A new gene therapy helped five deaf children hear for the first time (Credit: a-atlantichearing.com/ CC-BY-SA-2.0)

A novel gene therapy is bringing hope to children born with a specific type of hereditary deafness. On January 25, 2024, researchers at China's Fudan University and Harvard Medical School (HMS) announced that the groundbreaking treatment had restored the hearing of five of the six test patients.

Who participated in the trial?

The study was conducted on six children between the ages of one and seven. Of the six, four had cochlear implants. They allowed them to hear in one ear. When the implants were switched off, all participants were completely deaf. The two youngest participants, ages one and two, had no implants.

What type of deafness did the trials treat?

Dr. Yilai Shu examines a young patient at the Fudan University in Shanghai, China, after the gene therapy procedure (Credit: Dr. Yilai Shu/ CC-BY-SA-2.0)

The trial focused on a mutation in the OTOF gene. The gene produces the otoferlin protein in the snail-shaped part of the inner ear called the cochlea. It is the area of the ear where sounds are translated into electric pulses. The nerve cells carry the pulses to the brain, where they are interpreted as sound. Otoferlin is very important in transmitting the pulses from the cochlear cells to the nerves. Without it, the electric signals never reach the brain.

How did the treatment work?

The children were all injected in the cochlea with two harmless viruses. Each virus contained half of the normal OTOF gene. Once the gene reached the target cells, it began to produce the missing protein. Within four to six weeks after the injection, the researchers began testing for signs of hearing improvement.

What were the results?

At the end of the 26 weeks, five of the six children showed substantial improvement in hearing. The three older children could understand and respond to speech with their implants turned off. Two could even recognize speech in a noisy room and participate in a phone conversation.

The youngest children also showed improvement in their ability to discern speech. HMS Associate Professor Zheng-Yi Chen, who co-led the study, said that the one-year-old began to respond to sounds and formed simple first words like "mama."

The team is unsure why one of the participants showed no improvement in hearing. They suspect the child's body may have rejected the viruses.

What is next?

More trials are needed before the treatment can be offered to everyone. But once ready, it will change the lives of the estimated 200,000 people worldwide affected by Otoferlin-related deafness.

Resources: hms.harvard.edu, CNN.com