PEG-free, Triphosphate-Stabilized LNPs Enable Potent RNA Delivery

Hamraz, G. M.; Saucedo-Espinosa, M. A.; Walzer, K. C.; Frohns, F.; Schlohsarczyk, E. K.; Froelich, B.; Kaeppler, J.; Schmidt, S.; Hopf, C.; Panzner, S.

doi:10.64898/2025.12.19.695515

bioRxiv · 10.64898/2025.12.19.695515

PEG-free, Triphosphate-Stabilized LNPs Enable Potent RNA Delivery

Hamraz, G. M.·Saucedo-Espinosa, M. A.·Walzer, K. C.·Frohns, F.·Schlohsarczyk, E. K.·Froelich, B.·Kaeppler, J.·Schmidt, S.·Hopf, C.·Panzner, S.

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Abstract

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=108 SRC="FIGDIR/small/695515v2_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@d919d8org.highwire.dtl.DTLVardef@12fe9aforg.highwire.dtl.DTLVardef@96e2d2org.highwire.dtl.DTLVardef@54f73_HPS_FORMAT_FIGEXP M_FIG C_FIG Polyethylene glycol (PEG)-lipids have long enabled lipid nanoparticle (LNP) formulations by providing steric stabilization and prolonged circulation. However, anti-PEG immune responses may impede repeated systemic dosing in mRNA therapeutics due to the phenomenon known as accelerated blood clearance (ABC). Here, we introduce a PEG-free, polyanionic alternative in which sodium triphosphate (3P) electrostatically associates with ionizable surface lipids, conferring long-term colloidal stability through charge repulsion rather than steric shielding. 3P-LNPs maintained size uniformity, morphology, and mRNA integrity for over nine months at 4 {degrees}C. In a proof-of-concept study involving a single intravenous injection of LNPs in mice carrying a luciferase and a GFP transgene, early expression was approximately two-fold higher compared to PEG-LNPs, while expression levels at 24 hours and hepatic tolerability remained comparable. Serum enzyme and cytokine profiles indicated no necrosis or inflammation. These findings establish 3P-LNPs as a stable, biocompatible platform free of PEG, with potential for repeat systemic mRNA administration while avoiding PEG-related effects.

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Hamraz, G. M., Saucedo-Espinosa, M. A., Walzer, K. C., Frohns, F., Schlohsarczyk, E. K., Froelich, B., Kaeppler, J., Schmidt, S., Hopf, C., Panzner, S.. 2025-12-22. PEG-free, Triphosphate-Stabilized LNPs Enable Potent RNA Delivery. https://doi.org/10.64898/2025.12.19.695515

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