(665g) Assessment of the Impact of Interfacial and Shear Stress on Biologics Drug Product Via Mini-Piloting Tools

During biologics development, processes such as membrane filtration, filling, and mixing are critical in the drug product manufacturing. However, these processes, as well as turbulent flow conditions, and multiple passes through pumps, valves and “pinch” points; impose various stresses on the protein. These stresses can lead to protein instability. Shear, cavitation, and interfacial stress are often attributed as the main causes of protein unfolding and aggregation.

Proper risk analysis needs to be in place to understand the susceptibility of the protein to unfold and aggregate in presence of interfacial and shear stress. There are certain techniques, such as agitation/shaking studies that have been traditionally used to understand the impact of these stresses on the protein physical stability. However, the stresses applied in these systems are convoluted, making it difficult to define the control strategy, (i.e. adjustment in process parameters to reduce foaming/bubble formation, etc.). In this study, we have developed two mini-piloting tools that allow for the isolation of interfacial and shear stress respectively. The interfacial stress is applied to the sample by generating uniform bubbles when recirculating air from the headspace of the vial in a closed loop. The bubbles generated are passed through the solution for finite periods of time. For the shear stress, an estimation of the shear rates present during processing is made by fundamental transport relations and CFD modeling. The small scale shear stress tool simulates the shear experienced by the protein during processing, using a small-scale high pressure pump connected to a fine stainless steel tubing.

These systems help simulate the normal operating ranges as well as proven acceptable ranges for unit operation such as TFF, mixing and filling. Different protein formulations were subjected to controlled interfacial and shear stresses. The quality attributes evaluated after the stress were focused on size variant (particulate matter and HMW species), which is most likely the mechanism associated with interfacial and shear stress. It was possible to identify the susceptibility of the protein to aggregate depending of the stress that was applied. In addition, these tools contributed in formulation screening by evaluating which formulation would better mitigate the impact of the imposed stress.

During development, it is important to identify the protein formulations that have a tendency to aggregate in order to implement appropriate risk mitigation strategies. And also, to have scale down models to validate the design space for the process parameters of key unit operations.