Stem Cell-Derived Astrocyte Precursor Transplants in Amyotrophic Lateral Sclerosis
Amyotrophic lateral sclerosis (ALS), a lethal disease lacking effective treatments, is characterized by the loss of upper and lower motor neurons. 5-10% of ALS is familial, but the majority of ALS cases are sporadic with unknown causes. The lifetime risk is approximately 1 in 2000. This corresponds to ~30,000 affected individuals in the United States and ~5000 in the Collaborative Funding Partner country. There is currently only one FDA-approved compound, Rilutek, that extends lifespan by a maximum of three months. Although the causes of ALS are unknown and the presentation of the disease highly variable, common to all forms of ALS is the significant loss of motor neurons leading to muscle weakness, paralysis, respiratory failure and ultimately death. It is likely that many pathways are affected in the disease and focusing on a single pathway may have limited impact on survival. In addition, as ALS is diagnosed at a time that significant cell loss has occurred, an attempt to spare further cell loss would have significant impact on survival.
Several findings support the approach of glial (cells surrounding the motor neurons) transplants. Despite the relative selectivity of motor neuron cell death in ALS, published studies demonstrate that glial transporters critical for the appropriate balance of glutamate surrounding the motor neurons are affected both in animal models and in tissue from sporadic and familial ALS. The significance of non-neuronal cells in the disease process has been well characterized using SOD1 mouse models representing many of the key aspects of the human disease. In addition, transplantation using glial-restricted precursors (GRPs) that differentiate into astrocytes in SOD1 mutant rats has been shown to increase survival. Motor neurons have a process, the axon, up to a meter in length which connects the cell body to its target, the muscle. The ability to appropriately rewire and ensure functional connections after motor neuron replacement remains a daunting task with no evidence to date that this will be possible in humans. Therefore, we will focus on the development of an ALS therapy based on hES-derived astrocyte precursor cell transplants to prevent the progression of ALS.
Our proposed project will develop clinical grade stem-cell derived astrocyte precursor transplants for therapy in a prospective Phase I clinical trial. We will: 1) generate astrocyte precursors from three different sources of human embryonic stem cell (hESC) lines; 2) identify the hESC line and glial progenitor combination that has the best characteristics of minimal toxicity, best efficiency in generating astrocytes, and reducing disease phenotypes in vivo in a rat model of ALS; 3) manufacture the appropriate cells in a GMP facility required by the FDA; 4) work with our established clinical team to design a Phase I safety trial; and 5) submit an application for an invesitgational new drug (IND) within the next four years.
Amyotrophic lateral sclerosis (ALS; also known as Lou Gehrig's Disease) is a common and devastating adult motor neuron disease that afflicts many Californians. In the absence of a cure, or an effective treatment, the cost of caring for patients with ALS is substantial, and the consequences on friends and family members similarly takes a devastating toll. Our goal is to develop a safe and effective cell transplant therapy for ALS by starting with human embryonic stem cells. If successful, this advance will hopefully diminish the cost of caring for the many Californians with ALS, extend their useful lives, and improve their quality of life. In addition, the development of this type of therapeutic approach in California will serve as an important proof of principle and stimulate the formation of businesses that seek to develop these types of therapies in California with consequent economic benefit.
Considerable progress was made on transitioning cells and cell production methods from research-scale to translational/clinical scale. Specifically, Year 1 activities were focused on transitioning from research to pilot-scale cell production methods, and characterization of the animal amyotrophic lateral sclerosis (ALS) disease model. These activities were essential because cellular therapy development is a multi-stage process with increasing stringency over time in terms of the increased focus on the details of the methods, stringent requirements for reagents/materials, greater scale, and more thorough product characterization during the transition from early research to an approved cellular therapy.
During Year 1, small-scale embryonic stem cell (ESC) growth and differentiation methods previously developed for research at Life Technologies were further developed at a larger pilot-scale, which provided enough cells to perform early animal pre-clinical studies and cell characterization. In addition to the increased scale of cell production, where possible, research grade reagents and materials were substituted with reagents and materials that would be required or preferred for producing a cell therapy for use in humans [produced under Good Manufacturing Practices (GMP), non-animal origin, well characterized]. These conditions are not ideal for many ESC lines, and only 1 of the 4 starting ESC lines was able to adapt successfully to these culture conditions. To increase the number of potential clinical ESC candidate cell lines, we acquired 2 additional ESC lines, UCFB6 and UCSFB7 from the University of California, San Francisco. Development is ongoing to ensure the cell processing methods are robust and scalable for the increased cell numbers required for the large-scale animal studies in Year 2. Cells from the pilot-scale production are being subjected to deep sequencing as part of the development of molecular characterization methods that may provide future quality control assays.
During Year 1, further studies of a rat ALS disease model were performed to: 1) optimize cell injection methods; 2) improve characterization of disease onset and progression in the rat model; 3) evaluate the utility of behavioral and electrophysiology tests for following the disease; and 4) evaluate histology methods for measuring neuron damage and detection of implanted cells, which will be used to optimize the large-scale efficacy studies planned for Year 2. We discovered that several time-consuming analysis approaches for efficacy evaluation could be replaced by simpler, more cost effective approaches. Additionally, the Year 1 studies tested and ensured that the team could handle an aggressive cell implant schedule, twice daily immunosuppression, demanding behavioral and electrophysiology assessments, and extensive histology evaluations.
Considerable progress was made on transitioning cells and cell production methods from research-scale to translational/clinical scale, including initial cell production in a GMP facility with GMP compatible production methods. Additionally, extensive characterization of the amyotrophic lateral sclerosis (ALS) disease animal model was completed and cells were evaluated for potential efficacy in this ALS disease animal model. These activities are key for continued progress in cellular therapy development, which is a multi-stage process that requires increasing focus on the details of the methods, stringent requirements for reagents/materials, greater scale, and more thorough product characterization during the transition to an approved cellular therapy.
Specifically, we made significant progress in three major areas:
First, we found evidence for efficacy using neural stem cells made at Life Technologies. In brief, during Year 1, the rat ALS disease model was shown to be a more aggressive disease model with an earlier disease onset and more rapid progression to end-stage and death than the model that had been used in previous studies. During Year 2, this more aggressive ALS disease model was further characterized with the identification of a reliable marker of disease onset, and demonstration that alpha motor neuron sparing by implanted cells could be detected and measured even, despite the aggressive nature of disease progression in this rat model.
We found that H9 NSCs produced by Life Technologies, when implanted into the rat ALS disease model, survived, migrated extensively into the area where alpha motor neurons are located, differentiated into cells that appear to be astrocytes, and provided a protective effect for the alpha motor neurons. This protective effect was determined by comparing the survival of alpha motor neurons on the side of the rat spinal cord where NSCs were implanted with the side of the spinal cord that did not have cells implanted. The side of the spinal cord where the NSCs were implanted showed approximately 10% more surviving alpha motor neurons than the matching side of the spinal cord that did not have cells implanted.
Second, cells from the various production methods were subjected to gene sequencing as part of the development of molecular characterization methods. This sequencing information was critical to identify whether cells produced by various methods were typical for the cell type, or exhibited qualities that indicated they were not optimal cell populations. These methods will be used to identify optimal markers for characterizing cell populations as part of current cell production development and for future quality control assays.
Third, during Year 2, Life Technologies further developed their pilot-scale embryonic stem cell (ESC) growth and differentiation methods to be more easily adaptable to cell production under Good Manufacturing Practices (GMP). This involved increasing the scale of cell production, and where possible, substituting reagent grade reagents and materials with reagents and materials that would be required or preferred for producing a cell therapy for use in humans (produced GMP, non-animal origin, well characterized). These conditions are not ideal for many ESC lines, and in Year 1, only one (H9) of the 4 starting ESC lines was successfully adapted to these culture conditions, however, 3 additional ESC lines were acquired to increase the number of potential clinical ESC candidate cell lines. One of these ESC lines (UCSFB7 from the University of California, San Francisco) was successfully adapted to the pilot ESC culture conditions, and resulted in the production of NSCs, and with AP production in progress. Because the research version of ESC line H9 has been used to successfully produce NSCs at Life Technologies, agreements are in progress for City of Hope for NSC cell production using the H9 ESCs, that have been banked under GMP conditions at City of Hope. In addition, pilot-scale cell production was initiated earlier than originally planned at the University of California, Davis GMP facility. The plan is to produce NSCs and APs under conditions that UC Davis has found to be successful in the past, and transition these methods to GMP compliance. To date, UC Davis has produced ESCs from 3 ESC lines [UCSF4, UCSF4.2 (a.k.a. UCSFB6) and UCSF4.3 (a.k.a. UCSFB7] and has produced NSCs from ESC line UCSF4. The UCSF4 NSCs are scheduled to be shipped to UCSD for testing in the ALS disease animal model in early June, 2012, and NSC production from ESC lines UCSF4.2 and UCSF4.3 is expected to begin in late June 2012.