Metabolic understanding of disulfide reduction during monoclonal antibody production

Clinical associations and potential cellular mechanisms linking G6PD deficiency and atherosclerotic cardiovascular disease

Glucose 6-phosphate dehydrogenase deficiency (G6PD-d) is the most common enzymopathy in the world, occurring in 5-8% of the global population (half a billion people). Recent epidemiological evidence suggests that G6PD-d may be associated with increased cardiovascular disease (CVD). Atherosclerosis is the dominant cause of CVD, including myocardial infarction, heart failure, stroke, and peripheral artery disease. Atherosclerosis, in turn, is a chronic inflammatory disease, fueled by oxidized lipids and influenced by various immune and nonimmune cells including vascular endothelial and smooth muscle cells, monocytes and macrophages, T cells, B cells, and red blood cells. Here, we review the existing epidemiological evidence supporting a role for G6PD-d in CVD in humans and explore the data on potential cellular mechanisms by which G6PD-d may exacerbate atherosclerosis.

Raman spectroscopy for monitoring free sulfhydryl formation during monoclonal antibody manufacturing

During production, harvested cell culture fluid (HCCF) can degrade due to reductases breaking interchain disulfide bonds, forming low molecular weight (LMW) impurities that contain free sulfhydryl and high molecular weight (HMW) impurities through disulfide shuffling. Thus, detecting and quantifying the free sulfhydryl increase in HCCF is critical. Herein, Raman spectroscopy is implemented as a process analytical technology, and multivariate data analysis is applied to characterize and quantify sulfhydryl formation in HCCF with disulfide-containing indicator molecules. Raman spectra qualitatively probe the presence or absence of disulfide bond breakage in antibodies, consistent with offline non-reduced capillary electrophoresis sodium dodecyl sulfate results. Between two antibodies studied, mAb A was identified for a higher risk of antibody reduction where sulfhydryl formation was observed within 16 h, while mAb B did not show similar concerns even after 1 week. The offline measurement of redox potential is below -100 mV in HCCF for mAb A, while the stable mAb B HCCF shows redox potentials above +20 mV. A multivariate partial least squares (PLS) model for quantification is developed using an offline free sulfhydryl assay, applying Raman spectra to predict free sulfhydryl concentration with high accuracy (R2 > 0.98) and expected mean error of 0.677 mM from the offline Ellman's Assay. This work confirms the use of Raman PAT to monitor real-time disulfide reduction, enabling improvements to process understanding and product quality.

New high-throughput screening method for Chinese hamster ovary cell lines expressing low reduced monoclonal antibody levels: application of a system controlling the gas phase over cell lysates in miniature bioreactors and facilitating multiple sample setup

Interchain disulfide bonds in monoclonal antibodies may be reduced during large-scale mAb production using Chinese hamster ovary (CHO) cells. This reaction lowers the mAb product yield and purity; however, it may be prevented by screening cell lines that are unsusceptible to reduction and using them in mAb production. Antibody reduction susceptibility may be cell line-dependent. To the best of our knowledge, however, an efficient method of screening reduction-unsusceptible CHO cell lines has not been previously reported. Here, we report a novel screening method that can simultaneously detect and identify mAb reduction susceptibility in lysates containing ≤ 48 CHO cell lines. This evaluation system was equally effective and generated similar results at all culture scales, including 250 mL, 3 L, and 1000 L. Furthermore, we discovered that reduction-susceptible cell lines contained higher total intracellular nicotinamide adenine dinucleotide phosphate (NADPH) and NADP+ concentrations than reduction-unsusceptible cell lines, regardless of whether they expressed immunoglobulin (Ig)G4 or IgG1. NADPH or NADP+ supplementation in the lysate of reduction-unsusceptible cells resulted in mAb reduction. Application of the innovative CHO cell line screening approach could mitigate or prevent reductions in large-scale mAb generation from CHO cells.

Untargeted proteomics reveals upregulation of stress response pathways during CHO-based monoclonal antibody manufacturing process leading to disulfide bond reduction

Monoclonal antibody (mAb) interchain disulfide bond reduction can cause a loss of function and negatively impact the therapeutic’s efficacy and safety. Disulfide bond reduction has been observed at various stages during the manufacturing process, including processing of the harvested material. The factors and mechanisms driving this phenomenon are not fully understood. In this study, we examined the host cell proteome as a potential factor affecting the susceptibility of a mAb to disulfide bond reduction in the harvested cell culture fluid (HCCF). We used untargeted liquid-chromatography-mass spectrometry-based proteomics experiments in conjunction with a semi-automated protein identification workflow to systematically compare Chinese hamster ovary (CHO) cell protein abundances between bioreactor conditions that result in reduction-susceptible and reduction-free HCCF. Although the growth profiles and antibody titers of these two bioreactor conditions were indistinguishable, we observed broad differences in host cell protein (HCP) expression. We found significant differences in the abundance of glycolytic enzymes, key protein reductases, and antioxidant defense enzymes. Multivariate analysis of the proteomics data determined that upregulation of stress-inducible endoplasmic reticulum (ER) and other chaperone proteins is a discriminatory characteristic of reduction-susceptible HCP profiles. Overall, these results suggest that stress response pathways activated during bioreactor culture increase the reduction-susceptibility of HCCF. Consequently, these pathways could be valuable targets for optimizing culture conditions to improve protein quality.