The role of intermolecular interactions on monoclonal antibody filtration through virus removal membranes.

The removal of viruses by filtration is a critical unit operation to ensure the overall safety of monoclonal antibody (mAb) products. Many mAbs show very low filtrate flux during virus removal filtration, although there are still significant uncertainties regarding both the mechanisms and antibody properties that determine the filtration behavior. Experiments were performed with three highly purified mAbs through three different commercial virus filters (Viresolve Pro, Viresolve NFP, and Pegasus SV4) with different pore structures and chemistries. The flux decline observed during mAb filtration was largely reversible, even under conditions where the filtrate flux with the mAb was more than 100-fold smaller than the corresponding buffer flux. The extent of flux decline was highly correlated with the hydrodynamic diameter of the mAb as determined by dynamic light scattering (DLS). The mAb with the lowest filtrate flux for all three membranes showed the largest attractive intermolecular interactions and the greatest hydrophobicity, with the latter determined by binding to a butyl resin in an analytical hydrophobic interaction chromatography (HIC) column. These results strongly suggest that the flux behavior is dominated by reversible self-association of the mAbs, providing important insights into the design of more effective virus filtration processes and in the early identification of problematic mAbs/solution conditions.

Role of membrane structure on the filtrate flux during monoclonal antibody filtration through virus retentive membranes.

Virus removal filtration is a critical step in the manufacture of monoclonal antibody products, providing a robust size-based removal of both enveloped and non-enveloped viruses. Many monoclonal antibodies show very large reductions in filtrate flux during virus filtration, with the mechanisms governing this behavior and its dependence on the properties of the virus filter and antibody remaining largely unknown. Experiments were performed using the highly asymmetric Viresolve® Pro and the relatively homogeneous Pegasus™ SV4 virus filters using a highly purified monoclonal antibody. The filtrate flux for a 4 g/L antibody solution through the Viresolve® Pro decreased by about 10-fold when the filter was oriented with the skin side down but by more than 1000-fold when the asymmetric filter orientation was reversed and used with the skin side up. The very large flux decline observed with the skin side up could be eliminated by placing a large pore size prefilter directly on top of the virus filter; this improvement in filtrate flux was not seen when the prefilter was used inline or as a batch prefiltration step. The increase in flux due to the prefilter was not related to the removal of large protein aggregates or to an alteration in the extent of concentration polarization. Instead, the prefilter appears to transiently disrupt reversible associations of the antibodies caused by strong intermolecular attractions. These results provide important insights into the role of membrane morphology and antibody properties on the filtrate flux during virus filtration.

Industrial application of heat- and mass balance model for fluid-bed granulation for technology transfer and design space exploration.

This work demonstrates the application of state-of-the-art modeling techniques in pharmaceutical manufacturing for fluid bed granulation at varying scales to successfully predict process conditions and ultimately replace experiments during a technology transfer of five products. We describe a mathematical model able to simulate the time-dependent moisture profile in a fluid bed granulation process. The applicability of this model is then demonstrated by calibrating and validating it over a range of operating conditions, manufacturing scales, and formulations. The inherent capability of the moisture profile to serve as a simple, scale-independent surrogate is shown by the large number of successful scale-ups and transfers. A methodology to use this 'digital twin' to systematically explore the effects of uncertainty inherent in the process input and model parameter spaces and their impact on the process outputs is described. Two case studies exemplifying the utilization of the model in industrial practice to assess process robustness are provided. Lastly, a pathway to leverage model results to establish proven acceptable ranges for individual parameters is outlined.