Harnessing the Loop: The Perspective of Circular RNA in Modern Therapeutics
Abstract
1. Introduction
2. Characteristics of circRNA Therapeutics
2.1. Fundamental Properties of circRNA
2.2. Stability and Degradation Mechanisms of circRNA
2.3. Immune Responses to circRNA
- (1)
- Sequence and structure: dsRNA regions, GU/U-rich motifs, and imperfect circularization enhance immunogenicity.
- (2)
- Cellular context: Immune cell type (e.g., dendritic cells vs. epithelial cells), subcellular localization, and RNA abundance dictate response magnitude.
- (3)
- Delivery method: Exogenous circRNAs (e.g., synthetic or encapsulated) are more immunogenic than endogenous circRNAs. When circRNAs enter cells (e.g., via exogenous delivery or endogenous release), they can activate immune pathways through multiple mechanisms.
2.3.1. Recognition by Cytosolic Immune Sensors
2.3.2. Endosomal Toll-like Receptor (TLR) Activation
2.3.3. Inflammasome Activation
2.3.4. Adaptive Immune Responses
2.3.5. Immune Evasion Strategies
- (1)
- (2)
- Masking immunostimulatory motifs: Perfectly circularized RNAs lack free ends, reducing RIG-I recognition [56].
2.3.6. Immune Activation as Adjuvants
2.4. Synthesis Strategies, Quality Control, and Delivery Methods of circRNA Vaccines
3. Sequence Design and Optimization Strategies for circRNA Therapeutics
3.1. Optimization of Open Reading Frame Sequences
3.1.1. Codon Usage Bias (CUB) and Optimization
- (1)
- Quantum computing optimizes GC content and minimizes nucleotide repeats.
- (2)
- (3)
- RNNs, including bidirectional LSTM architectures, learn codon usage patterns to recommend optimal codon substitutions (e.g., the ICOR tool for E. coli) [79].
- (4)
- Mixed-integer linear programming balances codon selection with secondary structure constraints [80].
3.1.2. Integrated Algorithmic Platforms
3.2. Selection and Optimization of IRESes
3.2.1. IRES Databases and Resource Platforms
3.2.2. Design Considerations for IRES-ORF Integration
3.3. Optimization Strategies for Group I or II INTRONS and Other Components to Enhance Splicing Efficiency
3.3.1. Design and Optimization of Intronic Ribozymes with High Circularization Efficiency
3.3.2. Optimization of Spacer Sequences in the PIE System
3.3.3. Design and Matching of Homology Arms in the CirCode System
3.4. Design Strategies to Enhance the Stability of circRNA
- (1)
- Avoid incorporating degradation signals, such as specific nucleotide sequences or secondary structures.
- (2)
- Avoid introducing high burden of methylation (e.g., m6A) or other chemical modifications to initiate circRNA degradation.
- (3)
- Engineer hairpin structures or protein-binding motifs into circRNA to generate steric hindrance, thereby blocking degradation by enzymes that could cleave circRNA (e.g., DIS3).
4. Artificial Intelligence (AI) in Advancing circRNA Vaccines
4.1. The Rational Design
4.2. Model Construction and Databases
4.3. Manufacturing
4.4. Clinical Translation
5. Recent Advances in circRNA Therapeutics
5.1. CircRNA Vaccines for Viral Infectious Diseases
5.1.1. SARS-CoV-2 and Variants
5.1.2. Monkeypox Virus (MPXV)
5.1.3. Zika Virus (ZIKV)
5.1.4. Rabies Virus
5.1.5. Influenza Virus
5.2. CircRNA Vaccines for Cancer Therapy
5.2.1. High-Efficiency Vaccine Platforms Inducing Antitumor Immune Responses
5.2.2. Targeting the Immunosuppressive Tumor Microenvironment
5.2.3. Tumor-Specific circRNAs as Neoantigen Sources
5.2.4. Synergistic Combination Therapies
5.3. CircRNA Therapeutics for Autoimmune and Metabolic Disorders
5.4. Advances in Other Protein Replacement Therapies via circRNA-Encoded Functional Proteins
6. Clinical Trials of circRNA-Based Therapeutics
7. Conclusions and Perspective
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Vaccine Type | Profile | Advantages | Disadvantages |
---|---|---|---|
Inactivated | Pathogen inactivated in entirety |
|
|
Live-attenuated | Live pathogen with attenuated virulence |
|
|
Subunit | Specific pathogen components (protein/polysaccharide/VLP) |
|
|
Viral Vector | Antigen gene delivered via harmless viral vector |
|
|
DNA | Antigen gene inserted into plasmid DNA vector |
|
|
mRNA | Antigen-encoding mRNA encapsulated in lipid nanoparticles |
|
|
circRNA | Synthetic circRNA encapsulated in lipid nanoparticles |
|
|
CircRNA | Expressed Protein | Disease/Pathogen | Application Field | Mechanism/Function | Reference |
---|---|---|---|---|---|
circRNA RBD-Delta | Spike trimeric RBD (Delta/Omicron) | COVID-19 | Vaccine prevention | Induces neutralizing antibodies and Th1-skewed cellular immunity, providing broad-spectrum protection against variants | [115] |
circRNA VFLIP-X | VFLIP-X spike protein (K417N mutations) | SARS-CoV-2 variants | Vaccine prevention | Elicits broad neutralizing antibodies and balanced Th1/Th2 responses against multiple VOCs/VOIs | [116] |
circFAM53B | Cryptic peptides (ALFRLTNRA/RTAHYGTGR) | Breast cancer, melanoma | Universal cancer vaccine | Encodes tumor-specific antigens (TSAs) via HLA-I/II dual presentation, activating CD8+/CD4+ T cells | [117] |
circRNA EDIII-Fc + NS1 | EDIII-Fc and NS1 proteins | Zika virus | Vaccine prevention | Induces neutralizing antibodies and germinal center (GC) reactions, avoiding DENV ADE effect with single-dose efficacy | [107] |
circRNA-G | Rabies virus glycoprotein G (RABV-G) | Rabies | Vaccine prevention | Enhances humoral immunity (high IgG/neutralizing antibodies) and lymph node-targeted delivery for prolonged antigen expression | [118] |
circRNA-NA (N1/N2/IBV) | Neuraminidase (N1, N2, influenza B) | Influenza | Vaccine prevention | Induces broad neutralizing antibodies and Th1-skewed immunity against H1N1/H3N2/Victoria/Yamagata strains | [106] |
cirA29L/cirA35R/cirB6R/cirM1R | A29L, A35R, B6R, M1R proteins | Monkeypox | Vaccine prevention | Elicits neutralizing antibodies and T cell responses via multivalent antigens, reducing tissue viral load | [105] |
H19-IRP | H19-IRP (protein encoded by lncRNA) | Glioblastoma | Cancer immunotherapy | Activates CCL2/Galectin-9 transcription to recruit MDSCs/TAMs; triggers T cell responses as a TAA | [119] |
circRNA-PTPN2 | PTPN2 (neoantigen) | Hepatocellular carcinoma | Neoantigen vaccine | Activates DC maturation and T cell responses via circRNA-LNP delivery, enhancing tumor cell targeting | [108] |
circRAPGEF5, circMYH9 | Tumor-specific cryptic peptides | Colorectal cancer | Liquid biopsy-driven therapy | Presented via HLA-A*11:01, inducing T cell-mediated tumor organoid clearance | [120] |
circRNA-LNP | SIIINFEKL (OVA antigen) | Lung cancer | Mucosal immunotherapy | Enhances antigen-specific T cell responses via cDC1s and alveolar macrophages, reducing systemic toxicity | [121] |
circRNA-FS (FAPα/survivin) | FAPα, survivin | Pancreatic cancer | Chemo-immunotherapy combination | Enhances DC vaccine antigen expression, induces ICD, synergizes with gemcitabine to suppress Tregs | [122] |
Small circRNA (<300 nt) (e.g., circRNA-SIINFEKL) | Peptide antigens (e.g., SIINFEKL) | Low-immunogenic tumors (e.g., melanoma) | Long-term immune memory induction | High stability (half-life > 7 days), low PKR activation, synergizes with immune checkpoint inhibitors | [59] |
circRNA SCAR | - | Non-alcoholic steatohepatitis | Metabolic disease/Liver disease | Binds ATP5B and inhibits mitochondrial permeability transition pore (mPTP) opening, reduces mitochondrial ROS output, alleviates fibroblast activation and inflammation | [35] |
circPOLR2A (EPIC) | - | Psoriasis | Immune modulation/inflammation control | Stabilizes PKR binding to inhibit its activity, attenuates IFN-α signaling and dsRNA-mediated inflammatory responses | [123] |
circ-Snhg11 | - | Diabetes mellitus | Wound healing | Inhibits hyperglycemia-induced endothelial damage via miR-144-3p/HIF-1α axis, induces M2-like macrophage polarization | [124] |
circ-Snhg11 | - | Diabetes mellitus | Diabetic wound healing | Enhances SLC7A11/GPX4-mediated anti-ferroptosis signaling through miR-144-3p sponge effect, promotes angiogenesis | [125] |
circ-Snhg11 | - | Diabetes mellitus | Angiogenesis | Activates miR-144-3p/NFE2L2/HIF1α pathway to suppress oxidative stress and improve endothelial function with vascular regeneration | [126] |
circ-IGF1R | - | Diabetes mellitus | Diabetic foot ulcer | Upregulates HK2 and VEGFA expression via miR-503-5p sponge adsorption, enhances angiogenesis while reducing apoptosis | [127] |
circCDK13 | - | Diabetes mellitus | Wound healing/regenerative medicine | Interacts with IGF2BP3 in m6A-dependent manner to enhance CD44 and c-MYC expression, promoting cutaneous cell proliferation/migration | [128] |
VEGF-A circRNA | VEGF-A | Diabetes mellitus | Diabetic foot ulcer | Achieves sustained VEGF-A protein expression via lipid nanoparticle delivery to promote angiogenesis | [113] |
IL-12 circRNA | IL-12 | Lung cancer | Immunotherapy | Delivers circRNA-encoded IL-12 through H1L1A1B3 LNPs, activates immune response, increases CD8+ T cell infiltration, inhibits tumor growth | [113] |
circSEMA4B | SEMA4B-211aa | Breast cancer | Cancer therapy | Encodes SEMA4B-211aa to suppress PI3K/AKT pathway via miR-330-3p/PDCD4 axis-mediated inhibition of AKT phosphorylation | [129] |
Study Title | Year | Location | Sponsor | Study Status | Study ID | Data From |
---|---|---|---|---|---|---|
A Study to Evealuate Safety and Immunogenicity of TI-0010 SARS-CoV-2 Vaccine in Healthy Adults | 2023 | China | National Drug Clinical Trial Institute of the Second Affiliated Hospital of Bengbu Medical College | RECRUITING | NCT06205524 | clinicaltrials.gov |
A Single Arm Clinical Study of Dendritic Cell Vaccine Loaded With CircRNA Encoding Cryptic Peptide for Patients With HER2-negative Advanced Breast Cancer | 2024 | China | Sun Yat-Sen Memorial Hospital of Sun Yat-Sen University | NOT_YET_RECRUITING | NCT06530082 | clinicaltrials.gov |
First-in-Human Pilot Study of Epicardial CircRNA-HM2002 Injection in CABG for Ischemic Heart Failure | 2024 | China | Ruijin Hospital | ACTIVE_NOT_RECRUITING | NCT06621576 | clinicaltrials.gov |
HM2002 Injection | 2025 | China | Shanghai CirCode Biomed Co., Ltd, Shanghai, China. | UNKONW | CXSL2400740 | Center for Drug Evaluation of NMPA |
Study of CircRNA Treatment in Patients with Radiation Induced Xerostomia-1 (RXRG001) | 2025 | China | RiboX Therapeutics Ltd, Shanghai, China. | RECRUITING | NCT06714253 | clinicaltrials.gov |
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Share and Cite
Zhao, Y.-Y.; Zhu, F.-M.; Zhang, Y.-J.; Wei, H.Y. Harnessing the Loop: The Perspective of Circular RNA in Modern Therapeutics. Vaccines 2025, 13, 821. https://doi.org/10.3390/vaccines13080821
Zhao Y-Y, Zhu F-M, Zhang Y-J, Wei HY. Harnessing the Loop: The Perspective of Circular RNA in Modern Therapeutics. Vaccines. 2025; 13(8):821. https://doi.org/10.3390/vaccines13080821
Chicago/Turabian StyleZhao, Yang-Yang, Fu-Ming Zhu, Yong-Juan Zhang, and Huanhuan Y. Wei. 2025. "Harnessing the Loop: The Perspective of Circular RNA in Modern Therapeutics" Vaccines 13, no. 8: 821. https://doi.org/10.3390/vaccines13080821
APA StyleZhao, Y.-Y., Zhu, F.-M., Zhang, Y.-J., & Wei, H. Y. (2025). Harnessing the Loop: The Perspective of Circular RNA in Modern Therapeutics. Vaccines, 13(8), 821. https://doi.org/10.3390/vaccines13080821