Genetic deafness is a sensory handicap that affects hundreds of thousands of people around the world, often from birth. Until now, therapeutic solutions have remained limited to hearing aids or cochlear implants, which certainly improve sound perception, but do not repair the underlying cause. Today, a major scientific advance opens up a new era: gene therapy not only makes it possible to deal with children, but also adolescents and adults with a specific form of genetic deafness, really in restaurants their ability to hear.
A key gene, a disabling mutation
At the center of this innovation is the OTOF gene, responsible for the production of an essential protein for the transmission of sound signals from the inner ear to the brain. This gene plays a fundamental role in auditory neuronal communication. When transferred, the transmission of hearing information is interrupted, which makes the person deaf despite the intact presence of cochlear structures. This form of deafness is rare but devastating, because it prevents the perception of sounds from birth or very early in life.
This handicap is often diagnosed in young children, which so far limits interventions to external solutions, without the possibility of curing the genetic cause. The novelty is that gene therapy now makes it possible to act directly on responsible genetic defect, which could radically change the prognosis.
An innovative method based on a modified virus
To repair this faulty gene, researchers use a particularly suitable viral vector: the adeno-associated virus (AAV). This virus is modified to transport a healthy copy of the Otof gene without causing illness. Injected directly into the inner ear, more precisely through a membrane at the base of the cochlea, it allows hearing cells to produce the functional protein necessary for the transmission of sound.
This unique injection is a technical feat, because the cochlea is a delicate and difficult to access structure, especially in humans. In addition, this procedure had never been tested in adolescents or adults, which was an additional challenge linked to neuronal plasticity and the possible degeneration of hearing cells with age.
Encouraging results in patients aged 1 to 24
The clinical study, conducted in five hospitals in China, brought together ten patients with severe or congenital deafness linked to OTOF mutation. The ages of the participants varied from 1 to 24 years, thus making it possible to assess the scope of the treatment on different age groups.
The results were quickly visible: from a month after therapy, most patients began to perceive sounds, which testifies to a fast functional restoration. Over the following six months, this improvement has strengthened, with a clear drop in the average hearing threshold, going from 106 decibels (very high level, difficult to support) to 52 decibels, a volume closer to a natural and comfortable sound environment, comparable to the noise of rain.
This success was particularly notable in young children, aged 5 to 8, who showed a very good response to treatment. However, therapy has also been effective in two older patients, 14 and 24 years old, which shows that the therapeutic window can be wider than what was thought, offering hope to adolescents and adults who have so far been excluded from this type of intervention.
Credit: ISTOCK
Crédits: Evgeniya Markina/Istock
Treatment and safety of treatment
Security is a major concern in any gene therapy, especially when it involves an injection into an area as sensitive as the inner ear. During the one -year follow -up period, no serious side effects were reported in the participants, which is a very encouraging sign for the continuation of clinical development.
This good tolerance strengthens the confidence of researchers and doctors in the potential of this approach. It also opens the way to wider trials, necessary to confirm the sustainability of the results and the generalization of treatment to other populations.
Towards a treatment of other forms of genetic deafness
If the study focuses on Otof’s mutation, the researchers do not stop there. Other forms of genetic deafness, caused by mutations in genes like GJB2 or TMC1, are more frequent but also more complex to treat.
These genes intervene in different cellular hearing mechanisms, which requires more sophisticated and adapted genetic techniques. The results obtained so far on animal models are promising, suggesting the possibility of extending gene therapy to a larger number of patients.
This perspective is all the more exciting since genetic deafness affects millions of people in the world, often without curative solution. The success of OTOF therapy could therefore open the way to a new era where the restoration of hearing becomes possible for various genetic causes, thanks to personalized treatments.
