Development and Qualification of Potency Assays for Antibody-Drug Conjugates

Antibody–drug conjugates (ADCs) are a growing class of therapeutics that combine the specificity of monoclonal antibodies with a cytotoxic payload. Therefore, robust and biologically relevant potency assays are essential for supporting the development, comparability and lifecycle management of ADCs. However, the multimodal mechanisms of ADCs, including antibody binding, Fc-mediated functions, and payload-mediated cytotoxicity, present unique challenges for method design. In this study, development and qualification data for cell-based potency assays for ADCs is presented. Critical method parameters, such as cell seeding density, incubation conditions, and potency calculation, were optimised to ensure robustness and suitability across different potency levels. Additionally, the impact of varying the drug-to-antibody ratio (DAR) was evaluated. Qualification of the potency assay in accordance with the ICH Q2 guideline demonstrated acceptable high levels of accuracy, precision, linearity, method range and specificity. Collectively, results of the development and qualification of fit-for-purpose, mechanism-reflective potency methods are presented that support ADC development from early research through late-stage clinical programs. Contributing Authors: Frances Reichert Eurofins BioPharma Product Testing Munich GmbH, Planegg, Germany