Locoregionally delivered PD-1 blockade augments B7-H3 targeting CAR T cell efficacy in models of glioblastoma

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Abstract

Glioblastoma (GBM) is a lethal brain tumor with a 95% five-year mortality rate, and remains a major unmet clinical need. An innovative approach to target GBM is administration of chimeric antigen receptor (CAR) T cells. In this study we identified B7-H3 as a favorable target antigen for CAR T cell therapy of GBM and developed a B7-H3 targeting CAR T cell. This CAR demonstrates robust, antigen-specific cytolysis and cytokine production, low tonic signaling, and preservation of a stem/naïve cell phenotype. Using orthotopic xenograft models of GBM we show that a single intravenous administration of this B7-H3 targeted CAR confers tumor control, and long-term survival. We identified upregulation of T cell inhibitory ligands PD-L1 and PD-L2 as a mechanism of resistance, and modified our B7-H3 targeting CAR vector to include a secreted a PD-1 blocking scFv. We further demonstrate that concomitant PD-1 blockade by the secreted PD-1 blocking scFv augments the antitumor capabilities of B7-H3-targeting CAR T cells through increased intratumoral infiltration by the CAR T cells and improved effector function. These data demonstrate B7-H3 targeting CAR T cells with concomitant PD-1 blockade is a safe and efficient method for improving the antitumor capacity of CAR T cells for GBM.

Authors

Jonathan F. Khan, Parwiz Abrahimi, Winson Cai, Lauren Dong, Kenny Kwok-Hei Yu, Svena Verma, Yacine Marouf, Sadna Budhu, Tara Pal Chaudhuri, Valeria Estrada Navarro, Mamadou A. Bah, Kelsey Hopland, Yanhong Yang, Terence J. Purdon, Ileana C. Miranda, Viviane Tabar, Jedd D. Wolchok, Taha Merghoub, Renier J. Brentjens