U.K. toddler first to hear through gene therapy, hailing new era

In the United Kingdom, the first young patient with congenital deafness began to hear thanks to gene therapy. What revolutionary gene therapy made this possible?

Opal Sandy was born with a mutation of the OTOF gene, which causes congenital deafness. Before the girl turned one, she became the first patient to undergo a revolutionary gene therapy method. Now 18 months old, Opal can hear sounds as quiet as a whisper and is beginning to speak, uttering the words "mama" and "dada".

The girl is participating in a clinical trial, with participants being recruited in the United Kingdom, Spain, and in the United States. Opal Sandy was cared for by a team of scientists at Addenbrooke's Hospital at the University of Cambridge in England.

The OTOF gene mutation present in Opal causes the production of non-functioning ciliated cells, which receive sound from the environment in a part of the inner ear called the cochlea. Gene therapy involves introducing a working copy of the OTOF gene into the damaged cells using a modified virus. This was done for Opal through an infusion into the right ear under full anesthesia. Regeneron developed the drug.

Just a few weeks later, Opal could hear loud sounds in her right ear, such as clapping. After six months, doctors at Addenbrooke's Hospital confirmed that the ear had a nearly average level of hearing, also for quiet sounds - even whispers.

In her left ear, the little patient received a cochlear implant. This device "substitutes" for the non-functioning ciliated cells. The implant directly stimulates the hearing nerve by receiving wave vibrations, which convey "sound" to the brain. Opal's five-year-old sister, Nora, has the same type of deafness and is doing well using a cochlear implant.

The girls' parents, Jo and James Sandy from Oxfordshire say they are astonished by the gene therapy results in Opal. However, they stressed that allowing their child to participate in testing this treatment method was not an easy decision. 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."