Abstract 5500: A customizable, end-to-end platform for the screening and characterization of ADCs

Abstract Chemotherapy and radiotherapy have been considered the first line of antitumor therapies for patients with advanced or metastatic cancer, however these therapies demonstrate numerous drawbacks and acquired resistance is still inevitable in most cases. In order to address these challenges, scientists have discovered a novel class of cancer-targeted drugs referred to as antibody-drug conjugates (ADCs). ADCs are an emerging class of therapies that conjugate monoclonal antibodies with cytotoxic payloads through a chemical linker, allowing precise delivery of drugs to cancer cells. Trastuzumab deruxtecan (T-DXd) is an ADC composed of a humanized IgG antibody that specifically targets HER2, a tetrapeptide-based cleavable linker and a topoisomerase I inhibitor payload. T-DXd is the second HER2-targeting ADC approved by the FDA after trastuzumab emtansine (T-DM1); approved for HER2-positive unresectable or metastatic breast cancer in the second line and as an adjuvant therapy for residual disease in breast cancer patients with early stage disease. Both ADCs have demonstrated promising clinical efficacy in the treatment of HER2-positive solid cancers, which has sparked great interest in the development of the next generation of ADCs. Emerging evidence indicates that the efficacy of a given ADC depends on a number of key factors including the fine tuning between the combination of the antibody, linker and payload components, how the ADC is processed and it’s interaction with the cancer cells. Here we present robust and reproducible data from our comprehensive modular in vitro and in vivo screening platform, that has been developed to facilitate efficient and streamlined approaches for ADC screening and characterization, and have been validated using T-DXd and T-DM1 as proof-of-concept agents. Our platform offers assays that can evaluate ADC binding, internalization, anti-proliferative activity, ADC effects on cell cycle, apoptosis, and bystander effects. Immunological assays, such as antibody-dependent cellular cytotoxicity (ADCC), and antibody-dependent cellular phagocytosis (ADCP) can be employed to assess the induction of Fc effector functions. Additionally, we have validated a number of in vivo models including co-inoculation and intracranial xenograft models. Our data demonstrates that both ADCs exhibit strong binding and internalization, with T-DXd showing a pronounced bystander effect due to its payload release via a cleavable linker. Both agents effectively induced ADCC and ADCP, with minimal complement-dependent cytotoxicity observed. The T-DXd bystander effect was also confirmed used an in vivo co-inoculation xenograft model and efficacy of both T-DXd and T-DM1 against a human intracranial xenograft model was confirmed. This platform provides a comprehensive and customizable tool for ADC preclinical assessment, supporting the optimization of ADC therapeutic efficacy and safety. Citation Format: Zichun Wang, Qiong Wang, Shuyue Wang, Guilan Wang, Qikuan Chen, Wei Xue, Yinfei Yin. A customizable, end-to-end platform for the screening and characterization of ADCs [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 5500.