Scientists in Sweden have successfully delivered a functional version of the OTOF gene, a gene therapy that plays a significant role in transmitting auditory signals from the ear to the brain, successfully reducing deafness from 106 decibels to 52 decibes. The gene therapy was delivered via injection in the membrane at the base of the cochlea using an adeno-associated virus, or AAV, a well-tested and safe method for genetic therapies. The results were seen in a 2025 study analyzing the gene OTF at five hospitals throughout China. This is the first time the method has been tested in teenagers and adults. However, scientists have a long way to go before they can successfully reverse genetic hearing loss across the board.