GM1-gangliosidosis is a rare, fatal, neurodegenerative genetic disease caused by the deficiency of ?- galactosidase enzyme activity and characterized clinically by a wide range of variable neurovisceral, ophthalmological and dysmorphic features. There are currently no effective therapies for GM1-gangliosidosis and only symptomatic treatments are available. In preclinical models, adeno-associated viral (AAV) gene therapy that restores the ?-galactosidase enzyme activity is the most promising therapy for delaying symptom onset, reducing storage in the brain and peripheral tissues, and increasing lifespan. These impressive results have provided the foundation for AAV gene therapy clinical trials. One of the major challenges for developing treatments for GM1-gangliosidosis is the difficulty in the evaluation of treatment efficacy due to the small and heterogeneous patient population as well as slow progression in non-infantile patients. Recently we used liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify a pentasaccharide (referred to as H3N2b) that is elevated > 20-fold in patient urine, plasma, and cerebrospinal fluid (CSF), and in the central nervous system (CNS) of the GM1-gangliosidosis cat. The CNS H3N2b levels in the GM1-gangliosidosis cat are reduced in response to AAV-treatment. H3N2b has potential as a pharmacodynamics/response biomarker for assessment of AAV-treatment efficacy in GM1-gangliosidosis. The goal of this proposal is to validate LC-MS/MS methods for determination of H3N2b in human urine, plasma, CSF, which will be used to assess AAV gene therapy treatment efficacy in a clinical trial.
The aims of this application are 1) validation of LC-MS/MS methods for quantification of H3N2b in human plasma, urine, and CSF; 2) assessment of H3N2b in samples collected from GM1-gangliosidosis natural history study; and 3) application of H3N2b for assessment of treatment efficacy of AAV gene therapy. The proposed work will provide a much-needed tool for assessing therapeutic efficacy.
Although gene therapy has shown great promise in a cat model of GM1-gangliosidosis by delaying symptom onset, reducing lysosomal storage in the brain and peripheral tissues, and prolonging lifespan, evaluation of its treatment efficacy in clinical trials is challenging due to the small and heterogeneous patient population as well as slow progression in the non-infantile patients. Recently, we discovered a pentasaccharide biomarker that was markedly elevated in biofluids from GM1-gangliosidosis patients and in the central nervous system (CNS) of the cat model and was reduced significantly in the CNS of the cat model in response to gene therapy, and thus the biomarker has potential as a pharmacodynamics/response biomarker. In this project, we will validate clinical assays for the biomarker in human urine, plasma, and CSF, and use these assays for assessing the efficacy of gene therapy in a clinical trial.