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 using genetically engineered cell lines or purified NK cells from blood. Each has its own strengths, and can be the assay of choice depending on the needs of the researcher. In addition, these new assay chemistries are amenable to automated processing and can be detected using microplate readers. This can serve to further simplify the procedure and make a more robust process. This was initially demonstrated through multiple poster and oral presentations at the recent SLAS Conference, and will continue to be illustrated through our presence at a number of important upcoming biological therapeutic focused conferences.
How do you see biological therapeutics continuing to reshape the drug discovery process? What type of bioassays would you like to see automated in your lab?
By: BioTek Instruments, Brad Larson, Principal Scientist