Table 1.

Lexicon of terms and definitions used to describe biosimilars

Term	Definition
Biologic	An approved product composed of proteins, nucleic acids, or combinations of these, or living entities such as cells and tissues, which is isolated from natural sources (including humans, animals, and microorganisms) and produced by biotechnology methods and other cutting-edge technologies [34]
Biosimilar	A biological product developed such that there are “no clinically meaningful differences between the biological product and the reference [originator] product in terms of safety, purity, and potency” and “demonstrates similarity to the [originator] in terms of quality characteristics, biological activity, safety, and efficacy based on a comprehensive comparability exercise” [1, 2, 6]
Generic drug	Small (single molecule) or low molecular weight chemically synthesized compounds consisting of a simple, well defined structure that is independent of the manufacturing process and easy to characterize completely [35]
Extrapolation	A core concept for approval of biosimilars, extrapolation allows for the approval of a biosimilar for use in an indication held by the originator not directly studied in clinical trials of the biosimilar. It is based on sufficient scientific justification and the totality of the evidence [1, 2, 29]
Interchangeable biosimilar	The product is approved as a biosimilar; the biosimilar can be expected to produce the same clinical effects as the originator in any given patient, and the risk in terms of safety or diminished efficacy of alternating or switching between use of the product and its originator is not greater than the risk of using the originator without such alternation or switch [23] NOTE: This designation is only granted by the FDA; the EMA and WHO do not provide any regulatory statement on whether or not a biosimilar is considered interchangeable [20, 21, 29]
Intended copy	Copies of an originator biologic that have not been evaluated using the stringent, specifically defined criteria of the EMA, FDA, or WHO guidelines for biosimilars [26]