How one gene therapy is helping some deaf patients hear for the first time

A single gene therapy injection has shown the ability to restore hearing in patients with a specific genetic mutation, with some beginning to respond to sound within weeks

Hearing loss from birth, previously believed to be irreversible, can now be reversed in only a few weeks, according to new research.

 

Published in Nature Medicine, the study titled AAV gene therapy for autosomal recessive deafness 9: a single-arm trial conducted by scientists at Karolinska Institutet, Sweden, and their counterparts in China, found that all 10 individuals who underwent gene therapy were able to hear better, with some of them responding to sounds within one month.

 

The findings offer early but meaningful hope for treating certain types of genetic deafness.

What is the new gene therapy for genetic deafness and how does it work?

This experimental treatment targets a specific inherited form of hearing loss caused by mutations in the OTOF gene that encodes the otoferlin protein, produced by cells in a part of the inner ear called the cochlea, where sound waves are translated into electrical pulses carried by nerve cells to the brain, where they are interpreted as sound.

 

 

The OTOF mutation is predominantly congenital (present at birth) or prelingual (before speech). People with congenital deafness cannot properly transmit sound signals from the inner ear to the brain, resulting in profound deafness from birth.

 

According to the study, the therapy uses a harmless, engineered virus, called an adeno-associated virus (AAV), to deliver a healthy copy of the OTOF gene directly into the inner ear. Once inside, the gene begins producing otoferlin, effectively restoring the communication pathway for sound.

How does a single injection restore hearing in deaf patients?

The study authors say the procedure involves a one-time injection into the inner ear, specifically through a membrane at the base of the cochlea known as the round window. It carries the corrected gene into key hearing cells, enabling them to produce otoferlin. Once this protein is restored, the ear can once again convert sound vibrations into signals the brain can understand.

 

This is what allows patients, many of whom have never heard before, to begin perceiving sound.

 

According to the study, most patients began responding to sound within one month, and by six months, improvements were clear and stable. The researchers found average hearing thresholds improved from 106 decibels (extremely loud sounds) to 52 decibels (normal conversation level). This means patients went from hearing virtually nothing to detecting everyday sounds, speech, and environmental noise.

Which patients benefited most from the gene therapy trial?

While all 10 patients, aged between 1 and 24 years, showed improvement, children between five and eight years old responded particularly well. One seven-year-old girl regained enough hearing to hold everyday conversations with her mother just four months after treatment, say researchers.

Is the gene therapy safe for hearing loss treatment?

So far, the therapy appears safe and well tolerated. According to the study, the most common side effect was a temporary drop in neutrophils (a type of white blood cell), and no serious adverse effects were linked directly to the therapy. The participating patients were followed for 6 to 12 months.

 

However, the researchers have cautioned that this is still an early-stage trial. Long-term safety and durability of hearing restoration will need to be monitored over several years.

Can this gene therapy treat all types of deafness?

Not yet. The current therapy targets OTOF-related deafness, which is relatively rare. However, many other forms of genetic hearing loss are caused by different genes, such as GJB2 and TMC1, which are more common.

 

Researchers are already working on adapting similar gene therapies for these conditions. Early animal studies have shown promise, though these genes are more complex to treat.

 

The findings offer a shift in the current ways of managing deafness, from devices like hearing aids or cochlear implants to potentially correcting the underlying genetic cause. If larger trials confirm these results, gene therapy could become a one-time, long-lasting treatment for certain types of congenital deafness.