title: Limitations of polyethylene glycol-induced precipitation as predictive tool for protein solubility during formulation development.
abstract: OBJECTIVE
  Polyethylene glycol (PEG)-induced protein precipitation is often used to extrapolate apparent protein solubility at specific formulation compositions. The procedure was used for several fields of application such as protein crystal growth but also protein formulation development. Nevertheless, most studies focused on applicability in protein crystal growth. In contrast, this study focuses on applicability of PEG-induced precipitation during high-concentration protein formulation development.
  
  
  METHODS
  In this study, solubility of three different model proteins was investigated over a broad range of pH. Solubility values predicted by PEG-induced precipitation were compared to real solubility behaviour determined by either turbidity or content measurements.
  
  
  RESULTS
  Predicted solubility by PEG-induced precipitation was confirmed for an Fc fusion protein and a monoclonal antibody. In contrast, PEG-induced precipitation failed to predict solubility of a single-domain antibody construct. Applicability of PEG-induced precipitation as indicator of protein solubility during formulation development was found to be not valid for one of three model molecules.
  
  
  CONCLUSIONS
  Under certain conditions, PEG-induced protein precipitation is not valid for prediction of real protein solubility behaviour. The procedure should be used carefully as tool for formulation development, and the results obtained should be validated by additional investigations.
authors.affiliation: Division of Pharmaceutics, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.|Merck KGaA, Darmstadt, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Hofmann
authors.affiliation: Merck KGaA, Darmstadt, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Winzer
authors.affiliation: Merck KGaA, Darmstadt, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Weber
authors.affiliation: GILYOS GmbH, Würzburg, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Gieseler
mesh_terms: D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000737:chemistry*; D011232:Chemical Precipitation; D002626:Chemistry, Pharmaceutical / Q000379:methods*; D003460:Crystallization; D015195:Drug Design; D006863:Hydrogen-Ion Concentration; D011092:Polyethylene Glycols / Q000737:chemistry*; D011506:Proteins / Q000008:administration & dosage / Q000737:chemistry*; D012995:Solubility
chemical_list: D000911:Antibodies, Monoclonal; D011506:Proteins; D011092:Polyethylene Glycols
keywords: formulation development; high-concentration protein formulations; polyethylene glycol; protein solubility