MSC engineered to produce BDNF for the treatment of Huntington's disease
One in every ten thousand people in the USA has Huntington's disease, and it impacts many more. Multiple generations within a family can inherit the disease, resulting in escalating health care costs and draining family resources. This highly devastating and fatal disease touches all races and socioeconomic levels, and there are currently no cures. Screening for the mutant HD gene is available, but the at-risk children of an affected parent often do not wish to be tested since there are currently no early prevention strategies or effective treatments.
We propose a novel therapy to treat HD; implantation of cells engineered to secrete Brain-Derived Neurotrophic factor (BDNF), a factor needed by neurons to remain alive and healthy, but which plummets to very low levels in HD patients due to interference by the mutant Huntingtin (htt) protein that is the hallmark of the disease. Intrastriatal implantation of mesenchymal stem cells (MSC) has significant neurorestorative effects and is safe in animal models. We have discovered that MSC are remarkably effective delivery vehicles, moving robustly through the tissue and infusing therapeutic molecules into each damaged cell that they contact. Thus we are utilizing nature's own paramedic system, but we are arming them with enhanced neurotrophic factor secretion to enhance the health of at-risk neurons. Our novel animal models will allow the therapy to be carefully tested in preparation for a phase I clinical trial of MSC/BDNF infusion into the brain tissue of HD patients, with the goal of restoring the health of neurons that have been damaged by the mutant htt protein.
Delivery of BDNF by MSC into the brains of HD mice is safe and has resulted in a significant reduction in their behavioral deficits, nearly back to normal levels. We are doing further work to ensure that the proposed therapy will be safe and effective, in preparation for the phase I clinical trial. The significance of our studies is very high because there are currently no treatments to diminish the unrelenting decline in the numbers of medium spiny neurons in the striata of patients affected by HD. Our biological delivery system for BDNF could also be modified for other neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS), spinocerebellar ataxia (SCA1), Alzheimer's Disease, and some forms of Parkinson's Disease, where neuroregeneration is needed. Development of novel stem cell therapies is extremely important for the community of HD and neurodegenerative disease researchers, patients, and families. Since HD patients unfortunately have few other options, the potential benefit to risk ratio for the planned trial is very high.
It is estimated that one in 10,000 CA residents have Huntington’s disease (HD). While the financial burden of HD is estimated to be in the billions, the emotional cost to friends, families, and those with or at risk for HD is immeasurable. Health care costs are extremely high for HD patients due to the long progression of the disease, often for two decades. The lost ability of HD patients to remain in the CA workforce, to support their families, and to pay taxes causes additional financial strain on the state’s economy. HD is inherited as an autosomal dominant trait, which means that 50% of the children of an HD patient will inherit the disease and will in turn pass it on to 50% of their children. Individuals diagnosed through genetic testing are at risk of losing insurance coverage in spite of reforms, and can be discriminated against for jobs, school, loans, or other applications. Since there are currently no cures or successful clinical trials to treat HD, many who are at risk are very reluctant to be tested. We are designing trials to treat HD through rescuing neurons in the earlier phases of the disease, before lives are devastated.
Mesenchymal stem cells (MSC) have been shown to have significant effects on restoring synaptic connections between damaged neurons, promoting neurite outgrowth, secreting anti-apoptotic factors in the brain, and regulating inflammation. In addition to many trials that have assessed the safety and efficacy of human MSC delivery to tissues via systemic IV infusion, MSC are also under consideration for treatment of disorders in the CNS, although few MSC clinical trials have started so far with direct delivery to brain or spinal cord tissue. Therefore we are conducting detailed studies in support of clinical trials that will feature MSC implantation into the brain, to deliver the neurotrophic factor BDNF that is lacking in HD. MSC can be transferred from one donor to the next without tissue matching because they shelter themselves from the immune system. We have demonstrated the safe and effective production of engineered molecules from human MSC for at least 18 months, in pre-clinical animal studies, and have shown with our collaborators that delivery of BDNF can have significant effects on reducing disease progression in HD rodent models.
We are developing a therapeutic strategy to treat HD, since the need is so acute. HD patient advocates are admirably among the most vocal in California about their desire for CIRM-funded cures, attending almost every public meeting of the governing board of the California Institute for Regenerative Medicine (CIRM). We are working carefully and intensely toward the planned FDA-approved approved cellular therapy for HD patients, which could have a major impact on those affected in California. In addition, the methods, preclinical testing models, and clinical trial design that we are developing could have far-reaching impact on the treatment of other neurodegenerative disorders.
Huntington’s disease (HD) is a hereditary, fatal neuropsychiatric disease. HD occurs in one in every ten thousand people in the USA. The effects of the disease on patients, families, and care givers are devastating as it reaches from generation to generation. This fatal disease touches all races and socioeconomic levels, and current treatment is strictly palliative. Existing drugs can reduce the involuntary movements and psychiatric symptoms, but do nothing to slow the inexorable progression. There is currently no cure for HD. People at risk of inheriting HD can undergo a genetic counseling and testing to learn if they are destined to develop this dreadful disease. Many people from HD families fear the consequences of stigma and genetic discrimination. Those at-risk often do not choose to be tested since there are currently no early prevention strategies or effective treatments.
We propose a novel therapy to treat HD: implantation of cells engineered to secrete Brain-Derived
Neurotrophic Factor (BDNF), a factor that can promote addition of new neurons to the affected area of the brain. BDNF is reduced in HD patients due to interference by the mutant Huntingtin (htt) protein that is the hallmark of the disease. We have discovered that mesenchymal stem/stromal cells (MSC), a type of adult stem cell, are remarkably effective delivery vehicles, moving robustly through the tissue and infusing therapeutic molecules into damaged cells they contact. In animal models of HD implantation of MSC into the brain has significant neurorestorative effects and is safe. We propose to use these MSCs as “nature's own paramedic system”, arming them with BDNF to enhance the health of at-risk neurons. Our HD animal models will allow the therapy to be carefully tested in preparation for a proposed Phase I clinical trial of MSC/BDNF implantation into the brain of HD patients (HD-CELL), with the goal of slowing disease progression.
Delivery of BDNF by MSC into the brains of HD mice is safe and has resulted in a significant reduction in their behavioral deficits, nearly back to normal levels. We are doing further efficacy and safety studies in preparation for the Phase I clinical trial. The significance of our studies is very high because there are currently no other options, there is no current treatment to delay the onset or slow the progression of the disease.. There are potential applications beyond Huntington’s disease. Our biological delivery system for BDNF sets the precedent for adult stem cell therapy in the brain and could potentially be modified for other neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS), spinocerebellar ataxia (SCA), Alzheimer's disease, and some forms of Parkinson's disease. Since HD patients unfortunately have few other options, the potential benefit to risk ratio for the planned trial is very high.
In the first year of our grant we have successfully engineered human MSCs to produce BDNF, and are studying effects on disease progression in HD mice. We have developed methods to produce these cells in large quantities to be used for future human clinical studies. As we go forward in year 2 we plan to complete the animal studies that will allow us to apply for regulatory approval to go forward with the planned Phase I trial.
We have designed an observational study, PRE-CELL, to track disease progression and generate useful data in preparation for this future planned Phase I clinical trial. PRE-CELL has been approved by the institution’s ethics board and is currently enrolling subjects. PRE-CELL was designed to operate concurrently with the ongoing pre-clinical safety testing. For additional information go to: ClinicalTrials.gov Identifier: NCT01937923
Background: Huntington’s disease (HD) is a genetically inherited, fatal neuropsychiatric disorder which strikes 1/10,000 people. The cause is a repeat expansion in the Huntingtin gene which leads to progressive brain degeneration, ultimately resulting in death after 15-20 years. HD passes from generation to generation. Each child of a parent with HD has a 50% chance of inheriting the HD mutation. There is currently no treatment, therapy or medication that will delay the onset of the disease or slow its progression. All currently available treatments are palliative, which focus on symptom management alone. There is currently no cure for HD.
Proposed therapy: We propose a novel therapy for HD: implantation of mesenchymal stem cells engineered to secrete Brain-Derived Neurotrophic Factor (MSC/BDNF). BDNF levels are reduced in the brains of HD patients. BDNF has been shown in numerous transgenic HD mouse studies to prevent cell death and to stimulate the growth and migration of new neurons in the brain, and is thus a lead candidate for neuroprotection in HD. We are using MSCs as delivery vehicles to produce BDNF in the affected areas of the striatum. We are conducting detailed tests of MSC/BDNF in HD mouse models in preparation for a proposed Phase I clinical trial of MSC/BDNF implantation into the brain of HD patients (HD-CELL), with the goal of slowing disease progression.
Progress, Year 2 of grant: Based on recommendations from the CIRM Clinical Development Advisory Panel (CDAP), we altered our vector and added a second animal model. Following CDAP, we repeated all manufacturing and testing of MSC/BDNF using the new vector, produced using Standard Operating Procedures (SOPs) from our UC Davis Good Manufacturing Practices (GMP) Facility. We have shown that MSC/BDNF produces high levels of BDNF and that a multiplicity of infection of ten virus particles per cell generates a single unrearranged integrant per cell, on average. This is data critical to the Recombinant DNA Advisory Committee (RAC), for whom we have prepared an Appendix M application. RAC approval is needed prior to FDA approval because it is a proposed stem cell gene therapy trial. We are currently refining our application to the FDA and will seek CIRM approval for submission.
We are completing our double-blinded studies, now using the new vector, examining the effects on disease progression of implantation of MSC/BDNF in two strains of HD transgenic mice: YAC 128 and R6/2 (CAG 120). The R6/2 (CAG 120) model has the early onset of neurologic dysfunction and dies much earlier than wild-type of YAC 128 models. For this reason it is a more suitable model of juvenile HD. In the R6/2 model we have successfully demonstrated that implantation of MSC/BDNF causes an improvement in deficits in open field exploration, a behavioral assay. We have also shown that MSC/BDNF causes increased neurogenesis in the brain of treated mice, an important milestone.
The YAC 128 model develops slowly progressive behavior symptoms in mid-life and has loss of brain cells that mirrors changes seen in HD patients. In the YAC 128 model we have shown that implantation of our MSC/BDNF product decreases striatal atrophy between 8 and 12 months of age. Wild type mice have a typical lifespan of two years, so this age in the YAC 128 mouse roughly corresponds to the typical age at onset for early-stage HD patients that we are proposing to treat in our future planned Phase 1 study, HD-CELL.
Clinical Update: In tandem with the on-going preIND studies in the lab, the clinical team is conducting an observational study, PRE-CELL. The goal of PRE-CELL is to establish baseline characteristics and track disease progression in a group of early stage HD patients. PRE-CELL subjects undergo detailed neurological, psychiatric, cognitive, imaging and laboratory testing, including measurement of BDNF levels. PRE-CELL participants who have completed at least 1 year of follow-up and meet inclusion and exclusion criteria will be considered for the future planned cell therapy trial. PRE-CELL has been approved by the Institutional Review Board at UC Davis since July 2013 and is still enrolling. For additional information, please go to: ClinicalTrials.gov Identifier: NCT01937923.
Significance: Our progress to date supports the completion of our final pre-clinical studies and our plan to go forward toward regulatory approval. There are potential applications of our research beyond HD. Our biological delivery system for BDNF sets the precedent for adult stem cell therapy in the brain and could potentially be modified for other neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS), spinocerebellar ataxia (SCA), Alzheimer's disease, and some forms of Parkinson's disease. It also provides a platform for our future gene editing studies, since we will again use MSCs to deliver the needed molecules into the neurons.
Progress, Year 3 of the grant
Pre-clinical update: The pre-clinical team successfully engineered mesenchymal stem cells (MSCs) harvested from healthy qualified donors to overexpress BDNF (MSC/BDNF), using clinically relevant methods. MSC/BDNF were found to be stable with no change in their appearance, proliferation rate or differentiation when compared to non-engineered MSC. The efficacy studies of human MSC/BDNF were completed in two transgenic Huntington’s disease mouse models: the YAC 128 and R6/2. All animals underwent implantation of mini-osmotic pumps under the skin to provide immune suppression drugs to create a more favorable environment for the human cell product in the mouse brain prior to undergoing bilateral injection of MSC/BDNF into the target brain region, the striatum. All studies were conducted in randomized, controlled and blinded fashion. Implanted and control mice underwent weekly behavioral testing. The animals’ brains were sectioned and studied after death. Results demonstrated reduction in striatal atrophy and improvement in a key behavioral test measuring anxiety-like behaviors in YAC 128 mice, with evidence for the growth of new neurons in the area adjacent to the ventricle and a trend toward longer survival in R6/2 mice. For full description, please see the following publication in “Molecular Therapy:” http://www.ncbi.nlm.nih.gov/pubmed/26765769)
These data were submitted to the NIH Recombinant DNA Advisory Committee on June 6, 2015 (see http://videocast.nih.gov/summary.asp?Live=16416&bhcp=1). The committee provided positive feedback about the pre-clinical studies and the design of the future planned Phase 1 safety and tolerability trial. The grant team also submitted a pre-Investigational New Drug (pre-IND) package to the Food and Drug Administration, and a successful teleconference was conducted on July 15, 2015. The FDA provided specific feedback about the development of MSC/BDNF, the results of pre-clinical efficacy studies, the design of the future planned Phase 1 safety and tolerability trial, with recommendations to conduct definitive dose-finding, biosafety, biodistribution, and large animal neurotransplantation targeting studies. The pre-clinical team is completing the additional recommended studies in transgenic HD mouse models and seeks funding to conduct the large animal neurotransplantation studies.
Clinical Update: The clinical team continues to conduct the PRE-CELL study (ClinicalTrials.gov identifier: NCT01937923), an observational study for early-stage Huntington’s disease patients and their care partners. The goal of PRE-CELL is to establish baseline characteristics and track disease progression as measured by changes in clinical features, MRI brain scan structural and morphologic analysis, and measurement of biomarkers in spinal fluid and serum. Subjects who complete at least one year of participation in PRE-CELL will be potential candidates for the future planned Phase 1 safety and tolerability trial, HD-CELL. PRE-CELL is fully enrolled and closed to new subjects in July 2015. Interim analysis demonstrated successful determination of baseline characteristics and the rate of change in neurological, cognitive, functional, behavioral, quality of life, imaging and biomarker measures for each subject and for the cohort overall. PRE-CELL has been extended to July 31, 2016.
The clinical team developed a draft protocol for the future planned Phase 1 safety and tolerability trial (HD-CELL) and revised the protocol based on feedback from the NIH RAC hearing and the FDA pre-IND meeting. We plan to submit an IND application by Quarter 4 of the current year pending successful completion of the additional IND-enabling studies described above.
Significance. There is still a critical unmet need for disease-modifying treatments for HD. Our progress to date supports the completion of the additional pre-clinical studies and our plan to submit an IND application to the FDA for the future planned Phase 1 safety and tolerability trial of MSC/BDNF in HD patients. This work also provides a platform for our future gene editing studies for HD, since we will use MSCs to deliver the needed molecules into the central nervous system.
There are potential applications of this research beyond HD. Our biological delivery system for BDNF sets the precedent for adult stem cell therapy in the brain and could potentially be modified for other neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS), spinocerebellar ataxia (SCA), Alzheimer's disease, and Parkinson's disease. The MSC/BDNF product could be considered for studies of regeneration in traumatic brain injury, spinal cord and peripheral nerve injury.
- Mol Ther (2016) Human Mesenchymal Stem Cells Genetically Engineered to Overexpress Brain-derived Neurotrophic Factor Improve Outcomes in Huntington's disease Mouse Models. (PubMed: 26765769)
- Regen Med (2015) Developing stem cell therapies for juvenile and adult-onset Huntington's disease. (PubMed: 26237705)