Expressed therapeutic protein yields are predicted by transiently transfected mammalian cell population

Therapeutic proteins are currently at the hotspot of innovation in the pharmaceutical medicine. However, their industrial production is technically challenging and improved methods for transcriptional manipulation of mammalian industrial cell cultures are needed. In this work we show that some of the most frequently used lab scale transfection efficacy assays fail to predict performance in the protein production settings. We compare the efficacies of a number of transfection reagents using adherent and suspension mammalian cell cultures and assessment based on several assays that utilize reporter protein quantitation, transfected cell population and post-transfection viability of cells. We validate reporter assays for assessing transfection methods in the lab that predict protein production in industrial settings. We also demonstrate that cell penetrating peptide-based transfection achieve significantly higher protein yields compared to PEI and lipoplex methods in both CHO and HEK293 producer cell lines. Availability of fast lab scale screening methods allows future development of improved transfection methods for protein production. One such potentially effective transient transfection method is the CPP-based approach presented currently. ### Competing Interest Statement The authors M.U. and U.T, are employed by the company that owns the protein production technology QMCF - a technology that has also been used in the current manuscript. However, M.U. and U.T. participated in the current work as independent authors and the contents of the manuscript are not affected by financial ties