Determination of Similarity Margin in Comparative Clinical Studies to Support the Development of Biosimilar Products of Neupogen ® (Filgrastim, Granulocyte Colony-Stimulating Factor [G-CSF]).

To demonstrate a biological product is biosimilar to a reference product, the applicant needs to show that the product is highly similar and has no clinically meaningful differences. Comparative clinical studies are often conducted to support the conclusion of no clinically meaningful differences, as a part of totality of evidence. The FDA has published several guidance documents to facilitate the development of biosimilar products. While the guidance documents define the role and objective of comparative clinical studies, they do not provide details about the determination of the similarity margin. In this paper, we illustrate a similarity margin derivation for a surrogate endpoint in comparative clinical studies conducted to assess whether clinically meaningful differences exist between Neupogen® (Filgrastim, granulocyte colony-stimulating factor) and products proposed to be biosimilar to Neupogen® .