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| Providing new hope to families facing the debilitating aspects of lysosomal storage diseases. |
RESEARCH SUMMARY Since 2007, the New Hope Research Foundation has coordinated and funded numerous research projects investigating options for treating the central nervous system (CNS) aspects of lysosomal storage diseases. The focus of these studies have been finding treatments for GM2 gangliosidosis, a disease that primarily affects the CNS. It is the hope that the discovery of general methods for treating this disease could be utilized in the future for other diseases that affect the CNS. Pharmacological Chaperone Therapy Early studies funded by the Foundation investigated a small molecule drug, called pyrimethamine, which is known to cross the blood brain barrier (BBB) and enter the brain, This oral drug has been approved by the US Food and Drug Administration for over a half century for the treatment of malaria and toxoplasmosis. It has been recently shown in the laboratory to aid in the stability of the hexosaminidase enzyme, which is needed to break down GM2 ganglioside. Clinical studies, funded by the New Hope Research Foundation, have shown that pyrimethamine serves as a pharmacological chaperone for the hexosaminidase enzyme and that pyrimethamine is thereby able to increase the level of the enzyme in Adult Tay-Sachs disease patients that express an unstable form of this enzyme. More information on the pyrimethamine clinical study results was published by Clarke et al. (2011) and in a case study presented by Keimel and Charnas (2009) and by Keimel (2010). Gene Therapy Gene therapy has the greatest potential for curing GM2 gangliosidosis and other lysosomal storage diseases that affect the CNS. Two major challenges associated with gene therapy relate to the need for adequately distributing the gene vector throughout the CNS and in avoiding an immune response to the protein expressed by the gene vector. The gene therapy research now being conducted by the Foundation is focused on responding to these two challenges. Biodistribution: Early gene therapy clinical studies used a method of directly injecting the vector into the brain tissue, but the vector does not distribute very far from the site of injection and the volume of tissue transduced with this method is extremely limited. This method is only practical in small animal brains. The New Hope Research Foundation has focused its research on gene transfer delivery methods that will result in broad delivery of the gene vector throughout the CNS. The Foundation has identified methods for gene delivery, and is currently conducting investigations to delineate the vector distribution within the body, and in particular, the CNS. A future research project to evaluate these delivery methods in large animals is planned. HexM: Research funded by the Foundation has also resulted in the development of a new enzyme, called HexM, licensed to the Foundation. The advantage of HexM is that the complete gene can be packaged in one small adeno-associated virus (AAV) capsid. Incorporating the complete genetic material into a single small package has been shown to enhance the CNS biodistribution and also increase the efficiency of the vector. Extensive investigations have been completed that confirm the function of the new variant hexosaminidase enzyme, HexM, in effectively degrading the GM2 ganglioside within cell culture (Tropak et al., 2016 and Tropak et al., Supplement, 2016). The initial in vivo gene therapy research using this new enzyme in neonatal mice was presented at the 2015 annual meeting of the American Society for Gene and Cell Therapy (ASGCT) by Karumuthil Melethil et al., 2015, and Osmon et al., 2015. It was also summarized in a poster presented by Keimel et al., 2015, at the annual meeting of the Institute for Engineering in Medicine. This research not only established that the enzyme is effective in degrading GM2 ganglioside in mouse models of Tay-Sachs and Sandhoff disease, but also demonstrated that the treatment allowed significant improvements in both the behavioral testing and longevity of the diseased mice. Details of these studies have been published by Karumuthil Melethil et al., 2016 (and Karumuthil Melethil et al., Supplement, 2016), and by Osmon et al., 2016. The gene vector expressing HexM has also been shown to be effective after treating adult mice with either an intravenous injection (Osmon et al., ASGCT 2016) or by an injection into cerebrospinal fluid (Thompson et al., ASGCT 2016). A key result from these studies is the evidence that the AAV vector is able to cross the mature blood-brain-barrier and transduce cells within the CNS. These studies also showed that the gene transfer resulted in significantly improved behavioral performance and increased longevity when the therapy is injected into adult mice. Immune Tolerance: The human immune system naturally responds with strong defenses to the invasion of "foreign" particles. Critical to this function is the ability to distinguish these foreign invaders from the body's own molecules and cells, referred to as "self". It is anticipated that patients with mutations resulting in no expression of a hexosaminidase gene are expected to have an immune response following the introduction of the enzyme through enzyme replacement therapy (ERT) or to the expression of the enzyme following gene transfer. The Foundation is currently funding the development of assays that allow the measurement of anti-HexM antibodies and HexM specific T- cells, which could proliferate following a gene therapy. The research being funded by the Foundation is currently assessing this immune response in Tay-Sachs and Sandhoff mice in preparation for evaluating methods for inducing immune tolerance towards the HexM enzyme. RESEARCH PLAN AND REQUEST FOR PROPOSALS The New Hope Research Foundation is generally requesting additional proposals (See Grants) that support research efforts that will lead to the creation of a gene therapy for GM2 gangliosidosis. The most recent requests for proposals can be found at the bottom of the following list:
subunit found in lab animals and the human alpha subunit of beta-hexosaminidase A. Prior gene therapy studies in beta-hexosaminidase A deficient animals using only the human gene for the alpha sub-unit need to be interpreted considering the affinity of the monomers from the two species. (Initial grant awarded - 2007)
expression of some lysosomal enzymes. The goal of this project is to determine whether calcium channel blockers might be synergistic with pharmacological chaperone therapy (e.g., pyrimethamine) in the treatment of Adult Tay Sachs Diseases. (Initial grant awarded - 2008)
infantile Tay-Sachs disease so that it might be used as a historical control group for a future gene therapy clinical study. (Initial grant awarded - 2008)
alpha subunit transgene. Broad distribution of a gene therapy vector throughout the human brain will require a highly efficient vector. As the average number of viral particles entering individual cells is reduced with the broad vector distribution, the probability of annealling two individual strands will also be reduced. The self-complementary DNA eliminates the need to form a dual strand after the vector enters the cell. Self complementary AAV vectors have been shown to be more effective when delivered in low concentrations. The vector is also to use a promoter that provides long-term transduction in human neurons and glia cells while keeping the total DNA to a size that permits good AAV production yields. (Multiple grants awarded - 2011 thru 2012)
HexM, in cellulo. (Multiple grants awarded - 2011 thru 2013)
and the HEXM transgene. The effectiveness of the vector is to be assess using minimally invasive injections of the vector in neonatal and adult Tay-Sachs and Sandhoff mice. (Multiple grants awarded - 2013 thru 2014)
specific T-cells and to measure these levels following intravenous delivery of a HEXM vector in mouse models of GM2 gangliosidosis. (Multiple grants awarded - 2015 thru 2016)
response to the introduction of the enzyme through either enzyme replacement therapy (ERT) or to the expression of the enzyme following gene transfer. This project is to propose methods for inducing immune tolerance towards HexM and evaluate the effectiveness of the methods in animal models of GM2 gangliosidosis. (Active proposal request)
significant reductions in GM2 storage material, and therefore, a more clinically relevant biomarker of therapy success should be based on the actual substrate reduction. The goal of this project is to develop a GM2 assay with adequate controls to allow accurate quantitative comparisons over the course of a gene therapy clinical study. (Active proposal request)
it is assumed that an effective therapy must be similarly distributed. A method for delivering AAV vectors is therefore needed that will result in broad distribution of the vector and the expressed enzyme within the CNS. The goal of this project is to develop and evaluate methods in large animal models that could be safely applied to patients with lysosomal storage diseases. (Active proposal request)
known genetic mutations causing Tay-Sachs or Sandhoff disease. (Active proposal request) |
