Methods to Engineer and Identify IgG1 Variants with Improved FcRn Binding or Effector Function

Antibodies as therapeutic agents have gained broad acceptance as shown by the number of antibodies in clinical use and many more in clinical development. This utility is an outcome of the high specificity and affinity of the antigen-binding site comprised of the heavy and light chain variable domains. In addition, the Fc portion of human or humanized IgG₁ antibodies promotes long half-life through interaction with the recycling FcRn receptor and effects killing functions through interaction with complement and Fcγ receptors. Engineering the Fc portion to increase half-life through stronger binding to FcRn, or to increase complement or cell-mediated killing may lead to improved therapeutic antibodies. These improvements may benefit the patients through convenience in dosing or increased efficacy. Here we describe protocols for generating Fc-engineered IgG₁ antibodies and assays to measure Fc receptor binding, antibody dependent cellular cytotoxicity activity, and complement dependent cytotoxicity activity to identify variants with improved FcRn binding or effector function.