Biological differences between adult and perinatal human mesenchymal stromal cells and their impact on the manufacturing processes.

The biological properties of human mesenchymal stromal cells (hMSCs) have been explored in over a thousand clinical trials in the last decade. Although hMSCs can be isolated from multiple sources, the degree of biological similarity between cell populations from these sources remains to be determined. A comparative study was performed investigating the growth kinetics and functionality of hMSCs isolated from adipose tissue (AT), bone marrow (BM) and umbilical cord tissue (UCT) expanded in monolayer over five passages. Adult hMSCs (AT, BM) had a slower proliferation ability than the UCT-hMSCs, with no apparent differences in their glucose consumption profile. BM-hMSCs produced higher concentrations of endogenous vascular endothelial growth factor (VEGF) compared to AT- and UCT-hMSCs. This study also revealed that UCT-hMSCs were more efficiently transduced by a lentiviral vector carrying a VEGF gene than their adult counterparts. Following cellular immunophenotypic characterization, no differences across the sources were found in the expression levels of the typical markers used to identify hMSCs. This work established a systematic approach for cell source selection depending on the hMSC's intended clinical application.

Scalable manufacturing of gene-modified human mesenchymal stromal cells with microcarriers in spinner flasks.

Due to their immunomodulatory properties and in vitro differentiation ability, human mesenchymal stromal cells (hMSCs) have been investigated in more than 1000 clinical trials over the last decade. Multiple studies that have explored the development of gene-modified hMSC-based products are now reaching early stages of clinical trial programmes. From an engineering perspective, the challenge lies in developing manufacturing methods capable of producing sufficient doses of ex vivo gene-modified hMSCs for clinical applications. This work demonstrates, for the first time, a scalable manufacturing process using a microcarrier-bioreactor system for the expansion of gene-modified hMSCs. Upon isolation, umbilical cord tissue mesenchymal stromal cells (UCT-hMSCs) were transduced using a lentiviral vector (LV) with green fluorescent protein (GFP) or vascular endothelial growth factor (VEGF) transgenes. The cells were then seeded in 100 mL spinner flasks using Spherecol microcarriers and expanded for seven days. After six days in culture, both non-transduced and transduced cell populations attained comparable maximum cell concentrations (≈1.8 × 105 cell/mL). Analysis of the culture supernatant identified that glucose was fully depleted after day five across the cell populations. Lactate concentrations observed throughout the culture reached a maximum of 7.5 mM on day seven. Immunophenotype analysis revealed that the transduction followed by an expansion step was not responsible for the downregulation of the cell surface receptors used to identify hMSCs. The levels of CD73, CD90, and CD105 expressing cells were above 90% for the non-transduced and transduced cells. In addition, the expression of negative markers (CD11b, CD19, CD34, CD45, and HLA-DR) was also shown to be below 5%, which is aligned with the criteria established for hMSCs by the International Society for Cell and Gene Therapy (ISCT). This work provides a foundation for the scalable manufacturing of gene-modified hMSCs which will overcome a significant translational and commercial bottleneck. KEY POINTS: • hMSCs were successfully transduced by lentiviral vectors carrying two different transgenes: GFP and VEGF • Transduced hMSCs were successfully expanded on microcarriers using spinner flasks during a period of 7 days • The genetic modification step did not cause any detrimental impact on the hMSC immunophenotype characteristics.

Understanding the impact of bioactive coating materials for human mesenchymal stromal cells and implications for manufacturing.

Bioactive materials interact with cells and modulate their characteristics which enable the generation of cell-based products with desired specifications. However, their evaluation and impact are often overlooked when establishing a cell therapy manufacturing process. In this study, we investigated the role of different surfaces for tissue culture including, untreated polystyrene surface, uncoated Cyclic Olefin Polymer (COP) and COP coated with collagen and recombinant fibronectin. It was observed that human mesenchymal stromal cells (hMSCs) expanded on COP-coated plates with different bioactive materials resulted in improved cell growth kinetics compared to traditional polystyrene plates and non-coated COP plates. The doubling time obtained was 2.78 and 3.02 days for hMSC seeded in COP plates coated with collagen type I and recombinant fibronectin respectively, and 4.64 days for cells plated in standard polystyrene treated plates. Metabolite analysis reinforced the findings of the growth kinetic studies, specifically that cells cultured on COP plates coated with collagen I and fibronectin exhibited improved growth as evidenced by a higher lactate production rate (9.38 × 105 and 9.67 × 105 pmol/cell/day, respectively) compared to cells from the polystyrene group (5.86 × 105 pmol/cell/day). This study demonstrated that COP is an effective alternative to polystyrene-treated plates when coated with bioactive materials such as collagen and fibronectin, however COP-treated plates without additional coatings were found not to be sufficient to support cell growth. These findings demonstrate the key role biomaterials play in the cell manufacturing process and the importance of optimising this selection.

Smart Sensor Control and Monitoring of an Automated Cell Expansion Process.

Immune therapy for cancer patients is a new and promising area that in the future may complement traditional chemotherapy. The cell expansion phase is a critical part of the process chain to produce a large number of high-quality, genetically modified immune cells from an initial sample from the patient. Smart sensors augment the ability of the control and monitoring system of the process to react in real-time to key control parameter variations, adapt to different patient profiles, and optimize the process. The aim of the current work is to develop and calibrate smart sensors for their deployment in a real bioreactor platform, with adaptive control and monitoring for diverse patient/donor cell profiles. A set of contrasting smart sensors has been implemented and tested on automated cell expansion batch runs, which incorporate advanced data-driven machine learning and statistical techniques to detect variations and disturbances of the key system features. Furthermore, a 'consensus' approach is applied to the six smart sensor alerts as a confidence factor which helps the human operator identify significant events that require attention. Initial results show that the smart sensors can effectively model and track the data generated by the Aglaris FACER bioreactor, anticipate events within a 30 min time window, and mitigate perturbations in order to optimize the key performance indicators of cell quantity and quality. In quantitative terms for event detection, the consensus for sensors across batch runs demonstrated good stability: the AI-based smart sensors (Fuzzy and Weighted Aggregation) gave 88% and 86% consensus, respectively, whereas the statistically based (Stability Detector and Bollinger) gave 25% and 42% consensus, respectively, the average consensus for all six being 65%. The different results reflect the different theoretical approaches. Finally, the consensus of batch runs across sensors gave even higher stability, ranging from 57% to 98% with an average consensus of 80%.

Design and development of a new ambr250® bioreactor vessel for improved cell and gene therapy applications.

The emergence of cell and gene therapies has generated significant interest in their clinical and commercial potential. However, these therapies are prohibitively expensive to manufacture and can require extensive time for development due to our limited process knowledge and understanding. The automated ambr250® stirred-tank bioreactor platform provides an effective platform for high-throughput process development. However, the original dual pitched-blade 20 mm impeller and baffles proved sub-optimal for cell therapy candidates that require suspension of microcarriers (e.g. for the culture of adherent human mesenchymal stem cells) or other particles such as activating Dynabeads® (e.g. for the culture of human T-cells). We demonstrate the development of a new ambr250® stirred-tank bioreactor vessel which has been designed specifically to improve the suspension of microcarriers/beads and thereby improve the culture of such cellular systems. The new design is unbaffled and has a single, larger elephant ear impeller. We undertook a range of engineering and physical characterizations to determine which vessel and impeller configuration would be most suitable for suspension based on the minimum agitation speed (NJS) and associated specific power input (P/V)JS. A vessel (diameter, T, = 60 mm) without baffles and incorporating a single elephant ear impeller (diameter 30 mm and 45° pitch-blade angle) was selected as it had the lowest (P/V)JS and therefore potentially, based on Kolmogorov concepts, was the most flexible system. These experimentally-based conclusions were further validated firstly with computational fluid dynamic (CFD) simulations and secondly experimental studies involving the culture of both T-cells with Dynabeads® and hMSCs on microcarriers. The new ambr250® stirred-tank bioreactor successfully supported the culture of both cell types, with the T-cell culture demonstrating significant improvements compared to the original ambr250® and the hMSC-microcarrier culture gave significantly higher yields compared with spinner flask cultures. The new ambr250® bioreactor vessel design is an effective process development tool for cell and gene therapy candidates and potentially for autologous manufacture too.

Establishing the scalable manufacture of primary human T-cells in an automated stirred-tank bioreactor.

Advanced cell and gene therapies such as chimeric antigen receptor T-cell immunotherapies (CAR-T), present a novel therapeutic modality for the treatment of acute and chronic conditions including acute lymphoblastic leukemia and non-Hodgkin lymphoma. However, the development of such immunotherapies requires the manufacture of large numbers of T-cells, which remains a major translational and commercial bottleneck due to the manual, small-scale, and often static culturing systems used for their production. Such systems are used because there is an unsubstantiated concern that primary T-cells are shear sensitive, or prefer static conditions, and therefore do not grow as effectively in more scalable, agitated systems, such as stirred-tank bioreactors, as compared with T-flasks and culture bags. In this study, we demonstrate that not only T-cells can be cultivated in an automated stirred-tank bioreactor system (ambr® 250), but that their growth is consistently and significantly better than that in T-flask static culture, with equivalent cell quality. Moreover, we demonstrate that at progressively higher agitation rates over the range studied here, and thereby, higher specific power inputs (P/M W kg-1 ), the higher the final viable T-cell density; that is, a cell density of 4.65 ± 0.24 × 106 viable cells ml-1 obtained at the highest P/M of 74 × 10-4 W kg-1 in comparison with 0.91 ± 0.07 × 106 viable cells ml-1 at the lowest P/M of 3.1 × 10-4 W kg-1 . We posit that this improvement is due to the inability at the lower agitation rates to effectively suspend the Dynabeads®, which are required to activate the T-cells; and that contact between them is improved at the higher agitation rates. Importantly, from the data obtained, there is no indication that T-cells prefer being grown under static conditions or are sensitive to fluid dynamic stresses within a stirred-tank bioreactor system at the agitation speeds investigated. Indeed, the opposite has proven to be the case, whereby, the cells grow better under higher agitation speeds while maintaining their quality. This study is the first demonstration of primary T-cell ex vivo manufacture activated by Dynabeads® in an automated stirred-tank bioreactor system such as the ambr® 250 and the findings have the potential to be applied to multiple other cell candidates for advanced therapy applications.

Centralised versus decentralised manufacturing and the delivery of healthcare products: A United Kingdom exemplar.

BACKGROUND: The cell and gene therapy (CGT) field is at a critical juncture. Clinical successes have underpinned the requirement for developing manufacturing capacity suited to patient-specific therapies that can satisfy the eventual demand post-launch. Decentralised or 'redistributed' manufacturing divides manufacturing capacity across geographic regions, promising local, responsive manufacturing, customised to the end user, and is an attractive solution to overcome challenges facing the CGT manufacturing chain. METHODS: A study was undertaken building on previous, so far unpublished, semi-structured interviews with key opinion leaders in advanced therapy research, manufacturing and clinical practice. The qualitative findings were applied to construct a cost of goods model that permitted the cost impact of regional siting to be combined with variable and fixed costs of manufacture of a mesenchymal stromal cell product. RESULTS: Using the United Kingdom as an exemplar, cost disparities between regions were examined. Per patient dose costs of ~£1,800 per 75,000,000 cells were observed. Financial savings from situating the facility outside of London allow 25-41 additional staff or 24-35 extra manufacturing vessels to be employed. Decentralised quality control to mitigate site-to-site variation was examined. Partial decentralisation of quality control was observed to be financially possible and an attractive option for facilitating release 'at risk'. DISCUSSION: There are important challenges that obstruct the easy adoption of decentralised manufacturing that have the potential to undermine the market success of otherwise promising products. By using the United Kingdom as an exemplar, the modelled data provide a framework to inform similar regional policy considerations across other global territories.

Decentralized manufacturing of cell and gene therapies: Overcoming challenges and identifying opportunities.

Decentralized or "redistributed" manufacturing has the potential to revolutionize the manufacturing approach for cell and gene therapies (CGTs), moving away from the "Fordist" paradigm, delivering health care locally, customized to the end user and, by its very nature, overcoming many of the challenges associated with manufacturing and distribution of high volume goods. In departing from the traditional centralized model of manufacturing, decentralized manufacturing divides production across sites or geographic regions. This paradigm shift imposes significant structural and organisational changes on a business presenting both hidden challenges that must be addressed and opportunities to be embraced. By profoundly adapting business practices, significant advantages can be realized through a democratized value chain, creation of professional-level jobs without geographic restriction to the central hub and a flexibility in response to external pressures and demands. To realize these potential opportunities, however, advances in manufacturing technology and support systems are required, as well as significant changes in the way CGTs are regulated to facilitate multi-site manufacturing. Decentralized manufacturing is likely to be the manufacturing platform of choice for advanced health care therapies-in particular, those with a high degree of personalization. The future success of these promising products will be enhanced by adopting sound business strategies early in development. To realize the benefits that decentralized manufacturing of CGTs has to offer, it is important to examine both the risks and the substantial opportunities present. In this research, we examine both the challenges and the opportunities this shift in business strategy represents in an effort to maximize the success of adoption.

Process development of human multipotent stromal cell microcarrier culture using an automated high-throughput microbioreactor.

Microbioreactors play a critical role in process development as they reduce reagent requirements and can facilitate high-throughput screening of process parameters and culture conditions. Here, we have demonstrated and explained in detail, for the first time, the amenability of the automated ambr15 cell culture microbioreactor system for the development of scalable adherent human mesenchymal multipotent stromal/stem cell (hMSC) microcarrier culture processes. This was achieved by first improving suspension and mixing of the microcarriers and then improving cell attachment thereby reducing the initial growth lag phase. The latter was achieved by using only 50% of the final working volume of medium for the first 24 h and using an intermittent agitation strategy. These changes resulted in >150% increase in viable cell density after 24 h compared to the original process (no agitation for 24 h and 100% working volume). Using the same methodology as in the ambr15, similar improvements were obtained with larger scale spinner flask studies. Finally, this improved bioprocess methodology based on a serum-based medium was applied to a serum-free process in the ambr15, resulting in >250% increase in yield compared to the serum-based process. At both scales, the agitation used during culture was the minimum required for microcarrier suspension, NJS . The use of the ambr15, with its improved control compared to the spinner flask, reduced the coefficient of variation on viable cell density in the serum containing medium from 7.65% to 4.08%, and the switch to serum free further reduced these to 1.06-0.54%, respectively. The combination of both serum-free and automated processing improved the reproducibility more than 10-fold compared to the serum-based, manual spinner flask process. The findings of this study demonstrate that the ambr15 microbioreactor is an effective tool for bioprocess development of hMSC microcarrier cultures and that a combination of serum-free medium, control, and automation improves both process yield and consistency. Biotechnol. Bioeng. 2017;114: 2253-2266. © 2017 Wiley Periodicals, Inc.

Scalability and process transfer of mesenchymal stromal cell production from monolayer to microcarrier culture using human platelet lysate.

BACKGROUND AIMS: The selection of medium and associated reagents for human mesenchymal stromal cell (hMSC) culture forms an integral part of manufacturing process development and must be suitable for multiple process scales and expansion technologies. METHODS: In this work, we have expanded BM-hMSCs in fetal bovine serum (FBS)- and human platelet lysate (HPL)-containing media in both a monolayer and a suspension-based microcarrier process. RESULTS: The introduction of HPL into the monolayer process increased the BM-hMSC growth rate at the first experimental passage by 0.049 day and 0.127/day for the two BM-hMSC donors compared with the FBS-based monolayer process. This increase in growth rate in HPL-containing medium was associated with an increase in the inter-donor consistency, with an inter-donor range of 0.406 cumulative population doublings after 18 days compared with 2.013 in FBS-containing medium. Identity and quality characteristics of the BM-hMSCs are also comparable between conditions in terms of colony-forming potential, osteogenic potential and expression of key genes during monolayer and post-harvest from microcarrier expansion. BM-hMSCs cultured on microcarriers in HPL-containing medium demonstrated a reduction in the initial lag phase for both BM-hMSC donors and an increased BM-hMSC yield after 6 days of culture to 1.20 ± 0.17 × 10(5) and 1.02 ± 0.005 × 10(5) cells/mL compared with 0.79 ± 0.05 × 10(5) and 0.36 ± 0.04 × 10(5) cells/mL in FBS-containing medium. CONCLUSIONS: This study has demonstrated that HPL, compared with FBS-containing medium, delivers increased growth and comparability across two BM-hMSC donors between monolayer and microcarrier culture, which will have key implications for process transfer during scale-up.

Serum-free process development: improving the yield and consistency of human mesenchymal stromal cell production.

BACKGROUND AIMS: The cost-effective production of human mesenchymal stromal cells (hMSCs) for off-the-shelf and patient specific therapies will require an increasing focus on improving product yield and driving manufacturing consistency. METHODS: Bone marrow-derived hMSCs (BM-hMSCs) from two donors were expanded for 36 days in monolayer with medium supplemented with either fetal bovine serum (FBS) or PRIME-XV serum-free medium (SFM). Cells were assessed throughout culture for proliferation, mean cell diameter, colony-forming potential, osteogenic potential, gene expression and metabolites. RESULTS: Expansion of BM-hMSCs in PRIME-XV SFM resulted in a significantly higher growth rate (P < 0.001) and increased consistency between donors compared with FBS-based culture. FBS-based culture showed an inter-batch production range of 0.9 and 5 days per dose compared with 0.5 and 0.6 days in SFM for each BM-hMSC donor line. The consistency between donors was also improved by the use of PRIME-XV SFM, with a production range of 0.9 days compared with 19.4 days in FBS-based culture. Mean cell diameter has also been demonstrated as a process metric for BM-hMSC growth rate and senescence through a correlation (R(2) = 0.8705) across all conditions. PRIME-XV SFM has also shown increased consistency in BM-hMSC characteristics such as per cell metabolite utilization, in vitro colony-forming potential and osteogenic potential despite the higher number of population doublings. CONCLUSIONS: We have increased the yield and consistency of BM-hMSC expansion between donors, demonstrating a level of control over the product, which has the potential to increase the cost-effectiveness and reduce the risk in these manufacturing processes.

Expansion, harvest and cryopreservation of human mesenchymal stem cells in a serum-free microcarrier process.

Human mesenchymal stem cell (hMSC) therapies are currently progressing through clinical development, driving the need for consistent, and cost effective manufacturing processes to meet the lot-sizes required for commercial production. The use of animal-derived serum is common in hMSC culture but has many drawbacks such as limited supply, lot-to-lot variability, increased regulatory burden, possibility of pathogen transmission, and reduced scope for process optimization. These constraints may impact the development of a consistent large-scale process and therefore must be addressed. The aim of this work was therefore to run a pilot study in the systematic development of serum-free hMSC manufacturing process. Human bone-marrow derived hMSCs were expanded on fibronectin-coated, non-porous plastic microcarriers in 100 mL stirred spinner flasks at a density of 3 × 10(5) cells.mL(-1) in serum-free medium. The hMSCs were successfully harvested by our recently-developed technique using animal-free enzymatic cell detachment accompanied by agitation followed by filtration to separate the hMSCs from microcarriers, with a post-harvest viability of 99.63 ± 0.03%. The hMSCs were found to be in accordance with the ISCT characterization criteria and maintained hMSC outgrowth and colony-forming potential. The hMSCs were held in suspension post-harvest to simulate a typical pooling time for a scaled expansion process and cryopreserved in a serum-free vehicle solution using a controlled-rate freezing process. Post-thaw viability was 75.8 ± 1.4% with a similar 3 h attachment efficiency also observed, indicating successful hMSC recovery, and attachment. This approach therefore demonstrates that once an hMSC line and appropriate medium have been selected for production, multiple unit operations can be integrated to generate an animal component-free hMSC production process from expansion through to cryopreservation.

Development of novel lipoplex formulation methodologies to improve large-scale transient transfection for lentiviral vector manufacture.

Large-scale transient transfection has advanced significantly over the last 20 years, enabling the effective production of a diverse range of biopharmaceutical products, including viral vectors. However, a number of challenges specifically related to transfection reagent stability and transfection complex preparation times remain. New developments and improved transfection technologies are required to ensure that transient gene expression-based bioprocesses can meet the growing demand for viral vectors. In this paper, we demonstrate that the growth of cationic lipid-based liposomes, an essential step in many cationic lipid-based transfection processes, can be controlled through adoption of low pH (pH 6.40 to pH 6.75) and in low salt concentration (0.2× PBS) formulations, facilitating improved control over the nanoparticle growth kinetics and enhancing particle stability. Such complexes retain the ability to facilitate efficient transfection for prolonged periods compared with standard preparation methodologies. These findings have significant industrial applications for the large-scale manufacture of lentiviral vectors for two principal reasons. First, the alternative preparation strategy enables longer liposome incubation times to be used, facilitating effective control in a good manufacturing practices setting. Second, the improvement in particle stability facilitates the setting of wider process operating ranges, which will significantly improve process robustness and maximise batch-to-batch control and product consistency.

Degradation of specific glycosaminoglycans improves transfection efficiency and vector production in transient lentiviral vector manufacturing processes.

Both cell surface and soluble extracellular glycosaminoglycans have been shown to interfere with the exogenous nucleic acid delivery efficiency of non-viral gene delivery, including lipoplex and polyplex-mediated transfection. Most gene therapy viral vectors used commercially and in clinical trials are currently manufactured using transient transfection-based bioprocesses. The growing demand for viral vector products, coupled with a global shortage in production capability, requires improved transfection technologies and processes to maximise process efficiency and productivity. Soluble extracellular glycosaminoglycans were found to accumulate in the conditioned cell culture medium of suspension adapted HEK293T cell cultures, compromising transfection performance and lentiviral vector production. The enzymatic degradation of specific, chondroitin sulphate-based, glycosaminoglycans with chondroitinase ABC was found to significantly enhance transfection performance. Additionally, we report significant improvements in functional lentiviral vector titre when cultivating cells at higher cell densities than those utilised in a control lentiviral vector bioprocess; an improvement that was further enhanced when cultures were supplemented with chondroitinase ABC prior to transfection. A 71.2% increase in functional lentiviral vector titre was calculated when doubling the cell density prior to transfection compared to the existing process and treatment of the high-density cell cultures with 0.1 U/mL chondroitinase ABC resulted in a further 18.6% increase in titre, presenting a method that can effectively enhance transfection performance.

Continuous manufacturing of lentiviral vectors using a stable producer cell line in a fixed-bed bioreactor.

Continuous manufacturing of lentiviral vectors (LVs) using stable producer cell lines could extend production periods, improve batch-to-batch reproducibility, and eliminate costly plasmid DNA and transfection reagents. A continuous process was established by expanding cells constitutively expressing third-generation LVs in the iCELLis Nano fixed-bed bioreactor. Fixed-bed bioreactors provide scalable expansion of adherent cells and enable a straightforward transition from traditional surface-based culture vessels. At 0.5 vessel volume per day (VVD), the short half-life of LVs resulted in a low total infectious titer at 1.36 × 104 TU cm-2. Higher perfusion rates increased titers, peaking at 7.87 × 104 TU cm-2 at 1.5 VVD. The supernatant at 0.5 VVD had a physical-to-infectious particle ratio of 659, whereas this was 166 ± 15 at 1, 1.5, and 2 VVD. Reducing the pH from 7.20 to 6.85 at 1.5 VVD improved the total infectious yield to 9.10 × 104 TU cm-2. Three independent runs at 1.5 VVD and a culture pH of 6.85 showed low batch-to-batch variability, with a coefficient of variation of 6.4% and 10.0% for total infectious and physical LV yield, respectively. This study demonstrated the manufacture of high-quality LV supernatant using a stable producer cell line that does not require induction.

A quality-by-design approach to improve process understanding and optimise the production and quality of CAR-T cells in automated stirred-tank bioreactors.

Ex vivo genetically-modified cellular immunotherapies, such as chimeric antigen receptor T cell (CAR-T) therapies, have generated significant clinical and commercial outcomes due to their unparalleled response rates against relapsed and refractory blood cancers. However, the development and scalable manufacture of these novel therapies remains challenging and further process understanding and optimisation is required to improve product quality and yield. In this study, we employ a quality-by-design (QbD) approach to systematically investigate the impact of critical process parameters (CPPs) during the expansion step on the critical quality attributes (CQAs) of CAR-T cells. Utilising the design of experiments (DOE) methodology, we investigated the impact of multiple CPPs, such as number of activations, culture seeding density, seed train time, and IL-2 concentration, on CAR-T CQAs including, cell yield, viability, metabolism, immunophenotype, T cell differentiation, exhaustion and CAR expression. Initial studies undertaken in G-Rex® 24 multi-well plates demonstrated that the combination of a single activation step and a shorter, 3-day, seed train resulted in significant CAR-T yield and quality improvements, specifically a 3-fold increase in cell yield, a 30% reduction in exhaustion marker expression and more efficient metabolism when compared to a process involving 2 activation steps and a 7-day seed train. Similar findings were observed when the CPPs identified in the G-Rex® multi-well plates studies were translated to a larger-scale automated, controlled stirred-tank bioreactor (Ambr® 250 High Throughput) process. The single activation step and reduced seed train time resulted in a similar, significant improvement in CAR-T CQAs including cell yield, quality and metabolism in the Ambr® 250 High Throughput bioreactor, thereby validating the findings of the small-scale studies and resulting in significant process understanding and improvements. This study provides a methodology for the systematic investigation of CAR-T CPPs and the findings demonstrate the scope and impact of enhanced process understanding for improved CAR-T production.

Quasi-perfusion studies for intensified lentiviral vector production using a continuous stable producer cell line.

Quasi-perfusion culture was employed to intensify lentiviral vector (LV) manufacturing using a continuous stable producer cell line in an 8-day process. Initial studies aimed to identify a scalable seeding density, with 3, 4, and 5 × 104 cells cm-2 providing similar specific productivities of infectious LV. Seeding at 3 × 104 cells cm-2 was selected, and the quasi-perfusion was modulated to minimize inhibitory metabolite accumulation and vector exposure at 37°C. Similar specific productivities of infectious LV and physical LV were achieved at 1, 2, and 3 vessel volumes per day (VVD), with 1 VVD selected to minimize downstream processing volumes. The optimized process was scaled 50-fold to 1,264 cm2 flasks, achieving similar LV titers. However, scaling up beyond this to a 6,320 cm2 multilayer flask reduced titers, possibly from suboptimal gas exchange. Across three independent processes in 25 cm2 to 6,320 cm2 flasks, reproducibility was high with a coefficient of variation of 7.7% ± 2.9% and 11.9% ± 3.0% for infectious and physical LV titers, respectively. The optimized flask process was successfully transferred to the iCELLis Nano (Cytiva) fixed-bed bioreactor, with quasi-perfusion at 1 VVD yielding 1.62 × 108 TU.

Culture of human mesenchymal stem cells on microcarriers in a 5 l stirred-tank bioreactor.

For the first time, fully functional human mesenchymal stem cells (hMSCs) have been cultured at the litre-scale on microcarriers in a stirred-tank 5 l bioreactor, (2.5 l working volume) and were harvested via a potentially scalable detachment protocol that allowed for the successful detachment of hMSCs from the cell-microcarrier suspension. Over 12 days, the dissolved O2 concentration was >45 % of saturation and the pH between 7.2 and 6.7 giving a maximum cell density in the 5 l bioreactor of 1.7 × 10(5) cells/ml; this represents >sixfold expansion of the hMSCs, equivalent to that achievable from 65 fully-confluent T-175 flasks. During this time, the average specific O2 uptake of the cells in the 5 l bioreactor was 8.1 fmol/cell h and, in all cases, the 5 l bioreactors outperformed the equivalent 100 ml spinner-flasks run in parallel with respect to cell yields and growth rates. In addition, yield coefficients, specific growth rates and doubling times were calculated for all systems. Neither the upstream nor downstream bioprocessing unit operations had a discernible effect on cell quality with the harvested cells retaining their immunophenotypic markers, key morphological features and differentiation capacity.

Optimizing and developing a scalable, chemically defined, animal component-free lentiviral vector production process in a fixed-bed bioreactor.

Lentiviral vectors (LVVs) play a critical role in gene delivery for ex vivo gene-modified cell therapies. However, the lack of scalable LVV production methods and the high cost associated with them may limit their use. In this work, we demonstrate the optimization and development of a scalable, chemically defined, animal component-free LVV production process using adherent human embryonic kidney 293T cells in a fixed-bed bioreactor. The initial studies focused on the optimization of the culture process in 2D static cultures. Process changes such as decreasing cell seeding density on day 0 from 2.5 × 104 to 5 × 103 cells/cm2, delaying the transient transfection from 24 to 120 h post-seeding, reducing plasmid DNA to 167 ng/cm2, and adding 5 mM sodium butyrate 6 h post-transfection improved functional LVV titers by 26.9-fold. The optimized animal component-free production process was then transferred to the iCELLis Nano bioreactor, a fixed-bed bioreactor, where titers of 1.2 × 106 TU/cm2 were achieved when it was operated in perfusion. In this work, comparable functional LVV titers were obtained with FreeStyle 293 Expression medium and the conventional Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum both at small and large scale.

Lentiviral Vectors for T Cell Engineering: Clinical Applications, Bioprocessing and Future Perspectives.

Lentiviral vectors have played a critical role in the emergence of gene-modified cell therapies, specifically T cell therapies. Tisagenlecleucel (Kymriah), axicabtagene ciloleucel (Yescarta) and most recently brexucabtagene autoleucel (Tecartus) are examples of T cell therapies which are now commercially available for distribution after successfully obtaining EMA and FDA approval for the treatment of blood cancers. All three therapies rely on retroviral vectors to transduce the therapeutic chimeric antigen receptor (CAR) into T lymphocytes. Although these innovations represent promising new therapeutic avenues, major obstacles remain in making them readily available tools for medical care. This article reviews the biological principles as well as the bioprocessing of lentiviral (LV) vectors and adoptive T cell therapy. Clinical and engineering successes, shortcomings and future opportunities are also discussed. The development of Good Manufacturing Practice (GMP)-compliant instruments, technologies and protocols will play an essential role in the development of LV-engineered T cell therapies.