Biomass specific perfusion rate as a control lever for the continuous manufacturing of biosimilar monoclonal antibodies from CHO cell cultures.

Continuous manufacturing enables high volumetric productivities of biologics such as monoclonal antibodies. However, it is challenging to maintain both high viable cell densities and productivities at the same time for long culture durations. One of the key controls in a perfusion process is the perfusion rate which determines the nutrient availability and potentially controls the cell metabolism. Cell Specific Perfusion Rate (CSPR) is a feed rate proportional to the viable cell density while Biomass Specific Perfusion Rate (BSPR) is a feed rate proportional to the biomass (cell volume multiply by cell density). In this study, perfusion cultures were run at three BSPRs in the production phase. Low BSPR favored a growth arresting state that led to gradual increase in cell volume, which in turn led to an increase in net perfusion rate proportional to the increase in cell volume. Consequently, at low BSPR, while the cell viability and cell density decreased, high specific productivity of 55 pg per cell per day was achieved. In contrast, the specific productivity was lower in bioreactors operating at a high BSPR. The ability to modulate the cell metabolism by using BSPR was confirmed when the specific productivity increased after lowering the BSPR in one of the bioreactors that was initially operating at a high BSPR. This study demonstrated that BSPR significantly influenced cell growth, metabolism, and productivity in cultures with variable cell volumes.

Raman spectroscopy provides valuable process insights for cell-derived and cellular products.

Two of the big challenges in modern bioprocesses are process economics and in-depth process understanding. Getting access to online process data helps to understand process dynamics and monitor critical process parameters (CPPs). This is an important part of the quality-by- design concept that was introduced to the pharmaceutical industry in the last decade. Raman spectroscopy has proven to be a versatile tool to allow noninvasive measurements and access to a broad spectrum of analytes. This information can then be used for enhanced process control strategies. This review article will focus on the latest applications of Raman spectroscopy in established protein production bioprocesses as well as show its potential for virus, cell therapy, and mRNA processes.

A protocol to transfer a fed-batch platform process into semi-perfusion mode: The benefit of automated small-scale bioreactors compared to shake flasks as scale-down model.

Continuous processes such as perfusion processes can offer advantages compared to fed-batch or batch processes in bio-processing: improved product quality (e.g. for labile products), increased product yield, and cost savings. In this work, a semi-perfusion process was established in shake flasks and transferred to an automated small-scale bioreactor by daily media exchange via centrifugation based on an existing fed-batch process platform. At first the development of a suitable medium and feed composition, the glucose concentration required by the cells and the cell-specific perfusion rate were investigated in shake flasks as the conventional scale-down system. This lead to an optimized process with a threefold higher titer of 10 g/L monoclonal antibody compared to the standard fed-batch. To proof the suitability and benefit as a small-scale model, the established semi-perfusion process was transferred to an automated small-scale bioreactor with improved pH and dissolved oxygen control. The average specific productivity improved from 24.16 pg/(c*d) in the fed-batch process and 36.04 pg/c*d in the semi-perfusion shake flask to 38.88 pg/(c*d) in the semi-perfusion process performed in the controlled small-scale bioreactor, thus illustrating the benefits resulting from the applied semi-perfusion approach, especially in combination with controlled DO and pH settings. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2757, 2019.