Engineered CAR-T cells for treatment of solid cancers

The chimeric antigen receptor T (CAR-T) cell therapy has become a promising cancer immunotherapeutic method, particularly in treating B cell malignancies; however, this therapy is still in the early stages of development for the treatment of solid tumors. One limiting factor of CAR-T cell therapy is the suppressive tumor microenvironment, which inactivates the function of tumor infiltrating lymphocyte (TIL). This thesis work is divided into two major studies that aim to overcome two different immunosuppressive mechanisms in the TME: adenosine up-regulation and PD-1/PD-L1 immune inhibition. In the first study, we surface-engineered CAR-T cells to deliver an A2a receptor small molecule inhibitor in the TME. The small molecule inhibitor is encapsulated in cross- linked multilamellar liposomes, which are covalently conjugated to the surface of CAR-T cells. We hypothesized that this co-delivery strategy would be able to enhance CAR-T cell functions in the TME and, consequently, augment CAR-T cell antitumor activities. We demonstrated in this study that our drug delivery strategy was able to prevent CAR-T cells from becoming hypofunctional in the TME and improved CAR-T cell antitumor response. Moreover, we showed that the antitumor function of tumor infiltrated CAR-T cells could be rescued upon interference of the adenosine pathway using A2a receptor small molecule inhibitors. This study signifies the effects adenosine has on tumor infiltrating immune cells and demonstrated a strategy in which it could be overcome, in order to improve the efficacy of CAR-T cell therapy. The second obstacle we aim to overcome is the PD-1/PD-L1 immune regulatory pathway. In the second study, we engineered CAR-T cells to secrete the PD-1/PD-L1 checkpoint inhibitor and evaluated the antitumor efficacy in vivo. This strategy was proved to significantly enhance CAR-T cell effector functions in vivo and was able to completely eradicate established tumors. We evaluated the effector functions in an ex vivo assay and demonstrated that the intrinsically secreted PD-1/PD-L1 checkpoint inhibitor was able to prevent CAR-T cell exhaustion and maintained IFNγ secretion upon restimulation.