Revolutionary gene therapy enables the first deaf child to regain hearing

In the United Kingdom, the first young patient with congenital deafness had her hearing restored thanks to gene therapy. But what is the revolutionary gene therapy behind this success?

Opal Sandy was born with a mutation in the OTOF gene, leading to congenital deafness. Before her first birthday, she became the first to undergo a groundbreaking gene therapy method. At 18 months, Opal can now hear sounds as soft as a whisper and starts speaking, saying words like "mama" and "dada."

Opal is participating in a clinical trial with participants from the United Kingdom, Spain, and the United States. She received treatment from a team at Addenbrooke's Hospital, part of the University of Cambridge in England.

The OTOF gene mutation in Opal results in the production of dysfunctional ciliated cells responsible for receiving sounds in the inner ear's cochlea. The therapy introduces a functional copy of the OTOF gene into these cells using a modified virus. Opal underwent this procedure through an infusion into her right ear while under general anesthesia. Regeneron developed the therapy.

Weeks later, Opal began to hear loud sounds, like clapping, with her right ear. Six months later, doctors at Addenbrooke's Hospital observed that her hearing had reached a nearly average level, even for soft sounds such as whispers.

A cochlear implant was introduced in her left ear. This device compensates for the malfunctioning ciliated cells by directly stimulating the hearing nerve, thus conveying 'sound' to the brain. Opal's five-year-old sister, Nora, who shares the same type of deafness, is also responding well to her cochlear implant.

The girls' parents, Jo and James Sandy from Oxfordshire are amazed by the effects of gene therapy on Opal. They shared that the decision to let their daughter undergo this experimental treatment was difficult. Opal's mother told bbc.com, "We were quite nervous to go down a different path to one that we knew had already worked so well for our eldest daughter. But it also sounded like a really unique opportunity."