Expert Insight: Cell line development: Accelerating process optimization by combining cell culture with titer measurements

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Dr. Dirk Müller, Manager of Media & Process Development, Sartorius, and Lukas Klein, Scientist, Bioprocess Development, Sartorius

Cell line development involves screening thousands of clones to find those that are stable, produce high yields of the bioproduct, and exhibit the desired critical quality attributes (CQAs). While there are multiple CQAs that need to be monitored early in the development process, product yield, cell count, and viability assessment remain the main attributes by which process conditions are optimized.

In this SelectScience^® webinar, now available on demand, experts from Sartorius, Dr. Dirk Müller, manager of media & process development, and Lukas Klein, bioprocess development scientist, explore the analytical techniques and technologies such as the Octet^® system that can be incorporated into cell line selection workflows and greatly accelerate studies.

Read on for highlights from the Q&A discussion or register now to watch the webinar on demand

Can I use the Octet^® technology for assay types other than IgG titer determination?

DM: Yes, you can. The Octet^® system offers a range of different assays that you can use. For example, you can use it for measuring the sialic acid or mannose content of your products, and also for whole-cell protein.

What possible interferences from the cell broth do I have to be aware of when measuring titer using the Octet^®?

DM: In our experience, there's limited cross-reactivity because you tend to work with diluted supernatant samples. In that case, you can also conduct explicit standard edition studies with a little standard concentration to check for any potential interference in your matrix background.

Do you expect the findings regarding the impact of process parameters on specific productivity to be generalizable?

LK: The results that we have shown in this webinar apply to the particular clone that we have tested, and they can be different from clone to clone or if you have different clone and media combinations. However, they clearly serve as an example to illustrate the general strategy of acquiring and evaluating such data sets. But yes, of course, you can expect to see qualitatively similar results also for other cell lines or product clones that you may test.

What exactly is meant by specific productivity?

DM: Specific productivity can mean two different things. Firstly, specific productivity can mean the instantaneous cell-specific productivity during the process or the product formation rate, for example, if you look from day to day - how is my specific productivity evolving during the process?

The second way of looking at specific productivity is looking at the overall process. This is if you have an average value, a process integral value across the whole process. When you select certain clones or conditions, you use the final titer and can use the integral of viable cell counts to calculate that value and compare between the different clones, for example.

From your experience, what is the predictory value from Ambr^® 15 when processing data from 3 liters, 10 liters, or larger volumes?

LK: In our view, the Ambr^® 15 is predominantly a system where you can test certain conditions. You can do clone rankings, you can rank the best media, and you can also make first assessments on sensitive parameters in your process.

However, if you really want to optimize your process and ensure you have scalability, we recommend using something like an Ambr^® 250 system that has a larger working volume, so around 200 mL or 250 mL instead of just 15 mL. Because the reactor geometry, etc., is also more akin to what you have at the larger volume ranges, it is typically easier to transfer the setup of your process.

How is cell viability measured, and how frequently is it measured by the Ambr^® system?

DM: In principle, that is something you can program. There's a routine for how often you can program that. We typically do it once daily, and for most processes, this is sufficient. Then while you take a cell count you can hook it up, for example, to a novaFLEX device or to a Vi-CELL device, and then you perform both the cell count and the cell viability measurement.

That is usually sufficient on our end, but it clearly depends on the application you have. For example, if you want to investigate the decline in viability towards the end of the process in more detail, you can also program to take samples twice a day to better track where you have this phenomenon occurring.

Are there any general considerations people should be aware of in terms of contamination when using these systems?

LK: We have good experience in that we have very few contaminations. Typically, if you have clean handling with the vessels, make sure you inoculate properly, keep the vessels open only for the sample durations, and also optimize the program for the Ambr^® to minimize open handling times, then I think you will have a very low rate of failure.

Also, depending on applications and how many cultivations you run, you can, of course, try to back up by running duplicate runs. In case one would fail, you could still reserve or rescue some of your results if you see that as an issue, but in our hands, it works quite well to just use, for example, 48 reactors for 48 different cultures.

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