Development and Optimization of CHOgro® Transient Expression Technologies for High Titer Antibody Production in Suspension CHO Cells

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Mirus-upstream-2015-smDuring early stage drug development, quickly obtaining relevant candidate proteins through transient transfection can accelerate drug dis-covery. High titers are often obtained from Human Embryonic Kidney (HEK) 293 derived cell types; however, the use of different host cells between early stage transient and later stable protein production is a concern and can lead to the advancement of false-positive candidates. Chinese hamster ovary (CHO) cells are a desirable target cell type due to growth characteristics and a history of regulatory approval; however, their use has been hampered by low transient gene expression levels. To address this short-coming, we have created a robust and simple CHO transient protein expression system enabled by critical media attributes such as high density cell growth, quick adaptation and minimization of cell clumping post-transfection. The CHOgro® Expression System was developed through systematic optimization of transfection protocol parameters including: cell density, transfection reagent, media formulation and culture temperature leading to a commercially accessible high titer CHO transient transfection platform. Through this optimization antibody titers increased 2-10 fold over existing technologies with higher amounts of antibody secreted per cell. Six different representative antibody constructs were tested using the CHOgro® Expression System. Notably, even CHO cells maintained in other commercially available media formulations (e.g. FreeStyle™ CHO Expression Medium) can be seamlessly adapted with a full media exchange to the CHOgro® Expression Medium 24 hours prior to transfection and yield multifoldincreases in transient expression levels. With the CHOgro® Expression System high protein titers can now be achieved in suspension CHO cells through high density transient transfection.