Hybrid Mass Spectrometry Methods Reveal Lot-to-Lot Differences and Delineate the Effects of Glycosylation on the Structure of Herceptin®
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To consider the measurable variations in biopharmaceuticals we use mass spectrometry and systematically evaluate three lots of Herceptin®, two mAb standards and an intact Fc-hinge fragment. Each mAb is examined in three states; glycan intact, truncated (following endoS2 treatment) and fully deglycosylated. Despite equivalence at the protein level, each lot of Herceptin® gives a distinctive signature in three different mass spectrometry analyses. Ion mobility mass spectrometry (IM-MS) shows that in the API, the attached N-glycans reduce the conformational spread of each mAb by 10.5 – 25 %. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) data supports this, with lower global deuterium uptake in solution when comparing intact to the fully deglycosylated protein. HDX-MS and activated IM-MS map the influence of glycans on the mAb and reveal allosteric effects which extend far beyond the Fc domains into the Fab region. Taken together these findings, and the supplied interactive data sets could be used to provide acceptance criteria with application for MS based characterisation of biosimilars and novel therapeutic mAbs.