Public Abstract:
The proposal is to develop a plan to integrate a multidisciplinary team of scientists diverse expertise required to commercialize a clinically-relevant product using stem cells within 4 years.
Our disease target is hepatitis C which is the leading cause of hepatic cancer and the primary reason for liver transplantation in the U.S. This infectious disease afflicts 170 million people worldwide and its’ incidence is projected to triple over the next 20 years so that it will kill more people worldwide than AIDS. At present, there is no suitable antiviral therapy for hepatitis C. One reason for this is the lack of a suitable model system to study hepatitis C infection and the effectiveness of potential antiviral agents in the laboratory. Humans and sub-human primates are the only species that infect with HCV. Hence, there are no cost-effective, natural animal models to study hepatitis. A laboratory model system must include hepatocytes (liver cells which are the target of HCV) which can be infected by HCV in the laboratory, HCV must actively grow in these hepatocytes and the infected hepatocytes must themselves grow or survive in the laboratory for long periods of time so that their response to antiviral drugs can be assessed.
At present, HCV infection is studied in hepatocytes isolated from livers that are donated for transplant but found to be unsuitable for clinical use. These livers come from a pool of donors of diverse ages, genders, health status and ethnic backgrounds and their overall quality can also be highly variable. Regardless of overall quality, it is unusual for hepatocytes to survive in a highly functional state for more than a week in the laboratory and this severely limits the development of anti-HCV therapies.
We propose to use stem cells to produce hepatocytes for use in a unique laboratory model of human liver tissue. Instead of using isolated hepatocytes as a model, we grow liver tissue in three dimensions (as in the body) using not only hepatocytes but other cells found in the liver as well. These 3D tissues maintain liver function over extended periods in the laboratory and thus allow for the assessment of the effects of chronic drug exposure (commercialized application). A previous grant collaboration between members of this proposed team has demonstrated that these 3D tissues can be infected with and replicate hepatitis viruses C and D.
Stem cell-derived hepatocytes have several potential advantages over adult donor liver-derived hepatocytes for this project including the elimination of the hepatocyte sourcing and quality issues. We have already produced 3D liver tissues using mouse stem cell-derived hepatocytes.
The proposed team has expertise in hepatitis, stem cells and commercialization of FDA-approved tissue-based therapeutics. New personnel will be recruited to fill gaps. Goals are to advance a new HCV antiviral into the clinic and market a human liver 3D tissue-based antiviral screening platform in 4 years.
Statement of Benefit to California:
The incidence of hepatitis C (HCV) in the United States has been estimated at 1.8% [1], and more recently at 2.5% from a population-based sample of young women living in poorer neighborhoods in California [2], the state with the greatest number of HCV+ people. Computer modeling projects 165,900 deaths from chronic liver disease, 27,200 deaths from hepatocellular carcinoma, and $10.7 billion in direct medical expenditures for HCV from the year 2010 through 2019 [3]. During this period, HCV may lead to 720,700 years of de-compensated cirrhosis and hepatocellular carcinoma and to the loss of 1.83 million years of life in those younger than 65 at a societal cost of $21.3 and $54.2 billion, respectively [3]. HCV causes an estimated 8,000 to 10,000 deaths annually in the U.S. and accounts for 60 – 70 percent of chronic hepatitis cases, and 30 percent of cirrhosis, end-stage liver disease, and liver cancer cases. At least 75 percent of patients with acute hepatitis C ultimately develop chronic infection, and most of them have accompanying chronic liver disease. Liver failure from hepatitis C is the most common reason for a liver transplant. Currently, it is estimated there are about 170 million people worldwide who are infected with HCV, 4 million of those are in the United States.
The goal of this disease team planning proposal is the development of a human liver tissue model of HCV infection using liver cells derived from stem cells and to employ this model to advance new HCV antiviral therapies to the clinic. In addition to this direct benefit to the citizens of California, indirect benefits include development of novel core facilities and shared equipment resources, experienced collaborative research teams that can attract millions of dollars of additional funding to the state, spinout companies from new technology development, tax revenues and employment opportunities resulting from this new technology, new funding and spinout companies.
The program would also create a collaborative team spanning major liver transplant centers throughout California, facilitating patient access to treatments and the teams access to normal and diseased tissues and multiple clinical trial sites. {REDACTED} has been successful largely because of the strong biotechnology community in {REDACTED} with who {REDACTED} has partnered to develop and commercialize its products. These partnerships have brought millions of dollars of government grants to {REDACTED} as well as the promise of a growing, profitable tissue engineering and stem cell industry that will deliver innovative cell and tissue technologies to revolutionize patient care. There are few cities in the US that have the biotechnology infrastructure and collaborative environment that has enabled {REDACTED}’s success.
{REDACTED} received the 2007 Most Innovative New Product Award {REDACTED} for its first product, {REDACTED}. National press recognized our California company.
Review Summary:
Executive Summary
The applicant proposes a multi-disciplinary team to develop a 3D model of human liver including human liver cells from either human embryonic stem cells (hESC) or induced pluripotent (iPS) cells for use as an in vitro model for hepatitis C virus (HCV) infection. The goal is to develop this model as a screening platform for new antiviral therapies for hepatitis C and use it to develop and advance a new HCV antiviral into the clinic. Such a culture system could obviate the need for primary human hepatocytes, which are in limited supply. The Principal Investigator (PI) and his/her team have previously developed a 3 dimensional culture system to produce mouse hepatocytes.
Treatment for Hepatitis C is an important unmet medical need for this country as well as for the rest of the world. Hepatitis C infection is a major reason why patients undergo liver transplantation in this country and is the major risk factor for primary liver cancer. Current treatment options are limited with considerable side effects. Reviewers recognized the importance of a validated in vitro platform for Hepatitis C infection, to be used for screening new antiviral therapies. However, there was concern about the maturity of the science and the proposed team’s ability to achieve the stated goals in the time frame proposed in the application. Attempts to produce mature hepatocytes from hES cells have remained a challenge and differentiation of iPS cells to hepatocytes has not yet been achieved. Therefore, much development work will be required during the proposed project, and reviewers were not confident that the project would result in clinical studies within five years.
The PI has extensive experience in the area of tissue engineering including getting FDA approval for tissue engineered products. However, there was some concern among reviewers who felt that they had insufficient information from published literature or the application to evaluate the proposed concept. Reviewers recognized that certain applicant institutions must protect proprietary information, and often do not publish findings in the scientific literature. However, the absence of any publications by the PI or others in the relevant areas made it difficult for reviewers to assess the scientific basis of the proposed concept and the PI’s ability to bring the project to fruition.
The planning approach seems reasonable. The PI has assembled a good team of collaborators including an expert in molecular biology of hepatitis C virus. In addition collaboration with one of the major clinical liver centers in the United States is planned. However, the lack of stem cell biology and clinical expertise among the proposed team was of some concern to reviewers.
Overall review panel was not convinced that the applicant will be able to achieve the stated goals as outlined in the project, and the prospect of initiating a clinical study with five years seemed unlikely.
Reviewer One Comments
Concept:
Concept/ Rationale.
The authors claim to have developed long-term 3D culture systems with human hepatocytes and non parenchymal cells which exhibit phase 1 and phase 2 metabolism for several months. The system will be used to investigate HCV infection and propagation and ultimately to develop and test antiviral drugs. The authors correctly point out that human liver culture is quite variable so in addition to adult and fetal liver culture they suggest that iPS-derived hepatocytes would have advantages. They will generate iPS from somatic cells via gene transfection, induce differentiation to hepatocytes and fill the bioreactors with the cells and test for HCV replication and drug sensitivity.
Maturity:
A similar project to the one proposed here was funded by a SBIR project in collaboration with Stanford and Chiron/Novartis. There is no preliminary data included in the proposal from this research and no publications to support it. The maturity can not be determined from the application. It is not easy to make hepatocytes from hES cells and no one has done it from iPS cells. Much development will be required during the proposed project.
Significance. Unlike many other applications this proposal does not propose to take a product to a clinical application. The bioreactors would be used in drug development and testing and thus, would not be subject to the same FDA regulations as a cellular therapy, or even GMP conditions. This aspect would make the use of the devise easier if it worked as designed. This non-clinical application would presumably remain within the objectives of the program for funding.
Principal Investigator:
Brian Naughton, Ph.D. has extensive industry experience as co-founder of advanced tissue sciences. He has experience getting FDA approval for products such as the dermal replacement products TransCyte and Dermagraft. He has a record of considerable research support through SBIR applications in recent years. There are no peer-reviewed publications listed in the PI’s CV or the reference list describing the technology proposed in the application.
Planning Approach:
The projects list many highly qualified consultants, Ron Busuttil, Michael Houghton and others who will help direct the program. The scientific approach seems to have been already made. The proposal suggests that the consultants and other personnel will develop a project plan, identify personnel, and establish roles and responsibilities identify technology gaps and fill them, try to partner with drug companies for testing. The application list several gaps that they already recognize (iPSC technology, HCV infection, inexperience with patient and stem cell therapies, which is a plus.
Reviewer Two Comments
Concept:
The overall goal of this planning grant is to develop human liver cells from either ES cells or ES like cells induced by IPS as a platform to develop Hepatitis C antiviral drugs. Hepatitis represents a major clinical challenge and the P.I. has already developed an in vitro model to develop Hepatitis C based antivirals using human hepatic cells. However, given the paucity of cadaveric or biopsy material available, this group would now like to move this work toward human ES cells.
Overall although this is a solid proposal, in which the applicants purport to have already established liver cell cultures, the conclusion that they could use ES cell based technology to advance antiviral drugs to the clinic within 4 years seems unduly optimistic.
Principal Investigator:
The PI is a recognized leader in the world of commercial tissue engineering. However, he has not published any papers since 1995, so it is uncertain the extent to which the research findings outlined in this proposal are accurate. Also, the reviewer is not familiar with the group of liver clinicians that he has assembled for this proposal, so it is uncertain the extent to which this grouping represents a potentially high profile consortium.
Planning Approach:
This proposal is concise, but somewhat unrealistic in terms of being able to progress the use of stem cell based drug assays to develop antiviral drug therapies for hepatitis C in the time frame envisaged for these proposals.
Reviewer Three Comments
Concept:
This proposal by Dr. Brian Naughton proposes to develop a multi-disciplinary scientific team to develop an appropriate in vitro model for hepatitis C virus infection. Hepatitis C is certainly a very important problem in this country and throughout the world. It is the major reason why patients undergo liver transplantation in this country and the major risk factor for primary liver cancer. While therapy is currently available, it is non-specific immune modulating therapy plagued by significant side effects. A major drawback to the development of new agents for the treatment of hepatitis C has been the lack of a reliable in vitro model to study hepatic C virus infection. This group has already developed techniques for 3 dimensional cultured techniques using primary human hepatocytes. It is from this co culture technique that human hepatocytes have been demonstrated to possess differentiated cell function for much longer periods of time than standard model areas of primary hepatocytes. They have already demonstrated low level HCV and HDV delta replication in this model.
In this study they propose to utilize human embryonic stem cells to generate human hepatocytes and thus obviate the need for sources of primary human hepatocytes, which largely come from livers not utilized for liver transplantation. They have already demonstrated using mouse embryonic stem cells that this technique will likely yield cultures of primary hepatocytes.
The principle investigator has already assembled a number of very impressive collaborators including Jeffrey Glenn from Stanford University who was a MD, PhD student essentially defined the molecular biology of the delta virus. He is now also recognized as an expert in the molecular virology of HCV replication. He will also be collaborating with one of the major clinical liver centers in the United States at UCLA. In addition appropriate expertise in the molecular biology of the hepatitis C virus and biologic manufacturing is demonstrated.
My one concern is that there does not seem to be a collaborator who I would truly regarded as truly having expertise in stem cell biology.
It is also worth noting that Jeffrey Glen and James Dunn are described as transplant surgeons and neither is a transplant surgeon. Nonetheless, I think that the likelihood that this strategy will ultimately yield an appropriate in vitro model of HCV and HDV infection is high.
Principal Investigator:
The principal investigator is certainly very experienced in this area and has already brought several clinical therapies developed through tissue engineering to the clinic. He is extremely well funded in this area already and clearly has a track record of success. As I mentioned above he has assembled an impressive group of collaborators who only serve to increase the likelihood that this planning award will ultimately yield a model to study HCV replication in vitro. I am disturbed about one aspect of the proposal and that is that there has been a lack of publication in the scientific literature by the principal investigator. In fact, in his biosketch, he lists no publications since 1996. While I realize that much of his work has been proprietary, I do think that communicating findings in the scientific literature should be an important aspect of these awards.
Planning Approach:
The planning approach seems quite reasonable and well thought out. I do believe that the deliverables listed will likely be achieved. I do think that they will need additional expertise in stem cell biology, particularly when they move to working with human stem cells. They also may need additional expertise to that already identified in terms of bioengineering. Hopefully from this planning process will ultimately development such a model will we will finally be able to fast track new therapies for hepatitis C and hepatitis D to the clinic.
