Hydrophobic Domain Structure of Linear-Dendritic Poly(ethylene glycol) Lipids Affects RNA Delivery of Lipid Nanoparticles.

In this work, a series of linear-dendritic poly(ethylene glycol) (PEG) lipids (PEG-GnCm) were synthesized through a strategy using sequential aza- and sulfa-Michael addition reactions. The effect of modulating the hydrophobic domain of linear-dendritic PEG lipids was systematically investigated for in vitro and in vivo small RNA delivery as the surface-stabilizing component of 5A2-SC8 dendrimer lipid-based nanoparticles (DLNPs). The lipid alkyl lengths (C8, C12, and C16) and dendrimer generations (G1, G2, and G3) were altered to create PEG-GnCm with different physical properties and anchoring potential. The tail chemical structure of PEG-GnCm did not affect the formulation of 5A2-SC8 DLNPs, including the nanoparticle size, RNA encapsulation, and stability. However, the tail chemical structure did dramatically affect the RNA delivery efficacy of the formed 5A2-SC8 DLNPs with different PEG-GnCm. First-generation PEG lipids (PEG-G1C8, PEG-G1C12, and PEG-G1C16) and a second-generation PEG lipid (PEG-G2C8) formed 5A2-SC8 DLNPs that could deliver siRNAs effectively in vitro and in vivo. 5A2-SC8 DLNPs formulated with second-generation PEG lipids (PEG-G2C12 and PEG-G2C16) and all three third-generation PEG lipids (PEG-G3C8, PEG-G3C12, and PEG-G3C16) lost the ability to deliver siRNA effectively in vitro and in vivo. Overall, we determined that the hydrophobic domain chemical structure of linear-dendritic poly(ethylene glycol) lipids affected the RNA delivery of DLNPs by impacting the escape of 5A2-SC8 DLNPs from endosomes at early cell incubation times, thereby indicating how PEG lipid anchoring and chemical structure can modulate in vitro and in vivo siRNA delivery efficacies.

Modular degradable dendrimers enable small RNAs to extend survival in an aggressive liver cancer model.

RNA-based cancer therapies are hindered by the lack of delivery vehicles that avoid cancer-induced organ dysfunction, which exacerbates carrier toxicity. We address this issue by reporting modular degradable dendrimers that achieve the required combination of high potency to tumors and low hepatotoxicity to provide a pronounced survival benefit in an aggressive genetic cancer model. More than 1,500 dendrimers were synthesized using sequential, orthogonal reactions where ester degradability was systematically integrated with chemically diversified cores, peripheries, and generations. A lead dendrimer, 5A2-SC8, provided a broad therapeutic window: identified as 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 (>75 mg/kg dendrimer repeated dosing). Delivery of let-7 g microRNA (miRNA) mimic inhibited tumor growth and dramatically extended survival. Efficacy stemmed from a combination of a small RNA with the dendrimer's own negligible toxicity, therefore illuminating an underappreciated complication in treating cancer with RNA-based drugs.

Intercalation-mediated nucleic acid nanoparticles for siRNA delivery.

Tremendous effort has been made to improve stability and delivery efficacy of small RNA therapeutics. However, nearly all current nano-encapsulation carriers utilize the critical balance between only two interacting parameters: RNA-binding electrostatic interactions and nanoparticle-stabilizing hydrophobic interactions. We report the development of intercalation-meditated nucleic acid (IMNA) nanoparticles, which utilize intercalation as a third interaction to enhance small RNA delivery. This toolbox expansion of interaction parameters may inspire the use of additional forces in nanoparticle drug carriers to increase potency and stability.