Filtration of a multi-serotype glycoconjugate vaccine drug product through sterilizing grade 0.2/0.22 µm pore size filters.

Glycoconjugate vaccines containing multiple serotypes of a bacterial capsular polysaccharide can provide strong immune protection against pathogenic infections. Sterile filtration is an important component of the fill and finish operations in the preparation of these vaccines, with the capacity of the sterile filter limited by membrane fouling. The objective of this study was to examine the performance of a range of commercial 0.2/0.22 µm nominal pore size sterilizing grade filters with both single-layer and dual-layer structures during filtration of a glycoconjugate vaccine drug product consisting of four polysaccharide serotypes. The highly asymmetric Millipore Express showed much higher capacity than the more homogeneous filters, with the support structure of the Express acting as a prefilter that was able to remove foulants thereby protecting the small pores in the size-selective skin layer. This behavior was confirmed by performing experiments with different batch prefilters and by examining the location of foulant deposition within the sterile filters using confocal microscopy. These results provide important insights into the factors controlling fouling by these multiserotype vaccines as well as a framework for increasing the capacity of the sterile filter.

Sterile filtration of a multi-serotype glycoconjugate vaccine drug product.

Glycoconjugate vaccines consisting of multiple serotypes of the bacterial capsular polysaccharide can provide strong protection against infection by significant pathogens. Previous studies of the sterile filtration behavior of these glycoconjugates have been limited to experiments with individual serotypes even though the formulated vaccines contain several different serotypes to provide broad immunization. The objective of this study was to explore the fouling behavior of a glycoconjugate vaccine drug product consisting of four different polysaccharide serotypes. Sterile filtration data were obtained with 0.22 µm Durapore® membranes at both constant flux and constant pressure for both the individual serotypes and the drug product containing multiple serotypes. Fouled membranes were examined by confocal microscopy, demonstrating that all four serotypes deposit in a narrow band near the filter inlet. The different ionic composition of the formulation buffer (compared to the buffers used with the drug substance) had a large effect on the fouling behavior. In addition, the fouling resistance associated with the drug product was greater than the sum of the resistances of the individual serotypes. These results provide important insights into the sterile filtration behavior of these multivalent glycoconjugate vaccines.

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.

Prefiltration enhances performance of sterile filtration for glycoconjugate vaccines.

Recent studies have reported very low capacity during sterile filtration of glycoconjugate vaccines due to rapid fouling of the sterile filter. The objective of this study was to explore the potential for significantly increasing the capacity of the sterile filter through the use of an appropriate prefilter. Data were obtained using prefilters with different pore size and chemistry, with the sterile filtration performed at constant filtrate flux using 0.22 µm nominal pore size Durapore® polyvinylidene difluoride membranes. Prefiltration through 5 µm pore size Durapore® or Nylon prefilters nearly eliminated the fouling of the sterile filter, leading to more than a 100-fold reduction in the rate of pressure increase for the sterile filter. This dramatic improvement in sterile filter performance was due to the removal of large components (greater than 1 µm in size) as confirmed by dynamic light scattering. These results demonstrate the potential of using large pore size prefilters to significantly enhance the performance of the sterile filtration process for the production of important glycoconjugate vaccines.