ASO/siRNA Synthesis

ASO/siRNA Synthesis

1. Background

Antisense oligonucleotides (ASOs) and small interfering RNAs (siRNAs) represent a new generation of nucleic acid therapeutics that achieve precise gene expression regulation through sequence-specific recognition of target RNAs. Compared with conventional small-molecule drugs and antibody-based therapeutics, nucleic acid medicines offer significant advantages including straightforward design, a broad targetable space, and shorter development timelines, enabling the development of treatments for targets that are otherwise inaccessible to traditional modalities. With the successful market approval of multiple ASO and siRNA drugs, nucleic acid therapeutics have emerged as a major growth area in biopharmaceutical research.

High-quality oligonucleotide synthesis forms the foundation of nucleic acid drug development. Chemical modifications—such as 2'-MOE, 2'-F, and phosphorothioate (PS) backbone—markedly enhance the nuclease stability, target-binding affinity, and pharmacokinetic performance of ASOs and siRNAs, and directly determine the drugability of candidate molecules. However, the synthesis of heavily modified oligonucleotides places stringent demands on solid-phase synthesis processes and purification technologies.

ZhuHai Generulor has established a dedicated, fully integrated ASO/siRNA service platform built on mature solid-phase synthesis expertise. Starting from the client's target gene, we offer sequence design and optimization services that screen for high-efficacy candidate sequences based on target mRNA features, modification strategy, and off-target risk assessment. Our synthesis capabilities support a wide range of chemical modification types, from small- to mid-scale custom synthesis, and every product is subject to rigorous HPLC purification and comprehensive quality testing (HPLC purity analysis / mass spectrometry confirmation) to ensure a purity of ≥90%—delivering a complete solution from sequence design to finished-product delivery for nucleic acid drug research.

Figure 1. Schematic of ASO/siRNA Chemical Modifications and Oligonucleotide Synthesis Workflow

2. Synthesis Services

2.1 Supported Modification Types

ZhuHai Generulor offers custom synthesis of ASOs and siRNAs carrying a wide variety of chemical modifications, including but not limited to:

(1) ASO 2'-MOE (2'-O-methoxyethyl) modification: classic gapmer design, widely used in clinical drug development

(2) ASO Affinity Plus®: third-generation high-affinity modification that further enhances targeting efficiency and pharmacokinetic performance

(3) ASO Custom: other modification types customized to client requirements (e.g., 2'-F, LNA, PNA, PS, etc.)

(4) siRNA Custom Synthesis: synthesis of standard siRNAs and chemically modified siRNAs

2.2 Synthesis Scales

Flexible synthesis scales are available to meet the requirements of different research stages:

(1) 5 nmol: suitable for early-stage sequence screening and in vitro validation

(2) 10 nmol: suitable for preliminary functional validation

(3) 50 nmol: suitable for in vitro cellular experiments and small-scale animal studies

(4) 200 nmol: suitable for in-depth in vitro and in vivo functional research

(5) 200 nmol (HPLC Purified): highly purified by HPLC, suited for experiments requiring elevated purity standards

3. Technical Features and Advantages

（1）Established Solid-Phase Synthesis Process

We employ standard solid-phase synthesis (SPS) technology combined with optimized coupling, oxidation, and deprotection conditions to ensure the efficient synthesis of complex, heavily modified oligonucleotides. From phosphoramidite monomer selection through final deprotection, every step is subject to strict process controls to guarantee consistent, reliable product quality.

（2）Rigorous Quality Control System

All synthesized products are purified by reverse-phase high-performance liquid chromatography (RP-HPLC) to a purity of ≥90%. A complete quality testing report is provided with each order, including: HPLC purity analysis (confirming full-length product purity and impurity profile) and mass spectrometry (MS) analysis (confirming molecular weight accuracy). HPLC Purified-grade products undergo more stringent purification conditions, making them appropriate for experiments with the highest quality requirements.

（3）Flexible Custom Services

We support client-defined sequences and modification schemes, offering synthesis services from small to large scale according to research needs. Whether for early candidate sequence screening or late-stage preclinical studies, we can supply products at the appropriate scale.

（4）Rapid Turnaround

The standard synthesis turnaround is 3–4 weeks. Without compromising quality, this significantly shortens project timelines and accelerates the research and development process.

Figure 2. Quality Control Workflow / Representative HPLC and MS Analysis

4. Service Scope and Deliverables

*Deliverables include:

(1) Synthesized product (supplied at the selected scale)

(2) Quality testing report (including HPLC purity chromatogram, mass spectrometry confirmation data, and molecular weight comparison)

(3) Product handling instructions and storage recommendations

5. Submission Requirements and Project Timeline

*Note：Clients must clearly provide the target sequence (5'→3' orientation), the required chemical modification type(s) (e.g., 2'-MOE, PS backbone, etc.), synthesis scale (5/10/50/200 nmol), and purification requirements (standard purification or HPLC Purified). For special modification needs or large-scale synthesis requirements, please contact us to discuss a customized service plan.