The
glycosylation of biologics is an important factor in pharmacological
functions such as efficacy, safety, and biological activity and is
easily affected by subtle changes in the cellular environment. Hence,
comprehensive and in-depth glycomic characterization of biological
products should be performed to ensure product quality and process
consistency prior to regulatory approval, but it is still highly challenging
due to glycan microheterogeneity produced by enzymatic machinery.
In this study, we have developed a systematic methodology for the
separation and characterization of various glycans of biotherapeutics
using the combination of solid-phase extraction (SPE) and high resolution
LC/MS. Neutral and multiple-acidic glycans were selectively fractionated
by SPE with a porous graphitized carbon (PGC) cartridge according
to their molecule size and polarity (acidity, pK
a). Subsequent LC-MS and -MS/MS analyses enabled us to obtain
glycan compositions, structures, and quantitative information. Indeed,
we have successfully performed glycomic characterization of agalsidase-beta,
a representative therapeutic enzyme containing both phosphorylated
and sialylated glycans. In addition, a comparative analysis of functional
glycans released from different batches of enzymes was performed to
verify our method. These results suggest that stepwise PGC-SPE and
LC/MS/MS pairwise assays can be used as an efficient tool to detect
glycosylation changes of therapeutic glycoproteins including abundant
acidic species in biologics or biosimilar development.