A gene therapy trial in China successfully restored hearing in all 10 patients with OTOF gene mutations using a single injection of AAV virus carrying a working OTOF gene into the inner ear. Patients showed dramatic improvement from an average of 106 dB hearing loss to 52 dB, with some beginning to hear within weeks and a 7-year-old girl conversing with her mother after 4 months. The treatment worked across age groups from infants to adults, proving AAV delivery is safe and effective for genetic deafness. This represents the first root-cause treatment for hereditary hearing loss that could scale to other common deafness genes affecting millions globally.