Principles of Analytical Similarity Assessment

Detailed evaluation of the similarity in structural and functional properties between a proposed biosimilar product and the reference product necessitates a carefully designed analytical study program. Although regulatory agencies, such as EMA and US FDA, have published guidance documents outlining the requirements for analytical similarity assessment, the implications are often not fully understood by biosimilar developers. This chapter discusses important considerations for all aspects of the design of the analytical similarity assessment, including the selection of the test materials; the product characteristics to be compared, and the associated analytical testing methods and plan; suitability of analytical procedures, in design and performance; processing and interpretation of analytical test data; and the methods for assessment of analytical study results. The design of comparative forced degradation studies, intended to compare the pattern and kinetics of product degradation, is also discussed. Differences in regulatory expectations between EU and USA are identified, together with their implications for the conception of a study program intended to support product approval in both jurisdictions.