Method to improve virus filtration capacity

What is this patent about?

’237 is related to the field of protein purification, specifically addressing the challenges of removing viral contaminants from recombinant protein therapeutics. In the production of biologics using mammalian cell lines, ensuring the removal of endogenous and adventitious viruses is a critical safety requirement. While size-exclusion virus filtration is a robust method for clearing small pathogens like parvoviruses, these high-selectivity membranes are highly susceptible to fouling by trace impurities, which significantly limits their processing capacity and increases manufacturing costs.

The underlying idea behind ’237 is that the premature clogging of parvovirus filters is caused by multiple distinct classes of foulants that cannot be addressed by a single prefiltration mechanism. While prior approaches focused on using either depth filters or cation-exchange media to capture protein aggregates, the inventors discovered a synergistic effect when combining cation-exchange and endotoxin removal steps. By targeting different physicochemical species simultaneously, this dual-action prefiltration train prevents the adsorption of diverse impurities onto the virus filter’s pore walls, maintaining high flux and throughput.

The claims of ’237 focus on a method for enhancing the capacity of a virus filter by implementing both a cation exchange step and an endotoxin removal step immediately before the filtration of a recombinant protein. This specific sequence or combination is designed to treat compositions produced in mammalian host cells that may contain parvovirus contaminants. The independent claims require that this combined prefiltration approach achieves a 1.5 to 20-fold increase in the filter’s mass capacity (kg/m²) compared to using no prefiltration or either individual step alone.

In practice, the invention is implemented by passing a chromatography pool—such as a monoclonal antibody stream—through a filtration train where the two media act as protective barriers for the final 20 nm parvovirus filter. The implementation utilizes membrane adsorbers for both the cation exchange and endotoxin removal functions, which can be arranged in either order or housed within a single module. This setup allows for continuous processing across a wide pH range (4 to 10) and varying protein concentrations, ensuring that the fine retentive layer of the virus filter remains unobstructed by the complex impurity profile of the feedstock.

This approach differentiates itself from prior art by moving away from natural depth filters, which often suffer from lot-to-lot variability and the risk of leaching metals or beta-glycans into the purified product. Unlike methods that rely solely on negatively charged adsorbers to catch aggregates, this invention recognizes that endotoxin removal media—typically featuring positively charged surfaces or affinity ligands—capture a separate class of foulants. By addressing these multiple fouling pathways, the method provides a more robust and scalable solution for high-titer antibody manufacturing without the drawbacks of traditional clarification media.