The virus removal or inactivation capacity of a biopharmaceutical manufacturing process should be proven in a virus validation
study. Virus spike concentration and purity can potentially affect the LRV obtained. Additionally, such a study can affect
the economy of processing. In particular, if the effect of a more concentrated biotherapeutic on virus-validation profile
is minimal, the economy of the filtration can increase. A more robust method can affect economy by maintaining reproducibility
despite process variation. The effects of varying IgG concentration, PPV purity and PPV percentage of spike on the performance
of Planova 20N virus-removal filters were studied. Design of virus clearance studies, as well as safe and economic virus-filter
usage, is considered.
Materials and Methods
Serum or serum-free PPV supernatants were collected, centrifuged at low speed, and 0.45 μm filtered to obtain stock solutions.
For purified PPV, following 0.45 μm filtration, ultracentrifugation and density gradient centrifugation were applied. Serum,
serum-free, and purified PPV solutions were then used for spiking. The spike percentages were 0.5 or 3.0 vol% for serum-free
PPV, 1.0 vol% for serum PPV, and 0.01 vol% for purified PPV. The concentrations of human IgG were 1–30 mg/mL. The non-spiking
or spiked IgG solution were prefiltered by Planova 35N to remove aggregates. Filtration was performed in dead-end mode at
0.8 kgf/cm2 (11.4psi).
The Planova 20N flux was not affected by the PPV purity and was identical in the presence and absence of PPV (data not shown).
Also, the PPV LRV remained >4 over the filtration volume of 200L/m2 under various spiking conditions. In the non-serum PPV spiking (3vol%) case, a high PPV LRV was maintained past 500L /m2 . (Figure 1) Additionally, for all samples tested, the filtration capacity was not affected by virus purity. (Figure 2)
An inaccurate or poorly designed scale-down model can introduce factors that produce incorrect or uninterpretable results
in virus-clearance studies. A higher virus spike percentage can overcome virus-assay limitations; however, this can decrease
the filtration performance if not chosen wisely. We routinely recommend PPV spike percentages at contract laboratories up
to 1% without problem, and XMuLv spike percentages up to 0.5%. Our data shows that purified virus is not a factor under the
Production economy is dictated by the capacities of the materials used to process biotherapeutic material. In particular,
a material that consistently performs over a wide variation in challenge can be said to be robust. In the specific case of
a virus-removal filter, a virus validation can dictate the V/m2 ratio, based on the margin at which a minimal LRV=4 is maintained. Ideally, a robust virus-removal filter will maintain
LRV=4 through a wide concentration range. In the case of MAb's, this range could be 1–5mg/mL to upwards of 20mg/mL, or higher.