Metabolic reprogramming to improve EGFRvIII CAR T cell persistence

ABSTRACT
Adoptive immunotherapy using chimeric antigen receptor (CAR) T cells has been successful against some liquid
tumors, but has failed to cure solid tumors. A key reason for CAR T cell failure against solid tumors is antigen
heterogeneity. However, pre-clinical studies of CAR T cells against solid tumors in animal models show some
promise; in a brain tumor mouse model of glioblastoma, CAR T cells recognizing the EGFRvIII tumor-specific
antigen are successful in eliminating tumor, but only against homogeneous tumor and only when mice first
receive lymphodepletive host conditioning (via total body irradiation) prior to CAR T cell infusion. Although
lymphodepletive host conditioning provides immunological space for CAR T cell expansion, it is problematic in
the context of heterogeneous solid tumors, as it impairs endogenous host immunity which is critical for targeting
alternative antigens found within the solid tumor. For that reason, successful CAR T cell treatment against solid
heterogeneous tumors will require innovative methods to improve CAR T cell persistence to eliminate the need
for host lymphodepletive conditioning, and allow for preservation of host endogenous immunity. To achieve this,
we propose to utilize metabolic reprogramming of EGFRvIII CAR T cells. Many studies over the last decade
have now clearly demonstrated a link between T cell differentiation, function, and metabolism. A predominantly
oxidative metabolism supports T cell surveillance, survival, and memory, whereas a predominantly glycolytic
metabolism supports biosynthesis to promote effector T cell proliferation and function, but is associated with
decreased longevity. The objectives of this R21 proposal are to (1) utilize metabolic reprogramming of EGFRvIII
CAR T cells to improve CAR T cell persistence in vitro and in vivo, and (2) test the ability of modified EGFRvIII
CAR T cells delivered in the absence of lymphodepletive host conditioning to preserve the endogenous immune
system and improve heterogeneous tumor killing. We hypothesize that methods that increase oxidative
metabolism will improve CAR T cell persistence, eliminating the need for lymphodepletive host conditioning,
maintaining host endogenous immunity, and ultimately improving heterogeneous tumor killing. To test our
hypothesis, we will perform the following specific aims: 1) Identify genetic and pharmacological strategies to
modify EGFRvIII CAR T cells for enhanced metabolic fitness to support persistence; and 2) Test if metabolically
fit murine EGFRvIII CAR T cells delivered in the absence of lymphodepletive host conditioning preserve
endogenous immunity. If successful, these approaches can be partnered in future studies with strategies to
enhance endogenous host immunity against heterogeneous tumors and overcome a hostile immunosuppressive
tumor environment. This work, while performed in a brain tumor model, would be relevant for CAR T cell therapy
against multiple solid tumors.