Quantitative characterization of intact sialylated O-glycans with MALDI-MS for protein biotherapeutics

For validating O-glycosylation of protein biotherapeutics, we presented a quantitative O-glycomics method which is based on the neutralization of sialic acids, the specific release of O-glycans, and the introduction of permanent positive charge followed by quantitative MALDI-MS analysis. This method shows excellent technical reproducibility, linearity and sensitivity. In addition, it enables the quantification of intact O-glycans with minimal degradation or loss of sialic acids on these glycans compared to a conventional HPLC-based method. We then applied this method to quantitatively characterize O-glycans present on Etanercept. The analysis showed the relative abundances of mono- and di-sialylated core 1 O-glycans - were 79.3±0.8% and 17.3±1.4%, respectively. This glycomics technology could allow for the reliable quantitative analysis of intact O-glycans from glycoproteins and may contribute to validation of O-glycosylation protein biotherapeutics in the pharmaceutical industry.