Antiretroviral agents as inhibitors of both human immunodeficiency virus type 1 integrase and protease

New coumarin glycosides from the leaves of Diospyros crassiflora (Hiern)

Two new 5-methylcoumarin glycosides named diosfeboside A (1) and B (2) and five known compounds namely kaempferol 3-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-glucopyranoside (3), ursolic acid (4), betulinic acid (5), stigmasterol (6) and stigmasterol 3-O-β-D-glucopyranoside (7) were isolated from the leaves of Diospyros crassiflora (Hiern). Their structures were established through interpretation of 1 and 2D NMR, mass spectra analysis and comparison with reported data. In vitro cytotoxic activity of the new compounds against human carcinoma cell lines (HL-60, Bel-7402, BGC-823, and KB) was evaluated and no cytotoxicity was observed for each of them.

Stereochemistry of Products of Reactions between 3-diazo-naphthalene-1,2,4-trione and β-dicarbonyl Compounds. Structure of ethyl 2-[(3-hydroxy-1,4-dioxo-1,4-dihydro-naphthalen-2-yl)-hydrazono]-3-phenyl-3-oxo-propionate

3-Hydroxy-2-[(R1CO)(R2CO)]C=NNH-1,4-naphthoquinones, obtained from reactions of 3-diazonaphthalene-1,2,4-trione with β-diketones, R1C(O)CH2COR2, have been previously found to have high antibacterial activity. However, confirmation of the stereochemistry about the C=N bond could not be achieved by spectroscopic means for products having different R1and R2groups, thereby limiting the utility of the reaction. Full characterisation of the product isolated from reaction of 3-diazonaphthalene-1,2,4-trione with PhC(O)CH2CO2Et is now reported, from a single crystal X-ray structure determination: the product, 3-hydroxy-2-[(PhCO)(EtCO2)]C=NNH-1,4-naphthoquinone has a ( Z)-stereochemistry. The Z-isomer is obtained rather than the E form due to the preferred formation of the stronger intramolecular N–H—O hydrogen-bond with the ester carbonyl oxygen rather than a weaker one with the ketone oxygen. Weaker C–H—O hydrogen bonds link the molecules into columns. It is suggested that similar Z geometries will arise from other RC(O)CH2CO2Rireactants.

The synthesis and antimicrobial activity of some 4-hydroxycoumarin derivatives

Due to exceptional reactivity of 4-hydroxycoumarin, the synthesis of new coumarin derivatives of dimer and tetramer type has been carried out. The synthesis was carried out from 4-hydroxycoumarin and various aromatic aldehydes. In this way, compounds of the dimer 3,3'-(benzilidene)bis (4-hydroxycoumarin) type, as well as of the tetramer 3,3',3'',3'''-(1,4-dimethylenphenyl)tetra (4-hydroxycoumarin) type were prepared. The newly synthesized derivatives contain different functional groups, and as such they could exhibit microbiological activity. Therefore, we tested the microbiological activity of these derivatives on various species of bacteria and fungi. The tested compounds have shown different activity in terms of growth inhibition of microorganisms. Newly synthesized derivatives exhibit antibacterial activities, manifested as growth inhibition on Gram-positive bacteria types (Bacillus, Staphylococcus), while the activity against Candida was much weaker. The same compound did not show any antimicrobial activity against two Gram-negative bacteria types (Escherichia coli, Pseudomonas aeruginosa). The compound 1 showed the best microbiological activity. The obtained results confirmed its good antibacterial and antimycotic activities against different microorganisms.

Recent advances in the investigation of curcuminoids

More than 30 Curcuma species (Zingiberaceae) are found in Asia, where the rhizomes of these plants are used as both food and medicine, such as in traditional Chinese medicine. The plants are usually aromatic and carminative, and are used to treat indigestion, hepatitis, jaundice, diabetes, atherosclerosis and bacterial infections. Among the Curcuma species, C. longa, C. aromatica and C. xanthorrhiza are popular. The main constituents of Curcuma species are curcuminoids and bisabolane-type sesquiterpenes. Curcumin is the most important constituent among natural curcuminoids found in these plants. Published research has described the biological effects and chemistry of curcumin. Curcumin derivatives have been evaluated for bioactivity and structure-activity relationships (SAR). In this article, we review the literature between 1976 and mid-2008 on the anti-inflammatory, anti-oxidant, anti-HIV, chemopreventive and anti-prostate cancer effects of curcuminoids. Recent studies on curcuminoids, particularly on curcumin, have discovered not only much on the therapeutic activities, but also on mechanisms of molecular biological action and major genomic effects.

HIV-1 integrase inhibitors: 2005-2006 update

HIV-1 integrase (IN) catalyzes the integration of proviral DNA into the host genome, an essential step for viral replication. Inhibition of IN catalytic activity provides an attractive strategy for antiretroviral drug design. Currently two IN inhibitors, MK-0518 and GS-9137, are in advanced stages of human clinical trials. The IN inhibitors in clinical evaluation demonstrate excellent antiretroviral efficacy alone or in combination regimens as compared to previously used clinical antiretroviral agents in naive and treatment-experienced HIV-1 infected patients. However, the emergence of viral strains resistant to clinically studied IN inhibitors and the dynamic nature of the HIV-1 genome demand a continued effort toward the discovery of novel inhibitors to keep a therapeutic advantage over the virus. Continued efforts in the field have resulted in the discovery of compounds from diverse chemical classes. In this review, we provide a comprehensive report of all IN inhibitors discovered in the years 2005 and 2006.

Synthesis and HIV-1 integrase inhibition of novel bis- or tetra-coumarin analogues

Present studies were undertaken on the preparation of synthetic analogues of bis- or tetra-coumarins and their activity against HIV-1 integrase (HIV-1 IN). Among these coumarin analogues, compounds 14, 16 and 18 were found to be potent molecules against HIV-1 IN at IC50 values of 0.96, 0.58, and 0.49 microM, respectively. The results provided a tool for guiding the further design of more potent antiviral agents and for predicting the affinity of related compounds.

Biologically active coumarins as inhibitors of HIV-1

Considerable progress has been made in recent years in the field of drug development against HIV. Many different kinds of natural products, including coumarins, have been found to be active in anti-HIV models and are thus undergoing further investigation. This review demonstrates the variety of coumarins with unique mechanisms of action in the different stages of HIV replication. The discovery and development of coumarins as anti-HIV agents has expanded in the past two decades. Most of the studies have been focused on the inhibitory activity of reverse transcriptase, but anti-integrase and antiprotease activities were also described. The objective of this review is to evaluate data on coumarins’ potent activity with respect to the inhibition of HIV-reverse transcriptase, HIV-integrase or HIV-protease. Recent requirements for potential anti-HIV agents increasingly require adequate definition of the mechanism of action as well as definition of toxic effects and this also applies to natural as well as synthetic coumarins. Structural modification is a powerful tool to increase the potential of bioactive principles. By applying scientific expertise and modern scientific technology, new single compounds will assuredly be developed as potent anti-HIV candidates for world-class new drug development.

Development of integrase inhibitors for treatment of AIDS: An overview

HIV-1 integrase (IN) is an essential enzyme for retroviral replication. It is involved in the integration of HIV DNA into host chromosomal DNA. The unique properties of IN makes it an ideal target for drug design. First, there appears to have no functional equivalent in human cells and the reactions catalyzed by IN are unique. Second, IN is absolutely required for viral replication and mutations in a number of key residues block the viral replication. Third, IN has been validated as a legitimate target and the results from the molecules like S-1,360, JKT-303 which are under phase II/III clinical trials suggest synergistic effect with reverse transcriptase (RT) and protease (PR) inhibitors. During the past 10 years a plethora of inhibitors have been identified and some were shown to be selective against IN and block viral replication. The classes under which inhibitors of integrase can be classified are catechol-containing hydroxylated aromatics, diketoacid-containing aromatics, quninolines and others (non-catechol containing). In the present article we review all the recent small molecules reported to inhibit recombinant HIV-1 IN under these heads. It seems likely that the efficient use of HIV IN as target for rational design can give potent anti-HIV agents, which can be used alone or in combination regimens with other classes of anti-HIV drugs.

CURCUMIN: THE INDIAN SOLID GOLD

Turmeric, derived from the plant Curcuma longa, is a gold-colored spice commonly used in the Indian subcontinent, not only for health care but also for the preservation of food and as a yellow dye for textiles. Curcumin, which gives the yellow color to turmeric, was first isolated almost two centuries ago, and its structure as diferuloylmethane was determined in 1910. Since the time of Ayurveda (1900 Bc) numerous therapeutic activities have been assigned to turmeric for a wide variety of diseases and conditions, including those of the skin, pulmonary, and gastrointestinal systems, aches, pains, wounds, sprains, and liver disorders. Extensive research within the last half century has proven that most of these activities, once associated with turmeric, are due to curcumin. Curcumin has been shown to exhibit antioxidant, anti-inflammatory, antiviral, antibacterial, antifungal, and anticancer activities and thus has a potential against various malignant diseases, diabetes, allergies, arthritis, Alzheimer's disease, and other chronic illnesses. These effects are mediated through the regulation of various transcription factors, growth factors, inflammatory cytokines, protein kinases, and other enzymes. Curcumin exhibits activities similar to recently discovered tumor necrosis factor blockers (e.g., HUMIRA, REMICADE, and ENBREL), a vascular endothelial cell growth factor blocker (e.g., AVASTIN), human epidermal growth factor receptor blockers (e.g., ERBITUX, ERLOTINIB, and GEFTINIB), and a HER2 blocker (e.g., HERCEPTIN). Considering the recent scientific bandwagon that multitargeted therapy is better than monotargeted therapy for most diseases, curcumin can be considered an ideal "Spice for Life".

A historical sketch of the discovery and development of HIV-1 integrase inhibitors

The long process of HIV-1 integrase inhibitor discovery and development can be attributed to both the complexity of HIV-1 integration and poor 'integration' of these researches into mainstream investigations on antiretroviral therapy in the mid-1990s. Of note, some fungal extracts investigated during this period contain the beta-hydroxyketo group, later recognised to be a key structural requirement for keto-enol acids (also referred to as diketo acids) and other integrase inhibitors. This review reconstructs (in the general context of the history of AIDS research) the principal steps that led to the integrase inhibitors currently in clinical trials, and discusses possible future directions.

Synthesis, structure, toxicological and pharmacological investigations of 4-hydroxycoumarin derivatives

Twenty 4-hydroxycoumarin derivatives were synthesized. Five of them are described for the first time. The X-ray crystal structure analysis of 3,3'-(2,3,4-trimethoxyphenylmethylene)bis-(4-hydroxy-2H-1-benzopyran-2-one) (7) and 3,3'-(3,5-dimethoxy-4-hydroxyphenylmethylene)bis-(4-hydroxy-2H-1-benzopyran-2-one) (9) confirmed the structure of these compounds. A comparative pharmacological study of the anticoagulant effect with respect to Warfarin showed that the synthesized compounds have different anticoagulant activities. The most prospective compound is 3,3'-(4-chlorophenylmethylene)bis-(4-hydroxy-2H-1-benzopyran-2-one) (12) with low toxicity, very good index of absorption and dose dependent anticoagulant activity.

Discovery of a small-molecule HIV-1 integrase inhibitor-binding site

Herein, we report the identification of a unique HIV-1 integrase (IN) inhibitor-binding site using photoaffinity labeling and mass spectrometric analysis. We chemically incorporated a photo-activatable benzophenone moiety into a series of coumarin-containing IN inhibitors. A representative of this series was covalently photo-crosslinked with the IN core domain and subjected to HPLC purification. Fractions were subsequently analyzed by using MALDI-MS and electrospray ionization (ESI)-MS to identify photo-crosslinked products. In this fashion, a single binding site for an inhibitor located within the tryptic peptide (128)AACWWAGIK(136) was identified. Site-directed mutagenesis followed by in vitro inhibition assays resulted in the identification of two specific amino acid residues, C130 and W132, in which substitutions resulted in a marked resistance to the IN inhibitors. Docking studies suggested a specific disruption in functional oligomeric IN complex formation. The combined approach of photo-affinity labeling/MS analysis with site-directed mutagenesis/molecular modeling is a powerful approach for elucidating inhibitor-binding sites of proteins at the atomic level. This approach is especially important for the study of proteins that are not amenable to traditional x-ray crystallography and NMR techniques. This type of structural information can help illuminate processes of inhibitor resistance and thereby facilitate the design of more potent second-generation inhibitors.

Antihuman Immunodeficiency Virus Type 1 (HIV-1) Activity of Rare Earth Metal Complexes of 4-Hydroxycoumarins in Cell Culture

The cerium Ce(III), lanthanum La(III), and neodymium Nd(III) complexes with 4-hydroxy-3-(3-oxo-1-phenylbutyl)-2H-1-benzopyran-2-one (warfarin) (W) and 3,3'-benzylidenebis[4-hydroxycoumarin] (1) were synthesized and studied for the first time for cytotoxicity (on MT-2 cells) and as anti-HIV agents under acute and chronic infection. The complexes were characterized by different physicochemical methods: mass spectrometry, (1)H NMR, (13)C NMR, and IR spectroscopy. The spectra of the complexes were interpreted on the basis of comparison with the spectrum of the free ligands. Anti-HIV effect of the complexes/ligands was measured in MT-2 cells by microtiter infection assay. Detection of endogenous reverse transcriptase (RT) activity and RT processivity by PCR indicative for proviral DNA synthesis demonstrated that anti-HIV activity has not been linked to early stages of viral replication. No effect on late steps of viral replication has been found using cells chronically producing HIV-1(LAI) virus. La(W) demonstrated anti-HIV activity (IC50=21.4 muM) close to maximal nontoxic concentration. Nd(W), Ce(1), and Nd(1) demonstrated limited anti-HIV potency, so none of the complexes seems appropriate to be used in clinic. Further targeting of HIV-1 inhibition by La(W) is under progress.

Model of full-length HIV-1 integrase complexed with viral DNA as template for anti-HIV drug design

We report structural models of the full-length integrase enzyme (IN) of the human immunodeficiency virus type 1 (HIV-1) and its complex with viral and human DNA. These were developed by means of molecular modeling techniques using all available experimental evidence, including X-ray crystallographic and NMR structures of portions of the full-length protein. Special emphasis was placed on obtaining a model of the enzyme's active site with the viral DNA apposed to it, based on the hypothesis that such a model would allow structure-based design of inhibitors that retain activity in vivo. This was because bound DNA might be present in vivo after 3'-processing but before strand transfer. These structural models were used to study the potential binding modes of various diketo-acid HIV-1 IN inhibitors (many of them preferentially inhibiting strand transfer) for which no experimentally derived complexed structures are available. The results indicate that the diketo-acid IN inhibitors probably chelate the metal ion in the catalytic site and also prevent the exposure of the 3'-processed end of the viral DNA to human DNA.

Integrase inhibitors to treat HIV/AIDS

HIV integrase is a rational target for treating HIV infection and preventing AIDS. It took approximately 12 years to develop clinically usable inhibitors of integrase, and Phase I clinical trials of integrase inhibitors have just begun. This review focuses on the molecular basis and rationale for developing integrase inhibitors. The main classes of lead compounds are also described, as well as the concept of interfacial inhibitors of protein-nucleic-acid interactions that might apply to the clinically used strand-transfer inhibitors.

Enantioselective Enol Lactone Synthesis under Double Catalytic Conditions

[reaction: see text] The reaction of dimedone with 1-(2-alkenoyl)-4-bromo-3,5-dimethylpyrazoles in THF, catalyzed by catalytic amounts of both DBFOX/Ph-nickel(II) perchlorate trihydrate and 2,2,6,6-tetramethylpiperidine, in the presence of acetic anhydride in THF produces the corresponding enol lactones in high enantioselectivities through enantioselective Michael additions followed by cyclization with removal of the pyrazole auxiliary. Other related nucleophile precursors can be successfully applied in the enantioselective enol lactone synthesis under the double catalytic conditions.

Use of 1,4-naphthoquinones for control ofErwinia carotovora

The antimicrobial effect of 5 naphthoquinones was tested against the phytopathogenic bacteria Erwinia carotovora. Disk diffusion tests and determination of minimal inhibitory concentrations (MIC) indicate that the compound naphthazarin (NTZ) has the best antibacterial activity among the naphthoquinones tested. Studies on the mode of action indicate the effect of NTZ was bactericidal at 10 µg/mL. When cultivation was done in the presence of sodium ascorbate, the restoration of E. carotovora growth was observed with 3 µg/mL NTZ, but not when a 10 µg/mL dose was used. The incubation of NTZ with bacterial suspension of E. carotovora resulted in important changes in the absorption spectra of this naphthoquinone, indicating that a redox reaction takes place. These results may suggest that NTZ induces an increase of reactive oxygen species that are toxic to the cell. The compound NTZ was also effective in preventing E. carotovora growth on potato tubers, inhibiting the soft rot development at a concentration of 2 mg/mL.Key words: antimicrobial, naphthazarin, phytopathogen, potato, 5,8-dihydroxy-1,4-naphthoquinone.

Chemoprotective effect of plant phenolics against anthracycline-induced toxicity on rat cardiomyocytes. Part II. caffeic, chlorogenic and rosmarinic acids

The chemoprotective effects of caffeic (CA), chlorogenic (CHA) and rosmarinic (RA) acids were tested against the toxicity of doxorubicin (DOX) in neonatal rat cardiomyocytes and the iron-dependent DOX induced lipid peroxidation of heart membranes, mitochondria and microsomes. The protectivity of these acids was compared with dexrazoxan, used as an adjuvant during DOX chemotherapy. The cytoprotective effects were assessed by enzyme (LDH and ASAT) and troponin I leakage, secondly by intracellular ATP content. All hydroxycinnamic acids proved non-cytotoxic, and they stabilized both membranes and the energetic status of cardiomyocytes. After preincubation of cardiomyocytes with the test compounds (100, 200 microm; 1 h) the cardiomyocytes were treated with the toxic agent, DOX (100 microm; 8 h). The test compounds protected cardiomyocytes against DOX induced oxidative stress (RA > CHA > or = CA) on all monitored parameters. Substantial preservation of monolayer integrity of the cardiomyocytes by test compounds was also found microscopically. All the acids were more effective in the assays used than dexrazoxan. RA showed the most effective cytoprotectivity. All the acids significantly reduced the iron-dependent DOX induced lipid peroxidation of heart membranes, although of the test compounds, CHA was found to be the most effective (IC(50) = 8.04 +/- 0.74/6.87 +/- 0.52 micro m for microsomes/mitochondria).

HIV-1 integrase pharmacophore model derived from diverse classes of inhibitors

A three-dimensional pharmacophore model has been generated for HIV-1 integrase (HIV-1 IN) from known inhibitors. A dataset consisting of 26 inhibitors was selected on the basis of the information content of the structures and activity data as required by the catalyst/HypoGen program. Our model was able to predict the activity of other known HIV-1 IN inhibitors not included in the model generation, and can be further used to identify structurally diverse compounds with desired biological activity by virtual screening.

Recent progress in the development of coumarin derivatives as potent anti-HIV agents

Numerous plant-derived compounds have been evaluated for inhibitory effects against HIV replication, and some coumarins have been found to inhibit different stages in the HIV replication cycle. This review article describes recent progress in the discovery, structure modification, and structure-activity relationship studies of potent anti-HIV coumarin derivatives. A dicamphanoyl-khellactone (DCK) analog, which was discovered and developed in our laboratory, and calanolide A are currently in preclinical studies and clinical trials, respectively.

Curcumin, the major component of food flavour turmeric, reduces mucosal injury in trinitrobenzene sulphonic acid-induced colitis

1 Inflammmatory bowel disease (IBD) is characterized by oxidative and nitrosative stress, leucocyte infiltration and upregulation of proinflammatory cytokines. In this study, we have investigated the protective effects of curcumin, an anti-inflammatory and antioxidant food derivative, on 2,4,6- trinitrobenzene sulphonic acid-induced colitis in mice, a model for IBD. 2 Intestinal lesions (judged by macroscopic and histological score) were associated with neutrophil infiltration (measured as increase in myeloperoxidase activity in the mucosa), increased serine protease activity (may be involved in the degradation of colonic tissue) and high levels of malondialdehyde (an indicator of lipid peroxidation). 3 Dose-response studies revealed that pretreatment of mice with curcumin (50 mg kg(-1) daily i.g. for 10 days) significantly ameliorated the appearance of diarrhoea and the disruption of colonic architecture. Higher doses (100 and 300 mg kg(-1)) had comparable effects. 4 In curcumin-pretreated mice, there was a significant reduction in the degree of both neutrophil infiltration (measured as decrease in myeloperoxidase activity) and lipid peroxidation (measured as decrease in malondialdehyde activity) in the inflamed colon as well as decreased serine protease activity. 5 Curcumin also reduced the levels of nitric oxide (NO) and O(2)(-) associated with the favourable expression of Th1 and Th2 cytokines and inducible NO synthase. Consistent with these observations, nuclear factor-kappaB activation in colonic mucosa was suppressed in the curcumin-treated mice. 6 These findings suggest that curcumin or diferuloylmethane, a major component of the food flavour turmeric, exerts beneficial effects in experimental colitis and may, therefore, be useful in the treatment of IBD.

Curcumin differentially modulates mRNA profiles in Jurkat T and human peripheral blood mononuclear cells

Curcumin, the yellow pigment of the rhizome of Curcuma longa is known to inhibit the transcription factors AP-1, Egr-1, NF-kappaB, c-myc and several important signaling kinases. We therefore investigated the differential effects of curcumin in concentation between 1.5 and 13.6 microM on gene expression in T Jurkat CD4(+) and human peripheral blood mononuclear cells (PBMCs). Relative quantification with reverse transcription real-time PCR (RT-rt-PCR) showed that low concentrations of curcumin significantly down-regulated mitogen-induced granulocyte macrophage colony stimulating factor (GM-CSF) mRNA (3- to 5-fold at 3 microM) in a dose- and time-dependent manner in both cell types. In comparison, the down-regulation of inducible nitric oxide (iNOS) mRNA levels was less pronounced, but interferon gamma (IFN-gamma) mRNA was dose-dependently up-regulated with curcumin concentrations up to 8.2 microM. Cyclin D1 mRNA expression was specifically inhibited in Jurkat T cells and stimulated PBMCs. The transcription factors NF-kappaB and NF-ATc were not affected in PBMCs. Interleukin-2 (IL-2), and-6 (IL-6) mRNAs levels were not influenced markedly by curcumin in stimulated PBMCs, but significantly reduced in stimulated Jurkat T cells. In addition, cytotoxic effects and down-regulation of mRNAs, including p65 and the house-keeping genes could only be measured in Jurkat T cells. These findings confirm previous reports on the anti-neoplastic potential of curcumin and show that this compound differentially modulates the expression profile of Th1 cells and PBMCs.

HIV-1 integrase inhibitory substances from Coleus parvifolius

For the purpose of discovering anti-HIV-1 agents from natural sources, water and EtOH extracts of 50 Thai plants were screened for their inhibitory activity against HIV-1 integrase (IN), an enzyme essential for viral replication. Of these plants, an EtOH extract of Coleus parvifolius Benth. (aerial parts) showed potent activity against HIV-1 IN with an IC50 value of 9.2 microg/mL. From this extract, 11 compounds were isolated and identified as luteolin 5-O-beta-d-glucopyranoside (1), luteolin (2), luteolin 7-methyl ether (3), luteolin 5-O-beta-d-glucuronide (4), 5-O-beta-d-glucopyranosyl-luteolin 7-methyl ether (5), rosmarinic acid (6), rosmarinic acid methyl ester (7), daucosterol (8), a mixture of alpha- and beta-amyrin (9, 10) and phytol (11). Of these compounds, rosmarinic acid methyl ester (7), rosmarinic acid (6), luteolin (2) and luteolin 7-methyl ether (3) exhibited inhibitory activities against HIV-1 IN with IC50 values of 3.1, 5.0, 11.0 and 11.0 microM, respectively. Among rosmarinic acid derivatives, the HIV-1 IN inhibitory activity increased in turn for a dimer (IC50 = 5.0 microM), a trimer (IC50 = 1.4 microM), and a tetramer (IC50 = 1.0 microM).

Functional oligomeric state of avian sarcoma virus integrase

Retroviral integrase, one of only three enzymes encoded by the virus, catalyzes the essential step of inserting a DNA copy of the viral genome into the host during infection. Using the avian sarcoma virus integrase, we demonstrate that the enzyme functions as a tetramer. In presteady-state active site titrations, four integrase protomers were required for a single catalytic turnover. Volumetric determination of integrase-DNA complexes imaged by atomic force microscopy during the initial turnover additionally revealed substrate-induced assembly of a tetramer. These results suggest that tetramer formation may be a requisite step during catalysis with ramifications for antiviral design strategies targeting the structurally homologous human immunodeficiency virus, type 1 (HIV-1) integrase.

Chemical modification of coumarin dimer and HIV-1 integrase inhibitory activity

A systematic series of chemically modified coumarin dimmers has been synthesized and tested for their inhibitory activity against HIV-1 integrase. We observed that modified coumarin dimmers containing hydrophobic moiety on the linker display potent inhibitory activities.

Inhibition of feline immunodeficiency virus (FIV) replication by DNA binding polyamides

Two DNA minor-groove binding polyamides 1 and 2 were designed and synthesized and evaluated for inhibition of FIV-34TF10 replication. Both 1 and 2 decreased the replication of FIV-34TF10 by 75% by acting at the level of the virus but outside of the LTR or env region.

New class of HIV integrase inhibitors that block viral replication in cell culture

BACKGROUND

To improve the existing combination therapies of infection with the human immunodeficiency virus (HIV) and to cope with virus strains that are resistant to multiple drugs, we initiated a search for effective inhibitors of HIV integrase, the enzyme responsible for inserting the viral cDNA into the host cell chromosome.

RESULTS

We have now identified a series of 5H-pyrano[2,3-d:-6,5-d']dipyrimidines that block the replication of various strains of HIV-1 and HIV-2. The most potent congener, 5-(4-nitrophenyl)-2,8-dithiol-4,6-dihydroxy-5H-pyrano[2,3-d:-6,5-d']dipyrimidine (V-165), inhibited the replication of HIV-1(III(B)) in MT-4 cells at a 50% effective concentration (EC(50)) of 8.9 microM, which is 14-fold below its cytotoxic concentration. V-165 was equally active against virus strains that were resistant toward inhibitors of viral entry or reverse transcriptase. In combination regimens in cell culture, V-165 acted subsynergistically with zidovudine or nelfinavir and synergistically with nevirapine. V-165 inhibited both reverse transcriptase and integrase activities in enzymatic assays at micromolar concentrations, but only a close correlation was found between the anti-HIV activity observed in cell culture and the inhibitory activity in the integrase strand transfer assays. Time-of-addition experiments indicated that V-165 interfered with the viral replication cycle at a time point coinciding with integration. Quantitative Alu-PCR corroborated that the anti-HIV activity of V-165 is based upon the inhibition of proviral DNA integration.

CONCLUSIONS

Based on their mode of action, which is different from that of clinically approved anti-HIV drugs, PDPs are good candidates for further development into new drugs and to be included in future combination regimens.

In vitro antimicrobial activity of a new series of 1,4-naphthoquinones

The antibacterial activity of a series of 1,4-naphthoquinones was demonstrated. Disk diffusion tests were carried out against several Gram-positive and Gram-negative bacteria. The compound 5-amino-8-hydroxy-1,4-naphthoquinone was the most effective, presenting inhibition zones measuring 20 mm against staphylococci, streptococci and bacilli at 50 microg/ml. Methicillin-resistant Staphylococcus aureus and several clinical isolates of this bacterium were also inhibited. Naphthazarin, 5-acetamido-8-hydroxy-1,4-naphthoquinone, and 2,3-diamino-1,4-naphthoquinone were the next most active compounds. The minimal inhibitory concentration of the active compounds was determined against S. aureus, ranging from 30 to 125 microg/ml. All compounds presented a minimal bactericidal concentration higher than 500 microg/ml, indicating that their effect was bacteriostatic. The EC50, defined as the drug concentration that produces 50% of maximal effect, was 8 microg/ml for 5-amino-8-hydroxy-1,4-naphthoquinone against S. aureus, S. intermedius, and S. epidermidis. These results indicate an effective in vitro activity of 5-amino-8-hydroxy-1,4-naphthoquinone and encourage further studies for its application in antibiotic therapy.

QSAR of HIV-1 integrase inhibitors by genetic function approximation method

Quantitative structure--activity relationship (QSAR) paradigm, using genetic function approximation (GFA) technique was used to examine the correlations between the calculated physicochemical descriptors and the in vitro activities (3'-processing and 3'-strand transfer inhibition) of a series of human immunodeficiency virus type 1 (HIV-1) integrase inhibitors. Depending on the chemical structure, all molecules were divided into two classes---catechols and noncatechols. Eighty-one molecules were used in the present study and they were divided into training set and test set. The training set in each class consisted of 35 molecules and QSAR models were generated separately for both catechols and noncatechols. Equations were evaluated using internal as well as external test set predictions. Models generated for catechols show that electronic, shape related, and thermodynamic parameters are important whereas for noncatechols, spatial, structural, and thermodynamic properties play an important role for the activity.

Antipruritic effects of 1,4-naphthoquinones and related compounds

The antipruritic effects of orally administered 1,4-naphthoquinone derivatives and related compounds on compound 48/80-induced scratching behavior in mice were studied. 2-Hydroxy-3-(2-hydroxyethyl)-1,4-naphthoquinone, ferulic acid, 2,2'-methylenebis(3-hydroxy-1,4-naphthoquinone), and 2,2'-ethylidenebis(3-hydroxy-1,4-naphthoquinone) (impatienol) all exhibited significant antipruritic activity. However, 2-methoxy-3-(2-hydroxyethyl)-1,4-naphthoquinone (balsaquinone), which was isolated from a natural source for the first time, did not show any activity. The present results indicate that these compounds are promising for treating allergic diseases with chronic and severe pruritus.

Synthesis and HIV-1 integrase inhibitory activities of catechol and bis-catechol derivatives

Fourteen catechol and bis-catechol derivatives have been synthesised and tested for their HIV-1 inhibitory activities. The six more active molecules have been tested for their antiviral activity and cytotoxicity. We have found that bis-catechols 1 and 2 are the most active HIV-1 integrase inhibitor whereas the best antiviral compound is 4.

Eigen value analysis of HIV-1 integrase inhibitors

A three-dimensional quantitative structure activity relationship using the eigen value analysis (EVA) paradigm applied to 41 HIV-1 integrase inhibitors that inhibit integrase mediated cleavage (3'-processing step) and integration (3'-strand transfer step) in vitro was performed. The training set consisted of 35 molecules from five structurally diverse classes: salicylhydrazines, lichen acids, coumarins, quinones, and thiazolothiazepines. Models derived using semiempirical (MOPAC AM1 and PM3) calculated normal-mode frequencies were compared. The predictive ability of each resultant model was evaluated using a test set comprised of six molecules belonging to a different structural class: hydrazides. Models derived using AM1 method showed considerable internal as well as external predictivity (r(2)(cv) = 0.806, r(2)(pred) = 0.761 for 3'-processing and r(2)(cv) = 0.677, r(2)(pred) = 0.591 for 3'-strand transfer).

Molecular electrostatic potentials as input for the alignment of HIV-1 integrase inhibitors in 3D QSAR

Comparative molecular similarity indices analysis (CoMSIA), a three-dimensional quantitative structure activity relationship (3D QSAR) paradigm, was used to examine the correlations between the calculated physicochemical properties and the in vitro activities (3'-processing and 3'-strand transfer inhibition) of a series of human immunodeficiency virus type 1 (HIV-1) integrase inhibitors. The training set consisted of 34 molecules from five structurally diverse classes: salicylpyrazolinones, dioxepinones, coumarins, quinones, and benzoic hydrazides. The data set was aligned using extrema of molecular electrostatic potentials (MEPs). The predictive ability of the resultant model was evaluated using a test set comprised of 7 molecules belonging to a different structural class of thiazepinediones. A CoMSIA model using an MEP-based alignment showed considerable internal as well external predictive ability (r2(cv) = 0.821, r2(pred) = 0.608 for 3'-processing; and r2(cv) = 0.759, r2(pred.) = 0.660 for 3'-strand transfer).

Targeting HIV-1 integrase

Human immunodeficiency virus Type 1 (HIV-1) integrase is an essential enzyme for the obligatory integration of the viral DNA into the infected cell chromosome. As no cellular homologue of HIV integrase has been identified, this unique HIV-1 enzyme is an attractive target for the development of new therapeutics. Treatment of HIV-1 infection and AIDS currently consists of the use of combinations of HIV-1 inhibitors directed against reverse transcriptase (RT) and protease. However, their numerous side effects and the rapid emergence of drug-resistant variants limit greatly their use in many AIDS patients. In principle, inhibitors of the HIV-1 integrase should be relatively non-toxic and provide additional benefits for AIDS chemotherapy. There have been many major advances in our understanding of the molecular mechanism of the integration reaction, although some critical aspects remain obscure. Several classes of compounds have been screened and further scrutinised for their inhibitory properties against the HIV integrase; however, there are currently no useful inhibitors available clinically for the treatment of AIDS patients. This review describes the current knowledge of the biological functions of the HIV-1 integrase and reports the major classes of integrase inhibitors identified to date.

Retroviral integrase inhibitors year 2000: update and perspectives

HIV-1 integrase is an essential enzyme for retroviral replication and a rational target for the design of anti-AIDS drugs. A number of inhibitors have been reported in the past 8 years. This review focuses on the recent developments in the past 2 years. There are now several inhibitors with known sites of actions and antiviral activity. The challenge is to convert these leads into drugs that will selectively target integrase in vivo, and can be added to our antiviral armamentarium.

Developing a dynamic pharmacophore model for HIV-1 integrase

We present the first receptor-based pharmacophore model for HIV-1 integrase. The development of "dynamic" pharmacophore models is a new method that accounts for the inherent flexibility of the active site and aims to reduce the entropic penalties associated with binding a ligand. Furthermore, this new drug discovery method overcomes the limitation of an incomplete crystal structure of the target protein. A molecular dynamics (MD) simulation describes the flexibility of the uncomplexed protein. Many conformational models of the protein are saved from the MD simulations and used in a series of multi-unit search for interacting conformers (MUSIC) simulations. MUSIC is a multiple-copy minimization method, available in the BOSS program; it is used to determine binding regions for probe molecules containing functional groups that complement the active site. All protein conformations from the MD are overlaid, and conserved binding regions for the probe molecules are identified. Those conserved binding regions define the dynamic pharmacophore model. Here, the dynamic model is compared to known inhibitors of the integrase as well as a three-point, ligand-based pharmacophore model from the literature. Also, a "static" pharmacophore model was determined in the standard fashion, using a single crystal structure. Inhibitors thought to bind in the active site of HIV-1 integrase fit the dynamic model but not the static model. Finally, we have identified a set of compounds from the Available Chemicals Directory that fit the dynamic pharmacophore model, and experimental testing of the compounds has confirmed several new inhibitors.

A new class of HIV-1 integrase inhibitors: the 3,3,3', 3'-tetramethyl-1,1'-spirobi(indan)-5,5',6,6'-tetrol family

Integration is a required step in HIV replication, but as yet no inhibitors of the integration step have been developed for clinical use. Many inhibitors have been identified that are active against purified viral-encoded integrase protein; of these, many contain a catechol moiety. Though this substructure contributes potency in inhibitors, it is associated with toxicity and so the utility of catechol-containing inhibitors has been questioned. We have synthesized and tested a systematic series of derivatives of a catechol-containing inhibitor (1) with the goal of identifying catechol isosteres that support inhibition. We find that different patterns of substitution on the aromatic ring suffice for inhibition when Mn(2+) is used as a cofactor. Importantly, the efficiency is different when Mg(2+), the more likely in vivo cofactor, is used. These data emphasize the importance of assays with Mg(2+) and offer new catechol isosteres for use in integrase inhibitors.