Protein Sub-Visible Particle and Free Radical formation of a Freeze-Dried Monoclonal Antibody Formulation during Dropping.

Dropping during shipping and handling of liquid biopharmaceutical formulations has long been known to cause protein degradation and aggregation. On the other hand, accidental dropping of freeze-dried protein formulations is generally considered not a major issue for biopharmaceutical quality. Reports of stability and especially the underling degradation mechanism(s) during shipping and handling of freeze-dried protein formulations were rarely seen in literature. In this manuscript, we report an interesting phenomenon in which repeated dropping of freeze-dried monoclonal antibody X (mAb-X) formulation powder resulted in significant protein sub-visible particles (SbVPs) in the reconstituted liquid as determined by the sensitive particle analyzing technique micro-flow imaging (MFI). Free radicals were observed after repeated dropping by electron paramagnetic resonance (EPR). Formation of SbVPs could be partially inhibited by the free radical scavengers methionine and 3-carbamoyl-2,2,5,5-tetramethyl-1-pyrrolidin-yloxy free radical (CTPO). The amount of free radicals and SbVPs was correlated to the sample temperature during dropping. Therefore we propose that the high temperature formed during dropping was probably the root cause for protein aggregation and free radical formation, which could further cause protein aggregation. Our observations suggest that similar to liquid protein formulations, dropping of freeze-dried protein formulations should also be avoided or mitigated.