Abstract LB227: Leveraging novel Dato-DXd resistance models to inform biomarker discovery and rational combinations to combat drug resistance
Authors: Przybyla Anna , Rane Chetan , Patel Gopi , Bhavsar Deepa , Wen Shenghua , Clark David , Kim Yeoun Jin , Lau Alan , Wallez Yann , Mettetal Jay , Zhong Wenyan , Sung Matthew 
Published: April 2023

Abstract
Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate (ADC) consisting of a humanized anti-TROP2 IgG1 monoclonal antibody covalently linked to a highly potent topoisomerase I (TOP1) inhibitor payload via a stable, tumor-selective, tetrapeptide-based cleavable linker. Despite its promising early clinical signals, drug resistance is a challenge that may emerge with time. The mechanisms of Dato-DXd resistance are currently unknown. Herein, we created and investigated novel models of Dato-DXd resistance to characterize resistance mechanisms and identify novel combinations to overcome Dato-DXd resistance. We used a cyclical dosing method to develop two Dato-DXd acquired resistant NCI-N87 gastric cancer cell line models from in vitro cells (N87-IVR) and in vivo tumors (N87-EVR). The N87-IVR and N87-EVR cells were found to be more than 40-fold resistant to Dato-DXd compared to the parental N87 cells. First, we assessed TROP2 levels, Dato-DXd binding and expression of drug efflux pumps known to have TOP1-inhibitor substrates between the parental and resistant cell populations. Minor changes in each of these were not sufficient to drive Dato-DXd resistance in the drug-tolerant models. Subsequently, we performed a proteogenomic analysis to identify which proteins and pathways were modulated in the resistant phenotype. Both the N87-IVR and N87-EVR cells were divergent from the parental N87 cells and, interestingly, they showed similar yet distinct profiles. Among other changes, our analysis revealed a dramatic loss of SLFN11, a putative DNA/RNA helicase, in both resistant models. Previously published data has shown that a combination with an ATR inhibitor (ATRi) can re-sensitize TOP1 inhibitor-resistant cells in SLFN11-low settings. Consistent with these data, we observed that the ATRi ceralasertib (AZD6738) in combination with Dato-DXd re-sensitizes the resistant NCI-N87 cells in vitro and in vivo. In addition to SLFN11 loss, we also identified a number of other modulations with the potential to drive resistance, e.g. downregulation of the caveolin internalization machinery and interferon response genes. These findings help us refine the mechanism of action of Dato-DXd and shed light on the potential mechanisms of Dato-DXd resistance that may emerge clinically. These data have been used to uncover new biomarkers of Dato-DXd sensitivity and can lead to the development of new clinical strategies to combat Dato-DXd resistance, e.g. the combination with ATRi.
Citation Format: Anna Przybyla, Chetan Rane, Gopi Patel, Deepa Bhavsar, Shenghua Wen, David Clark, Yeoun Jin Kim, Alan Lau, Yann Wallez, Jay Mettetal, Wenyan Zhong, Matthew Sung. Leveraging novel Dato-DXd resistance models to inform biomarker discovery and rational combinations to combat drug resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB227.