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Novel, Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC) AssaysDownload
May 04, 2012
Authors: Brad Larson and Peter Banks, BioTek Instruments, Inc., Winooski, Vermont; Sumant Dhawan, Shalini Wadwani and Stéphane Martinez, Cell Technology, Inc., Mountain View, California; Nicolas Pierre and Francois Degorce, Cisbio US, Inc., Bedford, Massachusetts
The success of biologic therapeutics has begun to reshape today’s pharmaceutical market. The first and most successful of these antibody therapies, Rituximab (Rituxan®; Roche/Genentech), showed worldwide sales in 2009 of $5.6 billion (GEN News Highlights, 2011). This, among others including Trastuzumab (Herceptin®; F Hoffman-La Roche), have shown great promise for treatment of patients with leukemia, lymphomas, breast, and other cancer types due to their specificity and reduced side effects (Zhou, 2007). One of the mechanisms which play a central role in the response to clinical antibody therapy is antibody-dependent cell-mediated cytotoxicity (ADCC) (Wang, 2008). This involves the response of natural killer (NK) cells to bind to specific antibody-coated target cells, such as CD20 and HER2 expressing cells, to promote the death of the target cell.
With many of the existing patents covering these treatments set to expire in the next few years, the development of biologic therapeutics similar to the original drug (biosimilars) has become increasingly important. This is highlighted by the report that Spectrum Pharmaceuticals and Viropro are set to work together to develop a biosimilar to Rituximab (GEN News Highlights, 2011). As a direct result, assays that can assess the ability of a biosimilar to act in a manner similar to the original biologic have also seen increased interest. The current “gold standard” ADCC assay incorporates 51Cr. The procedure involves labeling and incubating target cells with the radioligand, assessment of the labeling procedure, and finally performance of the actual assay. Not only is this time consuming, but involves the use and eventual costly disposal of radioactive material.
A number of new cell-based technologies have been, and continue to be, developed that are easier to use than 51Cr, less time consuming, and do not include the use of radioactivity. These include high-throughput methods that separately assess antibody binding to target as well as CD16 receptors, as well as medium-throughput methods that assess this binding in one assay. Each has its own strengths, and can be the assay of choice depending on the needs of the researcher, or the point in development at which the testing is taking place. In addition, these new assay chemistries are amenable to automated processing and can be detected using microplate readers. Here we describe the automation of two such chemistries. The first targeted towards early identification of lead antibody candidates, and the second ideal for confirmation of final therapeutic formulations using actual human natural killer (NK) cells. Results demonstrate how the combination of assay and instrumentation create robust, efficient, and easy-to-use methods for the identification and validation of antibodies being considered for use in ADCC applications.