted to address other common hearing-related mutations. Animal studies on GJB2 and TMC1 gene therapies are already showing promise, and early-stage human trials are being discussed.
For patients and families living with inherited deafness, the idea of reversing hearing loss is more than medical progress—it’s transformative. To be able to hear rain, music, or a loved one’s voice for the first time has a profound impact on quality of life. And while cochlear implants will still have their place, gene therapy is moving closer to offering a natural and lasting alternative.
This may still be early days, but it’s no longer speculative. With trials showing restored hearing even in young adults, gene therapy for deafness is turning from hopeful science into clinical reality.