Impact of virus-antibody interactions on viral clearance in anion exchange chromatography

Viral clearance is an important performance metric for the downstream process of monoclonal antibodies (mAbs) due to its impact on patient safety. Anion exchange chromatography (AEX) has been well-accepted in the industry as one of the workhorse techniques for removing viruses, and is considered to be able to achieve high log clearance values under most operating conditions. However, it is not uncommon for viral clearance results on AEX to fall below the desired level despite operating under conditions that should achieve high clearance levels according to conventional wisdom of how this mode of chromatography operates. In this study, a design of experiment (DoE) approach was used to develop a more fundamental understanding of viral clearance during AEX chromatography using Minute Virus of Mice (MVM) on POROS HQ resin. Load pH, conductivity and virus concentration were evaluated as design factors for three mAbs with varying physical and chemical properties. The hydrophobicity and surface charge distributions of the molecules were found to be the most significant factors in influencing viral clearance performance, and the viral clearance trends did not seem to fit with conventional wisdom. To explain this seemingly unconventional behavior, we propose a new mechanism that suggests that interactions between the mAb and the virus have a major contribution on retention of the virus on the resin. This furthered understanding may help improve the predictability, performance and robustness of viral clearance during AEX chromatography.