Summary
Lonza has developed GSquad® Pro, a next generation vector system that significantly helps increase protein expression in CHO cells. The system combines a new LHP-1 promoter with hyperactive GS piggyBac® transposase technology to deliver higher titers, better product quality, and enhanced expression stability compared to traditional mCMV-based vectors.
The LHP-1 promoter achieves titer increases up to 123% for monoclonal antibodies in internal studies. For bispecific antibodies, the system achieves up to 8 grams per liter, while Fc fusion proteins reach up to 9 grams per liter. In customer projects with difficult-to-express bispecifics, the system delivered a 42% titer increase reaching approximately 5 grams per liter.
The LHP-1 promoter maintains balanced gene expression and demonstrates 97% expression stability across 65 generations. This technology is now deployed across Lonza's global CDMO manufacturing network and is available to licensees.
Lonza's Track Record in Biotherapeutic Manufacturing
Lonza operates as a leading global CDMO with industry leading offerings in cell line construction, process development and optimization, and manufacturing of drug substance for monoclonal antibodies and other recombinant therapeutic proteins. The company manufactured more than 775 large molecules in 2025, including more than 720 preclinical and clinical stage large molecules.
Lonza has expressed more than 100 therapeutic proteins, now on the market, using its expression tools. These products are manufactured across Lonza's global site network or via expression system license holders manufacturing with third party partners. This milestone demonstrates the technical capabilities of Lonza's expression systems and the extensive experience across its global manufacturing network, which includes facilities in Vacaville CA, Portsmouth NH, Boston MA, Cambridge UK, Slough UK, Basel CH, Visp CH, Porriño ES, and Tuas SGP.
The GS gene expression system® remains the platform of choice for expressing diverse therapeutic protein formats. These include antibodies, bispecifics, Fc fusion proteins, and other advanced formats. Since 2012, more than 2000 products have been expressed with the GS® platform in-house at Lonza. In 2023, more than 60% of molecules expressed in Lonza's early development services were non-mAbs. There are now more than 20 launched products on the market that are non-mAbs or advanced antibody formats expressed using the Lonza platform.
Molecule Type Diversity
Lonza has expressed, purified, and analyzed approximately 600 non-mAb products, demonstrating expertise across a broad range of therapeutic formats: Antibodies represent 35% of molecules processed through early development services. Bispecific antibodies account for 22% of products, duobodies make up 18% of the portfolio, one-armed antibodies comprise 7% of molecules, and Fc fusion proteins represent 6% of products expressed.
This diversity validates the GS system® platform's ability to improve CHO cell productivity beyond traditional monoclonal antibody programs.
The GS Gene Expression System®
The GS system® technology platform is a fully integrated high-performance CHO expression platform for recombinant protein expression designed to enable drug discovery and development teams to express a wide variety of therapeutic protein formats at high, stable titers.
Figure 1: An overview of the GS gene expressions system® technology platform
Host Cell Lines
- GS Xceed® CHOK1SV GS-KO®: The standard CHO-K1 derived host cell line with the glutamine synthetase gene knocked out to enable selection.
- GS Effex® FUT8 KO: derivative cell line designed for making afucosylated antibodies with enhanced antibody-dependent cellular cytotoxicity (ADCC).
These engineered CHO hosts support stable expression and enhanced CHO expression efficiency.
Expression Vectors
The GSquad® Pro vector platform represents the latest generation of expression vectors. These vectors integrate into host cells using hyperactive GS piggyBac® transposase technology for both stable and transient gene expression.
Additional vector systems available include GSquad® constant region vectors for streamlined antibody construction and GS® site-specific conjugation vectors for antibody-drug conjugates.
Complementary Technologies
The GS system® platform integrates with several complementary technologies:
- TheraPRO® Production Media: An optimized fed-batch media supporting high titer and excellent PQ.
- GS piggyBac® transposase technology: An engineered hyperactive piggyBac® transposase enzyme designed to insert GS Xceed® expression vector cargos with your gene of interest into the host cell genome with high efficiency.
- GS Discovery® transient expression platform: GS piggyBac® enhanced transient expression system for rapid material generation.
Together, these technologies support scalable CHO biomanufacturing from early research through GMP manufacturing.
Support for Licensees
Customers who license the GS system® platform gain access to the GS® manual portal. This portal provides all protocols and instructions needed to use the platform. Because Lonza uses the same system internally for CDMO services, licensees benefit from decades of practical experience. Lonza also provides technical, process, and regulatory support through a global network of subject matter experts to help licensees optimize the system for their specific needs.
Platform Innovation Journey
Lonza maintains the GS system® platform at the forefront of the industry through continual innovation. Key milestones in the platform's evolution include:
Figure 2: Innovation timeline of the GS expression system® technology platform
At Lonza, our R&D teams continue to innovate on the core GS® platform technology with common focus on areas such as enhanced vector technology and further engineered high-performing host cell lines to support precision bioprocessing. This includes integration of high-throughput automation, data science, artificial intelligence and machine learning for real-time clone-specific optimization.
Precision Bioprocessing Approach
Lonza's vision for next generation CHO bioprocessing centers on precision bioprocessing. This approach enhances synergy between improved expression vector design and engineered CHO host cell factories, supporting sustained performance and CHO productivity improvement across a broad range of therapeutic protein formats.
Key components of precision bioprocessing include:
- Enhanced DNA and cell expression technologies that work together as an integrated system.
- High-throughput automation enabling rapid screening and optimization of multiple parameters.
- Data science and artificial intelligence/machine learning applications for predictive modelling and optimization.
- Real-time, clone-specific media and feed optimization tailored to individual cell line characteristics.
- Understanding of product scaffold sequences and their impact on expression and quality.
- Downstream processing optimization integrated with upstream expression strategies.
Figure 3: Lonza’s vision for next generation CHO bioprocessing
This integrated approach moves beyond optimizing individual components in isolation. Instead, it focuses on understanding and enhancing the interactions between vector design, host cell characteristics, culture conditions, and product attributes. The goal is to improve CHO cell productivity and enable more efficient manufacturing of increasingly complex therapeutic proteins.
Hyperactive GS piggyBac® Transposase Technology
Expression vector design plays a critical role in determining the success of a biomanufacturing campaign. Lonza has improved integration sites after transfection by implementing hyperactive piggyback transposase technology.
How the Technology Works
Figure 4: An overview of the hyperactive GS piggyBac® transposase technology
GS expression vectors have been modified to include piggyBac recognizing inverted terminal repeat (ITR) sequences. These vectors are transfected in to the cell with the piggyBac enzyme delivered as optimized mRNA. The mRNA is translated into the active protein, which binds to the ITRs. The transposase then uses an active cut-and-paste mechanism to insert the cargo into open, accessible regions of the CHO genome where expression is high and stable over a long term.
Using this active transposition event improves the overall quality of vector integration compared to legacy random integration methods. The result is an overall uplift in expression output from a GS® expression vector.
Performance Benefits
Clones made using GS piggyBac® technology show an average uplift in titer compared to random integration. In a case study, GS piggyBac® clones demonstrated approximately 90% average increase in titer during clonal evaluation. The distribution of clones in a transfectant pool made using GS piggyBac® was found to be shifted more towards the higher productivity range than clones generated using random integration. This means the probability of finding a highly productive clone capable of supporting manufacturing increases significantly.
Lonza has deployed GS piggyBac® transposase technology across its global CDMO services network based on these performance advantages.
Titer Performance Across Molecule Types
Figure 5: Molecules produced using hyperactive GS piggyBac® transposase technology show high titers across multiple molecule types
Bispecific Antibodies
Bispecific antibodies typically achieve up to 8 grams per liter using GS piggyBac® technology. The system delivers stable high titers across the development cycle, from lead optimization through to cell line development (CLD) and GMP manufacturing.
Fc Fusion Proteins
Fc fusion proteins typically reach up to 9 grams per liter with GS piggyBac® integration. This allows for confidence across the development journey that high titers will be obtained for this types of molecules.
Transient Gene Expression
Lonza applies GS piggyBac® technology to improve transient gene expression titers as part of the GS Discovery® system, which represents a novel application of this technology. Transient expression data for antibodies and bispecific antibodies demonstrate clear titer benefits when using GS piggyBac® enhanced workflows compared to standard transient approaches.
Figure 6: GS piggyBac® transient process shows improved titers over 14 days when compared with a standard GS® transient process
The GSquad® Pro Vector system
Lonza has replaced the traditional mCMV promoter with the new LHP-1 promoter in its GSquad® Pro vector system. This change delivers significant improvements in titer, product quality, and expression stability. Internal case studies demonstrate that the LHP-1 promoter can increase monoclonal antibody titers by up to 123% compared to mCMV.
Transcriptional Performance
The LHP-1 promoter generates higher transcriptional output compared to mCMV. For antibodies, the heavy and light chain genes show much more balanced expression when controlled by LHP-1. This high transcriptional output combined with gene balancing contributes to improved titers.
The relative transcriptional output from discrete genes in a GS® vector influences overall product expression. The LHP-1 promoter provides more balanced expression of mAb heavy chain and light chain mRNA combined with high transcriptional output overall.
Figure 7: LHP-1 shows higher transcriptional output compared with mCMV
Cell Specific Production Rate
Fed batch culture processes typically follow a biphasic pattern. The early phase generates productive biomass. The latter phase generates the majority of product during the stationary phase.
With mCMV promoters, cell specific production rate remains remarkably consistent across the entire fed batch culture, regardless of gene order. With LHP-1 promoters, cell specific production rate shows a significant uplift as culture progresses from early to late phase.
The LHP-1 promoter upregulates product expression during the stationary phase of culture. This enhanced separation of the growth and production phases allows cell resources to be more efficiently directed.
Expression Stability
High titers must be backed by solid expression stability for commercial manufacturing. The LHP-1 promoter demonstrates outstanding stability across approximately 65 generations of cell culture.
Lonza compares early and late generation cells for changes in productivity. A change of 30% serves as the cutoff to indicate a stable clone. Example datasets using LHP-1 to control antibody heavy and light chains show expression stability of 97%. This performance makes the promoter fully compatible with commercial scale manufacturing.
Figure 8: LHP-1 promoter shows stable clone generation across multiple clones
Performance with Multi-Chain Proteins
Bispecific Antibodies
Testing in stable pools compared mCMV performance with the new LHP-1 promoter across different gene orders. mCMV allows expression optimization by changing gene order, particularly for certain molecules. However, LHP-1 consistently generates the highest titer stable pools above mCMV across all gene order configurations tested.
Product quality analysis demonstrates that higher titers observed with the GSquad® Pro vector system and LHP-1 promoter have no detrimental effect on correct chain pairing rates. Bispecific antibodies produced with LHP-1 maintain appropriate assembly characteristics even at elevated expression levels.
Fc Fusion Proteins
Single-chain Fc fusion proteins illustrate the trade-off between titer and product quality. With mCMV vectors, titer can be optimized by changing gene order. However, product quality, measured as the percentage of correctly assembled molecule, drops as titer increases using mCMV.
With LHP-1 vectors, titer remains much more consistent across gene orders, as does product quality. When comparing the best stable pools from mCMV (optimal titer with acceptable product quality) to LHP-1 pools, LHP-1 comfortably outperforms on titer while maintaining the right product quality profile.
For single-chain variable fragment (scFv) fusion proteins specifically, the LHP-1 promoter drives both increased titers and excellent product quality. Testing across different gene arrangements demonstrates that LHP-1 maintains correct chain pairing rates while delivering higher expression levels. This performance makes the system well-suited for complex fusion protein formats that require precise assembly.
Customer Project Results
A recent customer project required expression of a difficult-to-express bispecific molecule. Side-by-side cell line construction compared top clones made using mCMV based vectors and the new LHP-1 based GSquad® Pro vector system.
Clones selected for research cell bank (RCB) generation showed that the average performance of LHP-1 generated clones exceeded mCMV-generated clones significantly. The GSquad® Pro vector system using the LHP-1 promoter enabled approximately a 42% increase in clonal titer, reaching approximately 5 grams per liter for this challenging molecule.
GSquad® Pro Vector Design and Screening
The GSquad® Pro vector system enables fast, simple assembly of expression vectors encoding for one, two, three, or four product genes. This flexibility supports efficient construction of vectors for multichain products with varying complexity.
Figure 9: The GSquad® Pro vector system enables flexible and efficient assembly of expression vectors coding for up to 4 product genes
The key features of this the GSquad® Pro vector system include:
- High efficiency one-pot assembly of final GS piggyBac® vector
- Identical cloning workflow for all vectors regardless of the number of product genes
- Product gene expression controlled by new high-strength gene promoter LHP-1
- Easy sequencing of the final vector using in-built sequencing primer binding sites
- Inverted Terminal Repeats (ITRs) contained within the destination vectors enable construction of high titre stable pools using GS piggyBac® hyperactive transposase technology
Vector Format Optimization
Vector design influences product assembly and titer outcomes. Key variables include gene copy numbers and gene arrangement. The GSquad® Pro system allows rapid screening of different vector formats to identify optimal configurations:
- Triple gene vectors (TGV): Encode three product genes at defined ratios, such as LC1:HC1:HC2 at 1:1:1.
- Quadruple gene vectors (QGV): Encode four product genes at different ratios, such as LC1:HC1:HC2 at 2:1:1, with varying gene orders.
Early Screening Strategy
Product generation and analysis can be performed on stable pools to evaluate vector designs before committing to full cell line development. This approach involves:
- Construction of multiple vector designs with different gene orders and copy numbers.
- Creation of stable pools from each vector design.
- Fed batch culture of pools.
- Purification using protein A affinity chromatography.
- Titer determination using UV-Vis spectroscopy.
- Size exclusion high performance liquid chromatography (SE-HPLC) to quantify monomer content.
- SDS-PAGE analysis to evaluate product assembly.
This early screening provides information on product assembly characteristics in Lonza's proven CHOK1SV GS-KO® system. This approach allows for selection of the vector format with the highest titers of correctly assembled product, maximizing the chance of success in subsequent cell line development.
Combinatorial Library Approach
Lonza is developing combinatorial systems for rapid screening of vector element combinations. This library approach tests multiple chain order arrangements and promoter combinations simultaneously. The method saves time and increases efficiency by systematically exploring the design space for optimal expression of multichain products.
Data from preliminary studies demonstrates that multiparameter and chain arrangement combinatorial libraries expand the design options available for complex molecules. This systematic approach helps identify the best configuration for each unique molecule early in development.
Benefits of GSquad® Pro
The GSquad® Pro vector system with LHP-1 promoter technology delivers multiple benefits when used with Lonza's CHOK1SV GS-KO® cell line:
Support More Efficient Biomanufacturing
Higher titers of up to 123% relative to mCMV for a range of molecules including monoclonal antibodies, bispecific antibodies, and fusion proteins. This performance improvement can support more economically viable commercial scale manufacturing.
Enable Faster Material Generation
Faster and more consistent pool recovery rates compared to mCMV. This acceleration enables earlier generation of material for toxicology studies or faster progression to cell line development.
De-risk the Development Journey
Higher titers achieved without detriment to product quality attributes. The system maintains correct chain pairing rates and monomer content even at elevated expression levels. This balanced performance reduces the risk of quality issues during scale-up to commercial bioproduction.
Avoid Development Delays
Excellent clonal expression stability of 97% in Lonza studies. This stability avoids the risk of increased timelines and additional workload during cell line development that can occur when expression levels decline over successive generations.
This technology is now standard for Lonza's in-house manufacturing operations and available to all licensees of the GS system® technology.
Frequently Asked Questions
What are the advantages of using a single vector approach versus multi-vector co-transfection?
The single vector approach reduces uncertainty in the transfection process. With co-transfection, achieving good transfection levels for all different vectors adds complexity. The single vector platform provides sufficient optimization scope through promoter selection and gene order variation. This approach also de-risks development because all genes integrate into the host cell simultaneously. Multi-vector approaches remain viable for specific applications, but single vector systems offer more predictable outcomes for most projects.
Does the GSquad® Pro system address DNA recombination concerns with repeated promoter elements?
Repeated sequence elements in expression vectors can cause recombination events in both bacterial propagation and CHO cells. This is a well-known phenomenon affecting expression stability over time. The GSquad® Pro system incorporates greater sequence diversity to help mitigate these effects. Expression stability, which represents the primary concern with repeated elements, depends on multiple factors. The LHP-1 promoter technology specifically addresses many stability challenges through its design and performance characteristics.
How large is the LHP-1 promoter compared to mCMV?
The mCMV promoter is 492 base pairs. The new LHP-1 promoter is 610 base pairs. In the context of a typical expression vector for a bispecific antibody (approximately 19 to 20 kilobase pairs total), this size difference is negligible. The promoter size change has minimal impact on plasmid handling in bacteria or transfection efficiency in CHO cells.
Can Lonza's expression technologies be applied to viral vector production?
Lonza offers different cell lines and expression platforms that can be applied to various production needs, including viral vector manufacturing. The optimal approach depends on specific product requirements, vector type, and production scale. For specialized applications such as lentiviral or retroviral vector production, Lonza can discuss tailored solutions based on project needs.
How does gene order optimization work with the GSquad® Pro system?
Gene order refers to the arrangement of different genes within the expression vector. For multi-chain proteins like bispecifics, varying the order in which genes appear can affect expression levels and product quality. The GSquad® Pro system allows testing of different gene order configurations. The LHP-1 promoter shows less sensitivity to gene order compared to mCMV, meaning it delivers more consistent high performance across different configurations. This reduces the optimization burden during cell line development.
What support does Lonza provide to licensees using the GS system®?
Licensees gain access to the GS® manual portal containing all protocols and procedures for using the platform. Because Lonza uses the identical system for internal CDMO manufacturing, licensees benefit from decades of operational experience. Lonza also provides access to a global network of subject matter experts who can help troubleshoot challenges and optimize the system for specific molecules or production requirements.
Is the GSquad® Pro system available now?
The GSquad® Pro vector system is deployed across Lonza's global CDMO manufacturing network and available to all GS system® technology licensees. The technology represents the current standard for Lonza's internal manufacturing operations.
How does the system support transient expression?
The GS Discovery® transient expression platform uses GS piggyBac® transposase technology to boost transient gene expression titers. The system offers two protocols that balance speed versus ultimate titers. Using GS piggyBac® enhanced transient expression, titers increase substantially compared to standard transient processes for both monoclonal antibodies and bispecific antibodies. This approach enables faster material generation for early stage research and toxicology studies while maintaining consistency with the stable expression platform used for later development stages.
Can the system support molecules from early discovery through commercial manufacturing?
The GS system® technology is proven for all stages of development from early discovery through GMP manufacturing. Using one industrially relevant expression system across all development stages helps de-risk the journey to commercial bioproduction. Examples include bispecific antibodies and Fc fusion proteins that have progressed from lead optimization through bulk stable pools, cell line development, and into GMP manufacturing using the same core technology platform. This continuity reduces technical risk and accelerates timelines by eliminating platform transfers between development stages.
For more information about the GS system® technology, contact our experts or visit the technical resources section on Lonza.com.
