Direct Affinity Purification of Long‐Acting PASylated Proteins with Therapeutic Potential Using L‐Prolinamide for Mild Elution

Both insufficient plasma half‐life (circulation for only few hours or less) and laborious downstream purification can be bottleneck for biological drug development. We report a novel strategy for the efficient and gentle affinity purification of pharmacologically relevant proteins modified by PASylation for prolonged action in vivo. We previously described antibodies specific for Pro/Ala‐rich sequences (PAS) covering a range of binding characteristics. Our present approach relies on a chromatography matrix functionalized with a low‐affinity PAS‐specific antibody Fab fragment for specific adsorption of the PASylated protein from a macromolecular mixture. With the complete absence of hydrophobic/aromatic or ionic groups in the PAS sequence epitope, binding is mediated by Van der Waals contacts and distinct hydrogen bonds only. Surprisingly, selective competitive elution is achieved by application of the highly soluble and biologically inactive imino acid derivative L‐prolinamide. Based on the specific but strongly dynamic biomolecular interaction, our procedure allows the direct one‐step purification of PASylated proteins from a cell extract or culture supernatant while avoiding harsh elution conditions as they are often needed for conventional affinity chromatography.