Abstract 721: Novel and distinctive anti-HLA-G antibody, IMB-201, inhibits tumor progression by breaking immune escape mechanism and enhancing cytotoxicity

Abstract Human leukocyte antigen-G (HLA-G), a type of MHC class I, is known to be expressed only in the placenta and acts as an immune suppressor to protect the fetus from maternal immunity. Recent studies have revealed that HLA-G suppresses various tumor-infiltrated immune cells, such as T cells, NK cells, and macrophages, through interaction with inhibitory receptors Ig-like transcript 2 (ILT2). HLA-G has recently emerged as an attractive anticancer target because HLA-G is a highly specific tumor antigen and has a role in immune evasion of cancer cells. Additionally, the expression pattern of ILT2 differs from that of PD-1 in tumor-infiltrated CD8+ T cells. Therefore, an HLA-G targeting strategy is expected to be an alternative to address unmet medical needs for those not responding to anti-PD (L) 1 therapies. In this study, we screened the novel anti-HLA-G antibody, IMB-201, using phage display technique and confirmed that IMB-201 selectively bound to the membrane HLA-G of cancer cells. It exhibited superior activities in ILT2 blockade, NK cell activation, and antibody-dependent cellular cytotoxicity (ADCC) compared to the reference antibody. Furthermore, IMB-201 demonstrated more efficient suppression of tumor growth compared to the reference antibody in subcutaneous gastric cancer xenograft model. Notably, the group administered IMB-201 with NK92MI cells (CD16-negative NK cells) in the ovarian cancer xenograft model showed stronger tumor growth inhibition compared to the group treated only IMB-201, indicating that NK92MI cells were activated by IMB-201. This result indicates that one of the mechanisms of action (MoA) of IMB-201 worked effectively in vivo. In addition, to maximize the efficacy of IMB-201 and differentiate it from competitors, various efficacy enhancing modality could be applicable. We aim to develop biopharmaceuticals by selecting the optimized modality. Based on these results, IMB-201 could overcome the limitations of existing cancer immunotherapy, potentially becoming highly influential in cancer treatment as a novel immune checkpoint inhibitor. It is also expected to exhibit higher anticancer efficacy in combination therapy with immune checkpoint inhibitors. Citation Format: Hyeonju Kang, Seungil Baek, Inyoung Lee, Manseok Ju, Seonggu Han, Eunjung Han, Sungmuk Kang, Jihye Koo, Yoojin Kim, Suho Park, Eunyoung Cho, Chungmin Lee, Gyongsik Ha. Novel and distinctive anti-HLA-G antibody, IMB-201, inhibits tumor progression by breaking immune escape mechanism and enhancing cytotoxicity 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 (6Suppl): Abstract nr 721.