Usabamycins A-C: new anthramycin-type analogues from a marine-derived actinomycete

New anthramycin-type analogues, designated usabamycin A-C (1, 2 and 3), have been isolated from cultures of Streptomyces sp. NPS853, a bacterium found in marine sediments. The structures of the new compounds were established on the basis of extensive spectroscopic analyses including 1D- and 2D-NMR ((1)H-(1)H COSY, HSQC, and HMBC) experiments. The usabamycins show weak inhibition of HeLa cell growth and selective inhibition of serotonin (5-hydroxytrypamine) 5-HT(2B) uptake.     

Potential inhibitors of HIV integrase.

In the search for inhibitors of HIV integrase, the enzyme involved in the integration of viral DNA into host DNA, we have synthesized and studied a number of analogs of the heterocyclic molecule, chloroquine.     

Caffeoyl naphthalenesulfonamide derivatives as HIV integrase inhibitors

HIV-1 integrase (IN) is an essential enzyme for retroviral replication and a rational target for the design of anti-AIDS drugs. In the present study, we have designed, synthesized and tested a series of caffeoyl naphthalenesulfonamide derivatives as HIV integrase inhibitors. Among these compounds, we found that HIV integrase inhibitory activities of compounds III-3 and III-4 were more potent than L-chicoric acid (IC(50)=11.8 microg/mL) and others were comparable to L-chicoric acid. Furthermore, the structure-activity relationships of these compounds were studied. The information gathered from this paper will be useful in the development and design of HIV-1 integrase inhibitors in the future.     

A platform for designing HIV integrase inhibitors. Part 2: a two-metal binding model as a potential mechanism of HIV integrase inhibitors

We propose a two-metal binding model as a potential mechanism of chelating inhibitors against HIV integrase (HIV IN) represented by 2-hydroxy-3-heteroaryl acrylic acids (HHAAs). Potential inhibitors would bind to two metal ions in the active site of HIV IN to prevent human DNA from undergoing the integration reaction. Correlation of the results of metal (Mg²⁺ and Mn²⁺) titration studies with HIV IN inhibition for a series of active and inactive compounds provides support for the model. Results suggest Mg²⁺ is an essential cofactor for chelating inhibitors.     

Catechol-substituted L-chicoric acid analogues as HIV integrase inhibitors

HIV integrase catalyzes the integration of HIV DNA copy into the host cell DNA, which is essential for the production of progeny viruses. L-Chicoric acid and dicaffeoylquinic acids, isolated from plants, are well known potent inhibitors of HIV integrase. The common structural features of these inhibitors are caffeic acid derivatives connected to tartaric acid or quinic acid through ester bonds. In the present study, we have synthesized and tested the inhibitory activities of a new type of HIV IN inhibitors, which has catechol groups in place of caffeoyl groups in the structure of L-chicoric acid. Upon substitution of catechol groups at succinic acid, pyrrole-dicarboxylic acid, maleimide or maleic anhydride, the inhibitory activities (IC(50)=3.8-23.6 microM) were retained or remarkably increased when compared to parent compound L-chicoric acid (IC(50)=13.7 microM).     

A new procedure for the phosphorylation of nucleosides: application to the discovery of inhibitors of HIV integrase

A new phosphorylating agent for nucleosides, 2-O-(4,4'-dimethoxytrityl) ethylsulfonylethan-2'-yl-phosphate (1), has been developed by us. In the many examples studied by us, phosphorylation yields were found to be very high (about 90%). The procedure appears to be remarkably general and can be utilized for the phosphorylation of many biomolecules. Successful application of this phosphorylation method has contributed to the discovery of inhibitors of HIV integrase in our laboratory.     

Discovery of potent HIV integrase inhibitors active against raltegravir resistant viruses

A series of novel HIV integrase inhibitors active against rategravir resistant strains are reported. Initial SAR studies revealed that activities against wild-type virus were successfully maintained at single digit nanomolar level with a wide range of substitutions. However, inclusion of nitrogen-based cyclic substitutions was crucial for achieving potency against mutant viruses. Several compounds with excellent activities against wild-type virus as well as against the viruses with the mutations Q148H/G140S or N155H/E92Q were reported.     

Tricyclic HIV integrase inhibitors: potent and orally bioavailable C5-aza analogs

A series of C5-aza tricyclic HIV integrase inhibitors was prepared. A highly potent and orally bioavailable compound (compound 9) was identified and selected for development.     

Development of 2-t butyl-N-methyl pyrimidones as potent inhibitors of HIV integrase

A series of novel 2-(t)butyl-N-methyl pyrimidone HIV-1 integrase inhibitors have been identified. Optimization of the initial lead resulted in compounds such as 9d and 14a, which showed high levels of activity in cell culture inhibiting viral replication with CIC(95) of 10nM in the presence of 50% normal human serum.     

Conformationally restrained carbazolone-containing alpha,gamma-diketo acids as inhibitors of HIV integrase

Since alpha,gamma-diketo acid (DKA) compounds were identified as potent and selective inhibitors for HIV integrase, numerous structural modification studies have been carried out to search for a clinical candidate as a supplement for the highly active antiretroviral therapy regimen. Due to the lack of structural information on inhibitor-integrase interactions, a comprehensive structure-activity relationship study is necessary. Most of the reported modification studies on the key alpha,gamma-diketo acid pharmacophore focused on substituting the carboxylate moiety with its bioisosteres or other electron-pair bearing heterocycles. We were interested in studying the conformation and geometry of the central diketo moiety. A series of carbazolone-containing alpha,gamma-diketo acids were designed and synthesized by applying conformational restraint onto the open-chain form of the diketo acid. These compounds showed anti-integrase activity in the low micromolar range, and integrase assay results indicated that the geometry of the diketo acid moiety is crucial to potency. Carbazol-1-one containing DKA analogs (7-8) showed a 2- to 3-fold increase in activity compared with those of carbazol-4-one containing DKA analogs (5 and 6). Alkylation of carbazol-4-one DKA nitrogen (6a-c) led to a loss of activity, suggesting this nitrogen atom may directly interact with the active site of integrase. The halogens (7b-d) and para-fluorobenzyl substituents (8a-d) on carbazol-1-one ring had little effect on potency.     

Microarray compound screening (microARCS) to identify inhibitors of HIV integrase

A novel high-throughput strand transfer assay has been developed, using Microarray Compound Screening (microARCS) technology, to identify inhibitors of human immunodeficiency virus (HIV) integrase. This technology utilizes agarose matrices to introduce a majority of the reagents throughout the assay. Integration of biotinylated donor DNA with fluorescein isothiocyanate (FITC)-labeled target DNA occurs on a SAM membrane in the presence of integrase. An anti-FITC antibody conjugated to alkaline phosphatase (AP) was used to do an enzyme-linked immunosorbent assay with the SAM. An agarose gel containing AttoPhos, a substrate of AP, was used for detection of the integrase reactions on the SAM. For detection, the AttoPhos gel was separated from the SAM after incubation and then the gel was imaged using an Eagle Eye II closed-circuit device camera system. Potential integrase inhibitors appear as dark spots on the gel image. A library of approximately 250,000 compounds was screened using this HIV integrase strand transfer assay in microARCS format. Compounds from different structural classes were identified in this assay as novel integrase inhibitors.     

Changes to the HIV long terminal repeat and to HIV integrase differentially impact HIV integrase assembly, activity, and the binding of strand transfer inhibitors

Human immunodeficiency virus (HIV) integrase enzyme is required for the integration of viral DNA into the host cell chromosome. Integrase complex assembly and subsequent strand transfer catalysis are mediated by specific interactions between integrase and bases at the end of the viral long terminal repeat (LTR). The strand transfer reaction can be blocked by the action of small molecule inhibitors, thought to bind in the vicinity of the viral LTR termini. This study examines the contributions of the terminal four bases of the nonprocessed strand (G(2)T(1)C(-1)A(-2)) of the HIV LTR on complex assembly, specific strand transfer activity, and inhibitor binding. Base substitutions and abasic replacements at the LTR terminus provided a means to probe the importance of each nucleotide on the different functions. An approach is described wherein the specific strand transfer activity for each integrase/LTR variant is derived by normalizing strand transfer activity to the concentration of active sites. The key findings of this study are as follows. 1) The G(2):C(2) base pair is necessary for efficient assembly of the complex and for maintenance of an active site architecture, which has high affinity for strand transfer inhibitors. 2) Inhibitor-resistant enzymes exhibit greatly increased sensitivity to LTR changes. 3) The strand transfer and inhibitor binding defects of a Q148R mutant are due to a decreased affinity of the complex for magnesium. 4) Gln(148) interacts with G(2), T(1), and C(-1) at the 5' end of the viral LTR, with these four determinants playing important and overlapping roles in assembly, strand transfer catalysis and high affinity inhibitor binding.     

Tricyclic HIV integrase inhibitors V. SAR studies on the benzyl moiety

SAR studies on the para-fluorobenzyl moiety of tricyclic HIV integrase inhibitors are discussed and lead compounds with potency and PK properties comparable to raltegravir were identified.     

Dicaffeoyl- or digalloyl pyrrolidine and furan derivatives as HIV integrase inhibitors.

Human immunodeficiency virus (HIV) integrase (IN) catalyzes the integration of HIV DNA copy into the host cell DNA. Such integration is essential for the production of progeny viruses, and therefore therapeutic agents that can inhibit this process should be effective anti-HIV agents. We have previously reported the inhibitory activity of dicaffeoylglucosides against HIV IN. In the present study, we have synthesized and tested dicaffeoyl or digalloyl compounds joined through a five-membered heterocyclic ring as HIV IN inhibitors to explore the SARs of this family of compounds. The starting heterocyclic diols were prepared from L-tartaric acid, diethyl L-tartarate or D-(+)-ribonic gamma-lactone. We found that the HIV IN inhibitory activities of dicaffeoyl derivatives were comparable to that of L-chicoric acid (IC(50)=24.9 microM). On the other hand, digalloyl derivatives were more potent than L-chicoric acid with IC(50) values of 4.7--15.6 microM.     

Development of 2-pyrrolidinyl-N-methyl pyrimidones as potent and orally bioavailable HIV integrase inhibitors

A series of 2-pyrrolidinyl-N-methyl pyrimidones HIV integrase inhibitors has been explored leading to the identification of derivative 13, which showed high activity at inhibiting viral replication in cell culture, favorable pharmacokinetic profile in two preclinical species, and an attractive profile against a panel of HIV-integrase mutants.     

3-Hydroxy-1,5-dihydro-pyrrol-2-one derivatives as advanced inhibitors of HIV integrase

The two-metal binding model we previously reported as an inhibition mechanism of HIV integrase (HIV IN) produced a new direction in modification of 2-hydroxy-3-heteroaryl acrylic acid inhibitors (HHAAs). Here we present a novel series of HIV IN inhibitors having a 3-hydroxy-1,5-dihydro-pyrrol-2-one moiety (HDPO) as an advanced analog of HHAAs. This cyclic modification of the chelating region of HHAA produces a favorable configuration to coordinate two-metal ions in HIV IN, which consequently gave improvements in not only enzymatic assay but also antiviral cell based assay in many cases.     

Computer-assisted search and optimization of new human immunodeficiency virus integrase inhibitors

Finding and optimization of new HIV-1 integrase inhibitors is an important task due to the drawbacks of the existing HIV/AIDS therapy caused by the significant adverse effects, high cost of the treatment, and emerging resistance. In this study we have demonstrated potential of computer-assisted methods for finding and optimization of new HIV-1 integrase inhibitors blocking the 3′-processing reaction. Applicability of the specialized version of the computer program PASS for searching original inhibitors of 3′-processing reaction among commercially available samples of chemical compounds, belonging to a new chemical class, is shown. We compared the general pharmacological profiles calculated by PASS for the sets of original integrase inhibitors found in the study with those for known inhibitors published in literature. It was shown that the predicted average selectivity is close for the compounds from both sets, while the probability of predicted adverse/toxic effects is lower for the original compounds. Differences between the pharmacological profiles of original compounds and inhibitors of 3′-processing known in the literature pointed out to the essential novelty of our substances of the investigated chemical class. Significantly less deviations from the recommended values for QikProp parameters, which characterized the ADME properties, have been observed for the original compounds than for the integrase inhibitors published in literature. Thus, one can conclude that the original compounds look more prospective comparing to the earlier known inhibitors of 3′-processing.     

Triketoacid inhibitors of HIV-integrase: a new chemotype useful for probing the integrase pharmacophore

Integrase is one of three enzymes expressed by HIV and represents a validated target for therapy. This study reports on the discovery of a new triketoacid-based chemotype that selectively inhibits the strand transfer reaction of HIV-integrase. SAR studies showed that the template binds to integrase in a manner similar to the diketoacid-based inhibitors. Moreover, comparison of the new chemotype to two different diketoacid templates led us to propose two aryl-binding domains in the inhibitor binding site. This information was used to design a new diketoacid template with improved activity against the enzyme.     

A QSAR study on a series of N-methyl pyrimidones acting as HIV integrase inhibitors

A quantitative structure-activity relationship (QSAR) study has been performed on integrase (IN) inhibition activity of a large series of N-methyl pyrimidones [Gardelli et al. (2007) J Med Chem 50, 4953-4975)] having varying heterocyclic ring substitution at 2-position of pyrimidone ring. The activity is found to be significantly correlated with surface tension and molar volume of the molecules. The whole series of compounds is divided into two subsets: a training set and a test set. A significant correlation is obtained for the training set, which is then used to predict the activity of compounds in the test set. The predicted activities of compounds in the test set are found to be very close to their observed activities. The predicting ability of the correlation obtained is judged by leave-one-out jackknife procedure. The correlation shows the effective role of the surface tension and molar volume of the molecules. From the correlation obtained, the integrase inhibition activities are predicted for some new prospective compounds.