Five children born completely deaf experienced partial restoration of hearing following a “groundbreaking” gene therapy. The trial, led by Mass Eye and Ear in Boston and the Eye & ENT Hospital of Fudan University in Shanghai, marked the first global application of gene therapy to children in both ears.
Published in Nature Medicine on June 5, the research revealed that, in addition to regaining their hearing, the children, aged 1 to 11, could identify sound sources and locations, even in noisy settings. A follow-up to a trial from December 2022, where the gene therapy was successfully administered in one ear, this study demonstrated that treating both ears resulted in even more significant benefits.
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All the children involved in the study had a hereditary deafness condition known as DFNB9, resulting from mutations in the OTOF gene. This condition arises when the OTOF gene fails to produce a vital protein called otoferlin, crucial for transmitting sound signals from the ear to the brain. Consequently, the children were unable to hear or speak.
“The children were selected because they would benefit the most from early gene therapy intervention, particularly in language development,” explained Zheng-Yi Chen, DPhil, an associate scientist in the Eaton-Peabody Laboratories at Mass Eye and Ear in Boston, during an interview.
“However, from a safety perspective, treating children is riskier.”
Procedure Overview
During the “minimally invasive” procedure, doctors injected the human OTOF gene into the inner ears of the children. The kids were hospitalized for seven to 10 days for monitoring.
“After four weeks, the children showed improved hearing perception in tests, gradually gaining the ability to speak,” Chen explained.
Within two to three weeks, families noticed a response to sound.
“All five patients experienced restored hearing, improved speech perception, and the ability to identify sound sources in noisy environments,” Chen stated.
The participants encountered only mild adverse effects, such as fever and vomiting.
“This marks the first instance in history of hearing loss being reversed through gene therapy.”
“There were no severe adverse effects,” he noted. “All patients recovered without further intervention.”
The gene therapy is designed to be a one-time treatment, not requiring repetition, although the children will likely need speech therapy. Until now, there has been no single treatment for hearing loss besides cochlear implants, according to researcher Yilai Shu M.D., PhD, director of the Diagnosis and Treatment Center of Genetic Hearing Loss at Fudan Hospital in Shanghai.
“This marks the first time in history that hearing loss has been reversed by gene therapy,” Shu told “And, of course, we believe this will profoundly impact children’s lives.”
Chang Yiyi, a mother in Shanghai, shared her experience regarding her 3-year-old son, Zhu Yangyang, who participated in the trial.
“When Zhu couldn’t speak at 2 years old and didn’t respond to sound, we realized there was a problem,” she said.
Following hearing tests, it was discovered that Yiyi’s son had total deafness.
“It was unbelievable — the best feeling. It was like a miracle.”
“He would get very frustrated because he couldn’t understand, couldn’t speak, couldn’t hear,” she said.
Twenty-three days after receiving the gene therapy, the boy first responded to someone calling out to him.
“It was unbelievable — the best feeling,” Yiyi told. “It was like a miracle.”
“Now he can say ‘Mommy’ and ‘I want’ and some simple sentences.”
Globally, approximately 430 million people have disabling hearing loss, including 34 million children, according to the World Health Organization.
More than 50% of hearing loss cases are genetic.
Dr. Amy Sarow, the lead audiologist at Soundly, a Michigan-based hearing health care marketplace, noted that while gene therapy has shown promise in treating various conditions, there are limitations.
“It is exciting to think about how gene therapy could impact millions of individuals with hearing loss worldwide,” Sarow said. “However, there are many causes of hearing loss, and one type of gene therapy will not be suitable for every type.”
As with any intervention, there can be risks with gene therapy. “One potential risk is that treatment may not be successful in every case,” Sarow said. “Another potential risk is that the targeted gene therapy may not work in the targeted region.”
The next step is to follow the trial patients for a longer period to ensure stable positive results, according to Shu. Based on the initial study, the researchers expect the patients’ hearing abilities to continue improving over time.
“We are working to bring this to people outside China, including the U.S., as quickly as possible,” Shu told.
The researchers also aim to extend this gene therapy to treat other types of deafness in the future.
