Simultaneous analysis of filgrastim and pegfilgrastim aggregates by size-exclusion chromatography.

A new size-exclusion high-performance liquid chromatographic (SE-HPLC) method for the simultaneous analysis of filgrastim and pegfilgrastim aggregates was developed and validated. A cross-linked agarose and dextran column was used at ambient temperature and an alkaline sodium phosphate buffer as mobile phase eliminated non-ideal interactions with the stationary phase. The robustness of the method was assessed by varying injection volumes, flow rates and sample vehicles. Other reliability assessments include calibration curve, intra and inter-day precision and accuracy, repeatability of retention times, application to real in-process production samples and column lifetime. The method exhibited linearity over the concentration of 0.02-4 mg/ml range for filgrastim and pegfilgrastim monomer with a correlation coefficient of greater than 0.999. The lower limit of quantification was 0.02 mg/ml and the limit of detection was 0.005 mg/ml. This SE-HPLC technique has been successfully used for several years and more than 10,000 samples.

Structural similarity, characterization of Poly Ethylene Glycol linkage and identification of product related variants in biosimilar pegfilgrastim.

The approval of biosimilars requires demonstration of biosimilarity, which rests on the base of thorough analytical characterization of the biosimilar product. In addition to demonstration of biosimilarity, the product related impurities need to be thoroughly characterized and controlled at minimal levels. Pegylation of peptides and proteins creates significant challenges for detailed structural characterization, such as PEG (Poly Ethylene Glycol) heterogeneity, site of addition and number of attached pegylated moieties. A combination of several methods including circular dichroism, FTIR (Fourier-transform Infrared Spectroscopy), fluorescence spectroscopy, DSC (Differential Scanning Calorimetry), 1D and 2D NMR (Nuclear Magnetic Resonance), Edman degradation and peptide mapping by LC-MS (Liquid Chromatography Mass Spectrometry) were used for characterization of N-terminally pegylated filgrastim. Product related impurities such as oxidized, reduced, deamidated, dipegylated variants and monopegylated positional isomers have been characterized in detail using various HPLC (High Performance Liquid Chromatography) based methods and LC-MS techniques. The functional characterization in terms of receptor binding and cell proliferation assay was conducted for the similarity assessment and the potential impact of the product variants on the in vitro biological activity has also been assessed. In summary, this study presents, for the first time, a detailed structural and molecular level characterization of a biosimilar pegfilgrastim providing a strong base for the demonstration of overall biosimilarity of the product with the innovator product.

Analytical Comparison of the Originator Granulocyte-colony Stimulating Factor Filgrastim and its Biosimilars.

PURPOSE: Filgrastim, a recombinant human granulocyte colony-stimulating factor (rhG-CSF) produced in Escherichia coli, is indicated for treatment of neutropenia-related conditions in cancer patients. It has been marketed as Neupogen since 1991. In 2006, biosimilar rhG-CSF products have been approved in the European Union (EU). The aim of this study was to compare quality attributes of the originator filgrastim with its three biosimilars which came from the EU market in 2014 to verify whether their similarity is maintained since their market approval. MATERIALS/METHODS: Spectrophotometric analysis was used to determine protein content in analyzed products. Chromatographic and electrophoretic analyses were applied to verify the presence of high and low-molecular weight impurities. Secondary and tertiary structure of the drugs were investigated with circular dichroism and intrinsic fluorescence. Finally, biological activity of the drugs was assessed using cell proliferation assay. RESULTS: All products displayed protein content close to the label concentration with a ±6% variation. Two oxidized forms and a deamidated form were present at <0.5%. Levels of dimers and other high molecular-weight impurities were similar except for one product, which contained higher amount of the dimer. Profiles and levels of process-related impurities were comparable. The three-dimensional conformation of the molecules with respect to exposed tryptophan residues was similar. The relative potencies of the products were comparable to the reference standard with a ±2% variation. CONCLUSION: This study shows that a high level of similarity is maintained among originator and three biosimilar filgrastims up to 5 years from their first registration in the EU.

A demonstration of analytical similarity comparing a proposed biosimilar pegfilgrastim and reference pegfilgrastim.

BACKGROUND: Recombinant human granulocyte-colony stimulating factor (G-CSF, filgrastim) is used primarily to reduce incidence and duration of severe neutropenia and its associated complications in cancer patients that have received a chemotherapy regimen. The pegylated form of filgrastim, "pegfilgrastim", is a long-acting form that requires only a once-per-cycle administration for the management of chemotherapy-induced neutropenia. Apobiologix, a division of ApoPharma USA, Inc., and Intas Pharmaceuticals Limited have co-developed a proposed pegfilgrastim biosimilar to US-licensed pegfilgrastim. METHODS: The analytical similarity of Apobiologix pegfilgrastim and US-licensed pegfilgrastim with respect to their physicochemical profile was established using a wide range of rigorous orthogonal analytical techniques. Biological function was compared using receptor binding analyses, in vitro proliferation assays, and in vivo hematopoietic progenitor mobilization. RESULTS: Apobiologix pegfilgrastim and the US-licensed pegfilgrastim reference product were found to be highly similar analytically with respect to molecular mass, primary, secondary and tertiary protein structures, purity, charge, and hydrophobicity. No differences in receptor binding affinity were observed, and all samples demonstrated similar in vitro and in vivo bioactivity. CONCLUSION: These studies provide robust evidence supporting the structural and functional similarity between Apobiologix pegfilgrastim and the US-licensed reference pegfilgrastim, and hence their biosimilarity.

Identification of Low-Level Product-Related Variants in Filgrastim Products Presently Available in Highly Regulated Markets.

BACKGROUND: Filgrastim is a recombinant, non-glycosylated form of human granulocyte colony-stimulating factor, used to stimulate leukocyte proliferation in patients suffering from neutropenia. Since the expiration of patents associated with Amgen's filgrastim biopharmaceutical, Neupogen(®), in 2006, a number of filgrastim products have been marketed; however, a detailed characterization and comparison of variants associated with these products have not been publically reported. OBJECTIVE: The objective of this study was to identify and quantify product-related variants in filgrastim reference products and biosimilars thereof that are presently available in highly regulated markets. METHODS: In this study, we used intact and top-down mass spectrometry to identify and quantify product-related variants in filgrastim products. Mass spectrometry has become the method of choice for physicochemical characterization of biopharmaceuticals, allowing accurate and sensitive characterization of product-related variants. RESULTS: In addition to modifications ubiquitously present in biopharmaceuticals, such as methionine oxidation and asparagine/glutamine deamidation, we identified six different low-level, product-related variants present in some, but not all, of the tested products. Two variants, an acetylated filgrastim variant and a filgrastim variant containing an additional C-terminal tryptophan extension, are newly identified variants. CONCLUSION: This study demonstrates that filgrastim products already in widespread clinical use in highly regulated markets differ in low-level, product-related variants present at levels mostly below 1 % relative abundance. This study provides a comprehensive catalog of minor differences between filgrastim products and suggests that the filgrastim product-related variants described here are not clinically relevant when present at low abundance.