Accelerating IND-enabling toxicology studies using protein products from stable pools or pools of clones in Chinese hamster ovary cells

In recent years, accelerating Chemistry, Manufacturing, and Controls (CMC) workflows for clinical entry has become a critical focus in biologics development. Advances in the development of cell lines, cell culture processes, and analytical technologies have enabled the generation of more homogeneous stable pool populations with increased productivity. Leveraging the experience gained from the COVID-19 product development, the strategic use of stable cell pools or a pool of clones for early-stage non-GMP material generation and process development has proven transformative in significantly reducing the CMC timeline to investigational new drug (IND). This study provides a comprehensive comparison of bioprocess performance and product quality attributes of materials produced from stable pools or a pool of clones (toxicology study materials) versus those from clonally derived cells (GMP clinical batches) across six First-in-Human (FIH) programs involving mAbs, bsAb, and Fc-fusion proteins. The results demonstrate a strong alignment and the feasibility of using protein materials from stable pools or a pool of clones in toxicology studies. In conclusion, utilizing non-clonal CHO cell-derived material for preclinical studies offers a strategic approach that can be broadly applied to complex molecules across various disease areas, even under standard regulatory filings, accelerating the path to clinical trials.

Utilizing non-clonal CHO cell derived materials for preclinical studies of complex molecules

BACKGROUND

The use of non-clonal CHO cell derived materials for preclinical studies has been found to be a valuable approach to accelerate the development of monoclonal antibodies (mAbs) for first-in-human (FIH) studies. In a comprehensive study, we assessed the culture performance, productivity, and product quality of non-clonal cell lines compared with clonal cell lines expressing various biologic modalities to determine if this approach can be applied to complex molecules.

RESULTS

We evaluated a multi-specific antibody, a cytokine-Fc fusion protein, and a mAb produced using the stable pool, the pool of top clones, and the lead clone utilizing transposase-mediated integration. The results indicated that the attributes were comparable regardless of the source of cells. Building upon these findings, the study progressed to the preclinical manufacturing of two multi-specific antibodies using both the pool of top clones and the lead clone. Subsequently, clinical manufacturing of these multi-specific antibodies was performed using the lead clone. The batches produced with the pool of clones and the lead clone demonstrated a high level of comparability in culture performance, productivity, and product quality.

CONCLUSIONS

In conclusion, non-clonal CHO cell derived materials can be effectively utilized for preclinical studies of complex molecules without compromising their quality, allowing for accelerated development for FIH studies.

The new frontier in CHO cell line development: From random to targeted transgene integration technologies

Cell line development represents a crucial step in the development process of a therapeutic glycoprotein. Chinese hamster ovary (CHO) cells are the most frequently employed mammalian host cell system for the industrial manufacturing of biologics. The predominant application of CHO cells for heterologous recombinant protein expression lies in the relative simplicity of stably introducing ectopic DNA into the CHO host cell genome. Since CHO cells were first used as expression host for the industrial production of biologics in the late 1980s, stable genomic transgene integration has been achieved almost exclusively by random integration. Since then, random transgene integration had become the gold standard for generating stable CHO production cell lines due to a lack of viable alternatives. However, it was eventually demonstrated that this approach poses significant challenges on the cell line development process such as an increased risk of inducing cell line instability. In recent years, significant discoveries of new and highly potent (semi)-targeted transgene integration systems have paved the way for a technological revolution in the cell line development sector. These advanced methodologies comprise the application of transposase-, recombinase- or Cas9 nuclease-mediated site-specific genomic integration techniques, which enable a scarless transfer of the transgene expression cassette into transcriptionally active loci within the host cell genome. This review summarizes recent advancements in the field of transgene integration technologies for CHO cell line development and compare them to the established random integration approach. Moreover, advantages and limitations of (semi)-targeted integration techniques are discussed, and benefits and opportunities for the biopharmaceutical industry are outlined.

SiMPl-GS: Advancing Cell Line Development via Synthetic Selection Marker for Next-Generation Biopharmaceutical Production

Rapid and efficient cell line development (CLD) process is essential to expedite therapeutic protein development. However, the performance of widely used glutamine-based selection systems is limited by low selection efficiency, stringency, and the inability to select multiple genes. Therefore, an AND-gate synthetic selection system is rationally designed using split intein-mediated protein ligation of glutamine synthetase (GS) (SiMPl-GS). Split sites of the GS are selected using a computational approach and validated with GS-knockout Chinese hamster ovary cells for their potential to enable cell survival in a glutamine-free medium. In CLD, SiMPl-GS outperforms the wild-type GS by selectively enriching high producers. Unlike wild-type GS, SiMPl-GS results in cell pools in which most cells produce high levels of therapeutic proteins. Harnessing orthogonal split intein pairs further enables the selection of four plasmids with a single selection, streamlining multispecific antibody-producing CLD. Taken together, SiMPl-GS is a simple yet effective means to expedite CLD for therapeutic protein production.

Rapid and Scalable Production of Functional SARS-CoV-2 Virus-like Particles (VLPs) by a Stable HEK293 Cell Pool

At times of pandemics, such as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the situation demands rapid development and production timelines of safe and effective vaccines for delivering life-saving medications quickly to patients. Typical biologics production relies on using the lengthy and arduous approach of stable single-cell clones. Here, we used an alternative approach, a stable cell pool that takes only weeks to generate compared to a stable single-cell clone that needs several months to complete. We employed the membrane, envelope, and highly immunogenic spike proteins of SARS-CoV-2 to produce virus-like particles (VLPs) using the HEK293-F cell line as a host system with an economical transfection reagent. The cell pool showed the stability of protein expression for more than one month. We demonstrated that the production of SARS-CoV-2 VLPs using this cell pool was scalable up to a stirred-tank 2 L bioreactor in fed-batch mode. The purified VLPs were properly assembled, and their size was consistent with the authentic virus. Our particles were functional as they specifically entered the cell that naturally expresses ACE-2. Notably, this work reports a practical and cost-effective manufacturing platform for scalable SARS-CoV-2 VLPs production and chromatographic purification.

Further accelerating biologics development from DNA to IND: the journey from COVID-19 to non-COVID-19 programs

The Coronavirus Disease (COVID-19) pandemic has spurred adoption of revolutionary initiatives by regulatory agencies and pharmaceutical industry worldwide to deliver therapeutic COVID-19 antibodies to patients at unprecedented speed. Among these, timeline of chemistry, manufacturing and control (CMC), which involves process development and manufacturing activities critical for the assurance of product quality and consistency before first-in-human clinical trials, was greatly reduced from typically 12-15 months (using clonal materials) to approximately 3 months (using non-clonal materials) in multiple cases. In this perspective, we briefly review the acceleration approaches published for therapeutic COVID-19 antibodies and subsequently discuss the applicability of these approaches to achieve investigational new drug (IND) timelines of ≤10 months in over 60 COVID-19 and non-COVID-19 programs performed at WuXi Biologics. We are of the view that, with demonstrated product quality and consistency, innovative approaches used for COVID-19 can be widely applied in all disease areas for greater speed to clinic.

Recombinant CHO Cell Pool Generation Using PiggyBac Transposon System

CHO cell pools with desirable characteristics of high titer and consistent product quality are useful for rapid production of recombinant proteins. Here, we describe the generation of CHO cell pools using the piggyBac transposon system for mediating gene integration. The method describes the co-transfection of cells with the donor plasmid (coding for the gene of interest) and the helper plasmid (coding for the transposase) using polyethyleneimine (PEI). This is followed by a genetic selection for the generation of a cell pool. The resulting cell pool can be used to start a batch or fed-batch culture. Alternatively, it can be used for generation of clonal cell lines or generation of cell banks for future use.

Utilizing targeted integration CHO pools to potentially accelerate the GMP manufacturing of monoclonal and bispecific antibodies

Monoclonal antibodies (mAbs) are effective therapeutic agents against many acute infectious diseases including COVID-19, Ebola, RSV, Clostridium difficile, and Anthrax. mAbs can therefore help combat a future pandemic. Unfortunately, mAb development typically takes years, limiting its potential to save lives during a pandemic. Therefore "pandemic mAb" timelines need to be shortened. One acceleration tool is "deferred cloning" and leverages new Chinese hamster ovary (CHO) technology based on targeted gene integration (TI). CHO pools, instead of CHO clones, can be used for Phase I/II clinical material production. A final CHO clone (producing the mAb with a similar product quality profile and preferably with a higher titer) can then be used for Phase III trials and commercial manufacturing. This substitution reduces timelines by ~3 months. We evaluated our novel CHO TI platform to enable deferred cloning. We created four unique CHO pools expressing three unique mAbs (mAb1, mAb2, and mAb3), and a bispecific mAb (BsAb1). We then performed single-cell cloning for mAb1 and mAb2, identifying three high-expressing clones from each pool. CHO pools and clones were inoculated side-by-side in ambr15 bioreactors. CHO pools yielded mAb titers as high as 10.4 g/L (mAb3) and 7.1 g/L (BsAb1). Subcloning yielded CHO clones expressing higher titers relative to the CHO pools while yielding similar product quality profiles. Finally, we showed that CHO TI pools were stable by performing a 3-month cell aging study. In summary, our CHO TI platform can increase the speed to clinic for a future "pandemic mAb."

Recombinant Protein Production from Stable CHO Cell Pools

The continuous improvement of expression platforms is necessary to respond to the increasing demand for recombinant proteins that are required to carry out structural or functional studies as well as for their characterization as biotherapeutics. While transient gene expression (TGE) in mammalian cells constitutes a rapid and well-established approach, non-clonal stably transfected cells, or "pools," represent another option, which is especially attractive when recurring productions of the same protein are required. From a culture volume of just a few liters, stable pools can provide hundreds of milligrams to gram quantities of high-quality secreted recombinant proteins.In this chapter, we describe a highly efficient and cost-effective procedure for the generation of Chinese Hamster Ovary cell stable pools expressing secreted recombinant proteins using commercially available serum-free media and polyethylenimine (PEI) as the transfection reagent. As a specific example of how this protocol can be applied, the production and downstream purification of recombinant His-tagged trimeric SARS-CoV-2 spike protein ectodomain (SmT1) are described.

A CHO stable pool production platform for rapid clinical development of trimeric SARS-CoV-2 spike subunit vaccine antigens

Protein expression from stably transfected Chinese hamster ovary (CHO) clones is an established but time-consuming method for manufacturing therapeutic recombinant proteins. The use of faster, alternative approaches, such as non-clonal stable pools, has been restricted due to lower productivity and longstanding regulatory guidelines. Recently, the performance of stable pools has improved dramatically, making them a viable option for quickly producing drug substance for GLP-toxicology and early-phase clinical trials in scenarios such as pandemics that demand rapid production timelines. Compared to stable CHO clones which can take several months to generate and characterize, stable pool development can be completed in only a few weeks. Here, we compared the productivity and product quality of trimeric SARS-CoV-2 spike protein ectodomains produced from stable CHO pools or clones. Using a set of biophysical and biochemical assays we show that product quality is very similar and that CHO pools demonstrate sufficient productivity to generate vaccine candidates for early clinical trials. Based on these data, we propose that regulatory guidelines should be updated to permit production of early clinical trial material from CHO pools to enable more rapid and cost-effective clinical evaluation of potentially life-saving vaccines.

Accelerating the speed of innovative anti-tumor drugs to first-in-human trials incorporating key de-risk strategies

Pharmaceutical companies have recently focused on accelerating the timeline for initiating first-in-human (FIH) trials to allow quick assessment of biologic drugs. For example, a stable cell pool can be used to produce materials for the toxicology (Tox) study, reducing time to the clinic by 4-5 months. During the coronavirus disease 2019 (COVID-19) pandemic, the anti-COVID drugs timeline from DNA transfection to the clinical stage was decreased to 6 months using a stable pool to generate a clinical drug substrate (DS) with limited stability, virus clearance, and Tox study package. However, a lean chemistry, manufacturing, and controls (CMC) package raises safety and comparability risks and may leave extra work in the late-stage development and commercialization phase. In addition, whether these accelerated COVID-19 drug development strategies can be applied to non-COVID projects and established as a standard practice in biologics development is uncertain. Here, we present a case study of a novel anti-tumor drug in which application of "fast-to-FIH" approaches in combination with BeiGene's de-risk strategy achieved successful delivery of a complete CMC package within 10 months. A comprehensive comparability study demonstrated that the DS generated from a stable pool and a single-cell-derived master cell bank were highly comparable with regards to process performance, product quality, and potency. This accomplishment can be a blueprint for non-COVID drug programs that approach the pace of drug development during the pandemic, with no adverse impact on the safety, quality, and late-stage development of biologics.

Rapidly accelerated development of neutralizing COVID-19 antibodies by reducing cell line and CMC development timelines

Since the Coronavirus Disease 2019 (COVID-19) outbreak, unconventional cell line development (CLD) strategies have been taken to enable development of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-neutralizing antibodies at expedited speed. We previously reported a novel chemistry, manufacturing, and control (CMC) workflow and demonstrated a much-shortened timeline of 3-6 months from DNA to investigational new drug (IND) application. Hereafter, we have incorporated this CMC strategy for many SARS-CoV-2-neutralizing antibody programs at WuXi Biologics. In this paper, we summarize the accelerated development of a total of seven antibody programs, some of which have received emergency use authorization  approval in less than 2 years. Stable pools generated under good manufacturing practice (GMP) conditions consistently exhibited similar productivity and product quality at different scales and batches, enabling rapid initiation of phase I clinical trials. Clones with comparable product quality as parental pools were subsequently screened and selected for late-stage development and manufacturing. Moreover, a preliminary stability study plan was devised to greatly reduce the time required for final clone determination and next-generation sequencing-based viral testing was implemented to support rapid conditional release of the master cell bank for GMP production. The successful execution of these COVID-19 programs relies on our robust, fit for purpose, and continuously improving CLD platform. The speed achieved for pandemic-related biologics development may innovate typical biologics development timelines and become a new standard in the industry.

Monoclonal antibody therapies for COVID-19: lessons learned and implications for the development of future products

Several companies were authorized to treat COVID-19 patients with monoclonal antibodies within 1-2 years of the start of the pandemic. These products were discovered, developed, manufactured, clinically tested, and approved under emergency-use authorization at unprecedented speed. Pandemic urgency led to novel development approaches that reduced the time to clinical trials by 75% or more without creating unacceptable patient or product-safety risks. Hundreds of thousands of patients now benefit from these therapeutics that have reduced the rates of hospitalization and death. The chemistry, manufacturing, and control development strategies set a new precedent of speed, safety, and demonstrated clinical benefit and will likely have a lasting impact on the development of future monoclonal antibody therapies for not only infectious diseases but also for oncology, inflammation, and rare diseases.

Towards maximum acceleration of monoclonal antibody development: Leveraging transposase-mediated cell line generation to enable GMP manufacturing within 3 months using a stable pool

In recent years, acceleration of development timelines has become a major focus within the biopharmaceutical industry to bring innovative therapies faster to patients. However, in order to address a high unmet medical need even faster further acceleration potential has to be identified to transform "speed-to-clinic" concepts into "warp-speed" development programs. Recombinant Chinese hamster ovary (CHO) cell lines are the predominant expression system for monoclonal antibodies (mAbs) and are routinely generated by random transgene integration (RTI) of the genetic information into the host cell genome. This process, however, exhibits considerable challenges such as the requirement for a time-consuming clone screening process to identify a suitable clonally derived manufacturing cell line. Hence, RTI represents an error prone and tedious method leading to long development timelines until availability of Good Manufacturing Practice (GMP)-grade drug substance (DS). Transposase-mediated semi-targeted transgene integration (STI) has been recently identified as a promising alternative to RTI as it allows for a more rapid generation of high-performing and stable production cell lines. In this report, we demonstrate how a STI technology was leveraged to develop a very robust DS manufacturing process based on a stable pool cell line at unprecedented pace. Application of the novel strategy resulted in the manufacturing of GMP-grade DS at 2,000 L scale in less than three months paving the way for a start of Phase I clinical trials only six months after transfection. Finally, using a clonally derived production cell line, which was established from the parental stable pool, we were able to successfully implement a process with an increased mAb titer of up to 5 g per liter at the envisioned commercial scale (12,000 L) within eight months.

Mitochondrial membrane potential-enriched CHO host: a novel and powerful tool for improving biomanufacturing capability

With the aim of increasing protein productivity of Chinese hamster ovary (CHO) cells, we sought to generate new CHO hosts with favorable biomanufacturing phenotypes and improved functionality. Here, we present an innovative approach of enriching the CHO host cells with a high mitochondrial membrane potential (MMP). Stable transfectant pools and clonal cell lines expressing difficult-to-express bispecific molecules generated from the MMP-enriched host outperformed the parental host by displaying (1) improved fed-batch productivity; (2) enhanced long-term cell viability of pools; (3) more favorable lactate metabolism; and (4) improved cell cloning efficiency during monoclonal cell line generation. Proteomic analysis together with Western blot validation were used to investigate the underlying mechanisms by which high MMP influenced production performance. The MMP-enriched host exhibited multifaceted protection against mitochondrial dysfunction and endoplasmic reticulum stress. Our findings indicate that the MMP-enriched host achieved an overall “fitter” phenotype that contributes to the significant improvement in biomanufacturing capability.

Upstream cell culture process characterization and in-process control strategy development at pandemic speed

As of early 2022, the coronavirus disease 2019 (COVID-19) pandemic remains a substantial global health concern. Different treatments for COVID-19, such as anti-COVID-19 neutralizing monoclonal antibodies (mAbs), have been developed under tight timelines. Not only mAb product and clinical development but also chemistry, manufacturing, and controls (CMC) process development at pandemic speed are required to address this highly unmet patient need. CMC development consists of early- and late-stage process development to ensure sufficient mAb manufacturing yield and consistent product quality for patient safety and efficacy. Here, we report a case study of late-stage cell culture process development at pandemic speed for mAb1 and mAb2 production as a combination therapy for a highly unmet patient treatment. We completed late-stage cell culture process characterization (PC) within approximately 4 months from the cell culture process definition to the initiation of the manufacturing process performance qualification (PPQ) campaign for mAb1 and mAb2, in comparison to a standard one-year PC timeline. Different strategies were presented in detail at different PC steps, i.e., pre-PC risk assessment, scale-down model development and qualification, formal PC experiments, and in-process control strategy development for a successful PPQ campaign that did not sacrifice quality. The strategies we present may be applied to accelerate late-stage process development for other biologics to reduce timelines.

Rapid cGMP manufacturing of COVID-19 monoclonal antibody using stable CHO cell pools

Therapeutic proteins, including monoclonal antibodies, are typically manufactured using clonally derived, stable host cell lines, since consistent and predictable cell culture performance is highly desirable. However, selecting and preparing banks of stable clones takes considerable time, which inevitably extends overall development timelines for new therapeutics by delaying the start of subsequent activities, such as the scale-up of manufacturing processes. In the context of the coronavirus disease 2019 (COVID-19) pandemic, with its intense pressure for accelerated development strategies, we used a novel transposon-based Leap-In Transposase® system to rapidly generate high-titer stable pools and then used them directly for large scale-manufacturing of an anti-severe acute respiratory syndrome coronavirus 2 monoclonal antibody under cGMP. We performed the safety testing of our non-clonal cell bank, then used it to produce material at a 200L-scale for preclinical safety studies and formulation development work, and thereafter at 2000L scale for supply of material for a Phase 1 clinical trial. Testing demonstrated the comparability of critical product qualities between the two scales and, more importantly, that our final clinical trial product met all pre-set product quality specifications. The above expediated approach provided clinical trial material within 4.5 months, in comparison to 12-14 months for production of clinical trial material via the conventional approach.

Microfluidic chip-based single-cell cloning to accelerate biologic production timelines

Cell line development (CLD) represents a critical, yet time‐consuming, step in the biomanufacturing process as significant resources are devoted to the scale‐up and screening of several hundreds to thousands of single‐cell clones. Typically, transfected pools are fully recovered from selection and characterized for growth, productivity, and product quality to identify the best pools suitable for single‐cell cloning (SCC) using limiting dilution or fluorescence‐activated cell sorting (FACS). Here we report the application of the Berkeley Lights Beacon Instrument (BLI) in an early SCC process to accelerate the CLD timeline. Transfected pools were single‐cell cloned when viabilities reached greater than 85% or during selection when viabilities were less than 30%. Clones isolated from these accelerated processes exhibited comparable growth, productivity, and product quality to those derived from a standard CLD process and fit into an existing manufacturing platform. With these approaches, up to a 30% reduction in the overall CLD timeline was achieved. Furthermore, early process‐derived clones demonstrated equivalent long‐term stability compared with standard process‐derived clones over 50 population doubling levels (PDLs). Taken together, the data supported early SCC on the BLI as an attractive approach to reducing the standard CLD timeline while still identifying clones with acceptable manufacturability.

Reshaping cell line development and CMC strategy for fast responses to pandemic outbreak

The global pandemic outbreak COVID-19 (SARS-COV-2), has prompted many pharmaceutical companies to develop vaccines and therapeutic biologics for its prevention and treatment. Most of the therapeutic biologics are common human IgG antibodies, which were identified by next-generation sequencing (NGS) with the B cells from the convalescent patients. To fight against pandemic outbreaks like COVID-19, biologics development strategies need to be optimized to speed up the timeline. Since the advent of therapeutic biologics, strategies of transfection and cell line selection have been continuously improved for greater productivity and efficiency. NGS has also been implemented for accelerated cell bank testing. These recent advances enable us to rethink and reshape the chemistry, manufacturing, and controls (CMC) strategy in order to start supplying Good Manufacturing Practices (GMP) materials for clinical trials as soon as possible. We elucidated an accelerated CMC workflow for biologics, including using GMP-compliant pool materials for phase I clinical trials, selecting the final clone with product quality similar to that of phase I materials for late-stage development and commercial production.

Developing therapeutic monoclonal antibodies at pandemic pace

The time from discovery to proof-of-concept trials could be reduced to 5–6 months from a traditional timeline of 10–12 months.

[Biomanufacturing of monoclonal antibodies]

Antibody-based drugs are an increasingly important part of the therapeutic arsenal against a wide variety of medical conditions. As the number of commercial products and pipeline candidates grows, a crucial issue facing the industry is the current and future state of biomanufacturing. The productivity of the protein expression platforms, along with the performance of the technologies impacting upstream and downstream bioprocessing, are critical factors affecting the cost and time of therapeutic antibody development and commercialization. Cell engineering strategies are being used to improve the production of antibodies and to better control their quality in terms of posttranslational modifications, in particular with regards to their glycosylation state, as this can influence their therapeutic activity. Additionally, the advance of "omics" technologies have recently given rise to new possibilities in improving these expression platforms. We review here the various advances in biomanufacturing essential to the continued growth of the therapeutic antibody market.

Enabling speed to clinic for monoclonal antibody programs using a pool of clones for IND-enabling toxicity studies

The importance of speed to clinic for medicines that may address unmet medical needs puts pressure on product development timelines. Historically, both toxicology and first-in-human clinical materials are generated using the same clonal-derived cells to ensure safety and minimize any development risks. However, cell line development with single cell cloning is time consuming, and aggravated by the time needed to screen for a lead clone based on cell line stability and manufacturability. In order to achieve faster timelines, we have used pools of up to six clones for earlier production of drug substance for regulatory filing-enabling toxicology studies, and then the final single clone was selected for production of clinical materials. This approach was enabled by using platform processes across all stages of early development, including expression vectors, host cell lines, media, and production processes. Through comprehensive cell culture and product quality analysis, we demonstrated that the toxicology material was representative of the clinical material for all six monoclonal antibody programs evaluated. Our extensive development experience further confirmed that using a pool of clones for toxicology material generation is a reliable approach to shorten the early development timeline.

Process intensification in fed-batch production bioreactors using non-perfusion seed cultures

Although process intensification by continuous operation has been successfully applied in the chemical industry, the biopharmaceutical industry primarily uses fed-batch, rather than continuous or perfusion methods, to produce stable monoclonal antibodies (mAbs) from Chinese hamster ovary (CHO) cells. Conventional fed-batch bioreactors may start with an inoculation viable cell density (VCD) of ~0.5 × 106 cells/mL. Increasing the inoculation VCD in the fed-batch production bioreactor (referred to as N stage bioreactor) to 2-10 × 106 cells/mL by introducing perfusion operation or process intensification at the seed step (N-1 step) prior to the production bioreactor has recently been used because it increases manufacturing output by shortening cell culture production duration. In this study, we report that increasing the inoculation VCD significantly improved the final titer in fed-batch production within the same 14-day duration for 3 mAbs produced by 3 CHO GS cell lines. We also report that other non-perfusion methods at the N-1 step using either fed batch or batch mode with enriched culture medium can similarly achieve high N-1 final VCD of 22-34 × 106 cells/mL. These non-perfusion N-1 seeds supported inoculation of subsequent production fed-batch production bioreactors at increased inoculation VCD of 3-6 × 106 cells/mL, where these achieved titer and product quality attributes comparable to those inoculated using the perfusion N-1 seeds demonstrated in both 5-L bioreactors, as well as scaled up to 500-L and 1000-L N-stage bioreactors. To operate the N-1 step using batch mode, enrichment of the basal medium was critical at both the N-1 and subsequent intensified fed-batch production steps. The non-perfusion N-1 methodologies reported here are much simpler alternatives in operation for process development, process characterization, and large-scale commercial manufacturing compared to perfusion N-1 seeds that require perfusion equipment, as well as preparation and storage vessels to accommodate large volumes of perfusion media. Although only 3 stable mAbs produced by CHO cell cultures are used in this study, the basic principles of the non-perfusion N-1 seed strategies for shortening seed train and production culture duration or improving titer should be applicable to other protein production by different mammalian cells and other hosts at any scale biologics facilities.

Recombinant CHO Cell Pool Generation Using piggyBac Transposon System

CHO cell pools with desirable characteristics of high titer and consistent product quality are useful for rapid production of recombinant proteins. Here we describe the generation of CHO cell pools using the piggyBac transposon system for mediating gene integration. The method describes the co-transfection of cells with the donor plasmid (coding for the gene of interest) and the helper plasmid (coding for the transposase) using polyethyleneimine (PEI). This is followed by a genetic selection for the generation of a cell pool. The resulting cell pool can be used to start a batch or fed-batch culture. Alternatively it can be used for generation of clonal cell lines or generation of cell banks for future use.