Early signs of hearing improvement have been observed in an Australian toddler who received gene therapy for congenital deafness, the biotechnology company developing the treatment has confirmed.
And a surgeon involved in trialling the therapy also confirmed “encouraging onset of early auditory responses” in all five patients treated plus a good safety profile for the treatment and procedure.
The company, Sensorion, said the children were treated with its SENS-501 (OTOF-GT) therapy via intracochlear injection.
“Three-month results from a SENS-501 treated toddler in the first cohort demonstrate early promising hearing improvement,” it said in a press release in July 2025.
“In cohort one, early signs of hearing improvement were observed in patient three, aged 11 months at the time of injection.”
A spokesman for the French company told HPA the infant known as patient three is Australian. Another Australian toddler and three other children overseas also received low doses of the therapy in late 2024.
“The clinical response observed (in patient three) was evaluated using standard hearing tests carried out by the investigators (Auditory Brainstem Response [ABR], Pure Tone Audiometry, and Patient [Parents] Reported Outcomes),” Sensorion said.
Three-month data from the patient include: positive ABR responses at two frequencies, with the best frequency reaching 70 dB; improvement of hearing levels across two speech frequencies with best frequency reaching 90 dB level, per PTA; and meaningful changes in response to sounds and voices as reported by the parents with an IT-MAIS score increase of 16 points (145% relative improvement from baseline).
The patient also met expected auditory milestones based on an age-based parent questionnaire and according to the patient’s age.
ENT surgeon, Clinical Professor Catherine Birman OAM, from the Children’s Hospital at Westmead, Sydney delivered the therapy.
“I’m thrilled to report the preliminary cohort one data of SENS-501 in the infants and toddlers treated with this highly innovative therapy,” she said.
“Treatment with SENS-501 had a good safety profile and the onset of early auditory responses observed in patient three and the rest of the cohort is very encouraging, especially given the very low dose of vector injected, which is primarily intended at assessing the safety of the therapeutic and of the intracochlear surgical procedure.
“I look forward to patient three’s next visit and continuing the Audiogene study with the second cohort to assess a higher dose of SENS-501.”
Prof Birman said treating children under 31 months of age and naive of cochlear implants was a much-needed undertaking, as restoring hearing in the first three years of childhood had the potential to result in de-novo language acquisition.
Sensorion said Audiogene, its Phase 1/2 gene therapy clinical trial, evaluated a low dose of SENS-501, its first gene therapy candidate for a form of congenital deafness linked to mutations in the OTOF (otoferlin) gene.
The OTOF gene plays a key role in transmission of auditory signals between hair cells of the inner ear and the auditory nerve. When defective, individuals are born with severe to profound hearing loss.
The treatment aims to restore hearing by introducing a functional copy of the gene directly into hair cells via viral vector technology to restore the normal process of converting sound into electrical signals.
“SENS-501, including surgical delivery of the gene therapy, shows a good safety profile in all patients treated so far,” Sensorion said.
“Intracochlear administration was uneventful, and no serious adverse events or serious side effects were reported.”
Treatment and surgical procedure were well tolerated by all participants (aged six months to 31 months) and naive of cochlear implants at the time of the injection. A second cohort of three patients who will be given a higher dose is ongoing and recruitment is close to being completed, Sensorion said.
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