Abstract 601: IO-108, A fully human therapeutic antibody blocking the myeloid checkpoint LILRB2/ILT4, promotes innate and adaptive anti-cancer immunity in preclinical studies
Authors: Ma Jing-Tyan , Liu Xiaoye , Stafford Ryan , McCutcheon Krista , Chen Heyu , Huang Tao , Tian Hongyu , Hong Kyu , Zhang ChengCheng , Chung Luke , Song An , Woodard Paul , Liao XCharlene , Costa MariaJose 
Published: June 2022

Abstract
Tumor-associated myeloid cells inhibit anti-cancer immune responses systemically and in the tumor microenvironment (TME), thereby limiting the efficacy of T cell checkpoint inhibitors. However, the plasticity of myeloid cells may enable therapeutic intervention. The immune inhibitory receptor LILRB2 (also known as ILT4) is expressed primarily by myeloid cells (monocytes, macrophages, dendritic cells and neutrophils), and has emerged as a key myeloid checkpoint contributing to the tolerogenic activity of myeloid cells associated with cancer. LILRB2 has several ligands (classical and non-classical MHC-I, ANGPTL2/5, SEMA4A and CD1) and most of these are known to contribute to immune suppression in the TME. Using computational biology approaches, we found that high LILRB2 expression is associated with macrophage infiltration in many solid tumor types from TCGA. Therefore, LILRB2 is a compelling target to overcome immune suppressive activity of cancer-associated myeloid cells. IO-108 is a fully human IgG4 therapeutic antibody that binds to LILRB2 with high affinity and specificity. IO-108 binds to all myeloid cells in the solid TME and periphery. In vitro studies support that blockade of LILRB2 interaction with its various ligands is the anticipated mechanism of action of IO-108. The LILRB2 antagonist activity of IO-108 produces the desired pro-inflammatory (re)polarization of myeloid cells. IO-108 treatment results in increased pro-inflammatory responses and an enhanced antigen-presenting cell (APC) phenotype to multiple stimuli (e.g., T cell activators, STING and TLR agonists) in ex vivo assays. In addition, IO-108 precludes the anti-inflammatory myeloid cell phenotype resulting from “tumor conditioning” and promotes the differentiation of monocytes and immature dendritic cells (DC) into pro-inflammatory DC. IO-108 enhances the effect of PD-1 blocking antibodies in allogeneic mixed leukocyte reactions of CD4+ T cells and macrophages. Moreover, IO-108 polarized primary myeloid cells isolated from solid tumor patient blood and ovarian cancer-associated ascites towards a proinflammatory phenotype and attenuated their suppressive effect on autologous T cell proliferation and production of proinflammatory cytokines. In vivo, IO-108 inhibits tumor growth in mouse models, which is associated with immune cell activation. Importantly, IO-108 presents a favorable pharmacokinetic and safety profile in preclinical models. Collectively, the preclinical characterization of IO-108 enabled a comprehensive clinical biomarker plan and lends rationale to the clinical study (NCT05054348) of IO-108 as a novel immunotherapy for multiple solid tumor types, including those relapsed/refractory to standard of care therapies.
Citation Format: Jing-Tyan Ma, Xiaoye Liu, Ryan Stafford, Krista McCutcheon, Heyu Chen, Tao Huang, Hongyu Tian, Kyu Hong, ChengCheng Zhang, Luke Chung, An Song, Paul Woodard, XCharlene Liao, MariaJose Costa. IO-108, A fully human therapeutic antibody blocking the myeloid checkpoint LILRB2/ILT4, promotes innate and adaptive anti-cancer immunity in preclinical studies [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 601.