GALNT3 gene therapy

GALNT3 gene therapy is an experimental adeno-associated virus (AAV)-based gene therapy being developed by Gazi University in collaboration with Charles River Laboratories for the treatment of hyperphosphatemic tumoral calcinosis (HTC). HTC is a rare genetic disorder characterized by hyperphosphatemia and ectopic calcification due to mutations in the GALNT3 gene. The therapy delivers a functional copy of the GALNT3 gene, which encodes the enzyme polypeptide N-acetylgalactosaminyltransferase 3 (ppGalNAcT3). This enzyme is responsible for the O-glycosylation of fibroblast growth factor 23 (FGF23), protecting it from proteolytic cleavage. By restoring ppGalNAcT3 activity, the therapy aims to maintain levels of intact, active FGF23, thereby promoting phosphate excretion and preventing the formation of painful calcium phosphate deposits in soft tissues.