Inclusion Criteria:
* Male or female aged 9 months to 7 years at the time of gene therapy administration
* Subjects must have at least two (biallelic) pathogenic or likely pathogenic variants in the GJB2 gene
* Bilateral sensorineural hearing loss as assessed by ABR. Hearing loss at ≥85 dB HL for at least one of the frequencies (500-4000 Hz) in the study treatment ear.
* Subject's parent(s)/guardian(s) provide informed consent before the initiation of study-related procedures.
* Subject is able and willing to comply (or provide assent if old enough) will all study requirements.
Exclusion Criteria:
* Subject has non-GJB2 mediated hearing loss including genetic, syndromic, or non-syndromic hearing loss that is not associated with GJB2 mutations.
* Subject has autosomal dominant nonsyndromic hearing loss due to GJB2 mutation.
* No response on ABR testing.
* Bilateral Cochlear Implants.
View Inclusion and Exclusion Criteria at ClinicalTrials.gov