The study comprised ten patients between the ages of 1 and 24 at five hospitals in China, all of whom had a genetic form of deafness or severe hearing impairment caused by mutations in a gene called OTOF. These mutations cause a deficiency of the protein otoferlin, which plays a critical part in transmitting auditory signals from the ear to the brain.

Source1: wa%news.ki.se/gene-therapy-restored-hearing-in-deaf-patients [2025-07-02; web-archive]
Source2: https://news.ycombinator.com/item?id=47641713