Currently, there are no treatments to reverse or prevent genetic hearing loss, which affects 1 in 500 newborns. Several gene replacement and overexpression preclinical studies targeting genetic hearing loss have shown success, as the inner ear can be accessed safely by local injection. However, all these gene therapy studies have been performed in neonatal animals, except one in the Otof gene; therefore, the suitability of the approach in the fully mature adult inner ear remains to be elucidated.