Impact of Ethylene Oxide Sterilization of Polymer-Based Prefilled Syringes on Chemical Degradation of a Model Therapeutic Protein During Storage

Materials from prefilled syringe systems-such as silicone oil, tungsten, glass, and rubber-may enhance therapeutic protein aggregation and particle formation. Also, the sterilization method used for syringes may impact aggregation and chemical degradation of biologics during storage. Syringes are generally sterilized by radiation, ethylene oxide gas (EO), or steam. Among the sterilization methods, EO has the potential to cause chemical degradation by the formation of adducts with susceptible amino acid residues in the protein. In this study, EO- and steam-sterilized syringes were compared to determine the influence of residual EO on human serum albumin (HSA) degradation. Although the amount of residual EO in the EO-sterilized syringes was less than 220 μg/syringe, well below the International Organization for Standardization limit, EO adduction to cysteine (Cys) and methionine (Met) in HSA was observed by liquid chromatography and mass spectrometry analysis. The EO adduct ratio of HSA stored for 2 weeks in EO-sterilized syringes was about 45%. In contrast, no chemical degradation was observed in HSA formulation stored in steam-sterilized syringes. Because of the propensity of EO to readily form adducts with proteins, an alternative to EO sterilization should be used for prefilled syringes that will be used for therapeutic protein products.