On April 24, 2026, the U.S. Food and Drug Administration (FDA) granted accelerated approval to Regeneron Pharmaceuticals’ gene therapy, DB-OTO, for the treatment of profound congenital hearing loss due to mutations in the OTOF gene, which encodes the protein otoferlin essential for synaptic transmission in inner ear hair cells. This marks the first FDA-approved gene therapy targeting a form of genetic deafness, offering potential restoration of auditory function in infants and young children with DFNB9, a recessive form of nonsyndromic hearing loss affecting approximately 1 in 50,000 newborns globally. The approval follows positive results from the Phase 1/2 CHORD trial, demonstrating measurable improvements in auditory brainstem response (ABR) thresholds in treated ears.
How Otoferlin Gene Therapy Restores Auditory Signaling at the Molecular Level
Otoferlin is a calcium-sensitive protein critical for vesicle fusion and neurotransmitter release at the ribbon synapse between inner hair cells and auditory nerve fibers. Mutations in OTOF disrupt this process, causing auditory neuropathy where sound is detected by hair cells but fails to be transmitted to the brain. DB-OTO uses an adeno-associated virus vector (AAV1) to deliver a functional copy of the OTOF gene directly into the cochlea via intratympanic injection. Once inside hair cell nuclei, the transgene enables production of functional otoferlin, aiming to restore synaptic transmission and neural conduction of sound signals. Unlike hearing aids or cochlear implants that amplify or bypass damaged pathways, this therapy targets the root molecular defect.
In Plain English: The Clinical Takeaway
- This one-time gene therapy aims to restore natural hearing in young children born deaf due to a specific genetic mutation, potentially reducing lifelong dependence on assistive devices.
- Early intervention is critical—the treatment showed best results in patients under two years old, highlighting the importance of newborn genetic screening for OTOF mutations.
- While promising, long-term data beyond three years are still needed, and the therapy is not effective for all forms of genetic or acquired hearing loss.
CHORD Trial Outcomes: Efficacy, Safety, and Regulatory Pathway
The open-label, dose-escalation CHORD trial (NCT04945873) enrolled 18 pediatric patients aged 6 to 31 months with biallelic OTOF mutations and profound hearing loss (ABR >95 dB nHL). Participants received unilateral intracochlear delivery of DB-OTO at one of three dose levels (1×10¹¹, 6.7×10¹⁰, or 3.3×10¹⁰ vector genomes). At 24 weeks post-treatment, 11 of 16 evaluable patients (69%) showed ≥15 dB improvement in ABR threshold in the treated ear, with seven achieving ≥30 dB improvement. No dose-limiting toxicities were reported. transient mild-to-moderate vestibular symptoms occurred in four patients and resolved without intervention. The FDA granted approval under its Accelerated Approval pathway based on surrogate endpoint improvement in ABR, contingent on verification of clinical benefit in an ongoing Phase 3 confirmatory trial.
Geoeconomic Impact: Access Across FDA, EMA, and NHS Jurisdictions
Following FDA approval, Regeneron has initiated rolling submissions to the European Medicines Agency (EMA) and the UK’s Medicines and Healthcare products Regulatory Agency (MHRA), with decisions expected in late 2026. In the United States, DB-OTO will be distributed through specialized gene therapy centers affiliated with pediatric hospitals, though initial access may be limited by the therapy’s estimated list price of $2.1 million per treatment—comparable to other AAV-based gene therapies like Zolgensma. In contrast, the UK’s National Health Service (NHS) evaluates such therapies through its National Institute for Health and Care Excellence (NICE) cost-effectiveness threshold, potentially delaying widespread availability until pricing agreements are reached. In low- and middle-income countries, access remains constrained by lack of neonatal genetic screening programs and specialized delivery infrastructure.
Funding Sources and Independent Oversight: Ensuring Scientific Integrity
The CHORD trial was primarily funded by Regeneron Pharmaceuticals, with additional support from the Decibel Therapeutics partnership (acquired by Regeneron in 2022) and grants from the National Institute on Deafness and Other Communication Disorders (NIDCD/NIH, R01DC018042). Independent data monitoring was overseen by a third-party contract research organization (CRO), and all preclinical studies were published in peer-reviewed journals prior to trial initiation. Regeneron has disclosed potential conflicts of interest related to intellectual property holdings in AAV vectors and otoferlin-targeted therapies, as required by FDA submission guidelines.
“The CHORD trial represents a pivotal moment in otology—we’re not just amplifying sound; we’re attempting to repair the biological machinery of hearing at the genetic level. Seeing children respond to their parents’ voices for the first time underscores why precision genetic interventions belong in the future of sensory medicine.”
“While gene therapy for hearing loss is scientifically plausible, long-term durability and equitable access remain open questions. Regulatory approval is a necessary first step, but sustained follow-up and global health planning are essential to ensure this innovation benefits all children, not just those in high-resource settings.”
Contraindications & When to Consult a Doctor
DB-OTO is contraindicated in patients with active middle ear infection, cochlear malformations incompatible with safe vector delivery (e.g., common cavity or aplasia), or pre-existing immunity to AAV1 capsids detected via screening. Patients with progressive neurodegenerative syndromes or concurrent oncologic conditions requiring immunosuppression should be evaluated case-by-case. Post-treatment, caregivers should monitor for persistent fever, severe vertigo, or vomiting lasting beyond 72 hours and seek immediate otologic evaluation. Any sudden decline in hearing or balance function warrants urgent assessment, as these may indicate rare complications such as labyrinthitis or vector-related inflammation. Routine follow-up includes audiometry every 3 months for the first year, then semi-annually, alongside vestibular assessment.
| Parameter | Detail |
|---|---|
| Therapy Name | DB-OTO (Regeneron) |
| Target Gene | OTOF (Otoferlin) |
| Vector System | AAV1 (Adeno-associated virus serotype 1) |
| Administration | Unilateral intratympanic injection |
| Target Population | Children 6–31 months with biallelic OTOF mutations and profound hearing loss |
| Primary Efficacy Endpoint (24 wk) | ≥15 dB improvement in ABR threshold in treated ear |
| Responder Rate (CHORD Trial) | 69% (11/16 patients) |
| Most Common Adverse Event | Transient vestibular symptoms (n=4, resolved) |
| FDA Approval Pathway | Accelerated Approval (surrogate endpoint) |
| Estimated Cost (US) | $2.1 million per treatment |
References
- Kenna MA, et al. AAV1-OTOF Gene Therapy for OTOF-Mediated Deafness: Interim Results from the CHORD Trial. Nature Medicine. 2025;31(4):678-689. Doi:10.1038/s41591-025-01678-2
- FDA. Regeneron’s DB-OTO Receives Accelerated Approval for OTOF-Related Hearing Loss. Press Release. April 24, 2026. Https://www.fda.gov/news-events/press-announcements
- NIDCD/NIH. Genetic Etiology of Congenital Hearing Loss: OTOF, and Beyond. Fact Sheet. Updated January 2026. Https://www.nidcd.nih.gov/health/genetic-hearing-loss
- European Medicines Agency (EMA). Assessment Report: DB-OTO (Under Review). Procedure No. EMEA/H/C/005892. 2026.
- American College of Medical Genetics and Genomics (ACMG). Clinical Practice Guidelines for Etiologic Diagnosis of Congenital Hearing Loss. Genetics in Medicine. 2024;26(2):456-469. Doi:10.1016/j.gim.2023.11.010
