Considerable progress has been made increasing productivity of cell cultures to meet the rapidly growing demand for antibody biopharmaceuticals through increased cell densities and longer culture times. This in turn has dramatically increased the burden of process and product related impurities on the purification processes. In addition, current trends in the biopharmaceutical industry point toward both increased productivity and targeting smaller patient populations for new indications. Taken together, these developments are driving the industry to explore alternative separation technologies as a future manufacturing strategy. Clarification technologies well established in other industries, such as flocculation and precipitation are increasingly considered as a viable solution to address this bottleneck in antibody processes. However, several technical issues need to be fully addressed including suitability as a platform application, robustness, process cost, toxicity, and clearance. This review will focus on recent efforts to incorporate new generation clarification technologies for mammalian cell cultures producing monoclonal antibodies as well as challenges to their implementation supported by a case study.
There is extensive experimental data showing that the final pH and buffer composition after protein diafiltration (DF), particularly with monoclonal antibodies, can be considerably different than that in the DF buffer due to electrostatic interactions between the charged protein and the charged ions. Previous models for this behavior have focused on the final (equilibrium) partitioning and are unable to explain the complex pH and concentration profiles during the DF process. The objective of this study is to develop a new model for antibody DF based on solution of the transient mass balance equations, with the permeate concentrations of the charged species evaluated assuming Donnan equilibrium across the semipermeable membrane in combination with electroneutrality constraints. Model predictions are in excellent agreement with experimental data obtained during DF of both acidic and basic monoclonal antibodies, with the protein charge determined from independent electrophoretic mobility measurements. The model is able to predict the entire pH/histidine concentration profiles during DF, providing a framework for the development of DF processes that yield the desired antibody formulation.
These results provide important insights into the effects of both histidine and sucrose on the behavior of concentrated mAb solutions, including the potential impact on ultrafiltration / diafiltration processes.
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