Endotoxin removal by virus filters

Endotoxins pose a significant risk to drug product safety due to their potent pyrogenic activity. However, developing a universal decontamination method for protein solutions remains challenging, as current technologies struggle to reconcile efficient endotoxin removal with high product recovery and operational simplicity. This study explores the novel application of commercial virus filters for endotoxin clearance. We systematically evaluated filters from multiple manufacturers across a range of initial endotoxin concentrations and buffer conditions. The results demonstrate that Planova BioEX and Valpha PES virus filters reduced endotoxin levels by 88%-99% at initial endotoxin concentrations below 5 EU/mg of a therapeutic monoclonal antibody, while achieving near-complete protein recovery (>95%). A comparative study revealed that under low pH conditions (pH 5.5), virus filters outperformed Mustang E and Mustang Q membranes in removing low levels of endotoxin. Under high pH conditions (pH 7.5), their performance was comparable. This difference likely stems from distinct removal mechanisms: Mustang membranes rely on electrostatic interactions, whereas virus filters (~20 nm pore size) operate via size exclusion. Dynamic light scattering results indicated the majority of the mAb-endotoxin complexes exceeded 20 nm, supporting the size-based removal mechanism of virus filters. These findings demonstrate that virus filtration has the potential to serve as a viable alternative for endotoxin removal in preclinical protein processing, particularly for high-pH sensitive proteins and acidic proteins. It also represents a valuable addition to the endotoxin clearance toolbox for clinical manufacturing.