Discovery of 2,3-diaryl-1,3-thiazolidin-4-ones as potent anti-HIV-1 agents

Design, synthesis and anti-HIV activity of a series of 2,3-diaryl-1,3-thiazolidin-4-ones are reported. Some derivatives proved to be highly effective in inhibiting HIV-1 replication at nanomolar concentrations thereby acting as non-nucleoside HIV-1 RT inhibitors (NNRTIs). SAR studies evidenced that the nature of the substituents at the 2 and 3 positions of the thiazolidinone nucleus largely influenced the in vitro anti-HIV activity of this new class of potent antiviral agents.

Chicoric acid analogues as HIV-1 integrase inhibitors

The present study was undertaken to examine structural features of L-chicoric acid (3) which are important for potency against purified HIV-1 integrase and for reported cytoprotective effects in cell-based systems. Through a progressive series of analogues, it was shown that enantiomeric D-chicoric acid (4) retains inhibitory potency against purified integrase equal to its L-counterpart and further that removal of either one or both carboxylic functionalities results in essentially no loss of inhibitory potency. Additionally, while two caffeoyl moieties are required, attachment of caffeoyl groups to the central linking structure can be achieved via amide or mixed amide/ester linkages. More remarkable is the finding that blockage of the catechol functionality through conversion to tetraacetate esters results in almost no loss of potency, contingent on the presence of at least one carboxyl group on the central linker. Taken as a whole, the work has resulted in the identification of new integrase inhibitors which may be regarded as bis-caffeoyl derivatives of glycidic acid and amino acids such as serine and beta-aminoalanine. The present study also examined the reported ability of chicoric acid to exert cytoprotective effects in HIV-infected cells. It was demonstrated in target and cell-based assays that the chicoric acids do not significantly inhibit other targets associated with HIV-1 replication, including reverse transcription, protease function, NCp7 zinc finger function, or replication of virus from latently infected cells. In CEM cells, for both the parent chicoric acid and selected analogues, antiviral activity was observable under specific assay conditions and with high dependence on the multiplicity of viral infection. However, against HIV-1- and HIV-2-infected MT-4 cells, the chicoric acids and their tetraacetylated esters exhibited antiviral activity (50% effective concentration (EC50) ranging from 1.7 to 20 microM and 50% inhibitory concentration (IC50) ranging from 40 to 60 microM).

Human immunodeficiency virus glycoprotein gp120 as the primary target for the antiviral action of AR177 (Zintevir)

The human immunodeficiency virus (HIV) inhibitor AR177 (T30177, Zintevir) has been identified as a potent inhibitor of HIV integrase in vitro. The compound is currently the subject of clinical phase I/II trials. However, the primary target for the mechanism of action in vivo has not been identified unequivocally. We have found that AR177 inhibits syncytium formation between MOLT-4 cells and HUT-78 cells persistently infected with the HIV-1IIIB or NL4-3 strain, at a 50% effective concentration of 3 microg/ml, roughly 3-fold higher than the concentration required to inhibit HIV replication. Furthermore, flow cytometric analysis has shown that AR177 at 25 microg/ml interferes with the binding of the monoclonal antibody 9284 (directed to the V3 loop of gp120) on HIVIIIB-infected HUT-78 cells, pointing to inhibition of virus binding or virus fusion as the mechanism of action of AR177. To precisely characterize the site/target of intervention by AR177, we have selected HIV-1 (NL4-3) strains resistant to AR177. The binding of the AR177-resistant strain, unlike the parental HIV-1 NL4-3 strain, could not be inhibited by AR177. The resistant phenotype was associated with the emergence of mutations in the gp120 molecule. DNA sequence analysis revealed the presence of the K148E, Q278H, K290Q, and F391I mutations and a deletion of 5 amino acids (FNSTW) at positions 364-368 in the V4 region of the resistant strain but not of the wild-type HIV strain. Selection of resistant strains, although it takes a relatively long time to develop, may also select for strains with lower replicative capacity. No mutations were found in the integrase enzyme gene. Our data argue against HIV integrase being the primary target for the mechanism of anti-HIV action of AR177.

5-(5-Bromothien-2-yl)-2'-deoxyuridine and 5-(5-chlorothien-2-yl)-2'-deoxyuridine are equipotent to (E)-5-(2-bromovinyl)-2'-deoxyuridine in the inhibition of herpes simplex virus type I replication

2'-Deoxyuridines with a five-membered heterocyclic substituent in the 5-position were synthesized by palladium-catalyzed coupling reactions of 5-iodo-2'-deoxyuridine with the activated heteroaromatics. Further modification of the compound with the 5-thien-2-yl substituent gave 5-(5-bromothien-2-yl)-2'-deoxyuridine and 5-(5-chlorothienyl-2-yl)-2'-deoxyuridine. Both compounds show potent and selective activity against herpes simplex virus type 1 and varicella-zoster virus.

Synthesis and anti-HIV activity of new modified 1,2,3-triazole acyclonucleosides

The synthesis of 1,2,3-triazole acyclonucleosides 7a-h via 1,3-dipolar cycloaddition of N-9/N-1-propargylpurine/pyrimidine 2a-h with azido-pseudo-sugar 4 is described and none of them had anti-HIV activity.

Viral entry as the primary target for the anti-HIV activity of chicoric acid and its tetra-acetyl esters

The antiviral activity of L-chicoric acid against HIV-1 has been attributed previously to the inhibition of HIV-1 integration. This conclusion was based on the inhibition of integrase activity in enzymatic assays and the isolation of a resistant HIV strain with a mutation (G140S) in the integrase gene. Here we show that the primary antiviral target of L-CA and its analogs in cell culture is viral entry. L- and D-chicoric acid (L-CA and D-CA) and their respective tetra-acetyl esters inhibit the replication of HIV-1 (III(B) and NL4.3) and HIV-2 (ROD) in MT-4 cells at a 50% effective concentration (EC(50)) ranging from 1.7 to 70.6 microM. In a time-of-addition experiment, L-CA, D-CA, L-CATA, and D-CATA were found to interfere with an early event in the viral replication cycle. Moreover, L-CA, D-CA, and their analogs did not inhibit the replication of virus strains that were resistant toward polyanionic and polycationic compounds at subtoxic concentrations. Furthermore, HIV-1 strains resistant to L-CA and D-CA were selected in the presence of L-CA and D-CA, respectively. Mutations were found in the V2, V3, and V4 loop region of the envelope glycoprotein gp120 of the L-CA and D-CA-resistant NL4.3 strains that were not present in the wild-type NL4.3 strain. Recombination of the gp120 gene of the L-CA and D-CA resistant strain in a NL4.3 wild-type molecular clone fully rescued the phenotypic resistance toward L-CA and D-CA. No significant mutations were detected in the integrase gene of the drug-resistant virus strains. Although inhibition of HIV integrase activity by L-CA and its derivatives was confirmed in an oligonucleotide-driven assay, integrase carrying the G140S mutation was inhibited to the same extent as the wild-type integrase.

Antiviral activity against human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) of ethnobotanically selected Ethiopian medicinal plants

Ethiopian medicinal plants used for the treatment of a variety of ailments including infectious diseases were screened for activity against human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2). Seventy-one polar and nonpolar extracts derived from 21 plants belonging to 14 families were tested for inhibition of viral replication using HIV-1 (III(B)) and HIV-2 (ROD) strains. Selective inhibition of viral growth was assessed by the simultaneous determination of the in vitro cytotoxicity of each of the extracts against MT-4 cells. Six extracts made from the root bark of Bersama abyssinica Fresen, the leaves of Combretum paniculatum Vent., and Dodonaea angustifolia L.f., and the stem bark of Ximenia americana L. displayed antiviral activity at concentrations that were nontoxic to MT-4 cells. The highest selective inhibition of HIV-1 replication was observed with the acetone fraction of C. paniculatum and the methanol fraction of D. angustifolia which showed selectivity indices (ratio of 50% cytotoxic concentration to 50% effective antiviral concentration) of 6.4 and 4.9, and afforded cell protection of viral induced cytopathic effect of 100% and 99%, respectively, when compared with control samples. The greatest degree of antiviral activity against HIV-2 was achieved with the acetone extract of C. paniculatum (EC(50): 3 microg/mL), which also showed the highest selectivity index (32). The 50% cytotoxic concentration ranged from 0.5 microg/mL for the hexane extract of D. angustifolia L.f., the most cytotoxic of the extracts tested, to >250 microg/mL for some extracts such as the methanol fraction of Alcea rosea L., the least toxic tested. Only the polar extracts that were obtained by extraction with hydroalcohol, methanol or acetone exhibited inhibition of viral growth at subtoxic concentrations. The results obtained in this study enable the selection of extracts which show some specificity of action and support the further investigation of these extracts for their potential as new lead antiretroviral compounds.

Prevalence and characteristics of multinucleoside-resistant human immunodeficiency virus type 1 among European patients receiving combinations of nucleoside analogues

The prevalence and the genotypic and phenotypic characteristics of multinucleoside-resistant (MNR) human immunodeficiency virus type 1 (HIV-1) variants in Europe were investigated in a multicenter study that involved centers in nine European countries. Study samples (n = 363) collected between 1991 and 1997 from patients exposed to two or more nucleoside analogue reverse transcriptase inhibitors (NRTIs) and 274 control samples from patients exposed to no or one NRTI were screened for two marker mutations of multinucleoside resistance (the Q151M mutation and a mutation with a 2-amino-acid insertion at codon 69, T69S-XX). Q151M was identified in six of the study samples (1. 6%), and T69S-XX was identified in two of the study samples (0.5%; both of them T69S-SS), but both patterns were absent among control samples. Non-NRTI (NNRTI)-related changes were observed in viral strains from two patients, which displayed the Q151M resistance pattern, although the patients were NNRTI naive. The patients whose isolates displayed multinucleoside resistance had received treatment with zidovudine and either didanosine, zalcitabine, or stavudine. Both resistance patterns conferred broad cross-resistance to NRTIs in vitro and a poor response to treatment in vivo. MNR HIV-1 is found only among multinucleoside-experienced patients. Its prevalence is low in Europe, but it should be closely monitored since it seriously limits treatment options.

2-(2,6-Dihalophenyl)-3-(pyrimidin-2-yl)-1,3-thiazolidin-4-ones as non-nucleoside HIV-1 reverse transcriptase inhibitors

Several 1,3-thiazolidin-4-ones bearing a 2,6-dihalophenyl group at C-2 and a substituted pyrimidin-2-yl ring at the N-3 were synthesised and evaluated as anti-HIV agents. The results of the in vitro tests showed that some of them were highly effective inhibitors of human immunodeficiency virus type-1 (HIV-1) replication at 10-40 nM concentrations with minimal cytotoxicity. Structure-activity relationship studies revealed that the nature of the substituents at the 2 and 3 positions of the thiazolidinone nucleus had a significant impact on the in vitro anti-HIV activity of this class of potent antiretroviral agents. The compounds had significantly reduced activity against the characteristic NNRTI-resistant virus mutants (bearing the K103N and Y181C RT mutations), thereby acting as non-nucleoside HIV-1 reverse transcriptase (RT) inhibitors (NNRTIs).

Activity of non-nucleoside reverse transcriptase inhibitors against HIV-2 and SIV

BACKGROUND

After the initial discovery of 1-(2-hydroxyethoxymethyl)-6-(phenylthio)thymine (HEPT) and tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-one and thione (TIBO) derivatives, several other non-nucleoside reverse transcriptase (RT) inhibitors (NNRTI), including nevirapine (BI-RG-587), pyridinone derivatives (L-696,229 and L-697,661), delavirdine (U-90152), alpha-anilinophenylacetamides (alpha-APA) and various other classes of NNRTI have been described. The hallmark of NNRTI has been based on their ability to interact with a specific site ('pocket') of HIV-1 RT.

OBJECTIVE

To investigate whether, in addition to HIV-1, different strains of HIV-2 (ROD and EHO) and SIV (mac251, agm3 and mndGB1) are sensitive to a selection of NNRTI i.e. delavirdine, the HEPT derivative I-EBU (MKC-442), 8-chloro-TIBO (tivirapine), alpha-APA (loviride), nevirapine and the pyridinone derivative L-697,661.

METHODS AND RESULTS

The NNRTI tested inhibited the replication of the different strains of HIV-2 and SIV at micromolar concentrations. The inhibitory effects of the NNRTI on HIV-2-induced cytopathicity correlated well with their inhibitory effects on HIV-2 RT activity. Drug-resistant HIV-2 (EHO) variants containing the Ser102Leu and/or Glu219Asp mutations in their RT were selected after passaging the virus in MT-4 cells in the presence of increasing concentrations of delavirdine. The EHO virus mutants were at least 20-fold less susceptible to the antiviral effects of delavirdine. Some cross-resistance, depending on the mutant strain, was observed with the other NNRTI tested (i.e. MKC-442, tivirapine, loviride and pyridinone L-697,661).

CONCLUSIONS

Our data demonstrate that NNRTI are not exclusively specific for HIV-1 but are also inhibitory to different HIV-2 and SIV strains. These observations will have important implications for the development of new NNRTI with higher activity against both HIV-1 and HIV-2. Furthermore, in view of their anti-SIV activity, NNRTI could be evaluated further for their in vivo anti-retrovirus efficacy in non-human primate models.

Antiviral potential of a new generation of acyclic nucleoside phosphonates, the 6-[2-(phosphonomethoxy)alkoxy]-2,4-diaminopyrimidines

Three acyclic nucleoside phosphonates (ANPs) have been formally approved for clinical use in the treatment of 1) cytomegalovirus retinitis in AIDS patients (cidofovir, by the intravenous route), 2) chronic hepatitis B virus (HBV) infections (adefovir dipivoxil, by the oral route), and 3) human immunodeficiency virus (HIV) infections (tenofovir disoproxil fumarate, by the oral route). The activity spectrum of cidofovir {(S)- 1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine [(S)-HPMPC)]}, like that of (S)-HPMPA [(S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]adenine) and (S)-HPMPDAP [(S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]-2, 6-diaminopurine), encompasses a broad spectrum of DNA viruses, including polyoma-, papilloma-, adeno-, herpes-, and poxviruses. Adefovir {9-[2-(phosphonomethoxy)ethyl]adenine (PMEA)} and tenofovir [(R)-9-[2-(phosphonomethoxy) propyl]adenine [(R)-PMPA)]} are particularly active against retroviruses (ie., HIV) and hepadnaviruses (ie., HBV); additionally, PMEA also shows activity against herpes- and poxviruses. We have recently identified a new class of ANPs, namely 6-[2-(phosphonomethoxy)alkoxy]-2,4-diaminopyrimidines, named, in analogy with their alkylpurine counterparts, HPMPO-DAPy, PMEO-DAPy, and (R)-PMPO-DAPy. These compounds exhibit an antiviral activity spectrum and potency that is similar to that of (S)-HPMPDAP, PMEA, and (R)-PMPA, respectively. Thus, PMEO-DAPy and (R)-PMPO-DAPy, akin to PMEA and (R)-PMPA, proved particularly active against HIV- 1, HIV-2, and the murine retrovirus Moloney sarcoma virus (MSV). PMEO-DAPy and (R)-PMPO-DAPy also showed potent activity against both wild-type and lamivudine-resistant strains of HBV. HPMPO-DAPy was found to inhibit different poxviruses (ie., vaccinia, cowpox, and orf) at a similar potency as cidofovir. HPMPO-DAPy also proved active against adenoviruses. In vivo, HPMPO-DAPy proved equipotent to cidofovir in suppressing vaccinia virus infection (tail lesion formation) in immunocompetent mice and promoting healing of disseminated vaccinia lesions in athymic-nude mice. The 6-[2-(phosphonomethoxy)alkoxy]-2,4-diaminopyrimidines offer substantial potential for the treatment of a broad range of retro-, hepadna-, herpes-, adeno-, and poxvirus infections.

1H-13C nuclear magnetic resonance assignment and structural characterization of HIV-1 Tat protein

Tat is a viral protein essential for activation of the HIV genes and plays an important role in the HIV-induced immunodeficiency. We chemically synthesized a Tat protein (86 residues) with its six glycines C alpha labelled with 13C. This synthetic protein has the full Tat activity. Heteronuclear nuclear magnetic resonance (NMR) spectra and NOE back-calculation made possible the sequential assignment of the 86 spin systems. Consequently, 915 NMR restraints were identified and 272 of them turned out to be long range ([i-j] > 4), providing structural information on the whole Tat protein. The poor spectral dispersion of Tat NMR spectra does not allow an accurate structure to be determined as for other proteins studied by 2D NMR. Nevertheless, we were able to determine the folding for Tat protein at a 1-mM protein concentration in a 100 mM, pH 4.5 phosphate buffer. The two main Tat functional regions, the basic region and the cysteine-rich region, are well exposed to solvent while a part of the N-terminal region and the C-terminal region constitute the core of Tat Bru. The basic region adopts an extended structure while the cysteine-rich region is made up of two loops. Resolution of this structure was determinant to develop a drug design approach against Tat. The chemical synthesis of the drugs allowed the specific binding and the inhibition of Tat to be verified.

Synthesis and screening for anti-HIV activity of some N-Mannich bases of isatin derivatives

The effect of about 12 new compounds of Mannich bases of isatin against HIV-1 (IIIB) and HIV-2 (ROD) strains in MT 4 cells was studied. The screening method employed was MTT. In initial studies, one compound has shown maximum protection of 16% in subtoxic concentration.

Antiretrovirus activity of a novel class of acyclic pyrimidine nucleoside phosphonates

A novel class of acyclic nucleoside phosphonates has been discovered in which the base consists of a pyrimidine preferably containing an amino group at C-2 and C-4 and a 2-(phosphonomethoxy)ethoxy (PMEO) or a 2-(phosphonomethoxy)propoxy (PMPO) group at C-6. The 6-PMEO 2,4-diaminopyrimidine (compound 1) and 6-PMPO 2,4-diaminopyrimidine (compound 11) derivatives showed potent activity against human immunodeficiency virus (HIV) in the laboratory (i.e., CEM and MT-4 cells) and in primary (i.e., peripheral blood lymphocyte and monocyte/macrophage) cell cultures and pronounced activity against Moloney murine sarcoma virus in newborn NMRI mice. Their in vitro and in vivo antiretroviral activity was comparable to that of reference compounds 9-[(2-phosphonomethoxy)ethyl]adenine (adefovir) and (R)-9-[(2-phosphonomethoxy)-propyl]adenine (tenofovir), and the enantiospecificity of (R)- and (S)-PMPO pyrimidine derivatives as regards their antiretroviral activity was identical to that of the classical (R)- and (S)-9-(2-phosphonomethoxy)propyl purine derivatives. The prototype PMEO and PMPO pyrimidine analogues were relatively nontoxic in cell culture and did not markedly interfere with host cell macromolecular (i.e., DNA, RNA, or protein) synthesis. Compounds 1 and 11 should be considered attractive novel pyrimidine nucleotide phosphonate analogues to be further pursued for their potential as antiretroviral agents in the clinical setting.

Synthesis and anti-HIV activity of 1,1,3-trioxo-2H,4H-thieno[3,4-e][1,2,4]thiadiazines (TTDs): a new family of HIV-1 specific non-nucleoside reverse transcriptase inhibitors

The anti-HIV activity of a novel series of 1,1,3-trioxo-2H,4H-thieno[3,4-e][1,2,4]thiadiazines (TTDs) has been described. The compounds were synthesized via Curtius rearrangement of appropriate sulfamoylcarboxy azides which, in turn, were prepared from known starting materials. Several 4-substituted-2-benzyl-derivatives were found to selectively inhibit human immunodeficiency virus type 1 [HIV-1 (IIIB)] replication in MT-4 and CEM cells. These TTDs were also effective against other strains of HIV-1 (RF, HE, MN, NDK), including those that are resistant to AZT, but not against HIV-2 (ROD) or simian immunodeficiency virus [SIV(MAC251)] at subtoxic concentrations. Some of the test compounds exhibited antiviral activity against L100I RT mutant virus, but significantly lost antiviral activity against K103N, V106A, E138K, Y181C and Y188H RT mutant viruses. Compounds 6d, 6f and 6g were inhibitory to HIV-1 RT at concentrations that rank between 16.4 and 59.8 microM (nevirapine: IC50 = 4.5 microM against HIV-1 RT). Inhibition of HIV-1 RT by compound 6g was purely non-competitive with respect to the natural substrate (dGTP), which is in agreement with the nature of inhibition shown by other NNRTIs such as nevirapine and delarvidine. A structure-activity relationship was established for the anti-HIV activity of these heterocyclic compounds. TTDs represent a new chemical class of non-nucleoside HIV-1 reverse transcriptase inhibitors (NNRTIs).

Potent anti-HIV (type 1 and type 2) activity of polyoxometalates: structure-activity relationship and mechanism of action

A series of polyoxometalates have been synthesized and evaluated for their inhibitory effects on HIV-1(III(B)) and HIV-1(ROD) replication in MT-4 cells. All compounds showed activity against HIV-1 and HIV-2, but the antiviral potency of the heteropolytungstates varied considerably depending on their chemical structure. The antiviral activity of single, double, and triple Keggin-type of compounds against HIV-1(III(B)) replication was comparable (IC(50): 0.4-0.5 microgram/mL), whereas HIV-2(ROD) appeared to become less sensitive with the increasing number of Keggin structures per compound. The same trend was observed for single and double Dawson structures. Some of these compounds were examined for their inhibitory effect on the replication of HIV-1(RF) and SIV(MAC(251)) in MT-4 cells. Their anti-HIV-1(RF) and anti-SIV(MAC(251)) potencies were comparable to those for the HIV-1(III(B)) or HIV-2(ROD) strain, respectively. The polyoxometalates represent a class of polyanionic compounds, which block the binding of the envelope glycoprotein gp120 of HIV to CD4(+) cells. The compounds interfered with the binding of anti-CD4 mAb to the OKT4A/Leu3a epitope of the CD4 receptor, compound 24 being the most active in this regard, and inhibited the binding of anti-gp120 mAb to infected MT-4 cells. None of the polyoxometalates inhibited the binding of a specific CXCR4 mAb to SUP-T1 cells, suggesting that they do not interact with CXCR4, the main co-receptor for T-tropic HIV strains, and thus act as virus binding, and not as fusion, inhibitors.

Conversion of 2',3'-dideoxyadenosine (ddA) and 2',3'-didehydro-2',3'-dideoxyadenosine (d4A) to their corresponding aryloxyphosphoramidate derivatives markedly potentiates their activity against human immunodeficiency virus and hepatitis B virus

2',3'-Dideoxyadenosine (ddA), 2',3'-didehydro-2',3'-dideoxyadenosine (d4A) and their lipophilic 5'-monophosphate triester (aryloxyphosphoramidate) prodrugs were evaluated for their anti-retrovirus and anti-hepatitis B virus activity in various cell culture models. The aryloxyphosphoramidate derivatives of ddA (Cf 1093) and d4A (Cf 1001) showed markedly superior (100-1000-fold) efficacies than the parent drugs against human immunodeficiency virus type 1 (HIV-1), HIV-2, simian immunodeficiency virus (SIV), Moloney murine sarcoma virus (MSV) and human hepatitis B virus (HBV) replication regardless of the cell type in which the virus replication was studied (i.e., human T-lymphocyte CEM, MT-4, Molt/4 and C8166 cells, peripheral blood lymphocytes (PBL), monocyte/macrophages (M/M), murine embryo fibroblasts and human hepatocyte cells). Also the selectivity index (ratio of cytotoxic concentration/antivirally effective concentration) of both aryloxyphosphoramidate prodrugs was markedly increased. In particular the d4A prodrug Cf 1001 showed a selectivity index of 300-3000 as compared with 2-3 for the parental d4A in established laboratory cell lines. Also Cf 1001 had a selectivity index of 400-650 in HIV-1-infected PBL and M/M, respectively. Both Cf 1001 and Cf 1093 were equally efficient as 3TC (lamivudine) in inhibiting HBV replication in hepatocytes, and rank among the most potent HIV and HBV inhibitors reported so far in cell culture.

A new vinyl selenone-based domino approach to spirocyclopropyl oxindoles endowed with anti-HIV RT activity

Herein, we disclose a general and flexible access to spirocyclopropyl oxindoles by a domino Michael/intramolecular nucleophilic substitution pathway with variously substituted vinyl selenones and enolizable oxindoles in aqueous sodium hydroxide solution. The spirocyclopropyl oxindole being a privileged scaffold, some of the synthesized compounds were selected for biological evaluation. Compound showed selective anti-HIV-1 activity thanks to its ability to inhibit the reverse transcriptase.

Broad-spectrum antiviral activity and mechanism of antiviral action of the fluoroquinolone derivative K-12

The fluoroquinolone derivatives have been shown to inhibit human immunodeficiency virus (HIV) replication at the transcriptional level. We confirmed the anti-HIV activity of the most potent congener, 8-difluoromethoxy-1-ethyl-6-fluoro-1,4-dihydro-7-[4-(2- methoxyphenyl)-1-piperazinyl]-4-quinolone-3-carboxylic acid (K-12), in both acutely and chronically infected cells. K-12 was active against different strains of HIV-1 (including AZT- and ritonavir-resistant HIV-1 strains), HIV-2 and simian immunodeficiency virus, in MT-4, CEM, C8166 and peripheral blood mononuclear cells. In all of these antiviral assay systems, K-12 showed a similar activity (EC50 0.2-0.6 microM). K-12 inhibited Moloney murine sarcoma virus-induced transformation of C3H/3T3 cells with an EC50 of 6.9 microM. Also, K-12 proved inhibitory to herpesvirus saimiri, human cytomegalovirus, varicella-zoster virus and herpes simplex virus types 1 and 2 (in order of decreasing sensitivity), but was not inhibitory (at subtoxic concentrations) to human herpesvirus type 8 (as evaluated in BCBL-1 cells), vaccinia virus, Sindbis virus, vesicular stomatitis virus, respiratory syncytial virus, Coxsackie virus, Punta Toro virus, parainfluenza virus or reovirus. Time-of-addition experiments and quantitative transactivation bioassays indicated that K-12 inhibits the Tat-mediated transactivation process in HIV-infected cells.

Polyanion inhibitors of HIV and other viruses. 7. Polyanionic compounds and polyzwitterionic compounds derived from cyclodextrins as inhibitors of HIV transmission

New polyanionic compounds were obtained from radical addition of thiomalic acid and mercaptopropionic acid onto perallylated cyclodextrins (CDs) under UV irradiation with a catalytic amount of alpha,alpha'-azobis(isobutyronitrile). All these polyanions, bearing 18-48 carboxylate groups, inhibited human immunodeficiency virus type 1 (HIV-1) strain IIIB replication in MT-4 cells at a 50% inhibitory concentration (IC50) of 0.1-2.9 microM, while not being toxic to the host cells at concentrations up to 62 microM. These compounds were also active against a clinical HIV-1 isolate (HE) at >/=4-fold higher concentrations. Only some compounds showed activity against the two HIV-2 strains (ROD and EHO) but at higher concentrations than those required to inhibit HIV-1 (IIIB and HE) replication. In addition, these compounds were not active against the M-tropic HIV-1 strain BaL but were active against simian immunodeficiency virus [SIV (MAC251)]. These compounds were also inhibitory to the replication of human cytomegalovirus at an IC50 of 1-10 microM, but not herpes simplex virus (type 1 and type 2) or other (picorna-, toga-, reo-, orthomyxo-, paramyxo-, bunya-, rhabdo-, and poxvirus) viruses. Radical addition on perallylated CDs of a protected cysteine gave polyzwitterionic compounds. None of these last compounds proved inhibitory to the replication of HIV-1, HIV-2, or any of the other viruses tested.

Novel inhibitors of HIV-1 integration

Human immunodeficiency virus (HIV) is the etiological agent of the acquired immune deficiency syndrome (AIDS). The current strategy for the treatment of HIV infection is called Highly Active Antiretroviral Therapy (HAART) and is based on cocktails of drugs that are currently approved by the Food and Drug Administration. These drugs include compounds that target the viral entry step and the enzymes reverse transcriptase or protease. The introduction of HAART has dramatically changed the landscape of HIV disease. Death from AIDS-related diseases has been reduced significantly since HAART came into use. Nevertheless it is not clear how long clinical benefit will last taking into account the emergence of multiple drug-resistant viral strains. Addition of new anti-HIV drugs targeting other steps of the viral replication cycle may increase the potency of inhibition and delay resistance development. HIV integrase is an essential enzyme in the HIV life cycle and is an attractive target for new drug development. Despite years of intensive research, only two classes of compounds that inhibit integration have been identified until now, namely the diketo acids and the pyranodipyrimidines. In this review we will point to new potential antiviral targets related to retroviral integration that are amenable to drug development. We will describe the pitfalls of currently used integrase assays and propose new strategies and technologies for the discovery of HIV integration inhibitors. Furthermore, we will describe the two classes of integrase inhibitors and discuss their antiviral activity, molecular mechanism of anti-HIV action and the selection of HIV resistance against these drugs.

1,1,3-Trioxo-2H,4H-thieno[3,4-e][1,2,4]thiadiazine (TTD) derivatives: a new class of nonnucleoside human immunodeficiency virus type 1 (HIV-1) reverse transcriptase inhibitors with anti-HIV-1 activity

We report the development of a new group of nonnucleoside reverse transcriptase inhibitors (NNRTIs). One of the most active congeners of this series of 1,1,3-trioxo-2H,4H-thieno[3,4-e] [1,2,4]thiadiazine (TTD) derivatives, i.e., 2-(3-fluorobenzyl)-4-cyanomethylen-l,1,3-trioxo-2H,4H- thieno [3,4-e] [1,2,4] thiadiazine) (QM96639) was found to inhibit human immunodeficiency virus (HIV) type 1 [HIV-1 (IIIB)] replication in MT-4 cells at a concentration of 0.09 microM. This compound was toxic for the host cells only at a 1,400-fold higher concentration. The TTD derivatives proved effective against a variety of HIV-1 strains, including those that are resistant to 3'-azido-3'-deoxythymidine (AZT), but not against HIV-2 (ROD) or simian immunodeficiency virus (SIV/ MAC251). HIV-1 strains containing the L100I, K103N, V106A, E138K, Y181C, or Y188H mutations in their reverse transcriptase (RT) displayed reduced sensitivity to the compounds. Their cross-resistance patterns correlated with that of nevirapine. 2-Benzyl-4-cyanomethylen-1,1,3-trioxo-2H,4H-thieno[3,4-e] [1,2,4]thiadiazine (QM96521) enhanced the anti-HIV-1 activity of AZT and didanosine in a subsynergistic manner. HIV-1-resistant virus containing the V179D mutation in the RT was selected after approximately six passages of HIV-1 (IIIB) in CEM cells in the presence of different concentrations of QM96521. From structure-activity relationship analysis of a wide variety of TTD derivatives, a number of restrictions appeared as to the chemical modifications that were compatible with anti-HIV activity. Modelling studies suggest that in contrast to most other NNRTIs, but akin to nevirapine, QM96521 does not act as a hydrogen bond donor in the RT-drug complex.

Synthesis and biological activity of novel 1H,3H-thiazolo[3,4-a]benzimidazoles: non-nucleoside human immunodeficiency virus type 1 reverse transcriptase inhibitors

Using a known human immunodeficiency virus type 1 (HIV-1) non-nucleoside reverse transcriptase inhibitor (NNRTI), 1-(2,6-difluorophenyl)-1H,3H-thiazolo[3,4-a]benzimidazole (TBZ NSC 625487) as the lead structure for drug design, a series of novel 1H,3H-thiazolo[3,4-a]benzimidazole derivatives substituted on the benzene-fused ring was prepared. Their in vitro anti-HIV-1 activity, as well as their inhibitory effects on the viral reverse transcriptase, were evaluated. The structure-activity relationships for these compounds are described and the results suggest that the apolar binding pocket of RT, into which the NNRTIs must fit, can accommodate only groups with a limited size and shape.

Phase I/II dose escalation and randomized withdrawal study with add-on azodicarbonamide in patients failing on current antiretroviral therapy

BACKGROUND

Azodicarbonamide (ADA), a HIV-1 zinc finger inhibitor, targets a new step in viral replication and cell infectivity.

OBJECTIVE

A first phase I/II clinical study of ADA.

METHODS

ADA was administered at escalating doses concomitantly with current antiviral therapy during a 3-month open-label period in patients with advanced AIDS and documented virological failure. After 3 months, patients were randomized in a double-blind placebo-controlled withdrawal, ADA being given at the highest tolerated dosage.

RESULTS

Fifteen patients with advanced disease failing on combined antiretroviral therapy, 75% of them with proven phenotypic resistance, had a median baseline CD4 cell count of 85 x 10(6) cells/l, CD4/CD8 cell ratio of 0.09 and median plasma RNA viral load of 4.2 log10 copies/ml. Tolerance to ADA was dose dependent and some patients developed nephrolithiasis, glucose intolerance or showed an ADA-related cytotoxicity towards CD4 cells at higher dosages. No patient died during the study period. ADA increased CD4 cell percentage, increased the CD4/CD8 cell ratio and decreased plasma RNA viral load from baseline. At the end of the double-blind period, the ADA group, but not the placebo group, showed a significant response (P < 0.05). No phenotypic resistance to ADA was observed. Overall, 3/11 patients (27%) had consistent viral load reductions > 0.5 log10 copies/ml compared with baseline and 5/ 11 (45%) showed a CD4 cell recovery from baseline > 33%. In responders, ADA induced a median peak increase in CD4 cell percentage change from baseline of 65% (range 47-243%), and viral load decrease of 1.04 log10 copies/ml (range 0.52-1.23).

CONCLUSIONS

The maximal tolerated dosage of ADA appears to be 2 g (three times daily). This study provides safety results that will allow larger clinical trials to confirm the preliminary efficacy data.