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The pandemic caused by the novel betacoronavirus SARS-CoV-2 has already claimed more than 3.5 million lives. Despite the development and use of anti-COVID-19 vaccines, the disease remains a major public health challenge throughout the world. Large-scale screening of the drugs already approved for the treatment of other viral, bacterial, and parasitic infections, as well as autoimmune, oncological, and other diseases is currently underway as part of their repurposing for development of effective therapeutic agents against SARS-CoV-2. In this work, we present the results of a phenotypic screening of libraries of modified heterocyclic bases and 5-norcarbocyclic nucleoside analogs previously synthesized by us. We identified two leading compounds with apparent potential to inhibit SARS-CoV-2 replication and EC50 values in a range of 2070 M. The structures of these compounds can be further optimized to develop an antiviral drug.

Long-term antiviral treatment of chronic hepatitis B patients has been proven to be beneficial in reducing liver-related complications. However, lengthy periods of daily administration of medication have some inevitable drawbacks, including decreased medication adherence, increased cost of treatment, and possible long-term side effects. Currently, discontinuation of antiviral agent has become the strategy of interest to many hepatologists, as it might alleviate the aforementioned drawbacks and increase the probability of achieving functional cure. This review focuses on the current evidence of the outcomes following stopping antiviral treatment and the factors associated with subsequent hepatitis B virus relapse, hepatitis B surface antigen clearance, and unmet needs.

SUMMARY The development of effective antiviral therapy for COVID-19 is critical for those awaiting vaccination, as well as for those who do not respond robustly to vaccination. This review summarizes 1 year of progress in the race to develop antiviral therapies for COVID-19, including research spanning preclinical and clinical drug development efforts, with an emphasis on antiviral compounds that are in clinical development or that are high priorities for clinical development. The review is divided into sections on compounds that inhibit SARS-CoV-2 enzymes, including its polymerase and proteases; compounds that inhibit virus entry, including monoclonal antibodies; interferons; and repurposed drugs that inhibit host processes required for SARS-CoV-2 replication. The review concludes with a summary of the lessons to be learned from SARS-CoV-2 drug development efforts and the challenges to continued progress.

We report the convergent synthesis of bicyclo[3.1.0]hexanes possessing an all-carbon quaternary center via a (3 + 2) annulation of cyclopropenes with cyclopropylanilines. Using an organic or an iridium photoredox catalyst and blue LED irradiation, good yields were obtained for a broad range of cyclopropene and cyclopropylaniline derivatives. The reaction was highly diastereoselective when using difluorocyclopropenes together with a removable substituent on the cyclopropylaniline, giving access to important building blocks for medicinal chemistry. With efficient methods existing for the synthesis of both reaction partners, our method grants a fast access to highly valuable bicyclic scaffolds with three contiguous stereocenters.

Chemical modification of sugars and nucleosides has a long history of producing compounds with improved selectivity and efficacy. In this study, several modified sugars (2–3) and ribonucleoside analogs (4–8) have been synthesized from α-d-glucose in a total of 21 steps. The compounds were tested for peripheral anti-nociceptive characteristics in the acetic acid-induced writhing assay in mice, where compounds 2, 7, and 8 showed a significant reduction in the number of writhes by 56%, 62%, and 63%, respectively. The compounds were also tested for their cytotoxic potential against human HeLa cell line via trypan blue dye exclusion test followed by cell counting kit-8 (CCK-8) assay. Compound 6 demonstrated significant cytotoxic activity with an IC50 value of 54 µg/mL. Molecular docking simulations revealed that compounds 2, 7, and 8 had a comparable binding affinity to cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) enzymes. Additionally, the bridged nucleoside analogs 7 and 8 potently inhibited adenosine kinase enzyme as well, which indicates an alternate mechanistic pathway behind their anti-nociceptive action. Cytotoxic compound 6 demonstrated strong docking with cancer drug targets human cytidine deaminase, proto-oncogene tyrosine-protein kinase Src, human thymidine kinase 1, human thymidylate synthase, and human adenosine deaminase 2. This is the first ever reporting of the synthesis and analgesic property of compound 8 and the cytotoxic potential of compound 6.

Liguo Wang,1,* Peng Chen,2,* Chao Zheng3 1Department of Infectious Diseases, First Affiliated Hospital of Xiamen University, Fujian Province, China; 2Department of Emergency, Xinglin Hospital, First Affiliated Hospital of Xiamen University, Fujian Province, China; 3Department of Respiratory, First Affiliated Hospital of Xiamen University, Fujian Province, China *These authors contributed equally to this work Objective: The objective of this study was to explore the risk factors of poor adherence of nucleoside analogs (NUC) treatment in chronic hepatitis B (CHB) patients and the virological changes in patients with poor adherence. Subjects and methods: A total of 205 CHB patients were enrolled. The patients’ demographic data and family history were collected. NUC adherence was calculated every 12 weeks as follows: number of NUC tablets taken by the patients was divided by the number of NUC tablets prescribed. NUC adherence> 90% was defined as good adherence of NUC treatment. Results: NUC adherence of male patients was significantly lower than that of female patients. Adherence among patients with previous NUC treatment was poorer than that of patients without previous NUC treatment. Multivariate analysis indicated that female gender (OR =0.367,P=0.013) was the protective factor for NUC adherence in CHB patients, while pretreatment with NUC was the risk factor for NUC adherence (OR =3.209,P=0.002). A total of six patients in the good adherence group experienced virological breakthroughs while 15 of 77 patients in the poor adherence group experienced virological breakthroughs (P=0.001). Similar trends were observed in NUC resistance. Four of the 128 patients with good adherence developed NUC resistance while nine of the 77 patients with poor adherence developed resistance (P=0.015). Multivariate analysis suggested that pretreatment with NUC (OR =3.133,P=0.031), NUC drugs (OR = 3.951,P=0.010), and adherence (OR =2.749,P=0.046) were independent risk factors associated with virological breakthroughs and that NUC drugs (OR =7.083, P=0.005) and poor adherence (OR =4.951,P=0.009) were independent risk factors for NUC resistance. Conclusion: Male gender and pretreatment with NUC were risk factors associated with NUC adherence. Poor NUC adherence is more likely to induce virological breakthroughs and NUC resistance. For patients with poor NUC adherence, it is necessary to give timely education to improve treatment adherence. Keywords: chronic hepatitis B, adherence, nucleoside analogs, virological breakthroughs, risk factors

Remdesivir (RDV, GS-5734), the first FDA-approved antiviral for the treatment of COVID-19, is a single diastereomer monophosphoramidate prodrug of an adenosine analogue. It is intracellularly metabolized into the active triphosphate form, which in turn acts as a potent and selective inhibitor of multiple viral RNA polymerases., Remdesivir (RDV, GS-5734), the first FDA-approved antiviral for the treatment of COVID-19, is a single diastereomer monophosphoramidate prodrug of an adenosine analogue. It is intracellularly metabolized into the active triphosphate form, which in turn acts as a potent and selective inhibitor of multiple viral RNA polymerases. RDV has broad-spectrum activity against members of the coronavirus family, such as SARS-CoV-2, SARS-CoV, and MERS-CoV, as well as filoviruses and paramyxoviruses. To assess the potential for off-target toxicity, RDV was evaluated in a set of cellular and biochemical assays. Cytotoxicity was evaluated in a set of relevant human cell lines and primary cells. In addition, RDV was evaluated for mitochondrial toxicity under aerobic and anaerobic metabolic conditions, and for the effects on mitochondrial DNA content, mitochondrial protein synthesis, cellular respiration, and induction of reactive oxygen species. Last, the active 5′-triphosphate metabolite of RDV, GS-443902, was evaluated for potential interaction with human DNA and RNA polymerases. Among all of the human cells tested under 5 to 14 days of continuous exposure, the 50% cytotoxic concentration (CC50) values of RDV ranged from 1.7 to >20 μM, resulting in selectivity indices (SI, CC50/EC50) from >170 to 20,000, with respect to RDV anti-SARS-CoV-2 activity (50% effective concentration [EC50] of 9.9 nM in human airway epithelial cells). Overall, the cellular and biochemical assays demonstrated a low potential for RDV to elicit off-target toxicity, including mitochondria-specific toxicity, consistent with the reported clinical safety profile.

Coronavirus disease 2019 (COVID-19) is a serious illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 or CoV-2). Some reports claimed certain nucleoside analogs to be active against CoV-2 and thus needed confirmation. Here, we evaluated a panel of compounds and identified novel nucleoside analogs with antiviral activity against CoV-2 and HCoV-OC43 while ruling out others. Of significance, sofosbuvir demonstrated no antiviral effect against CoV-2, and its triphosphate did not inhibit CoV-2 RNA polymerase.

Coronaviridae is a peculiar viral family, with a very large RNA genome and characteristic appearance, endowed with remarkable tendency to transfer from animals to humans. Since the beginning of the 21st century, three highly transmissible and pathogenic coronaviruses have crossed the species barrier and caused deadly pneumonia, inflicting severe outbreaks and causing human health emergencies of inconceivable magnitude. Indeed, in the past two decades, two human coronaviruses emerged causing serious respiratory illness: severe acute respiratory syndrome coronavirus (SARS-CoV-1) and Middle Eastern respiratory syndrome coronavirus (MERS-CoV), causing more than 10,000 cumulative cases, with mortality rates of 10 % for SARS-CoV-1 and 34.4 % for MERS-CoV. More recently, the severe acute respiratory syndrome coronavirus virus 2 (SARS-CoV-2) has emerged in China and has been identified as the etiological agent of the recent COVID-19 pandemic outbreak. It has rapidly spread throughout the world, causing nearly 22 million cases and ∼ 770,000 deaths worldwide, with an estimated mortality rate of ∼3.6 %, hence posing serious challenges for adequate and effective prevention and treatment. Currently, with the exception of the nucleotide analogue prodrug remdesivir, and despite several efforts, there is no known specific, proven, pharmacological treatment capable of efficiently and rapidly inducing viral containment and clearance of SARS-CoV-2 infection as well as no broad-spectrum drug for other human pathogenic coronaviruses. Another confounding factor is the paucity of molecular information regarding the tendency of coronaviruses to acquire drug resistance, a gap that should be filled in order to optimize the efficacy of antiviral drugs. In this light, the present review provides a systematic update on the current knowledge of the marked global efforts towards the development of antiviral strategies aimed at coping with the infection sustained by SARS-CoV-2 and other human pathogenic coronaviruses, displaying drug resistance profiles. The attention has been focused on antiviral drugs mainly targeting viral protease, RNA polymerase and spike glycoprotein, that have been tested in vitro and/or in clinical trials as well as on promising compounds proven to be active against coronaviruses by an in silico drug repurposing approach. In this respect, novel insights on compounds, identified by structure-based virtual screening on the DrugBank database endowed by multi-targeting profile, are also reported. We specifically identified 14 promising compounds characterized by a good in silico binding affinity towards, at least, two of the four studied targets (viral and host proteins). Among which, ceftolozane and NADH showed the best multi-targeting profile, thus potentially reducing the emergence of resistant virus strains. We also focused on potentially novel pharmacological targets for the development of compounds with anti-pan coronavirus activity. Through the analysis of a large set of viral genomic sequences, the current review provides a comprehensive and specific map of conserved regions across human coronavirus proteins which are essential for virus replication and thus with no or very limited tendency to mutate. Hence, these represent key druggable targets for novel compounds against this virus family. In this respect, the identification of highly effective and innovative pharmacological strategies is of paramount importance for the treatment and/or prophylaxis of the current pandemic but potentially also for future and unavoidable outbreaks of human pathogenic coronaviruses.

ATI-2173 is a novel liver-targeted molecule designed to deliver the 5′-monophosphate of clevudine for the treatment of chronic hepatitis B infection. Unlike other nucleos(t)ides, the active clevudine-5′-triphosphate is a noncompetitive, non-chain-terminating inhibitor of hepatitis B virus (HBV) polymerase that delivers prolonged reduction of viremia in both a woodchuck HBV model and in humans for up to 6 months after cessation of treatment. However, long-term clevudine treatment was found to exhibit reversible skeletal myopathy in a small subset of patients and was subsequently discontinued from development., ATI-2173 is a novel liver-targeted molecule designed to deliver the 5′-monophosphate of clevudine for the treatment of chronic hepatitis B infection. Unlike other nucleos(t)ides, the active clevudine-5′-triphosphate is a noncompetitive, non-chain-terminating inhibitor of hepatitis B virus (HBV) polymerase that delivers prolonged reduction of viremia in both a woodchuck HBV model and in humans for up to 6 months after cessation of treatment. However, long-term clevudine treatment was found to exhibit reversible skeletal myopathy in a small subset of patients and was subsequently discontinued from development. ATI-2173 was designed by modifying clevudine with a 5′-phosphoramidate to deliver the 5′-monophosphate to the liver. Bypassing the first phosphorylation step of clevudine, the 5′-monophosphate is converted to the active 5′-triphosphate in the liver. ATI-2173 is a selective inhibitor of HBV with an anti-HBV 50% effective concentration (EC50) of 1.31 nM in primary human hepatocytes, with minimal to no toxicity in hepatocytes, skeletal muscle, liver, kidney, bone marrow, and cardiomyocytes. ATI-2173 activity was decreased by viral polymerase mutations associated with entecavir, lamivudine, and adefovir resistance, but not capsid inhibitor resistance mutations. A single oral dose of ATI-2173 demonstrated 82% hepatic extraction, no food effect, and greatly reduced peripheral exposure of clevudine compared with equimolar oral dosing of clevudine. Despite reduced plasma clevudine exposure, liver concentrations of the 5′-triphosphate were equivalent following ATI-2173 versus clevudine administration. By selectively delivering the 5′-monophosphate to the liver, while retaining the unique anti-HBV activity of the 5′-triphosphate, ATI-2173 may provide an improved pharmacokinetic profile for clinical use, reducing systemic exposure of clevudine and potentially eliminating skeletal myopathy.

// Jung-Suk Choi 1 , Seol Kim 2 , Edward Motea 3 and Anthony Berdis 1, 2, 4, 5 1 Department of Chemistry, Cleveland State University, Cleveland, OH 44115, USA 2 Department of Biological, Geological, and Environmental Sciences, Cleveland State University, Cleveland, OH 44115, USA 3 Departments of Radiation Oncology and Pharmacology, Harold C. Simmons Comprehensive Cancer Center, UT Southwestern Medical Center, Dallas, TX 75390, USA 4 Center for Gene Regulation in Health and Disease, Cleveland State University, Cleveland, OH 44115, USA 5 Case Comprehensive Cancer Center, Cleveland, OH 44106, USA Correspondence to: Anthony Berdis, email: a.berdis@csuohio.edu Keywords: DNA damage, DNA polymerization, chemotherapy, nucleoside analogs, leukemia Received: February 24, 2017 Accepted: April 11, 2017 Published: April 19, 2017 ABSTRACT Anti-cancer agents exert therapeutic effects by damaging DNA. Unfortunately, DNA polymerases can effectively replicate the formed DNA lesions to cause drug resistance and create more aggressive cancers. To understand this process at the cellular level, we developed an artificial nucleoside that visualizes the replication of damaged DNA to identify cells that acquire drug resistance through this mechanism. Visualization is achieved using "click" chemistry to covalently attach azide-containing fluorophores to the ethynyl group present on the nucleoside analog after its incorporation opposite damaged DNA. Flow cytometry and microscopy techniques demonstrate that the extent of nucleotide incorporation into genomic DNA is enhanced by treatment with DNA damaging agents. In addition, this nucleoside analog inhibits translesion DNA synthesis and synergizes the therapeutic activity of certain anti-cancer agents such as temozolomide. The combined diagnostic and therapeutic activities of this synthetic nucleoside analog represent a new paradigm in personalized medicine.

// Jana Zemanova 1 , Ondrej Hylse 2, 3 , Jana Collakova 4, 5 , Pavel Vesely 5 , Alexandra Oltova 1 , Marek Borsky 1 , Kristina Zaprazna 6 , Marie Kasparkova 1 , Pavlina Janovska 7 , Jan Verner 1 , Jiri Kohoutek 8 , Marta Dzimkova 8 , Vitezslav Bryja 7, 9 , Zuzana Jaskova 1 , Yvona Brychtova 1 , Kamil Paruch 2, 3 , Martin Trbusek 1 1 Department of Internal Medicine – Hematology and Oncology, University Hospital Brno and Faculty of Medicine, Masaryk University, Brno, Czech Republic 2 Center of Biomolecular and Cellular Engineering, International Clinical Research Center, St. Anne’s University Hospital, Brno, Czech Republic 3 Department of Chemistry, CZ Openscreen, Faculty of Science, Masaryk University, Brno, Czech Republic 4 Institute of Physical Engineering, Faculty of Mechanical Engineering, Brno University of Technology, Brno, Czech Republic 5 CEITEC – Central European Institute of Technology, Brno University of Technology, Brno, Czech Republic 6 CEITEC – Central European Institute of Technology, Masaryk University, Brno, Czech Republic 7 Institute of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic 8 Department of Chemistry and Toxicology, Veterinary Research Institute, Brno, Czech Republic 9 Department of Cytokinetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, Czech Republic Correspondence to: Martin Trbusek, email: m.trbusek@volny.cz Keywords: checkpoint kinase 1/Chk1, SCH900776, nucleoside analogs, chronic lymphocytic leukemia, TP53 Received: February 01, 2016 Accepted: August 08, 2016 Published: August 19, 2016 ABSTRACT Treatment options for TP53 -mutated lymphoid tumors are very limited. In experimental models, TP53 -mutated lymphomas were sensitive to direct inhibition of checkpoint kinase 1 (Chk1), a pivotal regulator of replication. We initially tested the potential of the highly specific Chk1 inhibitor SCH900776 to synergize with nucleoside analogs (NAs) fludarabine, cytarabine and gemcitabine in cell lines derived from B-cell malignancies. In p53-proficient NALM-6 cells, SCH900776 added to NAs enhanced signaling towards Chk1 (pSer317/pSer345), effectively blocked Chk1 activation (Ser296 autophosphorylation), increased replication stress (p53 and γ-H2AX accumulation) and temporarily potentiated apoptosis. In p53-defective MEC-1 cell line representing adverse chronic lymphocytic leukemia (CLL), Chk1 inhibition together with NAs led to enhanced and sustained replication stress and significantly potentiated apoptosis. Altogether, among 17 tested cell lines SCH900776 sensitized four of them to all three NAs. Focusing further on MEC-1 and co-treatment of SCH900776 with fludarabine, we disclosed chromosome pulverization in cells undergoing aberrant mitoses. SCH900776 also increased the effect of fludarabine in a proportion of primary CLL samples treated with pro-proliferative stimuli, including those with TP53 disruption. Finally, we observed a fludarabine potentiation by SCH900776 in a T-cell leukemia 1 ( TCL1 )-driven mouse model of CLL. Collectively, we have substantiated the significant potential of Chk1 inhibition in B-lymphoid cells.

Emerging coronaviruses (CoVs) cause severe disease in humans, but no approved therapeutics are available. The CoV nsp14 exoribonuclease (ExoN) has complicated development of antiviral nucleosides due to its proofreading activity. We recently reported that the nucleoside analogue GS-5734 (remdesivir) potently inhibits human and zoonotic CoVs in vitro and in a severe acute respiratory syndrome coronavirus (SARS-CoV) mouse model. However, studies with GS-5734 have not reported resistance associated with GS-5734, nor do we understand the action of GS-5734 in wild-type (WT) proofreading CoVs. Here, we show that GS-5734 inhibits murine hepatitis virus (MHV) with similar 50% effective concentration values (EC50) as SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV). Passage of WT MHV in the presence of the GS-5734 parent nucleoside selected two mutations in the nsp12 polymerase at residues conserved across all CoVs that conferred up to 5.6-fold resistance to GS-5734, as determined by EC50. The resistant viruses were unable to compete with WT in direct coinfection passage in the absence of GS-5734. Introduction of the MHV resistance mutations into SARS-CoV resulted in the same in vitro resistance phenotype and attenuated SARS-CoV pathogenesis in a mouse model. Finally, we demonstrate that an MHV mutant lacking ExoN proofreading was significantly more sensitive to GS-5734. Combined, the results indicate that GS-5734 interferes with the nsp12 polymerase even in the setting of intact ExoN proofreading activity and that resistance can be overcome with increased, nontoxic concentrations of GS-5734, further supporting the development of GS-5734 as a broad-spectrum therapeutic to protect against contemporary and emerging CoVs., IMPORTANCE Coronaviruses (CoVs) cause severe human infections, but there are no approved antivirals to treat these infections. Development of nucleoside-based therapeutics for CoV infections has been hampered by the presence of a proofreading exoribonuclease. Here, we expand the known efficacy of the nucleotide prodrug remdesivir (GS-5734) to include a group β-2a CoV. Further, GS-5734 potently inhibits CoVs with intact proofreading. Following selection with the GS-5734 parent nucleoside, 2 amino acid substitutions in the nsp12 polymerase at residues that are identical across CoVs provide low-level resistance to GS-5734. The resistance mutations decrease viral fitness of MHV in vitro and attenuate pathogenesis in a SARS-CoV animal model of infection. Together, these studies define the target of GS-5734 activity and demonstrate that resistance is difficult to select, only partial, and impairs fitness and virulence of MHV and SARS-CoV, supporting further development of GS-5734 as a potential effective pan-CoV antiviral.

This review describes the current state of discovery of past most important nucleoside and nucleotide prodrugs in the treatment of hepatitis C virus infection as well as future potential drugs currently in discovery or clinical evaluation. I highlight first generation landmark prodrug compounds which have been the foundations of incremental improvements toward the discovery and approval milestone of Sofosbuvir. Sofosbuvir is the first nucleotide prodrug marketed for hepatitis C virus treatment and the backbone of current combination therapies. Since this approval, new nucleotide prodrugs using the same design of Sofosbuvir McGuigan prodrug have emerged, some of them progressing through advanced clinical trials and may become available as new incremental alternative hepatitis C virus treatments in the future. Although since Sofosbuvir success, only minimal design efforts have been invested in finding better liver targeted prodrugs, a few novel prodrugs are being studied and their different modes of activation may prove beneficial over the heart/liver targeting ratio to reduce potential drug–drug interaction in combination therapies and yield safer treatment to patients. Prodrugs have long been avoided as much as possible in the past by development teams due to their metabolism and kinetic characterization complexity, but with their current success in hepatitis C virus treatment, and the knowledge gained in this endeavor, should become a first choice in future tissue targeting drug discovery programs beyond the particular case of nucleos(t)ide analogs.

There is a growing body of evidence suggesting that some ribonucleoside/ribonucleotide analogs may be incorporated into mitochondrial RNA by human mitochondrial DNA-dependent RNA polymerase (POLRMT) and disrupt mitochondrial RNA synthesis. An assessment of the incorporation efficiency of a ribonucleotide analog 5′-triphosphate by POLRMT may be used to evaluate the potential mitochondrial toxicity of the analog early in the development process. In this report, we provide a simple method to prepare active recombinant POLRMT. A robust in vitro nonradioactive primer extension assay was developed to assay the incorporation efficiency of ribonucleotide analog 5′-triphosphates. Our results show that many ribonucleotide analogs, including some antiviral compounds currently in various preclinical or clinical development stages, can be incorporated into newly synthesized RNA by POLRMT and that the incorporation of some of them can lead to chain termination. The discrimination ( D ) values of ribonucleotide analog 5′-triphosphates over those of natural ribonucleotide triphosphates (rNTPs) were measured to evaluate the incorporation efficiency of the ribonucleotide analog 5′-triphosphates by POLRMT. The discrimination values of natural rNTPs under the condition of misincorporation by POLRMT were used as a reference to evaluate the potential mitochondrial toxicity of ribonucleotide analogs. We propose the following criteria for the potential mitochondrial toxicity of ribonucleotide analogs based on D values: a safe compound has a D value of >10 5 ; a potentially toxic compound has a D value of >10 4 but 5 ; and a toxic compound has a D value of 4 . This report provides a simple screening method that should assist investigators in designing ribonucleoside-based drugs having lower mitochondrial toxicity.

Hepatitis B infection affects two billion people worldwide and 350 million of these are chronically infected. Chronic hepatitis B virus is one of the most important cause of mortality and morbidity worldwide. If it is left untreated, about one-third of affected people will develop progressive and possibly fatal liver disease, like hepatic cirrhosis and primary hepatocellular carcinoma. Currently, five nucleos(t)ide analogs are approved for the treatment of chronic HBV infection. They are: lamivudine, adefovir dipivoxil, telbivudine, entecavir and tenofovir disoproxil fumarate. In this work, we developed and validated an UPLC-Tandem mass spectrometry assay method capable of monitoring lamivudine, telbivudine, tenofovir and entecavir plasma concentrations. Both standards and quality controls (high, medium and low) were prepared in human plasma. Each sample was added with internal standard (5'amino-5'deoxy-thymidine) and then drugs were extracted through a protein precipitation protocol with acetonitrile+0.1% formic acid and then dried. The extracts were resuspended in water and then injected into the chromatographic system. The chromatographic separation was performed on an Acquity UPLC HSS T3 1.8 μm 2.1 × 150 mm column, with a gradient of water and acetonitrile, both added with formic acid (0.05%). Accuracy, intra-day and inter-day precision at quality controls levels fitted all FDA guidelines for all analytes, while matrix effects and recoveries resulted stable between samples for each analyte. Finally, we tested this method by monitoring plasma concentrations in 30 HBV+ patients with good results. This simple analytical method could represent a useful tool for the management of anti-HBV therapy.

The concept of click chemistry represented by the formation of the 1, 2, 3-triazole core has found wide application in drug discovery, particularly in the early discovery phases and the lead optimization process. 1, 2, 3-Triazoles ha ve attracted considerable attention in recent years because of their wide range of biological activities against various viruses, malignant cells, microorganisms and their inhibitory activities against several enzymes. This review emphasizes the recent advances on diverse and potent biological profiles of 1, 2, 3-triazolo- nucleosides, along with emerging application of click chemistry in their synthesis, and their perspective in the development of new bioactive chemical entities in the future. The work is primarily addressed to antiviral, antimicrobial and anticancer potency of this important structural motifs in which the 1, 2, 3-triazole ring acts as a nucleobase surrogate or is linked to a nucleobase or a sugar/sugar mimic moiety.

Background: Data on the efficacy of simplifying therapy using darunavir/ritonavir and lopinavir/ritonavir monotherapy in clinical practice remain limited.; Methods: A retrospective single-centre study including patients initiating darunavir/ritonavir or lopinavir/ritonavir monotherapy with a plasma HIV-1 viral load (pVL) 50 copies/mL or as any change in the regimen after a single determination with a pVL >50 copies/mL) during the follow-up. We also evaluated the percentage of patients remaining free of treatment failure (TF; defined as VF or the early discontinuation of monotherapy for any reason) and compared the effectiveness of the two regimens. Effectiveness was evaluated using cumulative survival analysis (at Weeks 48 and 96). Factors associated with VF and TF were analysed using Cox regression.; Results: A total of 522 patients were included (309 receiving lopinavir/ritonavir and 213 receiving darunavir/ritonavir). The median follow-up was 64.3 (30.5-143.0) weeks. The percentage of patients free of VF and TF was 94% (95% CI 91%-96%) and 79% (95% CI 75%-82%) at 48 weeks, respectively, and 86% (95% CI 81%-89%) and 62% (95% CI 57%-67%) at 96 weeks, respectively. The risk of VF was similar for the two regimens (HR = 1.0, 95% CI 0.6-1.8; P = 0.962). Lopinavir/ritonavir monotherapy was associated with a 1.5-fold greater risk of TF (95% CI 1.1-2.1; P = 0.012) and a 2.3-fold greater risk of discontinuation of therapy due to adverse events (95% CI 1.3-3.9; P = 0.003).; Conclusions: The virological efficacy of darunavir/ritonavir and lopinavir/ritonavir monotherapy is high in clinical practice. Treatment discontinuation due to safety issues is more frequent with lopinavir/ritonavir. This study was supported in part by grants from Lluita contra la SIDA Foundation (Barcelona, Spain), the Spanish AIDS Network ‘Red Temática Cooperativa de Investigación en SIDA’ (RIS, RD06/0006), NEAT (European AIDS Treatment Network), Ministerio de Economía y Competitividad of Spain (MTM2012-38067-C02-01) and GRBIO (Grup de Recerca en Bioestadística i Bioinformàtica; 2014 SGR 464). The funders had no role in study design, data collection and analysis, the decision to publish or drafting of the manuscript.

New nucleoside derivatives with nitrogen substitution at the C-6 position were prepared and screened initially for their in vitro anticancer bioactivity against human epithelial cancer cells (liver Huh7, colon HCT116, breast MCF7) by the NCI-sulforhodamine B assay. N6-(4-trifluoromethylphenyl)piperazine analog (27) exhibited promising cytotoxic activity. The compound 27 was more cytotoxic (IC50 = 1-4 μM) than 5-FU, fludarabine on Huh7, HCT116 and MCF7 cell lines. The most potent nucleosides (11, 13, 16, 18, 19, 21, 27, 28) were further screened for their cytotoxicity in hepatocellular cancer cell lines. The compound 27 demonstrated the highest cytotoxic activity against Huh7, Mahlavu and FOCUS cells (IC50 = 1, 3 and 1 μM respectively). Physicochemical properties, drug-likeness, and drug score profiles of the molecules showed that they are estimated to be orally bioavailable. The results pointed that the novel derivatives would be potential drug candidates. This work was supported by the Scientific and Technological Research Council of Turkey -TUBITAK ( TBAG-109T987 ), the KANSIL-2016H121540 ( Ministry of Development , Turkey). A

El alfa-herpesvirus equino 3 (EHV3) es el agente etiológico del exantema coital equino (ECE), enfermedad venérea, altamente contagiosa y caracterizada por la aparición de pápulas, vesículas, pústulas y úlceras en los genitales externos de yeguas y padrillos. Luego de la primo-infección, el EHV3 se mantiene en el animal en un estado de latencia a partir del cual puede reactivar y excretarse, generalmente de manera subclínica. No existen vacunas, por lo que la prevención se basa en la detección de las lesiones clínicas previo al servicio, y la segregación de estos animales. Sin embargo, este abordaje no previene la infección del padrillo por parte de yeguas que excretan el virus de manera subclínica, y por lo tanto existe la necesidad de un tratamiento específico contra el EHV3. En la actualidad, existen varios compuestos antivirales de probada eficacia contra herpesvirus humanos y veterinarios. El objetivo de este trabajo es comparar la eficacia de 3 compuestos antivirales, aciclovir, ganciclovir y cidofovir, contra EHV3 in vitro, y evaluar la eficacia de los mismos contra 6 cepas de campo argentinas de EHV3. Para determinar la eficacia de los compuestos in vitro se evaluaron 3 parámetros: reducción del número de placas de lisis, reducción del tamaño de placas de lisis y reducción de la producción de virus. Adicionalmente, la efectividad de los compuestos en una concentración óptima, previamente determinada en este estudio, fue determinada para 6 cepas de campo argentinas de EHV3. De acuerdo con los resultados obtenidos, ganciclovir fue el compuesto más potente en reducir la replicación del EHV3 in vitro, y por lo tanto podría considerarse un potencial candidato para el tratamiento y la prevención del ECE en yeguas y padrillos. Equid alphaherpesvirus 3 (EHV3) is the etiological agent of equine coital exanthema (ECE), which is a venereal, highly contagious disease, characterized by the formation of papules, vesicles, pustules and ulcers on the external genitalia of mares and stallions. EHV3 remains in a latent state after a successful infection and there are latently infected animals in which the virus is reactivated and generally re-excreted subclinically. There are no available vaccines for this condition and prevention is based on the clinical examination of mares prior to mating, which allows to segregate those showing clinical signs. As this approach does not eliminate the risk of contagion in stallions from subclinically infected mares, there is a need for a specific EHV3 treatment. Nowadays, there exist various antiviral compounds of proven effectiveness for other alphaherpesviruses affecting humans and animals. The aim of the present study was to compare the efficacy of three antiviral compounds, acyclovir, ganciclovir and cidofovir against EHV3 in vitro, and to assess their efficacy against six EHV3 Argentinian field isolates. To determine the efficacy of these compounds in vitro, three parameters were analyzed: reduction of plaque number, reduction of plaque size and reduction of viral production. Additionally, the effectiveness of the three compounds at an optimum concentration previously determined in this study was investigated for the EHV3 field isolates. Based on our results, ganciclovir was the most potent antiviral compound to reduce EHV3 replication in vitro and may thus be a valuable candidate for treatment and prevention of ECE in mares and stallions. Fil: Vissani, María Aldana. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; Argentina Fil: Zabal, Osvaldo Alfredo. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; Argentina. Universidad del Salvador; Argentina Fil: Tordoya, María S.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; Argentina Fil: Parreño, Gladys Viviana. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Thiry, Etienne. Université de Liège; Bélgica Fil: Barrandeguy, María. Universidad del Salvador; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires; Argentina

// Jingfeng Bi 1, * , Zheng Zhang 1, * , Enqiang Qin 2, * , Jun Hou 1, * , Shuiwen Liu 3 , Zengmin Liu 4 , Shuo Li 3 , Zhenman Wei 1 and Yanwei Zhong 5 1 Research Center for Clinical and Translational Medicine, 302 Hospital, Beijing, 100039, China 2 Infectious Disease Treatment Center, 302 Hospital, Beijing, 100039, China 3 Medical Department, 302 Hospital, Beijing, 100039, China 4 Medical Department, XingLong Hospital of TCM, Beijing, 100039, China 5 Institute of Infectious Disease, Pediatric Liver Disease Therapy and Research Center, 302 Hospital, Beijing, 100039, China * These authors contributed equally to this work Correspondence to: Zhenman Wei, email: weizhenman@sina.com Yanwei Zhong, email: zhongyanwei@126.com Keywords: nucleoside analogs, hepatitis B, cirrhosis, hepatocellular carcinoma Received: April 07, 2017 Accepted: May 06, 2017 Published: May 22, 2017 ABSTRACT Whether Nucleos(t)ide analogs(NA) treatment can delay the onset of HCC remains unclear. We retrospectively analyzed the clinical data of patients with HBV-related cirrhosis and HCC from 2000 to 2012. Cox proportional hazards model was used to explore the association between NA treatment and postponement of HCC development, the dependent variable was time interval from cirrhosis treatment towards the onset of HCC, and the covariates included age, sex, family history, compensation status at baseline. A total of 1155 HCC patients treated with NAs ( n = 528, lamivudine, adefovir, entecavir) and non NA ( n = 627) for more than 24 months before the occurrence of HCC were incorporated into the cohort. Compared with the non-NA group, NAs therapy was associated with delaying the onset of HCC in patients with cirrhosis. Significant factors were: adefovir treatment ( n = 181; p = 0.0072; HR: 0.792; 90% CI: 0.687–0.914), entecavir treatment ( n = 83; p = 0.0068; HR: 0.716; 90% CI: 0.585-0.877), lamivudine switched to adefovir treatment ( n = 95, p = 0.0808; HR: 0.822; 90% CI: 0.684 to 0.989). But Lamivudine monotherapy was not a significant factor ( n = 102; p = 0.6877; HR: 1.045; 90% CI: 0.873–1.250). Long-term NA treatment (> 6 months, except for lamivudine monotherapy) can delay the onset of HCC in patients with HBV-related cirrhosis, and applying high barrier NA to resistance is important in these patients.

The asymmetric synthesis of 1,3-oxathiolan-5-one derivatives through an enzyme-catalyzed, dynamic covalent kinetic resolution strategy is presented. Dynamic hemithioacetal formation combined with intramolecular, lipase-catalyzed lactonization resulted in good conversions with moderate to good enantiomeric excess (ee) for the final products. The process was evaluated for different lipase preparations, solvents, bases, and reaction temperatures, where lipase B from Candida antarctica (CAL-B) proved most efficient. The substrate scope was furthermore explored for a range of aldehyde structures, together with the potential access to nucleoside analog inhibitor core structures.

Background To assess the potential effects of telbivudine (LdT) and entecavir (ETV) on renal function in patients with chronic hepatitis B (CHB), we performed a meta-analysis of the relevant data available on these agents to evaluate their effects on the estimated glomerular filtration rate (eGFR) during treatment. Methods The PubMed, EMBASE, Scopus, CNKI (China National Knowledge Infrastructure), Cochrane Library, and WanFang databases were searched for relevant articles appearing in the literature up to July 1, 2015. A total of 6 studies (1960 CHB patients) with 1-year eGFR outcomes were retrieved and analyzed. Results Generally, the results of the 6 studies analyzed showed that eGFR was improved after LdT treatment, but was decreased after ETV treatment. Using a fixed-effects approach, the change in eGFR was found to be significantly different between LdT and ETV treatment (Z = 3.64; P = 0.0003). Whereas the eGFR was slightly decreased with ETV compared with baseline (−1.45 mL/min/1.73 m2), the eGFR was improved with LdT (2.99 mL/min/1.73 m2) after 1 year of treatment. An overall test of effect in the meta-analysis showed that the eGFR in LdT-treated patients was significantly improved after 1-year of treatment (Z = 3.71; P = 0.0002). Conclusion This meta-analysis has confirmed that LdT has a renal protective effect whereas ETV does not. However, whether the benefit on renal function outweighs the occurrence of resistance in specific clinical situations is not yet clear.

Lethal mutagenesis, a new antiviral strategy to extinguish virus through elevated mutation rates, was explored in H61-D cells an HIV-1 persistently infected lymphoid cell line. Three mutagenic agents: 5-hydroxy-2 '-deoxycytidine (5-OHdC), 5-fluorouracil (5-FU) and 2,2 '-difluoro-2 '-deoxycytidine (gemcitabine) were used. After 54 passages, treatments with 5-FU and gemcitabine reduced virus infectivity, p24 and RT activity. Treatment with the pyrimidine analog 5-OHdC resulted in increases of p24 production, RT activity and infectivity. Rise in viral replication by 5-OHdC during HIV-1 persistence is in contrast with its inhibitory effect in acute infections. Viral replication enhancement by 5-OHdC was associated with an increase in intracellular HIV-1 RNA mutations. Mechanisms of HIV-1 replication enhancement by 5-OHdC are unknown but some potential factors are discussed. Increase of HIV-1 replication by 5-OHdC cautions against the use, without previous analyses, of mutagenic nucleoside analogs for AIDS treatment. © 2011 Elsevier Inc., Fundacion para la Investigacion y Prevencion del SIDA en España (FIPSE); Red Temática Cooperativa de Investigación en SIDA (Red de grupos 173) of the Fondo de Investigaciones Sanitarias de la Seguridad Social; MICINN; Fundación Ramón Areces

Two nontypical nucleosides, 7-β- d -ribosyl-2,6-diamino-8-azapurine and 8-β- d -ribosyl-2,6-diamino-8-azapurine, have been found to exhibit moderately good, and selective, substrate properties toward calf and bacterial ( Escherichia coli ) forms of purine nucleoside phosphorylase (PNP). The former compound is effectively phosphorolysed by calf PNP and the latter by PNP from E. coli . Both compounds are fluorescent with λ max ∼ 425 to 430 nm, but the reaction product, 2,6-diamino-8-azapurine, emits in a different spectral region ( λ max ∼ 363 nm) with nearly 40% yield, providing a strong fluorogenic effect at 350 to 360 nm.

The evaluation of response to radiotherapy in patients with laryngeal cancer is a challenge because of the difficulty to differentiate between post-therapy changes and recurrent or residual tumor. Positron emission tomography is a non-invasive imaging tool that may be helpful in this differentiation. In this study, [F-18]-fluoro-3'-deoxy-L-thymidine ([F-18]FLT), a proliferation tracer is compared with 2-[F-18]-fluoro-2-deoxy-D-glucose ([F-18]FDG).Patients with primary laryngeal cancer, scheduled to undergo radiotherapy were included in this study. Patients underwent both [F-18]FLT-PET and [F-18]FDG-PET shortly before radiotherapy. Ten patients underwent [F-18]FLT-PET and [F-18]FDG-PET 2-3 months after radiotherapy. Scans were analyzed visually for areas of increased tracer uptake. The standardized uptake value (SUV) was measured as a semi-quantitative value of tracer uptake.Fourteen patients, all male, were included in this study. Both [F-18]FLT-PET and [F-18]FDG-PET showed increased tracer uptake in 12 out of 14 patients (86%). [F-18]FDG uptake was significantly higher than [F-18]FLT uptake (SUVmax: 4.5 vs. 2.4 (P = 0.002); SUVmean: 3.4 vs. 1.9 (P = 0.002)). After radiotherapy, 3 patients had histologically proven residual or recurrent laryngeal cancer. [F-18]FDG was true positive in 2 out of 3 patients, whereas [F-18]FLT showed increased tracer uptake in only one. Of the remaining 7 patients, [F-18]FLT was true negative in all, whereas [F-18]FDG showed increased uptake in one (false positive).[F-18]FLT-PET is feasible in visualizing laryngeal cancer and its evaluation of treatment. The overall uptake of this tracer is significantly lower as compared with [F-18]FDG, but tumor to background ratios are comparable. (C) 2009 Published by Elsevier Ltd.

Graphical abstract, Acyclic 2′-azanucleosides with a phosphonomethoxy function in the side chain were obtained by coupling of diethyl {2-[N-(pivaloyloxymethyl)-N-(p-toluenesulfonyl)amino]ethoxymethyl}phosphonate with the pyrimidine nucleobases via the Vorbrüggen-type protocol. The compounds were evaluated in vitro for activity against a broad variety of RNA and DNA viruses.

Graphical abstract, The acyclic azanucleosides with 2-, 3-, or 4-aminobenzenesulfonyl function at the nitrogen atom of the sugar mimic were prepared by coupling of 2-, 3-, or 4-nitro-N-(2-pivaloyloxyethyl)-N-(pivaloyloxymethyl)benzenesulfonamide with the silylated pyrimidine nucleobases followed by the reduction of the nitro group with sodium dithionite in aqueous solution or the palladium-catalysed transfer hydrogenation. The azanucleosides were evaluated for, but found to be devoid of, activity against several RNA- and DNA-viruses in vitro.

This work aimed at building a population pharmacokinetic (PK) model for lamivudine (LMV), stavudine (STV) and zidovudine (ZDV), estimating their inter and intraindividual PK variability and investigating the influence of different covariates. Population PK of LMV, STV and ZDV was separately evaluated from plasma concentrations obtained in 54, 39 and 27 HIV1-infected patients, respectively, enrolled in the COPHAR1-ANRS102 trial. The primary objective of this trial was to study the pharmacokinetics of indinavir (IDV) and nelfinavir (NFV) in treated patients with a sustained virological response. Concentrations of nucleoside analogs (NA) were measured in plasma as a secondary objective. A one-compartment model with first-order elimination was used, with zero-order absorption for LMV and first-order absorption for STV and ZDV. Mean parameters [interpatient variability in coefficient of variation (CV%)] of LMV, STV and ZDV were: oral volume of distribution (V/F) 145 l (52%), 24 l (81%) and 248 l (80%), oral clearance (Cl/F) 32 l/h, 16 l/h (74%) and 124 l/h (51%), respectively. For LMV, absorption duration (T a ) was 1.46 h (64%). For STV and ZDV, k a was 0.46 h−1 and 2.9 h−1, respectively. We found a systematic effect of combination with NFV vs. IDV. We found that intrapatient variability was greater than interpatient variability (except for STV) and greater than 55% for the three drugs. This trial enabled the estimation of the population PK parameters of three NA in patients with a sustained virological response, and the median curves could be used as references for concentration-controlled strategies. We observed, as for the protease inhibitors, a great variability of PK parameters.

Nucleoside analogs (NAs) are an important class of anti-retroviral compounds used against human immunodeficiency virus (HIV). We have analyzed the potential effect of polyamines on the incorporation of NAs during DNA synthesis by HIV type-1 (HIV-1) reverse transcriptase (RT). The polyamines exert the ability to decrease the incorporation of various dideoxynucleoside triphosphates (ddATP, ddTTP or ddCTP) with both RNA/DNA and DNA/DNA substrates in the following order: spermine > spermidine > putrescine. The reduction is a sequence-independent effect, taking place at different sequence context. The results suggest that polyamines might affect the inhibition of reverse transcription by nucleoside analogs HIV-1 RT directed .

The HCV polymerase is an attractive target for the development of new and specific anti-HCV drugs. Herein, the characterization of the inhibitory effect of 2′-C-Methyl-Cytidine shows that it is a potent inhibitor of both genotype 1b and 1a HCV replicon replication, both of laboratory-optimized as well as of NS5B clinical isolates–chimera replicons. The corresponding 5′-triphosphate derivative is a potent inhibitor of native HCV replicase isolated from replicon cells and of the recombinant genotype 1b and 1a HCV polymerase-mediated RNA synthesis. Resistance to 2′-C-Methyl-Cytidine was mapped to amino acid substitution S282T in the NS5B coding region. Cross-resistance was observed to 2′-C-Methyl-Adenosine but not to interferon α-2a, to non-nucleoside HCV polymerase inhibitors or to R1479, a new and potent nucleoside inhibitor of NS5B polymerase. In vitro studies mapped resistance to R1479 to amino acid substitutions S96T and S96T/N142T of the NS5B polymerase. These mutations did not confer resistance to 2-C-Methyl-Cytidine, thus confirming the lack of cross-resistance between these two HCV inhibitors. These data will allow the optimization of new polymerase inhibitors and their use in combination therapy.

A diastereo- and enantioselective synthesis of 4′-aza analogues of 2′,3′-dideoxynucleosides has been designed by the strategy of the 1,3-dipolar cycloaddition reaction of a Vasella-type nitrone. The reaction leads to (1′ R )- and (1′ S )-4′-aza analogues of 2′,3′-dideoxythimidine and fluorouridine, in enantiomerically pure forms.

The 1′,2′-unsaturated 2′,3′-secoadenosine and 2′,3′-secouridine analogues were synthesized by the regioselective elimination of the corresponding 2′,3′-ditosylates, 2 and 18, respectively, under basic conditions. The observed regioselectivity may be explained by the higher acidity and, hence, preferential elimination of the anomeric H–C(1′) in comparison to HC(4′). The retained (tol-4-yl)sulfonyloxy group at C(3′) of 3 allowed the preparation of the 3′-azido, 3′-chloro, and 3′-hydroxy derivatives 5–7 by nucleophilic substitution. ZnBr2 in dry CH2Cl2 was found to be successful in the removal (85%) of the trityl group without any cleavage of the acid-sensitive, ketene-derived N,O-ketal function. In the uridine series, base-promoted regioselective elimination (19), nucleophilic displacement of the tosyl group by azide (20), and debenzylation of the protected N(3)-imide function gave 1′,2′-unsaturated 5′-O-trityl-3′-azido-secouridine derivative 21. The same compound was also obtained by the elimination performed on 2,2′-anhydro-3′-azido-3′-azido-3′-deoxy-5′-O-2′,3′-secouridine (22) that reacted with KO(t-Bu) under opening of the oxazole ring and double-bond formation at C(1′).

In the UK, the annual cost of treatment and care for people with human immunodeficiency virus (HIV)/acquired immune deficiency virus (AIDS) rose by over 600% from £104 million in 1997 to £762 million in 2010; approximately two-thirds of the £762 million cost of treatment and care in 2010 was for the procurement of antiretrovirals and other related drugs. The number of people accessing care for HIV/AIDS rose from 22,000 in 2000 to 65,000 in 2009. Adoption of “test and treat” guidelines for treating all HIV-infected people with antiretrovirals would further increase the burden of costs. Given the current economic situation, there is now a new focus on strategies for treatment and care of people with HIV-1 infection which can maintain efficacy but at a lower cost. In this review, we propose three strategies which could potentially lower the costs of treatment and care, ie, stopping testing CD4 counts for patients with full HIV RNA suppression on antiretroviral treatment and recent CD4 counts above 350 cells/μL; more widespread use of generic antiretrovirals as replacements for patients currently taking patented versions; and use of darunavir-ritonavir monotherapy as a switch option for patients with full HIV RNA suppression on other antiretrovirals and no history of virological failure. However, it is important that high standards of clinical care are maintained despite cost-saving measures. Antiretrovirals with generic alternatives may have toxicity issues, eg, zidovudine and nevirapine. There could be ethical issues in starting patients on these drugs if they are currently tolerating other treatments. The use of darunavir-ritonavir monotherapy is not consistently recommended in international HIV treatment guidelines.

Increased cellular proliferation is an integral part of the cancer phenotype. Hence, the sustained and continued demand on supply of DNA building blocks during the DNA replication presents a potential target for therapeutic intervention. For this propose, the alpha and Auger electron emitting nucleotides analogs are attractive for targeted endoradiotherapy, given that DNA of malignant cells is selectively addressed. This review summarizes development and preclinical and clinical studies of endoradiotherapeutic acting nucleoside analogs with a special focus on thymidine analogs.

Objectives The aim of this study was to investigate the economic consequences of nucleoside analog therapy for hepatitis B treatment in China. Methods A cost-utility analysis of treatments for HBeAg-positive and HBeAg-negative chronic hepatitis B (CHB) was conducted using a Markov model, in which patients' yearly transitions between different health states were tracked. Patients were tracked as they moved between the following health states: CHB, HBeAg seroconversion (HBeAg-positive CHB patients can have this special health state), virologic resistance, virologic response, compensated cirrhosis, decompensated cirrhosis, hepatocellular carcinoma, liver transplantation, and death. The transition parameters were derived either from systematic reviews of the literature or from previous economic studies. Cost and utility data came from studies based on a Chinese CHB cohort. One-way sensitivity analyses as well as second-order Monte Carlo and probabilistic sensitivity analyses were performed. Results The entecavir strategy yielded the most quality-adjusted life years (QALYs) for both HBeAg-positive and HBeAg-negative patients when compared with the "no treatment," the lamivudine, the adefovir, and the telbivudine strategies. The risks of complications and mortality also decreased. In the economic analysis, the "no treatment" strategy was the least effective, whereas the entecavir strategy was both the least expensive and the most cost-effective option, followed by telbivudine and lamivudine. The probabilistic sensitivity analysis showed that the entecavir strategy would result in improved cost-effectiveness in >90% of cases at a threshold of $20,000 per QALY. In a one-way sensitivity analysis, the most influential parameters impacting the model's robustness were the utilities of the CHB and virologic response health states. Conclusions In China, when treating both HBeAg-positive and HBeAg-negative CHB populations, entecavir is the most cost-effective option when compared with lamivudine, adefovir, and telbivudine.

The variability of tumor responses to chemotherapeutic agents is a topic of major interest in current cancer research. Advances in the knowledge of dysregulation of key molecular pathways in cancer cells have enabled techniques to be developed that can profile tumor cells for their genetic background, allowing selection of anticancer agents on an individual basis. The next generation of anticancer treatments might therefore be tailored according to the molecular alterations identified in tumor cells of individual patients. However, before these alterations can be exploited from a therapeutic point of view, it is necessary to understand how such alterations influence the cellular pathways that control sensitivity to chemotherapeutic agents. Pharmacogenetics and pharmacoproteomics, novel disciplines that investigate the relationship between gene and protein expression in tumor cells and the response to anticancer agents, will be instrumental in developing optimal chemotherapeutic regimens for patients with non-Hodgkin's lymphoma.

A first solid phase approach to obtain monosubstituted CD conjugates to different labels has been developed. A new solid support has been designed to get a variety of C-6 monofunctionalized CDs (α, β, MeβCD and HPβCD) covalently linked through a phosphodiester bridge to different labels, in highly pure form and under very mild detachment conditions. © The Royal Society of Chemistry 2012.

The self-assembly of 2,4,6-tris(pyridin-4-yl)-1,3,5-triazine (tpt) triangular panels with p-cymene (pPr(i)C(6)H(4)Me) ruthenium building blocks and 2,5-dioxydo-1,4-benzoquinonato (dobq) or 5,8-dioxydo-1,4-naphthoquinonato (donq) bridges, in the presence of a pyrenyl-nucleoside derivatives (pyreneR),. affords the triangular prismatic host guest compounds [(pyrene-R)CRu6(pPr(i)C(6)H(4)Me)(6)(tpt)(2)(dobq)(3)](6+) ([(pyrene-R)C1](6+)) and [(pyrene-R)CRu6(pPr(i)C(6)H(4)Me)(6)(tpt)(2)(donq)(3)](6+) ([(pyrene-R)C2](6+)), respectively. The inclusion of six monosubstituted pyrenyl-nucleosides (pyrene-R1 = 5'-(1-pyrenyl butanoate)-2'-deoxyuridine, pyrene-R2 = 5-fluoro-5'-(1-pyrenyl butanoate)-2'-deoxyuridine, pyrene-R3 = 5'-{N-[1-oxo-4-(1-pyrenyl)butyl]glycyl}-2'-deoxyuridine, pyrene-R4 = 5-fluoro-5'-{N[1-oxo-4-(1-pyrenyl)butyl]-glycyl}2'-deoxyuridine, pyrene-R5 = 5-fluoro-5'-{N-[1-oxo-4-(1-pyrenyl)butyl]-phenylalanyl}-2'-deoxyvuridine, pyrene-R6 = 5-fluoro-5'-{N-[1-oxo-4-(1-pyrenyl)butyl]-phenylalanyl}-2'-deoxyuridine) has been accomplished. The carceplex nature of [(pyrene-R)C1](6+) with the pyrenyl moiety firmly encapsulated in the hydrophobic cavity of the cage with the nucleoside groups pointing outward was confirmed by NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS), while the host-guest nature of [(pyrene-R)C2](6+) was studied in solution by NMR techniques. In contrast to the floxuridine compounds used in the clinic, the host-guest complexes are highly water-soluble. Consequently, the cytotoxicities of these water-soluble compounds have been established using human ovarian A2780 and A2780cisR cancer cells. All the host guest systems are more cytotoxic than the empty cages alone [1][CF3SO3](6) (IC50 = 23 mu M) and [2][CF3SO3](6) (IC50 = 10 mu M), the most active compound [pyrene-R4C1][CF3SO3](6) being 2 orders of magnitude more cytotoxic (IC50 = 0.3 mu M) on these human ovarian cancer cell lines (A2780 and A2780cisR).

Ribonucleotide reductase (RNR) is an essential enzyme in DNA biogenesis and a target of several chemotherapeutics. Here, we investigate how antileukemic drugs (e.g., clofarabine [CIF]) that target one of the two subunits of RNR, RNR-alpha, affect noncanonical RNR-alpha functions. We discovered that these clinically approved RNR-inhibiting dATP-analogs inhibit growth by also targeting ZRANB3-a recently identified DNA synthesis promoter and nuclear-localized interactor of RNR-alpha. Remarkably, in early time points following drug treatment, ZRANB3 targeting accounted for most of the drug-induced DNA synthesis suppression and multiple cell types featuring ZRANB3 knockout/knockdown were resistant to these drugs. In addition, ZRANB3 plays a major role in regulating tumor invasion and H-ras(G12V)-promoted transformation in a manner dependent on the recently discovered interactome of RNR-alpha involving select cytosolic-/nuclear-localized protein players. The H-ras(G12V)-promoted transformation-which we show requires ZRANB3-supported DNA synthesis-was efficiently suppressed by ClF. Such overlookedmechanisms of action of approved drugs and a previously unappreciated example of non-oncogene addiction, which is suppressed by RNR-alpha, may advance cancer interventions.