Antibodies mediate a large array of functions—from functions that directly eliminate pathogens such as induction of phagocytosis and driving natural killer cell–mediated cytotoxicity to accessory functions such as assisting in antigen capture and presentation to drive more effective B and T cell response. Critically, however, only some of these functions may be desired for a given monoclonal antibody to have therapeutic efficacy, and through the engineering of the Fc domain it is possible to generate monoclonal antibodies with specific functional profiles. Systems Serology can be used to evaluate the functional profile of panels of monoclonal antibodies and Fc variants, allowing for the selection of candidates with the optimal functional profile.
The SARS CoV2 pandemic is the most destructive infectious disease outbreak in living memory, with over 200 million cases reported globally resulting in over 4 million deaths. The scientific response to the pandemic has been unprecedented, resulting in the rapid development, testing, approval, and deployment of therapeutics, vaccines, and diagnostics to improve management and ultimately control of the disease. Among the therapies that have been developed and tested as potential therapeutics are a large number of monoclonal antibodies. Many of these monoclonal antibodies were produced on modified Fc domains, with the goal of increasing the antibody half-life, enhancing some or all antibody functions, or eliminating antibody function entirely. However, while many of these modified Fc domains were originally selected based on their altered binding to particular Fc receptors, changes in the Fc domain of an antibody can result in off-target effects where binding to other Fc receptors is enhanced or compromised, potentially altering the Fc functionality of the antibody. Here, Systems Serology was used to evaluate the functional activity of a panel of monoclonal antibodies that had been modified specifically for increased binding to FcRn, which should result in an increased serum half-life with a minimal impact on the functional activity of the antibody.
Systems Serology Application
While increased binding to FcRn was readily observed with the panel of Fc-modified monoclonal antibodies, the Fc-modified antibodies demonstrated altered binding to other Fc receptors. These results suggest that the targeted modifications made to the Fc domain to enhance the serum half-life of the antibody could significantly alter the functional activity of the monoclonal antibodies. When the functional activity of this panel of monoclonal antibodies was evaluated, virtually all antibody functions were reduced on the Fc-modified backbone, including the ability of the antibody to induce NK cell–dependent cytotoxicity, complement deposition, and phagocytosis by neutrophils. In fact, of the tested antibody functions, only one function—antibody-dependent cellular phagocytosis—was not negatively impacted by the half-life extending modification, demonstrating the significant off-target impacts that Fc modification can have on antibody functionality. Critically, for this panel of monoclonal antibodies, one antibody, despite demonstrating reduced activity when compared to the unmodified Fc domain, exhibited acceptable levels of functional activity, and this antibody was selected for further clinical development.
The comprehensive profiling of a panel of SARS CoV2–specific monoclonal antibody variants using Systems Serology demonstrated a potentially significant impact to the functional activity of a monoclonal antibody by Fc domain modification. Critically, as these off-target changes in antibody function could possibly alter the efficacy of an antibody, following Fc modification of potential clinical candidates, critical antibody functions need to be evaluated to demonstrate that the targeted functional profile of the antibody has not been adversely affected. As monoclonal antibody therapeutics will likely continue to play a role in limiting the spread of emerging infectious diseases, the Systems Serology suite of assays offered by SeromYx provides a platform in which antibody functionality can be robustly measured, ultimately providing critical information on the functionality of monoclonal antibodies that are moving further into clinical development.