Is CABP2-Associated Hearing Loss (DFNB93) a Gene Therapy Target? Preclinical Progress and Patient Registry

CABP2 modulates presynaptic CaV1.3 Ca2+ channel function in inner hair cells (IHCs) and is required for indefatigable synaptic sound encoding. Biallelic variants in CABP2 are associated with non-syndromic hearing loss (DFNB93). Otoacoustic emissions have been observed in an Italian family with a homozygous CABP2 variant, indicating preservation of outer hair cell-mediated cochlear amplification. Hence, DFNB93 belongs to the hearing disorders caused by impairment of IHC synapses, termed auditory synaptopathy. DFNB93 mouse models have recapitulated findings and demonstrated that lack of CaBP2 impairs synaptic sound encoding by enhanced steady-state inactivation of CaV1.3 Ca2+ channels. Furthermore, preclinical studies have demonstrated feasibility of gene therapy. As growing evidence from OTOF clinical trials confirms synaptopathies as promising therapeutic targets for hearing restoration, CABP2 ranks highly among the candidate genes for virus-mediated gene therapy to restore hearing. This perspective summarizes the preclinical gene replacement studies for hereditary hearing loss and outlines the characteristics that make genetic targets ideal for therapy development. It reviews the current literature on human CABP2 studies, pre-clinical therapy development, and introduces a patient registry that aims to support research involvement with the CABP2 patient community. We conclude with a preview of the next steps toward CABP2 gene therapy clinical trials.