Abstract:Self-inactivating lentiviral vectors (LVVs) are used regularly for genetic modification of cells, including T cells and hematopoietic stem cells for cellular gene therapy. As vector demand grows, scalable and controllable methods are needed for production. LVVs are typically produced in HEK293T cells in suspension bioreactors using serum-free media or adherent cultures with serum. The iCELLis® is a packed-bed bioreactor for adherent or entrained cells with surface areas from 0.53 to 500 m
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“…Similar titres were produced in Scale-X bioreactors where cell distribution was more homogenous [149]. A side-by-side comparison of LVs from iCellis Nano with LVs manufactured under cGMP using 10-layer cell factories has also demonstrated similar transduction efficiencies [156]. Nonetheless, the singular run of an iCellis Nano in this study was equivalent to 30 triple flasks, demonstrating the impact of scale up options within the upstream.…”
Lentiviral vectors (LVs) are potent tools for the delivery of genes of interest into mammalian cells and are now commonly utilised within the growing field of cell and gene therapy for the treatment of monogenic diseases and adoptive therapies such as chimeric antigen T-cell (CAR-T) therapy. This is a comprehensive review of the individual bioprocess operations employed in LV production. We highlight the role of envelope proteins in vector design as well as their impact on the bioprocessing of lentiviral vectors. An overview of the current state of these operations provides opportunities for bioprocess discovery and improvement with emphasis on the considerations for optimal and scalable processing of LV during development and clinical production. Upstream culture for LV generation is described with comparisons on the different transfection methods and various bioreactors for suspension and adherent producer cell cultivation. The purification of LV is examined, evaluating different sequences of downstream process operations for both small- and large-scale production requirements. For scalable operations, a key focus is the development in chromatographic purification in addition to an in-depth examination of the application of tangential flow filtration. A summary of vector quantification and characterisation assays is also presented. Finally, the assessment of the whole bioprocess for LV production is discussed to benefit from the broader understanding of potential interactions of the different process options. This review is aimed to assist in the achievement of high quality, high concentration lentiviral vectors from robust and scalable processes.
“…Similar titres were produced in Scale-X bioreactors where cell distribution was more homogenous [149]. A side-by-side comparison of LVs from iCellis Nano with LVs manufactured under cGMP using 10-layer cell factories has also demonstrated similar transduction efficiencies [156]. Nonetheless, the singular run of an iCellis Nano in this study was equivalent to 30 triple flasks, demonstrating the impact of scale up options within the upstream.…”
Lentiviral vectors (LVs) are potent tools for the delivery of genes of interest into mammalian cells and are now commonly utilised within the growing field of cell and gene therapy for the treatment of monogenic diseases and adoptive therapies such as chimeric antigen T-cell (CAR-T) therapy. This is a comprehensive review of the individual bioprocess operations employed in LV production. We highlight the role of envelope proteins in vector design as well as their impact on the bioprocessing of lentiviral vectors. An overview of the current state of these operations provides opportunities for bioprocess discovery and improvement with emphasis on the considerations for optimal and scalable processing of LV during development and clinical production. Upstream culture for LV generation is described with comparisons on the different transfection methods and various bioreactors for suspension and adherent producer cell cultivation. The purification of LV is examined, evaluating different sequences of downstream process operations for both small- and large-scale production requirements. For scalable operations, a key focus is the development in chromatographic purification in addition to an in-depth examination of the application of tangential flow filtration. A summary of vector quantification and characterisation assays is also presented. Finally, the assessment of the whole bioprocess for LV production is discussed to benefit from the broader understanding of potential interactions of the different process options. This review is aimed to assist in the achievement of high quality, high concentration lentiviral vectors from robust and scalable processes.
“…The development of stable producer cell lines for lentivectors pseudotyped with VSV-G is challenging, owing to the cytotoxicity associated with this envelope, which is not the case with other vector envelopes. While several lentiviral packaging cell lines have been described, none is commercially available-an unmet need in the vector production space (98)(99)(100)(101).…”
As of April 2021, there are five commercially available chimeric antigen receptor (CAR) T cell therapies for hematologic malignancies. With the current transition of CAR T cell manufacturing from academia to industry, there is a shift toward Good Manufacturing Practice (GMP)-compliant closed and automated systems to ensure reproducibility and to meet the increased demand for patients with cancer. In this review, we describe current CAR T cell clinical manufacturing models and discuss emerging technologic advances that embrace scaling and production optimization. We summarize measures being used to shorten CAR T cell manufacturing times and highlight regulatory challenges to scaling production for clinical use.
Significance:As the demand for CAR T cell cancer therapy increases, several closed and automated production platforms are being deployed, and others are in development. This review provides a critical appraisal of these technologies, which can be leveraged to scale and optimize the production of nextgeneration CAR T cells.
iNtRODUctiONChimeric antigen receptor (CAR)-modified T cells have emerged as an efficacious treatment for patients with certain hematologic malignancies (1). Currently, five CAR T cell products are approved for commercial use and available on the U.S. market: three for B-cell leukemia and lymphoma (tisagenlecleucel, axicabtagene ciloleucel, lisocabtagene maraleucel), one for mantle cell lymphoma (brexucabtagene autoleucel), and one for multiple myeloma (idecabtagene vicleucel; refs. 2-8). These therapies involve genetically modifying patient-derived (autologous) peripheral blood T cells to express a CAR directed against antigens present on the surface of targeted tumor cells, such as the CD19 molecule, or, in the case of idecabtagene vicleucel, B-cell maturation antigen (BCMA;. After antigen recognition, the intracellular signaling domains activate the immune effector and memory functions of the CAR T cells. Once activated, these T cells proliferate, infiltrate tumor sites, secrete cytokines, and release cytolytic granules to eliminate targeted cells in an antigen-dependent manner (1). All approved CAR T cell products are second-generation CARs that incorporate CD28 or CD137 (4-1BB) costimulatory signals, which are essential for eliciting a clinically relevant immune response (9-15). These CAR T cells were able to elicit complete responses (CR) in 32% to 67% of patients with lymphoma and showed better CR rates in patients with leukemia (16)(17)(18)(19).The increasing success of CAR T immunotherapies in relapsed/refractory hematologic malignancies sparked the interest of pharmaceutical companies, and several products targeting a variety of cancers are currently in the pipeline (20). However, many limitations to current CAR T cell manufacturing must be overcome before this modality can be fully integrated into routine clinical practice. First, most CAR T cell trials to date have used autologous peripheral blood and apheresis as the main cell sources for manufacturing
“…It should be acknowledged that other monitored online parameters, such as air and oxygen gas flow rates, also correlated with an increase in PTI and MRI during these initial baseline monitoring experiments. However, pH was selected as the key parameter of interest to test the Ranger RI systems ability to adapt bioprocessing conditions to maximise the activity of the cell culture, since the utilisation of lower pH set-points (pH 6.00–6.80) has been recently reported to increase LVV production compared to neutral conditions 32 – 34 . Figure 2 Unoptimised HEK293T-based PCL HIV-1-GFP LVV production bioprocess involving the passive monitoring of ( a ) PTI ( b ) MRI and ( c ) pH to gain baseline monitoring data.…”
Process analytical technology (PAT) has demonstrated huge potential to enable the development of improved biopharmaceutical manufacturing processes by ensuring the reliable provision of quality products. However, the complexities associated with the manufacture of advanced therapy medicinal products have resulted in a slow adoption of PAT tools into industrial bioprocessing operations, particularly in the manufacture of cell and gene therapy products. Here we describe the applicability of a novel refractometry-based PAT system (Ranger system), which was used to monitor the metabolic activity of HEK293T cell cultures during lentiviral vector (LVV) production processes in real time. The PAT system was able to rapidly identify a relationship between bioreactor pH and culture metabolic activity and this was used to devise a pH operating strategy that resulted in a 1.8-fold increase in metabolic activity compared to an unoptimised bioprocess in a minimal number of bioreactor experiments; this was achieved using both pre-programmed and autonomous pH control strategies. The increased metabolic activity of the cultures, achieved via the implementation of the PAT technology, was not associated with increased LVV production. We employed a metabolic modelling strategy to elucidate the relationship between these bioprocess level events and HEK293T cell metabolism. The modelling showed that culturing of HEK293T cells in a low pH (pH 6.40) environment directly impacted the intracellular maintenance of pH and the intracellular availability of oxygen. We provide evidence that the elevated metabolic activity was a response to cope with the stress associated with low pH to maintain the favourable intracellular conditions, rather than being indicative of a superior active state of the HEK293T cell culture resulting in enhanced LVV production. Forecasting strategies were used to construct data models which identified that the novel PAT system not only had a direct relationship with process pH but also with oxygen availability; the interaction and interdependencies between these two parameters had a direct effect on the responses observed at the bioprocess level. We present data which indicate that process control and intervention using this novel refractometry-based PAT system has the potential to facilitate the fine tuning and rapid optimisation of the production environment and enable adaptive process control for enhanced process performance and robustness.
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