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Improving Cell-Mediated Cytotoxicity Assessment through the Use of an Automated Luminescent ADCC AssayDownload
February 08, 2012
Authors: Brad Larson and Peter Banks, BioTek Instruments, Inc., Winooski, Vermont, USA; Sumant Dhawan and Shalini Wadwani, Cell Technology, Inc., Mountain View, California, USA
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/neu 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. Here we describe the use of a non-radioactive luminescent chemistry to simplify the assay process and provide improved data quality. Recruitment of NK cells by the proper antibody leads to lysis of the target cell. This causes release of Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH) from the cell. ATP production ensues, which is coupled to a luciferase/luciferin reaction producing a luminescent signal. No target cell preparation time is necessary, and shortened incubation times mean the procedure can be completed in half the time of the original procedure, without any complicated and expensive regulatory permissions. The assay is easily automated in 96-well format to further simplify the procedure. Experimental data generated with fresh as well as cryopreserved NK cells, using multiple effector:target cell ratios, will be shown to prove the validity and flexibility of the method.