Use of Water Proton NMR to Characterize Protein Aggregates: Gauging the Response and Sensitivity

Water proton transverse relaxation rate R₂(¹H₂O) measurements by NMR stand out as a powerful noninvasive tool to detect protein aggregates, including subvisible particles in biopharmaceutical formulations. To understand the applicability of water proton NMR ( wNMR), we studied the response and sensitivity of wNMR to the aggregates of a monoclonal antibody (mAb) within a wide size range at different aggregate levels, for three different physical stresses: freeze-thaw cycling, heating, and agitation. We compared the sensitivity and response of wNMR with those observed by conventional techniques of size exclusion chromatography (SEC), microflow imaging (MFI), and dynamic light scattering (DLS). Our findings showed that wNMR detects mAb aggregates within wide aggregate levels and in a wide range of aggregate sizes. wNMR was sensitive to an increase in soluble protein aggregates in the range of <1.0%. In most cases, wNMR demonstrated linear response toward the aggregate fraction. Nonlinearity of such response potentially points to the presence of larger size aggregates that possibly rearrange and/or dissociate upon dilution. The results demonstrate the potential of wNMR as a quantitative and noninvasive analytical tool for characterizing protein aggregates in biopharmaceutical formulations.