bluuebunny/crossref_metadata_2025 huggingface dataset:
The Thiocarboxanilides UC-10 and UC-781 Have an Additive Inhibitory Effect against Human Immunodeficiency Virus Type 1 Reverse Transcriptase and Replication in Cell Culture When Combined with other Antiretroviral Drugs
Authors: Balzarini J , De Clercq E
Published: May 2015

The thiocarboxanilides represent a structural class of potent and selective human immunodeficiency virus type 1 (HIV-1)-specific reverse transcriptase (RT) inhibitors. Combinations of the clinical candidate thiocarboxanilides UC-10 (oxime ether derivative) and UC-781 (pentenyloxy ether derivative) with a variety of nucleoside RT inhibitors (NRTIs) and non-nucleoside RT inhibitors (NNRTIs), two HIV protease inhibitors and one fusion/uncoating inhibitor were evaluated for their inhibitory effects on HIV-1 RT activity and HIV-1 replication in CEM cell cultures. The inhibitory activity of the NNRTIs including UC-10, UC-781, nevirapine, BHAR α-APA, 8-chloro-TIBO, MKC-442 and the quinoxaline HBY 097 against HIV-1 RT was highly dependent on the nature of the template/primer used in the HIV-1 RT reaction. However, fractionary inhibitory concentration (FIC) indexes for all drug concentrations evaluated in the combination experiments of UC-781 and the other NNRTIs fell within the range 0.5–1.5. This points to a predominantly additive effect of the thiocarboxanilides and other NNRTIs in the inhibition of HIV-1 RT. Similar FIC indexes were observed for the combination of UC-781 with the NRTI triphosphates AZT-TP, d4T-TP, ddCTP, ddATP and 3TC-TP and the NRTI diphosphate PMEApp against HIV-1 RT. All these drug combinations showed similar additive inhibitory effects on HIV-1 replication in cell culture. Also, the combinations of UC-10 or UC-781 with the protease inhibitors Ro31–8959/008 and ABT 84538.0 and the fusion/uncoating inhibitor bicyclam JM 3100 showed an additive effect (FIC within the 0.5–1.5 range). Thus, irrespective of the nature of the drugs, their combination with the thiocarboxanilides proved merely additive. In no case were antagonistic anti-HIV activity or increased cytotoxicity observed. In conclusion, thiocarboxanilides combined with a variety of clinically used anti-HIV agents result in additive anti-HIV activity.
Anti-Human Immunodeficiency Virus Activity, Bioavailability and Drug Resistance Profile of the Novel Proteinase Inhibitor MDL 74,695
Authors: Taylor DL , Ahmed PS , Brennan TM , Bridges CG , Tyms AS , Van Dorsselaer V , Tarnus C , Hornsperger J-M , Schirlin D
Published: May 2015

MDL 74,695, a novel dipeptide-like compound containing the ‘difluorostatone type’ transition state mimic and a potent inhibitor of the human immunodeficiency virus (HIV) proteinase, was investigated for anti-HIV activity in vitro. The compound showed selective inhibition of both HIV-1 and HIV-2 in MT-4 cells. A potent antiviral effect against a range of clinical isolates of HIV-1 cultured in human peripheral blood mononuclear cells and primary monocytes was also demonstrated. The antiviral activity of MDL 74,695 against viruses resistant to a range of reverse transcriptase inhibitors was equivalent to the wild-type. In rats MDL 74,695 (30 mg kg−1) was 4.9% orally bioavailable and maintained levels above the in vitro 50% inhibitory concentration (IC50) for approximately 3 h. Viruses with reduced sensitivity to MDL 74,695 and saquinavir were selected in cell culture by continuous passage in increasing drug concentrations, and first appeared after 20 and 17 passages, respectively. Amino acid changes were identified at positions 48 (glycine to valine), 50 (isoleucine to valine) and 82 (valine to either isoleucine or alanine) in various combinations for MDL 74,695-resistant viruses. For saquinavir-resistant viruses changes were identified at positions 48 (glycine to valine) and 90 (leucine to methionine). Studies using MDL 74,695, saquinavir and a third proteinase inhibitor indinavir, indicated that virus selected in the presence of MDL 74,695, with amino acid exchanges at positions 48 and 82 showed cross-resistance to saquinavir. However, viruses selected in the presence of MDL 74,695 with amino acid exchanges at positions 50 and 82 showed no significant change in sensitivity to saquinavir. Likewise, viruses selected in the presence of saquinavir with amino acid exchanges at positions 48 and 90 remained sensitive to MDL 74,695. All viruses selected after growth in the presence of either MDL 74,695 or saquinavir showed little or no resistance to indinavir.
Synthesis of Nucleosidyl Rifamycins as Inhibitors of Human Immunodeficiency Virus Type 1
Authors: Bartolucci C , Cellai L , Mannina L , Marzano M , Brufani M , Filocamo L , Messina S , Brizzi V , Benedetto A , Di Caro A
Published: May 2015

In the search for potential nucleoside/non-nucleoside mixed type inhibitors of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase, we synthesized a new set of rifamycin S derivatives, containing AZT connected via its hydroxyl at 5′ C, through a spacer, to the third C of rifamycin S. The length of the spacer was eight, nine or 14 atoms. Rifamycin S was also used in its 21, 23-O, O-isopropylidene derivative form, and in one case thymidine replaced AZT. These nucleosidyl rifamycins were weak inhibitors of isolated HIV-1 reverse transcriptase. The inhibitory power was weak most probably because their large molecular volume hindered the inhibition process. With the exception of the thymidine derivative, the AZT derivatives, at concentrations in the range 0.04–0.07 μM, proved non-toxic and inhibited the replication of HIV-1 in C8166 T lymphocytes. This activity appears to be owing to AZT released by the derivatives upon hydrolysis in solution. The present compounds require further development as mixed type reverse transcriptase inhibitors and can be considered non-toxic lipophilic prodrugs of AZT.
Biological activity and DNA Sequence Specificity of Synthetic Carbamoyl Analogues of Distamycin
Authors: Alfieri A , Animati F , Arcamone F , Bailly C , Crisanti A , Dentini M , Felicetti P , lafrate E , Lombardi P , Manzini S , Rossi C , Waring MJ
Published: May 2015

A new penta(N-methylpyrrole carboxamide) analogue of the antibiotic distamycin has been synthesized in which the N-terminal formylamino group was replaced by a carbamoyl moiety. It was substantially more stable than distamycin in aqueous solution and bound to DNA with about the same affinity constant. It had an exemplary margin of selectivity against herpes simplex virus type 1-infected HEp-2 cells in culture compared to uninfected control cells, and was equipotent with distamycin. For comparison, data for analogues containing fewer N-methylpyrrole carboxamide units and/or lacking the carbamoyl replacement are presented. Extensive DNase I footprinting experiments were conducted and revealed that all the distamycin analogues bound to AT-rich nucleotide sequences in three different restriction fragments, irrespective of how many pyrrole rings or which terminal moiety they contained. However, the relative strength of footprints differed significantly among the various compounds, though the apparent size of the binding site did not. With semi-synthetic DNA containing inosine and 2,6-diaminopurine residues in place of guanosine and adenine, respectively, the compounds recognized new binding sites composed of IC-rich clusters and were excluded from binding to their canonical sites. This showed that the process of specific sequence recognition was critically dominated by the placement of the purine 2-amino group in the minor groove of the double helix.
Anti-Herpes Simplex Virus Type 1 Activity of Humic Acid-Like Polymers and Their O-Diphenolic Starting Compounds
Authors: Helbig B , Klöcking R , Wutzler P
Published: May 2015

Phenolic polymers of the humic acid (HA) type, like other polyanionic substances, are inhibitors of herpes simplex virus type 1 (HSV-1) replication. The antiviral potency of the low molecular weight (MW) phenolic starting compounds has not been investigated systematically up to now. To reveal possible relationships between the chemical structure of o-diphenolic starting compounds and the anti-HSV-1 activity of HA-like polymers, nine polymers were synthesized by oxidation of the corresponding o-dihydroxybenzene derivatives. They were characterized by MW distribution, Fourier transform infra-red spectra and functional group analysis. Using an XTT-based tetrazolium reduction assay, both the low MW starting compounds and the synthesized polymers were examined for their antiviral and cytotoxic activities in HSV-1-infected Vera cells. The results demonstrate that most of the starting compounds failed to inhibit herpesvirus replication. The polymeric oxidation products (OP), however, developed detectable anti-HSV-1 activity with IC50 values in the range 2.3 [the OP of 3,4 dihydroxycinnamic acid (caffeic acid); KOP] to 42.1 μg mL−1 (3,4-dihydroxy-toluene OP). The CC50 of polymers varied between 40.8 (3,4-dihydroxybenzaldehyde OP) and >128 μg mL−1 (most polymers). Functional group analysis revealed that the presence of carboxylic groups in the starting compounds enhanced the antiviral activity and reduced the cytotoxicity of polymers. The introduction of a C=C double bond into the side chain [i.e. caffeic acid; 3-O-(3,4-dihydroxycinnamoyl)-d-chinic acid (chlorogenic acid; CH)] yielded the most effective polymers (KOP, CHOP). These may be considered as leader substances for HSV-1 inhibitors of the HA type.
Penciclovir Pharmacokinetics and Distribution to the Brain and Muscle of Rats, Studied by Microdialysis
Authors: Borg N , Ståhle L
Published: May 2015

Famciclovir, the oral form of penciclovir, is a potent, highly selective antiherpesvirus agent licenced for the treatment of herpes zoster (shingles). Some herpesviruses are prone to infect the central nervous system. To obtain guidance for the possible treatment of herpes encephalitis it is important to study the extent of transport of antiviral agents into the brain. We have used microdialysis to sample the unbound extracellular concentration of penciclovir in the gastrocnemic muscle (which corresponds directly to plasma free concentrations) and in the brain of rats under halothane anaesthesia. Penciclovir (50 mg kg−1) was given intravenously (i.v.) and samples were taken for 5 h after administration. The AUC (area under the time versus concentration curve) (0–5 h) of penciclovir in the brain was 0.096±0.018 (mean±SEM) of the AUC in muscle while the mean ratio of brain to muscle concentration 5 h post-injection was 0.1 80±0.084. Famciclovir given per os to rat at a dose of 1 20 mg kg−1 resulted in a concentration ratio for penciclovir between brain and muscle of 0.415±0.078 at 5 h after administration, while the AUC ratio (0–5 h) was 0.143±0.012. Both of these are higher than after i.v. injection of penciclovir. Penciclovir and famciclovir were also administrated by i.v. infusion (60 and 80 mg kg−1 h−1 respectively). Famciclovir administration (AUC 0.075±0.025 mmol h L−1) did not increase penciclovir transport to the brain compared with penciclovir administration (AUC 0.163±0.018 mmol h L−1).
Pleiotropic Effects of Small Peptides Corresponding in Sequence to the Cytoplasmic Domain of the Influenza Virus Haemagglutinin on Influenza, Vesicular Stomatitis and Sindbis Viruses
Authors: Loewy A , Gorka J , Mo J , Ryan C , Schlesinger MJ
Published: May 2015

Studies on the antiviral effects of short peptides of six to 10 amino acids that correspond in sequence to the cytoplasmic domains of enveloped virus transmembrane glycoproteins have been extended to include additional kinds of assay in order to determine a site for inhibition of virus replication. Based on these experiments, the antiviral activity previously described for a decapeptide with the influenza virus haemagglutinin HA2 C-terminal sequence was not specific for influenza virus and the integrity of newly released, extracellular vesicular stomatitis virus particles was affected by the peptide. A shortened, six amino acid form of this peptide inactivated cell-free preparations of influenza, vesicular stomatitis and Sindbis viruses and also bound effectively to virus-encoded structural proteins. For this virus-protein interaction, the peptide sequence was highly specific with respect to its hydrophobicity and net ionic charge.
Human Immunodeficiency Virus Resistance to AZT in MOLT4/8 Cells is Associated with a Lack of AZT Phosphorylation and is Bypassed by AZT-Monophosphate SATE Prodrugs
Authors: Cinatl J , Gröschel B , Zehner R , Cinatl J , Périgaud C , Gosselin G , Imbach J-L , Doerr HW
Published: May 2015

Human T lymphoid MOLT4/8 cells were grown continuously for more than 2 years in a medium containing 3′-azido-2′,3′-dideoxythymidine (zidovudine; AZT) at a concentration of 250 μM. These cells, designated MOLT-4/8rAZT250, were used to test the cytotoxic and antiviral activity of AZT. Intracellular accumulation of AZT, expression of the multidrug resistance 1 (MDR-1) gene, thymidine kinase (TK) gene and activity of the TK enzyme in cellular extracts were measured. The results showed that both the cytotoxic and antiviral activity of AZT were significantly lower in MOLT4/8rAZT250 than in MOLT4/8 cells; concentrations required to inhibit 50% production of the p24 human immunodeficiency virus type 1 (HIV-1) antigen of two laboratory strains were at least 100-fold higher in resistant cells. The MDR-1 gene was not expressed in the resistant cells. TK mRNA expression was significantly lower in the resistant than in the sensitive cells. TK enzymatic activity for deoxythymidine phosphorylation was impaired in MOLT4/8rAZT250 cells compared to the sensitive cells. AZT was phosphorylated only in the sensitive cells whereas no phosphorylation of AZT was found in the resistant cells. We tested whether several AZT-monophosphate triesters, which bypass cellular TK, could overcome resistance to the cytotoxic and antiviral activity of AZT. The bis( t-butylSATE) phosphotriester derivative of AZT showed comparable cytotoxic and antiviral activity in sensitive and resistant cells. The results demonstrated that MOLT4/8rAZT250 cells exert resistance to the anti-HIV activity of the drug mainly owing to the lack of AZT phosphorylation and that resistance may be bypassed by using AZT-monophosphate SATE prodrugs.
Inhibition of Human Immunodeficiency Virus Type 1 Reverse Transcriptase by Degradation Products of Ceftazidime
Authors: Baertschi SW , Cantrell AS , Kuhfeld MT , Lorenz U , Boyd DB , Jaskunas SR
Published: May 2015

Previous work by Hafkemeyer et al. (1991) [ Nucleic Acids Research19: 4059–4065] indicated that a degradation product of ceftazidime, termed HP 0.35, was active against the RNase H activity of human immunodeficiency virus type 1 (HIV-1) and feline immunodeficiency virus (FIV) reverse transcriptase (RT) in vitro. Attempting to repeat these results, we isolated HP 0.35 from an aqueous degradation of ceftazidime and, after careful purification, we found HP 0.35 to be essentially inactive against both the polymerase and RNase H domains of HIV-1 RT (IC50 of >100 μg mL−1). During the investigation we discovered that polymeric degradation products of ceftazidime inhibited both the polymerase and, to a greater extent, the RNase H activities of HIV-1 RT in vitro (IC50 approximately 0.1 and 0.01 μg mL−1, respectively). Subjecting HP 0.35 to conditions under which it could polymerize induced inhibitory activity similar to that of the polymeric ceftazidime degradation products. It is proposed that the previously reported activity of HP 0.35 may have resulted from the presence of low levels of polymeric material either from incomplete purification or from polymerization of HP 0.35 during storage or in vitro testing.
In vitro and Animal Models for Antiviral Therapy in Papillomavirus Infections
Authors: Stanley MA , Masterson PJ , Nicholls PK
Published: May 2015

The need for antiviral therapies for papillomavirus infections is well recognized but the difficulties of reproducing the infectious cycle of papillomaviruses in vitro has hindered our understanding of virus-cell interactions and the regulation of viral gene expression during permissive growth. Recent advances in understanding the temporal expression and function of papillomavirus proteins has enabled consideration of a targeted approach to papillomavirus chemotherapy and in particular the inhibition of viral replication by targeting the E1 and E2 proteins. There are in vitro culture systems available for the screening of new chemotherapeutic agents, since significant advances have been made with culture systems which promote epithelial differentiation in vitro. However, to date, there are no published data which show that virions generated in vitro can infect keratinocytes and initiate another round of replication in vitro. In vivo animal models are therefore necessary to assess the efficacy of antivirals in preventing and treating viral infection, particularly for the low-risk genital viruses which are on the whole refractory to culture in vitro. Although papillomaviruses affect a wide variety of hosts in a species-specific manner, the animals most useful for modelling papillomavirus infections include the rabbit, ox, mouse, dog, horse, primate and sheep. The ideal animal model should be widely available, easy to house and handle, be large enough to allow for adequate tissue sampling, develop lesions on anatomical sites comparable with those in human diseases and these lesions should be readily accessible for monitoring and ideally should yield large amounts of infectious virus particles for use in both in vivo and in vitro studies. The relative merits of the various papillomavirus animal models available in relation to these criteria are discussed.
The Inhibitory Activity of Diazinyl-Substituted Thiourea Derivatives on Human Immunodeficiency Virus Type 1 Reverse Transcriptase
Authors: Heinisch G , Matuszczak B , Pachler S , Rakowitz D
Published: May 2015

Starting from 2-(2-aminoethyl)pyridine, a series of N-diazinyl-N′-[2-(2-pyridyl)ethyl]thioureas was prepared via the (2-pyridyl)ethylisothiocyanate and was screened as non-nucleoside human immunodeficiency virus type 1 reverse transcriptase inhibitors. Derivatives bearing a 3-pyridazinyl or a 4-pyrimidinyl moiety turned out to be the most potent compounds. However, they exhibited less activity than nevirapine or trovirdine.
Antiviral Treatment: From Concept to Reality
Authors: Boon R
Published: May 2015

The initial development of antiviral compounds was slow, with the first clinical antiviral agent not available until the 1960s. Early development was hindered by the lack of understanding of virus life-cycles and the absence of an assay system for antiviral activity. The appearance of the first assay system, the fertilized egg yolk sac, led to the identification of methisazone. This was the first antiviral agent to be used clinically. The improvement in antiviral assay systems, and the start of directed research programmes led to the development of the first antiherpes agents idoxuridine, trifluorothymidine (TFT) and vidarabine. However, all of these agents were associated with significant adverse effects. Antiherpes therapy took a major step forward with the development of the acyclic nucleoside analogue, aciclovir. Aciclovir is much more potent than previous antiherpesvirus agents. Its mode of action results in selectivity for herpesvirus-infected cells, thus significantly reducing the side-effects seen with earlier agents. Because of this, it became the standard therapy for herpes simplex virus type 1 (HSV-1), HSV-2 and varicella zoster virus infections. However, the bioavailability of oral aciclovir is poor, requiring high and frequent doses. This led to the search for better absorbed agents and to the development of two prodrugs, famciclovir and valaciclovir. Both famciclovir and valaciclovir offer much improved bioavailability of the nucleosides penciclovir and aciclovir, compared with aciclovir. Once in the body the conversion of valaciclovir to aciclovir means that the two agents have similar pharmacokinetic properties. Similarly, famciclovir is converted to penciclovir in the body. Penciclovir, when phosphorylated in virus-infected cells, persists within the cell for a much longer period than aciclovir triphosphate. Over the last 10 years we have seen an acceleration in the development of antiviral agents and some major advances in antiviral therapy. Many challenges, however, still lie ahead.
Current and Future Management of Herpes Zoster
Authors: Johnson RW
Published: May 2015

Herpes zoster (shingles) is a common disease affecting approximately three in 1000 of the population per year and up to 10 in 1000 per year in the elderly population. This incidence is likely to increase as the proportion of elderly people in the general population increases and various forms of immunosuppression become more common, e.g. following organ transplantation. Management of both the acute and chronic pain is probably the most important part of caring for shingles patients. Antiviral therapy, anti-inflammatory steroids and sympathetic nerve blocks are the main measures used during the acute phase to prevent the development of postherpetic neuralgia (PHN). Antiviral agents given early in the acute phase of herpes zoster are generally the therapy of choice and there is also growing evidence for benefit with tricyclic antidepressants. Pain relief once PHN has developed is generally much less effective. Many classes of drug have been investigated for the management of PHN and some have been found to be helpful in some patients. There is as yet no generally effective agent, however preventive antiviral therapy early in the course of herpes zoster is recommended for all elderly patients since they have a high risk of developing severe PHN.
Pain and its Assessment in Herpes Zoster
Authors: Dworkin RH
Published: May 2015

Pain typically accompanies acute herpes zoster. In a proportion of patients, herpes zoster pain persists well beyond rash healing. This persisting pain is termed post-herpetic neuralgia (PHN). Because of the substantial personal and economic burdens caused by PHN, studies of the pathophysiology of herpes zoster pain and of the efficacy of antiviral treatment in reducing prolonged pain are of great importance. Different methods have been used to examine pain in research on herpes zoster and in clinical trials, making it difficult to compare across studies. There is substantial evidence, however, that demonstrates the importance of distinguishing acute pain from PHN. Several differences have been found between acute herpes zoster pain and PHN, including pathophysiological findings, risk factors and pain quality. Recommendations for the design and analysis of future trials of antiviral agents in herpes zoster have been recently proposed. These include a definition of PHN and recommended secondary end points for future trials. Adopting these recommendations in future research on herpes zoster pain, and in the design and analysis of future trials, will facilitate comparisons across studies of the pathophysiology and prevention of PHN.
Genital Herpes: Management Issues for the Next Century
Authors: Sacks SL , Wilson BR
Published: May 2015

Genital herpes (GH) is caused by herpes simplex virus (HSV) types 1 and 2. HSV-2 is more commonly the causal agent, and is responsible for 98% of recurrences. A first episode may become clinically apparent within 2–21 days post-infection. Symptomatic recurrences present as vesiculo-ulcerative lesions, which typically resolve within 5 days. The overall recurrence rate for GH is 60–90%. Asymptomatic shedding occurs in both sexes on 1–5% of days. Aciclovir, famciclovir and valaciclovir are the approved drugs for GH, and one of these should be used in all first episodes. Episodic treatment is often used where recurrences are infrequent and easily recognized. Oral treatment with famciclovir, aciclovir or valaciclovir reduces the duration of lesions, viral shedding and uncomfortable symptoms. Patients with frequent or problematic recurrences are candidates for prophylaxis with antivirals which suppress both symptomatic and asymptomatic reactivation. A herpes diagnosis often leaves patients emotionally vulnerable, concerned about asymptomatic shedding and fearful of transmission to sexual partners. GH can be devastating, occasionally leading to clinical depression and/or suicidal ideation. Patients commonly fear discussing GH with their physician or partners, but doing so is vitally important for their psychological health. Counselling to assist in this process is helpful. In summary, good management of GH requires careful attention to proper diagnosis and therapy, with psychosocial intervention: all three provided in the context of accurate information.
Hepatitis B: Treatment for the 21st Century
Authors: Bowden S
Published: May 2015

Hepatitis B virus (HBV) infection constitutes a worldwide public health problem, causing both acute and chronic liver infections. Although a vaccine has been developed that is effective in preventing HBV infection, this is of no benefit to the estimated 350 million carriers of the virus. Chronic hepatitis B infection may lead to cirrhosis of the liver and hepatocellular carcinoma. Therefore, there is a clear need for antiviral therapy. Alpha interferon was the first therapeutic agent used against HBV infection. However, its lack of efficacy in many patients and significant adverse event profile has prompted the development of alternative therapies. Nucleoside analogues are currently being investigated as potential anti-HBV agents, with two compounds, famciclovir and lamivudine, undergoing Phase III clinical trials of long-term use. In preclinical studies using the Pekin duck model for hepatitis B, both compounds have been found to reduce the amount of serum duck HBV DNA to sub-detectable levels during therapy. However, once therapy was stopped, the virus returned to pretreatment levels, making long-term treatment necessary. In clinical studies in chronic hepatis B patients, treatment with these agents also resulted in a significant reduction of HBV DNA levels but, again, the return of HBV DNA after discontinuing treatment indicates the need for long-term therapy. The need for long-term treatment means that the virus may develop resistance to the antiviral agents. Resistance mutations to both famciclovir and lamivudine are now being reported after treatment of chronic HBV infection with these agents. Combination therapy may be a strategy to overcome the development of resistance. Therapeutic vaccines and new antiviral agents are also being developed.
Thiazolo[4,5-d]Pyrimidines. Part II. Synthesis and Anti-Human Cytomegalovirus Activity in Vitro of Certain Acyclonucleosides and Acyclonucleotides Derived from the Guanine Analogue 5-Aminothiazolo[4,5-d]Pyrimidine-2,7(3H,6H)-Dione
Authors: Revankar GR , Ojwang JO , Mustain SD , Rando RF , De Clercq E , Huffman JH , Drach JC , Sommadossi J-P , Lewis AF
Published: May 2015

The synthesis and in vitro antiviral activity of certain hydroxyalkoxymethyl, hydroxyalkyl, hydroxyalkenyl and phosphonoalkenyl derivatives of the guanine congener 5-aminothiazolo-[4,5- d]pyrimidine-2,7(3 H,6 H)-dione are reported. The compounds of this study were selected for their structural similarity to acyclonucleosides with known anti-herpesvirus activity. 5-Amino-3-[(Z)-4-hydroxy-2-buten-1-yl]thiazolo[4,5- d]pyrimidine-2,7(3 H,6 H)-dione was the only member of the series to display significant in vitro activity against human cytomegalovirus (HCMV); however, this compound did not inhibit other herpesviruses, human immunodeficiency virustype 1 or murine cytomegalovirus. It was found to have a cytotoxicity profile similar to that of ganciclovir (DHPG). The antiviral effect was found to be sensitive to the initial viral input and the time of addition during the virus replication cycle. Significantly, the compound was found to have equal anti-HCMV activity, against standard virus strains, to DHPG, but also showed potent activity against DHPG-resistant virus strains, except for a strain mutated in the UL97 (phosphotransferase) gene.
Synthesis and Biological Evaluation of 5H-Indolo [3,2-b][1,5]Benzothiazepine Derivatives, Designed as Conformationally Constrained Analogues of the Human Immunodeficiency Virus Type 1 Reverse Transcriptase Inhibitor L-737,126
Authors: Silvestri R , Artico M , Bruno B , Massa S , Novellino E , Greco G , Marongiu ME , Pani A , De Montis A , La Colla P
Published: May 2015

In the presence of sodium hydride, reaction of aryldisulphides with ethyl esters of indole-2-carboxylic acids furnished ethyl 3-arylthioindole-2-carboxy-lates, which were cyclized intramolecularly to afford 5 H-indolo[3,2-b][1,5]benzothiazepin-6(7 H)-ones or hydrolysed in alkaline medium to give 3-arylthioindole-2-carboxylic acids. These acids, also obtained by the action of aryldisulphides on indole-2-carboxylic acids, afforded tetracyclic 5 H-indolo [3,2-b][1,5]benzothiazepin-6(7 H)-ones upon treatment with EDCI–DMAP. Transformation of cyclic sulphides into the required sulphones was achieved by treatment with hydrogen peroxide or with m-chloroperbenzoic acid. The title derivatives are conformationally constrained analogues of the potent human immunodeficiency virus type 1 (HIV-1) reverse transcriptase inhibitor 3-benzene-sulphonyl-5-chloroindole-2-carboxamide (L-737, 126). Although the indolobenzothiazepine derivatives, as well as the indolyl aryl sulphones used for their synthesis, were endowed with anti-HIV-1 activities in the submicromolar and micromolar range, none of them proved more potent than L-737,126.
In Vitro Evaluation and Characterization of Newly Designed Alkylamidophospholipid Analogues as Anti-Human Immunodeficiency Virus Type 1 Agents
Authors: Kucera LS , Iyer N , Morris-Natschke SL , Chen SY , Gumus F , Ishaq K , Herrmann DBJ
Published: May 2015

Our laboratories first reported two novel classes of complex synthetic lipids, including alkylamidophosphocholines (PC lipid; CP-51) and alkylamidophosphate ester-linked lipid–AZT conjugates (lipid–AZT conjugates; CP-92), with selective and potent activity against human immunodeficiency virus type 1 (HIV-1). To extend these observations, we synthesized additional PC lipids and lipid–AZT conjugates (INK and INK–AZT conjugate) to evaluate their structure–activity relationships by testing for selectivity against infectious wild-type (wt) and drug-resistant HIV-1 replication, virus fusogenic activity and toxicity for mouse bone marrow cells. PC lipid compounds with medium chain lengths at positions 1 and 2 gave an improved selective index (SI). INK-3, with 12 and 8 carbons and INK-15, with 10 and 12 carbons were among the most selective when evaluated in CEM-SS cells. INK-14, a lipid–AZT conjugate where AZT replaced the choline in PC lipid INK-3, gave the highest SI of >1250 against both infectious wt HIV-1 replication in CEM-SS cells and a clinical isolate in peripheral blood leukocytes. Notably, the PC lipid compounds INK-3 and INK-15, but not the lipid–AZT conjugate INK-14, were potent inhibitors of matched pairs of AZT-sensitive and AZT-resistant HIV-1 clinical isolates. INK-3 also inhibited replication of HIV-2 and TIBO-resistant HIV-1, and inhibited HIV-1-mediated fusogenic activity by 78, 41 and 9% in a dose-dependent manner. The TC50 for mouse bone marrow cells was >100 μg/ml for INK-3 compared to 9.15–14.17 μg/ml for CP-51 and 0.142–0.259 μg/ml for AZT. These data suggest that optimum PC lipid compounds are significantly less toxic than AZT and have high potential as novel therapeutic agents for AIDS.
Colorimetric Assays for Evaluation of the Mode of Action of Human Immunodeficiency Virus Type 1 Non-Nucleoside Reverse Transcriptase Inhibitors
Authors: Shao X , Rytting A-S , Ekstrand DHL , Vrang L , Källander CFR , Gronowitz JS
Published: May 2015

Four non-nucleoside reverse transcriptase (RT) inhibitors, 9-Cl-TIBO [(+)-S-4,5,6,7-tetrahydro-9-chloro-5-methyl-6-(3-methyl-2-butenyl)imidazo(4, 5,1- jk)(1,4)-benzodiazepin-2(1 H)-thione)], nevirapine (6,11-dihydro-11-cyclopropyl-4-methyl-dipyrido[2,3- b:2′,3′- e]-[1,4]diazepin-6-one), MSA-300 (N-[ cis-2-(2–hydroxy-3-acetyl-6-methoxy-phenyl)-cyclopropyl]-N'-(5-chloropyrid-2-yl)-thiourea) and delavirdine {1-(5-methanesulphonamido-1 H-indol-2-yl-carbonyl)-4-[3-(1-methylethylamino)pyridinyl] piperazine} were analysed for the mode of action of their inhibition of human immunodeficiency virus type 1 (HIV-1) RT in three different assays utilizing a 96-well microtitre plate format, with solid-phase conjugated poly(rA) as template. These were: (i) direct RT assay, for determination of IC50 values of RT inhibitors; (ii) RT template/primer binding inhibition (BIC) assay, for measuring the effect of various substances on the RT activity binding to template/primer; (iii) RT protein ELISA, for measuring RT protein binding to template/primer with a monoclonal antibodyreactive against a peptide in the RNase H region. MSA-300 and delavirdine gave the lowest IC50 values, ranging from 0.17 μM to 0.24 μM for MSA-300 and from 0.12 μM to 0.38 μM for delavirdine, whereas higher IC50 values of approximately 20 μM were obtained for 9-Cl-TIBO at all primer concentrations. None of the non-nucleoside substances had inhibiting effects on the binding of template, primer, or template/primer to RT protein. Their inhibition of RT activity was not due to prevention of RT binding to template/primer. TIBO, nevirapine and delavirdine bound to RT reversibly, and they bound more tightly to RT template/primer ternary than to RT template binary complex. MSA-300 showed a comparatively high affinity for the enzyme. The utility of the three assays in relation to screening and analysis of RT inhibitory substances is discussed.
3-Hydroxyphthaloyl β-Lactoglobulin. III. Antiviral Activity against Herpesviruses
Authors: Neurath AR , Strick N , Li Y-Y
Published: May 2015

The spread of sexually transmitted diseases, including human immunodeficiency virus type 1 (HIV-1) and herpesvirus infections, has continued unabated despite educational efforts spearheaded as a response to the HIV-1 epidemic. This suggests the need for prophylactic measures, including the application of topical antiviral agents. Chemical modification of bovine β-lactoglobulin (β-LG), the major protein of whey, by hydroxyphthalic anhydride (3HP) led to the generation of a potent HIV-1 inhibitor (designated 3HP-β-LG) shown to also have activity against herpes simplex virus types 1 and 2 (HSV-1, HSV-2). This report provides more detailed results concerning the anti-herpesvirus activity of 3HP-β-LG, indicating that this compound: (i) inhibited infection by human cytomegalovirus (HCMV), which is known to besexually transmitted; (ii) inactivated the infectivity of both HSV-1 and HSV-2; (iii) inhibited cell-to-cell transmission of HSV-1 and HSV-2; and (iv) bound to HSV-1, HSV-2 and HCMV virus particles and partially inhibited the binding of anti-glycoprotein E (gE) and anti-gC monoclonal antibodies to HSV-1 and HSV-2. The binding of 3HP-β-LG to the herpesviruses under study was inhibited by aggregated human IgG, suggesting that the respective viral Fc receptor is one of the target sites for 3HP-β-LG. In agreement with results on inhibition of HIV-1 infection, 3HP-β-LG appears to be the acid anhydride-modified protein of choice as an antiviral agent against herpesviruses.
Inhibition of Human Cytomegalovirus Proteinase by Salcomine Derivatives
Authors: Watanabe S , Konno K , Shigeta S , Yokota T
Published: May 2015

Salcomine, N,N'-bis(salicylidene)ethylene diaminocobalt (II), and its derivatives were evaluated for their ability to inhibit selectively human cytomegalovirus (HCMV) proteinase activity. The 50% inhibitory concentration (IC50) of salcomine was 1.4 μM for HCMV proteinase, but >200 μM for three other serine proteinases (trypsin, >250 μM; chymotrypsin, 206 μM; and elastase, >250 μM). Two salcomine derivatives also inhibited HCMV proteinase with IC50 values under 2 μM. Studies of the structure–activity relationship of salcomine-related compounds showed that the phenyl moiety and the spacer moiety (distance betweenthe two amines) were instrumental in the inhibition of HCMV proteinase. Moreover, salcomine inhibited the growth of laboratory strain AD169 and three clinical isolates at a 50% effective concentration (EC50) range of 1.92–2.89 μM. These results show that salcomine derivatives are potent and selective inhibitors of HCMV proteinase and HCMV replication in cell culture. Salcomine derivatives appear to be worth pursuing as candidate drugs for the chemotherapy of HCMV infection.
Potent and Selective Inhibitors of Human Immunodeficiency Virus Protease Structurally Related to L-694,746
Authors: Franchetti P , Perlini P , Sheikha G Abu , Cappellacci L , Grifantini M , Loi AG , De Montis A , Pani A , Marongiu ME , La Colla P
Published: May 2015

A series of human immunodeficiency virus (HIV) protease inhibitors, which are analogues of N-[2( R)-hydroxy-1( S)-indanyl]-5( S)-[( tert-butyloxycarbonyl)amino]-4( S)-hydroxy-6-phenyl-2-( R)-[[4-(carboxymethoxy)phenyl]methyl]hexanamide (L-694,746), a metabolite of the anti-HIV agent L-689,502, were synthesized. In these compounds, the acetic group linked to the para position of the P1′ phenyl in the reference inhibitor was replaced either by the bioisosteric phosphonomethoxy group and its diisopropyl/dibenzyl derivatives, or the 1H-tetrazol-5-yl-methoxy group and its 1-benzyl derivative. In enzyme assays, phosphonomethoxy and tetrazolmethoxy analogues proved to be potent inhibitors of the HIV-1 protease, with IC50 values as low as 0.04 nM. When tested for anti-HIV-1 activity in cell-based assays, most of the new derivatives proved active, with benzyl derivatives being more active than their highly polar, unsubstituted counterparts. The dibenzylphosphonomethoxy analogue was the most active compound, with an EC50 value of 10 nM and a selectivity index of 20 000. When compounds were examined for their capability to reduce p24 levels in both acutely and chronically infected MT-4 and H9/IIIB cells, all of them were found to be active at concentrations close to those capable of preventing HIV-1-induced cytopathic effect.
Synthesis, in Vitro Anti-Human Immunodeficiency Virus Structure—Activity Relationships and Biological Stability of 5′-O-Myristoyl Analogue Derivatives of 3′-Azido-2′,3′-Dideoxythymidine (AZT) as Potential Prodrugs
Authors: Parang K , Wiebe LI , Knaus EE
Published: May 2015

5′- O-Myristoyl analogue derivatives of 3′-azido-2′,3′-dideoxythymidine (AZT), designed as potential double-barrelled prodrugs to AZT and the myristic acid analogues, were synthesized. Their ability to protect CEM cells against human immunodeficiency virus (HIV)-induced cytopathogenicity was determined and structure–activity paradigms were developed. 3′-Azido-2′,3′-dideoxy-5′- O-(4-oxate-tradecanoyl)thymidine (EC50=1.4 nM) and 3′-azido-2′,3′-deoxy-5′- O-(12-bromododecanoyl)thymidine (EC50=3.2 nM) were the most effective anti-HIV-1 agents, relative to AZT (EC50=10 nM). These myristoyl analogue derivatives were more lipophilic (calculated log P=4.5–8.1 range) than the parent compound AZT (log P=0.06), and a linear correlation between their log P and HPLC log retention timeswas observed. The ester cleavage half-lives ( t1/2) for esters upon in vitro incubation with porcine liver esterase, rat plasma or rat brain homogenate was dependent on the steric bulk, and electronegative inductive effect of the α-substituent (H, Br, F), of the 5′- O-myristoyl analogue moiety. 3′-Azido-2′,3′-dideoxy-5′- O-(11-(4-iodophenoxy) undecanoyl)-thymidine exhibited t1/2 values of 80.4, 3.7 and 150.0 min upon incubation with porcine liver esterase, rat plasma and rat brain homogenate, respectively.
(Z)- and (E)-2-(Hydroxymethylcyclopropylidene)-Methylpurines and Pyrimidines as Antiviral Agents
Authors: Qiu Y-L , Ptak RG , Breitenbach JM , Lin J-S , Cheng Y-C , Kern ER , Drach JC , Zemlicka J
Published: May 2015

Several Z- and E-methylenecyclopropane nucleoside analogues were synthesized and evaluated for antiviral activity. Reaction of the Z- and E-2-amino-6-chloropurine methylenecyclopropanes with ammonia or cyclopropylamine gave 2,6-diamino or 2-amino-6-cyclopropylamino analogues. Alkylation elimination of N4-acetylcytosine with ethyl Z- and E-2-bromo-2-bromomethylcyclopropane-1-carboxylates gave a mixture of the Z-and E-methylenecyclopropane derivatives of cytosine. Reduction furnished a mixture of syncytol and the E isomer. Benzoylation led to the respective N4-benzoyl derivatives which were separated by chromatography. Debenzoylation afforded pure syncytol and the E isomer. Alkylation of 2,4-bis-O-trimethylsilylthymine with ethyl Z- and E-2-bromo-2-bromomethylcyclopropane-1-carboxylates gave the corresponding Z- and E-1-bromo-cyclopropylmethylderivatives of thymine. Base-catalysed elimination of HBr gave Z- and E-methylenecyclopropane carboxylic esters. Reduction furnished, after chromatographic separation, synthymol and the E isomer. The Z/E isomeric assignment of the obtained products followed from 1H NMR spectroscopy. The methylenecyclopropane analogues were tested for antiviral activity in vitro against human and murine cytomegalovirus (HCMV, MCMV), Epstein–Barr virus (EBV), varicella zoster virus (VZV), hepatitis B virus (HBV), herpes simplex virus types 1 and 2 (HSV-1, HSV-2), human herpesvirus 6 (HHV-6) and human immunodeficiency virus type 1 (HIV-1). The Z-2-amino-6-cyclopropylaminopurine analogue was the most effective agent against HCMV (EC50 or EC90 0.4–2 μM) followed by syncytol and the Z-2,6-diaminopurine analogues (EC50 or EC90 3.4–29 and 11–24 μM, respectively). The latter compound was also a strong inhibitor of MCMV (EC50 0.6 μM). Syncytol was the most potent against EBV (EC50 <0.41 and 2.5 μM) followed by the Z-2,6-diaminopurine (EC50 1.5 and 6.9 μM) and the Z-2-amino-6-cyclopropylaminopurine derivative (EC50 11.8 μM). Syncytol was also most effective against VZV (EC50 3.6 μM). Activity against HSV-1, HSV-2 and HHV-6 was generally lower; synthymol had an EC50 of 2 μM against HSV-1 (ELISA) and 1.3 μM against EBV in Daudi cells but was inactive in other assays. The 2-amino-6-cyclopropylamino analogue displayed EC50 values between 215 and >74 μM in HSV-1 and HSV-2 assays. 2-Amino-6-cyclopropylaminopurine and 2,6-diaminopurine derivatives were effective against HBV (EC50 2 and 10 μM, respectively), whereas none of the analogues inhibited HIV-1 at a higher virus load. Syncytol and the E isomer were equipotent against EBV in Daudi cells but the E isomer was much less effective in DNA hybridization assays. The E-2,6-diaminopurine analogue and E isomer of synthymol were devoid of antiviral activity.
Chemistry and Anti-Herpes Simplex virus Type 1 Evaluation of CycloSal-Nucleotides of Acyclic Nucleoside Analogues
Authors: Meier C , Habel L , Haller-Meier F , Lomp A , Herderich M , Klöcking R , Meerbach A , Wutzler P
Published: May 2015

The synthesis of different cycloSal-phosphotriesters of the acyclic nucleoside analogues acyclovir (ACV), penciclovir (PCV) and T-penciclovir (T-PCV) as potential new lipophilic, membrane-soluble pronucleotides is described. The introduction of the cycloSal moiety was achieved by using reactive cyclic chlorophosphane reagents. In addition to the cycloSal-PCV monophosphate (MP) phosphotri-esters, a second derivative bearing an acetyl group at the second primary alcohol function was prepared. In hydrolysis studies the cycloSal-ACVMPs showed the expected range of hydrolytic stability dependent on the substituent in the masking group (8–17 h). In contrast, the cycloSal-PCVMP derivatives exhibited a 11- to 15-fold increase in hydrolytic lability as compared to the corresponding cycloSal-ACVMP derivatives. We demonstrated that the free primary alcohol group is responsible for this rate acceleration because cycloSal-OAc-PCVMP, in which the hydroxyl group was blocked by acetylation, did not show the aforementioned acceleration. Unexpectedly, the hydrolysis product was not PCVMP but according to NMR and mass spectrometry it was cycloPCVMP (cPCVMP). The title compounds were evaluated in vitro for their ability to inhibit herpes simplex virus type 1 (HSV-1) and thymidine kinase-negative (TK–) HSV-1 replication in Vero cells. The cycloSal-ACVMP compounds exhibited high antiviral activity in HSV-1-infected cells. More importantly, one derivative retained all activity from the wild-type virus strain in HSV-1/TK–-infected Vero cells. The PCV derivatives were markedly less active. The reason for the failure of the cycloSal-PCVMPs seems to be due to the formation of cPCVMP instead of the desired PCVMP.
An Approach towards the Synthesis of Potential Metal-Chelating TSAO-T Derivatives as Bidentate Inhibitors of Human Immunodeficiency virus Type 1 Reverse Transcriptase
Authors: Chamorro C , Camarasa M-J , Pérez-Pérez M-J , de Clercq E , Balzarini J , Félix A San
Published: May 2015

Novel derivatives of the potent human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) inhibitor TSAO-T have been designed, synthesized and tested for their in vitro antiretro-viral activity against HIV. These TSAO-T derivatives have been designed as potential bidentate inhibitors of HIV-1 RT, which combine in their structure the functionality of a non-nucleoside RT inhibitor (TSAO-T) and a bivalent ion-chelating moiety (a β-diketone moiety) linked through an appropriate spacer to the N-3 of thymine of TSAO-T . Some of the new compounds have an anti-HIV-1 activity comparable to that of the parent compound TSAO-T, but display a markedly increased antiviral selectivity. There was a clear relationship between antiviral activity and the length of the spacer group that links the TSAO molecule with the chelating moiety. A shorter spacer invariably resulted in increased antiviral potency. None of the TSAO-T derivatives were endowed with anti-HIV-2 activity.
Synthesis, Structure and in Vitro Anti-Human Immunodeficiency virus Activity of Novel 3-Methyl-1H,3H-Thiazolo[3,4-a]Benzimidazoles
Authors: Chimirri A , Grasso S , Monforte AM , Monforte P , Rao A , Zappalà M , Bruno G , Nicolò F , Pannecouque C , Witvrouw M , De Clercq E
Published: May 2015

A series of novel 1-aryl-3-methyl-1 H,3 H-thiazolo[3,4- a]benzimidazoles, TBZ analogues, were synthesized and investigated as anti-human immunodeficiency virus (HIV) agents in order to study the effects of structural modifications on antiviral activity and cytotoxicity. They were proved to inhibit significantly HIV-1 replication in vitro without showing inhibitory activity on HIV-2 or simian immunodeficiency virus. Their potency was influenced by the presence of suitable substituents in the phenyl ring at C-1 as well as by their stereochemical characteristics. In fact, the most active compound of the series was the trans-1-(2,6-difluorophenyl)-3-methyl-1 H,3 H-thiazolo[3,4- a]benzimidazole, in which the butterfly-like conformation is stabilized by two intramolecular hydrogen bonds between the fluorine atoms and H-1 and H-3. This was made possible by the trans arrangement of C-1 and C-3 substituents, as shown by X-ray and NMR analysis.