Techniques for characterization of solid-phase preparations of biotherapeutics, especially monoclonal antibody (mAb) based modalities, are increasing in demand. In particular, methods that readily inform on structure and stability could prove transformative in the arena of solid-phase formulation development. Solution-state NMR has proven to be a robust and reproducible method for characterizing the higher order structure (HOS) of aqueous formulations of biotherapeutics. Similarly, solid-state NMR (ssNMR) has the potential to serve as a premier tool for solid-phase HOS characterization. By interrogating nuclear dipole-dipole interactions, which are sensitive to inter nuclear distance and orientation, ssNMR can report directly on HOS. Here we demonstrate the proof-of-concept for using ssNMR 1H-13C cross polarization (hC-CP) buildup as a means to characterize lyophilized mAb formulations. Employing NISTmAb as model system, we describe how hC-CP buildup can differentiate between lyophilized protein forms. Using Principal Component Analysis (PCA), we show that hC-CP data cluster by formulation type and resultant loading spectra reveal the regions in the mAb that vary as a function of sample differences. Results from this study support the use of ssNMR as a means for HOS characterization of solid-phase preparations of mAbs and other protein therapeutics and further illustrates the encompassing utility of NMR in the biopharmaceutical industry.
