While promising for functional recovery, AAV has packaging capacity of less than 5 kb (Reisinger, 2020), which limits the utility of single vectors for treating monogenetic disorders of hearing, many of which are larger than 5 kb (Jones and Jones, 2014) including otoferlin. Because the coding sequence for the complete OTOF cDNA exceeds the packaging capacity of an AAV1 vector, DB-OTO (AAV1-Myo15-hOTOFv5) is composed of two AAV1 vectors which encode the 5′ and 3′ components, of human OTOF (Ghosh et al., 2011). The gene discussed is OTOF; the disease is sensory perception of sound.