SNUH researchers develop world’s first injective cure for congenital deafness

Lee Sang-yeon, a professor of pediatric otorhinolaryngology at Seoul National University Hospital (SNUH), speaks to a patient at SNUH in Jongno District, central Seoul on Sept. 19. [JUN MIN-KYU]

 
Korean researchers have developed the world’s first gene-editing injection that can correct mutations causing hereditary deafness, offering new hope for children who have relied only on hearing aids or cochlear implants.
 
 
“Mom, if I do this, can I get better too?”
 
Several months ago, nine-year-old Seo-jun (alias), who has lived with congenital hearing loss and relied on hearing aids all his life, asked his mother this question while undergoing a biopsy. At the time, no one could say whether treatment would be possible.
 
Seo-jun’s mother, who was heartbroken at not being able to give a definitive answer to her son’s question, said in an interview with the JoongAng Ilbo on Wednesday, “Now there is hope.”
 
Congenital deafness, like Seo-jun’s, occurs in about one to three out of every 1,000 newborns. More than 200 different genes can cause it, and there has been no breakthrough in treatment beyond prescribing hearing aids or cochlear implants — until now.
 
Lee Sang-yeon, a professor of pediatric otorhinolaryngology at Seoul National University Hospital and researcher in the Molecular Genome Engineering Laboratory led by Bae Sang-su, a professor of biochemistry at Seoul National University, recently reported that they have developed a gene-editing tool that produces meaningful hearing recovery.
 

Lee Sang-yeon, a professor of pediatric otorhinolaryngology at Seoul National University Hospital (SNUH), speaks during an interview with the JoongAng Ilbo at SNUH in Jongno District, central Seoul on Sept. 16. [JUN MIN-KYU]

 
The team targeted the MPZL2 mutation, observed in about 10 percent of hereditary deafness patients and found frequently in East Asians. This mutation often leads to rapid hearing decline during adolescence.
 
The research team analyzed 1,437 families from a hereditary hearing loss cohort to identify the primary causative mutation. They then injected a mouse model with the newly developed gene editing agent. Hearing improved by 20 to 30 decibels, and the effect lasted more than five months.
 
“For decades, the only treatments were hearing aids and cochlear implants,” said Lee. “Now gene therapy offers a new paradigm. The fact that hearing can be restored with a single injection, without surgery, is very encouraging.”
 
“Until now, all we could do was hope his hearing wouldn’t get worse while he wore hearing aids,” Seo-jun’s mother said. “Hearing about this treatment gave me hope for the first time that my child may actually recover.”
 

A diagram showing an overview of gene therapy study developed by a research team at Seoul National University Hospital for hearing loss. A single injection of the proprietary gene-editing tool resulted in improved hearing in a mouse model harboring the MPZL2 mutation, a major cause of hereditary sensorineural hearing loss. [SCREEN CAPTURE]

 
 
Mapping Korean deafness genes
 
The breakthrough was possible because the team built a “Korean genetic map of deafness.” Existing genetic testing could identify the cause in only about half of congenitally deaf patients. By conducting whole-genome sequencing on 752 patients and families, the team identified an additional 20 percent.
 
They also discovered previously unknown mutations, creating opportunities for customized therapies.
 
For instance, siblings Eun-chan (12, alias) and Eun-jin (9, alias), who have Usher syndrome, a condition that causes both hearing and vision loss with age, were found to carry a “deep intron mutation” that previous tests could not detect. That discovery makes it possible to design a targeted treatment.
 
“The MPZL2 therapy can be used for thousands of patients, but for rare intron mutations, ‘N-of-1’ treatments — designed for a single patient — are also necessary,” explained Lee. “Development is essentially complete, but toxicity testing remains the key hurdle.”
 
“I was terrified my kids would truly lose both their hearing and sight,” said Eun-chan and Eun-jin’s mother. “Hearing about this treatment made the future look brighter. It feels like a miracle, [something] beyond words.”
 

Lee Sang-yeon, a professor of pediatric otorhinolaryngology at Seoul National University Hospital (SNUH), speaks during an interview with the JoongAng Ilbo at SNUH in Jongno District, central Seoul on Sept. 16. [JUN MIN-KYU]

 
 
Commercialization still faces challenges
 
Experts caution that there remains much to do before such treatments can become widely available. Safety testing requires significant time and funding, especially in medium-sized animals like monkeys.
 
“It is important to treat hearing loss before it becomes too severe, so speed matters,” said Lee. “In the United States, rare disease therapies can be fast-tracked. I hope Korea’s drug regulators will take a flexible approach.”
 
The project was partly funded by the 300 billion won ($212.2 million) donation from the family of the late Samsung chairman Lee Kun-hee for childhood cancer and rare disease research, as well as support from the National Research Foundation of Korea and Seoul National University College of Medicine.
 
“Because of research funding, we were able to assemble a strong team and make our ideas a reality,” said Lee. “I hope state support continues so this therapy can be safely developed and truly help patients.”
 
 

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom.
BY NAM SOO-HYOUN [[email protected]]