The application of caprylic acid in downstream processing of monoclonal antibodies

General strategies for IgG-like bispecific antibody purification

Bispecific antibodies (bsAbs) can simultaneously bind two different antigens or epitopes. Their dual-targeting capability enables novel mechanisms of action, gaining therapeutic advantages over conventional monospecific mAbs. In recent years, the number of bsAbs grows rapidly and bsAbs under development are available in diverse formats. In particular, Fc-containing IgG-like bsAbs, which represent the major group, can be constructed in asymmetric or symmetric format. For asymmetric ones, whose assembly requires multiple distinct chains, although numerous strategies have been developed to promote desired chain pairing, product-related variants such as free chains, half molecules and mispaired species are usually present at various levels. For symmetric ones, increased level of aggregates and truncating variants is often associated with their production. In general, bsAbs pose greater challenges to the downstream team than regular mAbs. In the past few years, our team successfully developed the downstream process for over 70 bsAbs in greater than 30 different formats and accumulated substantial experience. This review introduces general strategies that we have used while purifying these challenging molecules.

The downstream purification of bispecific antibodies

Bispecific antibodies, a class of therapeutic antibodies, can simultaneously bind to two distinct targets. Compared with monospecific antibodies, bispecific antibodies offer advantages, including superior efficacy and reduced side effects. However, because of their structural complexity, the purification of bispecific antibodies is highly challenging. The purification process must strike a delicate balance between purity and productivity, eliminating a broad spectrum of contaminants, including product-related and process-related impurities, while also maximizing the yield wherever feasible. This review systematically describes the strategies for bispecific antibody capture, the elimination of product-related impurities, and the mitigation of the formation of process-related impurities, thereby, providing guidance for the development of downstream purification processes for bispecific antibodies.

Clear insight into complex multimodal resins and impurities to overcome recombinant protein purification challenges: A review

Increasing attention has been paid to the purity of therapeutic proteins imposing extensive costs and challenges to the downstream processing of biopharmaceuticals. One of the efforts, that has been exerted to overcome such limitations, was developing multimodal or mixed-mode chromatography (MMC) resins for launching selective, orthogonal, non-affinity purification platforms. Despite relatively extensive usage of MMC resins, their real potential and fulfillment have not been extensively reviewed yet. In this work, the explanation of practical and key aspects of downstream processing of recombinant proteins with or without MMC resins was debated, as being useful for further purification process development. This review has been written as a step-by-step guide to deconvolute both inherent protein purification and MMC complexities. Here, after complete elucidation of the potential of MMC resins, the effects of frequently used additives (mobile phase modifiers) and their possible interactions during the purification process, the critical characteristics of common product-related impurities (e.g., aggregates, charge variants, fragments), host-related impurities (e.g., host cell protein and DNA) and process related impurities (e.g., endotoxin, and viruses) with solved or unsolved challenges of traditional and MMC resins have been discussed. Such collective experiences which are reported in this study could be considered as an applied guide for developing successful downstream processing in challenging conditions by providing a clear insight into complex MMC resins and impurities.

High-throughput, low-cost quantification of 11 therapeutic antibodies using caprylic acid precipitation and LC-MS/MS

BACKGROUND

Therapeutic drug monitoring of treatment with therapeutic antibodies is hampered by the application of a wide range of different methods in the quantification of serum levels. LC-MS based methods could significantly improve comparability of results from different laboratories, but such methods are often considered complicated and costly. We developed a method for LC-MS/MS based quantification of 11 therapeutic antibodies concomitantly measured in a single run, with emphasis on simplicity in sample preparation and low cost.

RESULTS

After a single-step sample purification using caprylic acid precipitation to remove interfering proteins, the sample underwent proteolysis followed by LC-MS/MS analysis. Infliximab is used as internal standard for sample preparation while isotope-labeled signature peptides identified for each analyte are internal standards for the LC-MS/MS normalization. The method was validated according to recognized guidelines, and pipetting steps can be performed by automated liquid handling systems. The total precision of the method ranged between 2.7 and 7.3 % (5.1 % average) across the quantification range of 4-256 μg/ml for all 11 drugs, with an average accuracy of 96.3 %. Matrix effects were xamined in 55 individual patient samples instead of the recommended 6, and 147 individual patient samples were screened for interfering compounds.

SIGNIFICANCE AND NOVELTY

Our method for simultaneous quantification of 11 t-mAb in human serum allows an unprecedented integration of robustness, speed and reduced complexity, which could pave the way for uniform use in research projects and clinical settings alike. In addition, the first LC-MS protocol for signature peptide-based quantification of durvalumab is described. This high throughput method can be readily adapted to a drug panel of choice.

Understanding virus retention mechanisms on protein a chromatography based on using different wash buffers - Evaluating the possibility for a generic wash buffer toolbox to improve virus clearance capacity

During manufacturing of mammalian-cell derived monoclonal antibodies (mAbs) virus clearance capacity of the downstream process has to be demonstrated. The protein A chromatography step typically achieves less than 4 log10 and is not considered as a major contributing step. Having been successfully applied to host cell protein removal before, we used different wash buffers for three mAbs with two model viruses (Minute virus of mice and Murine leukemia virus) in series as well as separately to further understand major contributing interactions for virus retention and potentially design a generic toolbox of stringent wash buffers to be applied to various mAbs. Results indicate a major relevance of hydrophobic interaction for Murine leukemia virus (xMuLV) and mAb A, based on improved clearance for buffers additionally containing increased levels of hydrophobic compounds. This effect was less pronounced for Minute virus of mice (MVM), whereby hydrogen-bonds were expected to play a stronger role for this model virus. Additionally, electrostatic interactions presumably are more relevant for MVM retention compared to xMuLV under the conditions evaluated. A generic mAb and virus-independent stringent wash buffer toolbox could not be identified. However, based on our results a customized mAb and virus wash buffer design with improved virus clearance is possible, with here demonstrated log reduction increase by 1.3 log10 for MVM and 2.2 log10 for xMuLV for the protein A step compared to equilibration buffer alone.

Ferguson plot analysis of multiple intermediate species of thermally unfolded bovine serum albumin

Ferguson plot was used to characterize the multiple intermediate species of bovine serum albumin (BSA) upon thermal unfolding. Differential scanning calorimetry showed an irreversible melting of BSA in Tris-HCl and phosphate buffers with a mid-transition temperature, Tm, of ∼68 °C. Thermally unfolded BSA was analyzed by agarose native gel electrophoresis stained by Coomassie blue and SYPRO Orange staining as a function of pH or protein concentration. SYPRO Orange was used to stain unfolded proteins. BSA heated at 70 and 80 °C, i.e., above the Tm, formed multiple intermediate species, which depended on the pH between 7.0 and 8.0, protein concentration and which buffer was used. These intermediate species were analyzed by Ferguson plot, which showed that BSA heated at 60 °C had a similar size to the native BSA, indicating that they are either native or native-like state consistent with no SYPRO Orange staining. The intermediate species observed at higher temperatures with the mobility less than that of the native BSA showed a steeper Ferguson plot and were stained by SYPRO Orange, indicating that these species had a larger hydrodynamic size than the native BSA and were unfolded.

Methods for addressing host cell protein impurities in biopharmaceutical product development

The high demand for monoclonal antibody (mAb) therapeutics in recent years has resulted in significant efforts to improve their costly manufacturing process. The high cost of manufacturing mAbs derives mainly from the purification process, which contributes to 50%-80% of the total manufacturing cost. One of the main challenges facing industry at the purification stage is the clearance of host cell proteins (HCPs) that are produced and often co-purified with the desired mAb product. One of the issues HCPs can cause is the degradation of the final mAb protein product. In this review, techniques are considered that can be used at different stages (upstream and downstream) of mAb manufacture to improve HCP clearance. In addition to established techniques, many new approaches for HCP removal are discussed that have the potential to replace current methods for improving HCP reduction and thereby the quality and stability of the final mAb product.

Sodium caprylate wash during Protein A chromatography as an effective means for removing protease(s) responsible for target antibody fragmentation

For recombinant proteins produced in Chinese hamster ovary (CHO) cells, fragmentation is a common phenomenon that results in generation of product-related low-molecular-weight (LMW) species. Recently while purifying a bispecific antibody (bsAb), we observed that the target protein experienced cleavage at a couple of potential sites, leading to truncated products. Further studies suggest that the cleavage can likely be attributed to residual CHO cell protease activity. In order to maximally remove potential protease(s) that contribute fragmentation, we optimized Protein A chromatography by adding sodium caprylate (SC) to the wash buffer. Upon optimization, fragmentation of Protein A eluate happened to a much lesser degree as compared to that of eluate from unoptimized process, and the increased sample stability is in accordance with significantly reduced host cell protein (HCP) level. Taken together, the data suggest that SC wash during Protein A chromatography is an effective means for removing HCPs including endogenous protease(s) that are responsible for target antibody fragmentation.

Protein Purification Technologies

Protein Biotechnology is an exciting and fast- growing area of research, with numerous industrial applications. The growing demand for developing efficient and rapid protein purification methods is driving research and growth in this area. Advances and progress in the techniques and methods of protein purification have been such that one can reasonably expect that any protein of a given order of stability may be purified to currently acceptable standards of homogeneity. However, protein manufacturing cost remains extremely high, with downstream processing constituting a substantial proportion of the overall cost. Understanding of the methods and optimization of the experimental conditions have become critical to the manufacturing industry in order to minimize production costs while satisfying the quality as well as all regulatory requirements. New purification processes exploiting specific, effective and robust methods and chromatographic materials are expected to guide the future of the protein purification market.

Simple and efficient protocol for immunoglobulin Y purification from chicken egg yolk

Besides being a common food component broadly consumed worldwide, egg yolk immunoglobulin Y (IgY) has essential therapeutic potentials. In fact, in a time of ever-increasing risk of antibiotic resistance, it is crucial to find new ways to battle infection, and oral administration of preformed specific antibodies represents one of the most attractive approaches against infection. Infectious diseases of bacterial and viral origin in humans and animals can be controlled and passively cured by orally applied IgYs isolated from chicken egg yolks. Despite multiple obvious advantages of oral administration of IgY, harvesting IgY from egg yolk in a pure form is a challenging task.

In this study, we developed a fast, simple, cost-effective, and efficient protocol for IgY isolation from chicken egg yolks. First, egg yolk was collected and diluted with 5 volumes of cold distilled water, homogenized, pH adjusted, and centrifuged. Next, the supernatant was collected, to which caprylic acid at concentration of 2% v/v was added, followed by pH adjustment to pH 5.0, centrifugation at 4°C, and collection of the resulting supernatant. This step was repeated twice, with adding 2% v/v of caprylic acid each time. The final supernatant was concentrated using ultrafiltration, and the IgY purity and activities were checked by SDS-PAGE, western blotting, and ELISA. The sequential (2, 2, 2%) addition of caprylic acid yielded IgY with a purity of 63.5, 90.6, and 95.8%, respectively, and reached 97.9% after ultrafiltration at pH 9.0. The IgY activity increased exponentially to reach 99% after the ultrafiltration step.

The proposed caprylic-acid-based protocol of IgY purification from the yolk of chicken eggs seems to be simple, fast, direct, and very cheap. This indicates that this protocol has great potential for scale-up processing.

Sodium caprylate induced precipitation post Protein A chromatography as an effective means for host cell protein clearance

In downstream processing of monoclonal antibody (mAb), post Protein A neutralization and subsequent intermediate depth filtration are critical steps for host cell protein (HCP) clearance. Previous studies have shown that adding caprylic acid (CA) during neutralization can further improve HCP removal by promoting their precipitation. In this study, we replaced CA with its sodium salt - sodium caprylate (SC). For the five mAbs studied, SC has been shown to be equally effective as CA at precipitating HCPs. As the salt form has a higher solubility, SC stock solution with relatively high concentration can be easily prepared, which facilitates its adding to the Protein A elution pool. Thus, this study not only confirms the effectiveness of CA/SC-induced HCP precipitation but also provides a more convenient way to integrate this method into the downstream process.