Liquid formulations for stabilizing IgMs during physical stress and long-term storage.

To develop a liquid formulation for IgMs to survive physical stress and storage. Stabilizing formulations for 8 monoclonal immunoglobulin (IgMs) were found using differential scanning calorimetry (DSC). In these formulations, the IgMs were subjected to stress and storage and analyzed by size exclusion chromatography and fluorescence activated cell sorting. Structure was analyzed using small-angle X-ray scattering (SAXS). The highest conformational stability was found near the isoelectric point and further enhanced by addition of sorbitol, sucrose and glycine. For 2 IgMs, the pH optimum for conformational and storage stability did not correspond. Lowering the pH led to the desired storage stability. Optimized formulations prevented aggregation and fragmentation from shear stress, freeze-thaw cycles, accelerated storage and real time storage at 4°C and -20°C for 12 months. Optimized formulations also preserved immunoreactivity for 12 months. SAXS indicated that IgM in stabilizing conditions was closer to the structural IgM model (2RCJ) and less susceptible for aggregation. A long-term stabilizing formulation for 8 IgMs was found comprising 20% sorbitol and 1 M glycine at pH 5.0-5.5 which may have broad utility for other IgMs. Formulation development using DSC and accelerated storage was evaluated in this study and may be used for other proteins.