Solutions for Purification of Fc-fusion Proteins
By Douglas W. Rea, Michiel E. Ultee, Sharon X. Chen, Thomas P. Loisel
Platform processes are valuable tools in process development. Applying them to complex fusion molecules made up of different structures, however, can lead to unexpected results. EA2 is a unique engineered molecule, and it did not fit well into a platform process. It does, however, have three potential affinity and pseudo-affinity sites, each target site having a platform purification unit operation. One site is the antibody Fc region for Protein A binding, but the product was too sensitive to low pHs for typical Protein A elution conditions, so a high pH elution process was developed instead. The other two pseudo-affinity sites proved to be unusable, as did ion exchange chromatography. The final process that was developed added hydrophobic interaction and mixed mode (HIC and AEX) chromatography polishing, with a solvent and detergent (S/D) treatment instead of the typical lowpH virus inactivation.This product points out the need for innovation and flexibility in cases where platforms do not work.