Disulphide bond reduction of a therapeutic monoclonal antibody during cell culture manufacturing operations

Background Disulphide bonding is critical to maintaining immunoglobulin (IgG) tertiary and quaternary structure for therapeutic monoclonal antibodies (MAb). Both interand intra-chain disulphide bonds are formed intracellularly in the expression host prior to secretion and purification during MAb production processes. Disulphide bond shuffling has previously been reported for IgG2[1,2] and disulphide-mediated arm-exchange for IgG4[3,4], reflecting innate behaviour of these IgG classes. However, atypical and significant reduction of disulphide bonds has been recently observed in IgG1[5,6] that present significant issues for manufacturing of therapeutic MAbs. During manufacturing of preliminary lots of a recently transferred MAb manufacturing process (IgG1), gross disulphide bond reduction following affinity capture chromatography of clarified production bioreactor material was observed. Investigations leading to the identification of the nature of this reduction process, and process steps to mitigate against its future occurrence, are described here. The MAb was co-developed with MacroGenics, Rockville, MD.