Following passage of the Biologics Price Competition and Innovation (BPCI) Act in 2009, the FDA circulated three guidances on the demonstration of biosimilarity of biosimilar products for public comments in April 2015 (FDA, 2015a,b,c). These guidances are intended not only (1) to assist sponsors to demonstrate that a proposed therapeutic protein product is biosimilar to a reference product for the purpose of submitting a marketing application under Section 351(k) of the Public Health Service (PHS) Act, but also (2) to describe the FDA’s current thinking on factors demonstrating that a proposed protein product is highly similar to a reference product, which was licensed under Section 351(a) of the PHS Act. In the guidance on Scientific Considerations in Demonstrating Biosimilarity to a Reference Product, the FDA introduces the concept of a stepwise approach to obtaining “Totality of the Evidence” for the regulatory review and approval of biosimilar applications (FDA, 2015a).