GalNac Ligand Design&Synthesis Service
Overview
The delivery of nucleic acid therapeutics remains the most critical barrier to clinical success. CD BioGlyco addresses this challenge with our specialized GalNAc ligand design & synthesis service, providing the gold-standard solution for highly efficient, liver-specific drug targeting. GalNAc is a powerful targeting ligand that recognizes the asialoglycoprotein receptor (ASGPR), a C-type lectin abundantly and selectively expressed on the surface of hepatocytes (liver cells).
The success of GalNAc conjugation lies in its mechanism: triantennary GalNAc ligands exhibit ultra-high affinity for the ASGPR, often showing binding constants in the low nanomolar range. This leads to rapid, receptor-mediated endocytosis, effectively shuttling the therapeutic oligonucleotide—whether siRNA, ASO, or an anti-miR—directly into the target cell cytoplasm. We leverage decades of scientific expertise and high-end chemical synthesis capabilities to custom-engineer GalNAc conjugates that maximize potency, enhance stability, and accelerate your therapeutic candidate toward clinical approval.
Core Technologies
We employ a flexible and robust suite of synthetic technologies designed to meet the rigorous demands of preclinical and clinical development, ensuring maximum potency and scalability of your GalNAc-oligonucleotide conjugate.
- Multivalency and Spatial Engineering
The efficacy of GalNAc conjugation is intrinsically tied to the clustering effect. ASGPR functions as a trimer, requiring a multivalent ligand to achieve high-affinity binding. Our core competency lies in synthesizing optimized triantennary GalNAc clusters that precisely mimic the natural high-affinity ligand structure. Research confirms that optimal binding affinity is achieved when the three GalNAc moieties are spatially oriented with a mutual distance of approximately 20 Å (2 nm), which we achieve through proprietary, meticulously engineered linker scaffolds, often derived from branched amino acid backbones like lysyl-lysine or simplified tris-acid architectures.
- Dual-Platform Synthesis for Unrivaled Purity and Scale
We offer both solid-phase and solution-phase strategies, allowing us to select the optimal route based on your required scale and structural complexity:
- Solution-Phase Cluster Conjugation
This is the preferred method for producing large quantities of high-purity, multivalent conjugates. We synthesize the complex, triantennary GalNAc cluster independently and activate it—typically using highly efficient pentafluorophenyl (PFP) ester chemistry—before coupling it to a purified, 5'-hexylamino-modified oligonucleotide intermediate in solution. This approach bypasses the limitations of solid-phase synthesis for large clusters, resulting in higher yields and superior purity material. - Solid-Phase Phosphoramidite Integration
For rapid screening and smaller-scale research projects, we employ highly active, non-nucleosidic GalNAc phosphoramidites. These building blocks are integrated directly into the oligonucleotide sequence during automated synthesis. While expedient, this approach is typically reserved for incorporating monovalent or certain simplified multivalent GalNAc designs.
Precision Liver Targeting: GalNAc Design & Synthesis
Our service offers unmatched breadth and depth to support every phase of drug development, from initial discovery to commercial production.
- Scale and Purity Customization
We offer synthesis scales from small research quantities (mg) for initial screening up to large-scale, multi-kilogram quantities for advanced preclinical trials and commercial manufacturing, with purity options ranging from 80% to ultra-pure 95% verified by HPLC or CE.
- Comprehensive Structure Classes
We provide reliable synthesis of all major immunostimulatory classes, including the B-class (strong B-cell activation, vaccine adjuvants), A-class (potent IFN-ɑ induction, pDC activation), C-class (combining B and A effects), and P-class ODNs (dimeric structures, enhanced NK stimulation).
- Custom Modification Integration
Our synthesis capabilities extend to over 200 chemical modifications, supporting complex designs for enhanced function, stability, and targeting, including diverse terminal and internal conjugations.
- Specialized Therapeutic Design
We possess expertise in synthesizing complex oligonucleotide architectures, such as ODNs containing advanced prodrug modifications (e.g., thermolytic protecting groups for tunable in vivo release) and specific fluorescent tags for cellular tracking and mechanistic studies.
Workflow
Project Scoping & Ligand Design
We begin by defining the project scope and designing the ligand, where we clarify the biological goals, therapeutic modality, and target specifications for the liver. This involves an initial consultation to select the oligonucleotide chemistry, the appropriate GalNAc valency, and to design the optimal linker and scaffold geometry.
Oligonucleotide Preparation
Prepare the nucleic acid payload with the necessary chemical modifications and conjugation handles. Automated solid-phase synthesis of the oligonucleotide (3' to 5' or 5' to 3'); incorporation of stability-enhancing modifications (e.g., 2'-MOE, LNA, phosphorothioate backbone); attachment of the final reactive group (e.g., 5'-hexylamino).
GalNAc Cluster Synthesis & Activation
In parallel, we synthesize, purify, and structurally characterize the custom triantennary GalNAc ligand core. We then activate this purified cluster using high-efficiency agents to prepare it for the critical coupling step.
Solution-Phase Conjugation
Next, we execute the solution-phase conjugation, where we carefully couple the activated GalNAc cluster with the functionalized oligonucleotide. We rigorously monitor this reaction to ensure exceptionally high conversion efficiency before quenching and performing an initial purification.
Purification & Quality Control (QC)
Finally, we purify the conjugate at scale using high-resolution chromatography and conduct a comprehensive suite of quality control analyses. This includes identity confirmation by mass spectrometry, purity assessment, and concentration measurement to ensure the final product meets all specifications.
Publication Data
Journal: Molecules
DOI: 10.3390/molecules22081356
Published: 2017
IF: 4.6
Results: In this study, the authors conducted a systematic comparison of two distinct strategies for synthesizing 5′-GalNAc-conjugated antisense oligonucleotides (ASOs), focusing on solid-phase and solution-phase conjugation approaches. The solid-phase method involved coupling a pre-formed THA-GalNAc phosphoramidite directly to the support-bound oligonucleotide, optimized for efficiency through parameters like temperature and recirculation time, achieving over 90% coupling yield but with slightly lower purity due to impurities like branchmers. In contrast, the solution-phase strategy entailed conjugating a purified aminohexyl-modified ASO intermediate with a THA-GalNAc pentafluorophenyl ester in aqueous buffer, resulting in higher overall yield (58% vs. 47%) and purity (97.7% vs. 96.8%), albeit with more complex steps and longer duration. The research highlighted that while the solid-phase approach offers expediency and simplicity, the solution-phase method provides superior product quality, providing valuable insights for selecting conjugation strategies in developing GalNAc-ASO therapeutics based on specific needs for scalability, purity, and efficiency.
Applications
siRNA Therapeutics for Genetic Liver Disorders
GalNAc conjugation is the established mechanism for delivering small interfering RNA (siRNA) to treat inherited metabolic diseases, successfully targeting transcripts like those involved in primary hyperoxaluria type 1 (PH1) or acute hepatic porphyria (AHP) with revolutionary clinical results.
Antisense Oligonucleotide (ASO) Programs
The service is crucial for developing ASOs aimed at reducing the production of specific disease-causing proteins synthesized by the liver, such as those implicated in cardiovascular risk (e.g., PCSK9 or ApoCIII).
Cardiovascular and Metabolic Diseases
Targeting key regulatory genes in the liver involved in lipid and cholesterol metabolism, including programs designed to silence genes responsible for hypercholesterolemia and hypertriglyceridemia, offers highly specific, long-lasting therapeutic benefits.
Hepatitis B Virus (HBV) Infection Treatment
GalNAc conjugates are central to developing next-generation treatments that target and silence the persistent HBV transcripts within the infected hepatocytes, offering a promising route to functional cure in chronic infection.
Advantages
Maximized ASGPR Binding Affinity
We utilize scientifically validated triantennary scaffolds that are structurally engineered for optimal three-point binding to the ASGPR, achieving ultra-high affinity (Kd in the low nanomolar range), which translates directly to greater in vivo potency and lower effective doses.
Proprietary Linker SAR Expertise
Our specialists possess deep knowledge in optimizing the physicochemical properties of the linker connecting the GalNAc cluster to the oligonucleotide, controlling flexibility and inter-galactose distance for maximal hepatocyte uptake efficiency.
Superior Conjugate Purity
By prioritizing the solution-phase PFP-ester conjugation strategy for scale-up, we achieve higher overall conjugate purity compared to traditional solid-phase methods, minimizing potential manufacturing contaminants for clinical applications.
Accelerated Timeline for Lead Candidates
By combining our established GalNAc cluster synthesis with optimized oligo synthesis, we drastically reduce the synthetic cycle time, allowing you to rapidly move from novel concept to fully characterized lead candidate for preclinical testing.
Frequently Asked Questions
Customer Review
We initially struggled with a proprietary GalNAc scaffold design. The CD BioGlyco team not only optimized the synthetic route but also provided crucial SAR insights, suggesting a minor linker modification that increased our in vitro potency by nearly 5-fold. This scientific partnership is exactly what a fast-moving biotech requires.
— Manager, R&D, Drug Delivery Innovations
The dual-platform synthesis option offered by CD BioGlyco was a game-changer. We used their rapid solid-phase phosphoramidite route for early screening, and then seamlessly transitioned to their high-yield solution-phase route for large-scale toxicology material. The material consistency across scales was exceptional.
— Dr. A. Sharma, Preclinical Pharmacology
Their deep knowledge of activated GalNAc clusters, particularly the PFP ester chemistry, resulted in coupling efficiencies we couldn't achieve internally. The high conversion rate and subsequent ease of purification dramatically reduced our manufacturing cost per gram for our liver-targeted siRNA therapeutic.
— Head of Chemistry, Synthetic Biology
Associated Services
To fully support your oligonucleotide therapeutic pipeline, we offer a complete suite of integrated services that complement our GalNAc platform, ensuring a single, high-quality partner for your entire project.
Therapeutic Oligonucleotide Synthesis Service
The quality of the therapeutic payload is paramount. We offer industry-leading synthesis services designed for purity and stability, which are then seamlessly integrated with our GalNAc conjugation.
Production of double-stranded RNA tailored for gene silencing, incorporating all necessary stability and thermodynamic modifications (e.g., 2'-F, 2'-OMe).
Custom synthesis of microRNA mimics and anti-miRs (antagomirs) designed for therapeutic modulation of gene expression pathways.
High-fidelity synthesis of ASO, specializing in second-generation (2'-MOE) and advanced chemistries for enhanced in vivo stability and binding affinity.
Custom synthesis and modification of single-stranded nucleic acid ligands for targeting non-hepatic proteins or cells with high specificity.
At CD BioGlyco, our GalNAc ligand design & synthesis service is the comprehensive solution for developing high-potency, liver-targeted oligonucleotide therapeutics. By merging exceptional scientific knowledge regarding ASGPR-binding principles with high-end chemical manufacturing capabilities, we deliver optimized, scalable, and high-purity GalNAc conjugates that are ready to accelerate your journey from bench to bedside. Our team of expert biologists and synthetic chemists is prepared to discuss your project's unique requirements and provide a tailored strategy to ensure your GalNAc conjugate achieves maximum therapeutic potential. Please contact us.
Reference
- Cedillo, I.; et al. Synthesis of 5′-GalNAc-conjugated oligonucleotides: a comparison of solid and solution-phase conjugation strategies. Molecules. 2017, 22(8): 1356. (Open Access)