Micelle Driven Oxidation Mechansim and Novel Oxidation Markers for Different Grades of Polysorbate 20 and 80

Different types and quality grades of polysorbate (PS) were subjected to oxidative stress (in absence of protein), and novel oxidation markers were discovered by our newly developed liquid chromatography-mass spectrometry (LC-MS) screening method. These markers confirmed that the more homogeneous, PS grades, such as PS80 all-oleate grade (compliant with Chinese pharmacopoeia) and PS20 all-laurate grades are more prone to oxidative degradation compared to their multicompendial grade analogues. In a case study with pharmaceutically relevant monoclonal antibody formulations, we could confirm that the novel oxidation markers are also found in presence of protein. To the best of our knowledge, this is the first report on monitoring of PS oxidation markers in protein containing samples with the help of LC-MS. Based on the observations made in the PS degradation studies, a new hypothesis regarding the mechanism of oxidative PS degradation is suggested: PS oxidation primarily takes place in the PS micelles. This hypothesis was supported experimentally, PS oxidation could no longer be detected if PS micelles were dissolved by tert-butanol. Physiochemical parameters of PS micelles such as density of micelle cores, heterogeneity of PS fatty acid composition, micelle composition and trace metal ions are key driving factors of PS oxidation.