A U.S. Patent for a “Method to Improve Virus Filtration Capacity” was awarded to Genentech on May 26th, 2020. The present invention is a method of virus filtration comprising subjecting a composition comprising a recombinant protein produced in a mammalian host cell and having or suspected of having a parvovirus contaminant to a virus filtration process comprising a cation exchange step and an endotoxin removal step, simultaneously or in either order, immediately preceding a virus filter capable of removing a parvovirus, and wherein said virus filter’s filtration capacity in kg/m.sup.2 is improved between 1.5 to 20 fold… Learn More