Lipid S4 is an advanced ionizable lipid engineered for systemic mRNA delivery to the brain, leveraging SR-57227—a high-affinity 5-HT3 receptor ligand—as its core head group to enable targeted blood-brain barrier (BBB) penetration via receptor-mediated transcytosis, while incorporating amino linkers for pH-responsive ionization and biodegradable branched ester tails to facilitate efficient endosomal escape and intracellular mRNA release; optimized through orthogonal screening into OS4 LNP (formulated at S4/DOPE/Chol/DMG-PEG2k = 40:40:60:0.75 molar ratio), it demonstrated a 13.3-fold increase in brain mRNA expression compared to FDA-approved MC3 LNPs, and further conjugation with the Tat cell-penetrating peptide yielded OS4T LNP, boosting delivery efficiency by 12.7-fold over OS4 alone and enabling broad mRNA expression across neurons, astrocytes, microglia, and endothelial cells; validated in orthotopic glioblastoma models, OS4T delivered engineered IL-12 mRNA, suppressing tumor growth and extending median survival to 37 days (vs. 17 days for controls) with minimal systemic toxicity, positioning S4-based LNPs as a robust, translatable platform for CNS-targeted therapeutics.

306-O12B-3 is an ionizable lipidoid with cationic properties, commonly used in lipid nanoparticle (LNP) formulations for antisense oligonucleotide (ASO) delivery. When administered intravenously in mice, LNPs incorporating 306-O12B-3 exhibit liver-specific accumulation. Studies show that ASO-loaded LNPs containing 306-O12B-3 effectively silence hepatic PCSK9 expression by targeting the proprotein convertase subtilisin/kexin type 9 gene. Additionally, when combined with the cationic lipidoid NT1-O14B (Item No. 37095), these LNPs can deliver tau-targeting ASOs to the brain, reducing tau protein levels in mice.

MK-16 is a specialized lipid designed to traverse the blood-brain barrier (BBB) for effective mRNA delivery. Its formulation, MK 16 BLNP, leverages dual mechanisms involving caveolae and γ-secretase to facilitate BBB penetration, ensuring the targeted and efficient transport of functional mRNA to diverse brain cell types. Demonstrating excellent tolerability across a range of dosing regimens, MK16 BLNP represents a promising platform for brain-targeted therapeutic applications.

TD5 is a brain-targeting lipid nanoparticle (BLNP) engineered for efficient mRNA delivery to the central nervous system (CNS) via intrathecal injection. It incorporates a tryptamine-derived ionizable lipid headgroup, myristic acid hydrocarbon tails, and a biodegradable carbonate ester linker, enabling pH-dependent mRNA encapsulation (81.7% efficiency) and brain cell-specific targeting. With a hydrodynamic diameter of 107.5 nm, near-neutral pKa (7.30), and mild positive charge, TD 5 demonstrates superior CNS tropism through serotonin receptor (5-HT1A)-mediated endocytosis. In vitro, TD-5 achieved 80.8% GFP expression in SH-SY5Y neuronal cells, outperforming MC3 LNPs by 50-fold. Following intrathecal administration in mice, TD-5 mediated GFP expression in 29.6% of neurons and 38.1% of astrocytes brain-wide, with 10-fold higher CNS specificity than peripheral organs. Genome editing studies showed TD5-delivered Cas9/sgRNA induced tdTomato activation in ≈30% of neurons and 40% of astrocytes across key brain regions. Safety profiling revealed minimal systemic immune responses (lower IL-6, IL-12p40 vs MC3 LNPs), normal hepatic/renal biomarkers, and no histopathological toxicity. The optimized structure balances myristic chain hydrophobicity for membrane interaction, ionizable amines for mRNA complexation, and tryptamine-mediated targeting for enhanced CNS uptake, establishing TD5 as a promising platform for CNS gene therapies.

NT1-O14B is a tryptamine-containing cationic lipidoid.1 It has been used in combination with other lipids in the formation of lipid nanoparticles (LNPs). Intravenous administration of LNPs containing NT1-O14B and encapsulating antisense nucleotides against tau decreases tau brain levels in mice.

NT1-O12B, an endogenous chemical and a neurotransmitter-derived lipidoid (NT-lipidoid), is an effective carrier for enhanced brain delivery of several blood-brain barrier (BBB)-impermeable cargos. Doping NT1-O12B into BBB-impermeable lipid nanoparticles (LNPs) gives the LNPs the ability to cross the BBB. NT-lipidoids formulation not only facilitate cargo crossing of the BBB, but also delivery of the cargo into neuronal cells for functional gene silencing or gene recombination.

F11T6 is a next-generation lipid nanoparticle (LNP) optimized for ultra-efficient neuron-targeted mRNA delivery, featuring a dual-tetrahydrofuran (THF) core and four pH-responsive acetal tails. Its unique bis-THF architecture enhances lipid bilayer stability and promotes brain-specific biodistribution, achieving ​​16.4% GFP+ neurons​​ in vivo—the highest reported among CNS-targeting LNPs. Cryo-EM reveals a compact spherical structure (Ø~150 nm) with 93.2% mRNA encapsulation efficiency, while THF-acetal synergy enables rapid endosomal escape (Pearson coefficient: 0.16 vs. 0.27 for F10T5). Preclinical studies show F11T6 leverages meningeal lymphatic transport for brain accumulation, yielding ​​13.0% neuron-specific tdTomato expression​​ in Ai14 mice, surpassing F10T5 (8.93%) and SM102 (0.1%). Mechanistically, the dual-THF core strengthens interactions with lipoprotein receptors on brain endothelial cells, whereas acetal tails undergo acid-triggered hydrolysis in endosomes, releasing mRNA into the cytoplasm. Despite slightly higher liver/spleen accumulation than F10T5, toxicology assessments confirm no hepatorenal toxicity (BUN/ALT/AST within normal ranges) or histopathological changes. Co-localization analyses demonstrate superior penetration into deep brain regions like the hippocampus, critical for treating neurodegenerative disorders. With a LogD of 12.3, F11T6 balances lipid solubility and biodegradability, outperforming clinical benchmarks in both efficiency (40× SM102) and neuron specificity. This platform holds transformative potential for delivering CRISPR-Cas9, siRNA, or neurotrophic factors, particularly in diseases demanding high-dose CNS transfection with minimal off-target effects.