Filgrastim (trade name Neupogen) is a G-CSF analog used to stimulate the bone marrow to produce granulocytes and stem cells. Pegfilgrastim is a PEGylated form of G-CSF often used to fight infection in patients undergoing chemotherapy. PEGylation of recombinant biopharmaceutical products is performed to increase the half-life of the product. For example, Pegfilgrastim has a human half-life of 15-80 hours, compared to Filgrastim’s half-life of 3–4 hours.

Biosimilar Characterization Considerations

The guidelines state that characterization of Erythropoietin products should include determination of physicochemical and structural properties, purity, impurities and quantity in line with ICH Topic Q6B:

Structural Characterization

Physicochemical Characterization

Product Specific Technical Considerations

In addition to a PEGylation site assessment for the PEGylated product, particular attention should be paid to the Post Translational Modifications (PTMs) including:

  1. N-terminal heterogeneity
  2. Disulfide bridges
  3. Deamidation
  4. Oxidation