RNAi-mediated gene silencing in non-human primates

Abstract

The opportunity to harness the RNA interference (RNAi) pathway to silence disease-causing genes holds great promise for the development of therapeutics directed against targets that are otherwise not addressable with current medicines. Although there are numerous examples of in vivo silencing of target genes after local delivery of small interfering RNAs (siRNAs), there remain only a few reports of RNAi-mediated silencing in response to systemic delivery of siRNA, and there are no reports of systemic efficacy in non-rodent species. Here we show that siRNAs, when delivered systemically in a liposomal formulation, can silence the disease target apolipoprotein B (ApoB) in non-human primates. APOB-specific siRNAs were encapsulated in stable nucleic acid lipid particles (SNALP) and administered by intravenous injection to cynomolgus monkeys at doses of 1 or 2.5 mg kg(-1). A single siRNA injection resulted in dose-dependent silencing of APOB messenger RNA expression in the liver 48 h after administration, with maximal silencing of >90%. This silencing effect occurred as a result of APOB mRNA cleavage at precisely the site predicted for the RNAi mechanism. Significant reductions in ApoB protein, serum cholesterol and low-density lipoprotein levels were observed as early as 24 h after treatment and lasted for 11 days at the highest siRNA dose, thus demonstrating an immediate, potent and lasting biological effect of siRNA treatment. Our findings show clinically relevant RNAi-mediated gene silencing in non-human primates, supporting RNAi therapeutics as a potential new class of drugs.

Special delivery: targeted therapy with small RNAs

“…30,31 The PEG-lipid coat stabilizes the particle during formation and provides a neutral and hydrophilic exterior that prevents rapid systemic clearance. The lipid bilayer contains a mixture of cationic and fusogenic lipids that facilitate internalization of the SNALP and endosomal escape of its siRNA payload.…”

Principles and effects of microRNA-mediated post-transcriptional gene regulation

“…Archean and eucaryotes harbour several key components of the RNAi machinery and the function of RNAi-related mechanisms has been studied in diverse eucaryotic model systems (Cerutti and Casas-Mollano, 2006). RNAi, apart from providing an indispensable reverse genetic tool (Elbashir et al, 2001) and promising therapeutic approach (Zimmermann et al, 2006), is key regulator of gene expression on both transcriptional and post-transcriptional level and it is involved in the defence against viruses and bacteria. RNAi provides switch points in many developmental processes and it is a key determinant in regulating mechanisms leading to diseases including cancer (Wienholds and Plasterk, 2005).…”

Involvement of c-jun in human liposarcoma growth: supporting data from clinical immunohistochemistry and DNAzyme efficacy

“…These levels are comparable to siRNA potency in vitro, and far lower than that required for siRNA efficacy in vivo [usually mg/kg doses administered systemically, 22,23 ]. Downregulation of c-jun may therefore be beneficial, economically so with Dz13, in perturbing growth of LS via stimulation of apoptosis in cancer cells.…”