Abstract 2930: Intrinsic payload resistance governs responses to datopotamab deruxtecan, a TROP2 antibody drug conjugate, in pancreatic cancer model systems

Abstract Introduction- TROP2, a transmembrane glycoprotein encoded by the TACSTD2 gene, is overexpressed in pancreatic cancer (PC) and contributes to cancer progression. Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate targeting TROP2, utilizing a novel linker technology that is only cleaved following internalization. It has demonstrated clinical activity in breast and lung cancers and is under investigation in PC. Determinants of response and resistance to ADCs are not well studied. Here, we investigate predictors of Dato-DXd efficacy in PDAC using in vitro models. Method-Twenty six PC cell lines with varying TROP2 mRNA levels were tested using Dato-DXd, isotype control-DXd, and naked toxin DXd in 96-well plates using CellTiter-Glo®. Drug sensitivity was correlated with mechanism based predictors using Pearson’s correlation. Cell surface TROP2 was quantified using QIFIKIT; antibody internalization was analyzed using iQue® Human Antibody Internalization Reagent and quantified with Quantum™ MESF microsphere kit. Cathepsin B activity was measured with the Magic Red® Fluorescent Cathepsin B Assay Kit.Result-To identify factors influencing response and resistance, we used the ratio of AUC (Area Under the Curve) of Dato-DXd to AUC of Isotype-DXd (AUC Dato/Isotype) as a standardized measure of efficacy. AUC Dato/Isotype approaching 1 indicate no activity of Dato-DXd over isotype control, and lower values signify selective cytotoxicity mediated by Dato-DXd. We noted no activity of Dato-DXd in cell lines lacking surface expression of TROP2 (n = 4), whereas responses varied among TROP2+ lines. To explore predictors of Dato-DXd response in TROP2+ cell lines (n = 22), we examined the relationship of TROP2 mRNA levels, TROP2 surface expression, Dato-DXd internalization, and Cathepsin B activity with Dato-DXd sensitivity, using Pearson correlation. AUC of the DXd (payload) is highly correlated with the Dato-DXd sensitivity (r = 0.63, p = 0.002). Further review of sensitivity of to DXd showed natural separation of tested models into DXd sensitive and resistant models at 1nM DXd concentration. Lines resistant to DXd at 1 nM showed significantly higher resistance to Dato-DXd (two-tailed t-test, t = 7.34, p < 0.0001). Conclusion-PC in vitro models reveal a range of sensitivities to Dato-DXd. We found that TROP2 expression is necessary but not sufficient for sensitivity to Dato-DXd and intrinsic resistance to payload is highly correlated with resistance to Dato-DXd. Ongoing analyses to identify additional predictors of response to Dato-DXd using whole transcriptome profiles of tested models will be presented. Citation Format: Panot Sainamthip, Kazuki Takahashi, Jiajia Chen, Junning Wang, Julien Dilly, Seema Chugh, David Lui, Andrew J. Aguirre, Harshabad Singh. Intrinsic payload resistance governs responses to datopotamab deruxtecan, a TROP2 antibody drug conjugate, in pancreatic cancer model systems [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 2930.