Evaluation of Gene Replacement Therapy in In Vivo and Patient-Derived In Vitro Models of Vanishing White Matter Disease

About This Grant

Project Summary/Abstract Leukodystrophy with vanishing white matter (VWM) is a severe, progressive neurodegenerative disease that most commonly afflicts infants and children. There are no disease modifying treatments. VWM is caused by autosomal recessive mutations in the five subunit genes of the Eukaryotic Initiation Factor 2B (eIF2B) complex, with most mutations occurring in EIF2B5. eIF2B is required for the first steps of protein translation, but also regulates the integrated stress response (ISR). The ISR can be triggered by minor stressors such as viral infection or trauma that decrease eIF2B activity; but in the context of VWM, results in acute and devastating neurological deterioration. Recent work, including ours, has shown abnormal, persistent activation of the ISR in VWM. This is caused by increased expression of stress response genes, such as ATF4, selectively in astrocytes. Concurrent work has shown that VWM astrocytes inhibit oligodendrocyte precursor cells (OPCs) from maturing, leading to decreased production of myelin, the core “vanishing white matter” pathology. Our preliminary data suggests that these two principal features of VWM pathogenesis, deregulated ISR and astrocyte-mediated oligodendrocyte impairment, are associated. However, studies of a therapeutic compound ISR inhibitor (ISRIB) in an EIF2B5-mutant mouse model failed to normalize disease pathologies and showed only partial efficacy. Our goal is to combine scientific insights from an interdisciplinary team of three VWM investigators to develop a targeted and highly translatable therapy for VWM. Due to VWM’s loss of function and monogenic nature, we are investigating adeno-associated virus (AAV) EIF2B5 gene replacement therapy. Advances in AAV vectors have led to safer and more efficient viral vehicles to deliver transgenes, and AAV serotype 9 has become the most widely used for neurological indications. In 2019, AAV9 gene therapy for spinal muscular atrophy achieved FDA approval based on preclinical and clinical work conducted at Nationwide Children’s Hospital, demonstrating the resources and expertise at our disposal to successfully translate a therapy from proof-of-concept to regulatory approval. Our project is to develop and test AAV-mediated transgene rescue of EIF2B5, with the ultimate goal to prevent or mitigate VWM disease. In Aim 1 (R61 phase) we will determine a lead AAV construct by comparing cell-specific and ubiquitous promoters, including a novel astrocyte-specific promoter. We will then ensure translatability of our therapeutic by validating expression and attenuation of disease markers in VWM human patient-derived organoids. Upon selection of a lead candidate, in Aim 2 (R33 phase) we will determine a safe and efficacious dose in two VWM mouse models using clinically relevant outcome measures, including magnetic resonance imaging and electroencephalography. In summary, we detail a rigorous approach to develop and optimize a lead candidate, targeting the underlying astrocytic VWM pathogenesis, and validate it in three models to enhance translation.