Facile access to 4'-(N-acylsulfonamide) modified nucleosides and evaluation of their inhibitory activity against SARS-CoV-2 RNA cap N7-guanine-methyltransferase nsp14.

N-Acylsulfonamides possess an additional carbonyl function compared to their sulfonamide analogues. Due to their unique physico-chemical properties, interest in molecules containing the N-acylsulfonamide moiety and especially nucleoside derivatives is growing in the field of medicinal chemistry. The recent renewal of interest in antiviral drugs derived from nucleosides containing a sulfonamide function has led us to evaluate the therapeutic potential of N-acylsulfonamide analogues. While these compounds are usually obtained by a difficult acylation of sulfonamides, we report here the easy and efficient synthesis of 20 4'-(N-acylsulfonamide) adenosine derivatives via the sulfo-click reaction. The target compounds were obtained from thioacid and sulfonyl azide synthons in excellent yields and were evaluated as potential inhibitors of the SARS-CoV-2 RNA cap N7-guanine-methyltransferase nsp14.

Exploitation of N-Gene of SARS-CoV-2 to Develop a New Rapid Assay by ASOs@AuNPs.

A naked-eye (equipment-free), label-free (cost-effective), and RNA extraction-free (to speed up) method for SARS-CoV-2 (as a case study of RNA viruses) detection is developed. Here, the DNA is being used as a template for in situ formation of anisotropic gold nanoparticles (AuNPs) without any chemical modification or DNA labeling. In this study, synthesized AuNPs for the direct detection of N-gene (nucleocapsid phosphoprotein) of SARS-CoV-2 are exploited. To this aim, antisense oligonucleotides (ASOs) with an extra poly guanine tail (G12) were designed. Thus, in the presence of its viral target RNA gene and ASOs@AuNPs-RNA hybridization, there was a red shift in its localized surface plasmon resonance (LSPR), and the intensity of the LSPR peak at 690 nm of throat swab samples was compared to the threshold cycle (Ct) of a reverse-transcriptase real-time polymerase chain reaction (RT-qPCR) (as a gold standard). Results suggested that the plasmonic biosensor can detect a very low amount of SARS-CoV-2 with a detection limit close to RT-qPCR. Simplicity of the new conjugation method with hybridization and annealing without amplification and denaturation steps enabled it to perform in a microfluidic paper-based analytical device.

Covalent Catalytic Strategies for Enzymes That Modify RNA Molecules on their Tripartite Building Blocks.

The tripartite structures of the four 5'-nucleotide monophosphate (NMP) building blocks in all RNAs enable enzyme-catalyzed chemical modifications to three types of sites: the heterocyclic bases via N- and C-methylations and other alkylations, conversion of the N-glycoside linkages of the uridine moiety to the C-C glycoside link in pseudouridines, and the phosphodiester-mediated processes of 5'-capping, splicing, and 3'-tailing of premRNAs. We examine known cases for enzymatic covalent catalytic strategies that entail transient formation and breakdown of covalent enzyme-RNA adducts in each catalytic cycle. One case involves generation of the required carbon nucleophile during C5 methylation of cytosine residues in RNAs. A second examines the mechanism proposed for pseudouridine synthases and for replacement of a guanine residue in tRNAs by queuosine. The third category involves phosphoric anhydride and phosphodiester chemistry by which viral RNAs encode enzymes for making their own mRNA 5'-caps. This strategy includes the recent finding that the SARS-CoV2 proteins assemble a canonical 5',5'-GTP cap on their 28 900 nucleotide genomic RNA to enable its translation as an mRNA by host translational machinery by way of a covalent RNA-viral enzyme intermediate.

Risk of Hepatitis B Virus Reactivation in Rheumatoid Arthritis Patients Undergoing Tocilizumab-Containing Treatment.

BACKGROUND AND AIM: To investigate the risk of hepatitis B virus reactivation in patients undergoing long-term tocilizumab therapy for rheumatoid arthritis. METHOD: From January 2011 through August 2019, a total of 97 patients were enrolled in this retrospective study. Clinical data, comedications, and the occurrence of HBV reactivation were recorded. RESULTS: Seven patients were HBsAg+ (7.2%), 64 were HBsAg-/HBcAb+ (65.9%), and 26 were HBsAg-/HBcAb- (26.8%). The median disease follow-up time was 9 years. TCZ was administered for a median of 29 months. Four patients (4.1%) experienced HBV reactivation after tocilizumab therapy. Of the 7 HBsAg+ patients, 4 received antiviral prophylaxis and had no HBV reactivation; the remaining 3 patients did not receive antiviral prophylaxis, and all 3 (100%) experienced HBV reactivation and hepatitis flare-up. Hyperbilirubinemia occurred in 2 of these 3 patients, with mild prothrombin time prolongation in one. After salvage entecavir treatment, all patients had a favorable outcome. Of the 64 HBsAg-/HBcAb+ patients, only one became positive for serum HBV DNA (2.5 × 107 IU/mL) after 18 months of tocilizumab treatment (1.6%; 1/64). This patient was immediately treated with entecavir, which prevented hepatitis flare-up. CONCLUSIONS: Tocilizumab is widely used in treating rheumatoid arthritis and has the potential to reduce the mortality rate among severe COVID-19 patients. However, HBV reactivation needs to be considered. HBsAg+ patients have a high risk of HBV reactivation, which could be prevented by antiviral prophylaxis. Although the risk of reactivation is low in HBsAg-/HBcAb+ patients, strict monitoring is necessary.

Products of Oxidative Guanine Damage Form Base Pairs with Guanine.

Among the natural bases, guanine is the most oxidizable base. The damage caused by oxidation of guanine, commonly referred to as oxidative guanine damage, results in the formation of several products, including 2,5-diamino-4H-imidazol-4-one (Iz), 2,2,4-triamino-5(2H)-oxazolone (Oz), guanidinoformimine (Gf), guanidinohydantoin/iminoallantoin (Gh/Ia), spiroiminodihydantoin (Sp), 5-carboxamido-5-formamido-2-iminohydantoin (2Ih), urea (Ua), 5-guanidino-4-nitroimidazole (NI), spirodi(iminohydantoin) (5-Si and 8-Si), triazine, the M+7 product, other products by peroxynitrite, alkylated guanines, and 8,5'-cyclo-2'-deoxyguanosine (cG). Herein, we summarize the present knowledge about base pairs containing the products of oxidative guanine damage and guanine. Of these products, Iz is involved in G-C transversions. Oz, Gh/Ia, and Sp form preferably Oz:G, Gh/Ia:G, and Sp:G base pairs in some cases. An involvement of Gf, 2Ih, Ua, 5-Si, 8-Si, triazine, the M+7 product, and 4-hydroxy-2,5-dioxo-imidazolidine-4-carboxylic acid (HICA) in G-C transversions requires further experiments. In addition, we describe base pairs that target the RNA-dependent RNA polymerase (RdRp) of RNA viruses and describe implications for the 2019 novel coronavirus (SARS-CoV-2): When products of oxidative guanine damage are adapted for the ribonucleoside analogs, mimics of oxidative guanine damages, which can form base pairs, may become antiviral agents for SARS-CoV-2.

Drug repurposing of anti-infective clinical drugs: Discovery of two potential anti-cytokine storm agents.

Coronavirus Disease 2019 (COVID-19) caused by Severe Acute Respiratory Syndrome Coronavirus -2 (SARS-CoV-2) has been widely spread in the world with a high mortality. Cytokine storm syndrome (CSS) and acute lung injury caused by SARS-CoV-2 infection severely threaten the patients. With the purpose to find effective and low-toxic drugs to mitigate CSS, entecavir and imipenem were identified to reduce TNF-α using a LPS-induced macrophage model from the anti-infective drug library. Entecavir and imipenem efficiently suppressed the release of inflammatory cytokines by partly intervention of NF-κB activity. The acute lung injury was also alleviated and the survival time was prolonged in mice. In addition, entecavir and imipenem inhibited the release of TNF-α and IL-10 in human peripheral blood mononuclear cells (hPBMCs). Collectively, we proposed that entecavir and imipenem might be candidates for the treatment of CSS.