Abstract 1364: Characterization of CHS-1000, an Fc-modified anti-ILT4 monoclonal antibody for reprogramming suppressive myeloid cells in solid tumors

Abstract

Abstract Tumor resident immunosuppressive myeloid cells play a significant role in inducing resistance to cancer immunotherapy and are associated with poor prognosis in several solid tumors. The leukocyte immunoglobulin-like receptor B2 (LILRB2), also known as ILT4, is primarily expressed on myeloid cells and is a negative regulator of myeloid cell activation. ILT4 and its primary ligands (HLA-G, HLA-A) are widely expressed in various solid tumors and are associated with disease progression, tumor metastasis and poor clinical outcome. Abrogating inhibitory signals mediated through ILT4 and its ligands is a promising strategy to reprogram suppressive myeloid cells and enhance efficacy of immune checkpoint therapies. Here we report IND-enabling preclinical characterization of CHS-1000, a novel recombinant humanized Fc-modified IgG1 antibody with attenuated Fc-gamma receptor (FcγR) binding, that specifically targets immunoglobulin-like transcript 4 (ILT4). CHS-1000 selectively binds to human ILT4 with high affinity and potently blocks ILT4 interactions with its primary ligands (HLA-A, HLA-G). Functionally, CHS-1000 promotes re-polarization of suppressive myeloid cells to a pro-inflammatory phenotype and enhances activation of dendritic cells and T cells. Combinations of CHS-1000 with PD-1 inhibitors or other immunotherapy agents hold particular promise for enhanced anti-tumor activity. These preclinical characterization data support clinical development of CHS-1000 in combination with toripalimab (a commercial stage anti-PD-1 antibody) as an immunotherapy treatment for patients with solid tumors. Citation Format: Narendiran Rajasekaran, Xiaoguang Wang, Scott Klakamp, Sruthi Ravindranathan, Suzanna Tatarewicz, Julia Du, Brian Nguyen, Kate Widmann, Nessa Hawkins, Daniel J. Chin, Theresa LaVallee, Varun Kapoor. Characterization of CHS-1000, an Fc-modified anti-ILT4 monoclonal antibody for reprogramming suppressive myeloid cells in solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1364.