Development of a kinetic antibody-dependent cellular cytotoxicity assay

Antibody-dependent cellular cytotoxicity (ADCC) is an important mechanism of action (MOA) of monoclonal antibody (mAb) therapeutics. Target cells opsonized with therapeutic antibody bind and activate Fc gamma R-bearing immune effector cells, resulting in target cell lysis. A key step in mAb drug development is the characterization of ADCC activity for its potential to inform mAb efficacy and safety. A number of in vitro assays are commonly used to assess ADCC. Most are endpoint assays that measure a surrogate marker of cell lysis. Newer imaging technologies allow direct measurement of ADCC-mediated cell lysis over time. In this study, we detail the development and characterization of a kinetic ADCC assay applicable to multiple target and effector cell types. This kinetic assay shows comparable sensitivity to an endpoint fluorescence release ADCC assay, while offering the advantages of a simpler set up and shorter assay time. Our results demonstrate that kinetic ADCC activity is a valid alternative assay format for measuring in vitro ADCC of mAbs.