In downstream purification of monoclonal antibodies (MAbs), the single greatest contributor to manufacturing costs is the expensive capture step typically based on protein A affinity chromatography. Almost since its introduction to bioprocessing, efforts have been made to reduce the cost of this step. Several alternative ligands have been promulgated as potential replacements for protein A, but they have proven difficult to adopt and scale up. Supplier companies have pushed for increases in capacity and economics, but those are always accompanied…