Engineering Alternatives: Modern Technology Enables Expression System Developers to Think Beyond CHO Cells


Pichia pastoris yeast cells (

Major biopharmaceutical companies are teaming up with academics and the Bill & Melinda Gates Foundation to develop new biomanufacturing cell lines and methods. The project — known as the AltHost Consortium — is exploring innovative ways to produce biologics and vaccines for clinical usage in diseases from diabetes to cancer.

Lead researcher J. Christopher Love at the Massachusetts Institute of Technology (MIT) likens this precompetitive, open-access collaboration to the early days of the biopharmaceutical industry. “When biomanufacturing first emerged as a field, shared knowledge across laboratories was crucial for the development of new technologies, and everyone had a stake in the conversation. We are returning to that collaborative, innovative spirit we once shared, and we aim to enable new manufacturing solutions that offer both speed and volume.”

The biopharmaceutical industry relies heavily on Chinese hamster ovary (CHO) cells to produce biotherapeutics. This current state reflects early collaborative efforts to develop the technologies and systems needed to use CHO cells on an industrial scale. The Society for Biological Engineering’s CHO Consortium now works to characterize CHO cell genomes and develop tools for manipulating glycosylation processes toward the goal of enhancing product quality. Members of that consortium share research costs.
Using a similar approach, the AltHost Consortium will try to build a library of customizable, alternative (nonmammalian) eukaryotic cells such as yeast, fungi, and microalgae. Such organisms grow significantly faster than mammalian cells can, cannot harbor adventitious agents of concern, and could provide for more agile production processes with greater volumetric productivity.

The first candidate in the consortium’s sights is Pichia pastoris, a yeast originally found on chestnut trees that is now widely used in biochemical and biotechnology research. According to consortium member Daniel Degreif (laboratory head for molecular biology and strain development at Sanofi), P. pastoris has demonstrated a tenfold improvement over the standard method in volumetric productivity of monoclonal antibodies (MAbs).

“By expanding the expertise in using new expression hosts through our consortium work,” Degreif said, “we hope to help transform scientific knowledge and medical advances into next-generation cutting-edge therapies.”

A Virtual Roundtable
In March 2021, we caught up with three scientists to talk about the AltHost Consortium and its work.

J. Christopher Love is a professor of chemical engineering in the Koch Institute for Integrative Cancer Research at MIT and an associate member of the Broad Institute and the Ragon Institute. He holds degrees from the University of Virginia (BS, chemistry) and Harvard University (PhD, physical chemistry). Love worked in immunology at Harvard Medical School and Boston’s Immune Disease Institute and served as a distinguished engineer in residence at Biogen. A cofounder of OneCyte Biotechnologies, Honeycomb Biotechnologies, and Sunflower Therapeutics, he also serves as an advisor to Alloy Therapeutics, Repligen, QuantumCyte, and other companies.

Christina Alves is the head of cell-line development at Biogen, where her team focuses on developing, screening, and characterizing cell lines for programs in clinical development. In that work, she drives innovation to increase productivity and efficiency and develop next-generation cell lines for biologics production. Before Biogen, Alves worked at Genzyme, Chiron Corporation, and Johns Hopkins University. She holds degrees from Northeastern University (BS, chemical engineering) and Johns Hopkins University (PhD, chemical and biomolecular engineering).

Stephen Hadley is a senior program officer with the Bill & Melinda Gates Foundation. He provides chemistry, manufacturing, and controls (CMC) support in the vaccine development group for global health, focused on translational science and early clinical programs supported by the foundation that require a supply of recombinant proteins, MAbs, or viral vaccines. Previously Hadley was vice president of quality at CMC ICOS Biologics and small-molecule manufacturing at ICOS Corporation after spending time as a research chemist at NeoRx Corporation and the US Food and Drug Administration (FDA). He holds degrees from the University of Maine (BS, chemistry) and the University of Washington (PhD, organic and natural products chemistry).

All three interviewees started as chemists and have ended up working in biotechnology. We discussed how a fascination with molecular structure and function could lead to such a journey — with a little serendipity along the way. As analytical methods have advanced the industry’s knowledge about biologics, it has “become a bit more synthetic in nature,” as Love said. “Now we can approach biological problems much like a chemist would. For me, that’s the connection in these fields. My research team sits in a chemical engineering department, which applies lessons and ideas from chemistry to challenges such as new manufacturing practices. Our department at MIT has had a long history of thinking about bioprocess advances.”

An early expertise in organometallic chemistry took Hadley to biotechnology in the 1980s. From working in analytical science, he developed an interest in “taking advantage of cells rather than chemical reactors to make things.” And Alves followed a talent for math, chemistry, and physics through chemical engineering into early work at Genzyme, where she happily found a way “to make an impact on people’s lives by leveraging science.”

Origin Story
Scott: How did the AltHost Consortium come about?

Love: It started about two-and-a-half years ago formally, but the inception was well before that. I spent a sabbatical with Biogen in 2015, and even before that we’d been working (with a project funded by the Gates Foundation for a vaccine candidate and in separate projects funded by DARPA) on questions related to next-generation manufacturing for low-cost vaccine production.

Our approach has been informed overall by thinking about those kinds of scientific and technical intersections [mentioned above]. Today, with the kinds of technologies that exist to read and write genetics more directly, we can think about what advantages we might realize if we started over by asking, “How should we make better hosts for manufacturing the complex molecules that go into biopharmaceuticals and vaccines now?”

Scott: How difficult is it to get biopharmaceutical companies to share data these days?

Love: Actually, it’s been fun to get people to come to the table. We’ve reminded them that this is where they started in the 1980s–1990s, when they first looked at other manufacturing hosts such as Escherichia coli and CHO. There was great interest across the industry in sharing information to bring those forward because everyone benefits ultimately by being able to bring products to patients through the required regulatory pathways. Today there’s less experience with alternative hosts, so this is a way for us to share the latest science while learning how best to think about future manufacturing.

Alves: Biogen has been thinking about alternative hosts for a while, so it was natural for us to move into this model. We recognize that there is value in leveraging common technology to increase speed to the clinic and drive for lower cost of goods to enable therapies to reach all patients. The ability to advance things more quickly by working with others so that we can all access the same host is an advantage.

Therapeutic biomolecules are really what is of value; how you make them, that’s just a tool. For some of our partners, it took a little bit of a shift in thinking to collaborate in this way. We’ve all spent so many years building our processes and our systems. But I think the partners involved truly believe in the model that we’re using.

Scott: The reasons for the dominance of CHO cells are well known. But CHO expression systems are surrounded by a maze of intellectual property (IP). Can you discuss some of the other drawbacks?

Love: CHO cells are extremely productive, and they will be in the industry for a long time. We don’t intend to supplant them. We’re interested in bringing forth new types of products and addressing other challenges in biomanufacturing. The pandemic has highlighted cost, accessibility, and the speed of development. The consortium is studying how new hosts with fast doubling times can help enable new manufacturing processes that could address cost and speed — if engineered in the right ways.

Hadley: The speed of development has been remarkable in the context of the overall COVID-19 response. We have to give scientists and companies credit for doing fantastic work. However, the pandemic highlighted that recombinant proteins and antibodies for treatment are too expensive to have a global impact on the pandemic.

Another dimension is the problem of volume. Consider the global potential of the two antibody products with emergency use authorizations for COVID-19 treatment. If they were upscaled to match the combined annual output of all antibodies produced commercially today, the output would be far less than the potential need for COVID-19 therapeutic interventions. That output might cover a few high-income countries. So beyond cost, there’s a volume problem to consider particularly for antibodies. The foundation is interested in funding development of antibodies for other infectious diseases — such as human immunodeficiency virus (HIV), malaria, respiratory syncytial virus (RSV), and neonatal sepsis — for which lower cost of production potentially enabled by alternative hosts will be needed to make cost-effective interventions in our geographies.

Scott: The industry trend has been away from blockbusters toward personalized medicines. Now we have to turn around think at a huge scale. That must be quite a mind shift for many people.

Hadley: Fermentation systems can scale higher. The food, beverage, and chemical industries know how to ferment products at very large scales, several times larger than the largest CHO-based production technology.

Love: That’s an important point, this bifurcation in demand. There are products that require very large production, and increasingly then there are those that require very small production, so the ability to tailor and make all of them efficiently is key. Alternative hosts could increase flexibility in the kinds of molecules you can make for different products.

A Yeast-Based Expression System
Scott: Pichia pastoris is the first major focus for the AltHost Consortium?

Alves: Before the formation of the AltHost Consortium, Biogen partnered with MIT in a project partly funded by the Gates Foundation to work with Amyris, Inc., for its expertise in engineering of different microorganisms. Biogen historically has been very CHO oriented, but we were interested in exploring what other host options were available. We identified yeast, filamentous fungi, a diatom, and a parasite, then performed some head-to-head work to express antibodies. The data showed that yeast can leverage established tools to multiplex gene edits quickly and enable rapid success or failure (1). There’s potential with the other options, but Chris’s years of expertise with Pichia helped point us towards that particular strain for the consortium.

Love: There’s a strong regulatory track record of products made in this organism, which is not true for all alternative hosts currently. Millions of patients globally have received products from Pichia. The United States now has an approved MAb that has been produced in Pichia: Lundbeck’s Vyepti (eptinezumab). This strong track record of safety and efficacy makes it an ideal place to start.

At MIT, we’ve done a lot of work over the past few years in learning how to intensify and integrate steps in biomanufacturing while considering the role of the host in enabling change. One real benefit of CHO cells is that they secrete products into supernatant. That simplifies purification enormously. Yeasts do the same but without harboring adventitious viruses. That enables you to remove certain steps in your downstream processes. Pichia also has very few host-cell proteins (HCPs) — almost an order of magnitude fewer than CHO cells. That simplifies downstream processing too and can even minimize buffer use.

The pandemic has shown us that access to simple raw materials and manufacturing practices could be a future benefit for timely responses. The brewing industry, for example, uses a very simple feedstock. You would need a slightly more complex feedstock to produce MAbs, but yeasts can use a highly defined medium that is likely to be less complex than that for CHO cells.

Scott:Is the genetic engineering side simpler too?

Love: The world is so different now. Pichia has been around for a long time, and people have had different experiences with it — many good, some not. But with the tools we have now for reading and writing genomes — e.g., using clustered regularly interspaced short palindromic repeats (CRISPR) and advanced sequencing technologies — you can go in and, much like in chemistry, tailor a host that is fit for purpose. That’s really what’s different now. We can edit the genome with precision we want and for about $30 sequence the genome and see it work. It’s also important that the lessons the consortium is learning from Pichia about host biology and protein production will apply to other similar hosts (including CHO).

Scott: That’s very different from even 10 years ago.

Love: Absolutely. Looking back at the work then for glycoengineering, I think the vision and demonstration of what was accomplished with the technologies and tools they had available is remarkable. Today, with CRISPR/Cas9 technology, we can think about modulating quality attributes precisely to something appropriate for a biopharmaceutical product in many fewer steps than were required previously.

Scott: Yeast glycosylation has been a challenge.

Love: All microbes present glycans that are different from those our cells would express. What was really powerful about previous demonstrations by GlycoFi and other groups was their ability to remodel cells in certain ways. The combination of gene editing and sequencing is letting us now address challenges that can arise with such modifications (e.g., growth deficiencies and stability of some systems). We can learn directly from the host how it regulates certain pathways and convert that knowledge into new strategies for engineering the levels and regulation of specific genes to enable glycoengineering.

Scott: Many companies using microbial hosts have had trouble adapting their processes for disposable bioreactors, which have been limited in their thermoregulatory ability. Do you know of any recent advances that are changing the equation?

Alves: It’d be nice to have a more nimble and agile manufacturing strategy here, with smaller volumes. If you don’t need metric tons of material for a given product, then P. pastoris can work in disposable systems. I think we can leverage some interesting space designs with an open footprint and “pop-up” reactors for different products. A disposable setup could be really efficient and a nice alternative to a dedicated stainless-steel yeast plant.

Scott: Do yeast systems generate less heat than bacterial fermentation does?

Love: It depends on how you operate the system and how you feed the cells — like most things in bioprocessing. Heat generation of Pichia is driven by what it metabolizes, and historically methanol has been used for induction. Other challenges that have been pointed out before with this approach: Safe handling of methanol in large volumes can be difficult for some facilities. But this is another example of an exciting opportunity to reengineer the host and realize the same benefits of without requiring methanol.

Historically, you might have looked at only a couple of genes associated with that specific pathway because that’s what you knew to look at. If you wanted a gene, you had to go clone it yourself. Now we get to look at [whole genomes] and how genes correlate under different growth conditions, then propose and build strains with different or no methanol use at all. We can go completely methanol free. In fact, as part of AltHost work (publication pending), we’ve now created P. pastoris strains that operate completely methanol free and have been used in production facilities compliant with good manufacturing practice (GMP).

Scott: Beyond antibodies, what other kinds of products are we talking about making?

Love: That’s one of the fun things that we’ve gotten to explore with the consortium. COVID-19 provides a good reminder that we don’t know what kinds of products we might need next. We need to be able to make a range of different proteins and other products. MAbs clearly remain an important class, and vaccines and their components also will continue to be important. But other kinds of molecules include single-domain antibodies and all the protein-engineered classes of molecules that are antibody-like but have other features. Bispecifics are one example. These are all different classes that will require different understanding of how best to manufacture them. If we can make them with the right qualities, there may be an opportunity to identify fit-for-purpose hosts.

Scott: For what types of products is Biogen considering yeast expression?

Alves: Our main focus is on antibodies right now because we have a strong antibody-biologics pipeline, and they are well-understood molecules. As our pipeline expands to explore new formats, we would consider other novel classes for treating different neurologic disorders.

Scott: HCPs are another concern with microbial expression systems — well-known pyrogens in E. coli, for example. Can you discuss this aspect of the P. pastoris system?

Love: Pichia has fewer than 200 HCPs that you can identify in supernatants using mass spectrometry (MS). In combination with perfusion-based technologies that offer some degree of filtering, we have fluids coming out of some bioreactors in the lab that are 70% pure already. This is a very different starting point for designing a manufacturing process compared with culture fluids in which the product is just one of many proteins present, either because of cell lysis or just from the host secretome itself.
And those limited HCPs are not all essential proteins, so you can begin to reduce their number further through targeted gene knock-outs. In related work with Steve Cramer’s group at Rensselaer Polytechnic Institute a few years ago, we considered together how Pichia HCPs interact with different resins (2). There are differences in the overall biophysical characteristics of yeast HCPs from those of mammalian systems. These biochemical and biophysical differences offer other opportunities to think about orthogonal methods for separating them out from product classes that are designed to be fit for mammalian systems.

Alves: As we develop processes that are more intense with higher cell densities, we’re starting to see more and different HCPs. CHO cells secrete thousands of them, and different products have different “hitchhiker” proteins that come along with them through downstream processing.

From a regulatory standpoint, CHO is a very safe cell line given that it’s mammalian, and it has a proven track record. There may be some initial hesitation with something like Pichia because you will see different HCPs than you have traditionally. But with so many fewer secreted proteins, we should be able to characterize them effectively. HCPs are a critical quality attribute (CQA) in any regulatory framework, so there always will be a focus on demonstrating adequate clearance and good analytical characterization to ensure safety.

Scott: Yeasts have a stronger cell membrane — no, it’s a cell wall, right? So the cells aren’t easily lysed.

Love: That’s a benefit; it’s also a challenge, and it’s one that we’re thinking about now. If you want to diffuse out larger molecules, that does represent a physical barrier — speaking of chemical engineering principles. Understanding how to create better porosity through that structure without losing the benefit that we have on the process side of the robust cellular structure is an interesting challenge, one on which we’re actively working.

On the Horizon
Scott: What other expression platforms are under consideration for future work by the consortium?

Love: Many interesting hosts are out there, and a number of other companies are exploring them: e.g., filamentous fungi, algae, and parasites. One parasitic organism we looked at previously with Biogen makes a monoglycoformed sugar on its proteins. We can learn a lot of biology from these other organisms and think about how to bring in pathways for complex biological processes such as glycosylation and secretion into other hosts. These are all questions that we’re interested in expanding on as we gain traction and build successes with the early work that we’ve been doing together.

Scott: Who’s involved with the AltHost Consortium at this time? Are you still building membership?

Love: There’s been a lot of interest in what we’re building together. Historically, these types of hosts have been inaccessible, whether because of IP or business considerations. But with the tools available today for engineering them, it’s relatively straightforward to do this work for virtually any host and minimize those barriers to adoption. The biopharmaceutical industry is heavily regulated for the right reasons. And we need to have hosts that are well understood like CHO and E. coli and Saccharomyces. To that end, we’ve created what’s effectively an open-source platform for advancing alternative hosts to the consortium members. Currently we have Amgen, Biogen, Genentech (Roche), Pfizer, Sanofi, and the Gates Foundation as members. We’re seeking to grow and expand as we continue to advance this precompetitive landscape that we’re creating together.

Hadley: It’s important to highlight the intention of the consortium to provide strains to the American Type Culture Collection (ATCC) and other such nonprofit organizations. The open-access, precompetitive aspect is critical to the Gates Foundation. One strain already has been transferred to a foundation-funded partner to develop a low-cost COVID-19 vaccine for low- to middle-income countries (LMICs). That illustrates this important aspect of the consortium.

Scott: Will you be involving any of the smaller companies?

Love: We are excited and actively seeking to include smaller companies, including those that aren’t traditionally in the biopharmaceutical arena. We need to create a new, innovation-focused ecosystem if we are to solve the challenges of speed, cost, and flexibility in manufacturing. You mentioned the need for appropriate process equipment, for analytics to be able to characterize HCPs, and so on. Those are all important considerations for next-generation approaches.

Scott: Users and suppliers increasingly work together on new technologies and problem solving. Do you think you’ll get some suppliers involved?

Love: If you look at other consortia (e.g., for CHO) and programs such as the National Institute for Innovation in Manufacturing Biopharmaceuticals (NIIMBL), you see that there are good ways for different parts of the ecosystem to interact in the same space. As we look ahead to additional capabilities for future manufacturing, there is an opportunity for vendors that supply materials and equipment to participate. We are eager to engage them, too, as we continue to grow the consortium.

Scott: And with groups like BioPhorum, it seems that companies are finding ways to share information without compromising their own IP.

Love: Everyone faces the same challenge with these incredibly powerful new therapeutics. We still have to get them to patients, and that has to be through manufacturing. Ultimately, these new manufacturing technologies are needed if we’re going to increase flexibility and speed to market while also lowering costs and manufacturing at scale. CHO cells are highly productive for what they do, but there’s probably a limit to how much farther we can take them and realize those gains. So it’s important to establish a precompetitive state in which we can talk openly and advance the science now that is necessary to support future manufacturing.

Hadley: The Gates Foundation works with many vaccine developers and manufacturers to supply low-cost and affordable vaccines for LMICs. Large multinational vaccine manufacturers and developing-country vaccine manufacturers all make important contributions to the development and supply of vaccines to LMICs. The foundation also has funded development of several innovative manufacturing technology platforms with the aim of reducing production costs of vaccines and antibodies. Common to all those technologies is process intensification, with linked or continuous processing, low capital costs, and small manufacturing footprints.

Love: One of the great things about working with the foundation has been that connectedness to other parts of the manufacturing ecosystem, certainly through some of the work my lab’s done over the past year. We’ve had good opportunities to leverage a lot of learnings from the AltHost Consortium to help advance some ideas on new vaccine candidates for COVID-19.

Hadley: You’ve done a good job advancing several vaccine candidates that we hope to have a significant impact on these geographies. It’s a major part of the ongoing story.
Love: The world needs more pandemic vaccines well beyond the ones we are fortunate to have right now.

Streamlining Biomanufacture
Scott: Has the pandemic changed any ideas about what you’re doing or served to confirm any points you’re making?

Hadley: An interesting story is still emerging about supply disruptions — the scarcity of single-use technologies, for example. Think about how to layer onto an existing manufacturing infrastructure the demand for a world population of 14 billion doses of two-dose vaccines. On an already largely or even fully occupied biomanufacturing infrastructure, that’s a big challenge.

I recently read a World Health Organization report stating that the total global market of vaccines accounted for 5.5 billion doses in 2019 (3). Suddenly, with the COVID-19 pandemic, you’re trying to go from that volume to 19 billion doses of vaccine in a very short time. This is telling us that alternative flexible and adaptable platforms for multiproduct biomanufacturing facilities will be an important part of the solution for our next pandemic. It’s not going to bend the curve on the current one, but it’s something that needs to be thought about for the future. Alternative hosts, process intensification, and low–capital-cost and small-footprint facilities will be enablers for that.

Love: It’s important to start that process purposefully now because it takes time to build and qualify the facilities necessary to make vaccines. We have to start now on designing for modularity and flexibility. That intensifies the importance of what we’re trying to do with the AltHost Consortium. We need to work faster together than we had anticipated when we started three years ago.

Scott: Reproducibility and robustness always have been important, but that places new emphasis on reproducibility.

Hadley: Yes. The technology transfer burden is significant on the companies that innovated COVID‑19 vaccines. One company cannot make enough vaccine in its own manufacturing network to meet that 14-billion dose requirement. So there are many companies executing multiple technology transfers for a single product to increase output. That’s a huge effort. I would be less concerned if those were for antibodies, which are reasonably well platformed to enable fairly efficient technology transfers. But most vaccines use novel manufacturing technologies that are more complicated to transfer.

Love: As we start looking at the platforming aspects required, we need capabilities to make platform-like processes for proteins, messenger RNA, and all the different molecules that could be helpful in a pandemic situation. We want to be able to use those capabilities to make other products at other times, too. It’s a natural evolution that’s common in other industries, where they have shared resources or facilities to make basic components that are then used to create competitive products. The semiconductor industry, for example, shares manufacturing capacity on platforms, with different companies making their own products using those facilities.

Scott: That sounds like an interesting approach I’ve not heard many people talk about. Does Biogen have ideas in that area?

Alves: Not as of yet. We’re focusing on the antisense oligonucleotide space, which has manufacturing issues similar to those of mRNA. It’s not quite platformed, and most companies involved are small. Many modalities in the biopharmaceutical space would benefit tremendously from applying all we’ve learned with small molecules and biologics.

We have included several of our protein and small-molecule people to build the antisense group within Biogen. We’re doing the same thing with gene therapy, leveraging the expertise of the biologics team to complement the viral experience and build a platform. As novel modalities keep coming to fruition, we need to use that engineering mindset so we can make them at the scale we will need.

Scott: That brings up the subject of expression titers and protein yields. What kind of yields are you looking at with P. pastoris, and where do you see that going?

Love: It’s really about the productivity of a facility. Ultimately, how much of the raw materials do you convert into final product? Titer is one metric, but it’s really about volumetric productivity in a facility: grams per liter per day of purified product. And ultimately, how much space does it take to accomplish that? The bigger the facility, the less efficient you are at that same conversion rate.

Because Pichia doubles faster than CHO cells, you get an increase in volumetric productivity by using your facility more efficiently. In fact, one consortium member hosted an business from MIT who wrote a master’s thesis to find the break-even point. The student found that, with a 50% relative output in titer (compared with CHO), it is feasible to achieve the same costs of manufacturing with P. pastoris (4).

But then you get other benefits in process intensification. What if you could also eliminate the protein A capture step for antibodies? That could help address costs in downstream processing too. Then we could start to think about shrinking and intensifying the overall facility footprint further as well. Changing the host enables a holistic reconsideration of the whole manufacturing platform.

Scott: Getting rid of that step would be huge.

Love: In research on a nonreplicating rotavirus vaccine (NRRV) project we’ve done with the Gates Foundation — and in separate work funded by DARPA — my lab has studied a number of different molecules (5). We’ve produced at least 12 different ones in continuous-production perfusion systems with straight-through downstream chromatography (largely polishing). The purities are very high coming out of perfusion to start with, so we’re just removing things that are not the product.

There’s still optimization work to bring those to a commercial-ready process, of course, but our results suggest that it may be possible to think about simplified downstream strategies with Pichia. The reasons for this intensification are what we spoke about on the intrinsic features of P. pastoris biology: the low levels of HCPs and our ability to engineer away the ones that we don’t want. We can take a holistic mindset that integrates both parts of the problem. Our goal is to convert raw materials into vaccines or MAbs — so we often ask what we can simplify further when we have the totality of the process at hand to engineer. Historically, biomanufacturers couldn’t do that. It would be a handoff from one step to the next. Whatever a cell line made, the downstream group would have to figure out how to handle it. But we can do both now. And that changes the equation entirely.

Scott: I assume that process intensification is a major goal for most consortium members.

Love: Our focus at the moment is on the host biology itself. But there is an interplay among elements — e.g., getting rid of methanol or knocking out HCPs — that are derived intrinsically from that biology and can benefit the overall process. As we think about process intensification, it is about increasing specific productivity of those cells and being able to sustain them through the right metabolic processes to keep them going.

Alves: Getting rid of protein A would be fantastic. Another costly operation is viral filtration. We’ve found that 70% of our drug-substance manufacturing cost comes from downstream processing, and that’s where we especially expect Pichia to help by driving down purification costs.

Obviously, we want to intensify the process and improve our yields however we can. Starting with the right organism engineered in the right way will make a big impact. With CHO, we tend to pull a lot of process levers that maybe we won’t have to if the organism is built correctly and holistically. And I think Chris’s lab is doing a great job of thinking through all those aspects that we want to put in up front to simplify things downstream.

1 Jiang H, et al. Challenging the Workhorse: Comparative Analysis of Eukaryotic Micro-Organisms for Expressing Monoclonal Antibodies. Biotechnol. Bioeng. 116(6) 2019: 1449–1462;

2 Timmick SM, et al. An Impurity Characterization Based Approach for the Rapid Development of Integrated Downstream Purification Processes. Biotechnol. Bioeng. 115 (8) 2018: 2048–2060;

3 MI4A. Global Vaccine Market Report. World Health Organization: Geneva, Switzerland, December 2020;

4 Coleman EM. MBA Thesis: Establishment of a Novel Pichia pastoris Host Production Platform. Massachusetts Institute of Technology: Cambridge, MA, May 2020;

5 Crowell LE, et al. On-Demand Manufacturing of Clinical-Quality Biopharmaceuticals. Nat. Biotechnol. October 2018;

Gareth Macdonald is a freelance contributor to BioProcess Insider, and corresponding author Cheryl Scott is cofounder and senior technical editor of BioProcess International, both part of Informa Connect; 1-212-600-3429; [email protected].

The introduction of this article is adapted from Macdonald’s online article:

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