UCOE technology enabled the selection of high expressing clones capable of producing 1.5–2 g/L of protein within ten weeks. This compares favorably to traditional methods that can take up to 10–12 months. Figure 4 shows that productivities can be increased from around 0.4 g/L to 1.5–1.9 g/L with minimal optimization in protein-free media with supplemental feeds.
The technology therefore enables not only the isolation of high expressing clones but can also allow the selection of high expressing pools, produced by transfecting the culture with the UCOE expression plasmid, followed by antibiotic selection. Such pools can be isolated within 2–3 weeks of transfection with a minimal quantity of plasmid DNA.
These pools can be used to generate research cell banks without the need for repeat transfection, and demonstrate high levels of productivity up to orders of magnitude above that achievable with transient transfection. This has allowed Cobra to supply large quantities of material for early-stage downstream purification (DSP) development for a number of clients.
In one example a human IgG1 was expressed in an initial shake flask media screen to 645 mg/L; this was followed by a 5 L fermentation, which allowed the development of a purification scheme prior to the isolation and generation of material from clones.
An IgG1 fusion has also been expressed at 500 mg/L in shake flask cultures using a generic medium developed for our CHO-S cell line; this has again allowed the development of an early-stage DSP process with the supply of sufficient quantities of material for activity studies. The production of material in pools is now routinely used at Cobra to reduce project timelines significantly.
UCOE technology is of huge value to the bioprocess industry if combined with informed cell-line development.
The engineering of expression vectors containing UCOEs enables the rapid and easy production of stable, high-expressing cell lines that are suitable for large-scale production and the rapid isolation of high expressing pools. Protein yields of 2 g/L can now be obtained with a reduced drain on resource, providing a cost-effective production solution to the biopharmaceutical sector.