Abstract 3300: Glycoimmune checkpoint and tumor stroma-targeted oncolytic vaccinia virus for the treatment of solid tumors

Abstract

Oncolytic virotherapy represents a promising therapeutic strategy for cancers that do not respond well to immune checkpoint inhibitors. Oncolytic viruses (OV) preferentially replicate in and lyse tumor cells, leading to systemic immune stimulation. Studies have shown that hypersialylation promotes tumor growth and metastasis, as well as the suppression of immune cells. Cancer-associated fibroblasts (CAFs) are known to facilitate tumor invasion and angiogenesis and maintain immunosuppressive microenvironment in solid tumors. We are developing vvDD-Sial-FAP/CD3, an oncolytic vaccinia virus expressing a membrane-bound sialidase, to remove sialic acids from the cell surface glycans, and fibroblast activation protein (FAP)-targeted T cell engager, to eliminate glycoimmune checkpoint and tumor stroma, respectively. vvDD-Sial-FAP/CD3 is an engineered vaccinia virus of Western Reserve (WR) strain with: (1) an insertional disruption of the viral thymidine kinase (TK) gene with the sialidase and FAP/CD3 transgenes. TK is an essential enzyme for the pyrimidine synthesis pathway; viral TK gene deletion thus results in selective replication of virus in rapidly dividing cancerous cells with high intracellular nucleotide pools, and (2) a deletion of the vaccinia growth factor (VGF) genes for greater dependence on the cell cycling status of the cancer cells. Our results showed that sialidase expressed from vvDD-Sial-FAP/CD3 efficiently cleaves the sialic acids from the cell surface and the Fc fused to the sialidase induced antibody-dependent cell-mediated cytotoxicity (ADCC) using an ADCC reporter assay. In vitro efficacy studies were conducted using HCT-116 human colon cancer cells mixed with FAP-expressing normal human dermal fibroblasts or FAP-positive HCC1143 human breast cancer cells in the presence of human peripheral blood mononuclear cells. In both tumor models, vvDD-Sial-FAP/CD3 induced activation of both CD4+ and CD8+ T cells, as measured by the upregulation of CD69 and CD25 markers and increased granzyme B release, which resulted in enhanced cell killing. Using A549 co-cultured with CAFs microtissues, we showed that vvDD-Sial-FAP/CD3 spread efficiently within the tumor spheroids. In addition, vvDD-Sial-FAP/CD3 increased tumor-infiltrated lymphocytes, leading to enhanced cell killing. Taken together, our results have demonstrated potent anti-tumor and -stroma effects induced by vvDD-Sial-FAP/CD3 in multiple cancer models. In vivo efficacy of vvDD-Sial-FAP/CD3, either alone or in combination with checkpoint inhibitor or NK cell therapy, is being evaluated. Citation Format: Winnie M. Chan, Mariya Viskovska, Micaela McArthur, Xue Mary Yu, Wei Liang, Zane Norman, Xiaotong Song, Nancy T. Chang, Haiyan Jiang. Glycoimmune checkpoint and tumor stroma-targeted oncolytic vaccinia virus for the treatment of solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3300.