Abstract 4129: Novel small molecule TLR7/8 agonists for enhancing NK cell-mediated ADCC

Abstract

Abstract Antibody-dependent cell-mediated cytotoxicity (ADCC) is a key mechanism of action for some therapeutic antibodies. ADCC involves killing of an antibody-coated target cell by an effector cell through the release of cytotoxic or cell death-inducing molecules. ADCC is triggered through interaction of Fcγ receptors present on the effector cell surface with the Fc region of the target-bound antibody. Natural killer (NK) cells are one of the primary effector cells that mediate ADCC. There is significant interest in designing therapeutic agents that can enhance ADCC because this can result in improved clinical responses with approved antibodies. We have developed a suite of highly substituted imidazoquinolines, which activate TLR 7 and/or 8 and induce significantly higher levels of cytokines compared to the FDA-approved TLR7 agonist imiquimod. In the current study, we evaluated our series of TLR7-specific, 8-specific and 7/8 dual selective agonists for their ability to improve ADCC with Cetuximab. We investigated NK cell activation in the presence of these compounds, as well as NK cell mediated ADCC against an EGFR expressing lung cancer cell line, A549. In addition, we also measured cytokine induction in human peripheral blood mononuclear cells in response to these compounds. Our studies show dual TLR 7/8 and 8-specific agonists induce robust pro-inflammatory cytokine secretion and activate NK cells. however, mixed agonists also induce greater immunosuppressive cytokines compared to TLR8-specific agonists. Further, these agonists also significantly enhanced Cetuximab mediated ADCC in vitro. In vivo studies examining the anticancer efficacy of the combination of selected TLR7/8 agonists and Cetuximab are ongoing. Citation Format: Vidhi Khanna, Hyunjoon Kim, Wenqui Zhang, Peter Larson, David Ferguson, Jayanth Panyam. Novel small molecule TLR7/8 agonists for enhancing NK cell-mediated ADCC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4129.