Bioassays are pivotal in developing and controlling biological products. The ideal bioassay measures the relevant function of the molecule in a precise manner, preferably in a cell-based assay format, which reflects the mechanism of action of the product. Over the last decades, bioassay capabilities have improved dramatically in both relevance and precision and have become an even more important tool in quality control, stability testing, extended characterization and comparability as well as in analytical biosimilarity assessments. This technical session will focus on the current state-of-the-art of bioassay capabilities and its application for development of therapeutic monoclonal antibodies. This product class confers their clinical effects via a variety of different functions, ranging from downstream events due to target binding by the Fc region to biological impacts associated with Fc functions such as antibody-dependent, cell-mediated cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and antibody-dependent cellular phagocytosis (ADCP). These functions are typically identified and assessed using cell-based systems; however measuring binding properties to the different binding partners including Fc receptors is an important orthogonal addition for a comprehensive characterization of the functional properties of a monoclonal antibody. This session will focus on the current knowledge and challenges in the technical development of bioassays for monoclonal antibodies. Case studies will illustrate today’s bioassay capabilities and application throughout the product lifecycle with information that can be applied to other protein products.