Antibody Drug Conjugate Glycan Engineering Platforms, Glycoform Engineering of Next Generation Antibodies, Glycoengineering platforms are technical service offerings which address the needs for optimally-defined glycan structures on antibody Fc and Fab glycans for ADC conjugation site control, effector function control and improved drug conjugation homogeneity. Modification of glycosylation through chemoenzymatic remodeling of glycans or engineering of host cells allows for improved efficacy and safety profiles and batch-to-batch consistency. These platforms support a variety of modalities such as bispecific antibodies, targeted drug conjugates (TDCs), and traditional monoclonal antibodies (mAbs) as developers shift toward these novel modalities that demand highly specific quality attributes.
Schematic representations of human antibody structures and attached glycans.1,5
Antibodies designed for therapeutic use are transitioning from simple monospecific formats towards antibody drug conjugates (ADC) and bispecific formats each with unique glycosylation needs. Antibodies typically leverage glycans for interactions with Fc receptors. Antibody drug conjugates require glycans that allow for homogeneous and stable conjugation of a cytotoxic drug. Bispecific antibodies require strict control over glycosylation to balance dual target specificity with effector functions. This advancement will require a high degree of engineering that is tailored to each antibody platform's structural limitations. Glycosylation is considered a "quality attribute" because it has significant impacts on potency, pharmacokinetics, and immunogenicity of therapeutic antibodies and is highly variable based on cell line metabolism and culture conditions. Glycosylation profiles differ from batch to batch unlike protein sequences and can alter functionality and clearance of therapeutic antibodies. For example, antibody binding to Fc gamma receptors and complement can be altered by the composition of attached glycans. Additionally, glycoforms that contain non-human sugars can be immunogenic. Current regulatory guidelines require extensive characterization and control over glycans. Glycans directly impact the ability to manufacture consistent product and predict clinical performance. The core Fc N-glycan attached to N297 helps maintain conformation of the Cdomain through multiple non-covalent interactions that shield the protein from aggregation and proteolysis. Functionality can be altered by glycosylation composition.
Table 1 Evolution of Antibody Modalities and Glycan Engineering Requirements
| Antibody Modality | Structural Complexity | Glycan Function | Engineering Priority |
| Conventional monoclonal | Homodimeric, single specificity | Effector function modulation | Optimization of ADCC/CDC activity |
| Antibody-drug conjugate | Cytotoxic payload attachment | Conjugation site; stability | Site-specific remodeling; DAR control |
| Bispecific | Dual antigen recognition; asymmetric | Effector engagement; half-life | Tuning for immune cell redirection |
| Fc-fusion protein | Cytokine or receptor extracellular domain | Stability; receptor interaction | Consistent glycosylation across domains |
Antibody-drug conjugates (ADC) and new antibody constructs represent another application of glycan engineering, as these therapeutics are not only comprised of multiple antibody domains, but are also linked to cytotoxic payloads. Engineering glycans on these new antibody formats is complex due to the necessity to understand how glycosylation can affect not only the typical Fc mediated functions, but also conjugation site availability, drug stability and avidity towards cellular receptors. Glyco-engineering principles can be applied to these new modalities to help increase therapeutic potency and control manufacturing variability.
Fc glycosylation can impact ADC pharmacology through effects on receptor binding to various Fcγ receptors and complement proteins like C1q. Binding to Fcγ receptors can impact clearance rates and toxicities due to antibody recycling through immune cells, while binding to complement proteins like C1q can result in inflammatory toxicities. ADC developers may want to tune glycosylation to maintain antibody integrity and half-life while knocking out such effector functions. Modification of Fc glycosylation can also affect ADC hydrophobicity and aggregation potential.
Fc glycans significantly affect the antibody's conformational stability, aggregation propensity and circulating half-life. First, binding of N-linked glycans to Cdomain helps preserve antibody's Fab region in an "open" confirmation by keeping the glycans attached to protein scaffold at a distance from each other through multiple non-covalent interactions with the protein backbone. This ability to prevent irreversible aggregation-denaturation ultimately affects bioavailability. Structural changes to glycans also affect an antibody's solubility and melting temperature. Highly branched and terminally fucosylated glycans increase protein stability under chemical and physical stress. This robustness during antibody production/storage helps increase the shelf-life of the antibody drug product. Furthermore, alteration in glycan structure also affects the serum half-life. Antibodies with high mannose glycans have shorter half-life due to enhanced recognition and clearance by asialoglycoprotein receptors in liver, while increased sialylation is associated with increased serum half-life possibly due to reduced non-specific interactions with extracellular proteins and increased recycling by FcRn.
Bispecific antibodies have particular glycosylation considerations due to their complexity and bispecificity. Challenges include their multivalent nature and specificity, as engineered Fc domains or differences in glycosylation sites between the heavy chains must be consistent to ensure product quality and expected pharmacokinetics. Glycoforms can be designed in bispecific antibodies to alter desired effector function, such as increasing ADCP activity against cancer cells while turning off undesired effector functions. Bispecific antibodies also have the potential for having more than one glycosylation site across various protein chains. As such, heterogeneity of glycans between domains must be managed to prevent issues such as increased aggregation, binding avidity, or immunogenicity. Glycosylation can also play a role in maintaining the integrity of the bispecific antigen recognition.
Our glycan engineering platform simplifies antibody-drug conjugate (ADC) development by enabling control of glycans to improve ADC potency and stability. Our platform offers tools for precise control of antibody Fc glycosylation to fine-tune immune effector functions, glycoengineering strategies for site-specific conjugation, and engineered host cells for improved batch consistency. Additionally, our platform can help create uniform drug loads while maintaining antibody targeting ability and structural integrity. Ultimately, glycan control can reduce ADC heterogeneity and aid in the development of highly engineered biotherapeutics with improved drug-like properties.
Table 2 Glycan Engineering Capabilities for ADC Development
| Solution Category | Technical Approach | Strategic Outcome |
| Fc optimization | Glycosylation pattern modulation | Enhanced immune cell engagement or silencing as appropriate |
| Site-specific conjugation | Enzymatic glycan remodeling | Homogeneous drug loading with preserved structural integrity |
| Heterogeneity reduction | Process and cell line engineering | Batch-to-batch consistency in glycan profiles |
| Manufacturing scalability | Pathway modulation in expression systems | Sustainable production of defined glycoforms |
Optimization of afucosylation has been shown to improve ADC efficacy by increasing antibody-dependent cell cytotoxicity (ADCC), providing another mechanism of tumor cell killing in addition to that of the payload. Afucosylation, or the removal of fucose from the Fc region of the antibody, increases its affinity for binding to FcγRIIIa receptors on immune effector cells such as natural killer cells and macrophages. Thus, afucosylation may allow for antibody-dependent immune-mediated killing of tumor cells resistant to the cytotoxic payload. Altering galactosylation has been shown to improve ADC efficacy by affecting complement-dependent cytotoxicity (CDC). Increasing terminal galactose residues enhances binding of the ADC to C1q, thereby increasing activation of the classical complement pathway and formation of the membrane attack complex. Optimization of ADC effector functions aims to balance these activities to promote anticancer efficacy by increased immune cell recruitment while limiting toxicity from inflammation without compromising payload-induced cell death.
Fc N-glycan specific conjugation takes advantage of its unique chemistry compared to other lysine or cysteine conjugation methods to allow site-specific attachment of payloads. Endoglycosidases and glycosyltransferases can be used to enzymatically modify glycans on antibodies to convert heterogeneous glycans into homogeneous glycans with exposed functional handles. These functional handles can be targeted for drug linker conjugation allowing for site specific conjugation of drugs to the Fc N-glycan, resulting in an ADC with a defined drug load and homogeneous glycoform. This improves pharmacokinetics and therapeutic index relative to ADCs conjugated at random sites. Homogeneity of DAR can decrease variability in potency and toxicity leading to better quality control between manufactured batches. Importantly, this site-specific conjugation leaves the rest of the antibody intact preserving its structure and function.
Engineering cells to produce homogeneous glycoforms can decrease structural heterogeneity present during ADC production and characterization. Limiting factors such as cell line, cell culture conditions, and purification can help decrease MH from non-glycosylated species, high mannose glycans, and incompletely processed complex glycans. Many production controls attempt to limit glycan heterogeneity by favoring processing towards common terminal groups that aid in conjugation efficiency and expected pharmacokinetics. Improvements in batch consistency allow for tighter control of QA metrics and should lead to less variation between production runs. Stable production parameters allow for ease of scaling up ADCs for clinical doses based on defined molecule properties rather than a statistical average of a mixture.
CHO cell lines can be genetically modified to stably produce therapeutic antibodies with tailor-made glycosylation patterns for ADCs. Genetic manipulation of glycosyltransferases including overexpression or knockdown can shift glycoform distribution towards the glycoform of interest, such as increased galactosylation and specific afucosylation. Genome editing with CRISPR can knock out genes like fucosyltransferases or add additional glycosylation pathways in order to create a host cell line that will reliably produce one glycosylation pattern. The glycan profile needs to be consistent when scaled up to GMP manufacturing. This includes demonstration that glycosylation is consistent from development through to manufacturing batches without affecting viability or productivity.
Applications of glycoengineering to next-generation antibodies include fine-tuning of effector functions for bispecific antibodies, antibody drug conjugates, and checkpoint inhibitors. This allows for tuning of ADCC, complement-dependent cytotoxicity (CDC), or anti-inflammatory responses for specific indications. Adjusting levels of core fucose, terminal sialic acid, or even absence of glycans can increase cytotoxicity against tumor cells, prevent effector function, or be used to balance high potency with longer half-life. These modifications can aid in the development of multispecific antibodies that can be produced in a consistent manner.
Schematic presentation of chemoenzymatic glycan remodeling for glycosite-specific antibody conjugation.2,5
Glycoengineering of bispecific antibodies introduces additional complexities compared to monoclonal antibodies. Bispecific antibodies may require tuning of effector functions between two antigen-binding sites. Structural stability may also need to be incorporated into engineered Fc domains. Optimization of glycans in bispecific antibodies could allow for desired NK cell activity toward cancer cells while avoiding activating complement pathways that could be unsafe. The arrangement of glycans also affects the orientation of antigen binding domains that determine avidity as well as targeting ability of healthy versus pathogenic cells. Bispecific antibodies may require specific glycan tweaks such as afucosylation to enhance anti-tumor activity and increasing sialylation to reduce inflammation for example in autoimmune diseases. Homogeneity of glycans is also important in bispecific antibodies to prevent batch to batch variability in manufacturing and pharmacological outcomes as they must target two antigens.
Fc silencing and activation are two extremes of glycoengineering desired for different therapeutic applications where effector recruitment is respectively undesired or desired. Mutation of the amino acid residue N297 to any residue other than asparagine abolishes N-linked glycosylation at this site and yields aglycosylated antibodies that lack Fc gamma receptor and complement binding activity. This may be desirable for checkpoint inhibitor antibodies or antibodies treating autoimmune diseases, where effector function activation can be detrimental to the intended function of the drug or promote host tissue damage. Alternatively, for maximal effector function enhancement, the removal of core fucose can be performed to greatly increase binding affinity to activating Fc gamma receptors on immune effector cells such as NK cells and macrophages. Alterations to amino acids in the lower hinge region have also been shown to diminish certain effector functions while leaving others intact.
Checkpoint inhibitors should not have effector function. Anti-PD-1, anti-PD-L1 and anti-CTLA-4 antibodies work by blocking these proteins, not killing cells. An antibody with Fc-mediated cytotoxicity will be toxic in this application. Therefore, Immune checkpoint inhibitors should be aglycosylated or highly sialylated to avoid ADCP of checkpoint-positive T cells or tumor cells that need to be left intact for the drug to work. Effector function also contributes to CRS and other infusion-related toxicities that can occur with these antibodies. Furthermore, if these antibodies have effector function, they will deplete T cells. This is important for anti-PD-1 therapies where it is necessary to keep as many T cells intact.
Attempts to tune antibody-dependent cell cytotoxicity potency along with changes to serum half-life often require glycans that activate specific immune cells without detrimentally affecting serum half-life or manufacturability. Antibodies with increased amounts of high mannose glycans have increased antibody dependent cell cytotoxicity activity but have been shown to have lower serum half-lives due to rapid clearance by the asialoglycoprotein receptor in the liver. Fully sialylated or galactosylated antibodies have increased half-lives due to interaction with the Fc neonatal receptor but may decrease antibody dependent cell cytotoxicity activity. Glycan engineering may require intermediate levels of modified glycans or may limit glycan modifications like high mannose to specific areas of the antibody to leave the remainder of the antibody with complex glycans. Fine-tuning the production process can allow for similar glycosylation profiles between small and large scale production so there is not as much batch variation between how antibody-dependent cell cytotoxicity and serum half-life may be affected.
Quality control (QC) and analytical characterization of glycoengineered antibodies/ADCs involve multiscale analyses that integrate structural glycobiology, biophysical profiling, and functional activity assays to confirm glycoengineering strategies successfully produce desired functional outcomes at commercial scale while meeting predefined quality attributes. Techniques involved in these analyses include, but are not limited to: carbohydrate heterogeneity profiling, site-specific conjugation level analysis, immune receptor binding, and stress stability profiling. Characterization of these attributes inform QC decision trees, batch release, and comparability studies.
Mapping of glycosylation (glycan profiling) is performed by using orthogonal methods of separation, usually followed by mass spectrometry-based detection methods, to describe structural variants (glycoforms) and their relative quantities. LC-MS can be used to determine intact mass and heterogeneity of antibody subunits. This allows separation of glycoforms that may vary by presence or absence of fucose, galactose and sialic acid. Release glycans can be separated by hydrophilic interaction liquid chromatography (HILIC), based on polarity. This allows quantitation of each specific glycan. Alternatively, CE can separate charged glycans based on electrophoretic mobility and can be used for high-throughput screening. Taken together these techniques allow analysis of afucosylation, high mannose, sialylation, and galactosylation which impact activity and clearance.
Drug-to-antibody ratio (DAR) and site of conjugation (SEC) are important attributes of ADCs, as they impact ADC efficacy, stability, and safety. MS can characterize DAR and SEC on several structural levels. Ultra-performance liquid chromatography (UPLC) coupled to MS of intact ADCs can be used to determine both the mean DAR and distribution of drug loads across species. Middle-down approaches using enzymatic digestion can be used to generate fragments for high-resolution MS, allowing improved separation of ADC species with site-specific conjugation. Peptide mapping followed by MS/MS can identify the exact residue modified for SEC analysis. Coupled with linker stability data, this can show how conjugation location impacts linker stability. Label-free quantitation or stable isotope labeling can also be performed for accurate quantitation of site-specific drug load.
Fcγ receptor binding assays and functional assays measure the effects of glycans on antibody binding to immune effector cells and biological activity downstream of binding. Techniques such as surface plasmon resonance or biolayer interferometry can be used to measure real-time kinetics of binding to activating or inhibitory Fc receptors and observe differences in affinity and stability of the complex caused by afucosylation or sialylation. Reporter gene assays can be performed on cells expressing Fc receptors to quantitatively measure activation of the receptor after antibody binding and translate binding kinetics into functional outcomes. NK cell-based cytotoxicity assays measure the impact of glycoengineering on biological antibody dependent cell-mediated cytotoxicity, and antibody-dependent cellular phagocytosis assays can be used to measure macrophage engagement. All these assays can be used to confirm the functionality of glycan alterations, whether the goal is increased cytotoxicity for cancer therapeutics or decreased inflammation for therapeutics targeting autoimmune diseases.
Examining the stability and aggregation profile helps determine how glycan modifications affect the stability of the antibody or ADC. Aggregates may arise during production and storage and may lead to product- related adverse events when administered to patients. Techniques such as size exclusion chromatography with multi-angle light scattering detection allows for characterization and analysis of intact molecules and high molecular weight species, whereas dynamic light scattering can be used to quickly screen aggregation under different conditions. Chemical and physical forced degradation studies (exposure to heat, light, oxidation, etc.) can indicate sensitivities that the product may have and subsequent formulation and storage conditions can be designed to mitigate these instabilities. Glycan engineering should not make a molecule more susceptible to these modifications. Monitoring known degradation products such as methionine oxidation or deamidation of asparagine can be easily measured to show chemical stability. Shelf life and storage conditions can be determined by stability studies.
Engineering glycans in next generation antibody formats is challenging due to the complexity added by both the carbohydrate changes and diversity of formats used in current bioconjugates. This includes ensuring batch consistency for multi-entity molecules, scalability and robustness of these processes, changing regulatory requirements for complex glycoproteins, and safety concerns related to immunogenicity changes. Solutions for overcoming these challenges include cell line and upstream process controls as well as thorough downstream characterization.
Structurally, ADCs are complex molecules mainly because of the heterogeneous nature of linkage of the cytotoxic payload to the linker followed by conjugation to the carrier antibody, which itself displays heterogeneity due to the glycan attached to it. This results in various ratios of drug linked to antibody along with heterogeneous conjugation sites. Also, the physiochemical properties of ADCs vary due to the antibody, linker, and payload structure. Their structural diversity leads to challenges in their production and quality control analysis. Payload hydrophobicity may lead to aggregation as well as interfere with glycan recognition. To limit structural heterogeneity, site-specific conjugation methods have been developed that involve modifying a glycan on the antibody to create a homogenous conjugation site.
Scale-up of glycoengineered cell lines from lab-scale to commercial-scale manufacturing often results in glycosylation inconsistencies. Shear, dissolved oxygen levels, and nutrient supply all vary with increased bioreactor size, which may change the kinetics of Golgi-resident glycosyltransferases. These variations may result in increased high mannose glycosylation, heterogeneous fucosylation, or faulty terminal glycosylation that falls outside of predetermined product quality attributes. Glycosylation consistency can be maintained by thoroughly characterizing the process to establish design spaces and utilize proper process analytical technology (PAT) tools to monitor.
As far as regulation of glycoengineered antibodies is concerned, agencies will need substantial data showing that modifications to glycosylation patterns do not present additional safety concerns or affect product quality. Regulatory agencies will likely require thorough structural analysis to demonstrate that heterogeneity in glycans is controlled within established specifications and that any changes to the production process do not negatively impact the known safety profile or efficacy of the product. Classification of glycosylation as a critical quality attribute (CQA) will require stringent analytical characterization, understanding of the glycosylation process, and established comparability if the production process is transferred to a new facility or altered in any way. Early discussion with regulators of glycoengineering plans will allow manufacturers to gain agreement on the range of glycans that are acceptable and any necessary validation.
Different glycosylation profiles may introduce new epitopes or foreign glycans that can induce unwanted immunogenicity to antibody drugs. Increased effector function caused by afucosylation or other glycoforms can also mediate on-target or off-target toxicity by binding to cells with low antigen levels that are normally not targeted. Anti-drug antibodies can also develop if the glycan itself is immunogenic. As such, when using non-human systems or engineering glycans with enzymes, immunogenicity risk should be assessed. Developmental steps should be taken to avoid using sugars that are not found in humans or extensively testing for immunogenicity if they are used. Effector functions can also be modulated to avoid overactivation of the immune system.
Table 3 Immunogenicity Risks and Mitigation in Glycan Engineering
| Risk Category | Potential Consequence | Mitigation Strategy |
| Neo-epitope exposure | Humoral immune response against deglycosylated regions | Structural modeling and epitope prediction |
| Non-human glycans | Anti-carbohydrate antibody development | Host cell selection with human-compatible machinery |
| Effector enhancement | Off-target cytotoxicity against normal tissues | Dose optimization and target selectivity verification |
| Aggregated species | Enhanced immunogenicity potential | Formulation development and aggregation monitoring |
Glycan engineering for antibody-drug conjugates (ADCs) and next-generation antibody formats requires a highly integrated approach that connects Fc glycosylation control, conjugation chemistry, functional validation, and regulatory strategy. Our platform combines deep expertise in antibody glycoengineering with advanced biologics development capabilities to deliver optimized, scalable, and development-ready solutions tailored to complex therapeutic modalities.
In ADC and multispecific antibody development, glycosylation directly influences stability, effector function, conjugation efficiency, and overall therapeutic performance. We integrate glycan engineering with conjugation strategy design to ensure functional and structural coherence.
By aligning glycoengineering with conjugation chemistry, we help maximize efficacy while maintaining product consistency and safety.
Complex antibody modalities require seamless coordination across discovery, process development, and regulatory preparation. Our end-to-end support ensures that glycosylation strategies are aligned with both scientific objectives and clinical development timelines.
This integrated development pathway reduces translational risk and accelerates clinical readiness.
ADCs, bispecific antibodies, and other next-generation biologics present unique structural and functional challenges. We design tailored glycoengineering strategies that account for molecule architecture, mechanism of action, and safety considerations.
Our customized approach ensures that glycan modifications are purposeful, data-driven, and aligned with the overall therapeutic profile.
Glycosylation is recognized as a critical quality attribute in ADCs and advanced antibody formats. We implement scalable glycoengineering and control strategies designed to meet regulatory expectations and support long-term manufacturing consistency.
Our focus is not only on optimizing glycan structures but on delivering regulatory-ready solutions that support clinical progression and commercial success in advanced biologic development.
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