(68d) A Novel Kinetic Model-Based Metabolic Flux Analysis for Antibody Producing Cell Lines

Monoclonal antibodies (MAbs) are significant reagents used extensively in diagnostic assays, therapeutic applications, and in vivo imaging. Mammalian cell cultures have become the favored production hosts for MAbs, since microbial systems are not able to carry out the complex post-translational and functional modifications of these proteins, such as glycosylation. Chinese Hamster Ovary (CHO) cells and hybridoma cells, which share similar metabolic characteristics, have been popular cell types for production of MAbs. The efficient performance of these cell cultures requires highly specialized culture media to enhance MAb yield for in vitro production in view of substantial cell death and reduced MAb productivity due to the variations in culture conditions. Although production practices have been employed for decades, cell kinetics is still under investigation to obtain quantitatively as well as qualitatively cost-effective production strategies. Creating these strategies requires understanding of cell metabolism affected by process dynamics in culture environments. Kinetic models empower us to illustrate quantitative cell growth and metabolic activity, which allows prediction of different cell phenotypes and provides better understanding of cell physiology, which is important in optimization of MAb production in animal cell cultures.

This work presents a new kinetic model of mammalian cell metabolism characterized by a reduced metabolic network developed on the basis of a set of macro-reactions provided by Niu et al. (2013). The model can predict time-dependent concentrations of metabolites, cell growth and productivity over a broad range of culture conditions. The metabolic network is described by 17 macro-reactions, with pyruvate, aspartate and glutamate serving as node metabolites in the network. Glutamine is considered as a regulatory metabolite for GS-CHO cells and determines asparagine utilization route and energetic state of animal cells. The model incorporates energy metabolism in biomass and monoclonal antibody formation. The specific ATP production rate is computed considering the central carbon metabolism and is used for estimation of biomass and MAb synthesis rates. All enzyme catalyzed reactions in the network are described by Michaelis–Menten type rate expressions with concentration dependencies of their precursors and currency metabolites. ATP production by glycolysis and respiratory chain is incorporated. The kinetic model was calibrated for glutamine free and glutamine available cases and validated for fed-batch cultures involving glutamine as the carbon source in the feed. Un-optimized fed-batch culture simulations are discussed for pulsed fed-batch operations and constant feed rate operations. Fed-batch operation with glutamine-free feed media increases the culture longevity and product (MAb) yield. The model predictions are in good agreement with the experimental data reported in the literature.