Discovery and Synthesis of HIV Integrase Inhibitors: Development of Potent and Orally Bioavailable N-Methyl Pyrimidones

A mini-review on integrase inhibitors: The cornerstone of next-generation HIV treatment

Integrase inhibitors represent one of the most remarkable and effective advances in the treatment of HIV-1 infection. Their lack of human cellular equivalence has established integrase as a unique and ideal target for HIV-1 treatment. Over the last two decades, a variety of drugs and small molecule inhibitors have been developed to control or treat HIV infection. Many of these FDA-approved drugs are considered first-line options for AIDS patients. Unfortunately, resistance to these drugs has dictated the development of novel and more efficacious antiretroviral drugs. In this review article, we illustrate the key classes of antiretroviral integrase inhibitors available. We provide a comprehensive analysis of recent advancements in the development of integrase inhibitors, focusing on novel compounds and their distinct mechanisms of action. Our literature review highlights emerging allosteric integrase inhibitors that offer improved efficacy, resistance profiles, and pharmacokinetics. By integrating these recent advancements and clinical insights, this review aims to provide a thorough and updated understanding of integrase inhibitors, emphasizing their evolving role in HIV treatment.

Salinization Dramatically Enhance the Anti-Prostate Cancer Efficacies of AR/AR-V7 and Mnk1/2 Molecular Glue Degraders, Galeterone and VNPP433-3β Which Outperform Docetaxel and Enzalutamide in CRPC CWR22Rv1 Xenograft Mouse Model

Galeterone, 3β-(hydroxy)-17-(1H-benzimidazole-1-yl)androsta-5,16-diene (Gal, 1) and VNPP433-3β, 3β-(1H-imidazole-1-yl-17-(1H-benzimidazole-1-yl)androsta-5,16-diene (2) are potent molecular glue degrader modulators of AR/AR-V7 and Mnk1/2-eIF4E signaling pathways, and are promising Phase 3 and Phase 1 drug candidates, respectively. Because appropriate salts can be utilized to create new chemical entities with enhanced aqueous solubility, in vivo pharmacokinetics, and enhanced in vitro and in vivo efficacies, the monohydrochloride salt of Gal (3) and the mono- and di-hydrochlorides salts of compound 2, compounds 4 and 5, respectively, were synthesized. The salts were characterized using 1H NMR, 13C NMR and HRMS analyses. Compound 3 displayed enhanced in vitro antiproliferative activity (7.4-fold) against three prostate cancer cell lines but surprisingly decreased plasma exposure in the pharmacokinetics study. The antiproliferative activities of the compound 2 salts (4 and 5) were equivalent to that of compound 2, but their oral pharmacokinetic profiles were significantly enhanced. Finally, and most importantly, oral administration of the parent compounds (1 and 2) and their corresponding salts (3, 4 and 5) caused dose-dependent potent inhibition/regression of aggressive and difficult-to-treat CWR22Rv1 tumor xenografts growth, with no apparent host toxicities and were highly more efficacious than the blockbuster FDA-approved prostate cancer drugs, Enzalutamide (Xtandi) and Docetaxel (Taxotere). Thus, the HCl salts of Gal (3) and VNPP433-3β (4 and 5) are excellent orally bioavailable candidates for clinical development.

A convenient synthetic route to (2S,4S)-methylproline and its exploration for protein engineering of thioredoxin

4-Substituted prolines, especially 4-fluoroprolines, have been widely used in protein engineering and design. Here, we report a robust and stereoselective approach for the synthesis of (2S,4S)-methylproline starting from (2S)-pyroglutamic acid. Incorporation studies with both (2S,4R)- and (2S,4S)-methylproline into the Trx1P variant of the model protein thioredoxin of E. coli show that the stereochemistry of the 4-methyl group might be a key determinator for successful incorporation during ribosomal synthesis of this protein.

Integrase Strand Transfer Inhibitors Are Effective Anti-HIV Drugs

Integrase strand transfer inhibitors (INSTIs) are currently recommended for the first line treatment of human immunodeficiency virus type one (HIV-1) infection. The first-generation INSTIs are effective but can select for resistant viruses. Recent advances have led to several potent second-generation INSTIs that are effective against both wild-type (WT) HIV-1 integrase and many of the first-generation INSTI-resistant mutants. The emergence of resistance to these new second-generation INSTIs has been minimal, which has resulted in alternative treatment strategies for HIV-1 patients. Moreover, because of their high antiviral potencies and, in some cases, their bioavailability profiles, INSTIs will probably have prominent roles in pre-exposure prophylaxis (PrEP). Herein, we review the current state of the clinically relevant INSTIs and discuss the future outlook for this class of antiretrovirals.

An Enantioselective Approach to 4-Substituted Proline Scaffolds: Synthesis of (S)-5-(Tert-Butoxy Carbonyl)-5-Azaspiro[2.4]heptane-6-Carboxylic Acid

A catalytic and enantioselective preparation of the (S)-4-methyleneproline scaffold is described. The key reaction is a one-pot double allylic alkylation of an imine analogue of glycine in the presence of a chinchonidine-derived catalyst under phase transfer conditions. These 4-methylene substituted proline derivatives are versatile starting materials often used in medicinal chemistry. In particular, we have transformed tert-butyl (S)-4-methyleneprolinate (12) into the N-Boc-protected 5-azaspiro[2.4]heptane-6-carboxylic acid (1), a key element in the industrial synthesis of antiviral ledipasvir.

Development of a Raltegravir-based Photoaffinity-Labeled Probe for Human Immunodeficiency Virus-1 Integrase Capture

Photoaffinity labeling (PAL) is one of the upcoming and powerful tools in the field of molecular recognition. It includes the determination of dynamic parameters, such as the identification and localization of the target protein and the site of drug binding. In this study, a photoaffinity-labeled probe for full-length human immunodeficiency virus-1 integrase (HIV-1 IN) capture was designed and synthesized, following the structure of the FDA-approved drug Raltegravir. This photoprobe was found to retain the HIV IN inhibitory potential in comparison with its parent molecule and demonstrates the ability to label the HIV-1 IN protein. Putative photoprobe/inhibitor binding sites near the catalytic site were then identified after protein digestion coupled to mass and molecular modeling analyses.

5,6-Dihydroxypyrimidine Scaffold to Target HIV-1 Nucleocapsid Protein

The HIV-1 nucleocapsid (NC) protein is a small basic DNA and RNA binding protein that is absolutely necessary for viral replication and thus represents a target of great interest to develop new anti-HIV agents. Moreover, the highly conserved sequence offers the opportunity to escape the drug resistance (DR) that emerged following the highly active antiretroviral therapy (HAART) treatment. On the basis of our previous research, nordihydroguaiaretic acid 1 acts as a NC inhibitor showing moderate antiviral activity and suboptimal drug-like properties due to the presence of the catechol moieties. A bioisosteric catechol replacement approach led us to identify the 5-dihydroxypyrimidine-6-carboxamide substructure as a privileged scaffold of a new class of HIV-1 NC inhibitors. Hit validation efforts led to the identification of optimized analogs, as represented by compound 28, showing improved NC inhibition and antiviral activity as well as good ADME and PK properties.

Galeterone and The Next Generation Galeterone Analogs, VNPP414 and VNPP433-3β Exert Potent Therapeutic Effects in Castration-/Drug-Resistant Prostate Cancer Preclinical Models In Vitro and In Vivo

These studies compared the efficacies of our clinical agent galeterone (Gal) and the FDA-approved prostate cancer drug, enzalutamide (ENZ) with two lead next generation galeterone analogs (NGGAs), VNPP414 and VNPP433-3β, using prostate cancer (PC) in vitro and in vivo models. Antitumor activities of orally administered agents were also assessed in CWR22Rv1 tumor-bearing mice. We demonstrated that Gal and NGGAs degraded AR/AR-V7 and Mnk1/2; blocked cell cycle progression and proliferation of human PC cells; induced apoptosis; inhibited cell migration, invasion, and putative stem cell markers; and reversed the expression of epithelial-to-mesenchymal transition (EMT). In addition, Gal/NGGAs (alone or in combination) also inhibited the growth of ENZ-, docetaxel-, and mitoxantrone-resistant human PC cell lines. The NGGAs exhibited improved pharmacokinetic profiles over Gal in mice. Importantly, in vivo testing showed that VNPP433-3β (at 7.53-fold lower equimolar dose than Gal) markedly suppressed (84% vs. Gal, 47%; p < 0.01) the growth of castration-resistant PC (CRPC) CWR22Rv1 xenograft tumors, with no apparent host toxicity. ENZ was ineffective in this CRPC xenograft model. In summary, our findings show that targeting AR/AR-V7 and Mnk1/2 for degradation represents an effective therapeutic strategy for PC/CRPC treatment and supports further development of VNPP433-3β towards clinical investigation.

Targeting Metalloenzymes for Therapeutic Intervention

Metalloenzymes are central to a wide range of essential biological activities, including nucleic acid modification, protein degradation, and many others. The role of metalloenzymes in these processes also makes them central for the progression of many diseases and, as such, makes metalloenzymes attractive targets for therapeutic intervention. Increasing awareness of the role metalloenzymes play in disease and their importance as a class of targets has amplified interest in the development of new strategies to develop inhibitors and ultimately useful drugs. In this Review, we provide a broad overview of several drug discovery efforts focused on metalloenzymes and attempt to map out the current landscape of high-value metalloenzyme targets.

Photoredox-Catalyzed Cα-H Cyanation of Unactivated Secondary and Tertiary Aliphatic Amines: Late-Stage Functionalization and Mechanistic Studies

This paper describes the development and mechanistic studies of a general, high-yielding amine C_α-H cyanation protocol via photoredox catalysis. Inexpensive NaCN is employed as the cyanide source and air is the external oxidant, resulting in mild and highly functional group tolerant conditions. Notably, efficient C_α-H cyanations of secondary and tertiary aliphatic amines and of complex, biologically active compounds (drugs) can be performed using the established methodology. Mechanistic studies suggest that the carboxylic acid additive has three effects: formation of a stabilizing hemiaminal intermediate, prevention of catalyst decomposition by protonating the substrate, and modulation of fluorescence quenching of the photoexcited catalyst species.

Protein-Structure Assisted Optimization of 4,5-Dihydroxypyrimidine-6-Carboxamide Inhibitors of Influenza Virus Endonuclease

Influenza is a serious hazard to human health that causes hundreds of thousands of deaths annually. Though vaccines and current therapeutics can blunt some of the perilous impact of this viral infection, new treatments are needed due to the constantly evolving nature of this virus. Recently, our growing understanding of an essential influenza viral protein, PA, has led to the development of focused libraries of new small molecules that specifically target the active site of the PA influenza endonuclease, which we report here. Our overarching approach has been to proactively develop lead inhibitors that are less likely to rapidly develop clinical resistance by optimizing inhibitors that retain activity against induced resistant mutants. Here, we report details behind the discovery of new potent inhibitors of wild type and resistant mutant endonucleases along with their high-resolution co-crystal structure-activity relationships. These results add to our understanding of nuclease protein targets and potentially serve as starting points for a new therapeutic approach to the treatment of influenza.

Quantitative structure-activity relationship of anti-HIV integrase and reverse transcriptase inhibitors using norm indexes

The development of new and safe anti-human immunodeficiency virus (anti-HIV) drugs has been an urgent task for medical research recently. Herein, based on the norm-index descriptors proposed in this work and previous works, a couple of models were developed for investigating the quantitative structure-activity/toxicity relationship (QSAR/QSTR) of dual-target anti-HIV integrase (IN) and reverse transcriptase (RT) inhibitors. The validation results proved that the developed models were stable and reliable, both in statistical quality and predictive capacity. Moreover, potential dual-target inhibitors with high activity and low toxicity were deduced from the developed models; molecular docking results indicated that these inhibitors could interact with some important residues of HIV IN and RT through H-bonding. Accordingly, the norm indexes descriptors proposed by this work might be helpful for the research and development of dual-target anti-HIV drugs.

Stereoselective Polymer-Supported Synthesis of Morpholine- and Thiomorpholine-3-carboxylic Acid Derivatives

Herein we report the polymer-supported synthesis of 3,4-dihydro-2H-1,4-oxazine-3-carboxylic acid derivatives using immobilized Fmoc-Ser(tBu)-OH and Fmoc-Thr(tBu)-OH as the starting materials. After the solid-phase-synthesis of N-alkyl-N-sulfonyl/acyl intermediates, the target dihydrooxazines were obtained using trifluoroacetic acid-mediated cleavage from the resin. This approach was also studied for the preparation of dihydrothiazines from immobilized Fmoc-Cys(Trt)-OH. Inclusion of triethylsilane in the cleavage cocktail resulted in the stereoselective formation of the corresponding morpholine/thiomorpholine-3-carboxylic acids. Stereochemical studies revealed the specific configuration of the newly formed stereocenter and also the formation of stable N-acylmorpholine rotamers.

Multigram-scale Synthesis of Enantiopure 3,3-Difluoroproline

An efficient route for the synthesis of enantiopure 3,3-difluoroproline on multigram-scale is described herein. The deoxofluorination can be achieved with DAST on the corresponding racemic pyrrolidinone in good yield. Resolution of the racemate by crystallization with D- and L-tyrosine hydrazide provides both enantiomers of 3,3-difluoroproline in high yield and ee%.

Probing for improved selectivity with dipeptide-derived inhibitors of dipeptidyl peptidases 8 and 9: the impact of P1-variation

The influence of P1-variation on DPP8/9 inhibitor selectivity is investigated.

Catalytic Synthesis of N-Unprotected Piperazines, Morpholines, and Thiomorpholines from Aldehydes and SnAP Reagents

Commercially available SnAP (stannyl amine protocol) reagents allow the transformation of aldehydes and ketones into a variety of N-unprotected heterocycles. By identifying new ligands and reaction conditions, a robust catalytic variant that expands the substrate scope to previously inaccessible heteroaromatic substrates and new substitution patterns was realized. It also establishes the basis for a catalytic enantioselective process through the use of chiral ligands.

Targeting HIV-1 integrase with strand transfer inhibitors

HIV-1 integrase (IN) is a retroviral enzyme essential for integration of genetic material into the DNA of the host cell and hence for viral replication. The absence of an equivalent enzyme in humans makes IN an interesting target for anti-HIV drug design. This review briefly overviews the structural and functional properties of HIV-1 IN. We analyze the binding modes of the established drugs, clinical candidates and a comprehensive library of leads based on innovative chemical scaffolds of HIV-1 IN strand transfer inhibitors (INSTIs). Computational clustering techniques are applied for identifying structural features relating to bioactivity. From bio- and chemo-informatics analyses, we provide novel insights into structure-activity relationships of INSTIs and elaborate new strategies for design of innovative inhibitors.

Sketching the historical development of pyrimidones as the inhibitors of the HIV integrase

Heterocyclic substances perform a very unique role in drug design and discovery. This article provides the primary objectives of the analysis within pyrimidine centered new heterocyclic elements chronologically from their finding focusing on one of the essential enzyme of HIV virus particle that is integrase upon suppressing its strand transfer function. The class of compounds reviewed here includes bicyclic pyrimidines, dihydroxypyrimidines, pyrimidine-2,4-dinones, N-methylpyrimidones, pyranopyrimidine, pyridine-quinoline conjugates, pyrimidine-2-carboxamides, N-3 hydroxylated pyrimidine-2,4-diones as well as their various substituted analogues. Such initiatives released an effective drug Raltegravir as a first FDA approved anti-HIV integrase inhibitor as well as several of its derivatives along with other pyrimidones is under clinical or preclinical growth. Some of the provided scaffolds indicated dual anti-HIV efficacies against HIV reverse transcriptase and integrase enzymes at both cites as 3'-processing and strand transfer, while several scaffolds exhibited potency against Raltegravir resistant HIV mutant strains determining themselves a potent class of compounds having appealing upcoming implementations. Connections of the new compounds' molecular structure and HIV viral target has been overviewed to be able to accomplish further growth of promising anti-HIV agents in future drug discovery process.

Development of a receptor model for efficient in silico screening of HIV-1 integrase inhibitors

Integrase (IN) is a key viral enzyme for the replication of the type-1 human immunodeficiency virus (HIV-1), and as such constitutes a relevant therapeutic target for the development of anti-HIV agents. However, the lack of crystallographic data of HIV IN complexed with the corresponding viral DNA has historically hindered the application of modern structure-based drug design techniques to the discovery of new potent IN inhibitors (INIs). Consequently, the development and validation of reliable HIV IN structural models that may be useful for the screening of large databases of chemical compounds is of particular interest. In this study, four HIV-1 IN homology models were evaluated respect to their capability to predict the inhibition potency of a training set comprising 36 previously reported INIs with IC50 values in the low nanomolar to the high micromolar range. Also, 9 inactive structurally related compounds were included in this training set. In addition, a crystallographic structure of the IN-DNA complex corresponding to the prototype foamy virus (PFV) was also evaluated as structural model for the screening of inhibitors. The applicability of high throughput screening techniques, such as blind and ligand-guided exhaustive rigid docking was assessed. The receptor models were also refined by molecular dynamics and clustering techniques to assess protein sidechain flexibility and solvent effect on inhibitor binding. Among the studied models, we conclude that the one derived from the X-ray structure of the PFV integrase exhibited the best performance to rank the potencies of the compounds in the training set, with the predictive power being further improved by explicitly modeling five water molecules within the catalytic side of IN. Also, accounting for protein sidechain flexibility enhanced the prediction of inhibition potencies among the studied compounds. Finally, an interaction fingerprint pattern was established for the fast identification of potent IN inhibitors. In conclusion, we report an exhaustively validated receptor model if IN that is useful for the efficient screening of large chemical compounds databases in the search of potent HIV-1 IN inhibitors.

VN/14-1 induces ER stress and autophagy in HP-LTLC human breast cancer cells and has excellent oral pharmacokinetic profile in female Sprague Dawley rats

Resistance to aromatase inhibitors is a major concern in the treatment of breast cancer. Long-term letrozole cultured (LTLC) cells represent a model of resistance to aromatase inhibitors. The LTLC cells were earlier generated by culturing MCF-7Ca, the MCF-7 human breast cancer cell line stably transfected with human placental aromatase gene for a prolonged period in the presence of letrozole. In the present study the effect of RAMBA, VN/14-1 on the sensitivity of LTLC cells upon multiple passaging and the mechanisms of action of VN/14-1 in such high passage LTLC (HP-LTLC) cells was investigated. We report that multiple passaging of LTLC cells (HP-LTLC cell clones) led to profound decrease in their sensitivity to VN/14-1. Additionally, microarray studies and protein analysis revealed that VN/14-1 induced marked endoplasmic reticulum (ER) stress and autophagy in HP-LTLC cells. We further report that VN/14-1 in combination with thapsigargin exhibited synergistic anti-cancer effect in HP-LTLC cells. Preliminary pharmacokinetics in rats revealed that VN/14-1 reached a peak plasma concentration (Cmax) within 0.17h after oral dosing. Its absolute oral bioavailability was >100%. Overall these results indicate potential of VN/14-1 for further clinical development as a potential oral agent for the treatment of breast cancer.

Molecular features related to HIV integrase inhibition obtained from structure- and ligand-based approaches

Among several biological targets to treat AIDS, HIV integrase is a promising enzyme that can be employed to develop new anti-HIV agents. The aim of this work is to propose a mechanistic interpretation of HIV-1 integrase inhibition and to rationalize the molecular features related to the binding affinity of studied ligands. A set of 79 HIV-1 integrase inhibitors and its relationship with biological activity are investigated employing 2D and 3D QSAR models, docking analysis and DFT studies. Analyses of docking poses and frontier molecular orbitals revealed important features on the main ligand-receptor interactions. 2D and 3D models presenting good internal consistency, predictive power and stability were obtained in all cases. Significant correlation coefficients (r(2) = 0.908 and q(2)= 0.643 for 2D model; r(2)= 0.904 and q(2)= 0.719 for 3D model) were obtained, indicating the potential of these models for untested compounds. The generated holograms and contribution maps revealed important molecular requirements to HIV-1 IN inhibition and several evidences for molecular modifications. The final models along with information resulting from molecular orbitals, 2D contribution and 3D contour maps should be useful in the design of new inhibitors with increased potency and selectivity within the chemical diversity of the data.

Design and synthesis of novel pyrimidone analogues as HIV-1 integrase inhibitors

A series of novel pyrimidone analogues have been designed and synthesized as HIV-1 integrase (IN) inhibitors. This study demonstrated that introducing a substituent in the N1-position of the pyrimidone scaffold does not significantly influence IN inhibitory activity. Molecular docking studies showed these compounds could occupy the IN active site and form pi-pi interactions with viral DNA nucleotides DC16 and DA17 to displace reactive viral DNA 3'OH and block intasome activity.

Synthesis and biological activity of bimorpholine and its carbanucleoside

A new enantiomerically pure carbacyclic nucleoside analogue with bimorpholine as a nonaromatic nucleobase was synthesized. The nucleoside analogue and bimorpholine were tested for cytotoxicity using an MTT assay and the xCELLigence System. Both assays revealed that compound 3 was highly cytotoxic at a 50 μM concentration while the cytotoxic effect of compound 1 was much less prominent. No antiretroviral activity was detected for this compound. In contrast, it acted as a potent inhibitor of hepatitis C virus (HCV) replication. Most likely this effect originates largely from the cytotoxicity of the compound; however, it is possible that a specific mechanism of HCV inhibition also exists.

Pharmacophore modelling and atom-based 3D-QSAR studies on N-methyl pyrimidones as HIV-1 integrase inhibitors

Pharmacophore modelling and atom-based 3D-QSAR studies were carried out for a series of compounds belonging to N-methyl pyrimidones as HIV-1 integrase inhibitors. Based on the ligand-based pharmacophore model, we got 5-point pharmacophore model AADDR, with two hydrogen bond acceptors (A), two hydrogen bond donors (D) and one aromatic ring (R). The generated pharmacophore-based alignment was used to derive a predictive atom-based 3D-QSAR model for the training set (r(2) = 0.92, SD = 0.16, F = 84.8, N = 40) and for test set (Q(2) = 0.71, RMSE = 0.06, Pearson R = 0.90, N = 10). From these results, AADDR pharmacophore feature was selected as best common pharmacophore hypothesis, and atom-based 3D-QSAR results also support the outcome by means of favourable and unfavourable regions of hydrophobic and electron-withdrawing groups for the most potent compound 30. These results can be useful for further design of new and potent HIV-1 IN inhibitors.

Pharmacophore development and docking studies of the hiv-1 integrase inhibitors derived from N-methylpyrimidones, Dihydroxypyrimidines, and bicyclic pyrimidinones

To elucidate the crucial structural features for the HIV-1 integrase inhibitors, a three-dimensional pharmacophore model was developed based on N-methyl pyrimidones, dihydroxypyrimidines, and bicyclic pyrimidinones derivatives using Phase. N-methyl pyrimidone derivative raltegravir, the first US-FDA approved drug by Merck, belongs to this series. The best-fitted common pharmacophore hypothesis was characterized by two acceptor, two hydrophobic, and two ring features having a correlation coefficient of 0.895, cross-validated Q(2) value of 0.631, and survival score of 8.862, suggesting that a highly predictive pharmacophore model was developed. The cross-validation studies using 23 test set molecules and fifteen structurally diverse HIV-integrase inhibitors give extra confidence about the correctness of the pharmacophore model. The cross-validation studies proved that our developed model can successfully differentiate between active and inactive HIV-integrase inhibitors. The docking studies were also carried out wherein the molecules were docked against the active site of HIV integrase to analyze the binding mode and the necessary structural requirement for their respective enzymatic inhibition. The results obtained from our studies provide a valuable tool for designing of new lead molecules with potent activity.

Consensus ranking approach to understanding the underlying mechanism with QSAR

Constructing a highly predictive model and exploiting the underlying mechanism associated with a specific property of chemicals are the two main goals of quantitative structure-activity relationship analysis (QSAR). However, the latter has long been carried out as a byproduct of model construction. Here we confirmed for the first time in this study that conventional descriptor selection methods designed to develop a best predictive model are likely not suitable for mechanistic analysis, i.e., the selected descriptors strongly depended on the selection of chemicals in the training sets. As an alternative, a consensus ranking protocol was proposed to select a robust descriptor set for mechanistic analysis, which can successfully overcome the above shortcoming. Moreover, the consistently inferior model performance using descriptors selected for mechanistic analysis suggested the irreplaceable role of model development in achieving models with the best predictive capability.

Total synthesis and stereochemical reassignment of bisebromoamide

A revised configurational assignment for the thiazoline moiety of the marine peptide bisebromoamide is proposed and validated by total synthesis.

Evaluation of HIV-1 integrase inhibitors on human primary macrophages using a luciferase-based single-cycle phenotypic assay

Macrophages represent an important site for productive infection of HIV-1 and the evaluation of integrase (IN) inhibitors on this cell subset is of fundamental importance. In this report, preclinical evaluation of IN inhibitors on primary human macrophages was attempted successfully using a 96-well microtiter phenotypic assay developed recently for the evaluation of IN inhibitors in a cell-based system by taking advantage of HIV-derived lentiviral vectors expressing luciferase. IN inhibitors were also tested using a lentiviral vector containing an IN with introduced T66I/S153Y mutations, known to affect the activity of azido-group-containing diketo acid (DKA) IN inhibitors. Utilizing different classes of HIV integrase inhibitors against the wild-type IN and the mutant mentioned above, some of the IN inhibitors used were also active on this particular mutant, suggesting that should HIV-1 develop additional or different mutations to become resistant to such anti-IN drugs, new drugs can be developed with a better resistance profile. This assay provides a standardized method for the preclinical evaluation of the efficacy of IN inhibitors on wild-type and mutated IN that can be adapted easily for the evaluation of anti-IN activity on IN sequences derived from patients.

Examination of halogen substituent effects on HIV-1 integrase inhibitors derived from 2,3-dihydro-6,7-dihydroxy-1H-isoindol-1-ones and 4,5-dihydroxy-1H-isoindole-1,3(2H)-diones

Using 2,3-dihydro-6,7-dihydroxy-1H-isoindol-1-one and 4,5-dihydroxy-1H-isoindole-1,3(2H)-dione based HIV-1 integrase inhibitors as display platforms, we undertook a thorough examination of the effects of modifying the halogen substituents on a key benzyl ring that is hypothesized to bind in a hydrophobic pocket of the integrase.DNA complex. Data from this study suggest that in general dihalo-substituted analogues have higher potency than monohalo-substituted compounds, but that further addition of halogens is not beneficial.

Raltegravir, elvitegravir, and metoogravir: the birth of "me-too" HIV-1 integrase inhibitors

Merck's MK-0518, known as raltegravir, has recently become the first FDA-approved HIV-1 integrase (IN) inhibitor and has since risen to blockbuster drug status. Much research has in turn been conducted over the last few years aimed at recreating but optimizing the compound's interactions with the protein. Resulting me-too drugs have shown favorable pharmacokinetic properties and appear drug-like but, as expected, most have a highly similar interaction with IN to that of raltegravir. We propose that, based upon conclusions drawn from our docking studies illustrated herein, most of these me-too MK-0518 analogues may experience a low success rate against raltegravir-resistant HIV strains. As HIV has a very high mutational competence, the development of drugs with new mechanisms of inhibitory action and/or new active substituents may be a more successful route to take in the development of second- and third-generation IN inhibitors.