A flexible system for the safe, rapid, and efficient isolation and sensitive biosafety testing of hESC derivatives, leading to FDA-approved products for cellular therapies
Tools and Technologies I
In embryonic stem cellsí path from the bench to the bedside, there are several very important safety studies that must be done before therapies can be brought to patients in safe and effective clinical trials. Our application focuses on two key areas recently identified by the FDA: the ability to cleanly sort hESC derivatives away from primitive cells that can form teratomas, and the ability to test the safety of hESC derivatives in extremely sensitive assays. Our technologies will allow the field to mov forward through these current bottlenecks in the minimal amount of time, because we use methods and reagents that we have had previously approved by the FDA for cellular therapy trials. They are now modified to fit uniquely to the specialized problems of hESC selection and safety testing. We also have 20 years experience in developing and conducting clinical cellular therapy trials and in demonstrating to the FDA that safety comes first. We are developing clean and effective sorting strategies using immunomagnetic isolation technology with cell surface markers currently in use in clinical trials of adult stem cell therapies. This isolation strategy is more realistic for hESC isolation than flow cytometer-based sorting, the other alternative, because it is gentler on the cells, takes only two hours for a clinical dose, and gives a higher viable cell yield. The isolation marker is transiently produced on the surface of the specific derivatie cell type of interest, just long enough to allow the sorting (without manipulation of the genome). The cells are also safety modified to allow better levels of confidence by the ability to eradicate primitive cells. Our sorting systems are highly flexible, and are developed in conjunction with 20 disease teams, 14 at our University and 6 at collaborating sites. The methods developed in the current proposal will benefit all teams, plus others who would like to cross-reference our Standard Operating Procedures and investigational New Drug applications (INDs) in the future. Our flexible technology development is a good value since it will have wide-spread utility for hESC-based clinical trials. We also have a novel, most sensitive model available for validating the safety of the isolated products for cellular therapy, and have just completed a decade-long safety study examining adult stem cells. These models, which detect injected cells with single cell sensitivity and can allow dynamic in vivo visualization for tumor surveillance, will be available to all disease teams for teratoma testing. All previous cellular therapy trials have used adult stem cells. Our mission in the current proposal is to continue to bring our tools and techniques that have led to previous approvals by the FDA now to the field of hESC therapy. We will perform safe and effective hESC-based therapies in our [REDACTED] GMP facility after the proposed scale-up process is conducted at the level of ìgood laboratory practice”.
Statement of Benefit to California:
California is leading the way in human embryonic stem cell research, due to CIRM funding, allocated by taxpayers via proposition 71. But several bottlenecks exist in our efforts to safely and effectively bring exciting advances to the clinic, to bring cures to our community members. The present application addresses two such bottlenecks recently identified by the FDA: the ability to cleanly sort hESC derivatives away from the primitive cells, which retain the potential to form teratoma, and the ability to test the safety in extremely sensitive in vivo assays. The PI and co-Director have each had two decades of experience in human stem cell sorting and manipulation at the clinical level, and testing biosafety of the cellular therapy products to obtain approvals by the FDA. All previous cellular therapy trials have used adult stem cells. Our mission in the current proposal is to continue to bring our tools and techniques that have led to previous approvals by the FDA to the field of hESC therapy. We are unable to advance further in our goals without funding from the CIRM, since this type of scale-up technology development with new hESC lines cannot be funded by federal allocations. CIRM has generously funded renovation of our good manufacturing practice facility, where these clinical trials will take place after the proposed scale-up and validation process. We are collaborating with 20 disease teams, 14 at our University and 6 at collaborating sites in California, and the flexible methods that we are developing in the current proposal will benefit all teams, plus others who would like to cross-reference our Standard Operating Procedures and Investigational New Drug applications (INDs) in the future, for their own therapies. Our technologies use methods and reagents that we have had previously approved by the FDA for cellular therapy trials. They are now modified to fit uniquely to the specialized problems of hESC selection and safety testing. Our flexible technology development is a good value since it will have wide-spread utility for hESC-based clinical trials throughout California, and for our affiliated collaborators.
In a recent meeting called by the FDA to discuss safety considerations for human embryonic stem cell-derived cellular products, several concerns were highlighted. The most prominent of these was the concern that undifferentiated stem cells transplanted in a mixed cell population could lead to teratoma formation in the host. All hESC differentiation protocols discussed at the April 2008 FDA meeting relied on the differentiation protocol to gradually exclude undifferentiated hESCs from the final cell product, without the use of any separation methodology to definitively exclude undifferentiated hESC. Thus, a major concern in the field is that clinical trials in which residual undifferentiated cells result in teratoma formation could not only damage individual patients, but damage the entire field of cell therapy. The goal of this application is to move the field through the bottleneck of potential tumor formation by the development FDA-approvable technologies for: 1) the modification of hESC to allow elimination of residual undifferentiated cells that could cause adverse events upon administration – ‘safety-modified hESC’; 2) the isolation of hESC derivatives; and 3) the testing of for residual undifferentiated hESC in populations of hESC derivatives in a novel and highly sensitive xenotransplantation model. The FDA is likely to require that any product or cell originating from hESC is demonstrably free of undifferentiated cells, which have innate potential to form teratomas. Hence tools and technologies that assure absence of undifferentiated hESC and back-up strategies to eliminate such cells after transplantation, could have major impact on translation of hESC-derived cell therapies. However, overall the reviewers felt that the proposed research design lacked important methodological details and was largely an extension of work going on in many other groups, rather than a novel approach. Reviewers appreciated that the proposal was straightforward and generally well-organized and well-written by experts in the field, though one reviewer found the application overly complicated. Reviewers noted that the proposal employed many clever techniques and approaches. However, they noted that while the workflow as presented seemed logical and feasible, almost the entire project seemed to describe work already in progress. The Principal Investigator (PI) proposes to adapt technology previously developed for adult stem cells, to generate hESC modified to allow their elimination - ‘safety modified’ hESC. Reviewers were unclear on the conditions to generate single site safety modified hESC and how easy if would be to isolate the individual singly-modified hESC clones. Following characterization, appropriate clones would be expanded under GMP conditions and master cell banks prepared and qualified. Reviewers noted that the H1 line was to be the starting line and expressed reservations about the use of this line given its exposure to animal products and availability usually only at high passage number. Similarly, the PI proposes to adapt technology previously developed for the immunomagnetic isolation of adult stem cells for clinical use, for the isolation of cells differentiated from hESC. Again, reviewers commented that insufficient detail was provided on the modification of standard methods so that they were unable to fully assess the feasibility of the proposed approach. The technologies proposed, in conjunction with the safety modification of hESC should lead to a population of differentiated cells free of undifferentiated hESC contamination, which can be tested in a highly sensitive xenotransplantation model. The reviewers uniformly commented that the PI is very experienced and well qualified for this project in that s/he has been working for many years in cell therapy development. The assembled team is excellent. Reviewers commented that that supply component of the proposed budget seemed very high. Overall, while acknowledging the expertise of the PI and the team and the importance of this work for the clinical application of hESC; reviewers considered the proposal to be lacking in some important experimental detail and found much of this work to be an extension of work already underway.