Structure-activity relationship of pyrrolyl diketo acid derivatives as dual inhibitors of HIV-1 integrase and reverse transcriptase ribonuclease H domain

Natural product-inspired esters and amides of ferulic and caffeic acid as dual inhibitors of HIV-1 reverse transcriptase

Using an HIV-1 Reverse Transcriptase (RT)-associated RNase H inhibition assay as lead, bioguided fractionation of the dichloromethane extract of the Ocimum sanctum leaves led to the isolation of five triterpenes (1-5) along with three 3-methoxy-4-hydroxy phenyl derivatives (6-8). The structure of this isolates were determined by 1D and 2D NMR experiments as well as ESI-MS. Tetradecyl ferulate (8) showed an interesting RNase H IC₅₀ value of 12.4 μM and due to the synthetic accessibility of this secondary metabolite, a structure-activity relationship study was carried out. A series of esters and amides of ferulic and caffeic acids were synthesized and, among all, the most active was N-oleylcaffeamide displaying a strong inhibitory activity towards both RT-associated functions, ribonuclease H and DNA polymerase. Molecular modeling studies together with Yonetani-Theorell analysis, demonstrated that N-oleylcaffeamide is able to bind both two allosteric site located one close to the NNRTI binding pocket and the other close to RNase H catalytic site.

Natural Product Kuwanon-L Inhibits HIV-1 Replication through Multiple Target Binding

In recent years many advances have been made in the fight against HIV-1 infection. However, the lack of a vaccine, together with the increasing resistance to the highly active anti-retroviral therapy (HAART), make HIV-1 infection still a serious global emergency. Thus, new compounds with original modes of action are continuously required, and natural products have ever been a very interesting class of pharmacologically active molecules. Some of them have been used since ancient times against viral infections. Here we present a work in which we suggest that kuwanon-L, a natural product active as an HIV-1 integrase (IN) inhibitor, might exert its overall antiviral activity through binding to multiple viral targets. Specific enzymatic tests, together with a time-of-addition (TOA) experiment, support our hypothesis of binding both to IN and to reverse transcriptase (RT). Overall, this compound can be considered an attractive lead for the development of new classes of antiviral agents able to overcome the problem of resistance, due to its ability to exert its action by binding simultaneously to multiple viral targets.

[Nitrobenzofuroxane derivatives as dual action hiv-1 inhibitors]

Human immunodeficiency virus first type (HIV-1) is a main cause of one of the most dangerous diseases, AIDS. The search for new inhibitors of the virus still remains an urgent task. One approach to suppress the HIV infection is to use a double-acting inhibitors, i.e. inhibitors directed to two stages of the viral life cycle. The catalytic domain of HIV-1 integrase has a similar spatial organization with ribonuclease (RNase H) domain of HIV-1 reverse transcriptase, and approach aimed to create HIV-1 integrase and RNase H double-acting is very promising. In this work we synthesized a series of 6-nitrobenzofuroxane derivatives and studied their ability to inhibit two viral enzymes - integrase and RNase H HIV-1.

Sennoside A, derived from the traditional chinese medicine plant Rheum L., is a new dual HIV-1 inhibitor effective on HIV-1 replication

BACKGROUND

Despite the availability of effective antiretroviral therapies, drugs for HIV-1 treatment with new mode of action are still needed. An innovative approach is aimed to identify dual HIV-1 inhibitors, small molecules that can inhibit two viral functions at the same time. Rhubarb, originated from Rheum palmatum L. and Rheum officinale Baill., is one of the earliest and most commonly used medicinal plants in Traditional Chinese Medicine (TCM) practice. We wanted to explore TCM for the identification of new chemical scaffolds with dual action abilities against HIV-1.

METHODS

R. palmatum L. and R. officinale Baill. extracts along with their main single isolated constituents anthraquinone derivatives were tested on both HIV-1 Reverse Transcriptase (RT)-associated DNA Polymerase (RDDP) and Ribonuclease H (RNase H) activities in biochemical assays. Active compounds were then assayed for their effects on HIV-1 mutated RTs, integrase (IN) and viral replication.

RESULTS

Both R. palmatum L. and R. officinale Baill. extracts inhibited the HIV-1 RT-associated RNase H activity. Among the isolated constituents, Sennoside A and B were effective on both RDDP and RNase H RT-associated functions in biochemical assays. Sennoside A was less potent when tested on K103N, Y181C, Y188L, N474A and Q475A mutated RTs, suggesting the involvement of two RT binding sites for its antiviral activity. Sennoside A affected also HIV-1 IN activity in vitro and HIV-1 replication in cell-based assays. Viral DNA production and time of addition studies showed that Sennoside A targets the HIV-1 reverse transcription process.

CONCLUSION

Sennoside A is a new scaffold for the development of HIV-1 dual RT inhibitors.

New insights into the interaction between pyrrolyl diketoacids and HIV-1 integrase active site and comparison with RNase H

HIV-1 integrase (IN) inhibitors are one of the most recent innovations in the treatment of HIV infection. The selection of drug resistance viral strains is however a still open issue requiring constant efforts to identify new anti-HIV-1 drugs. Pyrrolyl diketo acid (DKA) derivatives inhibit HIV-1 replication by interacting with the Mg²⁺ cofactors within the HIV-1 IN active site or within the HIV-1 reverse-transcriptase associated ribonuclease H (RNase H) active site. While the interaction mode of pyrrolyl DKAs with the RNase H active site has been recently reported and substantiated by mutagenesis experiments, their interaction within the IN active site still lacks a detailed understanding. In this study, we investigated the binding mode of four pyrrolyl DKAs to the HIV-1 IN active site by molecular modeling coupled with site-directed mutagenesis studies showing that the DKA pyrrolyl scaffold primarily interacts with the IN amino residues P145, Q146 and Q148. Importantly, the tested DKAs demonstrated good effectiveness against HIV-1 Raltegravir resistant Y143A and N155H INs, thus showing an interaction pattern with relevant differences if compared with the first generation IN inhibitors. These data provide precious insights for the design of new HIV inhibitors active on clinically selected Raltegravir resistant variants. Furthermore, this study provides new structural information to modulate IN and RNase H inhibitory activities for development of dual-acting anti-HIV agents.

Inhibitory Effect of 2,3,5,6-Tetrafluoro-4-[4-(aryl)-1H-1,2,3-triazol-1-yl]benzenesulfonamide Derivatives on HIV Reverse Transcriptase Associated RNase H Activities

The HIV-1 ribonuclease H (RNase H) function of the reverse transcriptase (RT) enzyme catalyzes the selective hydrolysis of the RNA strand of the RNA:DNA heteroduplex replication intermediate, and represents a suitable target for drug development. A particularly attractive approach is constituted by the interference with the RNase H metal-dependent catalytic activity, which resides in the active site located at the C-terminus p66 subunit of RT. Herein, we report results of an in-house screening campaign that allowed us to identify 4-[4-(aryl)-1H-1,2,3-triazol-1-yl]benzenesulfonamides, prepared by the "click chemistry" approach, as novel potential HIV-1 RNase H inhibitors. Three compounds (9d, 10c, and 10d) demonstrated a selective inhibitory activity against the HIV-1 RNase H enzyme at micromolar concentrations. Drug-likeness, predicted by the calculation of a panel of physicochemical and ADME properties, putative binding modes for the active compounds, assessed by computational molecular docking, as well as a mechanistic hypothesis for this novel chemotype are reported.

Studies on Cycloheptathiophene-3-carboxamide Derivatives as Allosteric HIV-1 Ribonuclease H Inhibitors

Despite the significant progress achieved with combination antiretroviral therapy in the fight against human immunodeficiency virus (HIV) infection, the difficulty to eradicate the virus together with the rapid emergence of multidrug-resistant strains clearly underline a pressing need for innovative agents, possibly endowed with novel mechanisms of action. In this context, owing to its essential role in HIV genome replication, the reverse transcriptase associated ribonuclease H (RNase H) has proven to be an appealing target. To identify new RNase H inhibitors, an in-house cycloheptathiophene-3-carboxamide library was screened; this led to compounds endowed with inhibitory activity, the structural optimization of which led to the catechol derivative 2-(3,4-dihydroxybenzamido)-N-(pyridin-2-yl)-5,6,7,8-tetrahydro-4H-cyclohepta[b]thiophene-3-carboxamide (compound 33) with an IC50 value on the RNase H activity in the nanomolar range. Mechanistic studies suggested selective inhibition of the RNase H through binding to an innovative allosteric site, which could be further exploited to enrich this class of inhibitors.

Progress in HIV-1 Integrase Inhibitors: A Review of their Chemical Structure Diversity

HIV-1 integrase (IN) enzyme, one of the three main enzymes of HIV-1, catalyzed the insertion of the viral DNA into the genome of host cells. Because of the lack of its homologue in human cells and its essential role in HIV-1 replication, IN inhibition represents an attractive therapeutic target for HIV-1 treatment. Since identification of IN as a promising therapeutic target, a major progress has been made, which has facilitated and led to the approval of three drugs. This review focused on the structural features of the most important IN inhibitors and categorized them structurally in 10 scaffolds. We also briefly discussed the structural and functional properties of HIV-1 IN and binding modes of IN inhibitors. The SAR analysis of the known IN inhibitors provides some useful clues to the possible future discovery of novel IN inhibitors.

Anti-HIV Drug Discovery and Development: Current Innovations and Future Trends

The early effectiveness of combinatorial antiretroviral therapy (cART) in the treatment of HIV infection has been compromised to some extent by rapid development of multidrug-resistant HIV strains, poor bioavailability, and cumulative toxicities, and so there is a need for alternative strategies of antiretroviral drug discovery and additional therapeutic agents with novel action modes or targets. From this perspective, we first review current strategies of antiretroviral drug discovery and optimization, with the aid of selected examples from the recent literature. We highlight the development of phosphate ester-based prodrugs as a means to improve the aqueous solubility of HIV inhibitors, and the introduction of the substrate envelope hypothesis as a new approach for overcoming HIV drug resistance. Finally, we discuss future directions for research, including opportunities for exploitation of novel antiretroviral targets, and the strategy of activation of latent HIV reservoirs as a means to eradicate the virus.

Selective Formation of ortho-Aminobenzylamines by the Copper-Catalyzed Amination of Benzylamine Boronate Esters

The copper-catalyzed coupling between benzylamino boronate esters and aryl amines has been investigated. Formation of ortho-aminobenzylamines was achieved under oxidative conditions in the presence of copper(II) acetate. The major side product of the transformation is the homocoupling of the aryl boronate ester. The formation of the desired diamines was found to be improved in the absence of base, increasing selectivity over the homocoupled product. Both electron-donating and electron-withdrawing substituents are tolerated on both the boronate ester substrate and the aniline coupling partner under the reaction conditions. The presence of the adjacent benzylamine moiety appears to enhance the reactivity of the boronate ester and influence the resulting product distribution, likely by affecting the competing rates of transmetalation in the catalytic cycles.