Abstract 3266: BND-22, a first-in-class, anti-ILT2 monoclonal antibody inhibits the immunosuppressive effects of HLA-G and enhances anti-tumor activity of immune cells in preclinical in vitro, ex vivo, and in vivo models
Authors: Mandel Ilana , Haves Dana , Goldshtein Ilana , Peretz Tsuri , Alishekevitz Dror , Sapir Yair , Hashmueli Sharon , Friedman Itay , Moshe Tehila Ben 
Published: September 2020

Abstract
Background: Ig-like transcripts (ILTs) are a family of immuno-modulating receptors expressed on immune cells. ILT2 is an inhibitory receptor expressed on both innate and adaptive immune cells. It has been shown to bind to MHC class I molecules and binds with the highest affinity to HLA-G, an immunosuppressive MHC molecule expressed by multiple tumor types. ILT2-mediated inhibition can lead to impairment of immune cell proliferation, differentiation, phagocytosis, cytotoxicity and cytokine secretion, identifying the ILT2 signaling axis as a potential novel target for anti-cancer immunotherapy. Here we describe preclinical characterization of BND-22, a humanized IgG4, ILT2 antagonist antibody developed for the treatment of solid tumors.
Methods: BND-22 binding to ILT2 was evaluated by flow cytometry, ELISA and surface plasmon resonance. We investigated the ability of BND-22 to reverse ILT2-mediated immune suppression of macrophages and lymphocytes. Macrophage and NK cell effector functions were studied in vitro and ex vivo in the presence of several cancer cell lines and patient tumor tissues using flow cytometry, time-lapse live-cell-microscopy, and functional cell-based assays. Xenograft subcutaneous melanoma and colorectal carcinoma and melanoma lung metastases models were used to evaluate the in vivo anti-tumor effect of BND-22.
Results: BND-22 binds ILT2, but not other ILT-family receptors, with low nanomolar affinity and blocks its interaction with HLA-G in a concentration-dependent manner. ILT2 blockade with BND-22 increased macrophage-mediated phagocytosis of tumor cell lines and patient-excised tumors, enhanced the cytotoxicity of NK cells against multiple types of cancer cells, and increased NK cell production of Granzyme B and IFNγ. ILT2 and PD-1 were found to be expressed by different sub-populations of CD45+ cells. Co-blockade of ILT2 and PD-1 showed a synergistic effect in increasing pro-inflammatory cytokine production by patient-derived PBMC in response to autologous tumor cells. In subcutaneous melanoma and colorectal carcinoma xenograft mouse models, BND-22 enhanced the anti-tumor activity of macrophages, inhibited tumor growth and prolonged survival. BND-22 also potently increased the anti-tumor activity of lymphocytes and inhibited metastases spread in an in vivo melanoma lung lesion model.
Conclusions: BND-22, a first-in-class, anti-ILT2 antagonist antibody induces a potent macrophage and lymphocyte-driven anti-tumor immune response in multiple in vitro, ex vivo and in vivo models. BND-22 offers a differentiated, multi immune cell-based mechanism of action. Safety, tolerability, and anti-tumor activity of BND-22 will be explored in a first-in-human clinical trial in cancer patients with tumor types known to express HLA-G.
Citation Format: Ilana Mandel, Dana Haves, Ilana Goldshtein, Tsuri Peretz, Dror Alishekevitz, Yair Sapir, Sharon Hashmueli, Itay Friedman, Tehila Ben Moshe. BND-22, a first-in-class, anti-ILT2 monoclonal antibody inhibits the immunosuppressive effects of HLA-G and enhances anti-tumor activity of immune cells in preclinical in vitro, ex vivo, and in vivo models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3266.