CA2d is an ionizable lipid developed for systemic mRNA delivery to the central nervous system. Its architecture combines an MK-0752-derived CNS-accessing moiety, a short three-carbon diamine spacer, a tertiary ionizable amine, and two acetal-containing hydrophobic tails. When formulated with DOPE, cholesterol and DMG-PEG2000, CA2d LNPs crossed the blood-brain barrier through caveolae- and γ-secretase-associated transcytosis and delivered mRNA to neurons, astrocytes, microglia and brain endothelial cells. Following intravenous administration of FLuc mRNA at 0.5 mg/kg in mice, CA2d produced 16.6-fold higher brain expression than MC3 and 8.6-fold higher expression than SM-102 at 6 hours. CA2d was further evaluated in repeated brain-cell transfection studies, a pilot rhesus macaque experiment and a tPA-modified TGF-β1 mRNA formulation for ischemic stroke. These results support CA2d as a promising preclinical research lipid for investigating non-viral CNS mRNA delivery; it has not been clinically validated.
