Since the end of the 1990’s, the pharmaceutical industry has seen an increased interest in biologics, especially in the therapeutic areas of oncology and inflammation. The selection of potent and selective Mabs (monoclonal antibodies) for specific target receptors, such as Receptor Tyrosine Kinase (RTK) and G protein-coupled receptors (GPCRs), is the first step in successfully developing an antibody based drug. In addition to potent binding, some antibodies have the ability to recruit the immune system effector cells, a process known as ADCC (Antibody Dependent Cell Cytotoxicity). The ability to promote ADCC is an important attribute of successful candidates and for that reason should be sought in the final drug design.
Here we present the automation of two assays for the characterization and selection of potent antibody drug candidates. Both assays rely on HTRF® detection. The first assay quantifies the binding affinity of antibodies to their target antigen, on live cells. The second assay measures the affinity of the antibody Fc portion to the CD16 receptor also on live cells. As Fc-CD16 binding affinity correlates well with effector function, this method is a simple, yet efficient and precise way of assessing biological activity through ADCC.
Each assay procedure has been automated through the incorporation of easy-to-use, robust instrumentation. An 8-channel liquid handler is used for antibody titration and transfer to the lowvolume 384-well assay plates. Cell and reagent dispensing are then carried out using a non-contact liquid dispenser. The small footprint of the instrument, and ability to autoclave the dispensing pathway, allow for sterile manipulations of each component. Binding, as well as antibody competition experiments were performed to validate the automated assay procedure. Results demonstrate that the combination of assay and instrumentation create a powerful, easy to use and efficient method to screen and characterize antibodies being considered for use in ADCC applications.