Application of a High-Throughput Screening Procedure with PEG-Induced Precipitation to Compare Relative Protein Solubility During Formulation Development with IgG1 Monoclonal Antibodies

Protein solubility is a critical attribute in monoclonal antibody (mAb) formulation development as insolubility issues can negatively impact drug stability, activity, bioavailability, and immunogenicity. A high-throughput adaptation of an experimental method previously established in the literature to determine apparent protein solubility is described, where polyethylene glycol (PEG) is used to reduce protein solubility in a quantitatively definable manner. Utilizing an automated, high-throughput system, an immunoglobulin G (IgG)1 mAb in a variety of buffer conditions was exposed to increasing concentrations of PEG and the amount of protein remaining in solution was determined. Comparisons of PEGmidpt values (the weight% PEG in solution required to decrease the protein concentration by 50%) to extrapolated values of apparent protein solubility (in the absence of PEG) were performed. The determination of PEGmidpt by using sigmoidal curve fitting of the entire data set was shown to be the most precise and reproducible approach for use during high-throughput screening experiments. The high-throughput PEG methodology was then applied to the screening of different formulations to optimize relative protein solubility profiles (weight% PEG vs. protein concentration and their corresponding PEGmidpt values) in terms of solution pH and buffer ions for both human and chimeric IgG1 mAbs. Other comparisons included evaluating relative solubility profiles of an IgG1 mAb produced from different cell lines (Chinese hamster ovary vs. murine) as well as for different IgG1 mAbs (produced from the same cell line) in a series of formulation buffers. Based on these comparisons, it was concluded that rapid, high-throughput determinations of relative protein solubility profiles can be used as a practical, experimental tool to compare mAb preparations and to rank order buffer and pH conditions during formulation development.