Finding That Special Source

I joined Sigma-Aldrich (now MilliporeSigma) in 2002 as an R&D manager in molecular biology product development, before moving into cell culture media in 2006 and then through several roles to my current position. Looking back, it’s amazing to see how far the field has come in just 15 years.

When I entered the cell culture media space, monoclonal antibody titers were around a gram per liter or less; today, we see titers as high as 10–12 g/L range. Redesign of cell lines, cell culture media and advances in bioprocessing technology have both been crucial to this huge boost in productivity. In 2006, the industry was still using serum for many processes. Since then, we’ve progressed from formulas using non-defined complex components, i.e. full serum, to reduced serum amounts, to a variety of plant-derived hydrolysates, to the use of formulas with much more chemically defined ingredients.

Perhaps the biggest change is our approach to fed-batch processes, both in terms of media and feed design. In the early days, the cell culture media had most of the components needed for cell growth; today, the “basics” are included, and the rest of the components are fed into the process on a regimented basis, providing the nutrients the cells need, and, crucially, when they need them. In essence, we are now able to direct the cells to protein production rather than just increasing cell density – a common goal of the past, when the theory was more cells equal more protein. That’s really not the case, and so we’ve had to learn how to drive specific productivity of individual cells, which is not always an easy task, especially when put into the context of secreting a high amount of a recombinant therapeutic protein that is not a natural part of the cells’ architecture! To succeed, we, as an industry, have needed to increase fundamental knowledge of the biochemistry of the cell lines used.

Critical raw material quality

Modern cell culture media are typically made up of anything between 50 to 80 components (although some commercialized therapeutics are grown in cell culture media comprising over 100 components). Each component comes from a particular source – and they also come with a particular “risk”. All cell culture media manufacturers must consider those risks, as well as the potential of those risks being passed onto customers. There are two risks which perhaps concern drug producers:

1. Viruses. Is there any chance of inadvertently introducing an adventitious agent into a process? Some may recall the Vesivirus 2117 contamination incident at Genzyme’s Allston Massachusetts plant in 2009 – resulting in millions of dollars in lost revenue from delays to Cerezyme and Fabrazyme production and, more importantly, interruption to the supply of life-saving medicines to patients.
2. Process variability. Individual raw materials originate from diverse sources – mining, complex chemical synthetic routes, and so on – and each one, put simply, must be what we think it is; for example, sodium chloride should consist of sodium chloride and only sodium chloride. Invariably, however, impurities or manufacturing intermediates creep into play. These impurities and/or manufacturing intermediates can have an effect on cell culture and can be a source of process variability.

In the past, the industry never really understood much about the variability of impurities or the biological significance. Over the last four or five years, companies have started to more fully understand the implications of lot-to-lot variability, impurity profiles, and any trace elements that may be present. Some of those trace elements can have a strong impact on CHO-cell enzymes; copper at ppb levels, for example, can activate enzymes that actually alter the critical quality attributes of the resulting therapeutic (1). Consider a pharmaceutical company that is trying to match a certain quality profile filed in its IND material; the company could be hindered by the process variability introduced by trace level copper in a raw material. Likewise, consider a biosimilar developer trying to match an originator profile. In both cases, reducing process variability is essential, which necessitates fully characterized starting materials.

Controlling variability

There is a multiplicity of raw material vendors (including MilliporeSigma – although in fact, we are one of our own biggest suppliers when it comes to our cell culture media business). For any cell culture media manufacturer, establishing a robust supply chain is absolutely key. Such supply chains can only be built with time and trust. The credibility of individual suppliers stems from good and effective validation and quality systems, especially in terms of change notification (after all, a seemingly small process change at the start can have big consequences in the final application). A robust supply chain often necessitates multiple suppliers of qualified materials to maintain continuity.

But, importantly, if there is variability, we need to be able to measure it – and understand the potential impact. Going back to my copper example: for one client, trace level concentrations of copper may actually be beneficial by providing the right level of glycosylation. For another client, the glycosylation profile may be affected detrimentally. What does this mean? Firstly, we recognize how essential it is to accurately report copper levels. Secondly, universal specifications are only useful as a starting point. Customers may have some idea of how copper affects their process, but we often have to work side-by-side with them to develop a custom solution.

Room for research

Back in 2009, we put together a research and development team dedicated to raw materials, which focuses on the biological and analytical characterization of all the compounds used in our cell culture media. The team strives to answer some pretty fundamental questions about those compounds. Why does a particular compound need to be there – or, in other words, what is its biological function? In bioprocessing, we’re essentially taking cells out of their native environment and forcing them into a new role in therapeutic drug production – so there’s a lot of opportunity to remove components that we no longer need. Perhaps selenium is simply there because “we’ve always done it that way!” (You can actually learn something about the taxonomy of media design simply from where people went to grad school...) The team is also investigating the levels of impurities from lot-to-lot and from vendor-to-vendor – as well as the biological impact of those different levels of impurities.

When it comes to understanding the impact of cell culture media, we shouldn’t be passing the responsibility onto our clients – we believe that we, as a supplier, must drive that research. And our R&D team allows us to become raw material masters! Once we started digging, we realized that to answer many of our questions we have to run the full gamut of research – everything from high-level science, such as the fundamental nutritional biochemistry of CHO cells, to more routine work, such as looking at the variability in the manufacturing process for salt, for example.

A dynamic approach

Cell culture media has blossomed from the seemingly simple to the almost infinitely complex. And getting it right – at least for us – demands a multifaceted approach – or, in other words, the involvement of several areas: scientific research and development, quality, supply chain management, operations, and more. If we find something in R&D that may have some sort of impact – copper, for example – we need to set in motion a chain of events that spreads throughout the entire organization. It’s not all about cool science – it has to be translated into both the quality and manufacturing organizations to become fully realized.

Our focus on R&D has also allowed us to optimize our own raw materials and additives for use in upstream processes, which gives us a unique advantage; for example, our EMPROVE^® product portfolio offers a high level of quality that, in turn, can feed back into our cell culture media business. The result? Improved resource efficiency for both us and our clients. Notably, products bearing the EMPROVE^® trademark also come with comprehensive regulatory documentation, which can contribute to quality when clients file registration dossiers.

Right now, we’re working in an ever-evolving field, where new scientific knowledge about raw materials and their impact can be dynamically applied to improved products or better process understanding (both of which help our customers reach their own goals, whether that be improved quality or increased yields to drive down costs) – and that’s very exciting.