GalNAc-siRNA Delivery Service
Overview
The clinical maturation of RNA interference (RNAi) has been significantly propelled by the development of N-acetylgalactosamine (GalNAc) conjugation, a breakthrough technology that addresses the primary hurdle of oligonucleotide therapeutics: precise tissue delivery. CD BioGlyco offers a premium GalNAc-siRNA delivery service, utilizing the high-capacity asialoglycoprotein receptor (ASGPR) pathway to achieve near-exclusive delivery of small interfering RNA (siRNA) to hepatocytes. By chemically tethering a trivalent GalNAc cluster to a stabilized siRNA duplex, our platform bypasses the systemic limitations of "naked" oligonucleotides and the potential immunogenicity of lipid nanoparticles. This "lock-and-key" approach ensures rapid receptor-mediated endocytosis, facilitating potent and durable gene silencing for a wide range of hepatic and systemic metabolic disorders.
Core Technologies
Our delivery platform is built upon three pillars of chemical and biological engineering to ensure maximal therapeutic index:
- Trivalent GalNAc Clusters
We employ a triantennary ligand design that mimics the natural substrate of the ASGPR. This trivalent configuration provides sub-nanomolar binding affinity, capitalizing on the high density of ASGPR (~1.2 million receptors per cell) to ensure rapid cargo internalization.
- Enhanced Stability Chemistry (ESC)
To protect the siRNA from nuclease-rich environments, we utilize a sophisticated modification pattern. This includes alternating 2'-O-methyl (2'-OMe) and 2'-fluoro (2'-F) ribose modifications alongside strategic phosphorothioate (PS) backbone linkages at the 5' and 3' termini.
- Advanced ESC (AD-ESC) Designs
Our next-generation designs further optimize the 2'-F/2'-OMe ratio to minimize potential long-term accumulation toxicity while enhancing the metabolic half-life. These designs can maintain therapeutic silencing for over six months from a single administration.
- Receptor Recycling Mechanics
Our conjugates are designed to dissociate from the ASGPR within the acidic environment of the early endosome. This allows the receptor to recycle back to the cell surface within minutes, enabling a continuous and high-throughput "conveyor belt" of siRNA delivery.
GalNAc-siRNA Delivery: High-Efficiency Hepatocyte Targeting and Gene Silencing
The GalNAc-siRNA delivery is a comprehensive solution designed to support the entire development lifecycle, from target validation to IND-enabling studies. We provide bespoke synthesis of GalNAc-siRNA conjugates across a wide array of scales, ranging from low-milligram amounts for initial screening to multigram batches suitable for toxicology and non-human primate (NHP) studies. Our platform is compatible with various siRNA architectures, including standard 21-mer duplexes, asymmetric siRNAs, and Dicer-substrate RNAs.
A key component of our scope is the integration of advanced chemical modifications. We offer specialized "advanced ESC" designs that optimize the spatial distribution of phosphorothioate linkages and ribose modifications to maximize potency in the liver. Furthermore, our service includes the design and synthesis of custom linkers—such as acid-labile or redox-responsive bridges- to fine-tune the release of the siRNA payload within the hepatocyte cytoplasm. We also provide extensive analytical support, including metabolic stability assays in liver S9 fractions and ASGPR-binding affinity studies, ensuring that every conjugate meets the highest standards of biological activity and specificity.
Workflow
In Silico Design & Sequence Selection
We leverage advanced bioinformatic algorithms to perform a comprehensive analysis of the target mRNA sequence, ensuring the identification of highly potent siRNA candidates. Our design process prioritizes sequences with strong RISC (RNA-induced silencing complex) loading characteristics, maximal target engagement potency, and rigorously minimized off-target potential by cross-referencing against genomic databases. This predictive screening allows for the selection of lead candidates with the highest likelihood of success in downstream in vitro and in vivo applications.
Chemical Modification Strategy
To tailor the oligonucleotide to your specific therapeutic requirements, we implement a strategic chemical modification pattern. Based on the desired duration of effect, we employ either an ESC or an advanced ESC (AD-ESC) pattern. This involves the precise incorporation of 2'-F and 2'-OMe sugar modifications, combined with phosphorothioate (PS) backbone linkages at critical positions. This tailored approach significantly enhances nuclease resistance, improves pharmacokinetic profiles, and reduces immunostimulation, thereby ensuring robust intracellular stability and sustained activity.
High-Purity Oligonucleotide Synthesis
The selected sequences are synthesized using state-of-the-art, automated solid-phase synthesizers under strict, controlled conditions. This process ensures the high-fidelity production of both the sense and antisense strands. Special attention is paid to the 3'-end of the sense strand, where specific functional groups (e.g., amino or thiol modifiers) are incorporated to serve as dedicated handles for the subsequent site-specific conjugation of the GalNAc ligand, without compromising the integrity of the antisense strand.
Site-Specific Conjugation
The trivalent GalNAc ligand, known for its high affinity to the ASGPR receptor on hepatocytes, is attached exclusively to the pre-functionalized 3'-end of the sense strand. This is achieved through a stable (e.g., non-cleavable) or bioreversible (e.g, cleavable) linker chemistry, selected based on the intended drug release mechanism. This site-specific strategy guarantees that the antisense (guide) strand remains completely unmodified and fully accessible for efficient Ago2 loading and gene silencing activity, maximizing the therapeutic effect.
Multi-Step Purification
To achieve the stringent purity standards required for therapeutic applications, we employ a multi-step chromatographic purification workflow. This typically begins with reverse-phase HPLC (RP-HPLC) to efficiently separate and remove truncated or failure sequences, followed by ion-exchange chromatography (IEX) to eliminate any unreacted ligands and closely related impurities. This rigorous process consistently yields conjugates with pharmaceutical-grade purity exceeding 98%, ensuring a highly homogeneous final product.
Comprehensive Quality Control
Every single batch of the final conjugate undergoes a comprehensive battery of analytical tests to confirm identity, purity, potency, and safety. This includes liquid chromatography-mass spectrometry (LC-MS) for exact mass verification and confirmation of sequence identity, analytical size-exclusion chromatography (SEC) to assess monodispersity and quantify high-molecular-weight aggregates, and sensitive endotoxin testing to ensure the product is safe for in vivo studies.
Publication Data
Journal: Nucleic Acids Research
DOI: 10.1093/nar/gkae350
IF: 13.1
Published: 2024
Results: In this comprehensive study, the authors systematically evaluated the oral delivery potential of GalNAc-conjugated siRNAs in both rodent and non-human primate models. Recognizing that subcutaneous injection is the current standard, they explored oral administration co-formulated with various permeation enhancers, primarily sodium caprate (C10), to overcome the significant challenges of low intestinal permeability and pre-systemic degradation. Their research demonstrated that orally delivered GalNAc-siRNAs could indeed achieve robust and durable RNAi-mediated gene silencing in the liver, targeting proteins such as Factor XII and transthyretin. However, the oral bioavailability was consistently low, calculated to be less than 2% in NHPs, despite the siRNAs showing remarkable metabolic stability in the gastrointestinal tract. Pharmacokinetic and pharmacodynamic analyses revealed that the major limiting factor was not degradation but the poor intestinal absorption of the large, rigid double-stranded siRNA molecules. By comparing molecules of different sizes, including shorter REVERSIR oligonucleotides, the authors concluded that enhancing intestinal permeability, rather than improving metabolic stability, is the critical frontier for making oral siRNA therapeutics a practical reality. This work provides a foundational assessment of the barriers and potential strategies for developing orally administered nucleic acid drugs.
Applications
Cardiovascular Disease Management
Our GalNAc-siRNA service is widely used to target PCSK9, ANGPTL3, and ApoC3, providing long-term reductions in LDL cholesterol and triglycerides for patients with atherosclerotic cardiovascular disease.
Acute Hepatic Porphyrias
By targeting the ALAS1 gene in the liver, our conjugates prevent the accumulation of neurotoxic heme precursors, effectively managing the debilitating attacks associated with this rare genetic disorder.
Primary Hyperoxaluria Type 1
We provide the delivery vehicles for siRNAs targeting HAO1, reducing the hepatic production of oxalate and preventing the progressive kidney damage and oxalosis characteristic of the disease.
Transthyretin (ATTR) Amyloidosis
Our platform facilitates the silencing of the TTR gene in hepatocytes, preventing the formation of misfolded amyloid deposits in the heart and nerves, halting disease progression.
Advantages
Hepatocyte-Specific Precision
By targeting the ASGPR, which is expressed almost exclusively on liver cells, our GalNAc-siRNA conjugates achieve a high tissue-to-plasma ratio, significantly reducing the risk of systemic side effects.
Subcutaneous Administration Convenience
The high potency and solubility of GalNAc-RNA conjugates enable low-volume subcutaneous injections, which are significantly better tolerated than the intravenous infusions required for many other delivery systems.
Bypassing the LDLR Pathway
Unlike lipid nanoparticles that depend on ApoE and the LDL receptor, GalNAc-conjugated siRNAs use the ASGPR, making them effective even in patients with LDL receptor deficiencies or familial hypercholesterolemia.
Rapid Cellular Internalization
The ASGPR is a high-flux receptor that recycles every 15 minutes. This allows a single cell to internalize millions of GalNAc-siRNA molecules daily, ensuring a robust concentration of the therapeutic payload.
Frequently Asked Questions
Customer Review
The transition from standard siRNA to CD BioGlyco's GalNAc platform was seamless. Their expertise in ESC chemistry allowed us to move our lead candidate into in vivo studies with full confidence in its stability.
— By Dr. K.M., Head of Discovery Biology
We have tried several vendors, but CD BioGlyco's trivalent ligand architecture provides the most consistent liver targeting we've seen. Their custom linker options were a major plus for our project.
— By Director, Metabolic Disease Research
The subcutaneous delivery capability of these conjugates changed the way we conduct our chronic HBV studies. The animals tolerated the injections perfectly, and the data were highly reproducible.
— By Dr. R.J., Associate Professor
Associated Services
High-affinity, liver-targeted aptamers for specialized diagnostic and therapeutic applications.
Advanced phosphorodiamidate morpholino oligomers for precise splice modulation and antisense applications.
High-purity, modified single-guide RNAs for efficient CRISPR-mediated gene editing in hepatocytes.
Engineered circular RNAs for increased stability and prolonged protein expression in liver-directed therapy.
CD BioGlyco is at the forefront of the RNAi revolution, providing the specialized delivery solutions required to turn genomic insights into life-changing therapies. Our GalNAc-siRNA delivery service combines cutting-edge chemistry with a deep understanding of liver biology to provide your projects with unmatched potency, durability, and safety. Contact us to accelerate your liver-targeted programs and achieve the precision your patients deserve.
Reference
- Yu, M.; et al. Evaluating the oral delivery of GalNAc-conjugated siRNAs in rodents and non-human primates. Nucleic Acids Research. 2024, 52(10): 5423-5437. (Open Access)