Within a Month: The Single Injection That Brought Hearing Back to Ten Deaf Patients

Four months after a single injection into her inner ear, a seven-year-old girl was chatting with her mother the way any child does, back and forth, about nothing in particular. She was one of ten patients, from a one-year-old to a 24-year-old, who were born with a genetic form of deafness and who, over the course of one study, began to hear.

The results, published in the journal Nature Medicine and announced by Karolinska Institutet in Sweden, describe something researchers in this field have worked toward for years: hearing restored by repairing its genetic cause.

One faulty gene

For these particular patients, deafness traced back to a single gene called OTOF. The gene carries the instructions for a protein named otoferlin, and otoferlin does a specific job: it helps carry sound signals from the ear to the brain. When mutations leave the body short of it, the machinery of hearing is largely intact, but the message never gets through.

That detail is the reason this approach had a chance of working. The team, drawn from Karolinska and hospitals and universities in China, used a harmless synthetic virus to ferry a working copy of the OTOF gene into the inner ear. The delivery is a single injection, placed through a thin membrane at the base of the cochlea called the round window. One dose, one gene, sent where it was missing.

What the trial found

The change came quickly. Most of the ten patients recovered some hearing within a month. By the six-month follow-up, every one of them had improved considerably. On average, the softest sound they could perceive dropped from 106 decibels, roughly the roar of a jackhammer, to 52, about the level of an ordinary conversation.

The youngest patients did best, especially those between five and eight, though adults benefited too. The treatment held up on safety as well: the most common side effect was a temporary dip in a type of white blood cell, and across six months to a year of follow-up, no serious adverse reactions were reported.

“This is a huge step forward in the genetic treatment of deafness, one that can be life-changing for children and adults,” said Maoli Duan of Karolinska Institutet, one of the study’s corresponding authors. Earlier work in China had shown the method could help young children; this was the first time it was tested in teenagers and adults as well.

This was a small, early trial, and the therapy was developed by a company, Otovia Therapeutics, that employs several of the researchers and helped fund the work. The team is now following the ten patients to see how long the effect lasts.

Just the beginning

OTOF is one of many genes that can cause hearing loss, and it is one of the more straightforward to target, which is part of why it came first. The researchers are already looking past it.

“OTOF is just the beginning,” Duan said. He and others are turning to more common and more complicated genes behind deafness, including two called GJB2 and TMC1. Those are harder problems, and the animal studies so far have been encouraging. For decades, the tools for hearing loss worked from the outside, amplifying sound the ear could not catch. This work starts inside the ear, one gene at a time.