Ion exchange Chromatography Resins For Therapeutic Antibodies (mAbs) Purification

1. Anion-exchange Chromatography Resins

Anion exchange (AEX) is one of the most common methods for the purification of McAb.

Because the isoelectric point of therapeutic monoclonal antibody is usually high, the buffer solution with pH of 7 ~ 7.5 is suitable. The monoclonal antibody molecules do not interact with the anion-exchange chromatographic packings in any way and are often referred to as the "fluid-through mode". Impurities, such as DNA, host cell proteins and Endotoxin, are negatively charged in this Ph range and interact strongly with the anion-exchange packings to remain on the column.

If a buffer with a higher pH is used, the monoclonal antibody can carry enough negative charge to remain on the anion-exchange column, known as the binding mode. However, too high pH has the potential to cause the monoclonal antibody molecules to mutate, so the binding mode is used less often than the flow-through mode. The anion exchange method can also remove virus in flow-through mode, but its disadvantage is that it is not effective to remove McAb and protein A. In the flow-through mode, the DNA and host cell proteins have been largely removed by the protein A affinity chromatography step, which requires the anion exchange chromatography packing to have a strong adsorption capacity for these impurity molecules, but it doesn't require a very high dynamic load. For McAb that can maintain stability at high Ph, the combination mode may be considered.

Weak-partitioning chromatography (WPC) is a new method to refine McAb with a combination mode. In this method, the target monoclonal antibody (McAb) was firstly bound to anion-exchange chromatographic column with suitable pH buffer, and then the McAb was equally eluted by salt solution with certain conductivity. Because the target monoclonal antibody has a higher isoelectric point than all the impurity molecules, the impurity molecules bind more strongly on the anion exchange chromatography column, i. e. , the target monoclonal antibody is eluted first and the impurity molecules are eluted later in the isoelution. It has been reported in the literature that this method can be used as a refining method to improve the flow-through mode of anion exchange chromatography for removing the defects of the McAb molecular polymer and the protein a molecule, at the same time, it maintains the advantage of flow-through mode to remove DNA, host cell protein and endotoxin.

The following table shows the parameters of some anion exchange chromatographic resins.