Chimeric enzymes enhance treatment potential for globoid cell leukodystrophy through hematopoietic stem cell gene therapy

: Globoid cell leukodystrophy (GLD) is a fatal lysosomal storage disorder caused by a deficiency in the β-galactosylceramidase (GALC) enzyme, leading to severe demyelination and neurodegeneration, and often death before the age of 2 years. Hematopoietic stem/progenitor cell transplantation (HSPC-T) has limited efficacy due to inadequate GALC delivery to the central (CNS) and peripheral nervous systems (PNS) and associated risks. In vivo gene therapy (GT) using adeno-associated viral vectors shows promise, but safety concerns persist. This research presents a strategy using lentiviral (LV) vector-mediated ex vivo HSPC-GT with a chimeric GALC enzyme that incorporates peptides from α-l-iduronidase (IDUA) and apolipoprotein E II (APO) to enhance expression and blood-brain barrier penetration. The chimeric IDUAsp.GALC.APO enzyme exhibited superior production and secretion compared to native GALC and previous chimeric variants in LV-transduced HSPCs, resulting in improved cross-correction and normalization of GALC activity in GLD neural cells. Proof-of-concept studies demonstrated effective enzyme production, secretion, and cross-correction capability of macrophages from GLD patients. In vivo results showed stable gene marking, sustained enzyme production, and efficient delivery of the chimeric GALC in affected organs, including the CNS and PNS. These findings highlight the potential of HSPC-GT using chimeric GALC enzymes as an innovative therapeutic approach for treating GLD.