Of action. This is often an iterative process in which analytical similarity is tested and then further explored in preclinical biofunctional tests to determine whether minor differences, should they exist, result in differences in the biological activity of the molecule (Fig. 1). Confidence in the similarity of the molecule at this foundational step allows for a reduction in residual uncertainty

Le lots) and biofunctional parameters. The biofunctional parameters tested include an assessment of both binding and function within both the Fab and Fc portions of the mAb.Acknowledgments The authors thank Abhishek Mathur for scientific and technical contributions to the reported data and Jennifer Liu, Jill Crouse-Zeineddini, and Scott Kuhns for guidance on overall similarity assessment strategy.

Function testing. Teresa L. Born is the corresponding author and is responsible for the overall design and execution of the studies. Yuh-feng Chen is the subject expert for potency assessment and he contributed to the authoring and reviewing of this manuscript. Amanda Rohrbach, Christina Pastula, and Gwen Maher are the subject experts for binding assays and they contributed to the authoring and re