Reduction of disulfide bonds in monoclonal antibodies (mAbs) has been observed in several cases during the scale-up of Chinese Hamster Ovary cell-based products. Literature has linked this reduction to several factors, including cell shearing, temperature, dissolved oxygen content, media composition, reductive enzymes, and harvest duration. In this case study, a pilot scale run resulted in reduced IgG4 mAb product detected by non-reduced gel electrophoresis.  This was not seen in reduced scale bioreactors nor in other product quality assays. Replicating this failed batch using the reduced scale model was problematic and required harsh reducing harvest conditions. Additionally, reduced product was challenging to identify with traditional in-process testing, requiring more refined and controlled capillary sodium dodecyl sulfate gel electrophoresis procedure. After successfully reproducing the reduced mAb, process intermediates, including clarified harvest and Protein-A chromatography eluate, were treated and reoxidized from 15% to greater than 95% intact mAb.  Furthermore, the reconstituted mAbs maintained the desired product quality attributes of the reference material for control reactors. This work describes small scale time-dependent methods to reduce mAb intrachain disulfide bonds during harvest followed by reoxidation during downstream processing without modification of media or addition of chemical reagents to cell harvest.<br/>

Reoxidation of reduced monoclonal antibody using modified downstream processing

255th National Meeting (2018)

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