Development of an innovative salt-mediated pH gradient cation exchange chromatography method for the characterization of therapeutic antibodies

The successful application of monoclonal antibodies (mAb) in oncology and autoimmune diseases paved the way for the development of therapeutic antibodies with a wider range of structural and physico-chemical properties. A pH-gradient combining 2-(N-morpholino)ethanesulfonic (MES) and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffers and mediated with potassium chloride was developed to sufficiently retain acidic mAbs (pI < 7) in cation exchange chromatography (CEX), while keeping suitable separation performance for basic mAbs (pI > 7). Firstly, the MES and HEPES buffers were individually evaluated in their useful pH range by applying a salt gradient. The performance of a salt-mediated pH gradient combining the MES and HEPES buffers was then compared to a commercial pH gradient kit. The developed conditions were found superior to the salt-gradient approaches and provided a useful alternative to commercial pH gradient kits. In this study, the developed conditions were applied to separate a bispecific antibody (BsAb) from its two parental mAbs.