Scale-up issues during sterile filtration of glycoconjugate vaccines

Several recent studies have provided important insights into the factors controlling the sterile filtration of glycoconjugate vaccines; however, this work has been limited to small-scale disk filters with very uniform flow distribution. The objective of this study was to examine the scale-up of the sterile filtration step using a glycoconjugate drug substance made from a single polysaccharide serotype. Experimental data were obtained during constant flux filtration through 0.22 μm Durapore® polyvinylidene difluoride (PVDF) membranes, both with small discs and with the Opticap® XL2 pleated cartridge. The transmembrane pressure increased rapidly during the glycoconjugate filtration due to membrane fouling, with the rate of pressure increase being more pronounced in the pleated cartridge. Additional insights into the fouling behavior were obtained using confocal microscopy by in situ labeling of the glycoconjugate captured within the filter media using an Alexa Fluor fluorescent dye. Glycoconjugate deposition occurred only within the first 5-15 μm of the 0.22 μm Durapore® membrane at both scales, with more variability in the deposition pattern observed for the pleated filter due to the non-uniform flow distribution in the Opticap® XL2 cartridge. These results provide important insights into the underlying fouling behavior during sterile filtration of glycoconjugate vaccines as well as a framework for the scale-up of the sterile filter step in glycoconjugate biomanufacturing.