|This is a recombinant version of human G-CSF. The peptide is produced in E. coli and is non-glycosylated, whereas the naturally occurring peptide has an O-linked carbohydrate chain attached to Thr133. The carbohydrate chain protects the native peptide from degradation by human neutrophil elastase . Therefore, filgrastim is more quickly degraded and loses biological activity more rapidly in comparison to native G-CSF.
Biosimilar drugs: The potential for utilising filgrastim biosimilar agents in neutropenia management is discussed in . In March 2015, the US FDA approved the filgrastim biosimilar, Zarxio® (filgrastim-sndz) for the same indications as the reference product Neupogen®. This was the first biosimilar product to receive FDA approval. July 2018 saw FDA approval of the biosimilar Nivestym® (filgrastim-aafi), again for all eligible indications of the reference product. In the EU 7 filgrastim biosimilars received marketing authorisation between 2008 and 2014 (Ratiograstim®, Tevagrastim®, Filgrastim Hexal®, Zarzio, Nivestim®, Grastofil® and Accofil®, in order of approval), although some of these have since been withdrawn from the market.