503O8,12​​ is an ionizable lipidoid synthesized via Michael addition, combining a hydrophilic amine headgroup ("503" series) with two hydrophobic branched acrylate tails (C8 and C12 chains, likely with unsaturated bonds). Its design emphasizes organ-specific delivery, exhibiting ​​spleen-tropic targeting​​ in vivo.

C14-4 (C14-494,Lipid B-4,Lipid B4) is a novel ionizable lipid with the highest T-cell transfection efficiency and low cytotoxicity.The C14-4 ionizable lipid has been explored for CAR-T therapy.To screen the excellent formulations for mRNA delivery, a lipid library of 24 ionizable lipids was constructed to make iLNPs, which were used to deliver luciferase mRNA into Jurkat cells.[115] The optimal iLNPs formulation was C14-4 iLNPs (C14-4 ionizable lipid, DOPE, chol, and PEG at a molar ratio of 35%, 16%, 46.5%, and 2.5%) (Figure 6c). The optimal dose of luciferase mRNA for C14-4 iLNPs was 30 ng. Compared with electroporated CAR T cells, the CAR T cells engineered via C14-4 iLNPs showed potent cancer-killing activity when they were cocultured with Nalm-6 acute lymphoblastic leukemia cells. To obtain a safer and more effective CAR mRNA delivery vehicle, the orthogonal design provided 256 potential formulations, and 16 representative iLNPs formulations were evaluated.Through evaluating the safety, delivery efficiency, and transfection efficiency of 16 iLNPs, the formulation B10 (C14-4 ionizable lipid, DOPE, chol, PEG at a molar ratio of 40%, 30%, 25%, and 2.5%) was screened out as the optimal performing formulation. The luciferase expression based on B10 formulation was increased threefold than the initial formulation. Reducing the accumulation and clearance of iLNPs in the liver can increase the expression of CAR mRNA in T cells, further improving the therapeutic effect of CAR-T. Studies have shown that cholesterol analogs can alter the mechanisms of intracellular circulation and enhance the delivery of mRNA, which may be related to the reduced recognition of iLNPs by the Niemann Pick C1 (NPC1) enzyme.The addition of a hydroxyl group to various locations in the cholesterol molecule can alter the binding kinetics between the modified cholesterol and NPC1, and reduced NPC1 recognition of cholesterol. The results showed that replacement of 25% and 50% 7 α-hydroxycholesterol for cholesterol in iLNPs improved mRNA delivery to primary human T cells in vitro by 1.8-fold and twofold, respectively.C14-4 is one of the ionizable lipids to efficiently deliver mRNA to Jurkat cells or primary human T cells. It will effectively promote the development of mRNA delivery by iLNPs for CAR-T therapy.

Lipid88​​ is a high-performance, novel ionizable lipid component engineered for advanced mRNA-LNP vaccine delivery. LNP88 formulation demonstrates superior biodistribution, achieving >10-fold higher transfection efficiency in spleen and lymph nodes compared to benchmark lipids like ALC-0315 via intramuscular delivery. When encapsulating antigen-encoding mRNA (e.g., optimized mCSA construct), Lipid-88 based LNPs drive robust humoral and cellular immunity, enabling complete protection against challenging SARS-CoV-2 variants (WA1/2020, Omicron BA.1, BQ.1) in preclinical models. Its design prioritizes potent immunogenicity with favorable safety profiles.

PPZ-A10 is an ionizable cationic lipid.It has been used in the generation of lipid nanoparticles (LNPs) for the delivery of siRNA and mRNA in vitro and in vivo. Intraperitoneal administration of LNPs containing PPZ-A10 and encapsulating an mRNA reporter preferentially accumulates in hepatic Kupffer cells and splenic macrophages in mice.

Lipid 119-23 is an ionizable lipid for mRNA delivery. 119-23 LNP exhibits an enhanced capability to express functional mCre in several categories of immune cells, spanning the liver, spleen and lung.

​TOT-5​​, a tri-oleoyl-Tris ionizable lipid (pKa 6.2), enables splenic B cell-targeted mRNA delivery via 15% DSPC-incorporated LNPs. Its charge-neutral, hydrophobic surface minimizes hepatic ApoE uptake and enhances complement C3 adsorption, facilitating CD21/35-mediated uptake by marginal zone B cells. In vivo, intravenous 15%DSPC-LNPs showed 8-fold higher spleen-to-liver luciferase expression vs 3%DSPC, with anti-CD21/35 blocking 60% B cell uptake. Intramuscular administration induced robust OVA-specific IgG (10^5 titer) and CTL responses (3.5% tetramer+ CD8+ T cells) while reducing hepatotoxicity (ALT/AST levels ≤40 U/L vs SM-102-LNPs' 80-120 U/L). Cryo-ET confirmed stable lamellar structures (80-100 nm, ζ-potential -2 mV). This formulation achieves safe, ligand-free splenic targeting for mRNA vaccines. 

ADA (Acid-Degradable Anionic Lipids) is revolutionizing mRNA delivery with its unique azido-acetal linker, enabling rapid hydrolysis in endosomes (pH ~6.0). This breakthrough technology ensures efficient endosomal escape, significantly enhancing mRNA delivery to target cells. ADA-LNPs excel in delivering mRNA to the spleen and liver, making them ideal for immune-related therapies.By degrading into biocompatible byproducts, ADA minimizes long-term tissue persistence and toxicity.ADA-LNPs outperform traditional LNPs, delivering mRNA more effectively to immune cells like macrophages and B cells.

DMA4-H228 is a novel, biodegradable lipidoid specifically engineered for spleen-targeted mRNA delivery.​​ Its structure combines a dimethylamino (DMA4) headgroup with a unique hyperbranched lipid tail (H228) synthesized via Michael addition, incorporating ester bonds for enhanced biodegradability. This design enables the formation of stable lipid nanoparticles (LNPs) (~170 nm) with high mRNA encapsulation efficiency (>96%). Critically, DMA4-H228 exhibits exceptional intrinsic tropism for the spleen (>98% targeting efficiency after IV administration), requiring no external targeting ligands. It selectively delivers mRNA to splenic antigen-presenting cells (APCs), including dendritic cells, macrophages, and B cells. This triggers potent immune activation: rapid IFNα secretion, upregulation of APC maturation markers (CD86/CD40), and robust antigen-specific immune responses. Demonstrating significant therapeutic potential, DMA4-H228-based mRNA vaccines effectively inhibit tumor growth in melanoma models (e.g., B16F10-OVA). This correlates with increased tumor-infiltrating CD8⁺ T cells, a shift towards pro-inflammatory M1 macrophages, elevated antigen-specific antibodies (IgG), and strong T cell responses (evidenced by IFNγ⁺ spots). Its ability to bypass liver tropism and directly activate splenic APCs makes DMA4-H228 a powerful platform for next-generation mRNA vaccines and cancer immunotherapy.

CL15F 9-5, a piperidine-based ionizable lipid, exhibits favorable properties for mRNA delivery in lipid nanoparticles (LNPs). Its apparent pKa ranges between 6.24–7.15, ideal for mRNA encapsulation and endosomal escape. LNPs formulated with CL15F 9-5 (50:38.5:10:1.5 molar ratio of ionizable lipid:cholesterol:DSPC:DMG-PEG2k) demonstrated high mRNA encapsulation efficiency (>90%) and maintained physicochemical stability (size, PDI, zeta potential) during storage at 4°C for 5 months . In vitro, CL15F 9-5 LNPs showed superior luciferase expression in HEK-293T cells compared to CL4F-based LNPs. In vivo, liver-targeted LNPs delivered hEPO mRNA effectively, with sustained serum hEPO levels post-storage. Intravenous administration of FLuc mRNA-loaded CL15F 9-5 LNPs yielded strong hepatic bioluminescence, confirming liver tropism. As a vaccine candidate, CL15F 9-5 induced robust antigen-specific cellular immunity in mice, with a 14-fold increase in IFN-γ spots compared to SM-102. Its enhanced stability is attributed to reduced aldehyde impurities, minimizing mRNA-lipid adduct formation.

9322-O16B is a lipidoid for the efficient delivery of antiCD19 mRNA CAR to murine primary macrophages. LNP 9322-O16B is more efficient than delivery with lipofectamine 2000 (LPF2K) or MC3.

TE-EP8-S is a single-component, ionizable cationic lipid designed specifically for the targeted delivery of mRNA to T cells within the spleen. This innovative lipid formulation enhances the efficiency and precision of mRNA-based therapies by ensuring optimal cellular uptake and expression in immune cells. Its unique structure and properties make it a promising tool for advancing immunotherapeutic applications.

93-O17S is an imidazole-based synthetic lipidoid for in vivo mRNA delivery. Lipid nanoparticles (LNPs) with 93-O17S promotes both the cross-presentation of tumor antigens and the intracellular delivery of cGAMP (STING agonist).

5A2-SC8 is a dendrimer for miRNA delivery to late-stage liver tumors with low hepatotoxicity. 5A2-SC8 shows potent EC50 < 0.02 mg/kg (siRNA against FVII (siFVII)) in dose-response experiments, and well tolerated in separate toxicity studies in chronically ill mice bearing MYC-driven tumors. 5A2-SC8 is a degradable lipid-like compound (ester-based dendrimer) for small RNAs delivery.5A2-SC8, was obtained by screening a large library of more than 1500 ester-based dendrimers containing ionizable amino groups, which have three tertiary amine heads and five lipid tails. Based on this library, the in vitro transfection efficiency of different formulations of 5A2-SC8 iLNPs was evaluated, discovering the optimal formulation (5A2-SC8, DOPE, cholesterol, PEG at a molar ratio of 15:15:30:3) of 5A2-SC8 iLNPs for delivering fumarylacetoacetate hydrolase (FAH) mRNA to liver.After the intravenous injection via tail, the model mice of hepatorenal tyrosinemia type I had strong FAH protein expression, which prevented body weight loss and increased the survival rate of hepatorenal tyrosinemia mice . In addition to introducing utility of 5A2-SC8 iLNPs for the therapeutic intervention, the 5A2-SC8 iLNPs containing DOTAP have been used to establish complex mouse models via intravenous injection, including in situ liverspecific cancer model and in situ lung-specific cancer model. Based on this iLNPs delivery system, 5A2-SC8 induced model construction method overcomes the time-consuming and costly disadvantages of traditional animal models establishing methods, including transgenesis and gene engineering in embryonic stem cells.

Lipid 8 iLNPs were used to deliver CRISPR-Cas9 mRNA and sgRNA which targeted to the PLK1 gene. The safety and excellent intracerebral diffusion performance of lipid 8 iLNPs ensured that the survival of murine glioblastoma multiforme (GBM) mice was extended. The median survival was extended by approximately 50% and the overall survival was increased by 30%. The treatment of metastatic adenocarcinoma was executed by the EGFRtargeted lipid 8 iLNPs. These iLNPs possessed the ability of tumor targeting, which could increase the accumulation of CRISPR-Cas9 mRNA and sgRNA within the tumor cells. After a single intraperitoneal administration,
80% PLK1 gene was edited and the overall survival of mice with high-grade ovarian cancer malignant ascites was enhanced by
80% . These results demonstrate the clinical potential of CRISPR-Cas9 gene editing system can be delivered by iLNPs for treating tumors, and provide new ideas for tumor gene therapy.

Sail Lipid 2231 is a novel ionizable lipid targeting to spleen developed by Sai Biomedicine.As described on US20250205167A1 Lipid 2231 features  a ​​pyrrolidine core​​ (5-membered ring) with biodegradable ester linkages and asymmetric C17/C11 hydrophobic chains. In vivo data shows moderate spleen targeting (Spleen RLU: ​​3.8E+06​​) with a spleen-to-liver ratio of ​​12.767​​. 

Lipid 2298 is a novel ionizable lipid developed by Sai Biomedicine demonstrates excellent performance with a spleen-to-liver ratio of 3.448​ and a very high total expression level of 2.4E+07. Lipid 2298 offers a strong balance of efficient systemic protein production and clear preferential delivery to the spleen.

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.

CICL1 (L829)​​ is a ​​novel ionizable cationic lipid​​ specifically engineered for ​​targeted lipid nanoparticles (tLNPs)​​ that enables efficient in vivo delivery of mRNA payloads to ​​CD8+ T cells​​. Designed to overcome limitations of conventional LNPs, CICL-1 (L-829)​​significantly ​​reduces off-target delivery to the liver​​ and exhibits ​​rapid clearance​​ compared to benchmark lipids like ALC-0315, while demonstrating ​​enhanced biodegradability and tolerability​​ in rodent and primate models. When incorporated into CD8-targeted tLNPs, CICL 1 (L829 enables ​​preferential transfection of CD8+ T cells​​ over other immune subsets, facilitating the generation of functional ​​anti-CD19 or anti-CD20 CAR T cells directly *in vivo​​*. These tLNP-engineered CAR T cells mediate ​​rapid, deep B-cell depletion​​ in humanized mice and cynomolgus monkeys, with repopulating B cells exhibiting a naïve phenotype suggestive of immune reset. By eliminating the need for ex vivo manufacturing or lymphodepleting chemotherapy, the L829-tLNP platform represents a ​​safer, scalable approach​​ for accessible CAR T therapy in oncology and autoimmune diseases.

TE AA3-Dlin is an optimized lipid nanoparticle (LNP) carrier designed for mRNA-based cancer immunotherapy, enabling precise in vivo dendritic cell (DC) reprogramming to enhance antitumor immunity. TE AA3-Dlin LNP exhibits superior serum stability, maintaining consistent particle size and low turbidity under physiological conditions, while protecting mRNA from degradation, which is crucial for effective delivery. Functionally, TE AA3-Dlin preferentially targets splenic DCs by leveraging ApoE-enriched protein coronas, facilitating efficient cellular uptake and mRNA expression, as demonstrated by enhanced EGFP signals in DCs.This targeting promotes DC maturation, antigen presentation, and membrane-bound IL-15 expression, activating cytotoxic T lymphocytes (CTLs) for tumor rejection. In models like melanoma and colon carcinoma, it synergizes with checkpoint inhibitors, showing minimal toxicity and robust immunological memory.

Lipid A-12 is an ionizable cationic lipid from Capstan Therapeutics and a close analog of CICL-1 (L829). The structure was modified by the extension of the headgroup linker from a two-carbon (C2) to a three-carbon (C3) spacer compared to CICL-1 (L829).

4A3-LNSC8​ is a strategically designed thiourea-functionalized ionizable lipid that serves as the foundational core for a novel anion-coordination delivery platform. Its structure features a central 4A3 amine headgroup symmetrically extended with four hydrophobic tails, each incorporating a biodegradable ester linkage and a key thiourea-bridged linker. The inclusion of the thiourea group is the pivotal innovation, as it provides specific hydrogen-bonding sites capable of interacting with various halide anions (F⁻, Cl⁻, I⁻). When formulated into lipid nanoparticles (LNPs) without anion coordination, 4A3-LNSC8 itself exhibits a characteristic liver tropism, efficiently delivering mRNA to hepatocytes following systemic administration, with a measured surface pKa of approximately 5.54. However, its primary significance lies in its role as a versatile precursor. The strong anion-binding capability of its thiourea linkers allows for predictable modulation of the LNP's properties. Upon binding with anions like Cl⁻, the resulting complex (e.g., Cl-4A3-LNSC8) undergoes a significant pKa shift, which reprograms the LNP's in vivo fate, redirecting mRNA delivery from the liver to secondary lymphoid organs such as the spleen and lymph nodes. Thus, 4A3-LNSC8 is not merely an efficient ionizable lipid but a programmable scaffold that enables precise control over organ-targeting specificity through simple anion coordination, offering a powerful rational design strategy for advanced mRNA therapeutics.

Cl-4A3-LNSC8​ represents a novel class of thiourea-functionalized ionizable lipids engineered for selective organ-targeted mRNA delivery. Its core innovation lies in an anion-coordination strategy, where the parent lipid, 4A3-LNSC8, binds chloride ions (Cl⁻) via hydrogen-bonding interactions with its thiourea groups. This binding event is not merely structural but functionally critical, as it induces a significant shift in the surface pKa of the resulting lipid nanoparticles (LNPs) from approximately 5.54 to 8.79. This pKa modulation is the key mechanism that redirects the organotropism of the LNPs upon systemic administration. While the unmodified 4A3-LNSC8 LNPs preferentially deliver mRNA to the liver, Cl-4A3-LNSC8 LNPs effectivelyreprogram this tropism, enabling highly efficient mRNA delivery to secondary lymphoid organs (SLOs), particularly the spleen and lymph nodes. This platform demonstrates remarkable efficacy, achieving up to 65.7% gene editing efficiency in splenic macrophages in vivo, significantly outperforming benchmark delivery systems. Furthermore, by leveraging the coordination with different halides, such as iodine for computed tomography (CT) contrast, the system can be adapted for dual-modal theranostic applications, enabling simultaneous lymphatic metastasis imaging and therapeutic mRNA delivery.

E12LA6B603（ILB3132，ILB-3132） is a novel ionizable amino lipid disclosed in patent WO2024198497A1, developed by MagicRNA, representing a highly efficient component for lipid nanoparticle (LNP) delivery systems.When formulated into LNPs, E12LA6B603 LNP achieves a remarkable 98.26% encapsulation efficiency for mRNA. It mediates superior in vitro transfection in dendritic cells (1.8E+05 intensity) and demonstrates best-in-class in vivo protein expression after intramuscular injection (2.2E+09 intensity). Most notably, in a B16-OVA melanoma model, therapeutic OVA-mRNA vaccines delivered by E12LA6B603 LNPs induced 100% complete tumor regression, highlighting its superior efficacy over benchmarks like DLin-MC3 and SM-102. Its biodegradable ester linkages and balanced structure make it a promising, potent candidate for next-generation mRNA vaccines and therapeutics.

CL15F 6-4 is a short-tail ionizable lipid from the piperidine-based CL15F series, characterized by its symmetric branched structure with a 6-carbon main chain and 4-carbon side chain. This specific tail length critically determines the lipid nanoparticle's (LNP) properties, resulting in larger particles with a high surface density of the phospholipid DSPC. This elevated DSPC density reduces interactions with serum proteins like ApoE, minimizing rapid liver clearance and shifting mRNA delivery preference towards the spleen. Consequently, CL15F 6-4 LNPs achieve efficient, endogenous spleen-targeted delivery, making them a highly promising candidate for enhancing vaccine efficacy by preferentially transfecting antigen-presenting cells without complex functionalization.

A28-C6B2 is a biodegradable ionizable lipid specifically engineered for spleen-targeted delivery. Through its unique branched structure, it bypasses hepatic uptake to achieve highly efficient transfection of F4/80+ macrophages and CD11c+ dendritic cells within the spleen. This lipid remains neutral in the bloodstream to minimize non-specific interactions, while undergoing protonation in the acidic environment of the endosome to facilitate nucleic acid release, thereby significantly enhancing the potency of mRNA vaccines and immunotherapies.

H5T5 is a leading ionizable lipid nanoparticle (LNP) formulation optimized for in vivomRNA delivery, featuring a pKa of 6.51, a size of ~154 nm, and a narrow polydispersity index (PDI) of 0.05. It demonstrated superior in vitromRNA transfection efficiency in primary immune cells, such as bone marrow-derived macrophages. Following intravenous administration, H5T5 exhibits precise organotropism, predominantly targeting the spleen and bone marrow, where it effectively delivers mRNA to a broad spectrum of immune cells, including macrophages, dendritic cells, T cells, B cells, and NK cells. This capability enables its core application: the in vivogeneration of "pan-CAR" immune cells. When loaded with anti-HER2 CAR mRNA, the H5T5-based therapy achieved potent tumor regression and prolonged survival in multiple solid tumor models. Preliminary safety assessments indicated a manageable cytokine profile and no significant organ toxicity, positioning it as a promising platform for in vivocell engineering.

Sail Lipid 2308​ is a novel ionizable lipid targeting to spleen developed by Sai Biomedicine.As described on US20250205167A1, Lipid 2308 was designed with a ​​piperidine core​​ (6-membered ring) and asymmetric C17/C11 chains, this lipid achieves unprecedented ​​spleen-specificity​​. It demonstrates dominant spleen accumulation (Spleen RLU: ​​7.8E+06​​, 91.8% of total signal) with a record ​​spleen-to-liver ratio of 112.7​​ (9× higher than 2231). Despite lower protein expression (hEPO: 11,000 ng/mL), near-zero liver uptake (Liver RLU: 66,000) makes Lipid 2308 unparalleled for vaccine/immunotherapy applications targeting splenic immune cells.

2Ac3-C18 is a unique ionizable lipid with a distinct degradable core structure：featuring 2 acrylate units and 3 amine groups—linked to a C18 alkyl chain. Its LNPs (formulated with DOPE/cholesterol/DMG-PEG2000) exhibit spleen-specific mRNA delivery in vivo.

(4S)-KEL12​​ is a novel, biodegradable ionizable lipid developed for advanced mRNA vaccine delivery. It was rationally designed by incorporating both a ketal group in the linker and ester segments in the hydrophobic tails, a dual-degradable strategy aimed at enhancing its safety profile. Through iterative optimization, (4S)-KEL12 was identified as a lead candidate with an optimal pKa value of approximately 6.78, which is crucial for efficient mRNA encapsulation and endosomal release.

GL5 is an ionizable guanidine-based lipid nanoparticle (G-LNP) designed for superior mRNA delivery. Its guanidinocarbonyl-pyrrole (GCP) headgroup enables pH-responsive behavior and strong mRNA binding via bidentate hydrogen bonds. The cholesterol-free GL5-3 formulation forms compact, stable nanoparticles (~90-120 nm) that exhibit excellent spleen-targeting capability after intravenous injection.GL5-LNPs efficiently deliver mRNA to antigen-presenting cells (APCs), enhancing antigen presentation and T cell activation. In cancer immunotherapy models, GL5-based mRNA vaccines provided complete tumor protection and induced durable immune memory. The platform also enables mRNA delivery to other organs like the pancreas via different administration routes, demonstrating remarkable versatility and therapeutic potential.