Master Class: Glutamine Dipeptides
New information and products to tune primary metabolism and improve performance in cell culture. Presenters: Dr. Melanie Schölzel & Dr. Christian Kessler
Michael Betenbaugh is Professor of Chemical and Biomolecular Engineering at John Hopkins University. He has had over 200 papers published in the field of cell culture and biotechnology beginning in the early 1990s with insect cell culture and glycoengineering and evolving to include mammalian biomanufacturing and metabolic engineering. Our expert Dr. Martin Schilling of Evonik Health Care interviewed Michael Betenbaugh about the most exciting advances in cell culture.
Martin Schilling: What are the major advances in cell culture that have impressed you most?
Michael Betenbaugh: I worked in insect cell culture for eight or nine years and then moved over to mammalian cell culture, which I've now been working on for 20 years. I have been impressed with how scientists continually improve the ability to increase the amount of therapeutic proteins that they can generate from these mammalian cell culture systems.
What has been most amazing to me is how by a combined effort of industry, academia, suppliers, the field has been able to continually push the product yields of monoclonal antibodies that you can get from CHO cells. When I first went into this field, I figured that people would have moved away from CHO cells and would be working on a bright new alternative, but it just hasn't happened.
To me, this has been the signature achievement of the biopharma field – our ability to take these little CHO cells and continually tweak them, optimize media and processes so CHO continues to outperform in vitro, for many products, all those other methodologies.
Another thing I'm surprised about is how quickly the concept of perfusion and continuous cell culture has bubbled back up. There was the evolution from batch to fed-batch, and now many people are trying perfusion cell culture and that's seeing a renaissance. The rise, and fall, and rise of perfusion cell culture is really fascinating to me.
Everybody is talking about mRNA and cell culture-based COVID-19 vaccines right now and monoclonal antibodies have also become quickly available in the fight against COVID-19. The speed of development has been amazing for all those biological drugs. What does it mean in terms of future developments and timelines?
The COVID-19 response has completely scrambled our entire vision of timelines. I think the development of the COVID-19 vaccines has shown that timelines can get even shorter. It has transformed the way cell culture development and processing will be done in the future resulting in even more compressed timelines.
Another aspect is how quickly groups were able to get monoclonal antibodies out and tested. My understanding is that some of the products were made using transient expression rather than going through the lengthy process of generating stable cell lines to get them faster in the clinic. This is an interesting approach to accelerate development.
When we look at vaccines, rapid development of cell-culture based vaccines has been achieved in the COVID19 context with timelines comparable to the mRNA-based products. We've been using eggs to produce vaccines for decades. The egg-based process is still going to be used for influenza, but for other vaccines in the future, it will be either mRNA- or cell-based and much more about platforms such as those used by AstraZeneca or Johnson & Johnson.
There's a huge role for us to play as cell culture people. The cell lines, the process, media, it's just a new vista for us to look at, not only in cell culture, but in terms of a wide spectrum of new modalities as well. It is an exciting time to be in biomanufacturing R&D.
How does academia react to those trends we're seeing, to the ever-accelerating rate of biological innovation?
We're moving into the area of cell and gene therapy, novel vaccines and much more. What are the engineering and production challenges that we can address from an academic perspective? What are the fundamental questions? How does metabolism change in gene and cell therapy platforms? How can we model these cells and their behavior in bioreactors? Academia is not competing with the industry to maximize yield and productivity but can provide answers to fundamental questions that involve these cells or processes for example.
That's what we're aiming at with our international academic-industrial collaboration initiative, AMBIC (Advanced Mammalian Biomanufacturing Innovation Center) to identify and answer the fundamental questions around these challenges in biomanufacturing.
Please tell us more about AMBIC. What makes it special?
AMBIC provides an opportunity for the community to come together as one ecosystem. You don't get that at meetings. Meetings are great for networking and finding out what people are doing in specific areas. AMBIC takes a completely different perspective by bringing together scientists from industry and academia as a community to identify common key challenges in cell culture and address those through collaboratively defined and funded research projects. By doing this, we address fundamental scientific questions that are highly application relevant and advance the field.
I've been around for 20-plus years but the level of insight we get into industry related challenges through AMBIC is unique. For example, challenges related to nutrient solubility, nutrient uptake, and media chemistry are of high interest to the community and we are working on projects to address these challenges, e.g. using dipeptides. On the other hand, industry members benefit from scientific excellence and the infrastructure provided by the universities. And they also get to learn what their colleagues at other companies think are the great challenges in bioprocessing going forward.
I think it has been and continues to be a really great experience for all members and we are currently preparing to go into the next funding round.
You have already addressed some of the challenges the industry is working on. Many of those are related to cell culture media. What role do you see ingredient suppliers and raw material suppliers playing?
Every company I talk to asks how can we make the media better to improve process performance? I still think there's a lot to understand about what the key additives are. What's a better way to provide nutrients to the cell culture? We must consider both the biological and the physical world. How do you provide these nutrients to cells in the best way so they can adapt to very high-density cultures?
What other additives are there to improve growth, productivity and reduce by-product formation? How can we meet the challenges around process intensification where we are dealing with physical solubility limits, for example?
I think the easy questions are answered. Now, we're looking for that special ingredient that's going to increase productivity by 10 percent, lower costs by 10 percent, or increase the quality of product by 20 percent. There's still a huge demand for that while we are still working to understand the rules of the “game” in terms of metabolism, thermodynamics, solubility, and kinetics.
I think the formulations of the media, how you put those combinations together, that's another important aspect. It's a great time to be a media and ingredient supplier, but you have got to be innovative.
How many of those fundamental insights gained in AMBIC regarding CHO cell lines and antibody production can be transferred to other cell systems?
If you're talking production cell lines like CHO and HEK, I would say 75 percent of the knowledge from CHO will be useful, but the remaining 25 percent will be more specific – different requirements for cholesterol, lipids, vitamins, and dipeptides, for example. I think that we already know there are differences, especially things around lipids and how they're used in terms of virus production versus protein.
When we're talking about cell therapies, there is still much more to understand, and the requirements will be different. Our understanding on how cells adjust between glycolysis and oxidative metabolism is going to be helpful, but knowledge-based media design is far less advanced.
Cell lines beyond CHO is also where AMBIC and others are headed. What are the differences regarding media, metabolism, quality attributes etc.? We are now starting to look closer into this with HEK cell lines and cell therapies.
What do you see happening in the next 10 years?
I think there will be less focus on optimization of CHO cells. We’ll move on to HEK cells, viral vector production and cell therapies like T-cells and perhaps others. We can generate a great knowledge base on these systems as well to better understand how to apply them. Nevertheless, people will continue to work on CHO systems, but on more specific topics like difficult to express proteins and bi-specific and tri-specific antibodies, for example. There will be many other biological systems coming up as we progress in this field. Hopefully, AMBIC can be involved in many of these initiatives.
Finally, I think there will be a much greater attention on sustainability in everything we do. There will be much more emphasis on where ingredients come from. Are you producing your raw materials, active ingredients and drug products in a more sustainable manner and can you prove this to customers, patients and society? I think not only costs, but sustainability will be a key driver. That's my crystal ball for the next 10 years.
Michael, thanks for your time and your insights!
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