Fed-batch culture currently represents the most attractive choice for large scale production for monoclonal antibodies (MAbs), due to its operational simplicity, reliability, and flexibility for implementation in multipurpose facilities. Development of highly productive cell lines, maximization of cell culture longevity, and maintenance of high specific antibody secretion rates through genetic engineering techniques, nutrition supplementation, waste product minimization, and control of environmental conditions are important for the design of high-yield fed-batch processes. Initially simple supplementation protocols have evolved into sophisticated serum-free multi-nutrient feeds that result in MAb titers on the order of 1-2 g/L. Limited research has been published to date on the effect of various culture parameters on potentially important quality issues, such as MAb glycosylation and stability. Although most fed-batch protocols to date have relied on relatively simple control schemes, increasingly sophisticated algorithms must be applied in order to take full advantage of the potentially additive effects of manipulating nutrient and environmental parameters to maximize fed-batch process productivity.

A fed-batch process using concentrated medium was evaluated for its ability to improve cell culture longevity and final monoclonal antibody (MAb) titers for two monoclonal antibody producing cell lines. It was found to result in up to 7-fold increases in final antibody titers compared to batch culture controls. Although the development cell line specific fed-batch protocols is critical to the development of cost-efficient large-scale production processes, the use of complete medium concentrates provided us with a quick and simple method for producing large quantities of antibodies in the early stages of process development, thus accelerating early work on purification process development, analytical development, biochemical characterization, and safety studies. Insights gained from the concentrated medium fed-batch approach were valuable for the development of refined, cell line specific feeding strategies yielding final MAb titers on the order of 1-2 g/L. Process development data on the effects of inhibitory growth byproducts, medium osmolarity, and the mode of nutrient feed addition on culture longevity and MAb production and information on culture metabolic behavior were successfully incorporated in the development of the optimized fed-batch protocols.

An initial structured unsegregated kinetic model describing monoclonal antibody synthesis by a murine hybridoma cell line (9.2.27) grown in 1 liter batch cultures is described. The model is based on the intracellular balances of the heavy and light chain coding mRNAs, the intracellular balances of heavy and light chains and the description of the kinetics of heavy and light chain assembly. Model parameters were varied with specific growth rate in order to account for changes in the rates of antibody synthesis and secretion with entrance of the cells from the exponential into the stationary phase of growth. The parameters were varied based. on experimental data obtained in our laboratory on the variation of total cellular RNA content and the half-lives of heavy (H) and light (L) chain mRNAs with specific growth rate, and data from other investigators on immunoglobulin synthesis and secretion. The model successfully predicts the experimentally observed decrease in the intracellular heavy and light chain mRNA levels with entrance of 9.2.27 cells from the exponential into the stationary phase of growth, as well as the extracellular accumulation of antibody (IgG(2a)) during batch culture.

A three compartment model (ER --> Golgi --> extracellular medium) is used here to describe the interorganelle transport and final secretion of an IgG(2a) monoclonal antibody (MAb) in 9.2.27 murine hybridoma cells. Model simulations of pulse-chase and continuous labeling experiments are used to gain a better understanding of the kinetics of MAb interorganelle traffic. Simulation results for the continuous labeling case compare well with experimental data obtained during continuous labeling of 9.2.27 hybridoma cells. Incorporation of this compartmental transport model into our previously developed model of MAb synthesis and assembly can provide a useful tool for analyzing the dynamics and regulation of the complete antibody secretory pathway under different growth and/or nutritional conditions.