(336i) Effect of Aggregates On the Viral Filtration Performance of Monoclonal Antibodies

Current regulatory expectations necessitate the use of multiple orthogonal steps for viral inactivation and removal in the purification of monoclonal antibodies (MAb) from mammalian cell culture. The use of viral filtration (VF) is a primary component of virus clearance to remove both small and large viruses. Typical small viruses have a diameter of ~18?26 nm, whereas a typical monoclonal IgG antibody has a hydrodynamic diameter of ~8?12 nm. To achieve >4 log10 retention of the viruses and >99% recovery of the protein, viral filters are required to have a very narrow pore size distribution. Due to the small size of the pores, VF membranes are generally sensitive to the presence of impurities in the feed solution and can be prone to fouling. Typically the VF occurs downstream of the polishing chromatography steps, so the feed has high purity, however MAb -Mab interactions, such as aggregation could be a concern for VF performance. This paper will present a case study to show how the performance of this step is sensitive to the levels and types of MAb aggregates. One antibody was studied, focusing on the flux as a function of aggregate level and other operational conditions. These parameters were MAb concentration, pH, pressure, buffer composition and filtration mode using a regenerated cellulose hollow fiber membrane. The effect on viral clearance as a function of aggregate level was also investigated. The impact of level and type of MAb aggregate will be presented, along with a description of the fouling mechanism based on traditional models.