Experts from WuXi Biologics explain how next-generation cell line development with targeted integration advances the field by enabling the production of clonal cell lines with predictable transgene copies at specific, predefined sites in the host genome.
Chinese hamster ovary (CHO) cells are the backbone of biopharma. Used primarily for manufacturing monoclonal antibodies (mAbs) and other recombinant protein therapeutics,1 they account for around 90 percent of mammalian-produced therapeutic proteins on the market. More recently, novel CHO cell-derived subunit vaccines have also exemplified their utility in vaccine antigen production.1
The popularity of CHO cells is due to their unique properties and adaptability, including the ability to grow in suspension cultures – allowing for scalability and manipulation within bioreactors – and their remarkable robustness and genetic stability.
Additionally, CHO cells can produce proteins with human-like characteristics, such as glycosylation profiles, which is crucial for protein efficacy and stability. These cells can also perform complex human protein-like post-translational modifications (PTMs).
Producing the desired proteins requires inserting into the host genome an ‘expression cassette’ comprising a promoter, the gene of interest and a terminator. Conventionally, this process relied on the random insertion of expression vectors, followed by labour-intensive screening for suitable cells from a recombinant cell pool.2 Efforts to improve insertion accuracy have led to the development of semi-controlled integration techniques – the benefits of which include stable cell pools with greater homogeneity. However, they still can lack full insertion control.
With advancements in genome editing and availability of the CHO genome, targeted integration...[is considered the gold standard however the TI CLD platform] significantly accelerating development timelines while maintaining quality standards"
With advancements in genome editing and availability of the CHO genome, targeted integration (TI) emerged as the first technology to allow precise, controlled transgene insertion. TI delivers recombinant cell lines with predictable transgene copies and genome location, more predictable productivity and assured cell line stability. Considered the gold standard, it offers next-generation cell line development (CLD) for faster, more stable and consistent cell lines.
Here, we introduce WuXi Biologics’ new TI cell line platform and explain how it enables the rapid production of cell lines with predictable transgene copies at specific, predefined locations.
Novel targeted integration platform
Identification of suitable TI host cells involves screening for cell growth, metabolic profiles, titre performance and product quality attributes. Crucially, the cell line must harbour a landing pad capable of efficient recombinase-mediated cassette exchange.
Using this approach, WuXi Biologics established a robust CHO cell line based on its proprietary WuXiaTM cell line platform. In its fourth generation, known as WuXia TrueSite,3 the platform enables new TI host cell lines to achieve pool titres around 6.0 g/L and lead clone productivity around 8.0 g/L under fed-batch processes for mAb molecules (Figure 1), fusion proteins and symmetric/asymmetric antibodies. Process optimisation can increase the titre to over 10.0 g/L via intensification or changing the temperature (data not shown).
Figure 1: Top clone titre distributions of mAb molecules in pool and clonal cell lines
generated by the new proprietary TI CLD platform WuXia TrueSite.[/caption]
Product stability
Conventional random integration cell lines often face challenges with productivity decline during cell banking and scale-up. In contrast, TI cell lines are so stable that they can eliminate the need for cell line stability studies from the critical path, directly accelerating development timelines. Further downstream, their stability supports use for large-scale production – up to around 20,000L.
The expression stability of WuXia TrueSite clones has been demonstrated over 60 population doubling levels (PDLs) in fed-batch cultures of three mAbs and one asymmetric antibody (Figure 2). In the absence of selection pressures, the cell lines demonstrated robust genetic and quality stability, with over 99 percent remaining stable and titres being reduced by less than 20 percent.
Figure 2: Titre variation distributions between PDL0 and PDL60 (n=48),
showing good stability of pool and clonal cell lines derived from WuXia TrueSite.[/caption]
Product quality consistency
Consistent product quality is necessary for the reliability, safety and efficacy of biopharmaceuticals, and for reducing the risk of product failure downstream. It also enables more efficient R&D, reducing the time and resources required to develop and commercialise new products. For example, the high consistency of TI cell lines can support a streamlined approach whereby materials for early non-GMP evaluations can be generated from TI pools. Clone selection for master cell bank (MCB) generation can be based on matching pool product quality attributes and GMP production can proceed with selected clones.
Comparative analyses reveal that key quality attributes such as size exclusion chromatography–liquid chromatography (SEC-LC) main peak, charge variant profiles and N-glycan patterns are comparable between WuXia TrueSite clones and parental pools (Figure 3). These findings demonstrate high consistency and support use of the TI CLD platform pools for non-GMP (or even early clinical) material production, significantly accelerating development timelines while maintaining quality standards.
Figure 3: SEC-LC, cIEF and N-glycan profiles of three mAb molecules and an asymmetric antibody,
showing product quality attributes of pool and clonal cell lines derived from WuXia TrueSite.[/caption]
Accelerating cell line development
Enhancing the efficiency of the drug development process has been a driver of innovation in recent years. For example, in response to the COVID-19 pandemic, several developers (including Eli Lilly, Vir and WuXi Biologics) accelerated timelines by using non-clonal CHO pools to produce GLP-Tox and early-phase clinical material – a strategy known as ‘deferred cloning’.4 This technique uses a stable pool (or a pool of clones) for the preclinical phase, avoiding the bottleneck that single-clone selection can create. This enables earlier toxicology studies and parallel development, significantly shortening development timelines.
WuXia TrueSite can also accelerate timelines. For instance, its proven stability eliminates the need for cell line stability studies. Moreover, consistency of product quality supports a streamlined approach where non-GMP materials can be generated from TI pools.
Through these and other cross-functional efforts, the TI CLD platform can achieve ambitious IND timelines by expediting MCB establishment, thus halving the overall development time to just six months (Figure 4). The accelerated timeline is expected to be applicable to standard antibodies as well as pandemic response proteins. However, regulatory acceptance for non-pandemic programmes remains a hurdle. Despite this, the inherent genomic plasticity of CHO cells indicates that genetically defined stable pools, such as those produced using TI, may be suitable for early-stage clinical manufacturing.
Figure 4: Accelerated IND timeline achieved by application of the TI CLD platform WuXia TrueSite.[/caption]
*The DS and DP manufacturing timelines of WuXia TrueSite TI CMC are shorter than traditional CMC because accelerated GMP DS/DP release is achievable by leveraging reliable in-house testing capabilities. Submission of one-month DP stability data will follow a rolling submission strategy.
Conclusion
Targeted integration is a significant advance in CLD, enabling greater stability and consistency. This leads to marked efficiencies – reduced clone screening, simplified process development and elimination of redundant steps from the critical path – all of which accelerate novel molecules into clinical development.
With biopharma striving to hasten the delivery of life-saving therapies, CLD represents a critical point in achieving this mission. By combining the latest academic advancements with industrial-scale manufacturing expertise, TI CLD reduces technical risks, accelerates development cycles and provides superior process economics. As the fourth generation of the WuXia platform, TrueSite has achieved dual breakthroughs in quality and efficiency, and we expect it to play an important role in the rapidly evolving age of biologics.
About the authors
Tao Sun, PhD, Senior Principal Scientist, Cell Line Development, WuXi Biologics.
Xiaoyue Chen, PhD, Executive Director, Cell Line Development, WuXi Biologics.
Hang Zhou, PhD, Head of Bioprocess Research & Development, WuXi Biologics.
Fei Chen, PhD, Head of Cell Line Development, WuXi Biologics.
References
- Zalma V, et al. CHO Cells For Virus-Like Particle And Subunit Vaccine Manufacturing. Vaccine. 2024;42: 2530-2542.
- Tihanyi B, Nyitray L. Recent Advances In CHO Cell Line Development For Recombinant Protein Production. Drug Discovery Today: 2020;38: 25-34.
- WuXi Biologics Launches WuXia™4.0, Targeted Integration Cell Line Platform TrueSite TI™ to Accelerate Biologics Development with High Titer and Superior Stability. [Internet] WuXI Biologics. Available from: https://www.wuxibiologics.com/press-release/wuxi-biologics-launches-wuxia4-targeted-integration-cell-line-platform-truesite-ti-accelerate-biologics-development-with-high-titer-and-superior-stability/
- McGovern ĀT, Salisbury C, Nyberg G. The Pandemic and Resilience for the Future: AccBio 2021. Prog. 2022;38:e3207.
