Improving the positional adaptability: structure-based design of biphenyl-substituted diaryltriazines as novel non-nucleoside HIV-1 reverse transcriptase inhibitors

Structure-guided design of novel biphenyl-quinazoline derivatives as potent non-nucleoside reverse transcriptase inhibitors featuring improved anti-resistance, selectivity, and solubility

In pursuit of enhancing the anti-resistance efficacy and solubility of our previously identified NNRTI 1, a series of biphenyl-quinazoline derivatives were synthesized employing a structure-based drug design strategy. Noteworthy advancements in anti-resistance efficacy were discerned among some of these analogs, prominently exemplified by compound 7ag, which exhibited a remarkable 1.37 to 602.41-fold increase in potency against mutant strains (Y181C, L100I, Y188L, F227L + V106A, and K103N + Y181C) in comparison to compound 1. Compound 7ag also demonstrated comparable anti-HIV activity against both WT HIV and K103N, albeit with a marginal reduction in activity against E138K. Of significance, this analog showed augmented selectivity index (SI > 5368) relative to compound 1 (SI > 37764), Nevirapine (SI > 158), Efavirenz (SI > 269), and Etravirine (SI > 1519). Moreover, it displayed a significant enhancement in water solubility, surpassing that of compound 1, Etravirine, and Rilpivirine. To elucidate the underlying molecular mechanisms, molecular docking studies were undertaken to probe the critical interactions between 7ag and both WT and mutant strains of HIV-1 RT. These findings furnish invaluable insights driving further advancements in the development of DAPYs for HIV therapy.

Tri-substituted 1,3,5-triazine-based analogs as effective HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs): A systematic review

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) have significantly impacted the HIV-1 wild-type due to their high specificity and superior potency. As well as different combinations of NNRTIs have been used on clinically approved combining highly active antiretroviral therapy (HAART) to resist the growth of HIV-1 and decrease the mortality rate of HIV/AIDS. Although the feeble strength against the drug-resistant mutant strains and the long-term damaging effects have been reducing the effectiveness of HAART, it could be a crucial challenge to develop novel Anti-HIV leads with a vital mode of action and the least side effects. The extensive chemical reactivity and the diverse chemotherapeutic applications of the 1,3,5-triazine have provided a wide scope of research in medicinal chemistry via a structural modification. In this review, we focused on the Anti-HIV profile of the tri-substituted s-triazine derivatives with structure-based features and also discussed the active mode of action to evaluate the significant findings. The tri-substituted 1,3,5-triazine derivatives have been found more promising to inhibit the growth of the drug-sensitive and drug-resistant variants of HIV-1, especially HIV-1 wild-type, HIV-1 K103N/Y181C, and HIV-1 Tyr181Cys. It has been observed that these derivatives have interacted with the enzyme protein residues via a significantπ $\pi $ -π $\pi $ interaction and hydrogen bonding to resist the proliferation of the viral genomes. Further, the SAR and the active binding modes are critically described and highlight the role of structural variations with functional groups along with the binding affinity of targeted enzymes, which may be beneficial for rational drug discovery to develop highly dynamic Anti-HIV agents.

Fragment-Based Discovery of Azocyclic Alkyl Naphthalenesulfonamides as Keap1-Nrf2 Inhibitors for Acute Lung Injury Treatment

Blocking the Kelch-like epichlorohydrin-related protein 1 (Keap1)-nuclear factor-erythroid 2 related factor 2 (Nrf2) pathway is a promising strategy to alleviate acute lung injury (ALI). A naphthalensulfonamide NXPZ-2, targeting Keap1-Nrf2 interaction to release Nrf2, was confirmed to exhibit significant anti-inflammatory activities, however, accompanying nonideal solubility and PK profiles. To further improve the properties, twenty-nine novel naphthalenesulfonamide derivatives were designed by a fragment-based strategy. Among them, compound 10u with a (R)-azetidine group displayed the highest PPI inhibitory activity (K_D2 = 0.22 μM). The hydrochloric acid form of 10u exhibited a 9-fold improvement on water solubility (S = 484 μg/mL, pH = 7.0) compared to NXPZ-2 (S = 55 μg/mL, pH = 7.0). It could significantly reduce LPS-induced lung oxidative damages and inflammations in vitro and in vivo. Furthermore, a satisfactory pharmacokinetic property was revealed. In conclusion, the novel azetidine-containing naphthalenesulfonamide represents a promising drug candidate for Keap1-targeting ALI treatment.

Picomolar inhibitor of reverse transcriptase featuring significantly improved metabolic stability

Considering the undesirable metabolic stability of our recently identified NNRTI 5 (t_1/2 = 96 min) in human liver microsomes, we directed our efforts to improve its metabolic stability by introducing a new favorable hydroxymethyl side chain to the C-5 position of pyrimidine. This strategy provided a series of novel methylol-biphenyl-diarylpyrimidines with excellent anti-HIV-1 activity. The best compound 9g was endowed with remarkably improved metabolic stability in human liver microsomes (t_1/2 = 2754 min), which was about 29-fold longer than that of 5 (t_1/2 = 96 min). This compound conferred picomolar inhibition of WT HIV-1 (EC₅₀ = 0.9 nmol/L) and low nanomolar activity against five clinically drug-resistant mutant strains. It maintained particularly low cytotoxicity (CC₅₀ = 264 μmol/L) and good selectivity (SI = 256,438). Molecular docking studies revealed that compound 9g exhibited a more stable conformation than 5 due to the newly constructed hydrogen bond of the hydroxymethyl group with E138. Also, compound 9g was characterized by good safety profiles. It displayed no apparent inhibition of CYP enzymes and hERG. The acute toxicity assay did not cause death and pathological damage in mice at a single dose of 2 g/kg. These findings paved the way for the discovery and development of new-generation anti-HIV-1 drugs.

Approved HIV reverse transcriptase inhibitors in the past decade

HIV reverse transcriptase (RT) inhibitors are the important components of highly active antiretroviral therapies (HAARTs) for anti-HIV treatment and pre-exposure prophylaxis in clinical practice. Many RT inhibitors and their combination regimens have been approved in the past ten years, but a review on their drug discovery, pharmacology, and clinical efficacy is lacking. Here, we provide a comprehensive review of RT inhibitors (tenofovir alafenamide, rilpivirine, doravirine, dapivirine, azvudine and elsulfavirine) approved in the past decade, regarding their drug discovery, pharmacology, and clinical efficacy in randomized controlled trials. Novel RT inhibitors such as islatravir, MK-8504, MK-8507, MK8583, IQP-0528, and MIV-150 will be also highlighted. Future development may focus on the new generation of novel antiretroviral inhibitors with higher bioavailability, longer elimination half-life, more favorable side-effect profiles, fewer drug-drug interactions, and higher activities against circulating drug-resistant strains.

Indolylarylsulfones bearing phenylboronic acid and phenylboronate ester functionalities as potent HIV‑1 non-nucleoside reverse transcriptase inhibitors

To explore the chemical space around the entrance channel of the HIV-1 reverse transcriptase (RT) binding pocket, we innovatively designed and synthesized a series of novel indolylarylsulfones (IASs) bearing phenylboronic acid and phenylboronate ester functionalities at the indole-2-carboxamide as new HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs) through structure-based drug design. All the newly synthesized compounds exhibited excellent to moderate potency against wild-type (WT) HIV-1 with EC₅₀ values ranging from 6.7 to 42.6 nM. Among all, (3-ethylphenyl)boronic acid substituted indole-2-carboxamide and (4-ethylphenyl) boronate ester substituted indole-2-carboxamide were found to be the most potent inhibitors (EC₅₀ = 8.5 nM, SI = 3310; EC₅₀ = 6.7 nM, SI = 3549, respectively). Notably, (3-ethylphenyl)boronic acid substituted indole-2-carboxamide maintained excellent activities against the single HIV-1 mutants L100I (EC₅₀ = 7.3 nM), K103N (EC₅₀ = 9.2 nM), as well as the double mutant V106A/F227L (EC₅₀ = 21.1 nM). Preliminary SARs and molecular modelling studies are also discussed in detail.

Antiviral and Antimicrobial Nucleoside Derivatives: Structural Features and Mechanisms of Action

The emergence of new viruses and resistant strains of pathogenic microorganisms has become a powerful stimulus in the search for new drugs. Nucleosides are a promising class of natural compounds, and more than a hundred drugs have already been created based on them, including antiviral, antibacterial and antitumor agents. The review considers the structural and functional features and mechanisms of action of known nucleoside analogs with antiviral, antibacterial or antiprotozoal activity. Particular attention is paid to the mechanisms that determine the antiviral effect of nucleoside analogs containing hydrophobic fragments. Depending on the structure and position of the hydrophobic substituent, such nucleosides can either block the process of penetration of viruses into cells or inhibit the stage of genome replication. The mechanisms of inhibition of viral enzymes by compounds of nucleoside and non-nucleoside nature have been compared. The stages of creation of antiparasitic drugs, which are based on the peculiarities of metabolic transformations of nucleosides in humans body and parasites, have been considered. A new approach to the creation of drugs is described, based on the use of prodrugs of modified nucleosides, which, as a result of metabolic processes, are converted into an effective drug directly in the target organ or tissue. This strategy makes it possible to reduce the general toxicity of the drug to humans and to increase the effectiveness of its action on cells infected by the virus.

Design of the naphthyl-diarylpyrimidines as potent non-nucleoside reverse transcriptase inhibitors (NNRTIs) via structure-based extension into the entrance channel

A series of novel naphthyl-diarylpyrimidine (DAPY) derivatives were designed and synthesized to explore the entrance channel of the non-nucleoside reverse transcriptase inhibitors binding pocket (NNIBP) by incorporating different flexible side chains at the C-6 position. The biological evaluation results showed that all analogues possessed promising HIV-1 inhibitory activity at the nanomolar concentration range. Three compounds (7, 9 and 39) displayed excellent potency against WT HIV-1 strain with EC₅₀ values ranging from 5 to 10 nM and high selectivity indexes (SI = 3504, 30488 and 22846, respectively), which were higher than for nevirapine and comparable to the values for etravirine. The RT inhibition activity, preliminary structure-activity relationship and molecular docking study showed that the side chain at the C-6 position of the DAPYs occupied the entrance channel and significantly influenced anti-HIV activity and selectivity. Additionally, the physicochemical properties were investigated to evaluate the drug-like features, which indicated that introducing various substituents on the pyrimidine ring can improve solubility.

Improving Druggability of Novel Diarylpyrimidine NNRTIs by a Fragment-Based Replacement Strategy: From Biphenyl-DAPYs to Heteroaromatic-Biphenyl-DAPYs

A series of novel heteroaromatic-difluoro-biphenyl-diarylpyrimidines were designed as non-nucleoside anti-HIV inhibitors targeting reverse transcriptase by a fragment-based replacement strategy with the purpose of improving the druggability. Hopping five- or six-membered heterocycle groups on the biphenyl moiety as bioisosterism for intrinsically cyanophenyl gave 23 derivatives. All of these compounds possessed excellent HIV-1 inhibitory activity in the nanomolar range. Among them, 12g with a 4-pyridine group displayed excellent inhibitory activity toward WT and mutant HIV virus possessing significant selectivity. Moreover, this compound exhibited a decent improvement in druggability than etravirine and rilpivirine: (1) The hydrochloric acid salt of 12g exhibited significantly improved water solubility in different pH conditions. (2) 12g did not show apparent CYP enzymatic inhibitory activity or acute toxicity. (3) Excellent oral bioavailability was also revealed (F = 126%, rats) in 12g. Collectively, these novel heteroaromatic-biphenyl-DAPYs represent promising drug candidates for HIV clinical therapy.

Exploiting the hydrophobic channel of the NNIBP: Discovery of novel diarylpyrimidines as HIV-1 NNRTIs against wild-type and K103N mutant viruses

To further explore the chemical space surrounding the "hydrophobic channel" of the NNRTI binding pocket (NNIBP), a new series of diarylpyrimidines (DAPYs) were designed and synthesized as potent HIV-1 non-nucleoside RT inhibitors (NNRTIs). The target compounds were evaluated for anti-HIV potency in MT-4 cells. Most of the synthesized DAPYs exhibited moderate to excellent activity against the HIV-1 wild-type (WT) strain with EC₅₀ values ranging from 16 nM to 0.722 µM. Interestingly, few compounds displayed remarkable activity in inhibiting K103N mutant virus with EC₅₀ values ranging from 39 nM to 1.708 µM. Notably, FS2 (EC_50(IIIB) = 16 nM, EC_50(K103N) = 39 nM, SI = 294) was identified as the most significant compound, which was considerably more potent than nevirapine, lamivudine, and comparable to zidovudine. Additionally, the HIV-1 RT inhibition assay confirmed their binding target. Preliminary structure-activity relationships (SARs) and molecular modeling studies were also performed, providing significant suggestions for further optimization.

In silico structural elucidation of the rabies RNA-dependent RNA polymerase (RdRp) toward the identification of potential rabies virus inhibitors

The rabies virus (RABV) is a non-segmented, negative single-stranded RNA virus which causes acute infection of the central nervous system in humans. Once symptoms appear, the result is nearly always death, and to date, post-exposure prophylaxis (PEP) is the only treatment applicable only immediately after an exposure. Previous studies have identified viral RNA-dependent RNA polymerase (RdRp) as a potential drug target due to its significant role in viral replication and transcription. Herein we generated an energy-minimized homology model of RABIES-RdRp and used it for virtual screening against 2045 NCI Diversity Set III library. The best five ligand-RdRp complexes were picked for further energy minimization via molecular dynamics (MDs) where the complex with ligand Z01690699 shows a minimum score characterized with stable hydrogen bonds and hydrophobic interactions with the catalytic site residues. Our study identified an important ligand for development of remedial approach for treatment of rabies infection.

Hydrophobic Pocket Occupation Design of Difluoro-Biphenyl-Diarylpyrimidines as Non-Nucleoside HIV-1 Reverse Transcriptase Inhibitors: from N-Alkylation to Methyl Hopping on the Pyrimidine Ring

Considering the nonideal metabolic stability of the difluoro-biphenyl-diarylpyrimidine lead compound 4, a series of novel alkylated difluoro-biphenyl-diarylpyrimidines were designed and synthesized based on their structure. Introducing alkyl or substituted alkyl groups on the linker region to block the potential metabolic sensitive sites generated 22 derivatives. Among them, compound 12a with an N-methyl group displayed excellent anti-HIV-1 activity and selectivity. The methyl group was hopped to the central pyrimidine to occupy the small linker region and maintain the water-mediated hydrogen bond observed in the binding of compound 4 with RT. The resulting compound 16y exhibited an improved anti-HIV-1 activity, much lower cytotoxicity, and nanomolar activity toward multiple mutants. In addition, 16y has a better stability in human liver microsomes than 4. Moreover, no apparent in vivo acute toxicity was observed in 16y-treated female, especially pregnant mice. This series of alkylated compounds with highly potency and safety represent a promising lead template for future discovery.

Druggability modification strategies of the diarylpyrimidine-type non-nucleoside reverse transcriptase inhibitors

Drug discovery of human immunodeficiency virus (HIV) is a hot field in medicinal chemistry community for many years. The diarylpyrimidines (DAPYs) are the second-generation non-nucleoside reverse transcriptase inhibitors (NNRTIs) targeting reverse transcriptase, playing a great irreplaceable role in HIV transcriptional therapy. However, fast-growing drug-resistant mutations as nonnegligible challenge are still unpredictably appeared in the clinical practice, leading to deactivate or reduce the existing drugs. In the last 20 years, more and more novel DAPY derivatives have developed with the purpose to counter the mutants. Nevertheless, most of them have dissatisfactory pharmacokinetics (PK) or poor antiviral activity toward resistant mutant strains. In this article, we will analyze the NNRTI derivatives with promising druggability, and summarize a series of druggability modification strategies to improve the antiviral activity, reduce toxicity and improve the PK properties in recent years. The prospects of DAPYs and the directions for future efforts will be discussed.

Design, synthesis, and evaluation of "dual-site"-binding diarylpyrimidines targeting both NNIBP and the NNRTI adjacent site of the HIV-1 reverse transcriptase

Inspired by our previous efforts to improve the drug-resistance profiles of HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs), a novel series of "dual-site" binding diarylpyrimidine (DAPY) derivatives targeting both the NNRTI adjacent site and NNRTIs binding pocket (NNIBP) were designed, synthesized, and evaluated for their anti-HIV potency in TZM-bl and MT-4 cells. Eight compounds exhibited moderate to excellent potencies in inhibiting wild-type (WT) HIV-1 replication with EC₅₀ values ranging from 2.45 nM to 5.36 nM, and 14c (EC₅₀ = 2.45 nM) proved to be the most promising inhibitor. Of note, 14c exhibited potent activity against the single mutant strain E138K (EC₅₀ = 10.6 nM), being comparable with ETR (EC₅₀ = 9.80 nM) and 3.5-fold more potent than that of compound 7 (EC₅₀ = 37.3 nM). Moreover, 14c acted as a classical NNRTI with high affinity for WT HIV-1 RT (IC₅₀ = 0.0589 μM). The detailed structure-activity relationships (SARs) of the representative compounds were also determined, and further supported by molecular dynamics simulation. Overall, we envision that the "dual-site"-binding NNRTIs have significant prospects and pave the way for the next round of rational design of potent anti-HIV-1 agents.

Structure-activity relationship, molecular docking, and molecular dynamic studies of diterpenes from marine natural products with anti-HIV activity

HIV-1 infection is a global epidemic whose treatment is limited majorly by viral resistance and adverse effects. Natural products from algae have been studied for many years, including antiviral, being an alternative to anti-HIV drug design. Since the isolation of natural products can be a hurdle, molecular modeling is an important tool to study these compounds. Herein, structure-activity relationship, molecular docking, and molecular dynamic studies were performed to direct the studies of ten marine natural products with anti-HIV activity. In the structure-activity relationship, descriptors were identified associating the anti-HIV activity of five diterpenes with possible action on the reverse transcriptase allosteric site. These diterpenes were evaluated by molecular docking, and it was identified that only dolabelladienetriol interacted in the allosteric site. Molecular dynamics suggested that the dolabelladienetriol might interfere with the viral RNA binding to HIV-1 RT by inducing a conformational change of the enzyme. Also, in silico ADMET simulations predicts that the dolabelladienetriol present a high potential to be successfully developed as a drug. Thus, applying in silico approaches was possible to suggest potential anti-HIV compounds derived from marine natural products.Communicated by Ramaswamy H. Sarma.

Recent discoveries in HIV-1 reverse transcriptase inhibitors

HIV-1 reverse transcriptase inhibitors (RTIs) are indispensable components of highly active antiretroviral therapy (HAART), which has achieved great success in controlling AIDS epidemic in reducing drastically the morbidity and mortality of HIV-infected patients. RTIs are divided into two categories, nucleoside reverse transcriptase inhibitors (NRTIs) and nonnucleoside reverse transcriptase inhibitors (NNRTIs). In this review, the recent discoveries in NRTIs and NNRTIs, including approved anti-HIV drugs and noteworthy drug candidates in different development stages, are summarized, and their future direction is prospected.

Development of non-nucleoside reverse transcriptase inhibitors (NNRTIs): our past twenty years

Human immunodeficiency virus (HIV) is the primary infectious agent of acquired immunodeficiency syndrome (AIDS), and non-nucleoside reverse transcriptase inhibitors (NNRTIs) are the cornerstone of HIV treatment. In the last 20 years, our medicinal chemistry group has made great strides in developing several distinct novel NNRTIs, including 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT), thio-dihydro-alkoxy-benzyl-oxopyrimidine (S-DABO), diaryltriazine (DATA), diarylpyrimidine (DAPY) analogues, and their hybrid derivatives. Application of integrated modern medicinal strategies, including structure-based drug design, fragment-based optimization, scaffold/fragment hopping, molecular/fragment hybridization, and bioisosterism, led to the development of several highly potent analogues for further evaluations. In this paper, we review the development of NNRTIs in the last two decades using the above optimization strategies, including their structure–activity relationships, molecular modeling, and their binding modes with HIV-1 reverse transcriptase (RT). Future directions and perspectives on the design and associated challenges are also discussed.

Design of Biphenyl-Substituted Diarylpyrimidines with a Cyanomethyl Linker as HIV-1 NNRTIs via a Molecular Hybridization Strategy

The key problems of human immunodeficiency virus (HIV) therapy are the rapid emergence of drug-resistant mutant strains and significant cumulative drug toxicities. Therefore, there is an urgent demand for new anti-HIV agents with low toxicity and broad-spectrum antiviral potency. A series of biphenyl-substituted diarylpyrimidines with a cyanomethyl linker were designed using a molecular hybridization strategy. The cell-based anti-HIV assay showed that most of the compounds exhibited moderate to good activities against wild-type HIV-1 and clinically relevant mutant strains with a more favorable toxicity, and the enzymatic assay showed they had nanomolar activity against reverse transcriptase (RT). Compound 10p exhibited the best activity against wild-type HIV-1 with an EC50 (50% HIV-1 replication inhibitory concentration) value of 0.027 µM, an acceptable CC50 (50% cytotoxic concentration) value of 36.4 µM, and selectivity index of 1361, with moderate activities against the single mutants (EC50: E138K, 0.17 µM; Y181C, 0.87 µM; K103N, 0.9 µM; L100I, 1.21 µM, respectively), and an IC50 value of 0.059 µM against the RT enzyme, which was six-fold higher than nevirapine (NVP). The preliminary structure-activity relationship (SAR) of these new compounds was concluded. The molecular modeling predicted the binding modes of the new compounds with RT, providing molecular insight for further drug design.

Ligand-Based Design of Nondimethylphenyl-Diarylpyrimidines with Improved Metabolic Stability, Safety, and Oral Pharmacokinetic Profiles

A series of nondimethylphenyl-diarylpyrimidines with much lower cytotoxicities than their dimethyl analogues were developed. Compound B13 with a difluorobiphenyl moiety showed the highest antiviral activity against WT, mutant strains, and RT. The hydrochloride form of B13 exhibited an improved water solubility of 5.6 μg/mL compared with ETR (≪1 μg/mL), better stability in human and rat liver microsomes, and a great oral bioavailability of 44%, making it promising as a drug candidate. In addition, no apparent toxicity was observed in the acute toxicity assay (2 g/kg) and HE staining.