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ObjectivesInfliximab, trastuzumab and bevacizumab are among the most frequently prescribed therapeutic proteins, and like most other therapeutic proteins, are glycosylated. As differences in glycosylation may significantly change the safety and efficacy of therapeutic glycoproteins, it is extremely important to control N-glycosylation consistency. In the first part of this study, the batch-to-batch consistency of the N-glycosylation of infliximab, trastuzumab and bevacizumab was analysed. In the second part, the consistency of the N-glycosylation of bevacizumab stored in polycarbonate syringes (for off-label drug use) for 3 months was examined.MethodsN-glycans were (i) enzymatically released using peptide-N-glycosidase F, (ii) reduced, and (iii) analysed using hydrophilic interaction liquid chromatography coupled with high-resolution mass spectrometry. Mass spectrometry data were interpreted using principal component analysis combined with two-way analysis of variance and Tukey post hoc tests. The biological activity of infliximab and trastuzumab was examined using enzyme-linked immunosorbent assays.ResultsThe results of both studies make important contributions to the field of hospital pharmacy. All batches of the studied therapeutic glycoproteins (infliximab, trastuzumab and bevacizumab) varied considerably (especially in galactosylation), while the N-glycosylation of bevacizumab remained unchanged during 3-month storage.ConclusionsThreshold values for batch-to-batch N-glycosylation variations should be established and batch-to-batch glycosylation consistency should be regularly tested. In our study, samples with significantly different N-glycosylation profiles showed no significant variations in biological activity, suggesting that the differences are probably not therapeutically significant.

Therapeutic proteins are among the top selling drugs in the pharmaceutical industry. More than 60 % of the approved therapeutic proteins are glycosylated. Nowadays, it is well accepted that changes in glycosylation may affect the safety and the efficacy of the therapeutic proteins. For this reason, it is important to characterize both the protein and the glycan structures. In this study, analytical and data processing methods were developed ensuring an easier characterization of glycoprofiles. N-glycans were (i) enzymatically released using peptide-N-glycosidase F (PNGase F), (ii) reduced, and (iii) analyzed by hydrophilic interaction liquid chromatography coupled to a high-resolution mass spectrometer (HILIC-HRMS). Glycosylation changes were analyzed in human plasma immunoglobulin G samples which had previously been artificially modified by adding other glycoproteins (such as ribonuclease B and fetuin) or by digesting with enzyme (neuraminidase). Principal component analysis (PCA) and classification through soft independent modelling by class analogy (SIMCA) were used to detect minor glycosylation changes. Using HILIC-MS-PCA/SIMCA approach, it was possible to detect small changes in N-glycosylation, which had not been detected directly from the extracted-ion chromatograms, which is current technique to detect N-glycosylation changes in batch-to-batch analysis. The HILIC-MS-PCA/SIMCA approach is highly sensitive approach due to the sensitivity of MS and appropriate data processing approaches. It could help in assessing the changes in glycosylation, controlling batch-to-batch consistency, and establishing acceptance limits according to the glycosylation changes, ensuring safety and efficacy. Graphical abstract N-glycosylation characterization using LC-MS-PCA approach.