We adopted a rational approach to design cationic lipids for use in formulations to deliver small interfering RNA (siRNA). Starting with the ionizable cationic lipid 1,2-dilinoleyloxy-3-dimethylaminopropane (DLinDMA), a key lipid component of stable nucleic acid lipid particles (SNALP) as a benchmark, we used the proposed in vivo mechanism of action of ionizable cationic lipids to guide the design of DLinDMA-based lipids with superior delivery capacity. The best-performing lipid recovered after screening (DLin-KC2-DMA) was formulated and characterized in SNALP and demonstrated to have in vivo activity at siRNA doses as low as 0.01 mg/kg in rodents and 0.1 mg/kg in nonhuman primates. To our knowledge, this represents a substantial improvement over previous reports of in vivo endogenous hepatic gene silencing.

No abstract

Therapeutics based on RNA interference (RNAi) have emerged as a potential new class of drugs for treating human disease by silencing the target messenger RNA (mRNA), thereby reducing levels of the corresponding pathogenic protein. The major challenge for RNAi therapeutics is the development of safe delivery vehicles for small interfering RNAs (siRNAs). We previously showed that cholesterol-conjugated siRNAs (chol-siRNA) associate with plasma lipoprotein particles and distribute primarily to the liver after systemic administration to mice. We further demonstrated enhancement of silencing by administration of chol-siRNA pre-associated with isolated high-density lipoprotein (HDL) or low-density lipoprotein (LDL). In this study, we investigated mimetic lipoprotein particle prepared from recombinant apolipoprotein A1 (apoA) and apolipoprotein E3 (apoE) as a delivery vehicle for chol-siRNAs. We show that apoE-containing particle (E-lip) is highly effective in functional delivery of chol-siRNA to mouse liver. E-lip delivery was found to be considerably more potent than apoA-containing particle (A-lip). Furthermore, E-lip–mediated delivery was not significantly affected by high endogenous levels of plasma LDL. These results demonstrate that E-lip has substantial potential as delivery vehicles for lipophilic conjugates of siRNAs.

The main goal of this study was to evaluate tumor necrosis factor-alpha (TNF-α) gene silencing in peritoneal macrophages upon activation with lipopolysaccharide (LPS), using CD44-targeting hyaluronic acid (HA)-based nanoparticles encapsulating TNF-α-specific small interfering RNA (siTNF-α). HA nanoparticles were formulated by blending hyaluronic acid-poly(ethylene imine) (HA-PEI), hyaluronic acid-hexyl fatty acid (HA-C6), and hyaluronic acid-poly(ethylene glycol) (HA-PEG) in 3:2:1 weight ratio, and encapsulating siTNF-α to form spherical particles of 78-90 nm diameter. Following intraperitoneal (IP) administration in LPS-treated C57BL/6 mice, the nanoparticles were actively taken up by macrophages and led to a significant downregulation of peritoneal TNF-α level. Downregulation of peritoneal macrophage-specific TNF-α also had a significant impact on other pro-inflammatory cytokine and chemokine levels in the serum. The C57BL/6 group of mice challenged with 5 mg/kg LPS had a significantly higher survival rate when they were treated with 3 mg/kg siTNF-α, either prior or simultaneously with the LPS administration, as compared to the LPS-challenged mice, which were treated with controls including the scrambled siRNA formulation. Overall, the results of this study demonstrate that CD44 targeting HA nanoparticles can selectively deliver siTNF-α to peritoneal macrophages leading to downregulation of pro-inflammatory cytokines in the peritoneal fluid and in the serum. This RNAi strategy could potentially provide an important therapeutic modality for acute inflammatory diseases, such as septic shock.