The development pathway of a biosimilar is unlike that of a novel biotherapeutic. Many regulatory authorities reference a stepwise approach to establishing biosimilarity. Analytical requirements are greatly increased before a product enters clinical testing. Enhanced analytical efforts entail physical, chemical, and biological characterization of a biosimilar product compared with an originator reference product. Strategies at this early stage must include intensive characterization of multiple batches to determine variability of quality attributes. Here I address some issues involved in meeting regulatory…