Greater Impact Early On
Cell-culture optimization occurs throughout a product’s production life cycle, but options decrease over time. Processors have some leeway during late-stage development, even during clinical manufacturing, but the window of opportunity for enacting substantial changes begin to peter out during Phase II.
“That’s where things start to get locked down, but improvement continues throughout,” says Mindy Goldsborough, Ph.D., R&D director for advanced bioprocessing at BD Biosciences. “Companies are always interested in improving the efficiency and safety of their processes, and will even re-file if these benefits are sufficiently strong.”
BD’s cell-culture products include catalog media for growing CHO and other mAb-producing cells. The company has sold peptones (hydrolysates) for over 50 years and will soon launch chemically defined feeds/supplements.
“Chemically defined products take cell culture to the next logical step beyond animal component-free,” says Dr. Goldsborough. Adoption of animal-free ingredients was undertaken for safety reasons, chemically defined media for consistency.
BD also recently opened a media and supplement manufacturing facility in Miami, which is both animal-derived component-free and antibiotic-free, and controlled for animal-origin component raw materials to the tertiary level. It serves the cell-culture media needs of bioprocessors working with mammalian, microbial, or stem cell lines.
Process analytic technology (PAT), if widely implemented, could become the last link in the cell-culture process improvement chain, and one that operates in real time or nearly so.
Ultimately, processors would like to tweak processes as they proceed through PAT, but that is still a long way off for most biomanufacturers. Despite protestations from large manufacturers, regulators, and industry observers, PAT has been slow in its realization.
Friedrich Srienc, Ph.D., a professor at the University of Minnesota Biotechnology Institute, has developed a technique, based on flow cytometry, that is suitable for a PAT-based global assessment of cell-culture health.
Apoptosis and other cell cycle-indicating phenomena are useful in assessing the vitality and productivity of cultured cells, as well as their suitability for passaging. Investigators can assess culture density, protein-expression levels, and viability for both the culture and individual cells using appropriate off-the-shelf stains and standard flow-cytometry equipment.
Flow cytometry is traditionally thought of as an off-line analysis mode, which slows it down. Add to this the time and effort required to withdraw samples from the bioreactor and stain the cells. Making the process PAT-worthy would require speeding up or automating the individual operations.
Dr. Srienc has achieved that by automating the sampling, staining, and cytometry steps. Now, it is possible to quantify cell and culture parameters in a way that supports decision-making during the culture. “In my opinion you cannot get more detailed information on the properties of cells or a cell culture than with flow cytometry,” he says.
But despite the near-real-time capabilities of this technique, interest from industry has been mixed. “The stumbling block is that the system is not an off-the-shelf instrument that can be easily installed and deployed.” Potential biopharmaceutical customers all have engineers capable of putting such a system together, “but they have other priorities.”