Late-Stage Tumor Regression after PD-L1 Blockade Plus a Concurrent OX40 Agonist

Abstract

The protective capability of tumor antigen–specific T cells is regulated by costimulatory and inhibitory signals. Current approaches in cancer immunotherapy seek to restore the function of unresponsive T cells by blocking inhibitory pathways. In contrast, providing exogenous costimulatory signals to T cells also enhances antitumor functionality. By combining these two clinical approaches, we demonstrate the synergy of targeting PD-L1 together with the costimulatory molecule OX40, to enhance antitumor immunity. Concurrently blocking PD-L1 and providing a costimulatory agonist to OX40 increased the presence and functionality of tumor antigen–specific CD8+ T cells with simultaneous enhancement of T-helper type 1 (Th1)-skewed CD4+ T cells. This shift was functionally supported by increased glucose metabolism of antigen-specific CD8+ T cells and the acquisition of granzyme B by regulatory T cells. Together, this mechanism promoted tumor regression of late-stage tumors beyond that achieved by either blockade as monotherapy. These findings indicate that targeting both T-cell intrinsic (OX40) and extrinsic (PD-L1) regulatory molecules increases the bioenergetic potential of T cells, thereby expanding functional and tumor antigen–specific T cells.

PD-1 Specific ‘Blocking’ Antibodies That Deplete PD-1+ T Cells Present An Inconvenient Variable In Pre-clinical Immunotherapy Experiments

“…Therefore, using a tetramer for mAlg8, a known tumor rejection antigen (Gubin et al, 2014), we analyzed tumor-antigen specific T cells from d42m1-T3 MCA sarcoma tumor-bearing animals and evaluated the expression of PD-1 (Fig 2A) and PD-L1 ( Fig 2B) on T cells in the tumor and spleen. As previously reported (Polesso et al, 2019), tumor-antigen specific T cells in the tumor expressed very high levels of PD-1 compared to their counterpart in the spleen, and this increase was much greater than the expression of PD-L1 on these same cells.…”

“…In the MCA-205 mouse sarcoma model, we previously published that anti-PD-L1 synergizes with OX40 agonism to enhance anti-tumor T cell responses and cause tumor regression (Polesso et al, 2019). While performing these experiments, we compared anti-PD-1 to anti-PD-L1 immunotherapy ( Fig 1A) and noted a striking difference.…”

“…Using an independent mouse model, in which tumor-specific T cells are identified by high expression of the TCRinduced Nur77GFP signal (Moran et al, 2011;Moran et al, 2016;Polesso et al, 2019) and co-express high PD-1 in the tumor but not the spleen ( Fig 2K), we observed an overall decrease in the frequency of CD8+Nur77GFP hi T cells in the tumor after anti-PD-1 ( Fig 2L). This reduction occurred in the tumor, but not the spleen ( Fig 2M), and there was no reduction when using anti-PD-L1.…”

“…While conducting immunotherapy experiments in mice, we observed profound differences between anti-PD-1 and anti-PD-L1. While anti-PD-L1 synergized with OX40 agonism (Polesso et al, 2019), anti-PD-1 attenuated OX40 immunotherapy (Shrimali et al, 2017). We show here that anti-PD-1 clone G4 (Armenian hamster IgG), when compared to anti-PD-1 clone RMP1-14 (rat IgG2a), or anti-PD-L1 clone 10F.9G2 (rat IgG2b), resulted in a loss of antigen-specific CD8 T cells in two sarcoma tumor models and the murine cytomegalovirus (MCMV) infection model.…”

Immune checkpoint modulation enhances HIV-1 antibody induction

“…Tumor necrosis factor receptor superfamily member 4 (OX40) receptor is a stimulatory molecule on activated T cells and can result in enhanced activity and clonal expansion 26 . Administration of blocking (CTLA4, PD-1) or agonist (OX40) antibodies against these checkpoint regulators improves antitumor immune responses in animal models, and CTLA-4 and PD-1 antibodies have become approved immunotherapies for multiple tumor types in humans [19][20][21][22][27][28][29] .…”