Investigation of Fill-Finish Tubing Compatibility in the Absence of Protein Stabilizers

Optimization of the fill-finish process for a biotherapeutic is imperative for the highest quality drug product. Fill-finish is the last step in manufacturing and the last opportunity for intervention prior to entry into the supply chain. Typically, stabilizing excipients are utilized to mitigate the chemical or structural weaknesses of a protein therapeutic; however, there are cases in which the route of administration dictates the exclusion of key stabilizing excipients. When this is the case, process-related stabilization techniques need additional investigation. The goal of this work is to provide guidance and highlight key factors impacting enzyme stability in fill-finish processes in the absence of stabilizing excipients. Four tubing interfaces were studied in a recirculation model grouped as either silicone or thermoplastic elastomer. Colloidal stability was found to be the main route of degradation for this enzyme, producing soluble and insoluble aggregate, and various methods were employed to measure and characterize aggregation across a large dynamic size range. The flow imaging data captured high levels of particles that were shed from the thermoplastic elastomer tubing material in the 1-100 µm size range. Size-exclusion chromatography also indicated that the thermoplastic elastomer tubing produced unique multimeric soluble aggregates of the enzyme. Silicone tubing demonstrated superior performance compared to thermoplastic tubing in recirculation models. Silicone tubing produced a very low amount of subvisible particulate shedding with undetectable multimeric aggregate species as well as a better overall visual appearance after recirculation for up to 4 hours. The instability of the enzyme solution was not related to the shear stress in a flow field alone, but rather it was due to the use of an incompatible tubing material in the fill-finish process.