Abstract The high prices of biopharmaceutics or biologics used in the treatment of many diseases limit the access of patients to these novel therapies. One example is the monoclonal antibody trastuzumab, successfully used for breast cancer treatment. An economic alternative is the generation of biosimilars to these expensive biopharmaceutics. Since antibody therapies may require large doses over a long period of time, robust platforms and strategies for cell line development are essential for the generation of recombinant cell lines in a short period of time with higher levels of expression. Here, we obtain trastuzumab-expressing CHO-K1 cells through a screening and selection strategy that combined the use of host cells pre-adapted to protein free media and suspension culture and lentiviral vectors. The results shown that early screening strategy allowed to obtain recombinant CHO cell populations with higher enrichment of IgG-expressing cells. Moreover, the measurement of intracellular HC polypeptides by flow cytometry was a useful tool to characterize the homogeneity of cell population and our results suggest that might be used to predict the expression levels of monoclonal antibodies in early stages of cell line development process. Furthermore, using T-flask approach the assessment of the expression levels was studied in a setting more similar to that of a final production process. Finally, trastuzumab-expressing CHO-K1 clones were generated, characterized by batch experiments and preliminary results related to HER2-recognition capacity were successful. Further improvements in up-stream and down-stream steps related to this strategy will improve specific productivities and volumetric productivities of these clones.

The high prices of biopharmaceuticals or biologics used in the treatment of many diseases limit the access of patients to these novel therapies. One example is the monoclonal antibody trastuzumab, successfully used for breast cancer treatment. An economic alternative is the generation of biosimilars to these expensive biopharmaceuticals. Since antibody therapies may require large doses over a long period of time, robust platforms and strategies for cell line development are essential for the generation of recombinant cell lines with higher levels of expression. Here, we obtained trastuzumab-expressing CHO-K1 cells through a screening and selection strategy that combined the use of host cells pre-adapted to protein-free media and suspension culture and lentiviral vectors. The results demonstrated that the early screening strategy obtained recombinant CHO-K1 cell populations with higher enrichment of IgG-expressing cells. Moreover, the measurement of intracellular heavy chain polypeptide by flow cytometry was a useful metric to characterize the homogeneity of cell population, and our results suggest this could be used to predict the expression levels of monoclonal antibodies in early stages of cell line development. Additionally, we propose an approach using 25cm2 T-flasks in suspension and shaking culture conditions as a screening tool to identify high producing cell lines. Finally, trastuzumab-expressing CHO-K1 clones were generated and characterized by batch culture, and preliminary results related to HER2-recognition capacity were successful. Further optimization of elements such as gene optimization, vector selection, type of amplification/selection system, cell culture media composition, in combination with this strategy will allow obtaining high producing clones.