Sensitive and comprehensive analysis of O-glycosylation in biotherapeutics: a case study of novel erythropoiesis stimulating protein

Aim: Glycosylation of recombinant human erythropoietins (rhEPOs) is significantly associated with drug's quality and potency. Thus, comprehensive characterization of glycosylation is vital to assess the biotherapeutic quality and establish the equivalency of biosimilar rhEPOs. However, current glycan analysis mainly focuses on the N-glycans due to the absence of analytical tools to liberate O-glycans with high sensitivity. We developed selective and sensitive method to profile native O-glycans on rhEPOs. Results: O-glycosylation on rhEPO including O-acetylation on a sialic acid was comprehensively characterized. Details such as O-glycan structure and O-acetyl-modification site were obtained from tandem MS. Conclusion: This method may be applied to QC and batch analysis of not only rhEPOs but also other biotherapeutics bearing multiple O-glycosylations.