Enhanced Cancer Immunotherapy by Chimeric Antigen Receptor–Modified T Cells Engineered to Secrete Checkpoint Inhibitors

Abstract

Despite favorable responses of chimeric antigen receptor (CAR)-engineered T-cell therapy in patients with hematologic malignancies, the outcome has been far from satisfactory in the treatment of solid tumors, partially owing to the development of an immunosuppressive tumor microenvironment. To overcome this limitation, we engineered CAR T cells secreting checkpoint inhibitors (CPI) targeting PD-1 (CAR.αPD1-T) and evaluated their efficacy in a human lung carcinoma xenograft mouse model. To evaluate the effector function and expansion capacity of CAR.αPD1-T cells , we measured the production of IFNγ and T-cell proliferation following antigen-specific stimulation. Furthermore, the antitumor efficacy of CAR.αPD1-T cells, CAR T cells, and CAR T cells combined with anti-PD-1 antibody was determined using a xenograft mouse model. Finally, the underlying mechanism was investigated by analyzing the expansion and functional capacity of TILs. Human anti-PD-1 CPIs secreted by CAR.αPD1-T cells efficiently bound to PD-1 and reversed the inhibitory effect of PD-1/PD-L1 interaction on T-cell function. PD-1 blockade by continuously secreted anti-PD-1 attenuated the inhibitory T-cell signaling and enhanced T-cell expansion and effector function both and In the xenograft mouse model, we demonstrated that the secretion of anti-PD-1 enhanced the antitumor activity of CAR T cells and prolonged overall survival. With constitutive anti-PD-1 secretion, CAR.αPD1-T cells are more functional and expandable, and more efficient at tumor eradication than parental CAR T cells. Collectively, our study presents an important and novel strategy that enables CAR T cells to achieve better antitumor immunity, especially in the treatment of solid tumors. .

T-cells “à la CAR-T(e)” – Genetically engineering T-cell response against cancer

“…To remedy to this, Caruana et al engineered T cells to secrete heparanase enabling the efficient degradation of ECM and targeting of neuroblastoma tumors in mouse [258]. Furthermore, it is feasible to engineer T cells to secrete checkpoint blockers [259][260][261] (Fig. 1) or HVEM [262] to lower the immunosuppressive pressure in the tumor vicinity.…”

Programming CAR-T cells to kill cancer

“…In another example of this strategy, transgenic expression of cytokines tethered to their receptors can deliver stimulatory signals to the T cell while diminishing the risk of systemic toxicities associated with the administration of soluble cytokines 134 . Secreted antibodies Anti-PD-L1, anti-PD-1 Locally delivered checkpoint blockade 253,254 Custom response modules SynNotch Programmable response in response to antigen engagement 185 T-cell backpacks Nanoparticles loaded with TGF-β inhibitor and IL-15…”

Adoptive immunotherapy with CAR modified T cells in cancer current landscape and future perspectives

“…Some groups are also exploring the possibility of combing CAR T cells with oncolytic viruses (124) or with checkpoint inhibitors (125)(126)(127). Indeed, targeting the PD-1/PD-L1 axis is of particular interest for CAR-T cells development in solid tumors (128), and investigators are testing constructs which are able to deliver anti-PD-1 molecules (129,130) and strategies of cell-intrinsic PD-1 inhibition and inactivation (126,131,132), with the aim of improving the efficacy of CAR T cells also reducing the systemic side effects of checkpoint inhibitors.…”