Introduction and clearance of beta-glucan in the downstream processing of monoclonal antibodies

β‐Glucan process‐related impurities can be introduced into biopharmaceutical products via upstream or downstream processing or via excipients. This study obtained a comprehensive process‐mapping dataset for five monoclonal antibodies to assess β‐glucan introduction and clearance during development and production runs at various scales. Overall, 198 data points were available for analysis. The greatest β‐glucan concentrations were found in the depth‐filtration filtrate (37–2,745 pg/ml). Load volume correlated with β‐glucan concentration in the filtrate, whereas flush volume was of secondary importance. Cation‐exchange chromatography significantly cleared β‐glucans. Furthermore, β‐glucan leaching from the Planova 20N virus removal filter was reduced by increasing the flush volume (1 vs. 10 L/m²). β‐glucan concentrations after filter flush with 10 L/m² were consistently <10 pg/ml. No or only limited β‐glucan clearance was attained via ultrafiltration/diafiltration (UF/DF). However, during the first run with monoclonal antibody (mAb) 4, β‐glucan concentration in the UF/DF retentate was 10.8 pg/mg, potentially due to β‐glucan leaching from the first run with a regenerated cellulose membrane. Overall, β‐glucan levels in the final mAb drug substance were 1–12 pg/mg. Assuming high doses of 1,000–5,000 mg, a β‐glucan contamination at 20 pg/mg would translate to 20–100 ng/dose, which is below the previously suggested threshold for product safety (≤500 ng/dose).

Applications and analysis of hydrolysates in animal cell culture

Animal cells are used in the manufacturing of complex biotherapeutic products since the 1980s. From its initial uses in biological research to its current importance in the biopharmaceutical industry, many types of culture media were developed: from serum-based media to serum-free to protein-free chemically defined media. The cultivation of animal cells economically has become the ultimate goal in the field of biomanufacturing. Serum serves as a source of amino acids, lipids, proteins and most importantly growth factors and hormones, which are essential for many cell types. However, the use of serum is unfavorable due to its high price tag, increased lot-to-lot variations and potential risk of microbial contamination. Efforts are progressively being made to replace serum with recombinant proteins such as growth factors, cytokines and hormones, as well as supplementation with lipids, vitamins, trace elements and hydrolysates. While hydrolysates are more complex, they provide a diverse source of nutrients to animal cells, with potential beneficial effects beyond the nutritional value. In this review, we discuss the use of hydrolysates in animal cell culture and briefly cover the composition of hydrolysates, mode of action and potential contaminants with some perspectives on its potential role in animal cell culture media formulations in the future.

Safety risk management for low molecular weight process-related impurities in monoclonal antibody therapeutics: Categorization, risk assessment, testing strategy, and process development with leveraging clearance potential

Process-related impurities (PRIs) derived from manufacturing process should be minimized in final drug product. ICH Q3A provides a regulatory road map for PRIs but excludes biologic drugs like monoclonal antibodies (mAbs) that contain biological PRIs (e.g. host cell proteins and DNA) and low molecular weight (LMW) PRIs (e.g., fermentation media components and downstream chemical reagents). Risks from the former PRIs are typically addressed by routine tests to meet regulatory expectations, while a similar routine-testing strategy is unrealistic and unnecessary for LMW PRIs, and thus a risk-assessment-guided testing strategy is often utilized. In this report, we discuss a safety risk management strategy including categorization, risk assessment, testing strategy, and its integrations with other CMC development activities, as well as downstream clearance potentials. The clearance data from 28 mAbs successfully addressed safety concerns but did not fully reveal the process clearance potentials. Therefore, we carried out studies with 13 commonly seen LMW PRIs in a typical downstream process for mAbs. Generally, Protein A chromatography and cation exchange chromatography operating in bind-and-elute mode showed excellent clearances with greater than 1,000- and 100-fold clearance, respectively. The diafiltration step had better clearance (greater than 100-fold) for the positively and neutrally charged LMW PRIs than for the negatively charged or hydrophobic PRIs. We propose that a typical mAb downstream process provides an overall clearance of 5,000-fold. Additionally, the determined sieving coefficients will facilitate diafiltration process development. This report helps establish effective safety risk management and downstream process design with robust clearance for LMW PRIs.

Specificity Influences in (1→3)-β-d-Glucan-Supported Diagnosis of Invasive Fungal Disease

(1→3)-β-glucan (BDG) testing as an adjunct in the diagnosis of invasive fungal disease (IFD) has been in use for nearly three decades. While BDG has a very high negative predictive value in this setting, diagnostic false positives may occur, limiting specificity and positive predictive value. Although results may be diagnostically false positive, they are analytically correct, due to the presence of BDG in the circulation. This review surveys the non-IFD causes of elevated circulating BDG. These are in the main, iatrogenic patient contamination through the use of BDG-containing medical devices and parenterally-delivered materials as well as translocation of intestinal luminal BDG due to mucosal barrier injury. Additionally, infection with Nocardia sp. may also contribute to elevated circulating BDG. Knowledge of the factors which may contribute to such non-IFD-related test results can improve the planning and interpretation of BDG assays and permit investigational strategies, such as serial sampling and BDG clearance evaluation, to assess the likelihood of contamination and improve patient care.

Control of leached beta-glucan levels from depth filters by an improved depth filtration flush strategy

Beta-glucans are polysaccharides of D-glucose monomers linked by (1-3) beta-glycosidic bonds, are found to have a potential immunogenicity risk in biotherapeutic products, and are labeled as process contaminants. A common source of beta-glucans is from the cellulose found in traditional depth filter media. Typically, beta-glucan impurities that leach into the product from the primary clarification depth filters can be removed by the subsequent bind-and-elute affinity chromatography capture step. Beta-glucans can also be removed by a bind-and-elute cation exchange chromatography step, which is useful for removing beta-glucans introduced by a post-Protein A depth filtration step. However, the increasing prevalence of flowthrough polishing chromatography poses a challenge for beta-glucan removal due to the lack of any bind-and-elute chromatography steps after the post-Protein A depth filter. In this work, a depth filter flush strategy was developed to control beta-glucan leaching into the product pool. Different loading conditions for the depth filtration and subsequent chromatography steps were evaluated to determine the robustness of the optimized flush strategy. Carry through runs demonstrated greater than two-fold reduction in beta-glucan levels using the optimized wash as compared to standard filter flush conditions.

Impact of hydrolysates on monoclonal antibody productivity, purification and quality in Chinese hamster ovary cells

Plant and yeast derived hydrolysates are economical and efficient alternative medium supplements to improve mammalian cell culture performance. We supplemented two commercial Chinese hamster ovary (CHO) culture media with hydrolysates from four different sources, yeast, soybean, Ex-Cell CD (a chemically defined hydrolysate replacement) and wheat to improve the productivity of two cell lines expressing different monoclonal antibodies (mAbs). Yeast, soybean and Ex-Cell CD improved the final mAb titer by increasing the specific productivity (qP) and/or extension of the culture period. Wheat hydrolysates increased peak viable cell density but did not improve productivity. IgG recovery from protein A purification was not compromised for all cultures by adding yeast, soybean and Ex-Cell CD hydrolysates except for one sample from soybean supplemented culture. Adding these three hydrolysates neither increased the amount of host cell protein, DNA or aggregate impurity amounts nor affect their clearance after purification. Profiling of the glycan types revealed that yeast and soybean hydrolysates could affect the distribution of galactosylated glycans. Ex-Cell CD performed the best at maintaining glycan profile compared to the non-supplemented cultures. Overall, yeast performed the best at improving CHO culture growth and productivity without being detrimental to downstream protein A processes but could affect mAb product glycan distribution while Ex-Cell CD yielded lower titers but has less effect on glycosylation. The hydrolysate to use would thus depend on the requirements of each process and our results would provide a good reference for improving culture performance with hydrolysates or related studies.