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.

Manuscript.Compliance with Ethical Standards Amgen Inc. conducted and funded all analyses. Amgen Inc. also provided funding for medical writing and editorial support to MedVal Scientific Information Services, LLC, Skillman, NJ, USA. This article does not contain any studies with human participants or animals performed by any of the authors. This paper was prepared according to the ICMJE Uniform Re