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Custom GalNAc-siRNA Conjugate Synthesis

Design and source GalNAc-conjugated small interfering RNA for hepatocyte-targeted RNA interference research. Explore triantennary ligand configurations, chemically stabilized siRNA duplexes, conjugation strategies and project-specific analytical characterization.

Triantennary GalNAc 2′-OMe / 2′-F Phosphorothioate (PS) Custom duplex design Analytical QC
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Overview Delivery mechanism Architectures Design explorer Design guide Chemical modifications Synthesis & QC FAQ Contact
Targeted RNA delivery · Custom synthesis to multi-gram scale

What is a GalNAc-siRNA conjugate?

GalNAc-siRNA conjugates combine a chemically modified siRNA duplex with a GalNAc targeting ligand. GalNAc binds the hepatocyte ASGPR receptor to promote liver-directed uptake; productive cytoplasmic delivery allows the guide strand to engage RISC and silence complementary mRNA.

Bio-Synthesis supports custom design through multi-gram production, including blunt-ended, overhang and asymmetric duplexes; 3′ or 5′ sense-strand GalNAc attachment; and tailored linkers, purification and QC.

Choose from 2′-OMe, 2′-F, specialty sugar/base modifications, PS, PS2, PN and terminal chemistries. Chemistry placement, RNAi activity and scale-up feasibility are reviewed for each sequence.

Flexible GalNAc attachment

Explore 3′- or 5′-sense-strand GalNAc placement, triantennary or other ligand formats, and custom spacer/linker options.

Broad modification capabilities

Discuss 2′-OMe, 2′-F, specialty sugars and bases, PS, PS2, PN and other project-specific stabilization chemistries.

Research to multi-gram production

Plan synthesis scale, purification, identity and purity analysis, duplex assessment and project-defined QC requirements.

How GalNAc delivery works

From hepatocyte recognition to RNA interference

Follow a GalNAc–siRNA conjugate through five key stages of liver-targeted delivery. Select a stage to explore the mechanism.

CELLULAR DELIVERY PATHWAY
STAGE 01 / 05

ASGPR recognition

The GalNAc ligand binds the asialoglycoprotein receptor (ASGPR) on hepatocytes, promoting liver-directed uptake.

Key biological point

GalNAc supports receptor targeting; it does not guarantee productive gene silencing.

Scientific note: This is a simplified conceptual animation. Receptors may recycle after uptake, while only a small proportion of internalized siRNA typically escapes endosomes and becomes available for RISC loading.

Conjugation formats

GalNAc ligand and siRNA architecture options

GalNAc-siRNA design begins with duplex geometry and target biology. Both blunt-ended and 3′-overhang duplexes are used in RNAi research. Ligand valency, sense-strand attachment site (3′ or 5′), linker chemistry and guide-strand compatibility should be selected together; no single architecture fits every target.

Design Typical research rationale Important consideration
Blunt-ended duplex (19–21 bp) Fully paired ends; useful for stabilized duplex research Review strand asymmetry, guide loading and terminal protection
3′-overhang duplex (e.g., 19 bp + 2-nt overhangs) Conventional siRNA architecture with short unpaired termini Specify which strand carries each overhang and any end modifications
Asymmetric / Dicer-substrate designs Specialized processing or strand-bias research Evaluate Dicer processing, conjugation placement and length
Triantennary GalNAc ligand Multivalent ASGPR-mediated hepatocyte uptake Linker, ligand geometry and attachment position matter
Mono-/biantennary GalNAc Comparative ligand-valency studies Do not assume equivalent uptake to triantennary designs

Availability of individual ligand formats, linkers and attachment strategies must be confirmed before quotation.

Interactive architecture explorer

Explore duplex geometry and conjugation choices

Compare blunt-ended and overhang duplexes before choosing ligand position, linker, and chemical modification strategy. Designs are illustrative and require sequence-specific review.

Format End structure Customer design questions
Blunt-ended No unpaired terminal nucleotides 19-, 20-, or 21-bp? Which strand and terminal linkages?
3′ overhang Typically two unpaired nucleotides at one or both 3′ termini Overhang identity, length, stabilization and conjugation site?
Advanced asymmetric Strand lengths and terminal structure vary Guide loading, processing, stability and delivery constraints?

Triantennary GalNAc at the sense-strand 3′ end

Antisense / guide Sense / passenger — 3′ tri-GalNAc

A widely studied starting point for hepatocyte-targeted siRNA research. Review strand length, 2′-OMe/2′-F pattern, terminal PS placement and linker chemistry together.

Guide-strand 5′ recognition by Ago2 should be preserved.

Stability and potency

siRNA chemical modifications for GalNAc conjugates

GalNAc-siRNA design can draw on sugar, base, backbone, and terminal modifications—not only 2′-OMe/2′-F and PS/PS2. Bio-Synthesis also works with specialty phosphoramidate (PN) linkages. Chemistry must be chosen for the specific strand, position, target and analytical requirements; advanced options are not universal substitutions.

Modification Role in design Practical consideration
2′-O-methyl (2′-OMe) Common stabilized-siRNA sugar chemistry; nuclease resistance and immune-response modulation Position-specific balance with guide loading and target activity
2′-Fluoro (2′-F) Common stabilized-siRNA sugar chemistry; duplex affinity and nuclease resistance Placement and density require activity testing
2′-O-methoxyethyl (2′-MOE) Experimental affinity and nuclease-resistance tuning Bulkier chemistry; RISC compatibility is position-dependent
LNA / BNA and cEt Constrained sugars for high-affinity experimental designs Not routine drop-in substitutions in Ago2-active duplexes
FANA, UNA and GNA Alternative sugar/backbone analogs for seed and structure–activity studies Highly placement-sensitive; functional validation needed
Phosphorothioate (PS) Terminal protection and altered protein interactions Adds phosphorus stereocenters; use selectively
Phosphorodithioate (PS2) Achiral phosphorus linkage studied for nuclease resistance and reduced stereocomplexity Experimental substitution; 2024 study reports position-dependent effects
Phosphoramidate (PN) linkages Specialty phosphorus–nitrogen backbone chemistry for stability and structure–activity research Specify the exact PN linkage type and positions; RNAi compatibility is not universally established
Stereodefined Rp/Sp PS Controlled stereochemical design Specialized chemistry and analytical review
5′ phosphate / 5′-(E)-vinylphosphonate Guide-end recognition and metabolically stabilized phosphate mimic strategies Confirm guide-strand compatibility and synthetic feasibility
Modified nucleobases: 5-methyl-C, pseudouridine, 2-thio-U, 2,6-diaminopurine Experimental base-pairing, recognition and immunological studies Not established universal GalNAc-siRNA potency improvements
Tri-GalNAc and other ligand valencies ASGPR-directed hepatocyte uptake and valency studies Sense-strand attachment, linker and valency are design variables
PEG / TEG and cleavable linkers Ligand spacing and conjugate release research Chemistry and cleavage behavior require verification

Technical note: Published STC, ESC and Advanced ESC modification strategies provide useful design principles, but specific proprietary modification maps should not be represented as a standard Bio-Synthesis formulation without authorization and validation.

Design example

Blunt-ended and 3′-overhang GalNAc-siRNA: representative architectures

Original educational comparison of two commonly studied duplex formats. The primary diagram shows a 3′ sense-strand GalNAc attachment as one common example. A 5′ sense-strand attachment is another published design option; neither placement is universally preferred. Attachment position, linker chemistry and modification positions require design-specific evaluation. This original schematic is not taken from the 2024 paper.

Example A · 3′ sense attachment

Sense  5′ ─────────── 3′—GalNAc
Guide  3′ ─────────── 5′

Representative arrangement; shown in the detailed schematic below.

Example B · 5′ sense attachment

Sense  GalNAc—5′ ─────────── 3′
Guide        3′ ─────────── 5′

Alternative attachment orientation; linker and sequence-dependent evaluation required.
Two GalNAc–siRNA duplex formatsA Blunt-ended duplex · 19 bp Sense 5′ Guide 3′ 5′ guide 3′ sense GalNAc B 3′-overhang duplex · 19 bp paired + 2-nt overhangs Sense 5′ Guide 3′ 5′ guide 3′ sense GalNAc Black = representative 2′-OMe; green = representative 2′-F; lavender = overhang; ligand schematic not to scale.

2′-OMe 2′-F Terminal PS linkage PS2: optional experimental substitution (not shown as fixed sites)

1. Select duplex architectureCompare blunt 19-mer research designs with conventional overhang-containing siRNA.
2. Define strand chemistrySpecify every 2′-OMe, 2′-F, PS and any PS2 linkage separately for each strand.
3. Confirm ligand placementThe cited 2024 study used 5′ sense-strand GalNAc; other designs may use different positions.

Scientific context: The Beauty of Symmetry (2024). Consult the primary publication and supplementary information for exact experimentally tested patterns.

Customer design resource · Literature-informed

How to design a GalNAc-siRNA conjugate

A useful GalNAc-siRNA design begins with the target transcript and an experimentally supported guide sequence—not with a universal modification recipe. The duplex geometry, 2′-OMe/2′-F map, terminal backbone chemistry, guide-strand 5′ functionality, GalNAc attachment position and analytical requirements should be reviewed together.

Design route A · Established starting point

Start with a validated guide/passenger pair, select a suitable duplex length and overhang or blunt-end format, apply a position-specific 2′-OMe/2′-F pattern, and evaluate terminal PS protection and a triantennary GalNAc linker.

This is a design framework, not a validated sequence-independent modification map.

Design route B · Advanced PS2 comparison

For a matched research series, compare terminal PS protection against selected phosphorodithioate (PS2) substitutions. Keep the guide sequence and other variables constant where feasible; assess purity, stability and biological activity independently.

PS2 building-block availability, IP considerations and synthesis feasibility require review.

Blunt-end 19-mer GalNAc-siRNA Design Example

Schöllkopf and colleagues investigated a blunt-ended 19-mer GalNAc-siRNA in which every ribose was 2′-OMe or 2′-F modified. Their baseline used two terminal PS linkages at each of the 5′ antisense, 3′ antisense and 3′ sense ends, plus PS linkages within the GalNAc cluster. In this particular study, the GalNAc cluster was assembled from the 5′ end of the sense strand; it should not be confused with the frequently discussed 3′-sense attachment format.

Design decision Evidence from the 2024 study Practical interpretation for a customer
Duplex format Blunt-ended 19-mer; all riboses modified with 2′-OMe or 2′-F Consider a 19-mer blunt-end comparator when supported by the target sequence; do not assume superiority over 21-mer formats.
5′ antisense end PS2 was poorly tolerated at this position in the tested series Preserve a compatible guide-strand 5′ architecture; do not automatically replace terminal PS with PS2 here.
3′ antisense and 3′ sense ends Selected single PS2 linkages provided stabilization comparable to two PS linkages Consider matched PS-versus-PS2 comparators, with activity and stability testing.
GalNAc cluster PS2 substitutions had generally minor or position-dependent activity effects Linker/cluster chemistry should be evaluated separately from siRNA terminal chemistry.
Analytical complexity PS2 removes the phosphorus stereocenter associated with an ordinary PS linkage Potentially simpler chromatographic characterization; actual resolution depends on the entire construct.
5′ vinylphosphonate (VP) VP was studied in combination with other modifications Advanced option for specialized comparative studies, subject to feasibility.

Important orientation distinction: The featured paper's 5′-sense GalNAc cluster is a specific architecture. Many other GalNAc-siRNA designs attach the ligand to the 3′ sense end. These are different designs; neither location should be presented as universal.

What to send for a GalNAc-siRNA design review

  • Target gene, species, transcript accession and intended assay
  • Guide and passenger sequences (5′→3′), or target region if sequence selection is needed
  • Preferred 19-mer, 21-mer or alternative duplex geometry
  • Known off-target or immunostimulation constraints
  • 2′-OMe/2′-F pattern and terminal PS/PS2 positions, if known
  • Tri-GalNAc attachment site and preferred linker
  • Desired quantity, purity, QC, controls and application
  • Whether design is literature-derived or requires IP review

Bio-Synthesis can review the requested chemical construct for quotation; in vivo potency, freedom to operate and regulatory suitability are not implied or guaranteed.

Project execution

Custom synthesis, conjugation and analytical characterization

Design Review

Confirm target sequence, strand architecture, GalNAc attachment, modification pattern, quantity and application.

Synthesis & Conjugation

Plan solid-phase synthesis, ligand attachment, strand purification and duplex preparation as appropriate.

Purification & QC

Evaluate LC-MS identity, chromatographic purity, duplex integrity and project-specific analytical criteria.

What information should be included in a quotation request?

  • Sense and antisense sequences, written 5′→3′
  • 2′-OMe / 2′-F / PS modification map, if available
  • Preferred ligand valency and conjugation site
  • Required quantity, concentration and number of constructs
  • Desired purity and analytical acceptance criteria
  • Requested counterion, formulation or delivery format
  • In vitro versus in vivo research application
  • Any required comparators, controls or documentation

Specific synthesis routes, available ligand reagents, QC methods, minimum quantities, lead times and acceptance criteria are confirmed during technical and commercial review. No GMP or clinical-use claim is implied by this page.

Research use cases

Where custom GalNAc-siRNA conjugates are investigated

Hepatocyte-targeted gene silencing

Research into RNA interference against liver-expressed transcripts using ASGPR-mediated delivery.

Structure–activity relationships

Compare ligand valency, conjugation site, linker structure and nucleotide modification patterns.

Lead optimization

Evaluate candidate duplex stability, sequence selectivity and potency across defined experimental models.

Delivery mechanism studies

Investigate uptake, intracellular trafficking and endosomal limitations in appropriate hepatocyte models.

Comparative conjugate research

Study GalNAc-conjugated siRNA alongside unconjugated controls or alternative ligand constructs.

Analytical method development

Establish identity and purity methods suitable for chemically modified siRNA conjugates.

Discuss your GalNAc-siRNA project
Scientific collaboration · Custom GalNAc-siRNA

Plan Your GalNAc-siRNA Synthesis Project

Bio-Synthesis can help review your target sequence, duplex architecture, chemical modifications, GalNAc attachment site and analytical requirements. Discuss both blunt-ended and 3′-overhang siRNA, with custom sugar, base and backbone chemistries.
Request a Quote → Discuss with a Scientist ↗

Contact Bio-Synthesis

Email: sales@biosyn.com
Phone: 800-227-0627 (US/CAN)
Phone: +1-972-420-8505 (INT)

From Sequence to Custom Conjugate

Duplex design · Ligand placement · Chemical modification · Analytical QC

01

Sequence & Feasibility Review

Send both siRNA strands, target length and intended application. Review blunt versus overhang architecture, strand orientation and GalNAc position (sense 3′ or 5′).

Duplex architecture 3′ / 5′ GalNAc Sequence review
02

Modifications & Conjugation

Discuss 2′-OMe, 2′-F and additional sugar/base chemistries; PS, PS2 or specialty PN linkages; ligand valency and custom linker selection.

Sugar & base PS / PS2 / PN Custom linker
03

Quantity, Purification & QC

Specify yield, purity, analytical acceptance criteria, delivery format and documentation. Final feasibility, methods and timeline are confirmed during quotation.

Final yield Purification Analytical QC

Please include a nucleotide-level modification map when available. All advanced chemistries and analytical specifications are subject to technical feasibility review.

Technical questions

Frequently asked questions about GalNAc-siRNA synthesis

FAQ

Can 2′-OMe, 2′-F and PS modifications be combined?
Yes. These modifications are commonly combined in stabilized siRNA designs. The precise placement should be optimized for the target sequence and intended experimental use.
Does GalNAc deliver siRNA to all cell types?
No. The established targeting rationale is ASGPR-mediated uptake in hepatocytes. Other cell types may have different receptor expression and delivery barriers.
Does receptor uptake guarantee gene silencing?
No. Endosomal escape, RISC loading, target accessibility and sequence-specific activity remain critical determinants of productive silencing.
Can you make mono- or biantennary GalNAc constructs?
Alternative ligand-valency designs can be submitted for feasibility assessment. Reagent availability, conjugation strategy and achievable specifications must be confirmed.
What purity and QC data are available?
Analytical requirements are project-specific. Identity testing by mass spectrometry, chromatographic purity and additional characterization can be discussed during quotation.
Is GalNAc-siRNA the same as GalNAc-ASO?
No. GalNAc is a delivery ligand used with different oligonucleotide modalities. siRNA typically acts through Ago2/RISC, whereas many gapmer ASOs act through RNase H1.
Can I provide my own siRNA sequence and modification map?
Yes. Include both strands, their orientation, nucleotide-level modifications, conjugation position, ligand format and requested yield for technical review.
Can you guarantee in vivo knockdown or clinical suitability?
Biological efficacy depends on the sequence, chemistry, biological model and dosing conditions; it is not guaranteed by chemical synthesis alone. Regulatory-grade production requirements must be discussed separately.
Why is triantennary GalNAc commonly used?
Multivalent GalNAc presentation supports strong ASGPR engagement. Triantennary ligand designs are widely studied, although ligand spacing and the overall conjugate architecture remain important.
Which siRNA strand is usually conjugated to GalNAc?
The sense/passenger strand is a common attachment site. Both 3′-sense and 5′-sense GalNAc architectures are described in the literature. The 3′ placement in our illustration is only an example; attachment position and linker design should be evaluated with the full duplex.
More FAQsAll FAQs
Bio-Synthesis in published research

Published Research Using Bio-Synthesis Oligonucleotides

Explore peer-reviewed studies that identify Bio-Synthesis as a source of research oligonucleotides. These publications illustrate applications of our custom synthesis services, from GalNAc-related RNA research to siRNA and antisense oligonucleotide bioanalysis.

GalNAc-related RNA mimics in metabolic research (2025)

Published in Journal of Clinical Investigation, this study investigates a conserved lncRNA motif in metabolic regulation. Its methods identify Bio-Synthesis as the supplier of RNA mimics in a study that includes GalNAc-RNA mimic experiments. Materials cited: RNA mimics; this is not presented as a conventional GalNAc-siRNA duplex citation.

Read research article

Bio-Synthesis ASO and siRNA materials in bioanalytical research (2025)

Published in ACS Omega, this study evaluates an oligonucleotide extraction approach for bioanalysis and identifies Bio-Synthesis as a supplier of the ASO and siRNA materials studied. Materials cited: ASOs and siRNAs; GalNAc conjugation is not claimed here without construct-level confirmation.

Read research article

These citations document research use of Bio-Synthesis-supplied oligonucleotides. The precise material type is stated for each study; neither citation is labeled as a verified Bio-Synthesis GalNAc-siRNA duplex publication.

Peer-reviewed reading

Scientific literature and design background

Featured design publication · 2024

The beauty of symmetry: siRNA phosphorodithioate modifications reduce stereocomplexity, ease analysis, and can improve in vivo potency

Schöllkopf S. et al. Molecular Therapy – Nucleic Acids 35(4), 102336 (2024). DOI: 10.1016/j.omtn.2024.102336.

Essential reading for design requests involving blunt-ended 19-mer GalNAc-siRNA, 2′-OMe/2′-F patterns, terminal PS versus PS2 substitutions, GalNAc-cluster chemistry and analytical stereocomplexity. The results are sequence- and position-dependent; the paper reports research designs, not a standard Bio-Synthesis formulation.

Read full publication
  1. GalNAc-siRNA Conjugates: Leading the Way for Delivery of RNAi Therapeutics. Nucleic Acid Therapeutics (2018). Review of receptor targeting, conjugate chemistry and RNAi delivery.
  2. Investigating the pharmacodynamic durability of GalNAc–siRNA conjugates. Nucleic Acids Research (2020). Explores chemistry and durability relationships.
  3. Therapeutic siRNA: state of the art. Review of therapeutic siRNA chemistry and delivery platforms.
  4. RNAi-based drug design: considerations and future directions. Discussion of guide-strand selection, trafficking and pharmacological activity.

Why Choose Bio-Synthesis

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Greetings, Researchers,

Please be advised that any information, guidelines, write-ups, and oral/video/graphic content on our website are intended solely as general guidelines.

It is the researcher's sole responsibility to conduct thorough research on the design of products intended for their experiments before submitting
their designs to Biosynthesis for production feasibility review.

Thank you for your understanding.

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