Chromatography process development in the quality by design paradigm I: Establishing a high‐throughput process development platform as a tool for estimating “characterization space” for an ion exchange chromatography step

This article describes the development of a high‐throughput process development (HTPD) platform for developing chromatography steps. An assessment of the platform as a tool for establishing the “characterization space” for an ion exchange chromatography step has been performed by using design of experiments. Case studies involving use of a biotech therapeutic, granulocyte colony‐stimulating factor have been used to demonstrate the performance of the platform. We discuss the various challenges that arise when working at such small volumes along with the solutions that we propose to alleviate these challenges to make the HTPD data suitable for empirical modeling. Further, we have also validated the scalability of this platform by comparing the results from the HTPD platform (2 and 6 μL resin volumes) against those obtained at the traditional laboratory scale (resin volume, 0.5 mL). We find that after integration of the proposed correction factors, the HTPD platform is capable of performing the process optimization studies at 170‐fold higher productivity. The platform is capable of providing semi‐quantitative assessment of the effects of the various input parameters under consideration. We think that platform such as the one presented is an excellent tool for examining the “characterization space” and reducing the extensive experimentation at the traditional lab scale that is otherwise required for establishing the “design space.” Thus, this platform will specifically aid in successful implementation of quality by design in biotech process development. This is especially significant in view of the constraints with respect to time and resources that the biopharma industry faces today. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29: 403–414, 2013     

A label-free methodology for selective protein quantification by means of absorption measurements

The application of high throughput experimentation (HTE) in protein purification process development has created an analytical bottleneck. Using a new label-free and non-invasive methodology for analyzing multicomponent protein mixtures by means of spectral measurements, we show that the analytical throughput for selective protein quantification can be increased significantly. An analytical assay based on this new methodology was shown to generate very precise results. Further, the assay was successfully applied as analytics for a resin screening performed in HTE mode. The increase in analytical throughput was obtained without decreasing the level of information when compared to analytical chromatography. This proves its potential as a valuable analytical tool in conjugation with high throughput process development (HTPD). Further, fast selective protein quantification can enhance process control in a commercial production environment and, hence, minimize the need for off-line release analysis.     

High‐throughput process development of purification alternatives for the protein avidin

With an increased number of applications in the field of the avidin‐biotin technology, the resulting demand for highly‐purified protein avidin has drawn our attention to the purification process of avidin that naturally occurs in chicken egg white. The high‐throughput process development (HTPD) methodology was exploited, in order to evaluate purification process alternatives to commonly used ion‐exchange chromatography. In a high‐throughput format, process parameters for aqueous two‐phase extraction, selective precipitation with salts and polyethylene glycol, and hydrophobic interaction and mixed‐mode column chromatography experiments were performed. The HTPD strategy was complemented by a high‐throughput tandem high‐performance liquid chromatography assay for protein quantification. Suitable conditions for the separation of avidin from the major impurities ovalbumin, ovomucoid, ovotransferrin, and lysozyme were identified in the screening experiments. By combination of polyethylene glycol precipitation with subsequent resolubilization and separation in a polyethylene glycol/sulfate/sodium chloride two‐phase system an avidin purity of 77% was obtained with a yield >90% while at the same time achieving a significant reduction of the process volume. The two‐phase extraction and precipitation results were largely confirmed in larger scale with scale‐up factors of 230 and 133, respectively. Seamless processing of the avidin enriched bottom phase was found feasible by using mixed‐mode chromatography. By gradient elution a final avidin purity of at least 97% and yield >90% was obtained in the elution pool. The presented identification of a new and beneficial alternative for the purification of the high value protein thus represents a successful implementation of HTPD for an industrially relevant purification task. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:957–973, 2015     

A practical strategy for using miniature chromatography columns in a standardized high‐throughput workflow for purification development of monoclonal antibodies

The emergence of monoclonal antibody (mAb) therapies has created a need for faster and more efficient bioprocess development strategies in order to meet timeline and material demands. In this work, a high‐throughput process development (HTPD) strategy implementing several high‐throughput chromatography purification techniques is described. Namely, batch incubations are used to scout feasible operating conditions, miniature columns are then used to determine separation of impurities, and, finally, a limited number of lab scale columns are tested to confirm the conditions identified using high‐throughput techniques and to provide a path toward large scale processing. This multistep approach builds upon previous HTPD work by combining, in a unique sequential fashion, the flexibility and throughput of batch incubations with the increased separation characteristics for the packed bed format of miniature columns. Additionally, in order to assess the applicability of using miniature columns in this workflow, transport considerations were compared with traditional lab scale columns, and performances were mapped for the two techniques. The high‐throughput strategy was utilized to determine optimal operating conditions with two different types of resins for a difficult separation of a mAb monomer from aggregates. Other more detailed prediction models are cited, but the intent of this work was to use high‐throughput strategies as a general guide for scaling and assessing operating space rather than as a precise model to exactly predict performance. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:626–635, 2014     

Understanding the mechanism of virus removal by Q sepharose fast flow chromatography during the purification of CHO‐cell derived biotherapeutics

During production of therapeutic monoclonal antibodies (mAbs) in mammalian cell culture, it is important to ensure that viral impurities and potential viral contaminants will be removed during downstream purification. Anion exchange chromatography provides a high degree of virus removal from mAb feedstocks, but the mechanism by which this is achieved has not been characterized. In this work, we have investigated the binding of three viruses to Q sepharose fast flow (QSFF) resin to determine the degree to which electrostatic interactions are responsible for viral clearance by this process. We first used a chromatofocusing technique to determine the isoelectric points of the viruses and established that they are negatively charged under standard QSFF conditions. We then determined that virus removal by this chromatography resin is strongly disrupted by the presence of high salt concentrations or by the absence of the positively charged Q ligand, indicating that binding of the virus to the resin is primarily due to electrostatic forces, and that any non‐electrostatic interactions which may be present are not sufficient to provide virus removal. Finally, we determined the binding profile of a virus in a QSFF column after a viral clearance process. These data indicate that virus particles generally behave similarly to proteins, but they also illustrate the high degree of performance necessary to achieve several logs of virus reduction. Overall, this mechanistic understanding of an important viral clearance process provides the foundation for the development of science‐based process validation strategies to ensure viral safety of biotechnology products. Biotechnol. Bioeng. 2009; 104: 371–380 © 2009 Wiley Periodicals, Inc.     

Using high throughput screening to define virus clearance by chromatography resins

High throughput screening (HTS) of chromatography resins can accelerate downstream process development by rapidly providing information on product and impurity partitioning over a wide range of experimental conditions. In addition to the removal of typical product and process‐related impurities, chromatography steps are also used to remove potential adventitious viral contaminants and non‐infectious retrovirus‐like particles expressed by rodent cell lines used for production. This article evaluates the feasibility of using HTS in a 96‐well batch‐binding format to study removal of the model retrovirus xenotropic murine leukemia virus (xMuLV) from product streams. Two resins were examined: the anion exchange resin Q Sepharose Fast Flow? (QSFF) and Capto adhere?, a mixed mode resin. QSFF batch‐binding HTS data was generated using two mAbs at various pHs, NaCl concentrations, and levels of impurities. Comparison of HTS data to that generated using the column format showed good agreement with respect to virus retentation at different pHs, NaCl concentrations and impurity levels. Results indicate that NaCl concentration and impurity level, but not pH, are key parameters that can impact xMuLV binding to both resins. Binding of xMuLV to Capto adhere appeared to tolerate higher levels of NaCl and impurity than QSFF, and showed some product‐specific impact on binding that was not observed with QSFF. Overall, the results demonstrate that the 96‐well batch‐binding HTS technique can be an effective tool for rapidly defining conditions for robust virus clearance on chromatographic resins. Biotechnol. Bioeng. 2013; 110: 1984–1994. © 2013 Wiley Periodicals, Inc.     

Mechanistic insights into viral clearance during the chromatography steps in antibody processes by using virus surrogates

Viral safety is required for biological products to treat human diseases, and the burden of inactivation and or virus removal lies on the downstream purification process. Minute virus of mice (MVM) is a nonenveloped parvovirus commonly used as the worst-case model virus in validation studies because of its small size and high chemical stability. In this study, we investigated the use of MVM-mock virus particle (MVP) and bacteriophage ΦX174 as surrogates for MVM to mimic viral clearance studies, with a focus on chromatography operations. Based on structural models and comparison of log reduction value among MVM, MVP, and ΦX174, it was demonstrated that MVP can be used as a noninfectious surrogate to assess viral clearance during process development in multiple chromatography systems in a biosafety level one (BSL-1) laboratory. Protein A (ProA) chromatography was investigated to strategically assess the impact of the resin, impurities, and the monoclonal antibody product on virus removal.     

A versatile noninvasive method for adsorber quantification in batch and column chromatography based on the ionic capacity

Within the Quality by Design (QbD) framework proposed by the International Conference on Harmonisation (ICH), high‐throughput process development (HTPD) and mechanistic modeling are of outstanding importance for future biopharmaceutical chromatography process development. In order to compare the data derived from different column scales or batch chromatographies, the amount of adsorber has to be quantified with the same noninvasive method. Similarly, an important requirement for the implementation of mechanistic modeling is the reliable determination of column characteristics such as the ionic capacity Λ for ion‐exchange chromatography with the same method at all scales and formats. We developed a method to determine the ionic capacity in column and batch chromatography, based on the adsorption/desorption of the natural, uv‐detectable amino acid histidine. In column chromatography, this method produces results comparable to those of classical acid?base titration. In contrast to acid?base titration, this method can be adapted to robotic batch chromatographic experiments. We are able to convert the adsorber volumes in batch chromatography to the equivalent volume of a compressed column. In a case study, we demonstrate that this method increases the quality of SMA parameters fitted to batch adsorption isotherms, and the capability to predict column breakthrough experiments. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:666–677, 2016     

A tool for increasing the lifetime of chromatography resins

There is a steadily increasing demand for speed, cost efficiency and process understanding within biopharmaceutical process development. To match this, a high-throughput method for screening of cleaning-in-place (CIP) conditions for chromatography resins has been developed. The methodology includes fouling of MabSelect SuRe chromatography resin in 96-well filter plates, cleaning of the fouled resin by incubation in different CIP agents, and finally, analysis of the residual impurities on the resin after cleaning. This article describes the improvements that transformed the method from low throughput and significant manual interference to a totally automated method with high throughput and good reproducibility.Key words: bioprocess, cleaning-in-place, chromatography, high-throughput, monoclonal antibody, process development, protein A, screening     

A tool for increasing the lifetime of chromatography resins

There is a steadily increasing demand for speed, cost efficiency, and process understanding within biopharmaceutical process development. To match this, a high-throughput method for screening of cleaning-in-place (CIP) conditions for chromatography resins has been developed. The methodology includes fouling of MabSelect SuRe chromatography resin in 96-well filter plates, cleaning of the fouled resin by incubation in different CIP agents, and finally, analysis of the residual impurities on the resin after cleaning. This article describes the improvements that transformed the method from low throughput and significant manual interference to a totally automated method with high throughput and good reproducibility.     

SwellGel: a sample preparation affinity chromatography technology for high throughput proteomic applications

Development of high throughput systems for purification and analysis of proteins is essential for the success of today's proteomic research. We have developed an affinity chromatography technology that allows the customization of high capacity/high throughput chromatographic separation of proteins. This technology utilizes selected chromatography media that are dehydrated to form uniform SwellGel discs. Unlike wet resin slurries, these discs are easily adaptable to a variety of custom formats, eliminating problems associated with resin dispensing, equilibration, or leakage. Discs can be made in assorted sizes (resin volume 15 microl-3 ml) dispensed in various formats (384-, 96-, 48-, and 24-well microplates or columns) and different ligands can be attached to the matrix. SwellGel discs rapidly hydrate upon addition of either water or the protein sample, providing dramatically increased capacity compared to coated plates. At the same time, the discs offer greater stability, reproducibility, and ease of handling than standard wet chromatography resins. We previously reported the development of SwellGel for the purification of 6x His- and glutathione-S-transferase (GST)-tagged fusion proteins [Prot. Exp. Purif. 22 (2001) 359-366]. In this paper, we discuss an expanded list of SwellGel stabilized chromatographic methods that have been adapted to high throughput formats for processing protein samples ranging from 10 microl to 10 ml (1 microg to 50 mg protein). Data are presented applying SwellGel discs to high throughput proteomic applications such as affinity tag purification, protein desalting, the removal of abundant proteins from serum including albumin and immunoglobulin, and the isolation of phosphorylated peptides for mass spectrometry.     

Strategies for developing design spaces for viral clearance by anion exchange chromatography during monoclonal antibody production

The quality‐by‐design (QbD) regulatory initiative promotes the development of process design spaces describing the multidimensional effects and interactions of process variables on critical quality attributes of therapeutic products. However, because of the complex nature of production processes, strategies must be devised to provide for design space development with reasonable allocation of resources while maintaining highly dependable results. Here, we discuss strategies for the determination of design spaces for viral clearance by anion exchange chromatography (AEX) during purification of monoclonal antibodies. We developed a risk assessment for AEX using a formalized method and applying previous knowledge of the effects of certain variables and the mechanism of action for virus removal by this process. We then use design‐of‐experiments (DOE) concepts to perform a highly fractionated factorial experiment and show that varying many process parameters simultaneously over wide ranges does not affect the ability of the AEX process to remove endogenous retrovirus‐like particles from CHO‐cell derived feedstocks. Finally, we performed a full factorial design and observed that a high degree of viral clearance was obtained for three different model viruses when the most significant process parameters were varied over ranges relevant to typical manufacturing processes. These experiments indicate the robust nature of viral clearance by the AEX process as well as the design space where removal of viral impurities and contaminants can be assured. In addition, the concepts and methodology presented here provides a general approach for the development of design spaces to assure that quality of biotherapeutic products is maintained. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Defining the mechanistic binding of viral particles to a multi‐modal anion exchange resin

A multi‐tiered approach to determine the binding mechanism of viral clearance utilizing a multi‐modal anion exchange resin was applied to a panel of four viral species that are typically used in validating viral clearance studies (i.e., X‐MuLV, MVM, REO3, and PrV). First, virus spiked buffer‐only experiments were conducted to evaluate the virus's affinity for single mode and multi‐modal chromatography resins under different buffer conditions in a chromatography column setting. From these results we hypothesize that the mechanisms of binding of the viruses involve binding to both the hydrophobic and anionic functional groups. This mechanistic view agreed with the general surface characteristics of the different virus species in terms of isoelectric point and relative hydrophobicity values. This hypothesized mechanistic binding was then tested with commercially relevant, in‐process materials, in which competitive binding occurred between the load components (e.g., viruses, target product, and impurities) and the resin. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1019–1026, 2018     

Real time quantitative PCR as a method to evaluate simian virus 40 removal during pharmaceutical protein purification.

Continuous cell lines used for pharmaceutical protein manufacturing have the potential to be contaminated by viruses. To ensure the safety of pharmaceutical proteins derived from continuous cell lines, validation of the ability of the manufacturing process to clear potential contaminating viruses is required for product registration. In this paper, a real time quantitative PCR method has been applied to the evaluation of simian virus 40 (SV40) removal during chromatography and filtration procedures. This method takes advantage of the 5'-3' exonuclease activity of Taq DNA polymerase and utilizes the PRISM 7700 sequence detection system of PE Applied Biosystems for automated SV40 DNA quantification through a dual-labeled fluorogenic probe. This method provides accurate and reproducible quantification of SV40 DNA. The SV40 clearance during chromatography and filtration procedures determined by this method is highly comparable with that determined by the cell-based infectivity assay. This method offers significant advantages over cell-based infectivity assays, such as higher sensitivity, greater reliability, higher sample throughput and lower cost. This method can be potentially used to evaluate the clearance of all model viruses during chromatography and filtration procedures. This method can be used to substitute cell-based infectivity assays for process validation of viral removal procedures and the availability of this method should greatly facilitate and reduce the cost of viral clearance evaluations required for new biologic product development.     

Anion exchange chromatography provides a robust, predictable process to ensure viral safety of biotechnology products

The mammalian cell-lines used to produce biopharmaceutical products are known to produce endogenous retrovirus-like particles and have the potential to foster adventitious viruses as well. To ensure product safety and regulatory compliance, recovery processes must be capable of removing or inactivating any viral impurities or contaminants which may be present. Anion exchange chromatography (AEX) is a common process in the recovery of monoclonal antibody products and has been shown to be effective for viral removal. To further characterize the robustness of viral clearance by AEX with respect to process variations, we have investigated the ability of an AEX process to remove three model viruses using various combinations of mAb products, feedstock conductivities and compositions, equilibration buffers, and pooling criteria. Our data indicate that AEX provides complete or near-complete removal of all three model viruses over a wide range of process conditions, including those typically used in manufacturing processes. Furthermore, this process provides effective viral clearance for different mAb products, using a variety of feedstocks, equilibration buffers, and different pooling criteria. Viral clearance is observed to decrease when feedstocks with sufficiently high conductivities are used, and the limit at which the decrease occurs is dependent on the salt composition of the feedstock. These data illustrate the robust nature of the AEX recovery process for removal of viruses, and they indicate that proper design of AEX processes can ensure viral safety of mAb products.     

Investigating the combination of single-pass tangential flow filtration and anion exchange chromatography for intensified mAb polishing

There is growing interest within the biopharmaceutical industry to improve manufacturing efficiency through process intensification, with the goal of generating more product in less time with smaller equipment. In monoclonal antibody (mAb) purification, a unit operation that can benefit from intensification is anion exchange (AEX) polishing chromatography. Single-pass tangential flow filtration (SPTFF) technology offers an opportunity for process intensification by reducing intermediate pool volumes and increasing product concentration without recirculation. This study evaluated the performance of an AEX resin, both in terms of host cell protein (HCP) purification and viral clearance, following concentration of a mAb feed using SPTFF. Results show that preconcentration of AEX feed material improved isotherm conditions for HCP binding, resulting in a fourfold increase in resin mAb loading at the target HCP clearance level. Excellent clearance of minute virus of mouse and xenotropic murine virus was maintained at this higher load level. The increased mAb loading enabled by SPTFF preconcentration effectively reduced AEX column volume and buffer requirements, shrinking the overall size of the polishing step. In addition, the suitability of SPTFF for extended processing time operation was demonstrated, indicating that this approach can be implemented for continuous biomanufacturing. The combination of SPTFF concentration and AEX chromatography for an intensified mAb polishing step which improves both manufacturing flexibility and process productivity is supported.     

Cation exchange chromatography performed in overloaded mode is effective in removing viruses during the manufacturing of monoclonal antibodies

Viral safety is a critical concern with regard to monoclonal antibody (mAb) products produced in mammalian cells such as Chinese hamster ovary cells. Manufacturers are required to ensure the safety of such products by validating the clearance of viruses in downstream purification steps. Cation exchange (CEX) chromatography is widely used in bind/elute mode as a polishing step in mAb purification. However, bind/elute modes require a large volume of expensive resin. To reduce the production cost, the use of CEX chromatography in overloaded mode has recently been investigated. The viral clearance ability in overloaded mode was evaluated using murine leukemia virus (MLV). Even under high-load conditions such as 2,000 g mAb/L resin, MLV was removed from mAb solutions. This viral clearance ability was not significantly affected by resin type or mAb type. The overloaded mode can also remove other types of viruses such as pseudorabies virus and reovirus Type 3 from mAb solutions. Based on these results, this cost-effective overloaded mode is comparable to the bind-elute mode in terms of viral removal.     

Integrated flow-through purification for therapeutic monoclonal antibodies processing

An integrated all flow-through technology platform for the purification of therapeutic monoclonal antibodies (mAb), consisting of activated carbon and flow-through cation and anion exchange chromatography steps, can replace a conventional chromatography platform. This new platform was observed to have excellent impurity clearance at high mAb loadings with overall mAb yield exceeding 80%. Robust removal of DNA and host cell protein was demonstrated by activated carbon and a new flow-through cation exchange resin exhibited excellent clearance of mAb aggregate with high monomer recoveries. A ten-fold improvement of mAb loading was achieved compared to a traditional cation exchange resin designed for bind and elute mode. High throughput 96-well plate screening was used for process optimization, focusing on mAb loading and solution conditions. Optimum operating windows for integrated flow-through purification are proposed based on performance characteristics. The combination of an all flow-through polishing process presents significant opportunities for improvements in facility utilization and process economics.     

Virus clearance validation across continuous capture chromatography

Multicolumn capture chromatography is gaining increased attention lately due to the significant economic and process advantages it offers compared with traditional batch mode chromatography. However, for wide adoption of this technology in clinical and commercial space, it requires scalable models for executing viral validation studies. In this study, viral validation studies were conducted under cGLP guidelines to assess retro- (X-MuLV) and parvo-virus (MVM) clearance across twin-column continuous capture chromatography (CaptureSMB). A surrogate model was also developed using standard batch mode chromatography based on flow path modifications to mimic the loading strategy used in CaptureSMB. The results show that a steady state was achieved by the second cycle for both antibody binding and virus clearance and that the surrogate model using batch mode chromatography equipment provided impurity clearance that was comparable to that obtained during cyclical operation of CaptureSMB. Further, the log reduction values (LRVs) achieved during CaptureSMB were also comparable to the LRVs obtained using standard batch capture chromatography. This was expected since the mode of virus separation during protein A chromatography is primarily based on removal during the flow through and wash steps. Finally, this study also presents assessments on the resin cleaning strategy during continuous chromatography and how the duration of clean-in-place solution exposure impacts virus carryover.