551. Enhancement of Gene Therapy Treatment for Sandhoff Disease Through Complimentary Drug Therapy

GM2 gangliosidoses is a group of neurodegenerative lysosomal storage disorders caused by deficiency in the β-hexosaminidase A (HexA) enzyme. HexA is a heterodimer composed of 2 subunits; α- (encoded by the HEXA gene) and β-hexosaminidase β (Encoded by the HEXB gene). Mutations in either gene may cause inactivity of HexA leading to either Tay-Sachs disease (TSD, HEXA mutation) or Sandhoff disease (SD, HEXB mutation) respectively. TSD and SD are clinically indistinguishable phenotypes principally affecting infants and young children that are fatal before the age of 4 years; there is currently no effective available treatment. A mouse model for SD has been developed and these mice reach a humane end point at 14-17 weeks of age. Gene therapy can be an important primary therapeutic strategy, but may fall short of a complete rescue. Neuroinflammation and neurodegeneration have been identified as hallmark pathological mechanisms in GM2 gangliosidosis and can be adjunctive therapeutic targets. Neuroanti-inflammatory/neuroprotective agents like non-steroidal anti-inflammatory drugs (NSAIDs), Histone deacetylase inhibitors and pharmacological chaperones have shown ameliorating effects in SD and similar disease models when used alone. Adeno associated virus (AAV) based expression of Hexosaminidase isoenzymes has been shown to increase survival of Sandhoff mice for long term. We tested the combined role of gene therapy and neuroanti-inflammatory/neuroprotective agents in SD mice. Our methods include injecting neonatal SD mice with a relatively low dose (2×1013 vg/kg) of a novel AAV9 vector expressing Hex A using both α and β subunits. A pilot study established the survival of these mice to be approximately 24 weeks, a 55% increase in life span over vehicle-injected controls. We observed a 47% increase in Hex A activity in the midbrain of treated mice as compared to the vehicle injected controls. Cohorts received treatment with neonatal gene therapy alone or in combination with indomethacin (a NSAID), pyrimethamine (a proven pharmacological chaperone for Hex A) and ITF2357 (a histone deactylase inhibitor) to elicit their combinational therapeutic potential. Each drug is administered daily via oral gavage starting the age of 6 weeks. All treatments have been completed and mice are being monitored for survival benefit and locomotor behaviour. Further analyses of enzyme activity, GM2 ganglioside levels and copy numbers will be done. The results of this study will establish a proof-of-concept for a novel combination gene therapy approach for treatment of GM2 gangliosidoses and similar disorders.