Abstract P105: Targeting VSIG4, a novel macrophage checkpoint, repolarizes suppressive macrophages which induces an inflammatory response in primary cell in vitro assays and fresh human tumor cultures
Authors: Sazinsky Steve , Nguyen Ani , Zafari Mohammad , Phennicie Ryan , Wahle Joe , Komoroski Veronica , Rooney Kathryn , Mizzoni Craig , Klebanov Boris , Ritter Jessica , Manfra Denise , Feldman Igor , Novobrantseva Tatiana 
Published: December 2021

Abstract
VSIG4 (V-set immunoglobulin-domain-containing 4) is a B7 family related protein with known roles as a complement receptor involved in pathogen clearance, via interactions with C3 fragments, as well as a negative regulator of T cell activation by an undetermined mechanism. VSIG4 is expressed in tumor associated macrophages with exquisite specificity. In cancer, increased expression of VSIG4 has been associated with worse survival in multiple indications, including non-small cell lung cancer, multiple myeloma, ovarian cancer, stomach cancer and glioma, suggesting an important role in tumor immune evasion. Based upon computational analysis of transcript data across thousands of primary cancer and normal tissue samples, we hypothesized that VSIG4 has an important regulatory role in promoting M2-like immune suppressive macrophages in the tumor microenvironment, and that targeting VSIG4 via a monoclonal antibody could relieve VSIG4-mediated macrophage suppression by repolarizing tumor associated macrophages (TAMs) to an inflammatory phenotype capable of coordinating an anti-tumor immune response. Through a series of in vitro and ex vivo assays we demonstrate that anti-VSIG4 antibodies repolarize M2 macrophages and induce an immune response culminating in T cell activation. Anti-VSIG4 antibodies upregulate pro-inflammatory cytokines in M-CSF plus IL-10 driven monocyte-derived M2c macrophages, as well as in TAM-like macrophages in vitro derived from monocytes cultured in the presence of ascites fluid from ovarian cancer patients. To determine whether anti-VSIG4-induced macrophage repolarization can activate T cells, monocyte-derived M2c macrophages were co-cultured with autologous T cells in the presence of staphylococcal enterotoxin B (SEB) activation and anti-VSIG4 antibodies. Here, anti-VSIG4 antibodies upregulate both pro-inflammatory myeloid-derived cytokines (GM-CSF) and T cell-derived cytokines (IFNγ). To extend these observations to a relevant translational model, we treated fresh, patient-derived tumor samples with anti-VSIG4 antibodies and relevant controls ex vivo. Across numerous patient-derived samples, which included multiple tumor types, anti-VSIG4 treatment resulted in a significant upregulation of cytokines involved in TAM repolarization and T cell activation, and chemokines involved in immune cell recruitment, at levels greater than observed by treatment with anti-PD-1 or a clinical macrophage repolarizing agent (anti-ILT-4). Taken together, these data suggest that VSIG4 represents a promising new target capable of stimulating an anti-cancer response via multiple key immune mechanisms.
Citation Format: Steve Sazinsky, Ani Nguyen, Mohammad Zafari, Ryan Phennicie, Joe Wahle, Veronica Komoroski, Kathryn Rooney, Craig Mizzoni, Boris Klebanov, Jessica Ritter, Denise Manfra, Igor Feldman, Tatiana Novobrantseva. Targeting VSIG4, a novel macrophage checkpoint, repolarizes suppressive macrophages which induces an inflammatory response in primary cell in vitro assays and fresh human tumor cultures [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P105.