(19c) Adoptive Transfer of CAR-Engineered T Cells with Surface-Conjugated Synthetic Nanoparticles Containing Small Molecule Inhibitors for Reversing Intratumoral T Cell Hypofunction

Adoptive T cell transfers of genetically modified cytotoxic T cells to express chimeric antigen receptors (CAR) have become a promising immunotherapy method. CARs specifically target tumor-associated antigens or cancer stromal antigens with high binding affinity. Activation of a CAR engineered T cell is independent of the major histocompatibility complex (MHC) and is achieved primarily through the single chain variable fragment (scFv) that is fused with intracellular signaling domains. Multiple researchers have shown that adoptive transfer of CAR T cells is successful in patients with B cell haematological malignancies, but is still in the earlier stages of development for treatment of solid tumors. One limiting factor to adoptive T cell therapy is the suppressive tumor microenvironment that inactivates tumor infiltrated T cell (TIL) function. Moon et al. (2014) showed that hypofunctional TILs express high levels of inhibitors of the intracellular pathways, such as the up-regulation of DGKa and DGKz that phosphorylates diacylglycerol. In addition to intracellular inhibitors, the tumor microenvironment also contains high concentration of TIL suppressor molecules such as adenosine that is up taken by the A2AR receptor expressed on the cell surface of CD4 and CD8 T cells. Adenosine is generated from extracellular ATP through CD39 and CD73 expressed on the surface of tumor cells and regulatory T cells. We hypothesized that in vivo delivery of pharmaceutical drugs, namely DGK and A2AR inhibitors, with crosslinked multilayer liposome vesicles (cMLV) would reverse TIL hypofunction. For delivery, cMLVs containing drugs were conjugated with adoptively transferred CAR T cells to target hypofunctional TILs residing in the tumor. We demonstrated that conjugation of cMLVs to CAR T cells does not alter key functions, such as T cell cytokine secretion and cytotoxicity. Furthermore, our in vivo study showed that combination therapy of small molecule inhibitors with CAR T cells were able to reverse TIL hypofunction and increase tumor infiltrating CD3+ T cells.