Final Report Summary - ANTIVESSEL-T-CELLS (Development of Vascular-Disrupting Lymphocyte Therapy for Tumours)
-Stand alone description of the project and its outcomes
The main objective of this research proposal, Development of Vasculature-Disrupting Lymphocyte Therapy for Tumors, is to develop novel lymphocyte gene-engineering and combinatorial treatment approaches, that synergise with endogenous immunity and the susceptibility of tumors to blood vessel attack, to eliminate solid tumors. For that purpose, we began by developing and optimising the design of a range of tumor vasculature targeting chimeric antigen receptors (CARs) including against PSMA, VEGFR2, TEM1, and others. We further built these constructs for the engineering of both human and murine T cells. Indeed, while CAR therapy has proven highly efficacious against several advanced hematologic malignancies, solid tumors have proven poorly responsive. There are several reasons for this. First, there are important issues of on-target/off-site toxicity because most so-called solid ‘tumor antigens (TAs)’ are also found, albeit at low levels, on healthy tissues. In addition, the T cells must efficiently home to the tumor and then migrate into the tumor bed from the blood vessels, wherein a wide range of highly suppressive mechanisms can be upregulated that attenuate T cell effector function. All of these issues must be taken into careful consideration in the design of curative therapies against solid tumors. To date, most pre-clinical CAR studies have been performed against xenografts in immunocompromised mice. Thus, many of the players involved in effector T-cell suppression, such as T regulatory cells and myeloid derived suppressor cells, are not evaluated. Relatively few studies have been performed in immunocompetent syngeneic model systems, and we believe that this is in large part due to technical difficulties in efficiently transducing and expanding murine T cells. We spent considerable time and effort in developing a fully optimised methodology for retroviral engineering murine T cells to express CARs and other genes of interest. We further optimised constructs, and co-transduction strategies to develop next-generation murine CAR T cells that co-express immunomodulatory molecules such as cytokines, as well as a split CAR design (two TAs must be co-engaged for full T-cell activation) for the first time in murine T cells to improve safety. In syngeneic tumor models, we have observed that the endogenous immune system can play a critical role in both the suppression and the promotion of tumor control. Moreover, we have developed robust combinations of T cell therapy plus molecules that stimulate protective immune pathways, and/or block checkpoints, for improved control. Finally, classic therapy approaches including radiotherapy, chemotherapy, check-point blockade antibodies, and anti-VEGFA therapy (that can impacts the tumor vasculature and other factors in the tumor microenvironment), have been used in conjunction with engineered T cells for improved tumor control. In parallel to the mouse T cell work, we have also optimised vector design and lentiviral transduction protocols for primary human T cells. Finally, to improve the safety of CAR therapy, we have recently developed with our collaborators a novel heterodimeric, switchable CAR for which the administration of a small molecule can disrupt the complex and stop effector function. We believe that this novel CAR holds important promise for clinical translation, both in terms of improved patient safety and in terms of function as it is more powerful than classic second generation CARs.
The main objective of this research proposal, Development of Vasculature-Disrupting Lymphocyte Therapy for Tumors, is to develop novel lymphocyte gene-engineering and combinatorial treatment approaches, that synergise with endogenous immunity and the susceptibility of tumors to blood vessel attack, to eliminate solid tumors. For that purpose, we began by developing and optimising the design of a range of tumor vasculature targeting chimeric antigen receptors (CARs) including against PSMA, VEGFR2, TEM1, and others. We further built these constructs for the engineering of both human and murine T cells. Indeed, while CAR therapy has proven highly efficacious against several advanced hematologic malignancies, solid tumors have proven poorly responsive. There are several reasons for this. First, there are important issues of on-target/off-site toxicity because most so-called solid ‘tumor antigens (TAs)’ are also found, albeit at low levels, on healthy tissues. In addition, the T cells must efficiently home to the tumor and then migrate into the tumor bed from the blood vessels, wherein a wide range of highly suppressive mechanisms can be upregulated that attenuate T cell effector function. All of these issues must be taken into careful consideration in the design of curative therapies against solid tumors. To date, most pre-clinical CAR studies have been performed against xenografts in immunocompromised mice. Thus, many of the players involved in effector T-cell suppression, such as T regulatory cells and myeloid derived suppressor cells, are not evaluated. Relatively few studies have been performed in immunocompetent syngeneic model systems, and we believe that this is in large part due to technical difficulties in efficiently transducing and expanding murine T cells. We spent considerable time and effort in developing a fully optimised methodology for retroviral engineering murine T cells to express CARs and other genes of interest. We further optimised constructs, and co-transduction strategies to develop next-generation murine CAR T cells that co-express immunomodulatory molecules such as cytokines, as well as a split CAR design (two TAs must be co-engaged for full T-cell activation) for the first time in murine T cells to improve safety. In syngeneic tumor models, we have observed that the endogenous immune system can play a critical role in both the suppression and the promotion of tumor control. Moreover, we have developed robust combinations of T cell therapy plus molecules that stimulate protective immune pathways, and/or block checkpoints, for improved control. Finally, classic therapy approaches including radiotherapy, chemotherapy, check-point blockade antibodies, and anti-VEGFA therapy (that can impacts the tumor vasculature and other factors in the tumor microenvironment), have been used in conjunction with engineered T cells for improved tumor control. In parallel to the mouse T cell work, we have also optimised vector design and lentiviral transduction protocols for primary human T cells. Finally, to improve the safety of CAR therapy, we have recently developed with our collaborators a novel heterodimeric, switchable CAR for which the administration of a small molecule can disrupt the complex and stop effector function. We believe that this novel CAR holds important promise for clinical translation, both in terms of improved patient safety and in terms of function as it is more powerful than classic second generation CARs.