The IAP antagonist birinapant enhances chimeric antigen receptor T cell therapy for glioblastoma by overcoming antigen heterogeneity

Abstract

Antigen heterogeneity that results in tumor antigenic escape is one of the major obstacles to successful chimeric antigen receptor (CAR) Tcell therapies in solid tumors including glioblastoma multiforme (GBM). To address this issue and improve the efficacy of CAR Tcell therapy for GBM, we developed an approach that combines CAR Tcells with inhibitor of apoptosis protein (IAP) antagonists, a new class of small molecules that mediate the degradation of IAPs, to treat GBM. Here, we demonstrated that the IAP antagonist birinapant could sensitize GBM cell lines and patient-derived primary GBM organoids to apoptosis induced by CAR Tcell-derived cytokines, such as tumor necrosis factor. Therefore, birinapant could enhance CAR Tcell-mediated bystander death of antigen-negative GBM cells, thus preventing tumor antigenic escape in antigen-heterogeneous tumor models invitro and invivo. In addition, birinapant could promote the activation of NF-κB signaling pathways in antigen-stimulated CAR Tcells, and with a birinapant-resistant tumor model we showed that birinapant had no deleterious effect on CAR Tcell functions invitro and invivo. Overall, we demonstrated the potential of combining the IAP antagonist birinapant with CAR Tcells as a novel and feasible approach to overcoming tumor antigen heterogeneity and enhancing CAR Tcell therapy forGBM.