Development of Ultrafiltration and Diafiltration Processes for Batch and Continuous Formulation of Monoclonal Antibodies
Open Access
- Author:
- Jabra, Mario
- Graduate Program:
- Chemical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- November 06, 2021
- Committee Members:
- Andrew Zydney, Chair & Dissertation Advisor
William Hancock, Outside Unit & Field Member
Wayne Curtis, Major Field Member
Darrell Velegol, Major Field Member
Seong H. Kim, Professor in Charge/Director of Graduate Studies - Keywords:
- Ultrafiltration
Diafiltration
Continuous
Multistage countercurrent
pH shift
Excipient Shift
Bioprocessing
membrane filtration
Single Pass tangential flow filtration
SPTFF
Mechanistic Modelling
SPTFF optimization
Buffer Exchange
Countercurrent Dialysis
Continuous Ultrafiltration
Continuous Diafiltration
Membrane Processing
Monoclonal Antibody
IgG
Therapeutic Protein
Formulation - Abstract:
- There is growing interest among biopharmaceutical companies in the development of fully integrated continuous processes for the manufacture of monoclonal antibodies (mAbs). These continuous processes have the potential to significantly reduce manufacturing costs, enhance product quality, and provide greater flexibility to respond to changes in market demands. The objective of this thesis was to explore the development of novel strategies for antibody concentration and buffer exchange, both of which are critical in the final formulation step, using membrane ultrafiltration (UF) and diafiltration (DF). Diafiltration is currently used to perform buffer exchange and desalting. However, this is an inherently batch process, requiring prolonged recirculation of the antibody solution through a membrane module containing a highly retentive ultrafiltration membrane. Chapter 2 of this thesis presents results for a continuous 3-stage countercurrent diafiltration process that was able to provide 99.9% removal of a model impurity, with constant operation for 24 hrs. An alternative approach for buffer exchange was explored in Chapter 3 using a countercurrent dialysis process. This system was not only able to provide very high degrees of impurity removal, it also used less buffer and much less expensive membrane modules than current batch operations. Single Pass Tangential Flow Filtration (SPTFF) systems have recently been developed for continuous inline concentration using ultrafiltration modules with a long flow path length used to achieve high conversion in a single pass. However, the high conversion in SPTFF modules leads to large variations in local flow rate, protein concentration, and transmembrane pressure drop through the module, significantly complicating the design of effective SPTFF processes. Chapter 4 examined the development of a numerical model for the filtrate flux and conversion in SPTFF modules specifically accounting for the effects of intermolecular interactions on the viscosity and osmotic pressure of the antibody solution. Model predictions were validated using experimental data obtained with a highly purified monoclonal antibody product in several different SPTFF modules. This model was then used in Chapter 5 to examine the design and optimization of SPTFF modules to achieve specific process objectives. There is growing interest in formulating monoclonal antibody products in low-buffered or bufferless media. One challenge with the use of diafiltration under these conditions is the large shift in pH and excipient concentrations that are commonly seen over the course of the diafiltration. The main objective of Chapter 6 was to develop a model for the pH and excipient concentration based on Donnan equilibrium and electroneutrality constraints that incorporates the effects of both pH and ionic strength on the mAb charge through the use of a charge regulation model. The model involves no adjustable parameters, with the protein charge evaluated directly from the protonation / deprotonation of the ionizable amino acids in the protein structure. Experimental results were shown to be in excellent agreement with model calculations for multiple mAb products over a range of conditions. This model was then extended to evaluate the pH shifts seen in both batch ultrafiltration and continuous SPTFF processes in Chapter 7. In total, the results presented in this thesis provide important insights into the development of ultrafiltration and diafiltration processes for the concentration / formulation of monoclonal antibody products in both continuous and batch operations.