AAV-based gene therapy with modified HEXB confers lasting therapeutic benefits in GM2 gangliosidosis models

GM2 gangliosidoses, including Tay-Sachs (TSD) and Sandhoff (SD) diseases, are lysosomal storage disorders with neurological manifestations caused by the excessive accumulation of GM2 ganglioside (GM2) due to the deficiency of the heterodimeric β-hexosaminidase A (HexA), comprised of α and β subunits. Although preclinical studies and clinical trials of gene therapy for TSD and SD are underway, efficacy and safety concerns have prevented their clinical application. Here, we evaluated the therapeutic benefit of a tyrosine-mutant adeno-associated virus vector serotype 9 (AAV9/3) encoding modified HEXB (modHEXB) wherein nine amino acid residues were substituted for the amino acid residues in HEXA. The intracerebroventricular administration of AAV9/3-modHEXB in SD mice resulted in modHexB expression in several brain regions, reduced GM2 accumulation and improved neuroinflammation. Furthermore, AAV9/3-modHEXB highly rescued motor function, and longer lifespan in SD mice compared to a bicistronic expression vector carrying HEXB-P2A-HEXA. We also evaluated the safety and biodistribution of AAV9/3-modHEXB after intrathecal administration in juvenile rats. We observed widespread transgene expression within the brain, spinal cord, and peripheral tissues without signs of toxicity. This study supports the efficacy and safety of intrathecal administration of AAV9/3-modHEXB, suggesting its potential for clinical trials in patients with the infantile, juvenile, and adult types of TSD and SD.