Effectiveness of host cell protein removal using depth filtration with a filter containing diatomaceous earth

Multiple Use of Regenerated Depth Filters in Antibody Purification Processes

During the manufacturing of therapeutic antibodies, disposable depth filters are used after affinity chromatography to remove haze and process-related impurities such as host cell proteins (HCP) and DNA known as critical quality attributes. The present study reports on the regeneration of depth filters allowing their reuse for at least 10 times while retaining sufficiently high clarification capacity. Three filter types were evaluated including standard cellulose-based and fully synthetic matrix materials using acidic or alkaline solutions in alternating cycles of loading and regeneration. Both alkaline and acidic solutions were effective, however, overall acidic regeneration of the filter material appeared superior for multiple use. This was especially evident for the silica-containing XOSP filter, where HCP and DNA were almost completely removed and remained low over 10 applications. Simultaneously preserved product quality indicated a high resistance of the filter matrix toward regeneration. These unexpected findings offer improved flexibility for available filter capacity in downstream processing along with ecologic advantages over the single use applications. Regarding the carbon footprint of the filtration process, calculated potential savings by a factor of four can be achieved, mainly accounting for reduced plastic waste. Therefore, depth filter reuse supports sustainability and carbon dioxide reduction during production processes.

Trends and challenges in bispecific antibody production

Bispecific antibodies (bsAbs) represent a rapidly growing field of therapeutic agents. More bsAbs are being approved worldwide and are in various stages of clinical trials. However, the discovery and production of novel bsAbs presents significant challenges due to their complex structure. Thus, precise control of assembly and stability is required, given the many formats developed. This review examines recent trends in bsAb production, focusing on advancements in engineering platforms, production strategies, and challenges in large-scale manufacturing. Key developments include improvements in modular antibody design, novel expression systems, and optimization of bioprocessing techniques to enhance stability, yield, and efficacy. Additionally, the article explores the future potential of bsAbs as next-generation therapeutics, underscoring the growing impact of these innovations on expanding treatment options for patients with unmet medical needs.

The downstream purification of bispecific antibodies

Bispecific antibodies, a class of therapeutic antibodies, can simultaneously bind to two distinct targets. Compared with monospecific antibodies, bispecific antibodies offer advantages, including superior efficacy and reduced side effects. However, because of their structural complexity, the purification of bispecific antibodies is highly challenging. The purification process must strike a delicate balance between purity and productivity, eliminating a broad spectrum of contaminants, including product-related and process-related impurities, while also maximizing the yield wherever feasible. This review systematically describes the strategies for bispecific antibody capture, the elimination of product-related impurities, and the mitigation of the formation of process-related impurities, thereby, providing guidance for the development of downstream purification processes for bispecific antibodies.

Comparative Study of Immobilized Biolipasa-R for Second Generation Biodiesel Production from an Acid Oil

The primary objective of this work is to develop a sustainable biocatalytic transesterification process for low-grade oils, aligning with EU green technology requirements for the shift to second generation biodiesel. Thus, we investigated the immobilization and subsequent application of the lipase Biolipasa-R on transesterification processes to produce fatty acid methyl esters (FAMEs) from both a sunflower oil and an acid oil which is a bioproduct of the biodiesel industry. The lipase was immobilized on biomaterials, such as diatomaceous earth, with a yield of 60 %, and commercial carriers such as methacrylic resins with a yield of 100 %. The enzyme demonstrated superior activity when immobilized on diatomaceous earth, particularly in reactions involving the acid oil, outperforming the benchmark enzyme Novozym® 435 (95.1 % and 35 % conversion respectively). This work highlights the potential of Biolipasa-R as a cost-effective and efficient biocatalyst for biodiesel production and emphasizes the environmental benefits of utilizing industrial byproducts and eco-friendly immobilization techniques. The findings suggest that Biolipasa-R is a promising candidate for industrial applications in biodiesel production, offering a sustainable solution for waste management and energy generation.

Combining descriptive and predictive modeling to systematically design depth filtration-based harvest processes for biologics

Advances in upstream production of biologics-particularly intensified fed-batch processes beyond 10% cell solids-have severely strained harvest operations, especially depth filtration. Bioreactors containing high amounts of cell debris (more than 40% particles <10 µm in diameter) are increasingly common and drive the need for more robust depth filtration processes, while accelerated timelines emphasize the need for predictive tools to accelerate development. Both needs are constrained by the current limited mechanistic understanding of the harvest filter-feedstream system. Historically, process development relied on screening scale-down depth filter devices and conditions to define throughput before fouling, indicated by increasing differential pressure and/or particle breakthrough (measured via turbidity). This approach is straightforward, but resource-intensive, and its results are inherently limited by the variability of the feedstream. Semi-empirical models have been developed from first principles to describe various mechanisms of filter fouling, that is, pore constriction, pore blocking, and/or surface deposit. Fitting these models to experimental data can assist in identifying the dominant fouling mechanism. Still, this approach sees limited application to guide process development, as it is descriptive, not predictive. To address this gap, we developed a hybrid modeling approach. Leveraging historical bench scale filtration process data, we built a partial least squares regression model to predict particle breakthrough from filter and feedstream attributes, and leveraged the model to demonstrate prediction of filter performance a priori. The fouling models are used to interpret and provide physical meaning to these computational models. This hybrid approach-combining the mechanistic insights of fouling models and the predictive capability of computational models-was used to establish a robust platform strategy for depth filtration of Chinese hamster ovary cell cultures. As new data continues to teach the computational models, in silico tools will become an essential part of harvest process development by enabling prospective experimental design, reducing total experimental load, and accelerating development under strict timelines.

Host cell proteins in monoclonal antibody processing: Control, detection, and removal

Host cell proteins (HCPs) are process-related impurities in a therapeutic protein expressed using cell culture technology. This review presents biopharmaceutical industry trends in terms of both HCPs in the bioprocessing of monoclonal antibodies (mAbs) and the capabilities for HCP clearance by downstream unit operations. A comprehensive assessment of currently implemented and emerging technologies in the manufacturing processes with extensive references was performed. Meta-analyses of published downstream data were conducted to identify trends. Improved analytical methods and understanding of "high-risk" HCPs lead to more robust manufacturing processes and higher-quality therapeutics. The trend of higher cell density cultures leads to both higher mAb expression and higher HCP levels. However, HCP levels can be significantly reduced with improvements in operations, resulting in similar concentrations of approx. 10 ppm HCPs. There are no differences in the performance of HCP clearance between recent enhanced downstream operations and traditional batch processing. This review includes best practices for developing improved processes.

Evaluating Nanoparticle Hydrophobicity Using Analytical Membrane Hydrophobic Interaction Chromatography

Nanoparticle hydrophobicity is a key factor controlling the stability, adhesion, and transport of nanoparticle suspensions. Although a number of approaches have been presented for evaluating nanoparticle hydrophobicity, these methods are difficult to apply to larger nanoparticles and viruses (>100 nm in size) that are of increasing importance in drug delivery and gene therapy. This study investigated the use of a new analytical hydrophobic interaction chromatography method employing a 5.0 μm pore size polyvinylidene fluoride membrane as the stationary-phase in membrane hydrophobic interaction chromatography (MHIC). Experimental data obtained using a series of model proteins were in good agreement with literature values for the hydrophobicity (both experimental and computational). MHIC was then used to evaluate the hydrophobicity of a variety of nanoparticles, including a live attenuated viral vaccine, both in water and in the presence of different surfactants. This new method can be implemented on any liquid chromatography system, run times are typically <20 min, and the experiments avoid the use of organic solvents that could alter the structure of many biological nanoparticles.

Analysis of fouling and breakthrough of process related impurities during depth filtration using confocal microscopy

Titer improvement has driven process intensification in mAb manufacture. However, this has come with the drawback of high cell densities and associated process related impurities such as cell debris, host cell protein (HCP), and DNA. This affects the capacity of depth filters and can lead to carryover of impurities to protein A chromatography leading to early resin fouling. New depth filter materials provide the opportunity to remove more process related impurities at this early stage in the process. Hence, there is a need to understand the mechanism of impurity removal within these filters. In this work, the secondary depth filter Millistak+ X0HC (cellulose and diatomaceous earth) is compared with the X0SP (synthetic), by examining the breakthrough of DNA and HCP. Additionally, a novel method was developed to image the location of key impurities within the depth filter structure under a confocal microscope. Flux, tested at 75, 100, and 250 LMH was found to affect the maximal throughput based on the max pressure of 30 psi, but no significant changes were seen in the HCP and DNA breakthrough. However, a drop in cell culture viability, from 87% to 37%, lead to the DNA breakthrough at 10% decreasing from 81 to 55 L/m² for X0HC and from 105 to 47 L/m² for X0SP. The HCP breakthrough was not affected by cell culture viability or filter type. The X0SP filter has a 30%-50% higher max throughput depending on viability, which can be explained by the confocal imaging where the debris and DNA are distributed differently in the layers of the filter pods, with more of the second tighter layer being utilized in the X0SP.

Scale-up Issues for Commercial Depth Filters in Bioprocessing

Significant increases in cell density and product titer have led to renewed interest in the application of depth filtration for initial clarification of cell culture fluid in antibody production. The performance of these depth filters will depend on the local pressure and velocity distribution within the filter capsule, but these are very difficult to probe experimentally, leading to challenges in both process design and scale-up. We have used a combination of carefully designed experimental studies and computational fluid dynamics (CFD) to examine these issues in both lab-scale (Supracap^TM 50) and pilot-scale (Stax^TM ) depth filter modules, both employing dual-layer lenticular PDH4 media containing diatomaceous earth. The Supracap^TM 50 showed a more rapid increase in transmembrane pressure and a more rapid DNA breakthrough during filtration of a Chinese Hamster Ovary cell culture fluid. These results were explained using CFD calculations which showed very different flow distributions within the modules. CFD predictions were further validated using measurements of the residence time distribution and dye binding in both the lab-scale and pilot-plant modules. These results provide important insights into the factors controlling the performance and scale-up of these commercially important depth filters as well as a framework that can be broadly applied to develop more effective depth filters and depth filtration processes. This article is protected by copyright. All rights reserved.