DB-OTO Gene Therapy for Inherited Deafness

Genetic deficiency of otoferlin, a protein critical to synaptic transmission by the sensory hair cells of the ear, causes congenital deafness. Medicines to treat the condition are lacking; children typically receive cochlear implants. DB-OTO is a dual adeno-associated virus 1 gene therapy that delivers human OTOF complementary DNA (encoding otoferlin) regulated by a hair cell-specific promoter.

We conducted an open-label, single-group, first-in-human registrational study to evaluate DB-OTO. Children with OTOF variants and profound deafness (defined by an average audiometric threshold of >90 decibel hearing level [dB HL], indicating an inability to hear a gas-powered lawn mower) received an intracochlear infusion of DB-OTO (7.2×10¹² vector genomes per ear) in one or both ears. The primary efficacy end point was an average threshold on behavioral pure-tone audiometry (PTA) at week 24 of 70 dB HL or less, a clinical standard that generally avoids cochlear implantation and enables natural acoustic hearing. A key secondary end point was the presence of an auditory brain-stem response to a click stimulus at a threshold at or below 90 dB normalized hearing level (db nHL) at week 24. Safety assessments included adverse events, laboratory results, and vestibular testing.

A total of 12 children have been enrolled in the study. After a single infusion of DB-OTO, a PTA average threshold of 70 dB HL or less at week 24 (primary end point) and an auditory brain-stem response at or below 90 dB nHL (key secondary end point) were found in 9 of the 12 participants (75%; 95% confidence interval, 43 to 95; P = 1.1×10^-13 for both end points). Six participants could hear soft speech without assistive devices, and 3 had average normal hearing sensitivity. A total of 67 adverse events occurred or worsened during or after treatment, none of which led to discontinued participation in the study.

DB-OTO gene therapy improved hearing in patients with OTOF-related deafness, enabling natural acoustic hearing and normalizing hearing sensitivity in 3 of 12 treated patients. (Funded by Regeneron Pharmaceuticals; ClinicalTrials.gov number, NCT05788536.).