bluuebunny/crossref_metadata_2025 huggingface dataset:
Mutations and Polymorphisms Associated with Antiretroviral Drugs in HIV-1C-Infected African Patients
Authors: Doualla-Bell Florence , Gaseitsiwe Simane , Ndung'u Thumbi , Modukanele Musetsanagepe , Peter Trevor , Novitsky Vladimir , Ndwapi Ndwapi , Tendani Gaolathe , Avalos Ava , Wester William , Bussmann Hermann , Cardiello Peter , Marlink Richard , Moffat Howard , Thior Ibou , Wainberg Mark A , Essex Max
Published: March 2015

To detect and characterize polymerase gene ( pol) polymorphisms and mutation patterns in HIV-1C-infected Batswana patients treated with reverse transcriptase inhibitors, samples from AIDS patients treated with highly active antiretroviral therapy (HAART) were sequenced for the region encompassing the entire HIV-1 protease (PR) and the first 335 amino acids of reverse transcriptase (RT). Amongst the 16 patients treated with antiretroviral (ARV) drugs, eight started HAART regimens containing didanosine, stavudine and nevirapine (ddI/d4T/NVP) or efavirenz (EFV) (arm A) while the others started with zidovudine (AZT) and lamivudine (3TC) given together as combivir (CBV) with either NVP or EFV as arm B. Arm B is the first line regimen currently provided by the Botswana ARV national programme. Greater efficacy, in terms of treatment duration, was observed in patients in arm B (14 months) as compared with patients in arm A (9 months); P<0.05, n=8. Appearance of the M184V mutation in the arm B patients coincided with a rebound of viral load (VL) (4.3 +0.1 log10 RNA copies/ml) and a significantly improved immunological parameter (ΔCD4=207.0 +48.1 cells/μl; P<0.05). Interestingly, patients developing the M184V mutation preferentially harboured polymorphisms Q174K and/or I178L located in close proximity to pol position 184. The M184V mutation occurred following a clear clinical benefit consisting of increased CD4 cell counts and lower plasma viral loads. Primary mutations known to be associated with NNRTI and NRTI resistance for HIV-1B were observed in 10 of the 16 treated patients.
Isothiazole Derivatives as Novel HIV Replication Inhibitors
Authors: Cutrì Christian CC , Garozzo Adriana , Pannecouque Christophe , Castro Angelo , Guerrera Francesco , De Clercq Erik
Published: March 2015

A series of 3,4,5-trisubstituted isothiazoles has been screened against HIV-1 (IIIB) and HIV-2 (ROD) at sub-toxic concentrations in acutely infected MT-4 cells. Among the tested compounds, only 3-mercapto-5-phenyl-4-isothiazolecarbonitrile was found to inhibit the replication of HIV-1 (IIIB) and HIV-2 (ROD) at 50% effective concentrations (EC50) of 7.8 and 9.7 μg/ml, respectively. The presence of a thioalkyl chain or dialkylamino function in the 3-position caused a loss of anti-HIV activity. New 4-cyano-5-phenylisothiazoles with other substituents in the 3-position have also been synthesized and studied as potential anti-HIV agents. Our results have demonstrated that 5-phenyl-3-(4-cyano-5-phenylisothiazol-3-yl) disulphanyl-4-isothiazolecarbonitrile and S-(4-cyano-5-phenylisothiazol-3-yl)- O-ethyl thiocarbonate are effective against both HIV-1 (IIIB) (EC50=13.6 and 15.2 μg/ml, respectively) and HIV-2 (ROD) (EC50=17.4 and 13.4 μg/ml, respectively).
Recent Advances in the Synthesis of the Carbocyclic Nucleosides as Potential Antiviral Agents
Authors: Jeong Lak Shin , Lee Jeong A
Published: March 2015

Compared with 4′-oxonucleosides, there have been far fewer systematic structure-activity relationship studies on carbocyclic nucleosides as antiviral and antitumour agents. This is mainly because of the synthetic problems in preparing the carbasugars. However, the recent discovery of the ring-closing metathesis (RCM) (a powerful tool for the preparation of 5-membered carbasugar via C-C bond formation) has made it possible to synthesize the key carbasugars to a preparative scale. This review summarizes the asymmetric syntheses of carbasugars and carbocyclic nucleosides, using an RCM reaction as a key step. Furthermore, the review includes valuable information for designing and synthesizing novel carbocyclic nucleosides.
Synthesis, Physicochemical and Pharmacokinetic Studies of Potential Prodrugs of β-L-2′-Deoxycytidine, a Selective and Specific Anti-HBV Agent
Authors: Pierra Claire , Benzaria Samira , Dukhan David , Loi Anna Giulia , La Colla Paolo , Bridges Edward , Mao John , Standring David , Sommadossi Jean-Pierre , Gosselin Gilles
Published: March 2015

β-L-2′-Deoxycytidine (β-L-dC) is a potent, selective and specific anti-hepatitis B virus (HBV) agent. To improve its oral bioavailability, several derivatives involving sugar or base acylation, as well as N4-derivatization with an N,N-(dimethyl-amino)methylene function, were synthesized. The physicochemical characteristics (including chemical stabilities, solubilities and distribution coefficient values) and pharmacokinetics of these compounds were determined and compared with those of the parent drug, β-L-dC. Presented in part at the 14th International Conference on Antiviral Research, Seattle, Washington, USA, 8–13 April 2001. Antiviral Reseach 2001; 50:A79.
Therapeutic Basis of Vidarabine on Adenovirus-Induced Haemorrhagic Cystitis
Authors: Kurosaki Kunikazu , Miwa Naoko , Yoshida Yoshihiro , Kurokawa Masahiko , Kurimoto Masanori , Endo Shunro , Shiraki Kimiyasu
Published: March 2015

When adenovirus causes haemorrhagic cystitis in immunocompromised patients, vidarabine is used for its treatment because therapeutic choice is limited. Although vidarabine has been reported to be effective for these patients, its therapeutic basis has not yet been established. Vidarabine dose-dependently inhibited viral replication as assessed by a yield reduction assay. Viral protein synthesis was dose-dependently inhibited by vidarabine but not at all by acyclovir, and the degree of inhibition by vidarabine was different for each of the viral proteins, ranging from 0–40% of the untreated control. These results indicated the specificity and mechanism of action of vidarabine against adenovirus. The concentration of vidarabine and its metabolite in the bladder is suggested to exhibit effective anti-adenoviral activity in suppressing the replication of adenovirus. Thus, our results support vidarabine therapy as a possible candidate for adenovirus-induced haemorrhagic cystitis in immunocompromised patients.
Pegylating IFNs at His-34 Improves the in Vitro Antiviral Activity Through the JAK/STAT Pathway
Authors: Grace Michael J , Cutler David
Published: March 2015

Pegylated interferon alpha-2, alone or in combination with ribavirin, has become the standard therapy for patients with chronic hepatitis C infection. Pegylation of interferon alpha-2 results in a substantially extended half-life that permits once-weekly dosing, because of reduced clearance and more sustained absorption. The size of PEG moiety appears to influence the relative antiviral activities of peginterferon alpha-2. Increasing the size of the polyethylene glycol (PEG) moiety results in a reduction of the specific antiviral activity of the pegylated protein. For example, peginterferon alpha-2b (12 kDa) has an in vitro antiviral specific activity 25–35-fold higher than peginterferon alpha-2a (40 kDa). The antiviral activity of pegylated interferon alpha-2 is also governed by the site of pegylation of the interferon alpha core proteins. Interferon alpha-2a is monopegylated at four major positional lysine (Lys) residues. The major site of interferon alpha-2b monopegylation is histidine (His34), with additional pegylation sites at lysine and cysteine residues. The 12 kDa pegylated His34 positional isomer of peginterferon alpha-2b has the highest antiviral and antiproliferative in vitro specific activity compared with both the 12 kDa Lys positional isomers and the 40 kDa Lys positional isomers. The correlative effects of size and site of pegylation on the JAK/STAT signalling pathway, as evidenced by differences in the formation of the Stat1 homodimer complex, are suggestive of a receptor-mediated mechanism that governs the antiviral activity of pegylated interferons. The elucidation of the in vitro effects of pegylation is important and this will ultimately have a positive impact on the in vivo efficacy of treatment for patients with hepatitis C.
Analogues of Acyclic Nucleosides Derived from Tris-(Hydroxymethyl)Phosphine Oxide or Bis-(Hydroxymethyl)Phosphinic Acid Coupled to DNA Nucleobases
Authors: Nawrot Barbara , Michalak Olga , De Clercq Erik , Stec Wojciech J
Published: March 2015

A series of novel acyclic nucleoside analogues containing bis-(hydroxymethyl)phosphinic acid (BHPA) or tris(hydroxymethyl)phosphine oxide (THPO) coupled with DNA nucleobases or with 5-fluorouracil were prepared and their antiviral activity was studied against cytomegalovirus (CMV), varicella-zoster virus (VZV), parainfluenza-virus type 3, reovirus-type 1, sindbis, coxsackie B4, punta toro, vesicular stomatitis and respiratory syncytial virus, herpes simplex virus-type 1 (KOS) and type 2 (G), vaccinia virus and herpes simplex virus-1 (TK-KOS ACVr). No specific antiviral effects were noted for any of test compounds against viruses evaluated, except thymine, cytosine and adenine derivatives of BHPA exerting borderline activity against respiratory syncytial virus at the 80 mg/ml concentration.
Non-Nucleoside Structures Retain Full Anti-HCMV Potency of the Dideoxy Furanopyrimidine Family
Authors: Bidet Olivier , McGuigan Christopher , Snoeck Robert , Andrei Graciela , De Clercq Erik , Balzarini Jan
Published: March 2015

We have recently reported that 2′,3'dideoxy analogues of our exquisitely potent anti-VZV furanopyrimidine deoxynucleosides are shifted to selective anti-HCMV agents. We now find that the fully deoxygenated 2′,3′,5′-trideoxy analogue is fully antivirally active. This is taken as proof that these agents act by a novel non-nucleoside mechanism of action.
Replicon Cell Culture System as a Valuable Tool in Antiviral Drug Discovery against Hepatitis C Virus
Authors: Horscroft Nigel , Lai Vicky CH , Cheney Wayne , Yao Nanhua , Wu Jim Z , Hong Zhi , Zhong Weidong
Published: March 2015

Discovery of potential therapeutics against hepatitis C virus (HCV) infection has been hampered in the past decade by the inability to grow this virus in tissue culture and by the lack of robust small animal models. This situation has been improved by the recent development of a selectable HCV replicon cell culture system. For the first time, drug discovery scientists are able to screen large compound collections using the replicon cell culture system to identify small molecules with the potential to inhibit HCV RNA replication. The replicon system has also been used to elucidate inhibitors' antiviral mechanism of action and to optimize antiviral potency. In this review, we will summarize the recent development of HCV replicon cell culture system and its use in anti-HCV drug discovery. The antiviral activities of promising lead compounds are also reviewed.
New Antiviral Drugs, Vaccines and Classic Public Health Interventions against SARS Coronavirus
Authors: Oxford John S , Balasingam Shobana , Chan Charlotte , Catchpole Andrew , Lambkin Robert
Published: March 2015

Severe acute respiratory syndrome (SARS) is caused by one of two recently discovered coronaviruses. The virus is emergent from South East (SE) Asian mammals: either the civet cat, a related species or a rat species. The virus has a long incubation period and low reproduction number (R0 value) and hence the first outbreak in 2004 was controlled by hygiene and quarantine. However, the healthcare system was compromised and the economic cost was extremely high. Fortunately, the virus is easily cultivated in Vero E6 cells and therefore the search for new antivirals and vaccines was initiated within weeks of the discovery of the virus using classic techniques of cell culture and electron microscopy. Molecular diagnostics facilitated rapid and accurate diagnosis, a key factor in containing the outbreak. The broad-spectrum molecule ribavirin was used in SE Asia in infected patients alongside corticosteroids. In retrospect, many patients survived due to careful nursing. The only currently accepted intervention is interferon. Coronavirus replicon systems should facilitate rapid screening of new inhibitors and the complex mechanism of viral replication will ensure that drugs are developed against at least five molecular targets, in particular the viral protease.
Current Status of Anti-SARS Agents
Authors: Shigeta Shiro , Yamase Toshihiro
Published: March 2015

Severe acute respiratory syndrome (SARS) is a disease that has newly emerged in the 21st century, and is both severe and highly contagious. SARS first surfaced in late 2002 and spread within a few months from its origin in Guandong province, China, to more than 30 countries (World Health Organization, 2003). In this review, several antiviral substances shown to be active in vitro will be introduced and summarized in the order of the virus' replication steps; that is, binding to cellular receptor, fusion and entry to the cells, viral RNA replication and transcription, protein processing and so on. The possible clinical use of several synthetic peptides, including those that mimic the S-binding domain, the HR2 fusion protein and SARS proteinase substrates, will be discussed. Monoclonal antibodies (Mabs) and established drugs, such as interferons and HIV proteinase inhibitors, are also discussed in relation to anti-SARS clinical use.
Comparative Pharmacokinetics of Racivir®, (±)-β-2′,3′-Dideoxy-5-Fluoro-3′-Thiacytidine in Rats, Rabbits, Dogs, Monkeys and HIV-Infected Humans
Authors: Hurwitz Selwyn J , Otto Michael J , Schinazi Raymond F
Published: March 2015

Racivir® is a 50:50 racemic mixture of the (–)- and (+)-β-enantiomers of 2′-deoxy-3′-thia-5-fluorocytosine (FTC), which is being developed for the treatment of HIV and hepatitis B virus (HBV). The (+)-enantiomer of FTC is approximately 10–20-fold less potent than (–)-FTC, but it selects for a different HIV mutation in human lymphocytes. Plasma concentrations from a group of 54 rats, 12 pregnant rabbits and 60 dogs enrolled in large toxicity studies using a wide variety of oral doses, were compared using non-compartment pharmacokinetic modelling versus dose, treatment duration, species and gender. The pharmacokinetics of Racivir® were also compared with those of a previously published pharmacokinetic study in rhesus monkeys and with data from HIV-infected human male volunteers. The (+)-FTC, but not the (–)-enantiomer, can be deaminated to the non-toxic inactive metabolite (+)-FTU. Therefore, the plasma exposure to (+)-FTU was also determined. The order of relative plasma exposure to (+)-FTU was rhesus monkeys > humans > pregnant rabbits > dogs > rats. Allometric scaling was performed to relate systemic clearance/fraction of drug absorbed (Cl/F) and terminal phase volume of distribution (Vβ/F) versus species body weights. No individual animal species mimicked the Cl/F values in humans. However, allometric scaling using a combination of rats, pregnant rabbits and monkeys predicted the mean human Cl/F value better than a combination of rats and rabbits only (within 0.24 and SD of mean vs 0.81 SD of the observed mean value). Similarly, human Vβ/F values were best predicted using a combination of rat and monkey data (within 0.64 SD of mean value). Species demonstrating greater deamination to (+)-FTU tended to have greater than predicted Cl/F values. The Cmax values of dogs were the closest to humans, but were statistically different. This study highlights the importance of selecting animal species that demonstrate similar cytidine deaminase activity to humans when performing preclinical dosing studies on Racivir® other antiviral agents that are substrates for mammalian cytidine deaminases.
A Throat Lozenge Containing Amyl Meta Cresol and Dichlorobenzyl Alcohol Has a Direct Virucidal Effect on Respiratory Syncytial Virus, Influenza a and SARS-CoV
Authors: Oxford John S , Lambkin Robert , Gibb Iain , Balasingam Shobana , Chan Charlotte , Catchpole Andrew
Published: March 2015

A potent virucidal mixture containing amyl metacresol and dichlorobenzyl alcohol at low pH inactivated enveloped respiratory viruses influenza A, respiratory synctial virus (RSV) and severe acute respiratory syndrome coronavirus (SARS-CoV) but not viruses with icosahedral symmetry, such as adenoviruses or rhinoviruses. A titre of approximately 3.5 log10 TCID50 was reduced to below the level of detection within two minutes. Electron microscopy of purified influenza A virus showed extensive clumping and morphological changes in spike configuration after contact with the virucidal mixture, but no overt destruction of the viral membrane. We conclude that, formulated as a lozenge, the mixture could have significant effects in reducing the infectivity of certain infectious viruses in the throat and presumably in cough droplets, thus reducing, theoretically, opportunities for person-to-person transmission.
TSAO Derivatives the First Non-Peptide Inhibitors of HIV-1 RT Dimerization
Authors: Camarasa María-José , Velázquez Sonsoles , San-Félix Ana , Pérez-Pérez María-Jesús
Published: March 2015

The combination of different anti-HIV agents has become the standard of care for AIDS or HIV-infected individuals. Important progress has been made in the development of drugs for the clinical treatment of HIV infection. To date, 20 drugs have been approved for the treatment of AIDS. However, viral rebound during therapy, the emergence of HIV drug resistance and the need for long-term treatment modalities are the main causes for the failure of current antiretroviral therapy. There is still a need for the development of new drugs that are either less toxic, active against the growing number of drug-resistant HIV strains or directed to novel targets in the viral life cycle. Eleven of the approved anti-HIV drugs target the reverse transcriptase (RT). Among the so-called non-nucleoside RT inhibitors (NNRTIs) TSAO derivatives are an unusual class of compounds that exert their unique selectivity for HIV-1 through a specific interaction with the p51 subunit of HIV-1 RT. They are the only NNRTIs for which amino acids at both subunits (p66 and p51) of HIV-1 RT are needed for optimal interaction with the enzyme. Moreover, the TSAO compounds are the first non-peptide molecules that interfere with the dimerization of the enzyme.
Achievements and Challenges in Antiviral Drug Discovery
Authors: Littler Eddy , Oberg Bo
Published: March 2015

The last 40 years have seen the development of several antiviral drugs with therapeutic value in treating life-threatening or debilitating diseases such as those caused by HIV, hepatitis B virus, herpesviruses (such as herpes simplex virus and varicella zoster virus) and influenza virus. These relatively recent advances have been due to technical breakthroughs in the cultivation of viruses in the laboratory, identification of viral enzymes and, more recently, their molecular biology. We describe here the antecedence of several of the existing antivirals and their strengths and weaknesses. We indicate where the major challenges lie for future improvements of current therapies and possible new indications, such as hepatitis C virus and papillomavirus. We also describe how current antiviral therapies are restricted to a rather limited number of viral diseases of sufficient interest to the pharmaceutical industry. Finally we describe the potential threat of emerging viruses and bio-weapons and the challenges that they present to therapy.
Retrovirus Reverse Transcriptases Containing a Modified YXDD Motif
Authors: Sharma Prem L , Nurpeisov Viktoria , Schinazi Raymond F
Published: March 2015

The YXDD motif, where X is a variable amino acid, is highly conserved among various viral RNA-dependent DNA polymerases. Mutations in the YXDD motif can abolish enzymatic activity, alter the processivity and fidelity of enzymes and decrease virus infectivity. This review provides a summary of the significant documented studies on the YXDD motif of HIV-1, simian immunodeficiency virus, feline immunodeficiency virus and murine leukaemia virus and the impact of mutation that this motif has had on viral pathogenesis and drug treatment.
Characterization of Hepatitis B Virus Inhibition by Novel 2′-Fluoro-2′,3′-Unsaturated Beta-D- and l-nucleosides
Authors: Pai S Balakrishna , Pai Rekha B , Xie Meng-Yu , Beker Tolunay , Shi Junxing , Tharnish Philip M , Chu Chung K , Schinazi Raymond F
Published: March 2015

The clinical emergence of lamivudine and adefovir resistance mutations on prolonged therapy further necessitates the development of additional drugs for the treatment of hepatitis B virus (HBV) infections. We have evaluated a number of novel 2′-fluoro-2′,3′-unsaturated d- and l-nucleosides for their anti-HBV activity in the HepG2–2.2.15 cell system. The most potent nucleosides were β-l-2′-fluoro-2′,3′-dideoxy-2′,3′-didehydrocytidine (l-2′-Fd4C) and β-l-2′-fluoro-2′,3′-dideoxy-2′,3′-didehydro-5-fluorocytidine (l-2′-Fd4FC) with median effective concentrations (EC50) of 0.002 μM and 0.004 μM, respectively. The d-enantiomers of the 2′-fluoro-substituted cytidine analogues in this series showed activity, with the 5-fluorocytidine (d-2′-Fd4FC) being the most potent (EC50=0.05 μM). The active compounds were not cytotoxic to a number of cell lines or to bone marrow progenitor cells. Furthermore, mitochondrial DNA synthesis and function were not affected by these nucleosides. l-2′-Fd4C did not affect viral transcription, implying that it does not inhibit cellular RNA polymerase II. Studies with the HBV polymerase in core particles revealed that the 5′-triphosphates of l-2′-Fd4C and d-2′-Fd4FC produced a dose-dependent inhibition of the incorporation of 32P-dCTP into the HBV DNA, indicating that the mechanism of action of these compounds is through specific inhibition of viral DNA synthesis. This class of nucleosides, which exhibit potent antiviral activity and a favourable safety profile, have potential for the treatment of HBV infections and warrant further development.
Characterization and Treatment of Cidofovir-Resistant Vaccinia (WR Strain) Virus Infections in Cell Culture and in Mice
Authors: Smee Donald F , Wandersee Miles K , Bailey Kevin W , Hostetler Karl Y , Holy Antonin , Sidwell Robert W
Published: March 2015

The wild-type (WT) vaccinia (WR strain) virus is highly virulent to mice by intranasal inoculation, yet death can be prevented by cidofovir treatment. A cidofovir-resistant (CDV-R) mutant of the virus was developed by 15 Vero cell culture passages in order to determine cross-resistance to other inhibitors, growth characteristics, virulence in infected mice, and suitability of the animal model for studying antiviral therapies. Comparisons were made to the original WT virus and to a WT virus passaged 15 times in culture (WTp15 virus). Cidofovir inhibited WT, WTp15, and CDV-R viruses by 50% at 61, 56 and 790 μM, respectively, in plaque reduction assays, with similar inhibition seen in virus yield studies. Cross-resistance occurred with compounds related to cidofovir, but not with unrelated nucleosides. The resistant virus produced 300-fold fewer infectious particles (PFU) than WT and WTp15 viruses in mouse C127I cells, yet replicated similarly in Vero (monkey) cells. The CDV-R virus was completely attenuated for virulence at 107 PFU per mouse in normal BALB/c mice and in severe combined immunodeficient (SCID) mice. The WTp15 virus was 100-fold less virulent than WT virus in BALB/c mice. Thus, the lack of virulence of the resistant virus in the animal model is explained partly by its reduced ability to replicate in mouse cells and by attenuation occurring as a result of extensive cell culturing (inferred from what occurred with the WTp15 virus). Lung and snout virus titre reduction parameters were used to assess antiviral activity of compounds in BALB/c mice infected intranasally with the CDV-R virus. Cidofovir, HDP-cidofovir and arabinofuranosyladenine treatments reduced lung virus titres <fourfold, and snout virus titres ⩾eight-fold. The animal model appears to have limited utility in drug efficacy testing.
Pointer the Role of Breast Cancer Resistance Protein (BCRP/ABCG2) in Cellular Resistance to HIV-1 Nucleoside Reverse Transcriptase Inhibitors
Authors: Wang Xin , Baba Masanori
Published: March 2015

Treatment of HIV-1-infected patients with antiretroviral agents is not always successful due to the emergence of resistant HIV-1 mutants with reduced susceptibility to the agents. However, factors other than viral mutation may also contribute to treatment failure. It has been demonstrated that the ATP-binding cassette (ABC) transporter P-glycoprotein (P-gp/ABCB1) is a key determinant of oral bioavailability of HIV-1 protease inhibitors and their penetration of the central nervous system. More recently, we have found that the expression of breast cancer resistance protein (BCRP/ABCG2) in a CD4+ T-cell line confers cellular resistance to nucleoside reverse transcriptase inhibitors (NRTIs). The anti-HIV-1 activity of the NRTI zidovudine (AZT) was significantly diminished through the reduction of its metabolite levels in MT-4 cells which express high levels of BCRP. Moreover, the BCRP-specific inhibitor fumitremorgin C could completely restore the cytotoxicity of AZT and intracellular levels of its metabolites in BCRP-expressing cells. Thus, BCRP is considered to be a cellular factor that modulates the anti-HIV-1 activity of NRTIs.
Review HCV Antiviral Resistance: The Impact of in vitro Studies on the Development of Antiviral Agents Targeting the Viral NS5B Polymerase
Authors: Tomei Licia , Altamura Sergio , Paonessa Giacomo , De Francesco Raffaele , Migliaccio Giovanni
Published: March 2015

The high prevalence of the disease caused by hepatitis C virus (HCV) and the limited efficacy of interferon-based therapies have stimulated the search for safer and more effective drugs. The development of inhibitors of the HCV NS5B RNA polymerase represents a promising strategy for identifying novel anti-HCV therapeutics. However, the high genetic diversity, mutation rate and turnover of HCV are expected to favour the emergence of drug resistance, limiting the clinical usefulness of polymerase inhibitors. Thus, the characterization of the drug-resistance profile of these antiviral agents is considered crucial for identifying the inhibitors with a higher probability of clinical success. In the absence of an efficient in vitro infection system, HCV sub-genomic replicons have been used to study viral resistance to both nucleoside and non-nucleoside NS5B inhibitors. While these studies suggest that drug-resistant viruses are likely to evolve in vivo, they provide a wealth of information that should help in the identification of inhibitors with improved and distinct resistance profiles that might be used for combination therapy.
In vitro antiviral activity of three enantiomeric sesquiterpene lactones from Senecio species against hepatitis B virus
Authors: Li Haibo , Zhou Changxin , Zhou Linfu , Chen Zhi , Yang Leixiang , Bai Hua , Wu Xiumei , Peng Hua , Zhao Yu
Published: March 2015

Three enantiomeric sesquiterpene lactones were isolated under the bioguidance of the suppression of hepatitis B virus (HBV) surface antigen (HBsAg) from Senecio species, a widely distributed Chinese medicinal herb traditionally used for the treatment of hepatitis B, dermatosis and inflammation. The anti-HBV activity of the purified compounds was measured; all of them showed suppressive activity on the expression of HBsAg and HBV e antigen (HBeAg) in the HepG2.2.15 cell line. Realtime quantitative PCR analysis showed that the studied compounds decreased the number of infectious virions released, but did not inhibit the intracellular HBV DNA. The results suggest that enantiomeric sesquiterpene lactones may possess the potential to work synergistically with other antiviral compounds for the treatment of HBV infection.
In Vitro Activity of SPD754, a New Deoxycytidine Nucleoside Reverse Transcriptase Inhibitor (NRTI), against 215 HIV-1 Isolates Resistant to Other NRTIs
Authors: Bethell Richard C. , Lie Yolanda S. , Parkin Neil T.
Published: March 2015

SPD754 (also known as AVX-754) is a deoxycytidine analogue nucleoside reverse transcriptase inhibitor (NRTI) with antiretroviral activity against HIV-1 and HIV-2 in vitro and against recombinant viruses containing thymidine analogue mutations (TAMs). In order to better establish the activity of SPD754 against HIV-1 containing TAMs, twelve panels of up to twenty clinical isolates with defined TAM combinations were selected from the ViroLogic database. Phenotypic viral susceptibility to SPD754 and five other NRTIs was tested using the PhenoSense HIV assay and expressed as median fold-change compared with a reference strain. In total, 215 isolates were selected, representing four TAM patterns in both pathways by which TAMs accumulate clinically. The presence of five TAMs in the 41, 215 pathway, at codons 41, 67, 210, 215, and 219 of reverse transcriptase (RT), produced a median 1.8-fold reduction in SPD754 susceptibility, compared with fold reductions to zidovudine, lamivudine, abacavir, didanosine and tenofovir of 438, 4.8, 4.5, 1.4 and 3.6, respectively. Five TAMs in the 67, 70, 219 pathway (at codons 41, 67, 70, 215 and 219) reduced SPD754 susceptibility by a median 1.3-fold, compared with fold reductions for the aforementioned NRTIs of 108, 3.2, 3.0, 1.3 and 2.5, respectively. M184V addition reduced SPD754 susceptibility by 1.8-fold in the presence or absence of TAMs. SPD754 retains a substantial proportion of its antiviral activity against HIV-1 containing multiple TAMs, with or without the M184V mutation. These data suggest that SPD754 is a promising new NRTI for the treatment of NRTI-experienced HIV-infected patients.
Novel Phorbol Esters Exert Dichotomous Effects on Inhibition of HIV-1 Infection and Activation of Latent HIV-1 Expression
Authors: Zhong Yu , Matsuya Yuji , Nemoto Hideo , Mori Masao , Saito Haruo , Yamamoto Naoki
Published: March 2015

Two new phorbol esters, NPB-11 (12- O-methoxymethylphorbol-13-decanoate) and NPB-15 (12- O-benzyloxymethylphorbol-13-decanoate) were synthesized. The compounds exhibited potent anti-HIV-1 activity and low cytotoxicity in MT-4 cells by MTT assay even at a high concentration [50% cytotoxic concentrations (CC50) were 8.32 and 4.39 μg/ml, respectively]. Two inhibitors strongly suppressed HIV-1 (IIIB strain) replication in MT-4 cells with a 50% effective concentration (EC50) of 1.3 and 0.27 ng/ml, respectively. NPB-11 efficiently blocked replication of both X4 and R5 HIV-1 in PHA-activated peripheral blood mononuclear cells and MT-4 cells as revealed by p24 assay. The antiviral activity appeared to be mediated, at least partially, by the down-regulation of the expression of CD4 and the HIV-1 co-receptors, CXCR4 and CCR5. The compounds were also capable of selectively up-regulating HIV-1 expression in a variety of latently infected cell lines and inducing cell death in HIV-1 infected cells. The effect of NPBs on the induction of HIV-1 was specifically blocked by nontoxic doses of a protein kinase C blocker, staurosporine. NPB-11 blocked the spread of HIV-1 released from latently infected ACH-2 cells to MT-4 cells in a co-culture system. When combined with AZT, NPB-11 synergistically inhibited HIV-1 replication in MTT assay using MT-4 cells. These data suggest that these agents might be useful in reducing persistent viral reservoirs in patients and as adjuvant therapy in patients treated with HAART.
Synthesis and Biological Activity of 1H-benzotriazole and 1H-benzimidazole Analogues — Inhibitors of the NTPase/Helicase of HCV and of Some Related Flaviviridae
Authors: Bretner Maria , Baier Andrea , Kopańska Katarzyna , Najda Andżelika , Schoof Anna , Reinholz Michael , Lipniacki Andrzej , Piasek Andrzej , Kulikowski Tadeusz , Borowski Peter
Published: March 2015

To improve anti-helical activity of analogues of 1 H-benzotriazole and 1 H-benzimidazole their N-alkyl derivatives were synthesized and tested for anti-helicase activity against enzymes of selected Flaviviridae including hepatitis C virus (HCV), West Nile virus (WNV), Dengue virus (DENV) and Japanese encephalitis virus (JEV). 1- and 2-alkyl derivatives of 4,5,6,7-tetrabromo-1 H-benzotriazole were obtained by direct alkylation of 4,5,6,7-tetrabromo-1 H-benzotriazole with the use of respective alkyl halides in the presence of KOH in methanol, to give a mixture of 1- and 2- isomers, which was separated by flash column chromatography in good yield. The proportion of isomers strongly depended on the reaction time and temperature. 1- and 2-hydroxyethyl and 1- and 2-chloroethyl derivatives of the tetrabromobenzo-triazole were synthesized with the use of 2-bromoethanol and 1-bromo-2-chloroethane respectively as alkylating agents. N-alkylation of this benzotriazole compound enhanced inhibitory activity and selectivity towards the helicase activity of HCV NTPase/helicase. The most active were the 2-methyl, 2-ethyl and 2-propyl derivatives (IC50∼6.5 μM in the presence of DNA as a substrate). Derivatives of the benzotriazole in which hydroxyethyl or chloroethyl replaced the alkyl substituents lost their inhibitory activity. Brominated or methylated benzotriazole N(1) ribosides also did not exert helicase inhibitory activity. Although a number of N(1) and N(2) alkyl derivatives exerted good HCV and WNV helicase inhibitory activity when DNA was used as substrate, the activity was strongly decreased or even disappeared when RNA was used as substrate. The cytotoxicity tests in Vero and HeLa Tat cells showed a substantial decrease of cytotoxicity of N-alkyl derivatives as compared to the parent benzotriazole.
High-Throughput Screening of Low Molecular Weight NS3-NS4A Protease Inhibitors Using a Fluorescence Resonance Energy Transfer Substrate
Authors: Sudo Kenji , Yamaji Kayo , Kawamura Kouich , Nishijima Tomoko , Kojima Naoko , Aibe Kazuhiko , Shimotohno Kunitada , Shimizu Yasuaki
Published: March 2015

Hepatitis C virus (HCV) NS3-NS4A protease is an attractive target for anti-HCV agents because of its important role in replication. An optimized fluorescence resonance energy transfer (FRET) substrate for NS3-NS4A protease, based on the sequence of the NS5A-5B cleavage site, was designed and synthesized. High-throughput screening of in-house compound libraries was performed using a FRET substrate FS10 (MOCAc-DKIVPC-SMSYK-Dnp) and MBP-NS3-NS4A fusion protein. Several hit compounds were found, including YZ-9577 (2-oxido-1,2,5-oxadiazole-3,4-diyl) bis (phenylmethanone) with potent inhibitory activity (IC50=1.6 μM) and good selectivity against other human serine proteases.
The Effect of a Methyl or 2-fluoroethyl Substituent at the N-3 Position of Thymidine, 3′-fluoro-3′-deoxythymi-dine and 1-β-D-arabinosylthymine on Their Antiviral and Cytostatic Activity in Cell Culture
Authors: Balzarini Jan , Celen Sofie , Karlsson Anna , de Groot Tjibbe , Verbruggen Alfons , Bormans Guy
Published: March 2015

Thymidine (Thd), 1-β-D-arabinosylthymine (ara-T) and 3′-fluoro-3′-deoxythymidine (FLT) have been substituted at N-3 by a methyl or a 2-fluoroethyl group. FLT and ara-T are markedly inhibitory against human immunodeficiency virus type 1 (HIV-1) and HIV-2, and herpes simplex virus type 1 (HSV-1) and HSV-2, respectively. Modification at N-3 of these compounds markedly decreases both the antiviral and cytostatic activity of the parent compounds FLT and ara-T except for N-3-(methyl)-Thd that proved highly cytostatic for murine leukaemia L1210 cells. The decreased biological activity of the N-3-substituted pyrimidine nucleo-side analogues coincides with a significantly lower affinity of the modified Thd analogues for the cellular and viral (activating) nucleoside kinases.
Inhibitory Efficacy of CycloSal-Nucleoside Monophosphates of Aciclovir and Brivudin on DNA Synthesis of Orthopoxviruses
Authors: Sauerbrei Andreas , Meier Chris , Meerbach Astrid , Wutzler Peter
Published: March 2015

Previous studies have shown that cycloSaligenyl-monophosphate ( cycloSal-MP) derivatives of aciclovir (ACV), penciclovir (PCV) and brivudin (BVDU) can act as inhibitors of vaccinia virus and cowpox virus replication in vitro. The aim of the present study was to evaluate the inhibatory efficacy on DNA synthesis in vaccinia and cowpox viruses of several cycloSal-pro-nucleotides of ACV and BVDU, which have proven activity against pox viruses. Viral DNA was quantified in treated and non-treated virus-infected cells by semi-quantitative PCR on the basis of the haemag-glutinin protein gene of orthopoxviruses. As result, an inhibitory efficacy on vaccinia and cowpox virus DNA replication could be demonstrated for 3-methyl- cycloSal-ACVMP, 5-H- cycloSal-ACVMP, 6-chloro-7-ECM- cycloSal-3′-OH-BVDUMP, and 6-chloro-7-methyl- cycloSal-3′-OH-BVDUMP. At concentrations of 32–128 mg/ml, 3-methyl- cycloSal-ACVMP and 6-chloro-7-ECM- cycloSal-3′-OH-BVDUMP inhibited synthesis of viral DNA to a similar extent as the well-known inhibitors of pox viruses, cidofovir and 5-iodo-dUrd (deoxyuridine). When concentrations of 128 mg/ml were administered, both test substances diminished the amount of viral genome copies by ≥4 log10 corresponding to ≥99.99% reduction. In conclusion, selected cycloSal-pro-nucleotide derivatives of ACV and BVDU can inhibit orthopoxviral DNA synthesis. The high inhibitory efficacy on both replication of viral DNA and infectious viral particles in cell cultures makes these compounds promising candidates for in vivo experiments.
Indolyl Aryl Sulphones as HIV-1 Non-Nucleoside Reverse Transcriptase Inhibitors: Synthesis, Biological Evaluation and Binding Mode Studies of New Derivatives at Indole-2-carboxamide
Authors: De Martino Gabriella , La Regina Giuseppe , Ragno Rino , Coluccia Antonio , Bergamini Alberto , Ciaprini Chiara , Sinistro Anna , Maga Giovanni , Crespan Emmanuele , Artico Marino , Silvestri Romano
Published: March 2015

New non-nucleoside reverse transcriptase inhibitors (NNRTIs) that are active against the commonly occurring mutations of HIV are urgently needed for the treatment of AIDS. We synthesized new NNRTIs of the indolyl aryl sulphone (IAS) family, which are endowed with high antiviral potency against HIV-1 wt (wild-type), and the Y181C and K103N-Y181C drug resistant mutant strains. Several new compounds were highly active in lymphocytes infected with primary isolates carrying the K103N-V108I-M184V and L100I-V108I mutations. The design of new IASs was based on three-dimensional quantitative structure-activity relationship (3D QSAR) studies and docking simulations. A cross-docking study was also undertaken to gain some insights in to the binding mode of the newly synthesized IASs in the wt and mutated isoforms of reverse transcriptase.
Synthesis and Antiviral Evaluation of Alkoxyalkyl Esters of Phosphonopropoxymethyl-Guanine and Phosphonopropoxymethyl-Diaminopurine
Authors: Ruiz Jacqueline C , Aldern Kathy A , Beadle James R , Hartline Caroll B , Kern Earl R , Hostetler Karl Y
Published: March 2015

Phosphonopropoxymethyl-guanine is the methylene phosphonate analogue of acyclovir. Although not highly active against HSV, 4–38 µM of phosphonopropoxymethyl-guanine has been reported to be active against human and murine cytomegalovirus. Recently we found that cido-fovir, when esterified with alkoxyalkyl moieties, showed greatly increased antiviral activity against cytomegalovirus, herpes simplex virus and orthopoxviruses, in vitro. The alkoxyalkyl esters of cidofovir are orally active in murine models of human and murine cytomegalovirus and orthopoxviruses in vivo. To see if the antiviral activity of phosphonopropoxymethyl-guanine, phosphonopropoxymethyl-diaminopurine and phosphonopropoxymethyl-N6-cyclopropyl-diaminopurine could be increased by this approach, we synthesized their hexadecyloxypropyl-and octadecyloxyethyl- esters and evaluated antiviral activity and cytotoxicity in cells infected with HSV-1 and HCMV, in vitro. Marked increases in antiviral activity were noted in the alkoxyalkyl esters of phosphonopropoxymethyl-guanine. Alkoxyalkyl esters of diaminop-urine and N6-cyclopropyl-diaminopurine showed slight increases in activity against HSV-1 and marked increases in activity against HCMV. The results suggest that esterification with alkoxyalkyl moieties may be a generally useful way to increase antiviral activity of nucleoside phosphonates.
Antiviral Chemistry & Chemotherapy's Current Antiviral Agents FactFile 2006 (1st Edition)
Authors: De Clercq Erik , Brancale Andrea , Hodge Anthony Vere , Field Hugh J
Published: March 2015

The number of useful antiviral compounds is rapidly expanding. The currrent antiviral agents FactFile is a convenient key to the vital statistics of antiviral compounds to be used as an aide mémoire when reading or writing antiviral literature. A mini-portrait is provided for each of the antiviral compounds. The minimum criteria for inclusion of new compounds in the FactFile is the granting of an investigational new drug application with the realistic potential for medical or veterinary application. Several compounds that were subsequently withdrawn from further development are also included because of their historical importance or particular interest. The compounds are listed alphabetically according to their generic names together with systematic chemical names, common names and chemical structures. The compounds are grouped by virus targets; thus, the list is sub-divided into inhibitors of DNA viruses, RNA viruses, and retroviruses. The authors welcome comments and suggestions to be incorporated in future editions of the FactFile.
Silencing of HIV-1 Gene Expression by Two Types of siRNA Expression Systems
Authors: Hayafune Masaaki , Miyano-Kurosaki Naoko , Park Wee-Sung , Moori Yuka , Takaku Hiroshi
Published: March 2015

The RNA interference (RNAi) phenomenon is a recently discovered process in which the introduction of a double-stranded RNA (dsRNA) into cells causes the specific degradation of mRNA containing the same sequence. We designed mammalian expression vectors that direct the synthesis of small interfering RNA (siRNA)-like transcripts and examined them for their siRNA-mediated gene interference targeting the env gene (NL4–3:7490–7508, E7490). We constructed siRNA expression vectors for two different strands (sense and antisense; tandem promoter) and for siRNA expressed from the short hairpin RNA (shRNA). The inhibition efficacy on HIV–1 replication differed between these two vectors. Notably, the shRNA vector pU6-env-shRNA inhibited p24 production more effectively than the tandem promoter expression vector pU6-env-siRNA. Furthermore, we examined the ability of lentiviral vectors expressing shRNA to suppress HIV-1 expression in HIV-1-infected SupT1 cells. The env-shRNA (E 7490) almost completely suppressed HIV-1 expression in infected cells for up to 15 days.
Rimantadine and Oseltamivir Demonstrate Synergistic Combination Effect in an Experimental Infection with Type a (H3N2) Influenza Virus in Mice
Authors: Galabov Angel S , Simeonova Lora , Gegova Galina
Published: March 2015

We studied the combination effect of rimantadine hydrochloride and oseltamivir phosphate on mice infected with influenza A/Aichi/2/68 (H3N2) virus. Compounds were simultaneously administered in a 5-day-treatment course, starting 4 h before intranasal infection with 10 or 20 viral 50% mouse lethal doses. Initially, we tested combinations of oseltamivir (0.05, 0.1 and 0.2 mg/kg/day) and rimantadine (2.5, 5.0 and 7.5 mg/kg/day). Significant differences were recorded between combinationtreated groups, and groups with separately applied compounds and the placebo group, such as: protection index of oseltamivir with 5.0 or 7.5 mg/kg rimantadine varied between 34–41% and 43–87%, respectively, whereas the individual effects of oseltamivir, 5 mg/kg of rimantadine and 7.5 mg/kg of rimantadine were 0–10%, 0% and 18.7–29.6%, respectively; mean survival time in combination-treated groups was lengthened by 3.1–6.9 days, in oseltamivir groups by 0–1.9 days, and in rimantadine groups by 0.8–1.3 days at 5 mg/kg and 2.6–3.2 days at 7.5 mg/kg. The three-dimensional method of Prichard and Shipman characterized the combination effect as synergistic. Further, we studied the activity of 0.05 mg/kg/day of oseltamivir combined with 5 mg/kg of rimantadine. Lung virus titre in Madin Darby canine kidney cells, lung index and consolidation score proved the high effectiveness of the combination. When compared with the placebo group, a 2.8 log10 lower titre of 50% cell culture infectious dose (CCID50) was recorded in the combination-treated group at 48–60 h post-infection (the peak of lung virus growth). This is in contrast to the 0.1–1.0 log10 and 1.1–1.4 log10 reduction in CCID50 titre observed in the oseltamivir and rimantadine groups, respectively. These data emphasize the high anti-influenza A potential of the combination.
α-Glucosidase Inhibitors Have a Prolonged Antiviral Effect against Hepatitis B Virus through the Sustained Inhibition of the Large and Middle Envelope Glycoproteins
Authors: Simsek Ender , Lu Xuanyong , Ouzounov Serguey , Block Timothy M , Mehta Anand S
Published: March 2015

Previous work has shown that the secretion of enveloped hepatitis B virus (HBV) DNA and the HBV middle envelope protein (MHBs) are sensitive to glucosidase inhibition. Here, it is shown that HBV DNA secretion remains depressed after the removal of the glucosidase inhibitor and long after glucosidase function returns to normal. For example, glycoprocessing and the secretion of α-1 anti-trypsin returned to normal within 3 h of the removal of the glucosidase inhibitor. In contrast, the secretion of HBV did not return to normal for more than 7 days after the removal of the inhibitor. Consistent with the inhibition of HBV virion secretion, the levels of HBV L and HBV M proteins were also reduced by treatment with the glucosidase inhibitor and remained reduced for 7 days after compound withdrawal. The implications of the prolonged antiviral effect against HBV and the use of glucosidase inhibitors as antiviral agents are discussed.
Five Years of Progress on Cyclin-Dependent Kinases and other Cellular Proteins as Potential Targets for Antiviral Drugs
Authors: Schang Luis M , St. Vincent Mireille R , Lacasse Jonathan J
Published: March 2015

In 1997–1998, the pharmacological cyclin-dependent kinase (CDK) inhibitors (PCIs) were independently discovered to inhibit replication of human cytomegalovirus, herpes simplex virus type 1 and HIV-1. The results from small clinical trials against cancer were then suggesting that PCIs could be safe enough to be used clinically. It was thus hypothesized that PCIs could have the potential to be developed as novel antivirals targeting cellular proteins. Consequently, Antiviral Chemistry & Chemotherapy published in 2001 the first review on the potential of CDKs, and cellular proteins in general, as potential targets for antivirals. The viral functions inhibited by PCIs, or their cellular targets, were then just starting to be characterized. The antiviral spectrum of PCIs and their effects on viral disease were still mostly untested. Even their actual specificity was not yet completely characterized. In addition, cellular proteins were not accepted as valid targets for antivirals. Significant progress has been made in the last 5 years in understanding the antiviral activities of PCIs and the potential roles of cellular proteins in general as targets for antivirals. The first clinical trials of the antiviral activities of PCIs and other inhibitors of cellular protein kinases have now been scheduled. Herein, we review the progress made since the publication of the first review on PCIs as potential antiviral drugs and on CDKs, and cellular proteins in general, as potential targets for antiviral drugs. We also highlight the major issues that still need to be addressed before PCIs or other drugs targeting cellular proteins can be developed as clinical antivirals.