Purification of common light chain IgG-like bispecific antibodies using highly linear pH gradients

Monovalent bispecific antibodies (BsAbs) are projected to have broad clinical applications due to their ability to bind two different targets simultaneously. Although they can be produced using recombinant technologies, the correct pairing of heavy and light chains is a significant manufacturing problem. Various approaches exploit mutations or linkers to favor the formation of the desired BsAb, but a format using a single common light chain has the advantage that no other modification to the antibody is required. This strategy reduces the number of formed molecules to three (the BsAb and the two parent mAbs), but the separation of the BsAb from the two monovalent parent molecules still poses a potentially difficult purification challenge. Current methods employ ion exchange chromatography and linear salt gradients, but are only successful if the difference in the observed isoelectric points (pIs) of two parent molecules is relatively large. Here, we describe the use of highly linear pH gradients for the facile purification of common light chain BsAbs. The method is effective at separating molecules with differences in pI as little as 0.10, and differing in their sequence by only a single charged amino acid. We also demonstrate that purification resins validated for manufacturing are compatible with this approach.