Interplay between the isotherm course and the efficiency of mAb purification in flowthrough and bind-and-elute modes on cation exchange resins.

Separation of a monoclonal antibody (mAb) from impurities was examined on different cation exchange resins (CEX), including POROS XS, POROS HS, NUVIA S, and NUVIA HRS. Impurities mainly consisted of cell culture-derived mAb fragments, or lysozyme, that mimicked the presence of an adsorbing protein of low molecular weight. The choice between the flowthrough mode and the bind-and-elute mode for the purification was guided by the shape of the adsorption isotherm. If the slope of the isotherm chord of mAb was markedly lower than that of the impurities at the loading concentration used, the flowthrough mode performed efficiently. If the opposite held, the use of the bind-and-elute mode was preferable. The existence of an intersection of the isotherm courses indicated the possibility of separation in both flowthrough and bind-and-elute modes in properly selected concentration ranges. For the above reasons, the flowthrough separation of the mAb from its fragments was the most effective for the POROS XS resin, and mAb from LYZ for the NUVIA S resin. Moreover, for the NUVIA S resin, both flowthrough and bind-and-elute modes could be efficiently used for the separation of the mAb from its fragments.