Abstract 1863: α-ABN501, a novel antibody targeting claudin-3, demonstrates the potential to be a new therapeutic option for small cell lung cancer

Abstract Small Cell Lung Cancer (SCLC) is the most aggressive and lethal type of lung cancer, characterized by a poor prognosis, with a 5-year survival rate of only 7% for overall SCLC patients. Limited treatment options such as chemotherapy and immune-checkpoint inhibitor therapy are available for SCLC patients, very often followed by rapid recurrence and metastasis. Thus, new effective treatment options for SCLC remain high unmet medical needs. Overexpression of claudin-3 (CLDN3), one of the tight junction proteins, is observed in various types of cancers. The abnormal conformation of tumor cell growth leads to the external exposure of CLDN3, in contrast, the normal cells that maintain high polarity do not expose CLDN3 externally. Therefore, CLDN3 could be a potential therapeutic target and biomarker. Based on the analysis of the expression pattern of CLDN3 using a single-cell RNA sequencing dataset derived from SCLC patients, we found that CLDN3 could be a superior and unique target of SCLC compared to others (e. g. , DLL3 and B7H3). Hence, we developed a fully human monoclonal antibody, afucosylated ABN501 (α-ABN501), which has high specificity and strong affinity to CLDN3-expressing cells. The α-ABN501 antibody showed CLDN3-dependent killing effects against the SCLC cells, expressing different levels of CLDN3, as assessed via the antibody-dependent cellular cytotoxicity (ADCC) assay wherein using NK cells expressing CD16a (NK-92MI-CD16a), peripheral blood mononuclear cells (PBMC), and primary NK cells. Further, the efficacy study in the CLDN3-expressing SCLC cell derived xenograft mouse model revealed that α-ABN501 was highly efficacious in inhibition of tumor growth. Collectively, we elucidated that the ADCC activity of α-ABN501 was dependent on the expression level of CLDN3 and especially specific to the SCLC cells, which underlines significant suppression of tumor growth. Present study data sets suggest that the α-ABN501 can be a potential new therapeutic option for SCLC. In addition, the α-ABN501 antibody is currently under way of development into new drug platforms for further applications. Citation Format: Jae Choi, Sunghyun Hong, Ha Yeon Park, Jaemun Kim, Sangin Lee, Myeung-Ryun Seo, Sang-Beom Bang, Hyo-Jin Shin, Kwang-il Jeong, Hobin Yang, Sungyoul Hong, Jun Young Choi, Na Young Kim, Young Kee Shin, Saehyung Lee. α-ABN501, a novel antibody targeting claudin-3, demonstrates the potential to be a new therapeutic option for small cell lung cancer 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 1863.