Tools and Technologies I
The directed differentiation of human embryonic stem cells (hESCs) to high purity cell populations provides tremendous promise for drug discovery. Drug screening involves application of hundreds of thousands of novel drug candidates, one at a time, into a single plastic well containing a cell population, in order to identify one drug that has a beneficial effect on the cell population. This field is severely limited by a lack of high purity human cells to use in the screens. To date, drug candidates are tested on non-human cells, or immortalized human cell lines that have extremely little similarity to a normal human cell. This leads to errors in the identification of candidate drugs, which in turn leads to an immense wastage of money, time and resources, as well as an increased risk to humans participating in the first human tests of the candidate drug. Thus, differentiated human cells in high purity would provide ideal alternatives to the use of non-human cells or immortalized human cell lines for drug discovery, allowing highly relevant human data collection early in the screening process. We have developed a method to generate one human spinal cord cell type, motor neuron progenitors (MNPs), in large quantity (billions per week) and extremely high-purity (>98%) from hESCs. Motor neurons are lost in amyotrophic lateral sclerosis (Lou Gehrig's disease), spinal muscular atrophy, spinal cord injury, polio, and many other spinal cord diseases. Furthermore, we have seeded these high purity cells into 2 different models of conventional drug screening plates, containing either 96 or 384 wells, and validated a shipping system to ensure domestic or overseas shipment in a format that is ready to use. We have also developed methods to generate hESC-derived brain neuron cells and heart cells in large quantity (billions per week) and extremely high-purity (>98%), but we have not yet put these cells into drug screening wells. The overall goal of this program is to expand and optimize our 96 and 384 well drug screening programs to enable screening of millions of candidate drugs by the broader research and pharmaceutical communities. AIM 1 will optimize cell survival in the wells, consistency of the product, shipping, and quality control oversight for the application of MNPs to drug screening plates. AIM 2 will apply high purity human brain neuron cells to drug screening plates, then optimize as in AIM 1. AIM 3 will apply high purity human heart cells to drug screening plates, then optimize as in AIM 1. Ours is the first practical example of drug screening plates seeded with high purity human cells derived from any stem cell type. The optimization of this approach will provide an enabling hESC-based technology that will drastically decrease the hit to lead cycle time of drug discovery while providing a more relevant human safety profile.
Statement of Benefit to California:
The proposed research will benefit California by preserving and strengthening the State’s position as a leader in the field of stem cell therapeutics. Through the passage of Proposition 71 and subsequent establishment of the California Institute for Regenerative Medicine, the voters of California have identified stem cell research as a key area of focus for the state, with anticipated positive impacts including the creation of biotechnology jobs, attraction of leading researchers to California universities, creation of valuable intellectual property, and advancement of therapeutics beneficial to California residents. Our screening plate technology represents the first hESC-based drug discovery technology to have been commercialized in the world. Thus, this approach is the first to validate the State’s support of stem cell research and its application. This program has already led to job creation, tax revenue and other financial and reputation benefits; its advancement will lead to more. Additionally, hundreds of California-based companies and academic laboratories stand to benefit from this product if its development is successful.
This application proposes the scale-up, optimization and validation of a high throughput screening platform for human embryonic stem cell (hESC) derivatives. The three cell types to be adapted to this platform are all derived from hESC and include motor neuron progenitors (MNPs), neural progenitors and cardiomyocytes. The applicants have previously developed methods for the generation of large quantities of these differentiated derivatives in high purity, and developed a small scale plating system for MNP. They propose to scale up and optimize these technologies and to apply them to neural progenitors and cardiomyocytes as well to generate a hESC –derived screening platform for drug discovery. The reviewers were enthusiastic about the technology described in this proposal but were uncertain of its feasibility. Compelling preliminary data was provided that convinced the reviewers that expanding and optimizing the screening platform with hESC – derived MNP could be achieved, but the lack of similar data for the other hESC derivatives was of concern. In addition to this perceived risk, some reviewers questioned the relatively limited track record in this area of the Principal Investigator but consider the overall team capable. In the end, the reviewers were not convinced of the overall feasibility given the uncertainty of successfully applying the technology to two of the hESC derivatives. The reviewers indicated that the potential impact of this work is very high and addresses a current roadblock in stem cell science, the need for optimization and scale up hESC-based technologies. Specifically, the proposed high throughput screening platforms based on hESC derivatives would be immediately useful for drug discovery. The reviewers had mixed feelings about the feasibility of this proposal due to disproportionate strengths of the preliminary data, leading t least one reviewer to consider the proposal high risk but potentially high reward. The applicants convincingly demonstrated their ability to produce and ship assay-ready, 96 well plates of high purity hESC-derived cells that express motor neuron markers. Encouraged by these results, the reviewers were enthusiastic of the feasibility of further expanding, optimizing, validating and shipping a motor neuron progenitor screening platform. The preliminary data however, was very minimal or completely lacking for cardiomyocytes and neural progenitors. Without additional studies for these progenitors, the reviewers were unable to assess the feasibility of applying the technologies, including scale up, to these cell types. One reviewer was concerned about the use of hESC lines that were derived by the applicants and have not been examined by other groups. Another minor criticism was that the functional assay was not actually “real-time”, at least not as outlined by the applicants. One reviewer wondered whether alternatives for this assay hadn’t been considered that might be more appropriate. Most of the reviewers felt that the applicants were well qualified to conduct the studies in this proposal. The research environment was also considered to be a strong asset. There was some concern that the principal investigator seemed inexperienced and not widely known through publications, but the overall feeling was that the supportive setting and encouraging preliminary work spoke well to the capabilities of this team. In summary, the proposed technology would be a major asset to the field, but the reviewers’ enthusiasm was tempered by the uncertainty of success. PROGRAMMATIC REVIEW A motion was made to move this proposal to Tier 2. The reviewers agreed that the first aim was strong and feasible, and the motor neuron focus could positively impact the important area of ALS research. Most agreed that Aim 1 is of sufficiently high impact to warrant consideration on its own. The reviewers were enthusiastic about this possibility, providing the budget was appropriately modified. The amended motion to move to Tier 2, and if funded, to limit to Aim 1, carried.