Abstract 7149: The role of TROP2 in the MoA of Dato-DXd and how it underpins the biologic rationale of the novel AI-guided biomarker TROP2 normalized membrane ratio

Abstract Datopotamab deruxtecan (Dato-DXd) is an antibody drug conjugate (ADC) comprised of a humanized anti-TROP2 IgG1 monoclonal antibody attached to DXd, a topoisomerase I inhibitor, via a plasma stable cleavable linker. Dato-DXd is currently under clinical investigation for the treatment of patients with solid tumors including non-small cell lung cancer (NSCLC), hormone receptor positive and triple negative breast cancer. Recently, TROP2 Normalized Membrane Ratio (NMR) was identified as an exploratory predictive biomarker for Dato-DXd, in patients with non-squamous (NSQ), non-actionable genomically altered (AGA) NSCLC in the phase 3 TROPION-Lung01 study. TROP2 NMR is a quantitative scoring algorithm that measures membrane TROP2 expression relative to the combined sum of cytoplasmic and membrane TROP2 expression for every tumor cell in a TROP2 immunohistochemistry (IHC) stained tissue sample. Herein, we further describe the role of TROP2 in the mechanism of action (MoA) for Dato-DXd and the biological rationale linking TROP2 NMR to its pharmacological mode of action. Utilizing an isogenic cell line series in NCI-H322, a NSQ, non-AGA NSCLC cell line, where TROP2 was either knocked-out (KO) or over-expressed, we demonstrate that Dato-DXd binding and efficacy is dependent on TROP2 expression. TROP2-KO resulted in complete loss of Dato-DXd binding, delivery of intracellular DXd, in vitro cytotoxicity and in vivo efficacy of Dato-DXd implicating the MoA of Dato-DXd requires TROP2. However, TROP2 expression was not sufficient to predict Dato-DXd activity in a broad panel of cell lines across multiple indications including NSCLC. In 34 NSCLC cell lines, TROP2 mRNA expression generally correlated with Dato-DXd activity, however, among the TROP2-high NSCLC cell lines (n=17), there was a mixture of Dato-DXd sensitive and insensitive cell lines. As internalization of the Dato-DXd-bound TROP2 complex is central to its MoA, we measured the internalization capacity of Dato-DXd in NSCLC cell lines (n=15). Dato-DXd internalization required binding to cells, however, there was a differential capacity for Dato-DXd internalization across cell lines despite similar levels of Dato-DXd binding. Importantly, characterization of the TROP2 IHC staining pattern revealed a strong correlation between TROP2 NMR, but not membrane nor cytoplasmic TROP2, and Dato-DXd internalization capacity and efficacy across these NSCLC cell lines. This suggests TROP2 NMR can predict the innate internalization capacity of Dato-DXd from TROP2 IHC stained samples. Collectively, these data highlight the key role TROP2 plays in the MoA of Dato-DXd in preclinical NSCLC models and provides the molecular basis underpinning the biological rationale for TROP2 NMR as an innovative biomarker for Dato-DXd activity in NSCLC. Citation Format: Matthew S. Sung, Matthew Wilson, Dominik Vonficht, Armin Meier, Chetan Rane, Charlie Dunlop, Gopi Patel, Anna Przybyla, Yann Wallez, Xiaochuan Liu, Ross Hill, James Harper, Markus Shick, Hadassah Sade, Danielle Carroll. The role of TROP2 in the MoA of Dato-DXd and how it underpins the biologic rationale of the novel AI-guided biomarker TROP2 normalized membrane ratio [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 7149.