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Etanercept is a soluble fusion protein of the tumor necrosis factor receptor (TNFR) extracellular domain, linked to an Fc part of IgG1. It possesses three N- and 13 O-glycosylation sites. Due to its complex structure, an analytical challenge is facing the development and approval of biosimilars. In the current study, physicochemical characterization using state-of-the-art analytics was performed to analyze intact and subunit masses, post-translational modifications (PTMs), higher order structure and potency of Etanercept originator Enbrel® and its biosimilar Altebrel™ (AryoGen Pharmed) in accordance to critical quality attributes of biopharmaceuticals. Intact mass and subunit analysis revealed a size of about 126 kDa for both biologicals. Similar glycoprotein species for the complete monomer and the Fc domain of originator and follow-on product were observed, however, small differences in lysine variants and oxidation were found. N-Glycopeptide analysis with UHPLC-QTOF-MSE confirmed the N-glycosylation sites (N149, N171 and N317) as well as Fc-specific glycosylation on N317, and TNFR-specific highly sialylated glycans on N149 and N171 on both investigated products. Small quantitative variations in the N-glycan profile were detected, although the N-glycans were qualitatively similar. Four different O-glycopeptides bearing core 1-type glycans were detected. For both, N- and O-glycopeptide analysis, determination was achieved without prior cleavage of the sialic acid residues for the first time. In addition, ion mobility spectrometry data confirmed close similarity of higher-order structure of both biologics. Furthermore, a neutralization assay, investigating the impact of altered PTMs on potency, indicated that the differences within all batches are still in the acceptable range for biosimilarity.

Immunglobolin G (IgG)-based biopharmaceuticals are emerging on the pharmaceuticals market due to their high target selectivity in different diseases. In parallel, a growing interest by other companies to produce similar or highly similar follow-on biologics exits, once the patent of blockbuster biotherapeutics is about to expire. In correlation to their complex structure, an analytical challenge is facing the approval of these biosimilars. Health authorities (e.g. FDA and EMA) have issued several guidelines to define critical quality attributes during manufacturing process changes. In the current study, physicochemical characterization using state-of-the-art analytics was applied to analyse intact mass, post-translational modifications (PTMs) and higher order structure of Rituximab and one of its biosimilars. Intact mass analysis, middle-up approach as well as subunit analysis revealed similar glycoforms but additional lysine variants in the biosimilar. The N-glycosylation site was confirmed for both, the originator and the biosimilar. PTMs and higher order structure were confirmed to be similar. A special focus was given to N-glycosylation due to its potential to monitor the batch-to-batch consistency and alteration during the production bioprocess. Comparison of the N-glycosylation profiles obtained from three batches of the biosimilar and the reference product showed quantitative variations, although the N-glycans were qualitatively similar. Furthermore, a head-to-head comparability of functional properties was performed to investigate the impact of glycosylation alteration and PTMs on potency within the biosimilar batches and between originator and follow-on biodrug. The data affirm that the difference is still in the acceptable range for biosimilarity.

Biopharmaceuticals are gaining interest in therapy due to their high target selectivity. Most of the recently approved biopharmaceuticals represent drugs that are produced by biotechnological processes involving recombinant DNA. Thus, this review article mainly focusses on protein therapeutics. However analogous considerations also apply for other large molecule therapeutics. As early approved blockbuster biopharmaceuticals run out of patent protection shortly, a growing interest in biosimilar production results in the need of proper analytical characterization and comparison of inventor and biosimilar. In contrast to small molecule drugs small variations in the production process may strongly impact the final biological. Thus, quality assurance of biopharmaceuticals results in much higher analytical effort compared to small molecules. This review gives an overview on analytical methods for characterization of protein biologicals. Classical methods such as gel electrophoresis and liquid chromatography are summarized and complemented with state-of-the-art mass spectrometric investigations. Full molecule investigations of native or denaturized proteins as well as methods including digestion (middle-down and bottom-up) are discussed. Furthermore, literature on glycoprotein analysis using glycopeptide, released glycan and monosaccharide analysis is reviewed.

Eptacog alfa (NovoSeven®) is a vitamin K-dependent recombinant Factor VIIa produced by genetic engineering from baby hamster kidney (BHK) cells as a single peptide chain of 406 residues. After activation, it consists of a light chain (LC) of 152 amino and a heavy chain (HC) of 254 amino acids. Recombinant FVIIa undergoes many post-translational modifications (PTMs). The first ten glutamic acids of the N-terminal moiety are γ-carboxylated, Asn145 and Asn322 are N-glycosylated, and Ser52 and Ser60 are O-glycosylated. A head-to-head biosimilarity study was conducted for the originator and the first biosimilar AryoSeven™ to evaluate comparable bioengineering. Physicochemical properties were analyzed based on mass spectrometry, including intact mass, PTMs and higher-order structure. Both biotherapeutics exhibit a batch-to-batch variability in their N-glycan profiles. N-Glycopeptide analysis with UHPLC- QTOF-MSE confirmed N-glycosylation sites as well as two different O-glycopeptide sites. Ser60 was found to be O-fucosylated and Ser52 had O-glucose or O-glucose-(xylose)1,2 motifs as glycan variants. Ion mobility spectrometry (TWIMS) and NMR spectroscopy data affirm close similarity of the higher-order structure of both biologicals. Potency of the biodrugs was analyzed by a coagulation assay demonstrating comparable bioactivity. Consequently, careful process optimization led to a stable production process of the biopharmaceuticals.