Abstract 260: EpCAM-CD3 bispecific antibody-encoding mRNA delivered by lung targeted lipid nanoparticles suppresses orthotopic lung tumor growth.

Abstract The therapeutic use of bispecific T-cell engaging (BiTE) antibodies has shown great potential for treating malignancies. However, full exploitation of the potential of BsAbs is hindered by manufacturing challenges and short serum half-lives. In contrast, mRNA therapeutics have emerged as a powerful approach for treating a wide range of diseases. Their applications are increasingly linked to advancements in targeted delivery technologies and the production of mRNA encoded antibody is more flexible and cost-effective than the traditional method. In this work, We developed a lung selective organ targeting lipid nanoparticles (SORT LNPs)-formulated RNA (RNA-LNP) encoding a T cell-engaging bispecific antibody that binds the T cell marker CD3 and bivalently binds epithelial cell adhesion molecule (EpCAM), an epithelial antigen that is expressed on various solid tumors. We first performed In vitro flow cytometry analysis, which revealed that mRNA lipid nanoparticles (LNP) effectively mediated the killing of EpCAM positive tumor cells and activated human T cells. Then we established NCI-H441 lung orthotopic tumor model in PBMC humanized mice. We observed robust antitumor efficacy of mRNA LNP in this tumor model. To assess mRNA distribution, we quantified its content in various organs using qPCR. Results confirmed the lung targeting specificity of LNP. Moreover, we analyzed the activation of tumor-infiltrating T cells post mRNA LNP treatment. Finally, we conducted histopathological examination of various organs and we didn’t find signs of adverse effects from LNP formulated mRNA administration. In this comprehensive preclinical evaluation, we demonstrated that mRNA-encoded bispecific antibody promoted the activation and cytotoxicity of human T cells, exhibiting significant inhibition of orthotopic lung tumor growth in vivo. These findings underscore the potential research value of mRNA-encoded CD3-EpCAM T cell engager in treating solid tumors, marking a potential shift in the clinical application of protein-based T-cell engagers. Citation Format: Dong Wang, Gang Liu, Yuhe Han, Maorong Fu, Tingting Li, Xiangnan Qiang, Shunchuan Zhang, Zhixiang Zhang, Letian Kuai. EpCAM-CD3 bispecific antibody-encoding mRNA delivered by lung targeted lipid nanoparticles suppresses orthotopic lung tumor growth abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 260.