Issue link: https://www.e-digitaleditions.com/i/1468049
Pharmaceutical Technology TRENDS IN MANUFACTURING 2022 eBOOK 33 purification process has to be robust against the variations of the cell culture process, the material harvested from the bioreactor, and the variations in the chromatography steps. With a conventional protein A matrix, a very low pH (i.e., around 3 pH), can cause aggregation of the antibody. This aggregation represents a safety risk (because antibody aggregates are impurities, potentially triggering an immune reaction in the patient if they are present in the drug product) and a burden for the downstream steps, which need to remove these formed aggregates, thus causing a reduced yield. The new matrix ZCa has a ligand based on calcium; the presence or absence of the li- gand switches the antibody-binding ability of ZCa at mild pH. In the capture step, this switch is used first to bind the antibody, then to release it. Since low pH does not need to be used, the amount of ag- gregates is close to zero. Since it is not necessary to remove the aggregates, the yield is very high. The potential of this matrix was demonstrated in this project at pilot scale during 300 cycles. PharmTech: What is the importance of automa- tion in continuous bioprocessing? Chotteau (AdBIOPRO): Without automation, a con- tinuous process is not possible. A well-realized automation of a continuous purification process actually provides higher yields compared to a batch process because no material is lost. We had a yield of 90% for a purification process con- taining three chromatography steps and a virus reduction step. This high yield was due to the automated continuous purification process, the efficient design, and the new ligand of protein A that eliminated aggregation. Even before perfusion became popular for robust molecules such as antibodies, this mode of opera- tion was already being used for labile proteins, such as therapeutic enzymes. The automatic renewal of cell culture medium provided in perfusion culture is highly beneficial for the cells and the product of interest, which is constantly removed from the bioreactor and separated from any proteolytic action and other deterioration. Nowadays, many antibody-derived molecules, such as bi-specific antibodies, are in biopharma drug development pipelines. These new therapeutic drugs are more challenging to manufacture than traditional anti- bodies, and a perfusion operation can answer that challenge. In contrast with fed-batch, where the quality profile varies with time, perfusion culture has demonstrated a stable product quality pro- file over time at steady-state conditions. However, other researchers have reported that the product quality profile can sometimes have a drift with time. The implementation of PAT combined with automation could possibly counteract this drift. PharmTech: What are some of the uses of PAT in continuous bioprocessing? Chotteau (AdBIOPRO): We could have advanta- geously included more PAT [in the scale-up proj- ect]. PAT could be a tool to tune the quality pro- file, for instance, or to improve the robustness of the continuous process with the help of feedback control. We have recently developed monitoring of antibody glycosylation with a Raman probe "Without automation, a continuous process is not possible." — Veronique Chotteau, AdBIOPRO