Combined polyethylene glycol and CaCl sub(2) precipitation for the capture and purification of recombinant antibodies

A direct capture step was developed for the purification of recombinant antibodies from clarified culture supernatants. This method is a combination of CaCl sub(2) and polyethylene glycol (PEG) precipitation. For separation of high molecular weight impurities, such as dsDNA and aggregates, CaCl sub(2) precipitation was the method of choice, and PEG precipitation was used for monoclonal antibody (mAb) capturing to separate low molecular weight impurities, mainly host cell proteins (HCP). Precipitation tests were performed with five different CHO cell culture supernatants, and showed yields of at least 80-95%. Purity was determined by size exclusion chromatography, HCP ELISA, and two-dimensional differential in-gel electrophoresis (2D DICE); the measured values from CaCl sub(2)/PEG precipitation were comparable to those from Protein A purification. These results suggest that this novel purification method could be used as the basis for a platform process to capture antibodies from a clarified culture supernatant. CaCl sub(2)/PEG precipitation provides enough selectivity and recovery to substantiate replacing the Staphylococcus Protein A affinity chromatography step of the antibody purification process.