Direct comparison of in vivo antisense activity of ENA oligonucleotides targeting PTP1B mRNA with that of 2'-O-(2-methoxy)ethyl-modified oligonucleotides

Inhaled siRNA Formulations for Respiratory Diseases: From Basic Research to Clinical Application

The development of siRNA technology has provided new opportunities for gene-specific inhibition and knockdown, as well as new ideas for the treatment of disease. Four siRNA drugs have already been approved for marketing. However, the instability of siRNA in vivo makes systemic delivery ineffective. Inhaled siRNA formulations can deliver drugs directly to the lung, showing great potential for treating respiratory diseases. The clinical applications of inhaled siRNA formulations still face challenges because effective delivery of siRNA to the lung requires overcoming the pulmonary and cellular barriers. This paper reviews the research progress for siRNA inhalation formulations for the treatment of various respiratory diseases and summarizes the chemical structural modifications and the various delivery systems for siRNA. Finally, we conclude the latest clinical application research for inhaled siRNA formulations and discuss the potential difficulty in efficient clinical application.

Evaluating the Knockdown Activity of MALAT1 ENA Gapmers In Vitro

Antisense oligonucleotides (ASOs) are widely used for the identification of gene functions and regulation of genes involved in different diseases for therapeutic purposes. For in vitro evaluation of the knockdown activity of gapmer ASOs, we often use lipofection or electroporation to deliver gapmer ASOs into the cells. Here, we describe a method for evaluating the knockdown activity of gapmer ASOs by a cell-free uptake mechanism, termed as gymnosis, using MALAT1 gapmer ASOs modified with 2'-O-methoxyethyl RNA (2'-MOE) or 2'-O,4'-C-ethylene-bridged nucleic acid (ENA). This method is robust because it does not involve the use of any transfection reagent and has minimal effects on cell growth. Further, we describe a convenient technique for performing one-step reverse transcription and real-time qPCR using cell lysates without RNA extraction. Data for up to 96 samples can be obtained following these methods.

Antisense Oligonucleotides as Potential Therapeutics for Type 2 Diabetes

Type 2 diabetes (T2D) is a chronic metabolic disorder characterized by persistent hyperglycemia resulting from inefficient signaling and insufficient production of insulin. Conventional management of T2D has largely relied on small molecule-based oral hypoglycemic medicines, which do not halt the progression of the disease due to limited efficacy and induce adverse effects as well. To this end, antisense oligonucleotide has attracted immense attention in developing antidiabetic agents because of their ability to downregulate the expression of disease-causing genes at the RNA and protein level. To date, seven antisense agents have been approved by the United States Food and Drug Administration for therapies of a variety of human maladies, including genetic disorders. Herein, we provide a comprehensive review of antisense molecules developed for suppressing the causative genes believed to be responsible for insulin resistance and hyperglycemia toward preventing and treating T2D.

Therapeutically Significant MicroRNAs in Primary and Metastatic Brain Malignancies

Simple Summary

The overall survival of brain cancer patients remains grim, with conventional therapies such as chemotherapy and radiotherapy only providing marginal benefits to patient survival. Cancers are complex, with multiple pathways being dysregulated simultaneously. Non-coding RNAs such as microRNA (miRNAs) are gaining importance due to their potential in regulating a variety of targets implicated in the pathology of cancers. This could be leveraged for the development of targeted and personalized therapies for cancers. Since miRNAs can upregulate and/or downregulate proteins, this review aims to understand the role of these miRNAs in primary and metastatic brain cancers. Here, we discuss the regulatory mechanisms of ten miRNAs that are highly dysregulated in glioblastoma and metastatic brain tumors. This will enable researchers to develop miRNA-based targeted cancer therapies and identify potential prognostic biomarkers.

Abstract

Brain cancer is one among the rare cancers with high mortality rate that affects both children and adults. The most aggressive form of primary brain tumor is glioblastoma. Secondary brain tumors most commonly metastasize from primary cancers of lung, breast, or melanoma. The five-year survival of primary and secondary brain tumors is 34% and 2.4%, respectively. Owing to poor prognosis, tumor heterogeneity, increased tumor relapse, and resistance to therapies, brain cancers have high mortality and poor survival rates compared to other cancers. Early diagnosis, effective targeted treatments, and improved prognosis have the potential to increase the survival rate of patients with primary and secondary brain malignancies. MicroRNAs (miRNAs) are short noncoding RNAs of approximately 18–22 nucleotides that play a significant role in the regulation of multiple genes. With growing interest in the development of miRNA-based therapeutics, it is crucial to understand the differential role of these miRNAs in the given cancer scenario. This review focuses on the differential expression of ten miRNAs (miR-145, miR-31, miR-451, miR-19a, miR-143, miR-125b, miR-328, miR-210, miR-146a, and miR-126) in glioblastoma and brain metastasis. These miRNAs are highly dysregulated in both primary and metastatic brain tumors, which necessitates a better understanding of their role in these cancers. In the context of the tumor microenvironment and the expression of different genes, these miRNAs possess both oncogenic and/or tumor-suppressive roles within the same cancer.

An improved synthesis of 2'-O,4'-C-ethylene nucleic acid (ENA) and thermodynamic studies of duplex formation containing the guanosine ENA unit

Oligonucleotides containing 2'-O,4'-C-ethylene nucleic acids (ENA) have been proven highly effective for antisense therapeutics. 2'-O,4'-C-Ethyleneguanosine and its phosphoramidite were previously obtained from 3,5-di-O-benzy1-4-C-(p-tolulenesulfonyloxyethyl)-1,2-di-O-acetyl-α-D-erythropentofuranose by glycosylation, but with limited efficiency. Using 3,5-di-O-benzy1-4-C-(2-t-butyldiphenylsilyloxyethyl)-1,2-di-O-acetyl-α-D-erythropentofuranose as an alternative substrate, we developed several methods to obtain 2'-O,4'-C-ethyleneguanosine derivatives with much higher yields than previously reported. These methods were also applicable for the synthesis of 2'-O,4'-C-ethyleneadenosine and 2'-O,4'-C-ethylene-5-methyluridine derivatives. Moreover, we investigated the thermodynamic benefit of DNA strands containing 2'-O,4'-C-ethyleneguanosines during duplex formation with complementary RNA. Only a single modification by the nucleoside resulted in a 10-fold greater binding constant of the DNA/RNA duplex.

Synthesis of ENA Nucleotides and ENA Oligonucleotides

2'-O,4'-C-Ethylene-bridged nucleic acid (ENA) is a sugar-modified oligonucleotide with an ethylene bridge between the 2'-oxygen and 4'-carbon of ribose. ENA not only has as high binding affinity to complementary RNA as conventional bridged/locked nucleic acid, but also has much higher nuclease resistance in plasma, which makes it a promising candidate for antisense therapeutics. This unit presents detailed protocols for the synthesis and characterization of ENA nucleosides and oligonucleotides. © 2018 by John Wiley & Sons, Inc.

Antisense oligonucleotides containing conformationally constrained 2',4'-(N-methoxy)aminomethylene and 2',4'-aminooxymethylene and 2'-O,4'-C-aminomethylene bridged nucleoside analogues show improved potency in animal models

To identify chemistries and strategies to improve the potency of MOE second generation ASOs, we have evaluated gapmer antisense oligonucleotides containing BNAs having N-O bonds. These modifications include N-MeO-amino BNA, N-Me-aminooxy BNA, 2',4'-BNA(NC)[NMe], and 2',4'-BNA(NC) bridged nucleoside analogues. These modifications provided increased thermal stability and improved in vitro activity compared to the corresponding ASO containing the MOE modification. Additionally, ASOs containing N-MeO-amino BNA, N-Me-aminooxy BNA, and 2',4'-BNA(NC)[NMe] modifications showed improved in vivo activity (>5-fold) compared to MOE ASO. Importantly, toxicity parameters, such as AST, ALT, liver, kidney, and body weights, were found to be normal for N-MeO-amino BNA, N-Me-aminooxy BNA, and 2',4'-BNA(NC)[NMe] ASO treated animals. The data generated in these experiments suggest that N-MeO-amino BNA, N-Me-aminooxy BNA, and 2',4'-BNA(NC)[NMe] are useful modifications for applications in both antisense and other oligonucleotide based drug discovery efforts.

Fine-tuning of ENA gapmers as antisense oligonucleotides for sequence-specific inhibition

For gene validation and the development of oligonucleotide agents, 2'-O,4'-C-ethylene-bridged nucleic acid (ENA) antisense gapmers are widely available. An in vitro Escherichia coli RNase H reaction analysis using ENA gapmers and an RNA oligonucleotide with mouse peptidylarginine deiminase 4 (PADI4) gene sequences revealed that the RNA oligonucleotide was specifically cleaved in the only reported case of the use of an ENA gapmer with an antisense sequence. On the other hand, duplexes of the full-length transcripts of PADI4 mRNA and ENA gapmers with a wide DNA window were cleaved not only at the target site, but also at nontarget sites by RNase H derived from partial base-pairing between the transcript and the ENA gapmer. When the DNA window region of the ENA gapmer was shortened to 5 or 6 nucleotides, the nontarget cleavage was effectively diminished. Moreover, the specific inhibition of PADI4 mRNA expression was observed in the cotransfection of PADI4 cDNA and ENA gapmers containing a short DNA region into NIH3T3 cells. These results demonstrated that ENA gapmers with a short DNA region improved the sequence-specificity of mRNA downregulation. These optimized ENA gapmers could reduce the "off-target" effect and be applicable to gene validation and oligonucleotide therapeutics.

The versatility of oligonucleotides as potential therapeutics

Oligonucleotides can in a variety of ways inhibit gene expression by interfering with translation. Oligonucleotides that are complementary to a target mRNA, antisense oligonucleotides, can prevent translation either by cleaving the target or by physically blocking the process. Additionally, oligonucleotides can correct the undesired splicing of pre-mRNA. RNA interference using double-stranded oligoribonucleotides also results in cleavage of the target mRNA. Catalytically competent ribozymes and DNAzymes can have the same effect. Even with no RNA as target, oligonucleotides can be selected as aptamers to bind to any protein to inhibit its activity. Moreover, oligonucleotides can act as decoys particularly for transcription factors to prevent binding to the promoter. A different mode of action is the activation of Toll-like receptors to induce an immune response. Several pathways for drug development are still in their infancy, for example microRNAs and antagomirs.

Antisense oligonucleotides containing locked nucleic acid improve potency but cause significant hepatotoxicity in animals

A series of antisense oligonucleotides (ASOs) containing either 2′-O-methoxyethylribose (MOE) or locked nucleic acid (LNA) modifications were designed to investigate whether LNA antisense oligonucleotides (ASOs) have the potential to improve upon MOE based ASO therapeutics. Some, but not all, LNA containing oligonucleotides increased potency for reducing target mRNA in mouse liver up to 5-fold relative to the corresponding MOE containing ASOs. However, they also showed profound hepatotoxicity as measured by serum transaminases, organ weights and body weights. This toxicity was evident for multiple sequences targeting three different biological targets, as well as in mismatch control sequences having no known mRNA targets. Histopathological evaluation of tissues from LNA treated animals confirmed the hepatocellular involvement. Toxicity was observed as early as 4 days after a single administration. In contrast, the corresponding MOE ASOs showed no evidence for toxicity while maintaining the ability to reduce target mRNA. These studies suggest that while LNA ASOs have the potential to improve potency, they impose a significant risk of hepatotoxicity.