New Reactor Technology Enables Larger Scale Manufacture of Fragile Cells

As the demand for larger amounts of stem cells and other fragile cells grows, biopharmaceutical companies are struggling with how to effectively produce these specialized biological materials in larger quantities. ATMI LifeSciences has developed a new reactor to meet that need. Product Director Matthieu Egloff spoke with the Pharmaceutical Sciences, Manufacturing & Marketplace Report about the special conditions required for the larger-scale production of fragile cells and how its new Xpansion reactor was designed to provide them.

A podcast version of the interview also may be found here.

Technology driversPharmaceutical Sciences, Manufacturing & Marketplace Report: Why is there is a need for special reactors that are suitable for the growth of cells and particularly for fragile cells. Also, what are the trends in biologic API manufacturing that have led your company to develop a special reactor system?

Egloff (ATMI): First, I will start by dividing or categorizing the cell-therapy market. There is a lot of noise today in the cell-therapy and emerging field, and it is a promising new therapeutic area. In these markets, you have different kinds of applications, but you have also different kinds of sources for cells and so have different products based on these cells.

From all of these kinds of cells, one that is today making a lot of noise is stem cells. You have different sources of stem cells, adherent stem cells and pluripotent stem cells. All of these stem cells are very fragile cells to grow and use, and the technology to cultivate these cells doesn’t really exist today, or at least in the last year, there were not many technologies able to grow these cells.

Because cell therapy is an emerging market, I think the main companies developing the biotechnology didn’t have the time to really get involved into this market and to develop the right technology. But, today, this dawn is changing, and biotech companies, such as ATMI, are now developing this specific bioreactor.

And I will say why we have to develop a new bioreactor. Before, most of the biotech production was based on cell lines, mammalian cell lines, for adherent cells, for example, and these cells were used for vaccine production or for protein production. In this case, you just need to grow the cells and you will use what will be secreted by the cells. There is not really a need to harvest the cells at the end of the process.

But with cell therapy, it’s completely different. Now, you will have to harvest the cells because the cells are the product. You have to grow the cells and then make sure to be able to get them. That’s the tricky point from a technology perspective, and from a biology perspective, these cells, the stem cells, for example, are very fragile cells, meaning that they are very sensitive to what we call the niche microenvironment. You really have to control this niche microenvironment to be sure that the stem cells that you will grow will behave as you want.

So that’s the reason that you have to develop a very specific bioreactor that will support the right growth for these cells.

Fragile cellsPharmaceutical Sciences, Manufacturing & Marketplace Report: What exactly makes the cells fragile, and what are the special requirements that are needed to be able to work with those cells?

Egloff (ATMI): The main reason that these cells are fragile is because they are very sensitive to what I mentioned before, to the niche microenvironment, meaning they are very sensitive to the physiochemical parameters of pH and dissolved oxygen, and they are very sensitive to shear stress. Also, different factors and parameters can, in fact, affect the differentiation of the cells. That’s something very specific to stem cells. The stem cells can differentiate into different lineages, so according to different factors, they can differentiate into one type of cell or another one. And that’s why it’s very complicated to cultivate these cells because you really need to [not only] grow them, but to drive them on the right path. You have to avoid differentiation, or at least avoid the differentiation you don’t want to have. That’s why you really need a system that will be able to control these niche microenvironments.

Pharmaceutical Sciences, Manufacturing & Marketplace Report: What are some of the special requirements that allow you to do that then in a reactor system?

Egloff (ATMI): The first one, if we are talking mainly about adherent stem cells, is to control the environment of the cells, so you will have to control the pH and you will have to control the dissolved oxygen level into your bioreactor. You will have also to control and to minimize the shear stress, meaning that you can’t use a bioreactor with high mixing and shear stress. You will have to protect the cells; that’s the main requirement you need.

And, of course, for the stem cells growing in adherence, you will have to provide a surface to help the cells to adhere to something, to the surface or the scaffold needed to preserve the stem cells and not leave the cells to differentiate into another type of cell you don’t want to have.

Bioreactor requirementsPharmaceutical Sciences, Manufacturing & Marketplace Report: Can you describe your Xpansion Bioreactor system and how you’ve incorporated these requirements? How it is different from a conventional reactor as far as the design and operation, and how does it fit in with the rest of the manufacturing operation?

Egloff (ATMI): Today, most of the cell-therapy companies, or the companies developing products based on stem cells and adjuvant stem cells, are using tissue-culture flasks or multi-tray vessels to grow these cells. And these companies, because they are in the early R&D phase, or in clinical and early clinical trials, are using multi-tray stacks. These technologies have been used in the market for a very long time. They are robust, and these technologies—the tissue culture flask and the 2D and multi-tray stacks—are what we can call planar technology, meaning a 2D surface, a plate surface, and plastic. A cell-therapy company has to scale up the process, but it’s just impossible to have a commercialization process based on a tissue-culture flask or multi-tray stack technology because with this system, for the controls, you have to operate the system with manual operation and you have to operate the system under very aseptic conditions. There is a lot of risk to continue to use these technologies for high-volume manufacturing at the commercialization stage. Most of these cell-therapy companies have to develop and to scale up these small scale processes. For them, the main requirement, of course, is to be able to preserve the cell’s integrity, identity, and potency.

Because the stem cells are very fragile, and because these companies have developed the cells onto a 2D surface, a plastic 2D surface, they have to keep the same kind of microenvironment. Again, still for the same purpose, to preserve the sensitivity.That’s why, at ATMI, we developed something very similar to what people are used to using. We developed a multi-plate bioreactor, and that is unique on the market today. There is no other multi-plate bioreactor. We have really compacted the design of a multi-tray stack to keep the same philosophy. We continue to use a 2D surface and with plastic. We are using the same polystyrene material as in multi-tray stacks or tissue-culture flasks, and we are using the same kind of surface treatment. Thanks to that, we are really providing to the cells the same kind of environment as in a tissue-culture flask or in a multi-tray stack.

That is the first innovation we brought—to really compare the design. In a typical multi-tray stack, you have a lot of space between two plates, and with the design of Xpansion, we really succeeded in avoiding the space between two plates. Turning to a multi-tray stack, you have a space between two plates of about 16 mm; with Xpansion, we have only 1.6 mm between two plates. We also succeeded in reducing the thickness of the plate; it is about 3 mm in the multi-tray stack, and with Xpansion, we have only 1 mm of thickness for the plate. Thanks to that, we really compacted the design, and with one Xpansion bioreactor, that’s the name of the bioreactor, Xpansion, with the Xpansion bioreactor with 200 plates in only one device, it is equivalent to 20 multi-tray stacks.

To give you an idea, a 10 multi-tray stack is about 4 meters high, and the Xpansion with 200 plates is below 1 meter high. It has really decreased the footprint, but it’s also decreased the number of operations because you don’t have to manipulate 20 devices; you only have to manipulate one device.

That was the first innovation—to keep the same kind of material, to preserve the niche microenvironment, and to compare the design. The second point was to add all the advantages of a bioreactor, meaning the capacity to control pH, to control the dissolved oxygen, inside the bioreactor. We also have another feature, the capacity to observe the cells inside the bioreactor. We have a specific microscope that helps us to observe the cell density and the cell confluency inside the bioreactor.

The main value of this bioreactor is to help our customers to switch easily from multi-tray stacks or tissue-culture flasks into a bioreactor system. Thanks to that, they are able to scale up the process. Then, of course, they are able to improve the safety of the process because it’s a closed system. They also are able to decrease the cost of goods because you minimize the number of operations. You need less operators to operate the system, and they are able also to decrease the investment cost. Because, thanks to the system with the bioreactor, you will minimize the number of incubators that are required, and you will minimize the number of laminar flow hoods that are required with the previous technologies.

Because the bioreactor can be operated in a closed system, you will be able to work in a Class C environment, so you will definitely minimize the size of your facility, and the class form environment of your facility. Again, you will decrease the investment cost.

Future developmentsPharmaceutical Sciences, Manufacturing & Marketplace Report: Are you working on further developments for fragile-cell manufacturing? Are you looking to improve the reactor or introduce any other technologies that would be of benefit?

Egloff (ATMI): Yes, definitely, because we think that Xpansion is a great technology to help our customers to move from the R&D process to clinical production, and then to start to have early commercialization or mixed-scale commercialization of production and sales. But, some companies will have to produce a huge number of cells per cell batch, and for this kind of process, we are evaluating what can be the next generation of bioreactors for stem-cell production of very, very large numbers of cells.

For that, there are two main options today that we are evaluating. The first one is microcarriers, and it’s very difficult to grow stem cells on microcarriers for different reasons, but one of them is mainly the shear stress on the cells and how to guarantee seeding of the microcarrier and so on, and how to scale up a microcarrier-based process.

For that, we have a specific bioreactor at ATMI that has a specific and very low shear stress, thanks to a very high mixing efficiency. It’s a PadReactor, and it’s based on a patented mixing technology. That’s one method we are exploring—the use of microcarriers and this bioreactor. The second option we are evaluating is to use what we call a 3D scaffold that provides a lot of surface for the cells into a small volume, and thanks to the 3D technology, we may be able to produce a very high number of cells in a very small bioreactor. Those are the kinds of technologies that we are today evaluating for the future.

Pharmaceutical Sciences, Manufacturing & Marketplace Report: Do you have any estimation on a time frame for when these technologies would be available?

Egloff (ATMI): Today, we have the PadReactor technology available. We have already a lot of data using this technology and microcarriers for viral production. We are working with the top vaccine producers in the world with these technologies, so this technology is used a lot. We now have to adapt the microcarriers for fragile cells, and we are now starting to assemble some partnerships to explore how to grow stem cells with the PadReactor technology. So, hopefully, in the next year, we will have good data to show to our customers regarding this technology. And for the 3D technology, it really depends on how we will push forward the development; the ongoing development is quite confidential today, so it is difficult to give you an answer on the second option.