Combining SiRPα decoy–coengineered T cells and antibodies augments macrophage-mediated phagocytosis of tumor cells

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Abstract

The adoptive transfer of T cell receptor–engineered (TCR-engineered) T cells (ACT) targeting the HLA-A2–restricted cancer-testis epitope NY-ESO-1157–165 (A2/NY) has yielded favorable clinical responses against several cancers. Two approaches to improve ACT are TCR affinity optimization and T cell coengineering to express immunomodulatory molecules that can exploit endogenous immunity. By computational design we previously developed a panel of binding-enhanced A2/NY-TCRs including A97L, which augmented the in vitro function of gene-modified T cells as compared with WT. Here, we demonstrated higher persistence and improved tumor control by A97L–T cells. In order to harness macrophages in tumors, we further coengineered A97L–T cells to secrete a high-affinity signal regulatory protein α (SiRPα) decoy (CV1) that blocks CD47. While CV1-Fc–coengineered A97L–T cells mediated significantly better control of tumor outgrowth and survival in Winn assays, in subcutaneous xenograft models the T cells, coated by CV1-Fc, were depleted. Importantly, there was no phagocytosis of CV1 monomer–coengineered T cells by human macrophages. Moreover, avelumab and cetuximab enhanced macrophage-mediated phagocytosis of tumor cells in vitro in the presence of CV1 and improved tumor control upon coadministration with A97L–T cells. Taken together, our study indicates important clinical promise for harnessing macrophages by combining CV1-coengineered TCR–T cells with targeted antibodies to direct phagocytosis against tumor cells.

Authors

Evangelos Stefanidis, Aikaterini Semilietof, Julien Pujol, Bili Seijo, Kirsten Scholten, Vincent Zoete, Olivier Michielin, Raphael Sandaltzopoulos, George Coukos, Melita Irving