Effectiveness of host cell protein removal during depth filtration – Effect of filter chemistry
Abstract
Recent advancements in upstream processing (USP) of monoclonal antibodies (mAbs) have increased the load on downstream processing (DSP). The increased cell density of the product stream leaving the bioreactor means a higher concentration of contaminants associated with the production of mAbs. One such example is host cell proteins (HCPs), impurities that can create challenges for the operation of protein A affinity chromatography and hydrophobic interaction chromatography used for mAb purification. Recent studies have shown that depth filters can bind many of these small impurities, decreasing the load on subsequent filters and chromatography columns. This study aimed to examine the binding characteristics of two commercial depth filters to understand the relationship between a depth filter’s chemical composition and its ability to remove HCPs. Two depth filters with comparable pore sizes, each made from different filter media, were tested using a series of model proteins. The model proteins were chosen to match the range of typical HCPs based on their isoelectric points (pI), molecular weights, and hydrophobicities. These model proteins were. The X0SP filter, which has polyacrylic fibers and a synthetic silica filter aid, showed a higher binding capacity for α-chymotrypsin, conalbumin, and myoglobin than the X0HC filter, which has cellulose fibers and diatomaceous earth as the filter aid. The X0SP filter is particularly well suited for removing positively charged HCPs with binding capacities of more than 600 g/m2 at low conductivity. These results provide important insights into the performance characteristics and proper selection of depth filters for the purification of monoclonal antibodies.
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Alezz