Novel endosomolytic poly(amido amine) polymer conjugates for systemic delivery of siRNA to hepatocytes in rodents and nonhuman primates.

The application of small interfering (si)RNAs as potential therapeutic agents requires safe and effective methods for their delivery to the cytoplasm of the target cells and tissues. Recent studies have shown significant progress in the development of targeting reagents that facilitate the recognition of, and siRNA delivery to, specific cell types. Among recently reported delivery approaches, polymers with amphipathic properties have been used to enable endosome escape and cytosolic delivery. Here, we describe a linear amphipathic poly(amido amine) polymer conjugate system for the efficient siRNA delivery in vitro and in vivo. This polymer contains a novel amine bearing bis-acrylamide monomer designed for increasing amine density, which resulted in substantial improvement in liver uptake and RNAi activity compared to our previously reported poly(amido amine disulfide) polymer.1 The activity for this liver targeted delivery system was demonstrated in rodents and nonhuman primates.

An in vivo evaluation of amphiphilic, biodegradable peptide copolymers as siRNA delivery agents.

A series of amphiphilic, biodegradable polypeptide copolymers were prepared for the delivery of siRNA (short interfering ribonucleic acid). The molecular weight (or polymer chain length) of the linear polymer was controlled by reaction stoichiometry for the 11.5, 17.2, and 24.6 kDa polypeptides, and the highest molecular weight polypeptide was prepared using a sequential addition method to obtain a polypeptide having a molecular weight of 38.6 kDa. These polymers were used to prepare polymer conjugate systems designed to target and deliver an apolipoprotein B (ApoB) siRNA to hepatocyte cells and to help delineate the effect of polymer molecular weight or polymer chain length on siRNA delivery in vivo. A clear trend in increasing potency was found with increasing molecular weight of the polymers examined (at a constant polymer:siRNA (w/w) ratio), with minimal toxicity found. Furthermore, the biodegradability of these polymer conjugates was examined and demonstrates the potential of these systems as siRNA delivery vectors.

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.

Anxiety and memory test performance.

The present study examined the relationship of extra-test anxiety to memory test performance among patients undergoing cardiopulmonary bypass (N = 47) and back surgery (N = 24). These patients were chosen because they are often anxious before surgery and thus serve as a model of extra-test anxiety. This examination is important in neuropsychology because anxiety may serve as an extraneous factor compromising the validity of attention and memory scores. Anxiety level, determined from self-report and experimenter ratings, and memory performance, as measured by the Memory Assessment Scales and memory self-report, were assessed 1 to 2 days presurgery and approximately 6 weeks post surgery. The study further examined whether anxiety's influence on test performance is mediated by an impulsive cognitive style, as indicated by the Matching Familiar Figures Test. Multivariate analysis of variance (MANOVA) revealed no significant change in state anxiety during the testing interval. MANOVA did reveal significant differences between the two surgery groups on anxiety, and younger patients demonstrated greater anxiety about their upcoming surgery. An examination of the intercorrelations of anxiety and memory scores revealed that they do not share variance and are essentially unrelated. Although the subjects were moderately anxious about the upcoming surgery, this did not apparently influence their performance on memory tests.

Evidence for a dysfunctional prefrontal circuit in patients with an impulsive aggressive disorder.

Humans with lesions to the orbital/medial prefrontal cortex and interconnected areas display impulsive aggressive behavior. To examine further the relationship between impulsive aggression and orbital/medial prefrontal dysfunction, we measured the behavioral performance of psychiatric patients with a disorder characterized by impulsive aggression, Intermittent Explosive Disorder (IED). Presently, no evidence exists for a localized brain lesion in IED subjects. However, on the basis of the location of brain lesions that produce acquired impulsive aggression, we hypothesized that IED subjects would exhibit test performance similar to patients with lesions to the orbital/medial prefrontal cortex. Subjects with IED and controls were administered three tests sensitive to lesions of the orbital/medial prefrontal circuit: the Iowa Gambling Task, facial emotion recognition, and odor identification, and two control tests of working memory. On the gambling task, IED subjects continued to make disadvantageous decisions throughout the 100 trials, whereas controls learned to avoid disadvantageous decisions. On the facial recognition test, IED subjects were impaired at recognizing "anger," "disgust," and "surprise," and they were biased to label neutral faces with "disgust" and "fear." On odor identification, IED subjects were mildly anosmic and were impaired relative to controls. However, on the working memory control tests, both groups performed similarly. Across tests, the performance of IED subjects resembles the performance of patients with orbital/medial prefrontal lesions in previous studies. These results extend the link between dysfunction of the orbital/medial prefrontal circuit and impulsive aggressive behavior.