Unraveling the Effects of Filtration, Process Interruptions, and Post-Process Agitation on Protein Aggregation

Filtration is an essential process step for the manufacturing and filling of biopharmaceuticals. In filling operations, sterile filtration is typically achieved through dead-end filtration using fine membrane filters that completely retain colony-forming units per square centimeter of filter area. According to FDA and USP guidelines, sterilizing filters must be product-compatible and composed of non-fiber releasing materials, typically with a absolute pore size rating of 0.22 µm. However, it has been observed that protein interaction with filters and particle shedding from filter materials, can contribute to protein aggregation when exposed to routine stresses such as agitation during manufacturing, handling, storage or transportation. Since aggregates can cause severe immune responses upon parenteral application, it is crucial to understand the possible effects of various filter materials during different manufacturing and filling set-ups in order to choose the most suitable filter types and filtration processes. To address this, we investigated particle formation on the visible, subvisible and submicron scales as well as structural changes in a specific liquid glycoprotein (GP) formulation after constant and impulse filtration (i.e., stop and go mechanisms to assess possible film formation and film disruption on the filter material) with commonly used hydrophilic membrane materials, i.e., polyvinylidene fluoride (PVDF), polyether sulfone (PES), and cellulose acetate (CA) with a pore size of 0.22 microm. In addition, we exposed the material to stirring and heating to induce aggregation and investigate the filter performances in the case of initially high particle content.