New gene therapy allows children to hear - 18th March 2024

A new gene therapy treatment developed by researchers from Harvard University in the US and Fudan University in China has allowed six deaf children to hear for the first time. The children, aged from one to seven, all had a mutation in the OTOF gene. This instructs cells to manufacture proteins key to transmitting soundwaves to the brain.

Gene therapy commonly employs viruses, called viral vectors, to transport healthy DNA to target cells. However, the OTOF gene presented researchers with a particular challenge. Its size was such that one virus wasn't large enough to carry it.

Researchers overcame this difficulty by splitting the DNA in half and sharing it between two viral vectors, which were then injected into the inner ear. Once the DNA had been inserted into the target cells, it stimulated production of the vital proteins.

Following the 26 week trial, hearing in five out of six children showed significant improvement, being able to understand and respond to speech. Although one subject showed no change, this may be due to their immune system destroying a viral vector. By contrast, a one year old had begun to articulate simple words such as 'mama'.

With hearing loss affecting 1.6 billion people worldwide, there's increasing interest in improving treatments. However, most cases are due to the detrimental impact of environmental noise rather than genetic mutations.

With approximately 200,000 cases, the condition researched in this study affects relatively few people, meaning it's uncertain whether pharmaceutical companies will view this treatment as viable for commercial development.

Nevertheless, co-authors Zheng-Yi Chen and Yilai Shu remain optimistic that US regulatory approval will come in the next three to five years. For Shu, the parents' joy makes their work worthwhile, as he explained, "They were very, very excited, and all of them cried when they first found that their child can hear."