Small interfering RNAs (siRNAs) conjugated to a trivalent N-acetylgalactosamine (GalNAc) ligand are being evaluated in investigational clinical studies for a variety of indications. The typical development candidate selection process includes evaluation of the most active compounds for toxicity in rats at pharmacologically exaggerated doses. The subset of GalNAc-siRNAs that show rat hepatotoxicity is not advanced to clinical development. Potential mechanisms of hepatotoxicity can be associated with the intracellular accumulation of oligonucleotides and their metabolites, RNA interference (RNAi)-mediated hybridization-based off-target effects, and/or perturbation of endogenous RNAi pathways. Here we show that rodent hepatotoxicity observed at supratherapeutic exposures can be largely attributed to RNAi-mediated off-target effects, but not chemical modifications or the perturbation of RNAi pathways. Furthermore, these off-target effects can be mitigated by modulating seed-pairing using a thermally destabilizing chemical modification, which significantly improves the safety profile of a GalNAc-siRNA in rat and may minimize the occurrence of hepatotoxic siRNAs across species.

Despite six decades of clinical experience with the polymyxin class of antibiotics, their dose-limiting nephrotoxicity remains difficult to predict due to a paucity of sensitive biomarkers. Here, we evaluate the performance of standard of care and next-generation biomarkers of renal injury in the detection and monitoring of polymyxin-induced acute kidney injury in male Han Wistar rats using colistin (polymyxin E) and a polymyxin B (PMB) derivative with reduced nephrotoxicity, PMB nonapeptide (PMBN). This study provides the first histopathological and biomarker analysis of PMBN, an important test of the hypothesis that fatty acid modifications and charge reductions in polymyxins can reduce their nephrotoxicity. The results indicate that alterations in a panel of urinary kidney injury biomarkers can be used to monitor histopathological injury, with Kim-1 and α-GST emerging as the most sensitive biomarkers outperforming clinical standards of care, serum or plasma creatinine and blood urea nitrogen. To enable the prediction of polymyxin-induced nephrotoxicity, an in vitro cytotoxicity assay was employed using human proximal tubule epithelial cells (HK-2). Cytotoxicity data in these HK-2 cells correlated with the renal toxicity detected via safety biomarker data and histopathological evaluation, suggesting that in vitro and in vivo methods can be incorporated within a screening cascade to prioritize polymyxin class analogs with more favorable renal toxicity profiles.

Objective. Bruton's tyrosine kinase (BTK) plays a critical role in B cell development and function. We recently described a selective BTK inhibitor, RN486, that blocks B cell receptor (BCR) and Fc␥ receptor signaling and is efficacious in animal models of arthritis. The aim of this study was to examine the potential efficacy of BTK in systemic lupus erythematosus (SLE), using an NZB ؋ NZW mouse model of spontaneous SLE.Methods. Mice received RN486 or its vehicle (administered in chow) at a final concentration of 30 mg/kg for 8 weeks, starting at 32 weeks of age.Results

Short interfering RNAs (siRNAs) and antisense oligonucleotides (ASOs) are the most clinically advanced oligonucleotide-based platforms. A number of N-acetylgalactosamine (GalNAc)-conjugated siRNAs (GalNAc-siRNAs), also referred to as RNA interference (RNAi) therapeutics, are currently in various stages of development, though none is yet approved. While the safety of ASOs has been the subject of extensive review, the nonclinical safety profiles of GalNAc-siRNAs have not been reported. With the exception of sequence differences that confer target RNA specificity, GalNAc-siRNAs are largely chemically uniform, containing limited number of phosphorothioate linkages, and 2’-O-methyl and 2’-deoxy-2’-fluoro ribose modifications. Here, we present the outcomes of short-term (3–5 week) rat and monkey weekly repeat-dose toxicology studies of six Enhanced Stabilization Chemistry GalNAc-siRNAs currently in clinical development. In nonclinical studies at supratherapeutic doses, these molecules share similar safety signals, with histologic findings in the organ of pharmacodynamic effect (liver), the organ of elimination (kidney), and the reticuloendothelial system (lymph nodes). The majority of these changes are nonadverse, partially to completely reversible, correlate well with pharmacokinetic parameters and tissue distribution, and often reflect drug accumulation. Furthermore, all GalNAc-siRNAs tested to date have been negative in genotoxicity and safety pharmacology studies.

Background: The reovirus M1 genome segment encodes the µ2 protein, a structurally minor component of the viral core, which has been identified as a transcriptase cofactor, nucleoside and RNA triphosphatase, and microtubule-binding protein. The µ2 protein is the most poorly understood of the reovirus structural proteins. Genome segment sequences have been reported for 9 of the 10 genome segments for the 3 prototypic reoviruses type 1 Lang (T1L), type 2 Jones (T2J), and type 3 Dearing (T3D), but the M1 genome segment sequences for only T1L and T3D have been previously reported. For this study, we determined the M1 nucleotide and deduced µ2 amino acid sequences for T2J, nine other reovirus field isolates, and various T3D plaque-isolated clones from different laboratories.