Development of a liver-targeted siRNA delivery platform with a broad therapeutic window utilizing biodegradable polypeptide-based polymer conjugates

The greatest challenge standing in the way of effective in vivo siRNA delivery is creating a delivery vehicle that mediates a high degree of efficacy with a broad therapeutic window. Key structure-activity relationships of a poly( amide) polymer conjugate siRNA delivery platform were explored to discover the optimized polymer parameters that yield the highest activity of mRNA knockdown in the liver. At the same time, the poly(amide) backbone of the polymers allowed for the metabolism and clearance of the polymer from the body very quickly, which was established using radiolabeled polymers to demonstrate the time course of biodistribution and excretion from the body. The fast degradation and clearance of the polymers provided for very low toxicity at efficacious doses, and the therapeutic window of this poly(amide)-based siRNA delivery platform was shown to be much broader than a comparable polymer platform. The results of this work illustrate that the poly(amide) platform has a promising future in the development of a siRNA-based drug approved for human use. (C) 2014 Elsevier B.V. All rights reserved.