Antibody-siRNA Conjugates Introduction
Antibody-small interfering RNA (siRNA) conjugates (ARCs) represent an innovative class of biomolecules merging the specificity of antibodies with the gene-targeting capabilities of siRNA. This strategy aims to exploit the precise targeting of antibodies and the gene-silencing properties of siRNA to deliver therapeutic payloads to specific cell types or subcellular compartments, thereby suppressing the expression of target genes. By combining these two elements, ARCs overcome the limitations of poor siRNA targeting and short in vivo circulation time, offering a promising solution for targeted gene silencing and improved therapeutic efficacy.
The structure of an ARC is a tripartite marvel:
The Antibody
Serves as the targeting moiety
The siRNA
Acts as the effector moiety
The Linker
A critical component that covalently connects the antibody and siRNA
Our Platform Advantages and Highlights
-3.webp)
Proprietary Linker Portfolio
- Description: We have developed a proprietary portfolio of highly stable and efficiently cleavable linkers, including novel pH-responsive and reduction-responsive linkers optimized to facilitate endosome escape and cytoplasmic release.
- Function: Addresses common bottlenecks in ARC development by ensuring precise release of siRNA in target cells.
-4.webp)
High-Throughput Screening (HTS)
- Description: Our platform enables simultaneous synthesis and preliminary screening of multiple ARC drug candidates with different DAR, linker, and siRNA modifications.
- Function: Rapidly identifies lead compounds achieving optimal balance in stability, target affinity, and potency.
-5.webp)
Comprehensive Analytical Equipment
- Description: We possess advanced instrumentation for comprehensive characterization, including SEC-MALS for precise determination of molecular weight and aggregation state.
- Function: Crucial for ensuring production quality and consistency of ARCs.
ARCs Synthesis Service
The ARC system consists of three main components: antibody, siRNA, and linker. A key technology in ARC development lies in the successful conjugation of the antibody and siRNA. Creative Biolabs has developed several methods for conjugating siRNA to antibodies, including non-covalent interactions or covalent binding to lysine or cysteine residues in the antibody structure. This innovative approach holds promise for treating a variety of diseases by leveraging the specificity of antibodies and the gene-silencing capabilities of siRNA.
-6.webp)
Non-covalent Conjugation
Non-covalent conjugation is the process of assembling ARC through electrostatic non-covalent interactions, typically achieved by binding protamine and nonarginine to form a stable complex.
-7.webp)
Thiol and Maleimide-Based Conjugation
This conjugation uses an N-succinimide-based S-acetylsioacetate (SATA) reagent to chemically conjugate siRNA to cysteine residues introduced from IgG antibodies via a thiol-maleimide reaction.
-8.webp)
CPP-based Conjugation
To address the low intracellular uptake efficiency of siRNA due to its negative charge, cationic components such as CPPs can be used to neutralize the charge of siRNA, thereby promoting its intracellular delivery and enhancing its escape from endosomes.
-9.webp)
Fab-based Conjugation
Fab-based conjugation is the chemical conjugation of siRNA to the C-terminus of an antigen-binding fragment (Fab). Fab lacks an Fc domain and offers several significant advantages compared to full-length monoclonal antibodies (mAbs), including stronger tissue penetration, higher tolerability, and lower likelihood of immune system activation.
Antibody-siRNA Conjugation Methods
The coupling method determines the homogeneity, stability, and in vivo performance of the final product. We employ a state-of-the-art strategy:
| Conjugation Strategy | Description | Key Advantage |
|---|---|---|
| Site-Specific Cysteine Conjugation | Utilizing reduced interchain cysteines or engineered thiols on the antibody for conjugation with maleimide-functionalized siRNA. | Excellent DAR control (typically 2 or 4); homogenous product. |
| Enzymatic Conjugation (e.g., Sortase-mediated) | Using enzymes to ligate the siRNA-linker onto a specific recognition sequence engineered into the antibody's Fc or Fab region. | Highly selective and residue-specific; preserves antigen-binding site. |
| Amine (Lysine) Conjugation | Non-selective coupling via primary amines on lysine residues. | Historically common; simple chemistry. |
| Click Chemistry (Strain-Promoted Azide-Alkyne Cycloaddition) | Bioorthogonal reaction between a modified antibody and a modified siRNA (e.g., Azide-siRNA and Alkyne-Antibody). | High efficiency and minimal side reactions; suitable for complex structures. |
Applications of Antibody-siRNA Conjugates
Gene silencing agents (ARCs) have shown broad application prospects in the treatment of a variety of diseases, including breast cancer, prostate cancer, colon cancer, multiple myeloma (MM), HIV, and leukemia. By utilizing the cell-penetrating ability of CPP, the released siRNA-CPP can efficiently penetrate target cells, thus significantly improving gene silencing efficiency in both in vitro and in vivo experiments.
Following intravenous injection, the modified ARCs achieved a significant 66.7% reduction in EGFP (enhanced green fluorescent protein) expression in a mouse tumor model, demonstrating their safe and efficient delivery capability. These advances herald a new era in disease treatment, and ARCs are expected to meet the treatment needs of a variety of intractable diseases.
ASC's Scientific Mechanism: From Targeted Recognition to RISC Activation
A. Target Selection and Receptor-Mediated Endocytosis (RME)
An ideal ASC target must meet the following biological criteria:
- • High expression on the surface of target pathological cells and low expression on normal cells to ensure drug precision.
- • The target antigen must be a receptor capable of rapid and efficient internalization via receptor-mediated endocytosis (RME).
B.The Key Role of Linkers
The linkers used in ASC design must be "environmentally responsive," meaning they can specifically cleave and release siRNA after entering the endosome. Key escape strategies and supporting evidence include:
- • pH-sensitive linkers
- • Enzyme-cleaved linkers
C. The Final Completion of Gene Silencing
Successfully released siRNA into the cytosol is rapidly loaded into the RNA-Induced Silencing Complex (RISC), the effector molecule of the RNAi mechanism.
- • RISC Loading
- • Target Recognition and Binding
- • Gene Knockdown
Results Delivery
We provide a comprehensive final report package containing the following:
Customer Review
-1.webp)
Dr. T. Chen
Chief Scientific Officer
"Creative Biolabs completed our anti-PD-L1-siRNA conjugate project with exceptional scientific rigor. Their site-specific conjugation chemistry yielded a homogeneous DAR 2 product that significantly improved the therapeutic index in our mouse tumor models compared to previous non-site-specific batches. Detailed qPCR and KD reports were crucial to our preclinical IND application."
-2.webp)
Professor A. Sharma
Principal Investigator
"The team’s expertise in siRNA chemical modification is invaluable. They designed and synthesized a novel 2'-O-methyl-modified siRNA payload and successfully conjugated it to our proprietary antibody fragment. The resulting ARC exhibited excellent nuclease resistance and a 3-fold increase in gene knockdown efficiency in primary cells. Their data quality is unparalleled."
Frequently Asked Questions
From design to delivery of validated in vitro data, a typical project cycle is 3 to 6 months, depending on the complexity of the antibody and the validation assays required.
Absolutely. We are very flexible. You can provide one or two components, or we can procure/modify them according to your specific requirements.
We carefully design the conjugation sites and linker lengths to avoid steric hindrance affecting the interaction between siRNA and RISC. Furthermore, we rigorously perform functional validation (gene knockdown assays), which is an integral step in our workflow.
While lipid nanoparticles (LNPs) are well-suited for liver delivery, active targeting vectors (ARCs) enable precise extrahepatic targeting. They avoid the high accumulation and potential immunogenicity of certain LNPs in the liver, thus enabling the treatment of non-hepatic diseases with greater safety.
Yes. We offer siRNA design services, using proprietary algorithms to identify the most effective and selective target sequences, minimizing off-target effects and avoiding known immune-stimulating motifs. This is often the first step in the successful development of ARC projects.
Connect with Us Anytime!
Creative Biolabs possesses industry-leading site-specific conjugation technology, a comprehensive siRNA modification library, and rigorous QC/PK/PD assessment capabilities. We invite pharmaceutical companies and academic researchers worldwide to contact us and utilize our expert ASC service platform to translate the potential of gene silencing into the next generation of revolutionary therapeutic solutions.
Our customer service representatives are available 24 hours a day!
Tell us about your project, and our experts will get back to you with a customized quote and proposal.
