CHO cell cultures in shake flasks and bioreactors present different host cell protein profiles in the supernatant

Discovery of Chemical Tools for Polysorbate-Degradative Enzyme Control in the Biopharmaceutical Upstream Process via Multi-Omic Profiling of Host Cell Clones

Host cell proteins are process-related impurities in biotherapeutics and can potentially pose risks to patient safety and product quality. Specifically, certain host cell-derived enzymes, including lipases, can degrade the formulation excipient polysorbate (PS) in biopharmaceutical formulations, affecting drug product stability in liquid formulations. We leveraged multiomics approaches, including transcriptomics, proteomics, and activity-based protein profiling (ABPP), to identify mechanisms that regulate PS-degradative enzyme (PSDE) abundance and to develop strategies for their control. Comparative multiomics analysis of two monoclonal antibody (mAb)-producing host cell clones revealed differential lipase profiles at the mRNA, protein, and enzyme activity levels and associated increased lipase activity with upregulated lipid catabolic pathways such as the fatty acid beta oxidation pathway. Further, for the first time in the literature, we identified peroxisome proliferator-activated receptor γ (PPARγ) as a key regulator of PSDEs in manufacturing Chinese Hamster Ovary (CHO) cells. Downregulation of the PPARγ pathway with its antagonists resulted in a selective reduction of PSDE levels and improved PS stability without compromising mAb productivity or quality. This study highlights the potential of PPARγ modulators as chemical tools for PSDE control at the gene regulation level, offering significant implications for biopharmaceutical process development and control.

Development of an Optimized LC-MS Workflow for Host Cell Protein Characterization to Support Upstream Process Development

Host cell proteins (HCPs) coexpressed during the production of biotherapeutics can affect the safety, efficacy, and stability of the final product. As such, monitoring HCP populations and amounts throughout the production and purification process is an essential part of the overall quality control framework. Mass spectrometry (MS) is used as an orthogonal method to enzyme-linked immunosorbent assays (ELISA) for the simultaneous identification and quantification of HCPs, particularly for the analysis of downstream processes. In this study, we present an MS-based analytical protocol with improvements in both speed and identification performance that can be implemented for routine analysis to support upstream process development. The protocol adopts a streamlined sample preparation strategy, combined with a high-throughput MS analysis pipeline. The developed method identifies and quantifies over 1000 HCPs, including 20 proteins listed as high risk in the literature, in a clarified cell culture sample with repeatability and precision shown for digest replicates. In addition, we explore the effects of varying standard spike-ins and changes to the data processing pipeline on absolute quantification estimates of the HCPs, which highlight the importance of standardization for wider use in the industry. Data are available via ProteomeXchange with the identifier PXD053035.

Proteomics Reveals Distinctive Host Cell Protein Expression Patterns in Fed-Batch and Perfusion Cell Culture Processes

Chinese hamster ovary (CHO) cells are widely used to produce recombinant proteins, including monoclonal antibodies (mAbs), through various process modes. While fed-batch (FB) processes have been the standard, a shift toward high-density perfusion processes is being driven by increased productivity, flexible facility footprints, and lower costs. Ensuring the clearance of process-related impurities, such as host cell proteins (HCPs), is crucial in biologics manufacturing. Although purification processes remove most impurities, integrated strategies are being developed to enhance clearance of some high-risk HCPs. Current understanding of HCP expression dynamics in cell culture is limited. This study utilized data-independent acquisition (DIA) proteomics to compare the proteomic profiles of cell culture supernatants from 14 FB clones and three perfusion clones, all expressing the same mAb from the same host cell line. Results showed that perfusion processes enhance cell growth and productivity, exhibiting distinct proteomic profiles compared to FB processes. Perfusion processes also maintain a more comparable HCP abundance profile across clones, especially for 46 problematic HCPs monitored. Cluster analysis of FB proteomics revealed distinct abundance patterns and correlations with process parameters. Differential abundance analysis identified significant protein differences between the two processes. This is the first extensive study characterizing HCPs expressed by clones under different process modes. Further research could lead to strategies for preventing or managing problematic HCPs in biologics manufacturing.

Host cell proteins in monoclonal antibody processing: Control, detection, and removal

Host cell proteins (HCPs) are process-related impurities in a therapeutic protein expressed using cell culture technology. This review presents biopharmaceutical industry trends in terms of both HCPs in the bioprocessing of monoclonal antibodies (mAbs) and the capabilities for HCP clearance by downstream unit operations. A comprehensive assessment of currently implemented and emerging technologies in the manufacturing processes with extensive references was performed. Meta-analyses of published downstream data were conducted to identify trends. Improved analytical methods and understanding of "high-risk" HCPs lead to more robust manufacturing processes and higher-quality therapeutics. The trend of higher cell density cultures leads to both higher mAb expression and higher HCP levels. However, HCP levels can be significantly reduced with improvements in operations, resulting in similar concentrations of approx. 10 ppm HCPs. There are no differences in the performance of HCP clearance between recent enhanced downstream operations and traditional batch processing. This review includes best practices for developing improved processes.

Improved Time Resolved KPI and Strain Characterization of Multiple Hosts in Shake Flasks Using Advanced Online Analytics and Data Science

Shake flasks remain one of the most widely used cultivation systems in biotechnology, especially for process development (cell line and parameter screening). This can be justified by their ease of use as well as their low investment and running costs. A disadvantage, however, is that cultivations in shake flasks are black box processes with reduced possibilities for recording online data, resulting in a lack of control and time-consuming, manual data analysis. Although different measurement methods have been developed for shake flasks, they lack comparability, especially when changing production organisms. In this study, the use of online backscattered light, dissolved oxygen, and pH data for characterization of animal, plant, and microbial cell culture processes in shake flasks are evaluated and compared. The application of these different online measurement techniques allows key performance indicators (KPIs) to be determined based on online data. This paper evaluates a novel data science workflow to automatically determine KPIs using online data from early development stages without human bias. This enables standardized and cost-effective process-oriented cell line characterization of shake flask cultivations to be performed in accordance with the process analytical technology (PAT) initiative. The comparison showed very good agreement between KPIs determined using offline data, manual techniques, and automatic calculations based on multiple signals of varying strengths with respect to the selected measurement signal.

Comprehensive Assessment of Host Cell Protein Expression after Extended Culture and Bioreactor Production of CHO Cell Lines

The biomanufacturing industry is advancing toward continuous processes that will involve longer culture durations and older cell ages. These upstream trends may bring unforeseen challenges for downstream purification due to fluctuations in host cell protein (HCP) levels. To understand the extent of HCP expression instability exhibited by Chinese hamster ovary (CHO) cells over these time scales, an industry-wide consortium collaborated to develop a study to characterize age-dependent changes in HCP levels across 30, 60, and 90 cell doublings, representing a period of approximately 60 days. A monoclonal antibody (mAb)-producing cell line with bulk productivity up to 3 g/L in a bioreactor was aged in parallel with its parental CHO-K1 host. Subsequently, both cell types at each age were cultivated in an automated bioreactor system to generate harvested cell culture fluid (HCCF) for HCP analysis. More than 1,500 HCPs were quantified using complementary proteomic techniques, two-dimensional electrophoresis (2DE) and liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). While up to 13% of proteins showed variable expression with age, more changes were observed when comparing between the two cell lines with up to 47% of HCPs differentially expressed. A small subset (50 HCPs) with age-dependent expression were previously reported to be problematic as high-risk and/or difficult-to-remove impurities; however, the vast majority of these were down-regulated with age. Our findings suggest that HCP expression changes over this time scale may not be as dramatic and pose as great of a challenge to downstream processing as originally expected but that monitoring of variably expressed problematic HCPs remains critical. This article is protected by copyright. All rights reserved.

Targeted CHO cell engineering approaches can reduce HCP-related enzymatic degradation and improve mAb product quality

Host cell proteins (HCP) that co-purify with biologics produced in Chinese hamster ovary cells have been shown to impact product quality through proteolytic degradation of recombinant proteins, leading to potential product losses. Several problematic HCPs can remain in the final product even after extensive purification. Each recombinant cell line has a unique HCP profile that can be determined by numerous upstream and downstream factors, including clonal variation and the protein sequence of the expressed therapeutic molecule. Here, we worked with recombinant cell lines with high levels of copurifying HCPs, and showed that in those cell lines even modest downregulation (≤50%) of the difficult to remove HCP Cathepsin D, through stable short hairpin RNA interference or monoallelic deletion of the target gene using CRISPR-Cas9, is sufficient to greatly reduce levels of co-purifying HCP as measured by high throughput targeted LC-MS. This reduction led to improved product quality by reducing fragmentation of the drug product in forced degradation studies to negligible levels. We also show the potential of cell engineering to target other undesired HCPs and relieve the burden on downstream purification.

Trends in Monoclonal Antibody Production Using Various Bioreactor Syst

Monoclonal antibodies are widely used as diagnostic reagents and for therapeutic purposes, and their demand is increasing extensively. To produce these proteins in sufficient quantities for commercial use, it is necessary to raise the output by scaling up the production processes. This review describes recent trends in high-density cell culture systems established for monoclonal antibody production that are excellent methods to scale up from the lab-scale cell culture. Among the reactors, hollow fiber bioreactors contribute to a major part of high-density cell culture as they can provide a tremendous amount of surface area in a small volume for cell growth. As an alternative to hollow fiber reactors, a novel disposable bioreactor has been developed, which consists of a polymer-based supermacroporous material, cryogel, as a matrix for cell growth. Packed bed systems and disposable wave bioreactors have also been introduced for high cell density culture. These developments in high-density cell culture systems have led to the monoclonal antibody production in an economically favourable manner and made monoclonal antibodies one of the dominant therapeutic and diagnostic proteins in biopharmaceutical industry.