Analytics And Cross-Functional Communication: Keys To Purifying Complex Molecules
By Tyler Menichiello, contributing editor
In case you missed it, this month’s Bioprocess Online Live was all about the challenges and special considerations for purifying multispecifics — molecules engineered to engage two or more distinct targets (e.g., bispecific or trispecific antibodies). I was joined by two expert panelists: Mark Fitchmun, president and CEO of Somatek, and Jian Ren, Ph.D., a principal scientist in AbbVie’s manufacturing science and technology (MSAT) bioresearch center. You can watch the full event recording here thanks to our event sponsor, Thermo Fisher Scientific.
During the hour, we discussed everything from common product- and process-related impurities to general best practices for developing a purification strategy. Of note, the conversation invariably circled back to one topic — analytics. This is understandable, given that process engineers can only truly understand a molecule and its properties with sound analytical methods. Ren made a comment that stuck with me that sums up the importance of analytical methods in one sentence. “Analytics is the eyes of process development,” she said.
“Without analytics, we’re basically operating blind.”
The Importance Of Good Measurements
“I don’t think I’ve ever worked on a project where better, faster, more accurate analytics wouldn’t have made things go faster, easier, and cheaper,” Fitchmun said. “You can’t overestimate the importance of good measurements.” Having comprehensive analytical methods in place early in development helps teams not only understand the molecule, but how process changes affect it.
As such, it is critical to establish analytical methods early — but not at the expense of an asset moving through the clinic, said Ren. “The goal is speed to clinic,” she said, “so we’ll probably accept something that is good enough.” She emphasized the importance of phase-appropriate analytical development. Essentially, methods should be sufficient to guide process development, but they don’t need to be at a BLA level during Phase 1. Method optimization and refinement should increase throughout the product life cycle, according to Ren.
In the same way that processes and impurities differ by product, so do analytical methods. “There’s probably not any existing platform method that you can just grab and use,” Ren said. Methods need to be developed and optimized for a molecule based on its properties. Luckily, with the help of AI, teams can start predicting the behavior of these molecules to inform and hopefully speed up analytical development.
Ensure Communication Between Upstream And Downstream
Another major aspect of purification and process engineering our panelists discussed during the event was the delicate interplay between upstream and downstream development teams — “a difficult dance,” Fitchmun called it. In a perfect world, upstream development teams would perfect their half of the process as downstream teams perfect theirs, resulting in abundant yields of a perfectly formulated product.
Of course, process development is far from perfect. Process changes upstream often have an effect downstream. “When everybody gets going, the downstream people want the upstream people to stop adjusting things, and the formulation people want the downstream people to stop adjusting things, but in reality, everybody has to keep working,” Fitchmun says. “It’s an interesting dance to coordinate.”
The irony of this dance is that formulation teams require partially purified product before they can generate meaningful data — e.g., buffer compatibility or stability profiles — to inform upstream and downstream process development.
So how can teams avoid dancing with two left feet?
At AbbVie, a dedicated CMC lead helps coordinate activity between upstream, downstream, and formulation development, Ren told us. This person has the advantage of overseeing the whole process, which allows them to keep teams on the same page (more or less). Another strategy that may help is imposing a temporary lock on development for teams to get their bearings, Fitchmun adds.
While the upstream team is doing their development work, they can create a temporary lock where they’re supplying downstream developers with something that’s not moving, he explained. Downstream engineers can do the same thing for the formulation team — provide them with a fixed product or stable intermediate while they make their improvements. “Then, everybody agrees that improvements get rolled out at an agreed upon time, and everybody sees how it changed their workflow,” Fitchmun said.
Taking A Holistic Approach To Multispecifics Purification
There’s hardly one right way to optimize your purification steps, as Fitchmun and Ren demonstrated with their differing opinions on the use of affinity resins. “I try not to rely on affinity chromatography, particularly for multispecifics,” Fitchmun said. “And the reason is that for most multispecifics, their product-related contaminants bind to the affinity resins just as good as the actual product.”
“Maybe not necessarily Protein A or Protein G,” Ren concedes, “but I think there are some newer resins that can work really well with bispecific or multispecific molecules. Especially in conjunction with upstream development efforts.”
By making intentional changes upstream, developers can strategically bias which impurities form and capture them with appropriate resins, thus reducing the burden on downstream polishing. An example Ren describes is optimizing a bispecific molecule’s expression ratio in cell line development so that one arm is over-expressed. This leads to the formation of specific and predictable homodimers, which can be selectively captured during affinity chromatography. “It’s a more holistic approach,” Ren explained. “From cell line development all the way down to purification.”
If you’re interested in more takeaways from this event, as well as a myriad of insights from past events, you can find them here. They’re all free and available to watch on-demand thanks to our generous sponsors. In a couple months, I’ll be putting together an event on single-use systems you won’t want to miss, so stay tuned to Bioprocess Online for more details!