Decreases in polysorbate (PS80) content were observed while evaluating the long-term storage stability of Chinese hamster ovary-derived, purified monoclonal antibodies. It was determined that polysorbate had been enzymatically degraded; therefore, studies were performed to identify and characterize the protein(s) responsible. Polysorbate degrading activity was enriched from Chinese hamster ovary media leading to the identification of group XV lysosomal phospholipase A2 isomer X1 (LPLA2) by shotgun proteomics. Recombinant LPLA2 was over expressed, purified, and functional integrity confirmed against a diheptanoyl phosphatidylcholine substrate. Incubation of recombinantly produced LPLA2 with PS20 and PS80 resulted in hydrolysis of PS20 and PS80 monoester but a much slower rate was observed for higher-order PS80. Endogenous LPLA2 was detected and quantitated at less than 1 ppm in 3 formulated antibodies while LPLA2 was not detected (or less than 0.1 ppm) in a fourth formulated antibody. Furthermore, antibodies with detectable quantities of endogenous LPLA2 demonstrated polysorbate hydrolysis while in contrast the antibody without detectable LPLA2 did not show polysorbate hydrolysis. Comparison of polysorbate degradation products generated from the formulated antibody and samples of polysorbate incubated with recombinant LPLA2 resulted in similar elution profiles by liquid chromatography-mass spectrometry. These results suggest that LPLA2 may play a key role in polysorbate degradation in some antibody preparations.
Keywords: HPLC; enzyme; mass spectrometry; protein; stability; surfactants.
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