From the Editor: Drug Substance

This special summer issue serves as an “expression platform” for as many different industry voices as we could squeeze in between our front and back covers. To get even more points of view than our authors could provide, we used a reader survey. The results elucidated in this section begin to outline broadly the current working environment of some 200 readers who responded. Here, our discussion centers on drug-substance manufacturing. The introductions that lead the remaining sections expand that view to encompass drug-product development, advanced therapies, and business operations.

After our survey results, Enzene’s Himanshu Gadgil touts the potential for continuous production as a means to cut down manufacturing costs while maintaining biopharmaceutical drug-substance quality. Then authors from Cygnus Technologies (part of Maravai LifeSciences) feature an improved sample-preparation method for detecting host-cell proteins using liquid chromatography with mass spectrometry. And authors from Samsung Biologics describe three modular approaches for assisting drug sponsors in developing an investigational new drug (IND) focusing on speed, in-depth characterization, and process optimization.

Your Voice Here

BPI often makes a distinction between drug-substance and drug-product manufacturing. Much of our technical content presents extensive discussions of upstream-production and downstream-processing concerns. Thus it should come as no surprise that the reader survey we put together for this issue is weighted similarly.

Just over a third of our survey respondents are involved in upstream production of biopharmaceuticals; just over a quarter work in downstream processing. We summarize their answers below and thank them for their participation in this “expression platform.” Note that percentages are rounded off to the nearest whole number, and some questions allowed for “check all that apply.” Thus, not all percentages will add up to 100.

General Trends: Wondering whether some differences might be discovered, we asked a few questions of everyone regardless of their area of expertise. We wanted to compare the supply-chain concerns and experiences with advancing technologies between production and processing areas.

With the pandemic mostly behind us, what materials still are most affected by supply-chain concerns? Single-use components continue to be hard to come by. Many users seem to be encountering high prices and long lead times. Respondents observed particular difficulty with obtaining filters — e.g., for virus filtration, sterile filtration, and fill–finish. One respondent added that “single-use tubing (especially some reinforced silicone tubing) takes longer to receive.” And available materials are not always ideal for a given application: “Some single-use companies come out with offerings that are not fully tested and often are not made to needs.”

Our upstream-based readers reported continued supply-chain difficulties across the board, with many citing both cell-culture media and supplements (78%) and single-use components (67%) as the most problematic. Nearly half (49%) face difficulties with bioreactors, hardware, and control systems; over a third (35%) with filters; and nearly a third (31%) with cells and cell lines. When asked to identify the most problematic areas, respondents had a lot to say. Needs related especially to culture media and supplements (including bagged media) and spare parts for production hardware. One reader said that upstream requirements are “interconnected” because “all pieces must be available at the same time to start a campaign.” Considering variability in when materials arrive and in what quantities, some operational uncertainty lingers.

Respondents involved in downstream processing also face problems with filter availability, with a 63% majority citing such supply-chain concerns. Over half also highlighted difficulties with chromatography media/resins (59%), nearly half called out chromatography columns (41%) and single-use components (44%), and over a quarter reported trouble sourcing buffers (26%). When we asked which of those were most problematic, media and resins edged out filters for the top answer. Single-use components (especially tubing and connectors), membrane adsorbers, and viral-safety materials all were mentioned as well. Here, too, rising costs and missed delivery dates were concerns. And one respondent said, “Analytical kits are causing the most disruption to project timelines.”

Is process intensification (PI) a strategic goal? Most upstream respondents said yes, some only for new processes in development (36%) and others even looking at ways to improve legacy processes (30%). About a quarter of such respondents said that PI isn’t a key goal but is taken into consideration. Few told us that PI doesn’t apply to their modality (6%) or scale of production (2%).

On the downstream side, PI seemed to be even more important, with 40% of respondents applying it to new processes and 35% even working to improve legacy processes. Fewer here said it was considered but not a key goal (20%), and fewer still gave a flat no, with only 5% saying it doesn’t apply to their programs.

How much is your company leveraging artificial intelligence (AI), machine learning (ML), and so on in process development? Such technological advances seem to be more relevant upstream than downstream. Although half of production workers say AI/ML are not used at all, a quarter reported some use, and 8% reported quite a bit; 13% said their upstream groups were investigating the possibilities, and 4% even said that AI/ML already are used “a great deal.” Answers on the downstream side were a bit more subdued, with nearly two-thirds (63%) saying these technologies are not at all leveraged and no one reporting substantial use. Again, a quarter reported “somewhat,” but only 7% said “quite a bit” and only 5% reported investigating the possibilities.

How have automation and biomanufacturing 4.0 transformed your operations? Over a third of upstream respondents (38%) reported some implementation with improvements in efficiency; 16% reported unforeseen difficulties with the implementation. Over a quarter (28%) said that their upstream production areas use no automation at all. Few upstream groups have seen widespread implementation of biomanufacturing 4.0, with half of that minority reporting significant improvements and the other half facing challenges as a result. Only 6% of respondents said their companies are implementing full automation wherever possible.

In this area, too, downstream groups seem to be lagging some, with 30% saying that they’ve used no automation at all. But 15% reported widespread implementation, again half with improvements and half with unforeseen difficulties. Although 30% did report some implementation and improvements in efficiency, only 5% are are implementing full automation for downstream processing.

Upstream Concerns: We asked specific upstream-focused questions on topics such as expression systems, culture media, scalability, and perfusion culture.

Expression Systems: As has been the case for decades, mammalian cell lines continue to dominate biopharmaceutical production, with 80% of our survey respondents working with such systems. With 35% of respondents, bacterial expression edges out yeast fermentation at 24%. We were surprised to find 12% of respondents working with cell-free synthesis (more than are using transgenic plants and animals, insect cell culture, or plant cell culture), but that may be due at least in part to some companies making oligonucleotides and peptides.

There were few surprises when we asked about specific cell lines. Among mammalian cell lines, of course, Chinese hamster ovary (CHO) and human embryonic kidney (HEK293) cells predominated. Most bacterial systems are based on Escherichia coli, and the yeasts used are Saccharomyces cerevisiae and the methylotrophic Komagataella pastoris species formerly known as Pichia pastoris. Both Spodoptera frugiperda 9 and 21 insect cell lines are used. The only unexpected answer here was a mention of transgenic “low-alkaloid tobacco with an engineered plastome.” We’d sure like to see a technical contribution on that!

Media and Supplements: Interest continues to expand for serum-free, chemically defined, animal-origin–free, xeno-free, and proteinfree media, with upstream respondents listing those in order of importance. Of least importance were hydrolysates, serum, peptones, and extracts.

Scalability Challenges: When we asked about scaling production operations, we found that biological issues such as cell viability/productivity and cell adherence present the greatest challenges, as cited by over half of respondents. A third of participants pointed to technical issues related to engineering and availability of needed options, and just 15% reported business concerns over supply chains, vendor support, single sourcing, and so on. Those issues may be location dependent, with production in some regions restricted by logistics as well as government policies.

Perfusion and Continuous Production: A surprising majority of 52% said that they use perfusion some of the time, with a further 10% reporting use of it in most of their processes. According to a third of our respondents, the biggest challenge associated with continuous production is the large amount of culture media and supplements it requires. Filter fouling and cell productivity follow closely, with 23% and 21% citing those issues, respectively. Other concerns include cell viability and scale. “We typically limit perfusion to 500 L for manufacturability reasons,” one reader said. Another pointed out that “fed-batch allows more processes to come through the suite.” Others highlighted culture instability, regulatory compliance, and the need for “corresponding downstream process equipment or engineering” as limiting factors.

Downstream Themes: With most companies still uing fed-batch production, cell-culture harvest marks the point where downstream processing begins. When we asked about harvest, more respondents cited depth filtration as their method of choice (43%) than did centrifugation (31%). Among the few other options, only chromatographic clarification stood out. Only 12% reported using perfusion instead to straddle that line between upstream and downstream.

Chromatography: Of course, chromatographic purification remains the core of biopharmaceutical downstream processing. Indeed, most processes — probably reflecting the large number of monoclonal antibody products and derivatives in the research pipeline — are based on affinity and anion exchange, both of which figured into 78% of responses when we asked about technologies used. Other popular technologies include cation exchange (61%), hydrophobic interaction (54%), and multimodal chromatography (49%), with size exclusion lagging in use at 29%. Flow-through mode edges out bind–elute at 59% and 49%, respectively. That reflects and enables the slow trend toward continuous downstream processing, especially as over a quarter (27%) of respondents reported using multicolumn setups. That’s more than participants reporting use of monoliths, hydrophilic interaction, and “other” combined.

As for membrane adsorbers, most companies seem to be interested but have no immediate plans to switch over from column chromatography (35%) or are just at the stage of investigating options (25%). Just 12.5% said they’re already testing alternatives, the same number as those with no interest at all. About 15% are either implementing or already have membrane adsorbers in use — calling out by name Cytiva’s Mustang capsules, MilliporeSigma’s NatriFlo membranes, and Sartorius Sartobind products.

We asked about challenges and bottlenecks. Apart from chromatography, the most significant bottlenecks seem to come at harvest/clarification, at least for 32% of our respondents. That’s nearly twice as many as the 17% who cited buffer exchange, viral clearance, or filtration — and over six times those who highlighted viral inactivation (5%).

We were intrigued to find that product-related impurities outweigh process-related impurities in importance. Respondents cited both product variants (40%) and aggregates (22%) as more challenging than host-cell proteins (17%) and DNA (7%). And contrary to most fears expressed at the advent single-use technologies, leachables and extractables were cited by only 5%, along with culture-media components and metabolites.

Editors’ Perspective

In addition to presenting our survey results herein, we editors hope to apply what we’ve learned from them to our plans for content in the coming year(s). For example, we’ve brought you a lot of process-related impurities lately, but maybe we need to turn our focus more toward product variants and aggregates. We’d like to bring in some discussion of how to assess new technologies because a number of you seem to be doing that or will be embarking on such projects soon. And if there are best practices for handling supply-chain challenges, clearly we all need to find them. As you might expect, this is where you come in. If you have solutions and perspectives to share with your fellow readers, we hope that you’ll send them our way.