4. Conclusions
The end-to-end continuous process for mAb purification reported in this study has upstream and downstream steps with pool-less direct connections and a low pH inactivation step with automated pH adjustment performed in batch mode, which serves as a batch demarcation and also allows for feed adjustment before and after the low pH inactivation step. These characteristic properties make the process amenable for continuous mAb production. Furthermore, the mAb production experiment by the scale-down model of this report confirmed that this continuous process results in high productivity and high purity of mAb. The mAb was highly purified by the total flow-through integrated polishing process in which two columns (AEX and CEX) were directly connected to the virus filter. As a result, even with a filtration throughput of about 1000 L/m2, filtration pressure increases on the virus filter were extremely small, demonstrating that high purification and extremely stable virus filtration can be realized in the end-to-end continuous process for mAb purification.
Regarding virus reduction, both the flow-through two column chromatography and the virus filter showed robust virus removability for the total flow-through integrated polishing process. While virus filtration is usually carried out by constant pressure filtration and is not easily incorporated into a continuous process, the hollow fiber type virus filters tested in this study showed high virus reduction even at very low flux and with a process pause that may be observed in continuous processing. For very low flux of 1.5 LMH and a condition with process pause of 60 min, both Planova BioEX and S20N showed virus LRV of > 4, indicating that these hollow fiber type virus filters are highly applicable for the continuous process with high filterability and robust virus removability.