AAV.103

AAV.103 is an investigational gene therapy designed to restore hearing in individuals with mutations in the gap junction beta-2 (GJB2) gene, which encodes connexin 26—a protein essential for normal auditory function and the most common cause of congenital hearing loss. The therapy uses an adeno-associated virus (AAV) vector to deliver a functional copy of GJB2 selectively to non-sensory supporting cells in the inner ear that normally express this gene. By restoring GJB2 expression and thus connexin 26 function, AAV.103 aims to re-establish proper ion recycling and electrical signaling necessary for hearing[1][4][5][8]. The program was initially developed by Decibel Therapeutics and is now being advanced by Regeneron Pharmaceuticals following their acquisition of Decibel[3][4][5]. As of June 2025, AAV.103 remains in preclinical development with IND-enabling activities ongoing for GJB2-related congenital hearing loss[1][4][5][10].