Novel AAV843 Vector-Mediated Gene Replacement Therapy Rescues Primary Hyperoxaluria Type I in Mice

Primary hyperoxaluria type 1 (PH1) is a rare autosomal recessive disorder resulting from mutations in the alanine-glyoxylate aminotransferase (AGXT) gene, leading to excessive systemic deposition of calcium oxalate. This condition is an important cause of end-stage renal disease in children and poses a serious threat to patient survival. Current therapeutic approaches are limited primarily to conservative management and organ transplantation, underscoring the need for more effective treatments. Gene replacement therapy represents a promising alternative strategy. In this study, Agxt^-/^- mice lacking exons 3-8 were characterized, confirming the complete loss of hepatic alanine-glyoxylate aminotransferase (AGT) expression and the presence of early-onset hyperoxaluria. Exposure to glyoxylic acid induced pronounced renal calcium oxalate crystal deposition, establishing a robust and previously unreported induction approach in gene-edited PH1 mouse models. Using this platform, human AGXT cDNA was delivered via the liver-tropic, low-immunogenic AAV843 vector, which has been employed in clinical trials for hemophilia. Gene therapy resulted in normalization of urinary oxalate levels, restoration of hepatic AGT expression, and significant attenuation of renal injury and nephrocalcinosis. These therapeutic effects were accompanied by significant suppression of key mediators involved in renal inflammation, necroptosis, and fibrosis. Moreover, transgene expression was highly specific to the liver and was not associated with hepatotoxicity. These results demonstrate that AAV843-mediated AGXT gene replacement is a safe and effective approach that achieves phenotypic correction in a murine model of PH1, warranting further evaluation in preclinical studies.