Intensifying Downstream Processes

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The biopharmaceutical industry is faced with the challenge of increasing efficiency and productivity to get needed medicines to patients more quickly and cost-effectively. Greater productivity and process efficiency are also required to increase capacities to meet rapidly growing demand for both traditional and next-generation biologics. Process intensification allows biomanufacturers to produce more product, often more quickly, using fewer raw materials and smaller equipment in less space. While there has been much focus on upstream process intensification, this approach can have significant impacts for downstream processing as well.

Many market drivers for intensification

As with any maturing sector, the biotech industry is on a journey toward increased efficiency and productivity, according to Natraj Ram, vice president of innovation for the BioProduction business of Thermo Fisher Scientific. “These efficiencies should translate directly to bringing treatments to patients faster and at lower cost. Further, due to the increased demand and growth of biologics, the need to improve efficiencies and productivity in biomanufacturing is greater than ever before,” he says.

Developments in upstream processes, including higher titers resulting from upstream intensification or continuous output from perfusion production bioreactors, are creating the need for greater efficiency and productivity downstream, notes Gunnar Malmquist, senior principal scientist with Cytiva. In addition, he observes that the current competitive landscape with multiple drugs targeting the same therapeutic modality and increased biosimilar competition are driving the need for improvements in process economics that can be achieved via intensification.

Other drivers for downstream process intensification outlined by Malmquist include the personalized medicines trend and the increase in development of drugs targeting smaller patient populations, both of which typically require smaller volumes and thus smaller production batches. Process intensification is also often key to improving the suboptimal processes used to produce clinical batches of new therapeutic modalities in the rush to be first on the market.

Malmquist concludes: “Today’s diverse biologics pipeline increases the need for a smaller footprint and the need for multi-product facilities in order to achieve high efficiency and product throughput.”

Downstream processing challenges

Downstream operations in bioprocesses are challenging because of the extreme complexity of the mixtures to be purified. “Crude solutions contain a very high number of impurities, some of which are very similar to the product,” observes Lucrèce Nicoud, head of product portfolio for Ypso-Facto. In addition, advances in upstream processing have shifted the bottleneck in biomanufacturing to the downstream, which she says now accounts for the greatest portion of biopharmaceutical production costs.

“Changing the current state of downstream processing is imperative,” adds Martin Lobedann, a process technology consultant at Sartorius. Downstream bottlenecks in cost, time, and required operational area can be attributed to higher buffer consumption and the associated increased demand for floor space. Non-value-added activities such as column packing and system cleaning also add to the downtime and increase the risk and operational area, while lower capacities and productivity across the purification steps, particularly chromatography, are additional issues.

Established protein-based biologics are further along in the journey toward efficiency, with next-generation biomolecules adopting these efficiencies as applicable, according to Ram. “Monoclonal antibody (mAb) processes have been around longer and have slowly matured as technology suppliers have had time to develop and improve tools that are fit-for-purpose. For these mature processes, there are opportunities for improvements coming from years of process, product, and operational knowledge,” he comments.

Newer modality processes, Ram says, are still evolving and can’t afford to wait years to mature, creating an immediate demand for fit-for-purpose tools and a greater openness for newer technology adoption. As one example, he points to mRNA as a modality for future vaccines, with the need to achieve efficiencies in order to deliver vaccines globally in a cost-effective manner.

Next-generation modalities face more basic challenges on increasing titers, yields, consistency, and reproducibility upstream before moving to more platform-based approaches, adds Ganesh Kumar, market entry strategy manager at Sartorius. That means intensifying downstream processes will be important and application of the current practices adopted in the mAb industry may be possible.

There are, however, different challenges to increasing the efficiency of downstream processing for protein-based biologics and next-generation biomolecules, according to Tania Pereira Chilima, CTO of Univercells Technologies. “For mAbs manufactured using single-use technologies, one of the key challenges is the capture step, particularly when titers are high.” For next-generation biomolecules such as viral vectors based on adeno-associated viruses (AAVs), she notes that there are capture chromatography options available which can comfortably cope with the titers achieved today; the challenges lie in increasing yields and separating full and empty capsids.

More than moving from batch to continuous processing

Process intensification is much more than simply moving from batch to continuous, contends Kilian Kobl, a project manager with Ypso-Facto. “Transitioning towards continuous technologies oftentimes creates an interface to other (batch) parts of the process, and mastering this interface is key to a successful implementation of continuous technologies,” he explains. In addition, he comments that there are activities such as reducing the number of buffers used in a process that are essential aspects of process intensification not linked to batch or continuous operating mode.

The perception that continuous downstream processing is the ultimate goal can be challenged, agrees Ioana Erlandsson, process design manager at Cytiva. “The best, most intense, solution is process- dependent and is at least partially driven by the upstream mode,” she states.

Several companies are working toward implementation of connected processing in downstream, typically involving a semi-continuous process flow from harvest to the end of the third chromatography step, according to Lobedann. However, he cautions that “the transition to a fully continuous downstream process still needs to be evaluated as one must consider the benefits versus risks this may present, especially if we are to consider steps such as virus filtration, where the business and safety risk posed by an integrity failure of the viral filter during continuous processing could be quite high.”

In general, adds Ram, continuous processing would not make sense if greater facility productivity in terms of higher kg/year given a certain size/scale or a reduction in the scale of the facility to reduce footprint and capital cost could not be achieved.

“The potential benefits of continuous processing in terms of productivity, efficiency, batch consistency, cost of goods, reduced footprint, and raw-material requirements are well documented; the literature is saturated with scientific and engineering analyses and demonstrations. Some challenges, such as automation, process analytical technology (PAT), equipment robustness, and a regulatory pathway, are still undergoing development and industry alignment. Ultimately, continuous adoption comes down to the business risk of doing something new and the required investment of time and money,” Ram continues.

Intensifying the capture step a primary focus

The purification of biomolecules by chromatography consumes about 1000 kg of eluent per kg of product, according to Yohann Le Guennec, a project manager with Ypso-Facto. “That is an enormous quantity and this process must be changed. Eluent consumption has direct implications in terms of cost, safety, and of course environmental impact. Therefore, downstream process intensification efforts should aim at reducing raw material consumption and the associated generation of wastes. Such greener, safer, and cheaper processes would also have smaller processing footprints and require reduced storage space,” he believes.

Intensification of the capture step would have the greatest impact, Lobedann agrees. “Application of current affinity-based resins in the market make it the most expensive step due to a lower productivity (<20 g/L/h) caused by a combination of low binding capacities and linear flow velocities due to diffusion limitations,” he explains.

Opportunities across all downstream unit operations

In addition to increasing the higher throughput and productivity of antibody capture, Ram says that process intensification and integration have applicability in many other aspects of downstream processing, ranging from integrated harvest and clarification of cell culture to intensification and integration of viral inactivation and anion exchange chromatography steps to buffer preparation and management.

Process intensification would have a major impact on the interface between the bioreactor and the first capture step, as this is where the highest volumes are being generated, moved, and processed, according to Chilima. “The use of integrated, automated, and continuous platforms for upstream and midstream processing, potentially in combination with continuous chromatography to collect and process the product-containing perfusate, would significantly ease operations as well as reduce the manufacturing footprint,” she remarks.

Further intensification of the downstream at the polishing and buffer exchange steps would also reduce footprint and processing times when compared with traditional approaches, adds Lobedann. For instance, Malmquist points out that flow-through polishing steps can be seen as process intensification compared to bind and elute processes.

In addition to achieving faster purification within each unit operation, there are other ways to improve the productivity of purification processes in terms of increased kilogram of protein produced per hour from a liter of bioreactor volume (kg/H/L), according to Ram. Among them he includes increasing the capacity of purification tools and reducing the number of unit operations or using a combination of the various solutions.

The buffer management (preparation, distribution, and hold) area is often overlooked, and intensifying here with inline buffer dilution would also be promising, observes Lobedann. “This approach would greatly reduce the auxiliary footprint through the use of smaller storage tanks with concentrated buffers that can then be diluted at point of use,” he says.

Many established intensification technologies

Approaches available today for process intensification include established technologies including multi-column chromatography, membrane chromatography, continuous virus inactivation, single-pass tangential-flow filtration (TFF), and real-time buffer production.

Switching to a modern, high-capacity resin will lead to process intensification in itself because doing so enables the use of a smaller column, notes Malmquist. Even so, multicolumn chromatography is a great tool for intensifying downstream processing, especially in the mAbs space, according to Chilima. These systems can be operated sequentially or in simulated-moving-bed mode. “The latter will enable users to increase the utilization of the resins, further intensifying their operations,” she explains. Continuous capture has additional benefits for perfusion processes with a continuous output from upstream, Erlandsson adds.

Rapid cycling chromatography with fiber membrane units is another approach that is attractive in low-demand situations with infrequent production where the production schedule does not allow full utilization of the lifetime of a resin, according to Malmquist. “This type of convectively driven chromatography leads to very high volumetric productivities and allows really short cycle times (minutes) and facilitates true single-use chromatography where the lifetime of the adsorber (more than 100 cycles) is consumed within one single batch,” he observes.

Rapid cycling can also be performed with resins packed in low-bed-height-columns that allow high flowrates without reaching the pressure limit, notes Malmquist. “While the diffusional limitations set a cap on how fast you can run, 20 cycles per day isn’t impossible,” he says.

Alternative chromatography media such as membrane adsorbers also can greatly reduce the required volume of adsorbents due to their high binding capacities when operated in a flow-through mode, which results in increased volumetric productivity and lower buffer consumption when compared to resins, Kumar comments.

In addition, membrane adsorbers when operated in a bind/elute mode (e.g., rapid cycling chromatography) in the capture step also offer advantages such as higher productivity and lower cost of goods for processes with lower annual demand by operating with a one-batch-one-membrane approach, according to Kumar.

Continuous virus inactivation and single-pass TFF (SPTFF), meanwhile, enable hold-free continuous processing, according to Ram. “Real-time production systems can significantly debottleneck facilities and reduce facility footprints and capital cost,” he contends. SPTFF, adds Lobedann, can reduce the cost and operational floor space required to perform concentration and buffer exchange in between unit operations or toward final formulation. “As the SPTFF units can lead to smaller units by omitting recirculation pumps and tubing, they can be integrated into existing systems and hence minimize non-value-added activities,” he explains.

In-line conditioning enables on demand in-line buffer formulation from single-component stock solutions. “The technology can either be integrated with a chromatography skid or used in an independent buffer producing unit, thus significantly reducing the footprint, as well as labor and time, needed for buffer preparation and storage,” states Erlandsson. She also notes that in-line conditioning allows adjustment of the effluent from one step to suit the subsequent step without the need for a mixing tank for both flow-through and bind-and-elute steps and is a good fit for multi-product facilities. Buffer prep skid technology, adds Ram, can dramatically reduce suite turnaround times and required process footprint.

Finally, Chilima points to more cutting-edge technology developments such as fully automated and integrated platforms that combine upstream and midstream processing. “Systems like the Nevoline platform from Univercells Technologies are built to enable the product to be continuously and automatically produced, clarified, and concentrated, thus reducing the processing volumes during further downstream processing steps,” she explains.

Various approaches to developing intensified solutions

Determining the best downstream process intensification strategies can be achieved in a number of different ways. Nicoud highlights three main approaches. The first is a fully experimental approach involving trial and error.

The second involves the use of mathematical relations and statistical models to correlate operating parameters with responses. This approach, Nicoud says, enables the reduction of the number of conditions that must be tested and is applicable to all types of processes, but suffers from a lack of predictive capability.

When mechanistic models are employed, the physicochemical phenomena (e.g., acid-base equilibria, diffusion in the pores, interactions with the chromatographic medium) are identified and described by a set of equations solved numerically. “This approach requires a certain level of understanding of the underlying separation mechanisms, but is extremely powerful,” Nicoud observes. “Once the model parameters have been determined, the model can be used to predict new conditions ‘outside the box’.”

Upstream impacts

It is important, stresses Malmquist, to look at the overall process rather than upstream vs. downstream intensification separately. There are, he notes, links between the upstream strategy and the need and/or possibilities for downstream intensification. Higher titers will reduce the loading time for the capture step and thus lead to shorter cycles, for instance. Whether the upstream process is continuous (perfusion-based) or batch (batch cell culture or perfusion with collection in a hold tank) will also have a strong influence on the downstream intensification strategy.

In addition to driving the need for downstream process intensification, high-titer upstream processes often are accompanied by higher levels of product variants and process impurities, which introduces additional challenges downstream, according to Ram. The nature and content of impurities has a dramatic impact on the purification process, Nicoud agrees. “It is key that upstream and downstream teams work hand-in-hand to identify together the trade-offs existing between the benefit of a high titer and the burden of a high impurity content,” she states.

Better design and control of upstream processes to reduce the types and amounts of impurities entering the downstream can lead to more efficient downstream processes, Ram comments. “Using quality-by-design approaches to upstream process development as well as process analytical technologies during development and manufacturing could also enable more consistent product quality and aid in the intensification of downstream processing,” he adds.

In addition, higher cell-specific productivity enables high titer processes without the need for high cell density cultivation, thus making clarification less complicated, according to Kumar. He also notes that using improved cell lines or early harvest of the supernatant can be beneficial for subsequent processing by lowering impurity and improving product-quality profiles.

Furthermore, Kumar suggests that stable intermediates, especially harvests, can enable connected processing or end-to-end continuous processing for higher resin utilization and overall downstream processing productivity in a smaller footprint, possibly lowering utility costs.

Along those lines, Chilima points to fixed-bed bioreactors (FBRs) that decouple cell culture media from the cells containing the product as enabling upstream and downstream process intensification. “These bioreactors can provide the equivalent output of 1000-plus-liter stirred tank reactors within vessels with volumes in the tens of liters because FBRs are operated at very high cell densities with the cells immobilized within a matrix,” she explains. For intracellular products, that reduces the volumes handled during downstream processing, and for extracellular/secreted products the bioreactor itself behaves as a cell retaining system. In both cases, she also points out that an FBR behaves as a filter, reducing the impurity load on the harvest bulk, which may reduce the size of clarification filters and reduce downstream purification requirements.

A role for single-use technologies

Single-use technologies (SUT) have a role to play in facilitating process intensification in the downstream. By allowing shorter change-over times, they deliver an “overall facility intensification,” according to Erlandsson. Low-risk product changeovers and avoidance of cleaning activities reduces the patient risk for contamination, Lobedann adds. Another benefit is flexibility for fast scale up or scale out and easy installation by simple connections, all of which are important for realizing process intensification. The ability to achieve closed processing, while not related to process intensification, is crucial for ensuring patient safety.

Recently introduced membrane technology for bind-and-elute rapid cycling chromatography is a true single-use solution that will, Malmquist believes, change the way we look at single-use chromatography. New options for chromatography that further increase the capacity per liter of columns and operating speeds, such as the next-generation technologies being developed by Astrea Bioseparations, will also be important SUTs for downstream process intensification, according to Chilima.

In addition to membrane chromatography, Ram highlights SPTFF as being valuable in process intensification. Chilima, too, sees TFF systems as being a primary example of how SUTs enable continuous processing, which she says magnifies the benefits of process intensification.

Modularization of single-use manifolds used in the design of each
specific downstream unit operation also offers end users a way to minimize the unique SKUs they must manage and a pathway toward an easier supply-chain transition to enable support of intensified processes, according to Ram. “Such modularization,” he says, “requires the adaptability necessary to adjust single-use manifolds to variations in tubing I.D. scales, processing pressures, or flowrates necessary to support these processes therefore breaks traditionally large manifolds into smaller,
functional elements that can seamlessly connect together using standardized single-use subcomponents.”

As with any technology, however, Nicoud stresses that there are pros and cons of SUTs that must be assessed rationally on a case-by-case basis. As a successful example, he highlights the EASY process developed by Sanofi (1). “This disruptive process works in full flowthrough with disposable technologies and has been shown to be a valuable alternative to classical mAb downstream processing for small numbers of batches,” she explains.

Software and automation technologies key enablers of intensification

Both advanced automation technologies and the software that enable them—as well as data collection and analysis
systems—are essential to successful process intensification. For instance, process intensification through continuous processing cannot exist without automation, according to Chilima. To enable a fully automated process, she adds, adequate sensing technologies, control loops, and data management technologies must be in place.

Integrated unit operations also offer benefits for traditional batch production, Ram observes. “By reducing touch points and manual intervention and introducing increased inline and at-line monitoring and control, it can reduce production risk, increase process knowledge, and help improve process control,” he comments. PAT and integrated data analytics tools, agrees Kumar, play an important role in an intensified process by measuring and predicting critical process parameters as well as allowing control/correction as required to ensure product quality in an individual unit operation.

In addition, PAT and data analytics tools with a plug-and-play hardware/automation interface are a basic requirement for connected/continuous processes and set the foundation for implementing ‘smart,’ autonomous, data-driven manufacturing that would involve digital twins, review-by exception, and real-time release, Kumar remarks.

As a specific example, Malmquist highlights the transfer of mechanistic chromatography modeling from an academic exercise to industrial practice, which allows simulation of different concepts that directly impact downstream process intensification efforts. Integration of PAT sensors, meanwhile, will enable more intensive downstream processing by maximizing loading or elution pool definition.

Ram cautions that although more companies are investing in automation, the industry has yet to establish a platform approach or best practices for integrated unit operations. He does expect the industry will align on a preferred approach to integrated unit operations as automation and the use of PAT increases, making this a standard practice for biomanufacturers and helping reduce one of the barriers to continuous adoption.

Outside of direct impacts on processes, Kobl emphasizes that software can also facilitate communication and collaboration between the many people involved in the development of intensified processes. “Software tools can be extremely valuable to ease communication between stakeholders, in particular through the structuration of data to ensure the completeness and reusability of the information through various services and functions,” he says.

Still many hurdles to overcome

Achieving process and operational intensification in a general sense will be challenging. Le Guennec notes that process intensification cannot occur unless companies are willing to accept change, and in such a risk-averse industry, the reluctance to adopt new technologies and methodologies may be a great hindrance to implementation of downstream process intensification solutions.

For those companies that are interested, a lack of awareness regarding the tools and methods needed to guide management in the selection and evaluation of the right process intensification strategies for both upstream and downstream processing is one of the greatest hurdles hindering adoption, according to Kumar.

A lack of standardization of applicable technologies is another key issue, Ram contends. “Typical processes employ technologies and systems from multiple vendors, and attempts at intensification are designed around stitching together otherwise individual batch processes. These two factors limit the efficiencies that can be gained,” he explains.

In fact, to be really effective, additional process development effort may be needed for continuous chromatography and other process intensification activities, and in some cases investment in new manufacturing equipment might be required, which could impact process transferability due to facility-fit issues, according to Malmquist.

Some of the technologies employed for process intensification, Erlandsson adds, also come with an increased complexity, both from a technical/equipment perspective and from a perceived regulatory aspect. It is important, therefore, to accurately assess the operational and business value of technologies used for process implementation, according to Ram. “While the technology itself may be attractive, the implementation might not be palatable or adoptable from a business standpoint,” Ram states.

In addition, having a clear view on the strategy for automation will greatly enhance the ability to streamline downstream processes, Ram believes. Similarly, standardizing how key process indicators and critical processes parameters are managed is an important step for intensification.

Kumar recommends that drug manufacturers work with total solution providers with significant exposure in this area and use decision-making tools such as cost modeling (return on investment, total cost of ownership), conceptual design/process modeling, and application trials/development. Le Guennec agrees that process simulation may be a valuable tool for helping companies think “outside the box” and evaluate process alternatives digitally, thus mitigating the risks before actual implementation.

A valued approach to improving bioprocessing

Despite the challenges, there is growing recognition that process intensification offers a means for improving productivity and efficiency across both upstream and downstream operations. “Process intensification is by essence the willingness to improve existing processes. Due to a constant pressure to develop cheaper, safer, and greener processes, intensifying processes will always remain of major importance for the industry,” Kobl insists.

Lobedann notes that if process intensification is defined as a holistic framework to increase overall productivity of unit operations, the manufacturing process, or the facility output for biomanufacturing, then according to BioPlan Associates’ 17th Annual Report and Survey of Biopharmaceutical Manufacturing and Production (2), approximately 56% of the biopharma industry is already actively or informally evaluating unit operation-based process intensification with approximately 18% considering possible use of connected/continuous bioprocessing technologies in downstream processing. “This percentage will grow further once molecules manufactured through successful implementation of process intensification in the downstream have received regulatory approval and reached the market,” Lobedann avers.

Ultimately, Ram believes that process intensification, integration, and automation are all efforts to improve biomanufacturing efficiency that will become the norm, especially with established biotech players and, to some extent, with contract development and manufacturing organizations. “Many companies—biotechs, technology suppliers, software and automation vendors—are working hard on making this a reality,” he concludes.

References

1. Prouzeau et al, BioPharm International, 34 (1), 26-30 (January 2021).

2. BioPlan Associates, 17th Annual Report and Survey of Biopharmaceutical Manufacturing and Production, BioPlan Associates, Rockville, MD April 2020, www.bioplanassociates.com/17th.

About the author

Cynthia A. Challener, PhD, is a contributing editor to BioPharm International.

Article details

BioPharm International
Volume 35, Number 4
April 2022
Pages: 10–15

Citation

When referring to this article, please cite it as C. Challener, “Intensifying Downstream Processes,” BioPharm International 46 (4) (2022).