Skylark Bio has dosed the first patient in a Phase 1/2 trial of SKY-GJB2, an investigational gene therapy for children with GJB2-related hearing loss.

SONIX trial begins in children with genetic hearing loss

The first patient has been dosed in the SONIX Phase 1/2 clinical trial evaluating SKY-GJB2, a gene therapy being developed by Skylark Bio for GJB2-related hearing loss.

The multicentre, open-label trial will assess the safety, tolerability, pharmacokinetics, pharmacodynamics and preliminary efficacy of a single unilateral intracochlear injection of SKY-GJB2.

The study will enrol children aged nine months to seven years with GJB2-related hearing loss.

GJB2-related hearing loss is the most common genetic cause of nonsyndromic deafness and is caused by changes in the GJB2 gene, which affects production of connexin 26.

Connexin 26 is involved in the gap-junction network of the inner ear, which is important for normal hearing function.

There are currently no approved disease-modifying treatments that address the underlying genetic cause of GJB2-related hearing loss.

Skylark Bio said preliminary data from SONIX are expected by the end of 2026, with additional readouts anticipated in 2027.

SKY-GJB2 targets the underlying genetic cause

Current interventions for childhood hearing loss, including hearing aids and cochlear implants, can provide access to sound but do not correct the genetic cause of GJB2-related deafness.

SKY-GJB2 is designed to deliver a functional copy of GJB2 to supporting cells in the cochlea that naturally express connexin 26.

The investigational therapy is intended to restore the gap-junction network affected by GJB2 mutations and potentially improve hearing function.

Skylark Bio chief executive Jodi Cook said: “Dosing the first patient in SONIX brings us one step closer to a future where children born with genetic hearing loss have new treatment options.”

The company said the trial is designed to generate preliminary clinical data before the end of 2026.

Daniel Lee, scientific adviser to Skylark Bio and an otolaryngology specialist at Massachusetts Eye and Ear, said: “Although current interventions provide meaningful benefits, they do not address the underlying genetic cause.”

Lee added that the trial will evaluate SKY-GJB2 and its potential to support more natural hearing and spoken-language development.

Gene therapy advances in inherited hearing loss

The SONIX trial comes as genetic medicines for inherited hearing loss move into clinical development, with targeted delivery to the inner ear presenting a particular challenge for researchers.

SKY-GJB2 is designed for local administration directly into the cochlea, with the aim of delivering the genetic material to the cells involved in the underlying hearing disorder.

For children with GJB2-related hearing loss, earlier treatment could be particularly important because hearing during early childhood contributes to the development of spoken language.

The SONIX study will provide initial information on whether SKY-GJB2 can be administered safely and whether treatment produces biological or hearing-related effects in children with the condition.

The trial’s preliminary data are expected at the end of 2026, followed by further readouts in 2027.

If clinical development is successful, SKY-GJB2 could represent a potential one-time treatment approach for a genetic form of paediatric hearing loss for which current interventions do not address the underlying disease mechanism.