Delivery of siRNA to the mouse lung via a functionalized lipopolyamine.

We have designed a series of versatile lipopolyamines which are amenable to chemical modification for in vivo delivery of small interfering RNA (siRNA). This report focuses on one such lipopolyamine (Staramine), its functionalized derivatives and the lipid nanocomplexes it forms with siRNA. Intravenous (i.v.) administration of Staramine/siRNA nanocomplexes modified with methoxypolyethylene glycol (mPEG) provides safe and effective delivery of siRNA and significant target gene knockdown in the lungs of normal mice, with much lower knockdown in liver, spleen, and kidney. Although siRNA delivered via Staramine is initially distributed across all these organs, the observed clearance rate from the lung tissue is considerably slower than in other tissues resulting in prolonged siRNA accumulation on the timescale of RNA interference (RNAi)-mediated transcript depletion. Complete blood count (CBC) analysis, serum chemistry analysis, and histopathology results are all consistent with minimal toxicity. An in vivo screen of mPEG modified Staramine nanocomplexes-containing siRNAs targeting lung cell-specific marker proteins reveal exclusive transfection of endothelial cells. Safe and effective delivery of siRNA to the lung with chemically versatile lipopolyamine systems provides opportunities for investigation of pulmonary cell function in vivo as well as potential treatments of pulmonary disease with RNAi-based therapeutics.

Versatile cationic lipids for siRNA delivery.

Exploitation of the RNA interference (RNAi) pathway offers the promise of new and effective therapies for a wide variety of diseases. Clinical development of new drugs based on this platform technology is still limited, however, by a lack of safe and efficient delivery systems. Here we report the development of a class of structurally versatile cationic lipopolyamines designed specifically for delivery of siRNA which show high levels of target transcript knockdown in a range of cell types in vitro. A primary benefit of these lipids is the ease with which they may be covalently modified by the addition of functional molecules. For in vivo applications one of the core lipids (Staramine) was modified with methoxypolyethylene glycols (mPEGs) of varying lengths. Upon systemic administration, PEGylated Staramine nanoparticles containing siRNA targeting the caveolin-1 (Cav-1) transcript caused a reduction of the Cav-1 transcript of up to 60%, depending on the mPEG length, specifically in lung tissue after 48h compared to treatment with non-silencing siRNA. In addition, modification with mPEG reduced toxicity associated with intravenous administration. The ability to produce a high level of target gene knockdown in the lung with minimal toxicity demonstrates the potential of these lipopolyamines for use in developing RNAi therapeutics for pulmonary disease.