Abstract 3025: Preclinical characterization of a novel monoclonal antibody targeting a neo-antigen expressed in ovarian and GI malignancies

Abstract

Abstract Objectives: We have developed a novel humanized IgG1 monocolonal antibody, NEO-201, which targets a neoantigen expressed on ovarian and GI malignancies. This antigen has homology to CEACAM; however, it has specificity to tumor tissues and not normal tissues. Our aims were as follows: (1) to evaluate the expression of this antigen on tumor cell lines derived from various ovarian and GI cancers; and (2) to determine the functionality of NEO-201. Methods: Expression of the antigen was identified by western blot analysis and flow cytometry. Functionality was determined by an antibody dependent cell-mediated cytotoxicity (ADCC) assay using the antigen-expressing cell lines identified by western blot analysis. Cell lines not expressing the antigen were used as negative controls. The effector cells used in the ADCC assay were natural killer (NK) cells isolated from PBMCs of normal donors and high-affinity activated NK (haNK) cells. haNK cells are NK-92 cells genetically engineered to express the high-affinity variant of human CD16 (FcgRIIIA-V158) and the human IL-2 gene. haNK cells have little or no inhibitory expression of killer cell immunoglobulin-like receptors, a unique feature that may optimize their highly cytotoxic activity against a broad range of malignancies. Results: Using western blot analysis, 2 of 5 ovarian cancer cell lines (OV90 and PE01) and 1 of 2 colorectal cancer cell lines (LS174T) stained positively for NEO-201. Flow cytometry analysis on ovarian, colorectal, and pancreatic cancer cell lines confirmed the expression of the NEO-201 neoantigen on 1 of 2 ovarian cancer cell lines (OV90), 1 of 2 colorectal cancer cell lines (LS174T), and 2 of 2 pancreatic cancer cell lines (ASPC-1 and CFPAC-1). ADCC assay was performed using OV90 and ASPC-1 tumor cell lines. Cell lines not expressing the neoantigen were used as negative controls. Killing of tumor cells expressing the neoantigen was also observed with NEO-201 alone; however, the lysis was significantly augmented when NK cells from the PBMCs of normal donors or haNK cells were included in the ADCC assay. Conclusions: These finding demonstrate that the NEO-201 neoantigen is expressed on several tumor cell lines representing ovarian and GI malignancies. NEO-201 can mediate ADCC activity in the presence of NK cells and NK cell lines. In addition, NEO-201 can induce apoptosis in tumor cell lines expressing the NEO-201 neoantigen. Furthermore, preliminary studies demonstrated that this neoantigen is expressed in numerous cancer types (not shown). In vivo studies as well as IND-related studies are planned. Citation Format: Kristen Zeligs, Philip M. Arlen, Kwong Tsang, Lidia Hernandez, Massimo Fantini, Christina M. Annunziata. Preclinical characterization of a novel monoclonal antibody targeting a neo-antigen expressed in ovarian and GI malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3025. doi:10.1158/1538-7445.AM2017-3025