Keywords:mAb reduction / disulfide bond scrambling / free thiols
During the development of the production process for a monoclonal antibody (mAb), we observed a significant increase in the reduction of interchain disulfide bonds following pilot scale protein A purification of the produced antibody (IgG1κ).Different companies have reported the presence of fragmented IgG1 antibodies in the clarified cell culture fluid (CCCF) at manufacturing scale. It has been demonstrated  that enzymes of the thioredoxin system, released during the decline phase of the culture, were responsible for the interchain disulfide bond reduction. However, our observations were different as the majority of the interchain disulfide bonds were still oxidized in the CCCF. The massive fragmentation of interchain disulfide bonds occurred only after pilot scale protein A purification step. This study presents our insights in antibody reduction using scale-down models.