Investigation of single-pass tangential flow filtration (SPTFF) as an inline concentration step for cell culture harvest

A modular and multi-functional purification strategy that enables a common framework for manufacturing scale integrated and continuous biomanufacturing

Biopharmaceutical manufacture is transitioning from batch to integrated and continuous biomanufacturing (ICB). The common framework for most ICB, potentially enables a global biomanufacturing ecosystem utilizing modular and multi-function manufacturing equipment. Integrating unit operation hardware and software from multiple suppliers, complex supply chains enabled by multiple customized single-use flow paths, and large volume buffer production/storage make this ICB vision difficult to achieve with commercially available manufacturing equipment. Thus, we developed SymphonX™, a downstream processing skid with advanced buffer management capabilities, a single disposable generic flow path design that provides plug-and-play flexibility across all downstream unit operations and a single interface to reduce operational risk. Designed for multi-product and multi-process cGMP facilities, SymphonX™ can perform stand-alone batch processing or ICB. This study utilized an Apollo™ X CHO-DG44 mAb-expressing cell line in a steady-state perfusion bioreactor, harvesting product continuously with a cell retention device and connected SymphonX™ purification skids. The downstream process used the same chemistry (resins, buffer composition, membrane composition) as our historical batch processing platform, with SymphonX™ in-line conditioning and buffer concentrates. We used surge vessels between unit operations, single-column chromatography (protein A, cation and anion exchange) and two-tank batch virus inactivation. After the first polishing step (cation exchange), we continuously pooled product for 6 days. These 6 day pools were processed in batch-mode from anion exchange to bulk drug substance. This manufacturing scale proof-of-concept ICB produced 0.54 kg/day of drug substance with consistent product quality attributes and demonstrated successful bioburden control for unit-operations undergoing continuous operation.

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.

Concentration of clarified pool by single-pass tangential flow filtration to improve productivity of protein A capture step: Impact of clarification strategies

Protein A capture chromatography remains a high-cost and relatively low-productivity step for downstream processing of monoclonal antibodies. As bioprocessing transitions toward intensified processes, maximizing the efficiency of individual steps is key to achieving economic targets. This study was performed to assess the impact of inline concentration of clarified cell culture fluid (CCF), using single-pass tangential flow filtration, on protein A chromatography purification productivity. CCF with varying levels of impurities and turbidity were obtained dependent upon the clarification method. These CCFs were concentrated and processed over a protein A capture step. Productivity increases of 1.8- to 2.6-fold were achieved as compared to a protein A capture step with no CCF concentration. Achieving such targeted improvements requires careful consideration of the multiple components in the clarification strategy before implementation.

Impact of ethanol on continuous inline diafiltration of liposomal drug products

Liposomal drug products are playing an increasing role in the field of drug delivery. With this increased demand comes the need to increase the capabilities and capacity of manufacturing options. Continuous manufacturing techniques present a significant opportunity to address these needs for liposomal manufacturing processes. Liposomal formulations have unique considerations that impact translation from batch to continuous process designs. This article examines aspects of converting to a continuous design that were previously viewed as inconsequential in a batch process. The batch process involves the removal of ethanol (EtOH) through tangential flow filtration (TFF). EtOH was found to reduce the permeability of the hollow fibers used for TFF. This effect was determined to have minimal impact on the overall batch process design but considerable influence on the design of continuous TFF such as inline diafiltration (ILDF). Using a pilot scale setup, EtOH was found to decrease permeability in an inverse manner to EtOH concentration. Further assessment found that dilution of the EtOH levels prior to diafiltration can significantly reduce the amount of ILDF stages needed and that a continuous design requires less buffer to the commensurate batch design.

Single-Pass Tangential Flow Filtration (SPTFF) of Nanoparticles: Achieving Sustainable Operation with Dilute Colloidal Suspensions for Gene Therapy Applications

Recent approval of several viral-vector-based therapeutics has led to renewed interest in the development of more efficient bioprocessing strategies for gene therapy products. Single-Pass Tangential Flow Filtration (SPTFF) can potentially provide inline concentration and final formulation of viral vectors with enhanced product quality due. In this study, SPTFF performance was evaluated using a suspension of 100 nm nanoparticles that mimics a typical lentivirus system. Data were obtained with flat-sheet cassettes having 300 kDa nominal molecular weight cutoff, either in full recirculation or single-pass mode. Flux-stepping experiments identified two critical fluxes, one based on boundary-layer particle accumulation (J_bl) and one based on membrane fouling (J_foul). The critical fluxes were well-described using a modified concentration polarization model that captures the observed dependence on feed flow rate and feed concentration. Long-duration filtration experiments were conducted under stable SPTFF conditions, with the results suggesting that sustainable performance could potentially be achieved for as much as 6 weeks of continuous operation. These results provide important insights into the potential application of SPTFF for the concentration of viral vectors in the downstream processing of gene therapy agents.

Comparative Evaluation of the Performance of Sterile Filters for Bioburden Protection and Final Fill in Biopharmaceutical Processes

Sterile filtration processes are widely used in the production of biotherapeutics for microorganism removal and product sterility. Sterile filtration processes can be applied to buffer preparation and cell culture media preparation in biotherapeutics processes, and to final sterilization or final filling in downstream processes. Owing to their broad range of applications in bioprocessing, various 0.2/0.22 μm sterile filters with different polymer materials (i.e., hydrophilic PVDF and PES) and nominal pore sizes are commercially available. The objective of this study was to evaluate two different commercial sterile filters in terms of filtration performance in various sterile filtration processes of biopharmaceutical production. The results demonstrate the importance of choosing the appropriate filter considering the process type and target removal/transport product to ensure efficient sterile filtration in the production of biotherapeutics.

White paper on high-throughput process development for integrated continuous biomanufacturing

Continuous manufacturing is an indicator of a maturing industry, as can be seen by the example of the petrochemical industry. Patent expiry promotes a price competition between manufacturing companies, and more efficient and cheaper processes are needed to achieve lower production costs. Over the last decade, continuous biomanufacturing has had significant breakthroughs, with regulatory agencies encouraging the industry to implement this processing mode. Process development is resource and time consuming and, although it is increasingly becoming less expensive and faster through high-throughput process development (HTPD) implementation, reliable HTPD technology for integrated and continuous biomanufacturing is still lacking and is considered to be an emerging field. Therefore, this paper aims to illustrate the major gaps in HTPD and to discuss the major needs and possible solutions to achieve an end-to-end Integrated Continuous Biomanufacturing, as discussed in the context of the 2019 Integrated Continuous Biomanufacturing conference. The current HTPD state-of-the-art for several unit operations is discussed, as well as the emerging technologies which will expedite a shift to continuous biomanufacturing.

Enhancing protein A productivity and resin utilization within integrated or intensified processes

Recent interest in continuous manufacturing of biologics has driven the development and evaluation of multicolumn chromatography systems to drive down resin costs by increasing productivity and maximizing resin utilization, especially for the expensive protein A capture step. Single-pass tangential flow filtration can be used to reduce the volume of perfusion harvest, enabling a further increase in the productivity of the capture step by up to fivefold. However, there are expected to be practical limits for the productivity of the capture step, which must be determined based on the manufacturing batch size, duration, and frequency, especially as it relates to efficient utilization of the column lifetime. For short fed-batch manufacturing campaigns, intensified capture processes may result in up to 82% lower resin consumption, while avoiding the long-term storage of used resin. For perfusion processes and longer fed-batch campaigns, it may be more efficient to operate at a lower productivity that enables the column lifetime to be routinely achieved and achieves the desired resin and buffer savings without introducing unnecessary process risk or complexity. An intensified batch capture process, "super-batch," will be compared as an alternative to multicolumn chromatography processes to achieve high productivity and resin utilization with a potentially simpler process.

Modeling flux in tangential flow filtration using a reverse asymmetric membrane for Chinese hamster ovary cell clarification

Tangential flow filtration is advantageous for bioreactor clarification as the permeate stream could be introduced directly to the subsequent product capture step. However, membrane fouling coupled with high product rejection has limited its use. Here, the performance of a reverse asymmetric hollow fiber membrane where the more open pore structure faces the feed stream and the barrier layer faces the permeate stream has been investigated. The open surface contains pores up to 40 μm in diameter while the tighter barrier layer has an average pore size of 0.4 μm. Filtration of Chinese hamster ovary cell feed streams has been investigated under conditions that could be expected in fed batch operations. The performance of the reverse asymmetric membrane is compared to that of symmetric hollow fiber membranes with nominal pore sizes of 0.2 and 0.65 μm. Laser scanning confocal microscopy was used to observe the locations of particle entrapment. The throughput of the reverse asymmetric membrane is significantly greater than the symmetric membranes. The membrane stabilizes an internal high permeability cake that acts like a depth filter. This stabilized cake can remove particulate matter that would foul the barrier layer if it faced the feed stream. An empirical model has been developed to describe the variation of flux and transmembrane pressure drop during filtration using reverse asymmetric membranes. Our results suggest that using a reverse asymmetric membrane could avoid severe flux decline associated with fouling of the barrier layer during bioreactor clarification.

Intensified Downstream Processing of Monoclonal Antibodies Using Membrane Technology

The need to intensify downstream processing of monoclonal antibodies to complement the advances in upstream productivity has led to increased attention toward implementing membrane technologies. With the industry moving toward continuous operations and single use processes, membrane technologies show promise in fulfilling the industry needs due to their operational flexibility and ease of implementation. Recently, the applicability of membrane-based unit operations in integrating the downstream process has been explored. In this article, the major developments in the application of membrane-based technologies in the bioprocessing of monoclonal antibodies are reviewed. The recent progress toward developing intensified end-to-end bioprocesses and the critical role membrane technology will play in achieving this goal are focused upon.

Continuous ultrafiltration/diafiltration using a 3D-printed two membrane single pass module

A 3D printed ultrafiltration/diafiltration (UF/DF) module is presented allowing the continuous, simultaneous concentration of retained (bio-)molecules and reduction or exchange of the salt buffer. Differing from the single-pass UF concepts known from the literature, DF operation does not require the application of several steps or units with intermediating dilution. In contrast, the developed module uses two membranes confining the section in which the molecules are concentrated while the sample is passing. Simultaneously to this concentration process, the two membranes allow a perpendicular in and outflow of DF buffer reducing the salt content in this section. The module showed the continuous concentration of a dissolved protein up to a factor of 4.6 while reducing the salt concentration down to 47% of the initial concentration along a flow path length of only 5 cm. Due to single-pass operation the module shows concentration polarization effects reducing the effective permeability of the applied membrane in case of higher concentration factors. However, because of its simple design and the capability to simultaneously run UF and DF processes in a single module, the development could be economically beneficial for small scale UF/DF applications.

Model-Based Design and Process Optimization of Continuous Single Pass Tangential Flow Filtration Focusing on Continuous Bioprocessing

In this study the Single-Pass-Tangential-Flow-Filtration (SPTFF) concept for continuous ultrafiltration in bioprocessing is investigated. Based on a previously validated physico-chemical model for a single ultrafiltration cassette, the transfer to a multistage SPTFF is predicted and validated experimentally by concentration steps for bovine serum albumin (BSA) and the monoclonal antibody immunoglobulin G (IgG) are compared. The model applied for the ultrafiltration membrane contains the Stagnant Film Model (SFM) for concentration polarization, as well as the Osmotic Pressure Model (OPM) and the Boundary Layer Model (BLM) for the mass transfer through the membrane. In addition, pressure drop correlations as a function of the Reynolds number are included to describe the development of the transmembrane pressure over the length of the module. The outcome of this study shows the potential to improve this multi-parameter dependent unit operation by a model-based optimization allowing significant reduction of experimental efforts and applying the Quality by Design (QbD) approach consistently. Consequently, a versatile tool for conceptual process design is presented and further application is discussed.

Economic Analysis of Batch and Continuous Biopharmaceutical Antibody Production: A Review

PURPOSE

There is a growing interest in continuous biopharmaceutical processing due to the advantages of small footprint, increased productivity, consistent product quality, high process flexibility and robustness, facility cost-effectiveness, and reduced capital and operating cost. To support the decision making of biopharmaceutical manufacturing, comparisons between conventional batch and continuous processing are provided.

METHODS

Various process unit operations in different operating modes are summarized. Software implementation, as well as computational methods used, are analyzed pointing to the advantages and disadvantages that have been highlighted in the literature. Economic analysis methods and their applications in different parts of the processes are also discussed with examples from publications in the last decade.

RESULTS

The results of the comparison between batch and continuous process operation alternatives are discussed. Possible improvements in process design and analysis are recommended. The methods used here do not reflect Lilly's cost structures or economic evaluation methods.

CONCLUSION

This paper provides a review of the work that has been published in the literature on computational process design and economic analysis methods on continuous biopharmaceutical antibody production and its comparison with a conventional batch process.