Early Translational III
This application is aimed at the development of a novel stem cell-based therapeutic approach for the inherited neurodegenerative disease Friedreich’s ataxia (FRDA). FRDA is caused by a genetic mutation within a gene called frataxin (FXN). Frataxin protein is involved in energy production in the mitochondria of human cells. This mutation, a GAA•TTC triplet-repeat expansion, causes gene silencing, resulting in an insufficiency of frataxin protein in affected individuals. Current therapeutic approaches for FRDA are aimed at restoring mitochondrial function, frataxin replacement or gene activation, and will at best slow or stop the progression of the disease without correcting existing neurological symptoms. Using recently developed gene manipulation methods, we will excise or correct the trinucleotide repeats from the FXN gene in FRDA patient stem cells (induced pluripotent stem cells). We will demonstrate that the corrected genes are active and produce normal levels of frataxin protein. Corrected FRDA stem cells will be differentiated into neurons in the laboratory, and the neurons will be tested for restoration of energy production in cells. Collaborative studies will focus on delivery of corrected neurons into FRDA mouse models to establish efficacy in reversing neurological symptoms.
Statement of Benefit to California:
Our efforts are aimed at development of novel stem cell-based therapeutics for a class of inherited neurological diseases, called triplet-repeat neurodegenerative diseases, which include Huntington’s disease, the spinocerebellar ataxias, forms of muscular dystrophy, Fragile X syndrome and Friederich’s ataxia (FRDA). These diseases, although relatively rare compared to cancer or heart disease, affect thousands of individuals in California. Recent advances now make it possible to generate induced pluripotent stem cells (iPSCs) from affected individuals and differentiate these cells into cell types that are at risk in these diseases (such as neurons, heart, and muscle cells), We will use state-of-the-art genetic manipulation methods to correct the causative mutation in FRDA iPSCs, and show that the corrected gene now functions normally. Neurons will be generated from these genetically corrected cells and used for transplantation into mouse models of FRDA. Restoration of neurological function in these animals will provide a proof of principal that such cells should be used in human clinical trials. Our studies may yield a new therapeutic approach for these currently untreatable disorders, which will be of benefit to patients suffering from these diseases, both in California and worldwide.
This application for a Development Candidate Award is focused on a gene-corrected induced pluripotent stem cell (iPSC) derived therapy for Friedreich’s ataxia (FRDA). FRDA is an inherited neurodegenerative disease caused by a genetic mutation in the frataxin gene. The applicant proposes to transplant gene-corrected iPSC-derived neurons into the cerebellum, the main site of neurodegeneration. There are six Milestones proposed: 1) to develop molecular tools for frataxin gene correction; 2) to screen these tools for activity in FRDA patient cells; 3) to identify optimal methods for iPSC derivation; 4) to confirm that genetic correction of the frataxin gene results in functional gene expression; 5) to differentiate gene-corrected FRDA iPSCs into neuronal cells and test their function in vitro; and 6) to test the function of these neuronal cells in vivo by transplant into a mouse model of FRDA. Objective and Milestones - The proposal is not at an appropriate stage for a Development Candidate Award. It is unlikely that a therapeutic candidate ready for IND-enabling studies will emerge from this project in three years. - The Target Product Profile provides a clear description of the ultimate product, plans to achieve therapeutic efficacy and essential safety issues. The applicant recognizes the importance of establishing an optimal cell dose. Rationale and Significance - The proposed target for cell replacement therapy is the cerebellum, which is only one region of pathology in FRDA. Reviewers noted that cardiomyopathy is often a cause of early death in FRDA patients and suggested that multiple systems may require rescue in this disease. - FRDA is the most common inherited ataxia, affecting roughly 1:40,000 individuals. There are currently no effective therapies, and so this proposal, if successful, could have a significant impact on the disease. Research Project Feasibility and Design - The major deficiency in the research plan is the lack of preliminary data demonstrating the feasibility of frataxin gene correction. Without these data it is impossible to predict whether the project will progress successfully. - There will be considerable preclinical work required in animal models even after gene correction is achieved. The in vivo efficacy of the cell product will be tested in neonatal mice, a stage likely to be more conducive to functional integration of transplanted cells into the host circuitry than later stages appropriate for intervention in human patients. - The preliminary data do not include a description of previous work with an animal model of FRDA. - The research plan is complicated but comprehensive and technically detailed. In vitro assays and quality control methods are established and well described. Meaningful success criteria are included for each milestone. - Additional detail describing the design of the animal studies would have been helpful. For example, how behavioral data will be measured and interpreted, how many animals and what cell doses will be used and alternative approaches should outcomes be suboptimal. Qualification of the PI (Co-PI and Partner PI, if applicable) and Research Team - The research team consists of excellent investigators with complementary and synergistic expertise. - The Principal Investigator (PI) has a strong background in molecular and cellular biology and has been working on FRDA for a number of years. The Co-PI is a leader in the gene manipulation methods proposed in the application. - The Partner PI has expertise in human pluripotent stem cell development to treat neurodegenerative disease. Collaborations, Assets, Resources and Environment - The collaborative nature of the proposed project is a key strength and builds on the synergistic expertise of the team. - The investigators have well-equipped laboratories and the full support of the PI’s institution. Responsiveness to the RFA - The proposal is responsive to the RFA. Human stem cells are necessary to achieve the outcomes of the proposed research, a clear disease target is identified, and no other projects in CIRM’s translational portfolio target this disease.