Abstract B094: Modelling ADC sensitivity and mode-of-action in human cancer derived organoids

Abstract Background: Antibody-drug conjugates (ADCs) represent an innovative approach in targeted cancer therapy, combining antibodies' specificity with therapeutic modalities such as cytotoxic or targeted chemical compounds. This study presents an organoid-based ADC testing platform, leveraging patient-derived organoids (PDO/PDXO), combined with CRISPR engineering and advanced 3D high-content imaging (HCI). Method: Efficacy of EMA & FDA-approved ADC Trodelvy (Sacituzumab-Govitecan), was evaluated in the CellTiter-Glo (CTG)-based OrganoidXploreTM panel, a 3D in vitro screening panel of 50 organoid models across 7 indications. The panel was characterized by NGS (WES, RNAseq) but selected without bias for TROP2/TACSTD2 expression. Efficacy of a second TROP2 ADC, Datroway (datopotamab-deruxtecan/DS-1062), was independently tested in 3 selected models, including isogenic CRISPR/Cas9-induced TROP2 knockout organoids. Subsequently, ADC efficacy, target-engagement, uptake and payload mode-of-action were assessed by HCI. Results: Trodelvy demonstrated differential responses (<0.01nM<IC50<50nM) in the OrganoidXploreTM panel, with 18 models showing high sensitivity (IC50<0.01nM). Response rates did not correlate with mRNA expression of TROP2/TACSTD2. Successful target engagement and on-target efficacy was confirmed by HCI of 3 selected responder organoids and their isogenic TROP2 knock-out counterparts. This confirmed correspondence between mRNA and protein expression levels, and reaffirmed the lack of correlation between Trodelvy and Datroway sensitivity and target expression. These observations stress that efficacy in patient-derived tumor organoids is not primarily driven by absolute TROP2/TACSTD2 levels but rather through uptake dynamics and ADC mode-of-action. Indeed, slower uptake dynamics and payload sensitivity were observed in an organoid model with milder Trodelvy and Datroway toxicity. Finally, increased Datroway resistance and payload sensitivity was further confirmed in isogenic TROP2 knock-out organoid pairs. Conclusion: In conclusion, the OrganoidXplore™ screening platform in combination with HCI provides crucial insights into ADC efficacy, target engagement and mode-of-action. Using isogenic CRISPR-edited organoid pairs subsequently provided critical insights on the mechanisms driving ADC responses. Combined, this unveils a lack of correlation between target expression (mRNA and protein) and drug efficacy, and stresses the importance of functional ADC testing across a diverse patient population. The application of HCI for additional characterization, including ADC binding and uptake assays, will be a pivotal step in identifying optimal new ADC candidates. These findings highlight the application of functional screening in organoids to better understand the complexity of ADC efficacy and identify responder/non-responder patient profiles. Additionally, CRISPR-edited organoids can be applied in the future to model ADC resistance and off-target toxicity. Citation Format: Marten Hornsveld, Lenno krenning, Dorrith Verstegen, Caitlyn Hulsebosch, Peter van Schaik, Mariusz Madej, Hester Bange, Ludovic Bourre, Marrit Putker. Modelling ADC sensitivity and mode-of-action in human cancer derived organoids [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2025 Oct 22-26; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2025;24(10 Suppl):Abstract nr B094.