Ion-exchange chromatography (IEC) in downstream processing of bio­pharma­ceuticals is almost exclusively operated in a salt induced elution mode at fixed pH. This is the most widespread approach to remove contaminats and product related impurities during the manufacturing of monoclonal antibodies (mAbs).<br/>Chromatofocusing using externally generated pH gradients represents an interesting alternative providing robust performance and high selectivity. Here, an extended steric mass action (SMA) modeling approach is used based on a manageable number of simple pH gradient elution experiments. Adsorption isotherms were determined in a 96-well format and used for the simulation of elution curves at elevated protein loadings.<br/>The presented model captures salt, as well as pH dependencies of the ion exchange reaction and allows the prediction of pH gradient elution at fixed salt concentration, salt gradient elution at fixed pH or a combination of both salt and pH gradients, so called dual gradients. The impact of mobile phase modifiers such as polyethylene glycol (PEG) can also be described by the model. Furthermore, the method is transferable to mixed mode chromatography. Direct applicability of the model is demonstrated for the separation of a conventional mAb from soluble aggregates, as well as for the purification of a bispecific antibody (bsAb) for IEC and MMC.

Modelling of pH and dual gradient ion exchange and multi modal chromatography for the purification of mAbs

249th National Meeting (2015)

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