Delivery chemistry • discovery → preclinical

Oligonucleotide–Lipid Conjugation for siRNA & ASO

Site-specific lipid conjugation to tune biodistribution, uptake, and pharmacokinetics—supporting siRNA duplexes and ASO single-strands. Supported from early discovery through gram- to multi‑kilogram scale manufacturing with CMC-aligned workflows.

Sterols (Cholesterol) Fatty acids (C12–C24) PUFAs (DHA/EPA) Tocopherol (Vit E) PEG-lipids & custom Discovery → gram to multi‑kg scale

Overview

Lipid conjugation is a practical lever to tune hydrophobicity, plasma protein binding, tissue distribution, and cellular uptake for oligonucleotide therapeutics. We support lipid conjugation for siRNA duplexes and ASO single-strands, with site-specific attachment strategies selected to preserve functional regions and align with analytical verification.

Common designs include cholesterol/sterol conjugates, saturated and polyunsaturated fatty acids (e.g., DHA/EPA), tocopherol, PEG-lipid hybrids, and custom client-supplied lipids. Attachment can be engineered at the 3′ terminus, 5′ terminus, or internally (where design permits) for both siRNA and ASO programs.

siRNA: strand/position control ASO: terminal or internal (case-by-case) Client-supplied lipids supported

Quick facts

Lipid choice and linker strategy should be matched to modality, target tissue, dosing route, and stage (discovery vs preclinical).

Sterols

Cholesterol & analogs

Fatty acids

C12–C24; saturated/PUFA

Spacers
TEG/PEG tuning
Positions
3′ / 5′ / Internal placement
Scale
Discovery → multi‑kilogram
Linker Options
Stable & cleavable designs
Program-fit highlights

How we align lipid-conjugate design with manufacturing and analytics.

DesignControl
Site-specific attachment

Define position (3′/5′) and linker/spacer to preserve activity and enable clean analytical confirmation.

ScreeningOptions
Library-ready lipid choices

Compare sterols, fatty acids, and PEG-lipid hybrids across uptake and exposure readouts.

CMCScale
Analytics-aligned workflow

Track conjugation completeness, positional species, and impurity profiles to reduce rework during scale-up.

Common Lipids We Support

Representative lipid classes and examples used for conjugation to oligonucleotides (siRNA & ASO). Client-supplied lipids can be evaluated based on functional handle, purity, and compatibility.

Category Representative lipids Type / chain Typical functional rationale Common format
Sterol lipids Cholesterol (often via TEG/PEG spacer), sterol derivatives Sterol core Hydrophobic anchoring; distribution and uptake modulation 3′ or 5′
Vitamin-derived α‑Tocopherol (Vitamin E) and analogs Hydrophobic scaffold PK tuning; hydrophobic handle with spacer flexibility 3′ or 5′
Saturated fatty acids Lauric (C12), Myristic (C14), Palmitic (C16), Stearic (C18), Arachidic (C20), Behenic (C22), Lignoceric (C24) C12–C24 Simple hydrophobes; adjust protein binding and exposure 3′/5′ (linker optional)
PUFAs DHA (C22:6), EPA (C20:5), Arachidonic acid (C20:4), DGLA (C20:3), Linoleic (C18:2), α‑Linolenic (C18:3), γ‑Linolenic (C18:3) Unsaturated Explore alternative distribution behavior; exposure tuning Often 3′
Long-chain alkyl Stearyl (C18), Palmityl (C16), Lignoceryl (C24) Linear alkyl Hydrophobic anchoring; membrane association hypotheses 3′ or 5′
PEG‑lipid hybrids Chol‑TEG, fatty‑PEG, lipid‑PEG(n) constructs Spacer + hydrophobe Balance hydrophobicity/solubility; improve handling Lipid‑PEG‑Oligo
Custom / client-supplied Proprietary lipids, synthetic hydrophobes, program-specific ligands Program specific IP-driven designs and differentiated delivery hypotheses Feasibility evaluation
How to request a lipid conjugate
Provide modality (siRNA or ASO), sequence, desired lipid(s), attachment position (3′/5′/internal if applicable), spacer/linker preference (TEG/PEG length, stable vs cleavable), purity/QC requirements, and target quantity.

Attachment Formats & Design Considerations

Attachment strategy is selected to preserve function and maintain manufacturability. For siRNA duplexes, specify strand and position requirements; for ASOs, confirm terminus selection and compatibility with the intended mechanism.

3′Common
3′ terminal attachment

A common, robust format for both siRNA and ASO designs; supports linker/spacer tuning.

5′Program-specific
5′ terminal attachment

Useful when compatible with functional requirements; confirm activity impacts for modality.

InternalCase-by-case
Internal placement

Evaluated where design permits and analytical confirmation remains unambiguous.

Linkers & spacers (TEG/PEG) — why they matter
Spacer length and chemistry influence steric presentation, solubility, purification behavior, and exposure. Programs often screen spacer variants early to identify a lead design that balances potency, handling, and batch homogeneity.

Preclinical Manufacturing & CMC-Aligned Analytics

Lipid conjugates add critical quality attributes: conjugation completeness, linker integrity, positional homogeneity, and conjugate-specific impurities. We align purification and analytics to program stage to support scale-up without redesign.

PurificationResolution
Purification strategy

Resolve unconjugated oligo, partially conjugated species, and positional variants when relevant.

AnalyticsIdentity
Identity & purity confirmation

Orthogonal confirmation of conjugation and purity (e.g., LC‑MS and chromatography profiles).

StabilityHandling
Stability profiling

Assess storage and handling stability for linker and conjugate integrity to support shipping and use.

Talk to a Scientist

Tell us your modality (siRNA or ASO), target tissue/route, lipid(s) of interest (or ask us to propose options), attachment position, and linker/spacer preferences. If using a client-supplied lipid, include structure/handle and purity.

Custom lipid evaluation Position-specific attachment Analytics planning
What to include in your request
  • Oligo type (siRNA / ASO)
  • Sequence and any key modifications
  • Lipid(s) and functional handle
  • Attachment site (3′/5′/internal if applicable) + spacer
  • Purity/QC requirements and quantity target

FAQ

Can you conjugate lipids to both siRNA and ASO?

Yes. We support lipid conjugation for siRNA duplexes and ASO single-stranded oligonucleotides with program-appropriate attachment strategies.

Is cholesterol a lipid?

Yes. Cholesterol is a sterol, which is a major class of lipids commonly used as a hydrophobic conjugation motif.

Can you use client-supplied lipids?

Often yes. Provide the lipid structure or catalog number, functional handle, purity, and any constraints; we will assess compatibility and propose an attachment method.

What positions are available for attachment?

Most programs use 3′ or 5′ terminal attachment. Internal placement can be evaluated when compatible with the modality and analytical strategy.

Recommended Reading

Suggested starting points on oligonucleotide delivery and conjugate strategies (siRNA and ASO).

  1. Dowdy SF. Overcoming cellular barriers for RNA therapeutics. Nat Biotechnol. 2017;35:222–229.
  2. Springer AD, Dowdy SF. GalNAc‑siRNA conjugates: leading the way for delivery of RNAi therapeutics. Nucleic Acid Ther. 2018;28:109–118.
  3. Nair JK, et al. Multivalent N‑acetylgalactosamine‑conjugated siRNA localizes in hepatocytes and produces robust RNAi‑mediated gene silencing. J Am Chem Soc. 2014;136:16958–16961.

Citations can be added inline depending on how you want to attribute claims.

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