Lipids for Muscle RNA Delivery

iL-19 is an aminoethoxy-functionalized ionizable lipid with a triamine scaffold, two ester linkages and four doubly branched hydrophobic tails. It was identified as the overall lead for circular RNA delivery in a 2026 JACS study. With circRNA encoding firefly luciferase, iL-19 LNPs produced approximately 28-fold higher expression than the SM-102 benchmark in C2C12 cells and approximately 2.5-fold higher expression after intramuscular administration in BALB/c mice under the reported conditions. The reported circRNA formulation uses iL-19, DSPC, cholesterol and DMG-PEG2000 at 50:10:38.5:1.5 mol%. It supports preclinical investigation of circular RNA delivery to muscle; comprehensive safety and immunogenicity evaluation remains outstanding.

CL15F 7-5 is a piperidine-based ionizable lipid from the CL15F library, characterized by a symmetrically branched tail structure with a 7-carbon main chain and a 5-carbon side chain. This moderate tail length positions it between short-tail (e.g., CL15F 6-4) and long-tail (e.g., CL15F 14-12) variants, granting it a unique balance in mRNA delivery properties. Its LNPs exhibit optimized organ selectivity, enabling significant mRNA expression in both the spleen and muscle, as demonstrated by in vivo luciferase assays following intravenous and intramuscular administration. This lipid structure facilitates a favorable DSPC surface density on LNPs, which moderates interactions with serum proteins like ApoE, thereby reducing rapid hepatic clearance and promoting extrahepatic delivery. In vaccine applications, CL15F 7-5 LNPs encapsulating SARS-CoV-2 RBD mRNA elicited robust anti-RBD IgG titers and neutralizing antibodies in mice, outperforming the clinically benchmarked SM-102 lipid. The piperidine headgroup further contributes to storage stability by minimizing the generation of aldehyde impurities that can form mRNA-lipid adducts. Consequently, CL15F 7-5 represents a versatile lipid for developing stable, spleen-targeted mRNA vaccines and therapeutics, leveraging tail-length engineering for enhanced efficacy without complex formulation changes.

AMG-1541 is a degradable cyclic amino alcohol ionizable lipid optimized for mRNA vaccine delivery using lipid nanoparticles (LNPs). Formulated typically with DOPE, cholesterol, and PEG-lipids, AMG 1541 LNPs have a diameter of ~85 nm, PDI of 0.107, and encapsulation efficiency of 67%, ensuring stability and efficient mRNA delivery. In vitro, it outperforms benchmarks like SM-102, showing enhanced transfection in cells such as C2C12 and PBMCs. In vivo, intramuscular administration in mice results in robust protein expression within 6 hours and induces potent immune responses, including high antibody titers and Th1-biased T-cell activation, with minimal inflammation. Mechanistically, its β-hydroxyl groups form hydrogen bonds with mRNA phosphate backbones, facilitating endosomal escape. AMG1541 degrades rapidly under enzymatic conditions, reducing long-term toxicity, and is effective for vaccines targeting pathogens like influenza and SARS-CoV-2, making it a promising candidate for clinical applications.

D-Lin-MC3-DMA(MC3) is the most potent cationic lipid that has been synthesized for Lipid nanoparticles (LNPs) to deliver the siRNA.

ALC-0315 is an ionisable aminolipid that used for mRNA compaction and aids mRNA cellular delivery. ALC-0315 can be used to form lipid nanoparticle (LNP) delivery vehicles.

SM-102 is an ionizable amino lipid that has been used in combination with other lipids in the formation of lipid nanoparticles.Administration of luciferase mRNA in SM-102-containing lipid nanoparticles induces hepatic luciferase expression in mice. Formulations containing SM-102 have been used in the development of lipid nanoparticles for delivery of mRNA-based vaccines.

TCL053 is a three-tail ionizable lipid studied for local delivery of mRNA and separately encapsulated guide RNA to skeletal muscle in mice. The findings concern the specified research formulation and are not performance specifications for the supplied neat lipid.

Iso-A11B5C1 is an ionizable lipid. The iso-A11B5C1 LNP demonstrates a high level of muscle-specific mRNA delivery efficiency. exhibiting transfection efficiency comparable to the commercially available lipid SM-102, while considerably reducing inadvertent mRNA expression in main organs such as the liver and spleen.Additionally, study results show that intramuscular administration of mRNA formulated with iso-A11B5C1 LNP caused potent cellular immune responses, even with limited expression observed in lymph nodes.

CS22021 is a novel, synthetically engineered ionizable sterol lipid (ISL) developed by CanSino, specifically designed for advanced mRNA delivery via lipid nanoparticles (LNPs). Its core innovation lies in its unique molecular architecture, which integrates a cholesterol moiety directly conjugated to a branched aliphatic tail (derived from ALC-0315) and a hydrophilic headgroup containing tertiary amines. This bifunctional design allows CS22021 to simultaneously fulfill the roles of both the ionizable lipid (for mRNA binding/encapsulation and endosomal escape) and the structural cholesterol component within LNPs. Consequently, CS22021 enables the formulation of highly efficient three-component LNPs (ISL-3C-LNPs), eliminating the need for free cholesterol, using only itself, the phospholipid DOPE (crucial for forming stable, uniform nanoparticles without defects), and a PEGylated lipid. When formulated into LNPs and administered intramuscularly, CS22021 demonstrates a critical property: it achieves localized mRNA expression predominantly at the injection site, significantly minimizing off-target delivery (especially to the liver/spleen) and associated systemic toxicity. Furthermore, mRNA vaccines delivered by CS22021-based LNPs elicit robust and balanced immune responses, including strong antigen-specific IgG antibodies and, notably, a significantly enhanced CD8+ T cell response compared to conventional four-component LNPs. This combination of efficient mRNA encapsulation/delivery, localized expression for improved safety, and potent induction of cellular immunity, particularly CD8+ T cells, positions CS22021 as a highly promising lipid platform, especially for next-generation mRNA vaccine applications like cancer immunotherapy.

HY-501​​ is a next-generation cationically ionizable lipid engineered for high-efficiency RNA delivery developed by Biontech. Formulated at ​​40–50 mol%​​ in lipid nanoparticles (LNPs) alongside DSPC, cholesterol, and polysarcosine-conjugated lipid ​​C14pSar23​​, HY-501 yields uniform, stable particles (80–100 nm) with >90% RNA encapsulation. It demonstrates ​​superior in vivo performance​​: driving 2-fold higher protein expression than benchmark lipids (EA-405/HY-405) in muscle tissue, minimizing off-target liver accumulation, and reducing immunogenic risks (near-zero complement activation and <5% hemolysis). Preclinically, HY-501-based LNPs encoding SARS-CoV-2 spike protein elicit potent neutralizing antibodies and T-cell responses, underscoring its utility in precision vaccines. Its combination of scalable synthesis, exceptional transfection efficiency, and biosafety establishes HY-501 as a transformative vector for therapeutic RNA delivery.

Lipid OC7, as described in the patent WO2022207938A1, is a novel ionizable lipid that serves as the core functional component of the saNppa-LNP delivery system. Its key innovation lies in its unique biodegradable structure featuring an internal ester bond. Under typical physiological conditions, this bond hydrolyzes, triggering a charge shift from a cationic form that complexes nucleic acids to a zwitterionic form that releases them. This property is central to its role in enabling long-acting self-amplifying RNA (saRNA) therapies. Specifically, OC7 facilitates immune stealth by mitigating early interferon responses, supports sustained and efficient intracellular replication of saRNA even at low doses, and enables therapeutic protein expression that persists for over 28 days from a single administration. This combination of efficient delivery, controlled release, and extended duration of action makes OC7-based LNPs a promising platform for long-term treatments, such as for myocardial infarction, as demonstrated in the referenced research.

A33-D268 is an ionizable lipid derived from a 2-aminoimidazole (AM) core, featuring an asymmetric hydrophobic tail structure designed to optimize mRNA interactions. Selected as the top candidate from a 21-lipid library through molecular dynamics (MD) simulations, it demonstrated superior performance: low root mean square deviation (RMSD) and the smallest radius of gyration (Rg), indicating tight mRNA compaction, alongside moderate electrostatic energy and above-average hydrogen bonding for stable encapsulation. Formulated into LNPs, it achieves ​​efficient muscle-specific transfection​​ post-intramuscular injection, rivaling commercial ALC-0315 LNPs. Crucially, it exhibits ​​29-fold lower hepatic off-target expression​​, attributed to its inability to leverage serum protein coronas for liver tropism.