British toddler Opal Sandy, aged three, who was born profoundly deaf in both ears, can now hear normally on her own two years after receiving groundbreaking gene therapy, her parents have revealed.
She is one of 11 out of 12 children who experienced “clinically meaningful hearing improvements, including three who achieved normal hearing” after receiving the gene therapy, according to updated data released on 12 October 2025. Eight with longer follow-up have showed stability or continued improvement in their hearing, the researchers reported.
Opal was 11 months old in September 2023 when she received the gene therapy via an intra-cochlear infusion into her right ear.
Good Morning America television show aired footage on ABC America from BBC News on 17 October 2025 of Opal and her parents Jo and James Sandy revealing the remarkable progress.
Opal was born deaf due to an inherited condition which led to mutations of the otoferlin (OTOF) gene. The infusion under general anaesthesia delivered a working copy of the OTOF gene into her right cochlea, and surgeons also placed a cochlear implant in her left ear.
Now two years after the procedure, her parents said she can hear normally, even when the cochlear implant on her left ear is turned off. Her mother said the transformation was “mind blowing” and her father described the procedure as life changing.
Opal’s sister Nora, six, who has cochlear implants, was also born deaf.
“Both girls had no hearing whatsoever; we’re talking big, massive drums and cymbals being banged behind their heads; there was never a response even at the very highest levels they can test,” Jo said in the video.
Mind-blowing
Three weeks after the surgery, Opal could hear her mother clapping behind her and turned around despite not having her cochlear implant sound processor turned on.
“It was mind-blowing, even at that stage, we were really pleased because a child being able to hear really loud noises is obviously really fundamental from a safety perspective as a parent,” Jo said on the video.
Six months post-surgery Opal could hear whispers, picking up softer sounds and speech. Doctors described the level of hearing in her right ear as “near normal.”
The video shows footage that today she can hear unaided without her cochlear implant sound processor turned on.
New era in hearing loss treatment
Opal is one of 11 patients who received the treatment to experience clinically meaningful hearing improvements, according to Regeneron Pharmaceuticals.
Regeneron, the biotechnology company that developed the DB-OTO gene therapy, reported its latest data at the American Academy of Otolaryngology-Head and Neck Surgery 2025 annual meeting in Indiana from 11 to 14 October 2025.
It published the results in The New England Journal of Medicine on 12 October 2025 and released a media release. Regeneron said the results showcased “dramatic and sustained improvements in hearing and speech perception” in children with profound genetic hearing loss.
The updated data revealed 11 of 12 patients (14 of 15 ears) experienced “clinically meaningful hearing improvements, including three who achieved normal hearing” and eight with longer follow-up showed stability or continued improvement in their hearing.
Among three who completed speech assessments, all showed significant improvement with one able to identify one- and two-syllable words with no visual cues and respond to distant sounds and speech in noisy environments, the doctors reported.
“Until now, genetic OTOF-related hearing loss was considered permanent, which is why many of us have dedicated our careers to this field,” said trial investigator, Dr Lawrence Lustig, chair of the Department of Otolaryngology-Head and Neck Surgery at Columbia University College of Physicians and Surgeons.
“This registrational data set showcases consistent, rapid and robust responses to DB-OTO, and for those followed to later timepoints, we’ve seen hearing stability as well as continued improvement in understanding of speech.
“These results are even more poignant when viewed by the families – as one of the parents said, their situation is now ‘unimaginable’ from one year ago. This truly represents a new era in the treatment of hearing loss.”
Three can hear whispers
The CHORD trial evaluated paediatric participants with profound hearing loss due to variants of the OTOF gene. Among 12 participants aged 10 months to 16 years, nine received the gene therapy unilaterally and three received it bilaterally.
Nearly all demonstrated improved hearing, responding within weeks of treatment, the paper reported. Nine experienced hearing improvements at a threshold of ≤70 decibel hearing level (dBHL) as assessed by behavioural pure tone audiometry (PTA) at week 24.
This threshold corresponds to a clinical standard that typically does not require cochlear implantation and enables natural acoustic hearing, the researchers said.
Six could hear soft speech without assistive devices, and three were further able to detect whispers, achieving normal hearing sensitivity. One participant who did not meet the primary PTA endpoint at week 24 further improved to achieve “nearly normal” hearing sensitivity at week 48. Nine participants also demonstrated an auditory brainstem response (ABR) at ≤90 decibels (dB).
Improvements continued
Hearing improvements remained stable or continued to improve in eight participants who had follow-up visits of ≥36 weeks (up to 72 weeks), the researchers reported.
Speech development was also assessed in the three participants who were followed at least 48 weeks and all showed significant improvements. One could identify one- and two-syllable words with no visual cues and respond to distant sounds and speech in noisy environments.
In all 12 participants, the surgical procedure and DB-OTO were well tolerated, and there were no DB-OTO-related adverse findings reported.
While 67 adverse events occurred or worsened during or after treatment, none led to discontinued participation in the study. Two participants experienced serious adverse events; one was attributed to a cochlear implant surgical complication and the other, a recent vaccination.
Some participants experienced transient post-surgical vestibular adverse events such as nystagmus, nausea, dizziness and vomiting all of which fully resolved.
Regeneron said a US. regulatory application for DB-OTO is planned for his year, pending discussions with the Food and Drug Administration (FDA).
Watch the video of Opal and her parents.
More reading
Gene therapy restores hearing in baby and children with genetic deafness
Addressing the root cause of genetic deafness
Regeneron gene therapy improves hearing in ten deaf children in CHORD trial, ARO conference hears
