Protein engineering techniques can be used to produce more potent animal-free growth factors as highlighted by the higher level of Nanog expression in iPSCs cultured with an optimized form of the key growth factor TGF-1 (RHS), when compared with cells cultured with the mammalian-cell expressed protein (LHS). Credit: Stemnovate
Most industries today are under pressure to switch to more ethical and sustainable animal-free alternatives, and now the trend is coming to stem cell labs. As stem cell applications accelerate towards the clinic, novel drug discovery platforms are rapidly scaled, and new transformative stem cell-based technologies such as cultured meat arise, there is a drive to switch to animal-free cell culture media. This move is essential to facilitate future regulatory approval for advanced therapies, and enable pharma and biotech companies to ethically, reproducibly and cost-effectively scale stem cell-based innovations. Most stem cell scientists today use recombinant growth factor and cytokine proteins in their chemically-defined media to supply their cultures with the necessary biological signals required for maintenance of pluripotency, cell proliferation and differentiation into specific cell lineages. However, the fundamental biochemistry and manufacturing processes of these protein messengers can often be overlooked. But as scientists are trying to establish new animal-free systems to support the scale-up of their stem cell applications, the properties and challenges inherent in these proteins are becoming more prominent and frankly a headache for many.
Highlighted here are three key challenges facing pharma and biotech companies as they embark on the path to implementing animal-free systems, from the perspective of two protein scientists. 1.Why batch consistency is kingAs stem cell therapies gear up to make the leap from bench to clinic and the promise of stem cell biology in drug discovery and other industrial applications is realized, more subtle and still largely inexplicable challenges in optimizing growth factor and cytokine supply chains for defined media are being identified why when you change from one supplier or even batch of a recombinant protein do stem cells need weaning onto that protein, or dont tolerate the change? Is this a fundamental lack of batch consistency across the supply chain or is there an underlying biological basis?
At the minute, there is simply not enough data to answer this definitively. While we are starting to tease apart these questions, it highlights the need for greater innovation within the recombinant protein supply chain to bring best practice and innovation from other areas to improve the robustness of the global supply chain and encourage great openness and scrutiny of fundamental biochemical quality early in process development.
Questions we should ask include: are we seeing heterogeneity in post-translational modifications, which is well documented in monoclonal antibody manufacturing? Can synthetic biology or protein engineering be used to optimize proteins and engineer out features contributing to this variation?
For now, and until we have answers, its a good idea to source proteins from reputable suppliers that have rigorous standards for batch quality testing and meticulously scrutinize all biochemical and bioactivity data provided. 2.Cost of goods as a barrier to scaleTo bring innovative stem cell applications to market, pharma and biotech companies need to be able to seamlessly scale their cultures, meet regulatory requirements and achieve a sensible and sustainable process cost. Where recombinant proteins are needed in cell culture media, they are usually the greatest contributor to cost of goods.
Well-defined industry challenges catalyze change and the stem cell field is seeing renewed focus on much needed innovation in complex bioactive protein production to meet the needs for animal-free, highly reproducible proteins. Protein engineering technology, enhanced cell-based and cell-free expression systems, such as bacteria, yeast and even plants, coupled with improvements to downstream processing systems are just some of the latest innovations in this space. Previously, there have been concerns over the ability of simpler systems to form correctly folded and bioactive recombinant proteins. However, it is clear that many of these barriers can be overcome to produce highly pure growth factors and cytokines at scale. Others are striping back chemically-defined media protocols to determine the essential growth factors and cytokines needed for their cell type. For example, homebrews of key growth factors to reduce costs – Paul Burridge and his team at Northwestern University Feinberg School of Medicine have pioneered a cost-effective B8 chemically-defined media for weekend-free hiPSC culture at just 3% of the price of commercially available media. Now the challenge is to take the learnings from academic studies such as these and translate them into industrial processes. Meating the price of lab-grown steaksYou cannot discuss the cost of growth factors without mentioning the daunting step-change and barrier facing the fast-evolving cultured meat market. Here, highly optimized animal-free growth factor production systems will be required to provide the economies of scale needed to deliver kilogram-ton quantities at a fraction of the price in order to bring these lab-grown meat alternatives to consumers. After all, it just isnt viable for companies to be spending hundreds of dollars on each liter of culture media – instead, this needs to be reduced to ~$1/liter. 3.Animal-free or ADCF? Now that is the questionDespite animal-free/animal-derived component free (ADCF) growth factors and cytokines becoming increasing important, there are no standard definitions for these terms across the industry, with many protein manufacturers supporting the sector by defining their own internal standards. For the clinical space, the United States Pharmacopeia and International Organization for Standardization have published a framework for classifying raw materials used in cell therapy manufactureinto four different tiers based on their risk. Under this classification, ancillary materials used in the manufacture of cell-based therapies and tissue-engineered products, such as recombinant growth factors and cytokines, are considered low risk so fall into tiers 1 and 2 with an ADCF level of manufacturing defined as all components, sub-components and consumables do not contain materials derived from animals. To support the wider sector, not just those at the transition to the clinic, clarity over definitions and transparency from manufacturers will help to define and overcome the challenges faced and allow the promise of stem-cell derived innovations to be delivered.
Beata Blaszczyk, Senior Scientist, Qkine
Dr Catherine Elton, CEO and Founder, Qkine