Drugs produced by biotechnology are spreading quickly across the globe, raising hope for safer, more effective cancer treatments. Crucial for large-scale production of these complex drugs is gentle but effective separation technology.DATE 2019-12-23 AUTHOR Martin Neander
When Alexander Fleming discovered penicillin in 1928 it was a major medical breakthrough. His observation that colonies of the bacterium Staphylococcus aureus could be destroyed by the mould Penicillium notatum led to the development of medicines that could kill certain types of diseasecausing bacteria inside the body, effectively treating many previously serious diseases such as syphilis and Staphylococcus infections.
Although many types of bacteria have since become resistant, penicillin is still widely used today, and pharmaceutical drugs continue to play a major role in health care worldwide. However, life expectancy is rising around the globe, and people are running greater risks today than they did even 20 years ago of being affected by various other serious ailments. The need for treatment for different types of cancer, for example, calls for highly advanced drugs and new production methods.
The latest production technique for complex protein-based drugs is cell culturebased drug production. From the initial research carried out in the United States in the 1980s it has spread across the globe to Europe and lately to Asia. In fact, growing and harvesting mammalian cells to produce new medicines has turned into one of the most thrilling sections of the life science industry.
Proof that microbial and pharmaceutical drug production is in a negative trend and that cell culture-based drug production is on the rise comes from the US Food and Drug Administration statistics. Of 100 new drugs per year that are filed as new drug applications (NDAs), about 60 rely on cell culture-based production, while only 15 are produced by microbial fermentation (the remaining 25 are produced by traditional chemical processes). Out of the 100 NDAs, about half address cancer diseases.
From a drug production perspective, there are huge benefits to be found in the cell culture process. Compared with productionusing microorganisms, the mammalian cell can produce complex proteins that target diseases better and in a more direct and structured way, which is of great importance for cancer drugs based on monoclonal antibodies. These bind only to cancer cell-specific antigens and induce an immunological response against the target cancer cell.
The cell culture-based production process basically involves three steps: fermentation, harvesting and purification. Fermentation involves the growth of the mammalian cellbroth. In the cell-harvesting phase, cells are separated from the fermentation broth. The liquid or “centrate” from the harvesting stage is then purified, and the desired protein is separated and collected. Research in the mammalian cells field to create advanced medicines began in the 1980s.
From the start, Alfa Laval worked with industry leaders in the development of large-scale cell culture fermentation. During this journey, it became obvious that cell culture characteristics called for an extremely gentle separator design. Centrifuges have a powerful ability to separate in a continuous mode and can reach very high G-forces in rotation, which benefits the cell-harvesting process. However, because mammalian cells are fragile and easily break apart, the design of the harvesting centrifuge is crucial. If shearing forces are generated at the inlet, cells are torn apart. Separation becomes highly difficult, and the flow rate has to be kept lower.
“Thanks to the gentle design of our Culturefuge separators, the fragile cells are not torn apart, and full separation is achieved even at high flow rates,” says Tom Manelius, manager, Process Analysis & Design at Alfa Laval. The single most important location inside the centrifuge is the acceleration zone, where the fermentation broth is accelerated within fractions of a second. “Our way of designing the acceleration zone has been crucial to the superior performance in the harvesting of mammalian cells,” Manelius says.
The level of lactate dehydrogenase (LDH) is one way to measure the shear in cell culture processes. LDH is an enzyme released from damaged cells; the greater the concentration, the larger the percentage of broken cells. Manelius says that the inlet design used in traditional microbial fermentation may generate an LDH increase in the range of 10–20 percent. “When using the extremely gentle liquid-filled inlet in our Culturefuges, the LDH elevation typically stays under 5 percent,” he says.
The hollow spindle design of Alfa Laval’s Culturefuge product range allows the gentlest acceleration possible in a centrifugal disc stack separator, according to Manelius. This reduces the destructive shearing forces that the cells are exposed to. “The use of a hollow spindle also eliminates an air-liquid interface, because the feed zone is completely filled with rotating liquid,” he says. “This is unique compared with other solutions on the market. The hermetic outlet ensures that there is no contact with the air or any external environment. In this way, foaming is avoided.”
Another source of undesirable shear forces is the feed pump. With the Alfa Laval Culturefuge design this is not an issue because it does not use a feed pump. Instead, the fermentation broth is fed to the harvesting centrifuge by applying overpressure to the fermentor.
Manelius says an interesting result was found in a research study when comparing two disc stack centrifuges – one with a classic nonfilled acceleration zone and the other with a hollow spindle hermetic inlet for gently accelerating the feed. The research group found a 2.5-fold increase in throughput for the same clarification performance when processing through a hollow spindletype centrifuge.
Avastin against cancer
Avastin, developed by US biotech company Genentech, is one of the newest cancertreatment drugs produced using cell culture technology. It is a protein that slows down the development of cancer by restraining the formation of blood vessels in tumours.
Avastin is made from mammalian cells. To provide additional production capacity for the production of Avastin, Roche Pharma Biotech Production Basel has built the MAB Building 95 in Basel, Switzerland. It has 6 x 12.5 cubic metres of fermentation capacity and two downstream processing lines for the recovery and processing steps that yield the final product.
Alfa Laval has delivered equipment to the building for the production of this innovative cancer drug.