Design and optimization of Single Pass Tangential Flow Filtration for inline concentration of monoclonal antibodies

Intramodule pressure profiles and protein accumulation during tangential flow filtration

Tangential flow filtration (TFF) through a 30 kDa nominal molecular weight cut-off (MWCO) ultrafiltration membrane is widely employed to concentrate purified monoclonal antibodies (mAbs) to levels required for their formulation into injectable biologics. While TFF has been used to remove casein from milk for cheese production for over 35 years, and in pharmaceutical manufacture of biotherapeutic proteins for 20 years, the rapid decline in filtration rate (i.e., flux) at high protein concentrations is a limitation that still needs to be addressed. This is particularly important for mAbs, many of which are 140-160 kDa immunoglobulin G (IgG) type proteins recovered at concentrations of 200 mg/mL or higher. This work reports the direct measurement of local transmembrane pressure drops and off-line confocal imaging of protein accumulation in stagnant regions on the surface of a 30 kDa regenerated cellulose membrane in a flat-sheet configuration widely used in manufacture of biotherapeutic proteins. These first-of-a-kind measurements using 150 kDa bovine IgG show that while axial pressure decreases by 58 psi across a process membrane cassette, the decrease in transmembrane pressure drop is constant at about 1.2 psi/cm along the 20.7 cm length of the membrane. Confocal laser scanning microscopy of the membrane surface at the completion of runs where retentate protein concentration exceeds 200 mg/mL, shows a 50 μm thick protein layer is uniformly deposited. The localized measurements made possible by the modified membrane system confirm the role of protein deposition on limiting ultrafiltration rate and indicate possible targets for improving membrane performance.

Efficiency of ultrafiltration/diafiltration in removing organic and elemental process equipment related leachables from biological therapeutics

In the production of biological therapeutics such as monoclonal antibodies (mAbs), ultrafiltration and diafiltration (UF/DF) are widely regarded as effective downstream processing steps capable of removing process equipment related leachables (PERLs) introduced upstream of the UF/DF step. However, clearance data available in the literature are limited to species with low partition coefficients (log P) such as buffer ions, hydrophilic organic compounds, and some metal ions. Additional data for a wide range of PERLs including hydrophobic compounds and elemental impurities are needed to establish meaningful, comprehensive safety risk assessments. Herein, we report the results from studies investigating the clearance of seven different organic PERLs representing a wide range of characteristics (i.e., log P (-0.3 to 18)), and four model elements with different chemical properties spiked into a mAb formulation at 10 ppm and analyzed during clearance using gas chromatography-mass spectrometry (GC-MS), liquid chromatography-photodiode-array-mass spectrometry (LC-PDA-MS), and inductively coupled plasma mass spectrometry (ICP-MS). The clearance data showed ideal clearance and sieving of spiked organic PERLs with log P < 4, partial clearance of PERLs with 4 < log P < 9, and poor clearance of highly hydrophobic PERLs (log P > 9) after nine diafiltration volumes (DVs). Supplemental clearance studies on seven additional PERLs present at much lower concentration levels (0.1-1.5 ppm) in the mAb formulation upstream of UF/DF and three PERLs associated with the tangential flow filtration (TFF) equipment also demonstrated the similar correlations between log P and % clearance. For model elements, the findings suggest that UF/DF in general provides ideal clearance for elements. Evidence showed that the UF/DF process does not only help mitigate leachables risk from PERLs introduced upstream of UF/DF, but also from the TFF operation itself as all three TFF-related PERLs were effectively cleared. Overall, the UF/DF clearance presented in this work demonstrated whereas highly hydrophobic PERLs and elements that exist as charged species, particularly transition metal ions, may not be as effectively cleared and thus warrant further risk assessment; hydrophilic and some hydrophobic PERLs (log P < 4) are indeed well-cleared and thus present a lower overall safety risk.

Predictive modeling of single pass tangential flow filtration for continuous biomanufacturing

Opportunities for process intensification have made continuous biomanufacturing an area of active research. While tangential flow filtration (TFF) is typically employed within the biologics purification train to increase drug substance concentration, single-pass TFF (SPTFF) modifies its format by enabling continuity of this process and achieving a multifold concentration factor through a single-pass over the filtration membranes. In continuous processes feed concentration and flow rate are determined by the preceding unit operations. Therefore, tight control of SPTFF output concentration must be achieved through precise design of the membrane configuration, unlike TFF. However, predictive modeling can be utilized to identify configurations that achieve a desired target concentration across ranges of possible feed conditions with minimal experimental data, hence enabling accelerated process development and design flexibility. We hereby describe the development of a mechanistic model predicting SPTFF performance across a wide design space using the well-established stagnant film model, which we demonstrate is more accurate at higher feed flow rates. The flux excursion dataset was generated within time constraints and with minimal material consumption, showing the method's ability to be quickly adapted. While this approach eliminates characterizing complex physicochemical model variables or the need for users with specialized training, the model and its assumptions become inaccurate at low flow rates, below 25 L/m2 /h, and high conversions, above 0.9. As this low flow rate, high conversion operating regime is relevant for continuous biomanufacturing, we explore the assumptions and challenges involved in predicting and modeling SPTFF processes, while suggesting added characterization to gain further process insight.

Bridging the gap between fundamental research and product development of long acting injectable PLGA microspheres

INTRODUCTION

Long acting Injectable PLGA microspheres have gained more and more interest and attention in the field of life cycle management of pharmaceutical products due to their biocompatibility and biodegradability. So far, a multitude of trial-and-error experiments at lab scale have been used for establishing the correlation relationship between critical process parameters, critical material attributes and critical quality attributes. However, few published studies have elaborated on the development of PLGA microspheres from an industrial perspective.

AREAS COVERED

In this review, the scale-up feasibility of translational technologies of PLGA microspheres manufacturing have been evaluated. Additionally, state-of-the-art of technologies and facilities in PLGA development have been summarized. Meanwhile, the industrial knowledge matrix of PLGA microspheres development and research are establishing which provide comprehensive insight for understanding properties of PLGA microspheres as controlled/sustained release vehicle.

EXPERT OPINION

There is still big gap between fundamental research in academic institute and product development in pharmaceuticals. Therefore, the difference and connection between them should be identified gradually for better understanding of PLGA microspheres development.