2024-01-28 09:12:37
Will we soon be able to cure deafness among young people? At the moment, no curative treatment exists. Profoundly deaf children can benefit from cochlear implantation allowing them to “artificially” regain their hearing and those who are hard of hearing can benefit from prostheses compensating for the damage or amplifying the sound. But nothing to “heal”.
French researchers from the Pasteur Institute, Necker Hospital, Sensorion biotech, the Hearing Institute and the Fondation Pour l’Audition have just developed a new treatment called SENS-501 . Its objective: to allow children suffering from genetic deafness to fully regain their hearing. The clinical trial, entitled Audiogene, aimed at measuring the effectiveness of this drug has just begun. This is a first in France.
A trial on 12 profoundly deaf infants
Twelve infants aged 6 to 31 months will participate in this test. All suffer from a profound genetic deafness from birth called DFNB9. In affected people, a defective gene prevents the production of otoferlin, a protein needed by sensory hearing cells in the inner ear to convert sound vibrations into chemical signals sent to the brain.
“In the synapse of the affected cell, there is no longer any transfer of information to the auditory neuron,” explains Christine Petit, exceptional professor at the Pasteur Institute, professor at the Collège de France and founding director of the Hearing Institute, which participated in the development of this treatment.
A virus injection into the inner ear
Babies participating in the trial will undergo surgery, under general anesthesia, to inject a harmless virus into the cochlea of their inner ear. “We bring the strand of DNA that is dysfunctional into the target cell,” explains Natalie Loundon, ENT hospital practitioner and head of the audiology research platform unit at the Necker children’s hospital and who is working on this trial. It will somehow be replaced to be able to produce the missing protein, the otoferlin protein.
“When the therapeutic product enters this cell, the DNA from a normal copy of the gene “to be repaired” is released and begins to code for the protein,” adds Christine Petit. This protein, otoferlin, will replace the missing otoferlin and orchestrate synaptic activity again. In a few weeks we go from a frozen, mute synapse to a fully functional synapse. »
Effective tests carried out on mice
Tests were carried out on monkeys to ensure that the drug targets the defective cells and does not express itself in others. Conclusive studies have also been carried out in mice. “All the treated mice regained their hearing in the weeks following the injection,” rejoices Natalie Loundon.
The researchers hope to obtain a positive result within a month of the injection, with further progression within the next six months. It is currently impossible to know whether infants will quickly regain all of their hearing or whether it will reappear gradually. They will therefore be followed for several years in order to observe their long-term evolution. “We are very hopeful that it will last a very long time, more than forty years,” assures the doctor.
Hope for other types of deafness
If this research gives hope, it is not certain that we will soon achieve a total cure for all deaf people. “The type of deafness that we are working on in this clinical trial represents approximately 3% of those deaf at birth,” specifies Christine Petit. So a small part. But a choice made because of the “simplicity” of this type of deafness. “In this otoferlin anomaly, the entire structure of the inner ear is preserved,” emphasizes Natalie Loundon. All that’s missing is this little protein ».
However, researchers don’t stop there. “We are now working on the most common form of congenital deafness, which represents 50% of cases of hereditary profound deafness at birth, and which is due to damage to the GJB2 gene,” explains Christine Petit. This is a much more complex attack because it is no longer a single cell type that is defective but around ten different cell types. »
Chinese and American trials underway
The researcher assures her, the idea, ultimately, is to find a treatment for all children suffering from genetic deafness, or even for people suffering from age-related deafness. “Certain forms of deafness involving several genes will probably require other approaches to treat them,” says the professor. Natalie Loundon must daily temper the rush of patients wishing to participate in a clinical trial. “We’ll find it, that’s for sure, but it won’t happen tomorrow. »
Abroad, researchers have taken a lead. Four trials are underway around the world. Earlier this week, the Philadelphia hospital announced that it had allowed an 11-year-old deaf boy to regain his hearing thanks to a similar type of gene therapy.
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