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The quest for a viable upstream process relies on generation of a cell line expressing the protein of interest. Unfortunately, the search for the best-producing clone is often compared with looking for a needle in a haystack. Making this more challenging is the pressure to get it right the first time, quickly and while mitigating risk and costs.
This case study explores our mini-pool approach as fast track process for small biotechs who are on a very challenging timeline. It enables us to start process development and production of early material before cell line development is completed.
Chinese hamster ovary (CHO) cells are widely used as the host cell line for production of therapeutic recombinant proteins. Cell line development (CLD) processes, however, are time consuming and labor intensive. The ability to more rapidly and efficiently select high-producing cell lines is needed to accelerate upstream processes, while saving time and money (see Figure 1).
Our mini-pool approach consists of dividing a transfected cell population into many tiny populations in 96-well plates. This facilitates detection of high-producing cells as a result of the reduced diversity and reduced competition occurring within these mini-pools. With a large number of mini-pools available for screening, we also increase the probability of isolating a high producer.
The process begins by plating transfected cells in 96-well plates. In order to more efficiently screen and expand the mini-pools in static cultures and reduce labor requirements, we developed a semi-automated technology platform to monitor growth and productivity. The platform includes a cell imager with associated robotics and an automated incubator. Imager software records cell confluence in each well, facilitating the documentation and monitoring of cell growth. After recovery, all mini-pools are directly screened in 96-well plates to measure their productivity performances using a high-throughput analyzer.
This semi-automated platform allows the simultaneous screening of 3150 mini-pools. Combining the technical capabilities of the platform with statistical analysis of the high volume of data generated, enabled a reduction in the number of mini-pools screened while delivering the same performance results. This approach demonstrates the value of automated systems to efficiently create, screen and isolate high producing clones with reduced costs. Additionally, the mini-pool approach allows us to confidently use material from the mini-pools to start process development which can reduce the workflow by approximately 10-13 weeks (see Figure 1).
A number of strategies exist to accelerate the timeline from DNA to material and deliver the required titer. Employing the right combination of approaches to create an optimized process requires expertise and experience across all aspects of cell line development.