Medium and Feed Development: Beyond Maximizing Protein Titer to Optimizing Glycan Distribution and Simplifying Process Scale-Up

Serena Fries Smith, associate director of global technical engagements for Thermo Fisher Scientific, covered advantages in feed solutions in the context of current industry trends in an early November webinar. Leveraging feed designs and strategies can optimize glycosylation of complex proteins, simplify scale-up of fed-batch processes, and improve expression titers.

Smith’s Presentation
In 1994, the average expression titer was 0.5 g/L. Thanks in part to improvements in culture feeding, titers had increased to 1.3 g/L in 2004. By 2014, they reached 2.5 g/L. Now some processes are reporting up to 7.0 g/L. And Thermo Fisher has begun to tackle other industry challenges: e.g., developing feed formulations that help modulate glycosylation (GlycanTune total feeds) and dry media for simplified handling and improved process scale-up.

Glycosylation is an important protein quality attribute. It is critically important when a glycan distribution profile must be matched (e.g., when developing biosimilars or transitioning to new clones for existing processes) or when a specific glycan pattern is part of optimizing efficacy. No single glycan pattern is best for all products. Smith showed how simply adjusting certain feed components (and the time they are introduced to a culture) could change the pattern in a given cell line. That allows users to target these patterns to meet the needs of their specific products.

Gibco AGT dry media format is intended to simplify working with dry-powder media formats and reduce the risk of formulation errors. Superconcentrated formulas improve efficiency as well by helping companies make better use of available bioreactor working volumes. Whereas some fedbatch processes might add 30% or more of a nutrient feed at a time, a 3× concentrated feed decreases the volume to <10% while delivering the same amount of nutrients to cells. Thus the initial bioreactor working volume can be increased, and the volume change is minimized.

Schematics showed how the AGT format reduces errors by reducing ≤16 feeding steps down to only six, with no need for pH or osmolality adjustments. So it also reduces the need to manage additional raw materials for those adjustments. Gibco EfficientFeed+ products are stable at room temperature for 30 days after reconstitution, lessening the need for cold storage. Smith also showed two applications of superconcentrated EfficientFeed+ products that increased titer.

Questions and Answers
How can this help with glycosylation in an established process? If you’re using a specific medium and feed already, you can switch it out for our GlycanTune feed and test the results. It comes in three different formulations: GlycanTune A+, B+, and C+ total feeds. So I recommend looking at all three to identify which one works the best for your system and complements the feed that you are currently using. You will see the same type of change in your glycosylation pattern.

Is the hydrated 3× efficient feed really stable for a month at room temperature? At any concentration up to their maximum, EfficientFeed+ and GlycanTune+ products are stable at room temperature for up to 30 days.

Have these feed solutions ever been used with a perfusion bioreactor? We have a number of customers using them in perfusion — typically not as a sole perfusion medium, but rather in combination with one of our other products.

From which expression system have you generated these data points? And what kind of protein? These data points were generated using a Chinese hamster ovary (CHO) cell line producing a monoclonal antibody (MAb). Some customers also have evaluated GlycanTune products for nonantibody proteins, and they do see some changes in the glycosylation patterns. I would just recommend trying different experiments to help you hone in and determine the best approach.

Part of my job is to work with customers in designing initial screening experiments to evaluate how our products could work with their systems and meet their technical requirements. Reach out to me for support.

More Online
The full presentation (with supporting slides and data) can be found on the BioProcess International website at www.bioprocessintl.com/ask-the-experts/taking-medium-and-feed-development-beyond-maximizing-protein-titer-to-optimizing-glycan-distribution-and-simplifying-process-scale-up. Contact the presenter at [email protected].