New Faculty I
$3 072 000
This proposal will define the biology of stem cell engineering to produce a cancer-fighting immune system. The immune system protects our body against most outside threats. However, it frequently fails to protect us from cancer. The T cell receptor (or TCR), a complex protein on the surface of an immune cell (or lymphocyte), allows to specifically recognize cancer cells. The TCR functions like a steering wheel for lymphocytes, allowing them to travel around the body and specifically find and attack cancer cells. The goal of this research is to put TCR genes into stem cells to generate a renewable source of cancer-fighting lymphocytes. The stem cells will serve as the progenitors of cancer killer lymphocytes. My collaborators from Caltech have demonstrated that inserting the TCR genes into bone marrow stem cells allows them to pass on the TCR into lymphocytes, which then become cancer-targeted. Also, my collaborators from UCLA have demonstrated that human embryonic stem cells can be differentiated into blood stem cells, and these can be differentiated into lymphocytes re-directed to fight cancer through the expression of the TCR. The studies in mice provide compelling evidence that inserting TCR genes into stem cells has several advantages for the progeny lymphocytes, allowing them to better fight cancer. The next step is to bring this approach to patients with cancer. I have dedicated the past 10 years to make the transition from studies in mice to the bedside. I have gained the expertise to conduct clinical trials using cells as targeted drugs from patients. This experience has allowed me to design and start working on the clinical trials that will test the concept of inserting TCR genes into progenitors of lymphocytes and give them to patients. With my collaborators at Caltech, UCLA and USC we have raised the adequate resources from private foundations and the NIH to initiate clinical trials inserting TCR genes into lymphocytes. I request additional funds from CIRM to allow me to extract the most information from the clinical trials and then help take them one step further by ultimately testing the use of embryonic stem cells to engineer a cancer-fighting immune system. There are several challenges that need to be addressed, including what is the best approach to generate both immediate and long-term cancer fighting cells, what are the optimal stem cells to target, and how they should be manipulated and given to patients in the clinic. The study of samples obtained from patients participating in pilot clinical trials will provide information how to design new clinical trials using the method of inserting the cancer-specific TCR genes into stem cells. The experience of regenerating a cancer-fighting immune system in humans could then be applied to multiple cancer types and to infectious diseases that currently lack good treatment options.
Statement of Benefit to California:
Multiple preclinical studies have validated the concept that the immune system can be harnessed to fight cancer. However, clinical testing has failed short of expectations. I propose to genetically program the immune system starting from stem cells with the hope of advancing cancer immunotherapy. Malignant melanoma will be the cancer for the initial testing of this approach. Melanoma has a track record of being “immune-sensitive” and there are well-defined antigens against which the immune system can be targeted. Melanoma is the cancer with the fastest rising incidence in the U.S., and there is no evidence of slowing down anytime soon. This disease impacts heavily in our society, since it strikes adults at the prime years of life (30-60 years old). In fact, melanoma is the second cancer cause of lost of productive years given its incidence early in life and its high mortality once it becomes metastatic. The problem is particularly worrisome in areas of the world like California, with large populations of persons originally from other latitudes with much lower sun exposure and with skin types unable to handle the increased exposure to ultraviolet (UV) light in California. Although most frequent in young urban Caucasians, melanoma also strikes other ethnicities. In fact, the incidence of acral melanoma (non-UV light induced melanoma that develops in the palms and soles) has steadily increased in Hispanics and Blacks. Early melanoma can be cured with surgery. Therefore, programs aimed at early detection have the highest impact in this disease. Once it becomes metastatic, melanoma has no curative standard therapy. Despite this grim outlook, it has been long known that occasional patients participating in experimental immunotherapy protocols have long remissions and are seemingly cured. This proposal aims at incorporating the most current knowledge arising from preclinical research and prior clinical experimentation of immunotherapy strategies to engineer the immune system genetically to better fight metastatic melanoma. Bringing new science from the laboratory to the bedside requires well-designed, well-organized and informative clinical trials. It is not enough to show some responses, we need to understand how they develop and why some patients respond and other do not. Therefore, the analysis of stem cell-based immune system engineering within clinical trials proposed herein requires thorough analysis of patient-derived samples to inform the follow-up clinical testing. Information resulting from the genetic engineering of the immune system in patients with melanoma will help develop studies to direct the immune system to fight other cancers and infectious diseases like HIV. Once optimized, I envision the ability to clone T cell receptor (TCR) genes specific for tumor or infectious disease antigens expressed by different cancers or infectious agents, and use these TCRs to genetically program the patient’s immune system to attack them.
SYNOPSIS: The overall goal of this translationally-oriented proposal is to develop optimal strategies for introducing tumor-targeting T lymphocytes into patients suffering from melanoma. cancer and chronic infectious diseases. This paradigm has been demonstrated in mouse models. The grant builds upon an in-progress clinical trial in which TCR transgenes will be inserted into patient lymphocyte populations, and eventually into blood precursor cells, in the hope that this will enhance the efficacy of the tumor-directed immune response. In the current proposal, the applicant will first analyze blood samples taken from these patients. Sample cells will be cultured under different conditions to try to optimize the derivation of transgenic TCR-expressing "T memory stem cells", which he defines based on cell surface markers (activation markers, homing receptors, and cytokines and cytokine receptors) that previously have been established to mark mouse memory T cells. In a second aim, the applicant will use a mouse melanoma model to examine the efficacy of transgenic TCR delivery via HSC or ES cell transduction. Clinical translation of these findings to humans with MART-1+ melanoma is also proposed, at least for HSC transduction. The applicant also indicates that some effort will be devoted to "positioning" the team to move in the future into an hESC based clinical trial, though what this effort will entail is not clear. STRENGTHS AND WEAKNESSES OF THE RESEARCH PLAN: This work addresses an important issue in cancer biology and cancer immunology, in that it attempts to harness the body's intrinsic immune responsiveness to combat malignancy. The aim of enabling the treatment of serious cancers makes this proposal very significant and the approach adopted could lead to benefits beyond the immediate target disease. Each of the project aims has multiple subparts, in most of which the PI or his colleagues, have had experience. Some of the experiments described are funded by on-going clinical trials with support from this application picking up important basic science analyses. The selected staff are well qualified with long standing experience in the type of work proposed. The timeframes required to achieve the work, including regulatory background work, are well understood by the applicant. The difficulties of clinical translation are also clearly well understood by the authors and there is sufficient background work for this proposal to indicate that significant contingencies may not be necessary. The PI has clearly done a remarkable job in recruiting the funding and infrastructure to enable the initiation of this significant clinical trial at UCLA. He shows innovation in attempting to maximize the possible scientific discovery that can be achieved from the patient samples and data that will be collected through the course of this trial. The experiments leading up to the translational clinical trials are better described than the clinical trials themselves, which is a distinct weakness in the narrative. Although it would be speculative at this point, more details about clinical trial designs would have been welcome. Nonetheless, the concept behind designing memory T cells to fight tumors and chronic infections has been around a long time, with numerous animal model studies lending support, but translating the basic science into clinical trial stages has been frustratingly slow. This proposal intends to facilitate the translation in some innovative ways (using “bedside to bench” observations), but a high level of enthusiasm for the project as a whole must include the belief that the skill and background of Dr. Ribas’s team will fill in the gaps for the clinical trial details when that time comes. The central hypothesis for this proposal relates to the sustained renewal of genetically modified, tumor-directed lymphocytes in patients. One reviewer, however, felt that investigating this possibility is not a primary focus of the planned investigation as presented, since there does not appear to be any consideration of the time period over which this renewal is needed or how it can be promoted and analysed. The applicant plans to use stem cell biology as a tool to achieve this renewable, constant supply of tumor-directed lymphocytes; however, the proposal does not appear to be centered on fundamental issues in stem cell biology per se. The proposal develops existing ideas for the use of recTCR-transduced lymphocytes and, whilst hESC work is indicated, no details are given other than to suggest that human eggs and embryos may be used. The mention of the use of such cells indicates a long term plan to develop hESC lines and to carry out SCNT but this is not otherwise evident in the proposal. The main focus of this project would no doubt, if successful, have significant clinical impact for certain cancer patients, however, the likely impact in basic stem cell research is less clear. The first aim, characterizing the phenotype of T cells generated under different conditions of differentiation and at different timepoints after T cell infusion into patients appears relatively straightforward; however, it is not clear that the assays proposed will achieve the desired goal of quantitatively determining the presence of "T memory stem cells". As the applicant defines them, T memory stem cells are "a subset of memory T cells with high capability of self-renewal"; however, none of the assays described directly measures self-renewal activity, and the surrogate markers proposed have not been validated functionally in the human system. Thus, it is unclear whether conditions that give populations of cells with a particular cell surface profile or cytokine responsiveness will be optimal for maintaining TCR transgenic cells in the patient. Surprisingly, no correlation analysis with patients' clinical parameters is proposed. In the second aim, the applicant proposes pre-clinical studies in mice to determine whether delivery of transgenic T cells via transduction of HSC will provide longer lasting T cell chimerism. The PI suggests that this strategy may be advantageous also because the HSC-derived T cells will not exhibit endogenous TCR rearrangements. However, in studies of germline transgenic mice, endogenous TCRs do show some degree of rearrangement, unless generated on a RAG-deficient background. The PI does not directly specify which strains of mice are to be used, does not mention RAG-deficiency, and does not comment on how endogenous rearrangements could affect the outcome of these experiments. In addition, there is no information about how HSC will be obtained, whether donors will be allogeneic or syngeneic, or how transductions will be performed to ensure maintenance of reconstituting potential. No preliminary data is given to indicate the efficacy of this system for chimera generation. Finally, the section describing hESC-related experiments is very vague. The rationale provided for these experiments - that they would become an "off-the-shelf cell therapy", is problematic, in that this would require a large bank of HLA-matched hESCs, which are not currently available. The applicant does not discuss this issue, or provide information on what degree of mismatches could be tolerated in such a system, or how useful existing lines would be. As such, it is not clear that transduction of unrelated hESC lines represents a preferred approach over transduction of purified, patient-derived T cells or HSC. QUALIFICATIONS AND POTENTIAL OF THE PRINCIPAL INVESTIGATOR: Dr. Ribas obtained his MD in 1990 from the University of Barcelona and his PhD in 1993 from Autonomous University of Barcelona. He completed postdoctoral and clinical training at UCLA and became a Clinical Assistant Professor in 2001, an Assistant Professor in 2003, and then an Associate Professor in 2006. He is clearly an exceptional physician-scientist with a great degree of energy and skill. He has accomplished a great deal in only a short time at UCLA and clearly has earned the respect of his colleagues in his ability to bring clinical research programs to fruition. He has tremendous potential to become a leader and make important contributions to clinical cancer therapy, but its not clear that his profile would be as significantly developed in stem cell research. The PI’s medical qualifications appear to be excellent and well focused within the project. The PI has a substantial number of grants established and the local coordination and support is solid for his proposed program. One concern is that his efforts may be spread to thin. His existing committed effort will total at least 71% at the time at which CIRM funding would begin, and this is spread over 14 different projects. Though some of these projects are overlapping, there are concerns about the degree to which he could truly focus on any one aspect of these studies, particularly since he still must give 20% of his effort to clinical activities outside research. The applicant provides a thoughtful and compelling career development plan that takes advantage of his unique expertise and skills as a physician-scientist. He receives appropriate mentorship from leaders in the field (e.g., David Baltimore, Owen Witte, James Economou), who will help him transition his work into stem cell biology. He also has sought didactic training in relevant areas, and this will help him build a better background in basic research. However, his proposed career development plan appears to revolve around sustaining current interactions rather than thrusting into new areas. In the new proposed area of work there does not appear to be a development plan for Dr Ribas. Additionally, the development goals did not appear to be readily measurable and there seemed to be a strong focus on delivery of a clinical trial which it is claimed is not the primary intention of the proposal. INSTITUTIONAL COMMITMENT TO PRINCIPAL INVESTIGATOR: UCLA has clearly made a significant investment in this young scientist. They have provided him with a large amount of laboratory space, start up funding, and protected 80% of his time for academic pursuits. His lab is optimally positioned adjacent to the UCLA GMP suite and the hESC core. He also receives significant mentoring from individuals such as Owen Witte, David Baltimore, and Mike Phelps, who are also collaborators on the current project. The institution has recognized Dr. Ribas's energy and talent and has promoted his career by placing him in leadership positions on major clinical studies and the Engineered Immunity Consorium. Existing funding means that progress of the central theme of this work is assured beyond 2010. There are no plans presented for specific recruitment. But, given other general aspects of support for Dr Ribas, ongoing support would be anticipated as there is a highly developed multi-centre consortium which supports Dr Ribas. There is clearly very strong local support for taking the gene therapy to the clinic. UCLA's track record is excellent. They have a clear commitment to promoting stem cell research, and have established new centers and core facilities around this topic. They have trained and continue to train many excellent scientists in this field, and have plans to recruit additional stem cell scientists to further strengthen and expand their program. DISCUSSION: The research proposal intends to translate mouse data into human and piggy-backs on an existing clinical trial. Overall, reviewers felt that this is a good bedside-to-bench model and appreciated the effort to make the most of patient samples from an existing trial. However, the reviewers also found weaknesses in the proposal that questioned the overall significance of the studies. Although the proposal centers on achieving a self-renewing population of tumor-directed memory T cells, not much analysis of self-renewal is proposed. No validation of proposed surrogate markers in the human model are presented. Additionally, the mentioned hESC experiments are vague and the overall impact of these studies on stem cell biology is unclear. Reviewers felt that the investigator is excellent and energetic with good mentors and institutional support. Given the large number of projects currently managed by the PI, it was unclear to the reviewers how much time and energy the PI will have for this project. PROGRAMMATIC DISCUSSION: A motion was made to move this application to Tier I – Recommended for Funding. Reviewers identified two main programmatic reasons for making this motion. First, this is one of the few clinical translational applications that were reviewed. In addition to its relvance in cancer research, it is among the closest to HIV in the portfolio. Second, the purpose of the RFA was to identify and support future leaders in the stem cell field and according to one reviewer this candidate is clearly the person who is driving this translational work forward. A question remained as to the importance of this work to stem cell biology. The motion to move this application to Tier I- Recommended for Funding carried.