Silicone oil is often used to decrease glide forces in prefilled syringes and cartridges, common primary container closures for biopharmaceutical products. Silicone oil has been linked to inducing protein aggregation (Diabet Med 1989;6:278; Diabet Care 1987;10:786-790), leading to patient safety and immunogenicity concerns. Because of the silicone oil application process (Biotech Adv 2007;25:318-324), silicone oil levels tend to vary between individual container closures. Various silicone oil levels were applied to a container closure prior to filling and lyophilization of an albumin and interferon alfa-2b fusion protein (albinterferon alfa-2b). Data demonstrated that high silicone oil levels in combination with intended and stress storage conditions had no impact on protein purity, higher order structure, stability trajectory, or biological activity. Subvisible particulate analysis (1-10 µm range) from active and placebo samples from siliconized glass barrels showed similar particle counts. Increases in solution turbidity readings for both active and placebo samples correlated well with increases in silicone oil levels, suggesting that the particles in solution are related to the presence of silicone oil and not large protein aggregates. Results from this study demonstrate that silicone oil is not always detrimental to proteins; nevertheless, assessing the impact of silicone oil on a product case-by-case basis is still recommended.
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