Non-nucleoside reverse transcriptase inhibitors: the NNRTI boom

Nucleoside and non-nucleoside reverse transcriptase inhibitor drugs (NRTIs and NNRTIs) are capable of binding Chandipura virus polymerase protein (L) and inhibit virus replication

Chandipura virus (CHPV) is an emerging pathogen of Indian subcontinent. It is a vector borne virus and belongs to Rhabdovirus family. In recent past several outbreaks reported from the states of "Maharastha", "Gujrat", "Andra Pradesh" causing more than 300 deaths of children below 15 years and case-fatality rate was more than 50%. There is no targeted drug or vaccine available against CHPV and symptomatic treatment is the option. We hypothesized that nucleoside and non-nucleoside reverse transcriptase inhibitor drugs will be able to inhibit CHPV replication because of close structural similarity of the viral polymerases within the finger, palm and thumb domains. We examined the inhibitory effects of NRTI drugs AZT, tenofovir, abacavir and NNRTI drug nevirapine on CHPV replication in Vero cells. We have performed plaque assays and western blotting to determine the levels of inhibition of virus replication. We found significant inhibition of CHPV by all these 4 drugs in the order abacavir > nevirapine > tenofovir > AZT. To gain an insight into drug mediated inhibition, we performed docking and molecular modelling of CHPV polymerase protein L bound to these drugs. Detailed methodology and a part of these results have been published in a preprint server (BioRxiv, 2022, doi: https://doi.org/10.1101/2022.03.02.482698). We summarize that abacavir, tenofovir, AZT and nevirapine are effective inhibitors of CHPV and a combination therapy may be designed to treat the disease.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13337-024-00883-w.

Synthesis, in vitro Anti-HIV-1RT evaluation, molecular modeling, DFT and acute oral toxicity studies of some benzotriazole derivatives

This study synthesized and evaluated a series of benzotriazole derivatives denoted 3(a-j) and 6(a-j) for their anti-HIV-1 RT activities compared to the standard drug efavirenz. Notably, compound 3 h, followed closely by 6 h, exhibited significant anti-HIV-1 RT efficacy relative to the standard drug. In vivo oral toxicity studies were conducted for the most active compound 3 h, confirming its nontoxic nature to ascertain the safety profile. By employing molecular docking techniques, we explored the potential interactions between the synthesized compounds (ligands) and a target biomolecule (protein)(PDB ID 1RT2) at the molecular level. We undertook the molecular dynamics study of 3 h, the most active compound, within the active binding pocket of the cocrystallized structure of HIV-1 RT (PDB ID 1RT2). We aimed to learn more about how biomolecular systems behave, interact, and change at the atomic or molecular level over time. Finally, the DFT-derived HOMO and LUMO orbitals, as well as analysis of the molecular electrostatic potential map, aid in discerning the reactivity characteristics of our molecule.

Identification of a Non-Nucleoside Reverse Transcriptase Inhibitor against Human Immunodeficiency Virus-1

The HIV-1 infection epidemic remains a global health problem. Current antiretroviral treatments are effective in controlling the progression of a severe infection. However, the emergence of drug resistance requires an urgent identification of new treatment regimes. HIV-1 reverse transcriptase (RTs) has been a successful therapeutic target owing to its high specificity and potent antiviral properties; therefore, it has become an essential component of current HIV-1 standard treatments. This study identified a new HIV-1 RTs inhibitor (Compound #8) that is structurally unique and greatly effective against HIV-1 through chemical library screening and a medicinal chemistry program by analyzing the structure-activity relationship (SAR). Further analysis of molecular docking and mechanisms of action demonstrated that Compound #8 is a novel type of HIV-1 non-nucleoside reverse transcriptase inhibitor (NNRTI) with a flexible binding mode. Therefore, it exhibits great therapeutic potential when combined with other existing HIV-1 drugs. Our current studies suggest that Compound #8 is a promising novel scaffold for the development of new HIV-1 treatments.

A General Method for the Synthesis of 11H-Indeno[1,2-B]Quinoxalin- 11-Ones and 6H-Indeno[1,2-B]Pyrido[3,2-E]Pyrazin-6-One Derivatives Using Mandelic Acid as an Efficient Organo-Catalyst at Room Temperature

Aims:

Synthesis of 11H-indeno[1,2-b]quinoxalin-11-ones as well as 6H-indeno[1,2-b]pyrido[3,2-e]pyrazin-6-one derivatives under greener conditions.

Background:

Quinoxaline and related skeletons are very common in naturally occurring bioactive compounds.

Objective:

Design a facile, green and organo-catalyzed method for the synthesis of 11H-indeno[1,2-b]quinoxalin-11-ones as well as 6H-indeno[1,2-b]pyrido[3,2-e]pyrazin-6-one derivatives.

Methods:

Both the scaffolds were synthesized via the condensation of ninhydrin and o-phenylenediamines or pyridine-2,3-diamines respectively by using a catalytic amount of mandelic acid as an efficient, commercially available, low cost, organo-catalyst in aqueous ethanol at room temperature.

Results:

Mild reaction conditions, use of metal-free organocatalyst, non-toxic solvent, ambient temperature, and no column chromatographic separation are some of the notable advantages of our developed protocol.

Conclusion:

In conclusion, we have developed a simple, mild, facile and efficient method for the synthesis of structurally diverse 11H-indeno[1,2-b]quinoxalin-11-one derivatives via the condensation reactions of ninhydrin and various substituted benzene-1,2-diamines using a catalytic amount of mandelic acid as a commercially available metal-free organo-catalyst in aqueous ethanol at room temperature. Under the same optimized reaction conditions, synthesis of 6H-indeno[1,2-b]pyrido[3,2-e]pyrazin-6-one derivatives was also accomplished with excellent yields by using pyridine-2,3-diamines instead of o-phenylenediamine.

Non-Nucleotide RNA-Dependent RNA Polymerase Inhibitor That Blocks SARS-CoV-2 Replication

SARS-CoV-2 has caused an extensive pandemic of COVID-19 all around the world. Key viral enzymes are suitable molecular targets for the development of new antivirals against SARS-CoV-2 which could represent potential treatments of the corresponding disease. With respect to its essential role in the replication of viral RNA, RNA-dependent RNA polymerase (RdRp) is one of the prime targets. HeE1-2Tyr and related derivatives were originally discovered as inhibitors of the RdRp of flaviviruses. Here, we present that these pyridobenzothiazole derivatives also significantly inhibit SARS-CoV-2 RdRp, as demonstrated using both polymerase- and cell-based antiviral assays.

Synthesis and Characterization of New Fluoro/Trifluoromethyl-Substituted Acylthiourea Derivatives with Promising Activity against Planktonic and Biofilm-Embedded Microbial Cells

The aim of this study was preparation of new derivatives based on 2-((4-chlorophenoxy)methyl)-N-(arylcarbamothioyl)benzamide structure; the new compounds were characterized by IR, NMR (1H, 13C) spectroscopy, and elemental analysis. The obtained compounds were evaluated for their in vitro antimicrobial activity against planktonic and biofilm-embedded microbial cells (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Candida albicans), by qualitative and quantitative assays. Some of the compounds revealed promising antibacterial and antifungal activities, with low minimum inhibitory concentration values between 0.15 and 2.5 mg/mL and minimal biofilm eradication concentrations of 0.019–2.5 mg/mL. To investigate the potential target of their antibacterial activity, in silico drug-likeness and molecular docking screenings on Staphylococcus aureus DNA gyrase were performed. The compound with the best antibacterial activity (1g) was docked into topoisomerase II DNA gyrase enzymes (PDB ID: 2XCS) and showed valuable interactions with the target protein along with good docking scores, suggesting that it can act by the inhibition of DNA replication. The tested compounds exhibited only a poor antioxidant activity, as revealed by the in vitro assay using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay.

Synthesis of New Quinazoline-2,4(1H,3H)-dione non-nucleoside Analogues of the reverse transcriptase inhibitor TNK-651

The synthesis is described of a series of new non-nucleoside analogues of the reverse transcriptase inhibitor TNK-651 from quinazoline-2,4(1 H,3 H)-diones. Compounds 2a–c were silylated and treated with benzyl chloromethyl ether in the presence of CsI to give 1-benzyloxymethylquinazoline derivatives 3a–c. Treatment of the silylated quinazolinediones 2a–c with the appropriate acetals 5a–e in the presence of TMS triflate afforded the corresponding TNK-651 analogues 6–10.

Copper and Antibiotics: Discovery, Modes of Action, and Opportunities for Medicinal Applications

Copper is a ubiquitous element in the environment as well as living organisms, with its redox capabilities and complexation potential making it indispensable for many cellular functions. However, these same properties can be highly detrimental to prokaryotes and eukaryotes when not properly controlled, damaging many biomolecules including DNA, lipids, and proteins. To restrict free copper concentrations, all bacteria have developed mechanisms of resistance, sequestering and effluxing labile copper to minimize its deleterious effects. This weakness is actively exploited by phagocytes, which utilize a copper burst to destroy pathogens. Though administration of free copper is an unreasonable therapeutic antimicrobial itself, due to insufficient selectivity between host and pathogen, small-molecule ligands may provide an opportunity for therapeutic mimicry of the immune system. By modulating cellular entry, complex stability, resistance evasion, and target selectivity, ligand/metal coordination complexes can synergistically result in high levels of antibacterial activity. Several established therapeutic drugs, such as disulfiram and pyrithione, display remarkable copper-dependent inhibitory activity. These findings have led to development of new drug discovery techniques, using copper ions as the focal point. High-throughput screens for copper-dependent inhibitors against Mycobacterium tuberculosis and Staphylococcus aureus uncovered several new compounds, including a new class of inhibitors, the NNSNs. In this review, we highlight the microbial biology of copper, its antibacterial activities, and mechanisms to discover new inhibitors that synergize with copper.

Depolarization of mitochondrial membrane potential is the initial event in non-nucleoside reverse transcriptase inhibitor efavirenz induced cytotoxicity

Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI) and an active constituent of the highly active antiretroviral therapy regime. It has significantly contributed in control and management of human immunodeficiency virus propagation. However, EFV administration has also led to severe adverse effects, several reports highlighted the role of EFV in mitochondrial dysfunction and toxicity but the molecular mechanism has been poorly understood. In present study, human hepatoma cells Huh 7.5 were treated with clinically relevant concentrations of EFV and parameters like cytotoxicity, mitochondrial transmembrane potential, mitochondrial morphology, cytochrome c release, mitochondria-mediated apoptosis, mtDNA and mtRNA levels and EFV distribution into mitochondrial compartment were evaluated to understand sequence of events leading to cell death in EFV-treated cells. EFV at its clinically relevant concentration was significantly toxic after 48 and 72 h of treatments. EFV-mediated toxicity is initiated with the permeabilization of mitochondrial outer membrane and change in mitochondrial membrane potential (Δψm) which triggers a series of events like cytochrome c release, alteration in mitochondrial morphology and mitochondria-mediated apoptosis. Total mitochondrial content is reduced after 48 h of EFV treatment at IC₅₀ concentration which is also reflected in reduced mitochondrial DNA and RNA levels. After detecting EFV in mitochondrial compartment after 12 h of incubation with EFV, we hypothesize that EFV being a lipophilic molecule is internalized into the mitochondrial compartment causing depolarization of Δψm which subsequently leads to a cascade of events causing cell death.

Clinical Utility of Current NNRTIs and Perspectives of New Agents in This Class under Development

Highly active antiretroviral therapy (HAART) has significantly reduced the number of deaths caused by AIDS. However, the antiviral efficacy of HAART comprising protease inhibitors (PIs) and nucleoside reverse transcriptase inhibitors (NRTIs) is frequently accompanied by a decrease in patients' quality of life. PI-based therapies often fail due to poor adherence caused by heavy pill burden, complex dosing schedules and undesirable side effects. The current trend is to switch from PI-based to PI-sparing regimens consisting of non-nucleoside reverse transcriptase inhibitors (NNRTIs) and NRTIs. Despite some encouraging results from NNRTI-containing therapies, two major concerns in using the currently available NNRTIs remain: 1) low genetic barrier to the emergence of resistance and 2) cross-resistance due to single mutations that often render the whole class of NNRTIs ineffective. Clearly, new and improved NNRTIs are needed to address these concerns.

Structure-Activity Relationship Studies on a Novel Family of Specific HIV-1 Reverse Transcriptase Inhibitors

We have previously reported the discovery and preliminary structure-activity relationships of a new class of specific HIV-1 reverse transcriptase (RT) inhibitors whose prototype compound is the 1-[2′,5′-bis- O-( tert-butyldimethylsilyl)-β-D-ribofuranosyl]-3- N-[(carboxy) methyl]-thymine. In an attempt to increase the inhibitory efficacy against HIV-1 RT of this new class of nucleosides, and to further explore the structural features required for anti-HIV-1 activity, different types of modifications have been carried out on the prototype compound. These include substitution of the tert-butyldimethylsilyl groups by other liphophilic groups, replacement of the carboxy group at the N-3 position of the nucleobase by other functional groups, change in the length of the spacer between the thymine and the carboxylic acid residue and substitution of the thymine moiety by other pyrimidine (uracil, 5-ethyluracil) or purine (hypoxanthine) nucleobases. In addition, the most salient structural features of this new class of HIV-1-specific nucleosides have been incorporated into classical HIV RT nucleoside inhibitors such as ddI, AZT, d4T. Our studies demonstrate that both the carboxymethyl moiety at the nucleobase and tert-butyldimethylsilyl groups at the sugar are important structural components since deletion of either of them is detrimental to the antiviral activity.

Design, synthesis, and anti-HIV-1 activity of 1-aromatic methyl-substituted 3-(3,5-dimethylbenzyl)uracil and N-3,5-dimethylbenzyl-substituted urea derivatives

BACKGROUND

A new series of 1-aromatic methyl-substituted 3-(3,5-dimethylbenzyl)uracil and N-3,5-dimethylbenzyl-substituted urea derivatives were synthesized and evaluated as non-nucleoside HIV-1 reverse transcriptase inhibitors.

METHODS

A series of new 6-azido and 6-amino derivatives of 1-substituted-3-(3,5-dimethylbenzyl)uracils were synthesized using our previously reported method, and three acyclic derivatives were synthesized from urea. The anti-HIV-1 activities of these compounds were determined based on the inhibition of virus-induced cytopathogenicity in MT-4 cells. The cytotoxicities of the compounds were evaluated using the viability of mock-infected cells.

RESULTS

Some of these compounds showed good-to-moderate activities against HIV-1 with half maximal effective concentration (EC50) values in the submicromolar or subnanomolar range. Compared with emivirine, compound 6-amino-3-(3,5-dimethylbenzyl)-1-(4-aminobenzyl)uracil showed significant anti-HIV-1 activity with an EC50 value of 10 nM and a high selectivity index of 1923. Preliminary structure-activity relationship studies and molecular modeling analyses were carried out to explore the major interactions between HIV-1 reverse transcriptase and the potent inhibitor 6-amino-3-(3,5-dimethylbenzyl)-1-(4-aminobenzyl)uracil; these results may be important for further development of this class of compounds as anti-HIV-1 agents.

CONCLUSION

The excellent activity of 6-amino-3-(3,5-dimethylbenzyl)-1-(4-aminobenzyl)uracil (EC50: 0.010 ± 0.006 µM, SI: >1923) may serve as the basis for conducting further investigations on the behavior of this class of compounds against drug-resistant mutants.

Anti-HIV cytotoxicity enzyme inhibition and molecular docking studies of quinoline based chalcones as potential non-nucleoside reverse transcriptase inhibitors (NNRT)

A series of fourteen (A1 - A14) qunioline based chalcones were screened for reverse transcriptase inhibitors (RT) and found potentially active against RT. Bioassay, theoretical and dockings studies with RT (the enzyme required for reverse transcription of viral RNA) results showed that the type and positions of the substituents seemed to be critical for their inhibition against RT. The bromo and chloro substituted chalcone displayed high degree of inhibition against RT. The A4 andA6 showed high interaction with RT, contributing high free binding energy (ΔG -9.30 and -9.13kcal) and RT inhibition value (IC50 0.10μg/ml and 0.11μg/ml).

Focus on Chirality of HIV-1 Non-Nucleoside Reverse Transcriptase Inhibitors

Chiral HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs) are of great interest since one enantiomer is often more potent than the corresponding counterpart against the HIV-1 wild type (WT) and the HIV-1 drug resistant mutant strains. This review exemplifies the various studies made to investigate the effect of chirality on the antiretroviral activity of top HIV-1 NNRTI compounds, such as nevirapine (NVP), efavirenz (EFV), alkynyl- and alkenylquinazolinone DuPont compounds (DPC), diarylpyrimidine (DAPY), dihydroalkyloxybenzyloxopyrimidine (DABO), phenethylthiazolylthiourea (PETT), indolylarylsulfone (IAS), arylphosphoindole (API) and trifluoromethylated indole (TFMI) The chiral separation, the enantiosynthesis, along with the biological properties of these HIV-1 NNRTIs, are discussed.

Antiviral Drugs

Viruses are major pathogenic agents causing a variety of serious diseases in humans, other animals, and plants.

Drugs that combat viral infections are called antiviral drugs. There are no effective antiviral drugs for many viral infections. However, there are several drugs for influenza, a couple of drugs for herpesviruses, and some new antiviral drugs for treatment of HIV and hepatitis C infections.

The arsenal of antivirals is complex. As of March 2014, it consists of approximately 50 drugs approved by the FDA, approximately half of which are directed against HIV. Antiviral drug creation strategies are focused on two different approaches: targeting the viruses themselves or targeting host cell factors.

Direct virus-targeting antiviral drugs include attachment inhibitors, entry inhibitors, uncoating inhibitors, protease inhibitors, polymerase inhibitors, nucleoside and nucleotide reverse transcriptase inhibitors, nonnucleoside reverse-transcriptase inhibitors, and integrase inhibitors.

Protease inhibitors (darunavir, atazanavir, and ritonavir), viral DNA polymerase inhibitors (acyclovir, valacyclovir, valganciclovir, and tenofovir), and an integrase inhibitor (raltegravir) are included in the list of Top 200 Drugs by sales for the 2010s.

Efavirenz Has the Highest Anti-Proliferative Effect of Non-Nucleoside Reverse Transcriptase Inhibitors against Pancreatic Cancer Cells

Background

Cancer prevention and therapy in HIV-1-infected patients will play an important role in future. The non-nucleoside reverse transcriptase inhibitors (NNRTI) Efavirenz and Nevirapine are cytotoxic against cancer cells in vitro. As other NNRTIs have not been studied so far, all clinically used NNRTIs were tested and the in vitro toxic concentrations were compared to drug levels in patients to predict possible anti-cancer effects in vivo.

Methods

Cytotoxicity was studied by Annexin-V-APC/7AAD staining and flow cytometry in the pancreatic cancer cell lines BxPC-3 and Panc-1 and confirmed by colony formation assays. The 50% effective cytotoxic concentrations (EC50) were calculated and compared to the blood levels in our patients and published data.

Results

The in vitro EC50 of the different drugs in the BxPC-3 pancreatic cancer cells were: Efavirenz 31.5μmol/l (= 9944ng/ml), Nevirapine 239μmol/l (= 63786ng/ml), Etravirine 89.0μmol/l (= 38740ng/ml), Lersivirine 543μmol/l (= 168523ng/ml), Delavirdine 171μmol/l (= 78072ng/ml), Rilpivirine 24.4μmol/l (= 8941ng/ml). As Efavirenz and Rilpivirine had the highest cytotoxic potential and Nevirapine is frequently used in HIV-1 positive patients, the results of these three drugs were further studied in Panc-1 pancreatic cancer cells and confirmed with colony formation assays. 205 patient blood levels of Efavirenz, 127 of Rilpivirine and 31 of Nevirapine were analyzed. The mean blood level of Efavirenz was 3587ng/ml (range 162–15363ng/ml), of Rilpivirine 144ng/ml (range 0-572ng/ml) and of Nevirapine 4955ng/ml (range 1856–8697ng/ml). Blood levels from our patients and from published data had comparable Efavirenz levels to the in vitro toxic EC50 in about 1 to 5% of all patients.

Conclusion

All studied NNRTIs were toxic against cancer cells. A low percentage of patients taking Efavirenz reached in vitro cytotoxic blood levels. It can be speculated that in HIV-1 positive patients having high Efavirenz blood levels pancreatic cancer incidence might be reduced. Efavirenz might be a new option in the treatment of cancer.

Synthesis and biological evaluation of 2-thioxopyrimidin-4(1H)-one derivatives as potential non-nucleoside HIV-1 reverse transcriptase inhibitors

A series of new 5-allyl-6-benzylpyrimidin-4(3H)-ones bearing different substituents at the C-2 position of the pyrimidine core have been synthesized and evaluated for their in vitro activities against human immunodeficiency virus type 1 (HIV-1) in the human T-lymphotropic type (MT-4 cell cultures). The majority of the title compounds showed moderate to good activities against HIV-1. Amongst them, 5-allyl-6-benzyl-2-(3-hydroxypropylthio)pyrimidin-4(3H)-one analogue 11c exhibited the most potent anti-HIV-1 activity (IC₅₀ 0.32 µM). The biological testing results clearly indicated that the substitution at C-2 position of the pyrimidine ring could increase the anti-HIV-1 reverse transcriptase (RT) activity.

Dual role of novel ingenol derivatives from Euphorbia tirucalli in HIV replication: inhibition of de novo infection and activation of viral LTR

HIV infection is not cleared by antiretroviral drugs due to the presence of latently infected cells that are not eliminated with current therapies and persist in the blood and organs of infected patients. New compounds to activate these latent reservoirs have been evaluated so that, along with HAART, they can be used to activate latent virus and eliminate the latently infected cells resulting in eradication of viral infection. Here we describe three novel diterpenes isolated from the sap of Euphorbia tirucalli, a tropical shrub. These molecules, identified as ingenols, were modified at carbon 3 and termed ingenol synthetic derivatives (ISD). They activated the HIV-LTR in reporter cell lines and human PBMCs with latent virus in concentrations as low as 10 nM. ISDs were also able to inhibit the replication of HIV-1 subtype B and C in MT-4 cells and human PBMCs at concentrations of EC₅₀ 0.02 and 0.09 µM respectively, which are comparable to the EC₅₀ of some antiretroviral currently used in AIDS treatment. Control of viral replication may be caused by downregulation of surface CD4, CCR5 and CXCR4 observed after ISD treatment in vitro. These compounds appear to be less cytotoxic than other diterpenes such as PMA and prostratin, with effective dose versus toxic dose TI>400. Although the mechanisms of action of the three ISDs are primarily attributed to the PKC pathway, downregulation of surface receptors and stimulation of the viral LTR might be differentially modulated by different PKC isoforms.

Efavirenz stimulates HIV-1 reverse transcriptase RNase H activity by a mechanism involving increased substrate binding and secondary cleavage activity

Efavirenz is a non-nucleoside reverse transcriptase inhibitor used for treating HIV/AIDS. We found that polymerization activity of a reverse transcriptase (RT) with the E478Q mutation that inactivates the RNase H catalytic site is much more sensitive to efavirenz than wild-type RT, indicating that a functional RNase H attenuates the effectiveness of efavirenz. Moreover, efavirenz actually stimulated wild-type RNase H binding and catalytic functions, indicating another link between efavirenz action and RNase H function. During reverse transcription in vivo, the RT that is extending the DNA primer also periodically cleaves the genomic RNA. The RNase H makes primary template cuts ~18 nucleotides from the growing DNA 3'-end, and when the RT pauses synthesis, it shifts to make secondary cuts ~9 nucleotides from the DNA 3'-end. After synthesis, RTs return to bind the remaining template RNA segments at their 5'-ends and make primary and secondary cuts, 18 and 9 nucleotides in, respectively. We found that efavirenz stimulates both 3'- and 5'-directed RNase H activity. Use of specific substrates revealed a particular acceleration of secondary cuts. Efavirenz specifically promoted binding of the RT to RNase H substrates, suggesting that it stabilizes the shifting of RTs to make the secondary cuts. We further showed that efavirenz similarly stimulates the RNase H of an RT from a patient-derived virus that is highly resistant and grows more rapidly in the presence of low concentrations of efavirenz. We suggest that for efavirenz-resistant RTs, stimulated RNase H activity contributes to increased viral fitness.

Nanorod-Shaped Basic Al2O3 Catalyzed N,N-Diformylation of Bisuracil Derivatives: A Greener "NOSE" Approach

A feasible “NOSE” (nanoparticles-catalyzed organic synthesis enhancement) protocol has been developed for N,N-diformylation of bisuracil derivatives using nano-Al₂O₃ rods as an efficient, inexpensive, and recyclable catalyst under solvent-free reaction condition at 40°C. The catalyst was reused up to the 4th cycle without affecting the rate and yield of the N,N-diformylation products appreciably.

Etravirine for the treatment of HIV/AIDS

INTRODUCTION

Etravirine (TMC125) is an orally administered second-generation non-nucleoside reverse transcriptase inhibitor (NNRTI) that is approved in treatment-experienced patients as addition to an optimized background therapy (OBT).

AREAS COVERED

A Medline search was conducted of Phase II - IV clinical trials, as well as a review of abstracts from major HIV and infectious disease conferences from 2010 - 2013, involving etravirine.

EXPERT OPINION

Etravirine is a well-tolerated NNRTI with a good safety profile and a higher genetic barrier for resistance compared to first-generation NNRTIs. Rash is a potential side effect but remains mostly mild to moderate. The necessity of taking it twice daily with food (200 mg bid.), potential pharmacokinetic interactions and low concentrations in the central nervous system (CNS) represent limitations. The efficacy of once daily etravirine (400 mg qid.) and the use in treatment modification/simplification strategies requires further research. Despite its favorable profile, etravirine is currently not sufficiently investigated nor approved for use in treatment-naïve patients which should be balanced against its potential as a backup NNRTI and the broad cross-resistance conferred by etravirine failure to other NNRTIs. Etravirine should be avoided following treatment failure with regimens containing rilpivirine, another second-generation NNRTI.

Synthesis and evaluation of novel 4-substituted styryl quinazolines as potential antimicrobial agents

In an attempt to afford possible antibacterial and anti-human immunodeficiency virus (HIV) agents, a series of 22 novel styryl quinazoline-based heterocyclic entities were designed and synthesized. Various substituted aryl urea and thiourea cores were incorporated at position 4 of quinazoline, followed by styrylation of position 2, aiming at an augmented biological potential. The synthesized compounds were well characterized through IR, (1) H NMR, (13) C NMR and elemental analyses. All compounds were screened for their in vitro anti-HIV activity against the HIV-1 (IIIB) and HIV-2 (ROD) strains. The antibacterial activity was also evaluated against various pathogenic Gram-positive and Gram-negative bacterial strains.

Molecular docking of (5E)-3-(2-aminoethyl)-5-(2- thienylmethylene)-1, 3-thiazolidine-2, 4-dione on HIV-1 reverse transcriptase: novel drug acting on enzyme

The study of Human immunodeficiency virus (HIV) in humans and animal models in last 31 years suggested that it is a causative agent of AIDS. This causes serious pandemic public health concern globally. It was reported that the HIV-1 reverse transcriptase (RT) played a critical role in the life cycle of HIV. Therefore, inhibition of HIV-1RT enzyme is one of the major and potential targets in the treatment of AIDS. The enzyme (HIV-1RT) was successfully targeted by non nucleotide reverse transcriptase inhibitors (NNRTIs). But frequent application of NNRTIs led drug resistance mutation on HIV infections. Therefore, there is a need to search new NNRTIs with appropriate pharmacophores. For the purpose, a virtually screened 3D model of unliganded HIV-1RT (1DLO) was explored. The unliganded HIV-1RT (1DLO) was docked with 4-thiazolidinone and its derivatives (ChemBank Database) by using AutoDock4. The best seven docking solutions complex were selected and analyzed by Ligplot. The analysis showed that derivative (5E)-3-(2- aminoethyl)-5-(2- thienylmethylene)-1, 3-thiazolidine-2, 4-dione (CID 3087795) has maximum potential against unliganded HIV-1RT (1DLO). The analysis was done on the basis of scoring and binding ability. The derivative (5E)-3-(2- aminoethyl)-5-(2- thienylmethylene)-1, 3-thiazolidine-2, 4-dione (CID 3087795) indicated minimum energy score and highest number of interactions with active site residue and could be a promising inhibitor for HIV-1 RT as Drug target.

Conformation depends on 4D-QSAR analysis using EC-GA method: pharmacophore identification and bioactivity prediction of TIBOs as non-nucleoside reverse transcriptase inhibitors

The electron conformational and genetic algorithm methods (EC-GA) were integrated for the identification of the pharmacophore group and predicting the anti HIV-1 activity of tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepinone (TIBO) derivatives. To reveal the pharmacophore group, each conformation of all compounds was arranged by electron conformational matrices of congruity. Multiple comparisons of these matrices, within given tolerances for high active and low active TIBO derivatives, allow the identification of the pharmacophore group that refers to the electron conformational submatrix of activity. The effects of conformations, internal and external validation were investigated by four different models based on an ensemble of conformers and a single conformer, both with and without a test set. Model 1 using an ensemble of conformers for the training (39 compounds) and test sets (13 compounds), obtained by the optimum seven parameters, gave satisfactory results (R²(training) = 0.878, R²(test)= 0.910, q² = 0.840, q²(ext1) = 0.926 and q²(ext2) = 0.900).

3,4,5-Trisubstituted-1,2,4-4H-triazoles as WT and Y188L mutant HIV-1 non-nucleoside reverse transcriptase inhibitors: docking-based CoMFA and CoMSIA analyses

3,4,5-Trisubstituted-1,2,4-4H-triazoles (TTs) have recently been identified as a new class of potent non-nucleoside HIV-1 reverse transcriptase (RT) inhibitors. Two series of triazoles have been studied, one of which was also screened against the Y188L mutant. A computational strategy based on molecular docking studies followed by comparative molecular fields analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) has been used to elucidate the atomic details of the RT/TT interactions and to identify the most important features impacting the TT antiretroviral activity. Two 3D-QSAR CoMFA and CoMSIA models were derived, using the TT pEC₅₀ values measured against wild-type (WT) HIV-1 (model A) and the Y188L mutant form (model B), respectively, as the dependent variable. The final model A CoMSIA (r(ncv)²  = 0.97, r(cv)²  = 0.89, SEE = 0.314, and r(pred)²  = 0.82) and model B CoMSIA (r(ncv)²  = 0.91, r(cv)²  = 0.61, SEE = 0.236, and r(pred)²  = 0.73) analyses were more predictive. The results allowed us to obtain useful information for the design of new compounds with improved potency towards WT HIV-1 or that are potentially active against the Y188L mutant.

Looking for an active conformation of the future HIV type-1 non-nucleoside reverse transcriptase inhibitors

HIV type-1 (HIV-1) non-nucleoside reverse transcriptase inhibitors (NNRTIs) are key drugs of highly active antiretroviral therapy (HAART) in the clinical management of AIDS/HIV infection. NNRTI-based HAART regimes effectively suppress viral reproduction, are not cytotoxic and show favourable pharmacokinetic properties. First-generation NNRTIs suffer the rapid selection of viral variants, hampering the binding of inhibitors into the reverse transcriptase (RT) non-nucleoside binding site (NNBS). Efforts to improve these first inhibitors led to the discovery of second-generation NNRTIs that proved to be effective against the drug-resistant mutant HIV-1 strains. The success of such agents launched a new season of NNRTI design and synthesis. This paper reviews the characteristics of second-generation NNRTIs, including etravirine, rilpivirine, RDEA-806, UK-453061, BIRL 355 BS, IDX 899, MK-4965 and HBY 097. In particular, the binding modes of these inhibitors into the NNBS of the HIV-1 RT and the most clinically relevant mutant RTs are analysed and discussed.

Synthesis of novel uracil non-nucleoside derivatives as potential reverse transcriptase inhibitors of HIV-1

Novel emivirine and TNK-651 analogues 5a-d were synthesized by reaction of chloromethyl ethyl ether and / or benzyl chloromethyl ether, respectively, with uracils having 5-ethyl and 6-(4-methylbenzyl) or 6-(3,4-dimethoxybenzyl) substituents. A series of new uracil non-nucleosides substituted at N-1 with cyclopropylmethyloxymethyl 9a-d, 2-phenylethyloxymethyl 9e-h, and 3-phenylprop-1-yloxymethyl 9i-l were prepared on treatment of the corresponding uracils with the appropriate acetals 8a-c. Some of the tested compounds showed good activity against HIV-1 wild type. Among them, 1-cyclopropylmethyloxymethyl-5-ethyl-6-(3,5-dimethylbenzyl)uracil 9c and 5-ethyl-6-(3,5-dimethylbenzyl)-1-(2-phenylethyloxymethyl)uracil 9g showed inhibitory potency equally to emivirine against HIV-1 wild type. Furthermore, compounds 9c and 9g showed marginal better activity against NNRTI resistant mutants than emivirine.

Novel tight binding PETT, HEPT and DABO-based non-nucleoside inhibitors of HIV-1 reverse transcriptase

Non-nucleoside reverse transcriptase (RT) inhibitors (NNRTIs) are a key component of effective combination antiretroviral therapies for HIV/AIDS. NNRTIs despite their chemical diversity, bind to a common allosteric site of HIV-1 RT, the primary target for anti-AIDS chemotherapy, and noncompetitively inhibit DNA polymerization. NNRTIs currently in clinical use have a low genetic barrier to resistance and therefore, the need for novel NNRTIs active against drug-resistant mutants selected by current therapies is of paramount importance. We describe the chemistry and biological evaluation of highly potent novel phenethylthiazolylthiourea (PETT), 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT) and dihydroalkoxybenzyloxopyrimidine (DABO) derivatives targeting the hydrophobic binding pocket of HIV-1 RT. These NNRTIs were rationally designed by molecular modeling and docking studies using a novel composite binding pocket that predicted how drug-resistant mutations would change the RT binding pocket shape, volume, and chemical make-up and how these changes could affect NNRTI binding. Several ligand derivatization sites were identified for docked NNRTIs that fit the composite binding pocket. The best fit was determined by calculating an inhibition constant (Ludi Ki) of the docked compound for the composite binding pocket. Compounds with a Ludi Ki of <1 microM were identified as the most promising tight binding NNRTIs. These NNRTIs displayed high selective indices with robust anti-HIV-1 activity against the wild-type and drug-resistant isolates carrying multiple RT gene mutations. The high rate of treatment failure due to the emergence of drug resistance mutations makes the discovery of broad-spectrum PETT, HEPT and DABO-based NNRTIs useful as a component of effective combination regimens.