Mass Spectrometry Characterization of Higher Order Structural Changes Associated with the Fc-glycan Structure of the NISTmAb Reference Material, RM 8761.

As monoclonal antibodies (mAbs) rapidly emerge as a dominant class of therapeutics, so does the need for suitable analytical technologies to monitor for changes in protein higher order structure (HOS) of these biomolecules. Reference materials (RM) serve a key analytical purpose of benchmarking the suitability and robustness of both established and emerging analytical procedures for both drug producers and regulators. Here, two simple enzymatic protocols for generating Fc-glycan variants from the NISTmAb RM are described and both global and localized changes in HOS between the RM and these Fc-glycan variants are characterized using hydrogen deuterium exchange-mass spectrometry (HDX-MS) and ion mobility spectrometry-mass spectrometry (IMS-MS) measurements. An alternative statistical approach is described where measurement thresholds that differentiate between measurement variability and significant structural changes were established on the basis of experimental data. Measurements revealed decreases in structural stability correlating with the degree of Fc-glycan structure loss, especially at the C2/C3 domain interface. These data promote the use of this RM and these Fc-glycan variants for establishing the sensitivity of and validating analytical methods for the detection of HOS measurements of mAbs.