(233c) Upstream Process Characterization Utilizing Response Surface Experimental Design: Case Study for a GS-NS0 Monoclonal Antibody Production Process

Process characterization is a systematic investigation into a production process and yields valuable information on performance and product quality attributes. The main goals of the characterization studies are to identify Key Operating Parameters (KOP) and Critical Process Parameters (CPP), define operating ranges for those parameters, and demonstrate process robustness. In addition to identifying acceptable operating ranges, setting recommended operating ranges within the acceptable limits is crucial to a robust process. Prior to beginning experimental studies aimed at defining the cell culture process, a Failure Mode Effects Analysis (FMEA) was completed based on previous process and equipment knowledge. Following the risk analysis, which prioritized the process parameters with the highest likeliness of failure, the characterization of the GS-NS0 fed-batch process was completed using a response surface experimental design in a 3-L stirred bioreactor scale-down model. The process parameters that were studied were temperature, pH, dissolved oxygen, inoculation density, feed timing, medium concentration, and feed concentration. These studies quantified the effects of the process parameters on cell growth, cell viability, antibody production, binding affinity, glycan distribution, and charge variant distribution, and identified temperature and pH as CPPs and inoculation density as a KOP. The other investigated parameters were determined to be non-key parameters. The characterization of this GS-NS0 fed-batch process provided necessary information to set recommended and acceptable operating ranges for the process parameters. It also highlighted process sensitivities and failure limits, which were useful during process scale-up and technology transfer to the manufacturing facility. Further, short-term excursion studies were performed to evaluate the effect of process control drifts beyond the acceptable operating range. The response surface experimental design worked well as a tool to characterize the fed-batch process. This design enabled the detailed mapping of operating space for the evaluated parameters and provided information necessary to identify the critical parameters for this process.