In 2006 a new term was coined that is now all too familiar in the industry: downstream bottleneck. With observations of a slow cycle of downstream process improvements indicating potential solutions in the next five years, downstream processing is a very hot topic at conferences and in publications. Thus, the Recovery and Purification track will be highly focused on this pertinent and timely issue. Beyond discussing the bottleneck itself head-on in the opening sessions, the track will focus on alternatives to protein A purification and conventional chromatography, benefits of single-use technologies, optimization strategies, and enhanced downstream process development methods.
Joe Zhou, scientific director of process development at Amgen, will analyze single-use systems in downstream processing. He will look specifically at the use of single-use depth filtration, membrane chromatography, and nanometer filtration technology products for MAb processing. In an interview with BioProcess International, Zhou explained that in order implement single-use technology in the downstream processing steps, the cell culture processes must be optimized.
“The improvements for the cell culture part is removing whatever the impurity is — particulate, turbidity, or chalk level,” explained Zhou. “And also add a prewash step to the protein A, and remove turbidity, chopped DNA, or complex lipids. Then the output from protein A will be very clean already. That will not give you much challenge when you apply it to any disposable system of Q-membrane, or depth-filter, or the 20-nm filtration.”
Another new term is ABC, or “anything but chromatography.” This concept is central to efforts in the downstream processing sciences because the cost of chromatography columns greatly affect manufacturing costs as a whole. Zhou explained that with lowering stock prices at big biopharmaceutical companies, the downstream teams have to work harder while continuing to provide for product safety.
“Therefore, we talk about a two-column operation, which will actually do much better than ABC because they are easily scaled up and can already take care of the issues of safety, specifically viral clearance and in protein removal.”
David Wood, assistant professor of chemical engineering at Princeton University observed that some companies seem resistant to ABC because of unknown implications with the regulatory bodies.
“What interests us most in academia are very new processes that depart from established ones. For example, things like nonchromatographic separations are highly scalable, and potentially chromatographic separations have managed to radically advance the capacity,” said Wood. “But I think that in industry there is a lot of attachment to the past because they have processes that the FDA will approve and therefore it’s hard to embrace totally new technology.”
Zhou responded with the industry perspective, “At this moment, we need to see more data because we are data-driven companies. But I’m not saying that ABC is not an option. We’re looking for it to be popular in the future.” However, the main roadblock is viral clearance. Validation in a nonchromatographic system would have to meet FDA requirements, and the cost associated with that validation process is a major factor in the industry’s lack of forward movement.
Wood’s talk will focus on self-cleaving fusion tags for the nonchromatographic capture and purification of recombinant proteins. He is very aware of the industry’s uncertainty and questions about the technology as well as steps that need to be taken to address those concerns.
“A self-cleaving tag has the potential to free up a lot of different types of purification in terms of affinity. However, there are still a lot of questions,” shared Wood. “A lot of the biotech companies raise those questions like, Can you guarantee complete cleavage? Can you guarantee that the cleaved tag won’t leak into the product? Can you guarantee that you won’t leak into the product? Can you guarantee that you won’t get a broken cleavage? And some of those things still need to be worked out. Of course the big question that we’re working on in my laboratory is: can you get this to work with antibodies being expressed in CHO?”
Matthias Berkemeyer, head of downstream process development at Boehringer-Ingelheim will be presenting on protein crystallization. Wood shared some of the questions that he’s heard about this technology’s overall potential in the industry.
“I’ve seen some things with crystallization that are pretty impressive, but they don’t seem very generalizable,” shared Wood. “I know that a lot of the companies want to move toward a platform manufacturing method, and I don’t know if crystallization is going to be easy because forming crystals has to be carefully optimized for each protein.” A lot of questions are floating around the industry, and the speakers will filter them down to provide some productive answers.