Purification Method for Bispecific antigen-binding Polypeptides with Enhanced Protein L Capture Dynamic Binding Capacity

The present invention provides a downstream purification method process for the production of bispecific antigen-binding polypeptides. The method comprises at least the steps of (i) providing a separation resin comprising a polymer matrix part and a ligand part, wherein the matrix part comprises polymethacrylate and has a particle size of about 30 to 60 pm, wherein the ligand part comprises recombinant protein L, and wherein the ligand part's protein L is covalently bound to the matrix part's particles, (ii) contacting a process fluid comprising the bispecific antigen-binding polypeptide with the separation resin, (iii) capturing the bispecific antigen-binding polypeptide by the ligand part of the separation resin, wherein the bispecific antigen-binding polypeptide reversibly binds to the ligand part of the separation resin, and wherein the remainder of the process fluid does not bind to the ligand part of the separation resin, (iv) washing the bound bispecific antigen-binding polypeptide with a wash buffer which does not elute the bispecific antigen-binding polypeptide from the ligand portion, and (v) elute the bispecific antigen-binding polypeptide from the ligand part with an elution buffer at a low pH.