Abstract 1654: Bioluminescent and cell-based assays for comprehensive characterization of antibody-drug conjugate mechanisms of action

Abstract The growing field of targeted therapeutics has led to the emergence of Drug Conjugates, including antibody-drug conjugates (ADCs), protein-drug conjugates (PDCs), and other payload-conjugated biologics that integrate selective delivery with potent cytotoxic payloads. These modalities exert therapeutic effects via multiple mechanisms of action (MoA), including direct cytotoxicity following receptor binding and internalization, bystander killing via cleaved payload diffusion, antigen function blockade, and immune-mediated cytotoxicity such as ADCC and ADCP, driven by Fc effector function. Effective characterization and potency assessment of ADCs require robust in vitro tools that capture these complex MoA. Here we present a panel of bioluminescent and cell-based assays to support the pharmacological profiling of ADCs. The Lumit® Ligand Binding Assay provides a homogeneous solution-phase format to quantify antigen engagement by mAbs and ADCs, enabling efficacy and QC assessments. The Lumit® FcRn Binding Immunoassay evaluates FcRn-ADC interactions to inform half-life predictions and Fc engineering. Fcγ receptor binding, uptake, and C1q engagement are assessed through Lumit®-based and cell-based formats, offering insights into immune effector functions and FcγR-mediated toxicity. Additionally, a bioluminescent ADC Internalization Assay tracks intracellular trafficking, enabling payload delivery characterization and identification of dose-limiting toxicity risks. Together, these assays offer scalable, reproducible platforms for PK, PD, and toxicity evaluation in ADC development. Citation Format: Mei Cong, Yitong Li, virginia Kincaid, Morten Seirup, Christopher Eggers, Rod Flemming, Jim Hartnett, Kristin Riching, Jamison Grailer, Julia K. Gilden. Bioluminescent and cell-based assays for comprehensive characterization of antibody-drug conjugate mechanisms of action [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 1654.