Diabetes significantly impacts the quality of life and the economy of California since it is estimated that more than 2.7 million people are afflicted with this disease, costing the State $24.5 billion annually. Since the rate of success- full insulin independence – using islet transplantation is less than 10% five years after treatment, and this even with persistent immune suppression, there is an urgent need for a new cell-based therapy especially for type 1 (T1D) or insulin dependent diabetes. In addition, other obstacles to this therapy include the shortage of organs available for islet isolation aggravated by the need for more than 1 donor per recipient, the destruction of the engrafted islets by allogeneic rejection and autoimmunity, and concerns about the risk/benefit ratio because the persistent immune suppression increases the risk of cancer and infection and other metabolic disturbances including high lipids and hypertension.
Human ES cells (hESCs) could provide an unlimited source of endocrine β cells, and recent studies by biotech companies and academic labs have provided evidence that hESCs can be differentiated into pancreatic endocrine precursors and functional β cells. However, significant barriers remain. Thus there is a critical need to develop well-defined 'scalable' culture conditions that are free of animal products. The use of poorly defined animal products jeopardizes the safety and the utility of current protocols. In addition, current published protocols fail to offer strategies for the purification of β-cell precursor populations. In the absence of such a purification step, transplanted populations inevitably contain pluripotent cells that give rise to tumors in the transplant recipient. This is clearly unacceptable and urgently needs to be addressed.
Another major challenge facing hESC-based therapy of T1D is the allogeneic rejection and autoimmune destruction of engrafted islets. While cell encapsulation technology offers a potential strategy to protect the graft from the recipient’s immune system, its feasibility in the clinic remains questionable despite decades of research and development. Therefore it is of the highest priority to develop novel hESC-derived endocrine precursors that can escape the recipient’s immune system and avoid tumor development in the graft.
To resolve these critical issues, this grant encompasses a multi-disciplinary team to achieve the following four goals: To develop strategies to allow purification of hESC-derived endocrine precursors that could elude the recipient’s immune system; To establish chemical defined conditions to reproducibly differentiate hESCs into endocrine precursors; To validate in vivo that purified endocrine precursors can be used to treat diabetes in animal models without the risk of tumor development. Successful completion of the proposed research will greatly facilitate the clinic development of human ES based therapy for T1D.
Statement of Benefit to California:
This research would benefit the State of California and its citizens on multiple fronts. First and foremost, positive results will create a new development candidate of a cell-based therapy for type 1 diabetes with the potential for avoiding the risk of tumor formation - a consequence that hinders the development of any human ES cell based therapy. Second, it may obviate the need for immune suppression therapy that today carries serious side effects including propensity to infections and cancer, abnormalities in lipid metabolism and hypertension, and even damage to the transplanted cells as it occurs following islet transplantation procedures, the only available therapy nowadays for insulin-dependent diabetes. Avoidance of these complications represents a significant positive step in the reduction of health care expenses directly attributed to diabetes and its complications.
If successful, the approach involving the genetic modification proposed for the development of a cell product for diabetes in these investigations can also be utilized for the derivation of other therapeutically useful cells from human ES cells for human therapy, since the purification of cells of interest as well as avoiding teratomas risk and immune rejection are common bottlenecks for all human ES cell based therapy.
This Development Candidate Award application aims to provide a safe and efficient technology for large-scale generation of insulin-producing beta cells suitable for clinical application. The applicants hope to develop strategies for the purification of human embryonic stem cell (hESC)-derived endocrine precursors (EP) that could elude the recipient’s immune system, establish chemically defined conditions to reproducibly differentiate hESCs into EPs, and to validate the use of EPs to treat diabetes in an animal model without the risk of tumor development. The proposal describes three specific aims that are directed towards achieving these goals. The first aim is to introduce an antibiotic resistance gene into hESCs to allow efficient purification of hESC-derived EPs. The differentiation potential of purified EPs into functional beta cells, their teratoma risk and their efficacy and routes of delivery will be evaluated in vivo. In the second aim, the applicant intends to introduce two genes independently and together into hESCs in an attempt to achieve immune tolerance of these cells. The third aim is to develop reporter hESC lines for high throughput screening of small molecules to optimize chemically defined protocols to reproducibly differentiate hESCs into EPs.
Reviewers agreed that the proposed development candidate addresses an unmet medical need and if successfully established would have immense importance for the treatment of millions of patients with type I diabetes. However, the project faces many challenges for succeeding in the timeframe proposed and its immediate impact is likely to be low. Although the rationale for the development candidate is scientifically plausible and the approach has innovative aspects, the study is not fully supported by preliminary results.
The reviewers felt that the objective and aims are focused and logical, but the proposal was thought to be more exploratory and oriented towards answering fundamental questions and less directed towards achieving a well-defined development candidate. Some of the preliminary results presented are encouraging and demonstrate the capacity of the research team to introduce genes into hESC and to differentiate hESC into insulin-producing cells. However, preliminary results justifying the proposed roadmap to clinical translation are missing or insufficient. The cells constituting the development candidate have not been generated and the experimental models proposed are only partly in place, making it unlikely that the applicant will achieve the goals of the project within three years. Reviewers were uncertain if the proposed animal model is robust enough and felt that further optimization and validation will be required before it can be used to study whether the proposed genetic modifications enable hESC-EP to elude allogeneic rejection and autoimmune destruction. Reviewers also noted that the proposed screening assays were cumbersome in design, requiring a two-step process that will result in differentiation and expansion of cells over an extended time period. From a regulatory perspective, activities proposed for achieving a development candidate were thought to be incomplete and unlikely to support IND-enabling studies at the conclusion of the award period. It was noted that lead optimization studies for improving potency and specificity of differentiation-promoting compounds involves different classes of molecules, when it might be better to select a lead candidate at the onset of these studies since otherwise, many of the studies would need to be repeated to confirm comparability, including tumorigenicity assessment. Additionally, tumorigenicity assessments will need to be conducted via the intended route of administration for at least 10 to 12 months. No information was evident with respect to the dose, number of animals, and time points that would be used. Different routes of administration will be tested though it is unclear which criteria would be used for transplantation site selection. There is also no information about manufacturing. Milestones are provided as research to be performed, and no specific timelines are presented.
Reviewers highlighted the principle investigator’s (PI) strong record of scientific achievements supporting his/her qualifications to lead the proposed project. However, it was not evident that the individual has any previous experience in developing a candidate for clinical use. The PI has assembled a multidisciplinary team suitable for the work proposed. No formal plan for communication and coordination among team members is provided. No budgetary concerns were identified. Proposed collaborations were thought to be critical to the success of the project and evidence of collaborator commitment is presented. Relevant assets for the clinical application of the tentative development candidate were not presented. Resources, facilities and major equipment critical to the success of the project were considered appropriate.
Overall, reviewers felt that this proposal would not result in a development candidate ready for IND-enabling studies in the time proposed due to several weaknesses regarding study design and feasibility. The PI and research team bring strength to the proposal through their track record of scientific achievements, but it was unclear that this team has had significant experience in bringing development candidates to the clinic.