GRL-09510, a Unique P2-Crown-Tetrahydrofuranylurethane -Containing HIV-1 Protease Inhibitor, Maintains Its Favorable Antiviral Activity against Highly-Drug-Resistant HIV-1 Variants in vitro

Machine learning-guided design of potent darunavir analogs targeting HIV-1 proteases: A computational approach for antiretroviral drug discovery

In the pursuit of novel antiretroviral therapies for human immunodeficiency virus type-1 (HIV-1) proteases (PRs), recent improvements in drug discovery have embraced machine learning (ML) techniques to guide the design process. This study employs ensemble learning models to identify crucial substructures as significant features for drug development. Using molecular docking techniques, a collection of 160 darunavir (DRV) analogs was designed based on these key substructures and subsequently screened using molecular docking techniques. Chemical structures with high fitness scores were selected, combined, and one-dimensional (1D) screening based on beyond Lipinski's rule of five (bRo5) and ADME (absorption, distribution, metabolism, and excretion) prediction implemented in the Combined Analog generator Tool (CAT) program. A total of 473 screened analogs were subjected to docking analysis through convolutional neural networks scoring function against both the wild-type (WT) and 12 major mutated PRs. DRV analogs with negative changes in binding free energy (ΔΔ G bind ) compared to DRV could be categorized into four attractive groups based on their interactions with the majority of vital PRs. The analysis of interaction profiles revealed that potent designed analogs, targeting both WT and mutant PRs, exhibited interactions with common key amino acid residues. This observation further confirms that the ML model-guided approach effectively identified the substructures that play a crucial role in potent analogs. It is expected to function as a powerful computational tool, offering valuable guidance in the identification of chemical substructures for synthesis and subsequent experimental testing.

Expanding the therapeutic options for Candida infections using novel inhibitors of secreted aspartyl proteases

For widening the therapeutic options for Candida management, the druggability of Candida proteome was systematically investigated using an innovative pipeline of high-throughput data mining algorithms, followed by in vitro validation of the observations. Through this exercise, HIV-1 protease was found to share structural similarity with secreted aspartyl protease-3 (SAP3), a virulence protein of Candida. Using the molecular fingerprint of HIV-1 protease inhibitor GRL-09510, we performed virtual screening of peptidomimetic library followed by high-precision docking and MD simulations for discovery of SAP inhibitors. Wet-lab validation of the four shortlisted peptidomimetics revealed that two molecules, when used in combination with fluconazole, could significantly reduce the dosage of fluconazole required for 50% inhibition of Candida albicans. The SAP inhibitory activity of these peptidomimetics was confirmed through SAP assays and found to be on par with pepstatin A, a known peptidomimetic inhibitor of aspartyl proteases.

Alkaloids as Potential Anti-HIV Agents

BACKGROUND

Alkaloids are nitrogen-containing compounds that are naturally occurring and have a variety of biological activities, including antimicrobial properties. In this study, the authors used a molecular docking approach to evaluate the anti-HIV potential of 64 alkaloids.

METHODS

The authors used the Molegro Virtual Docker software to dock the alkaloids into the active sites of three HIV enzymes: protease, integrase, and non-nucleoside reverse transcriptase (NNRT). The docking scores were used to assess the potential of the alkaloids to inhibit the enzymes.

RESULTS

The results showed the alkaloids to have good potential to inhibit the enzymes. Tubocurarine and reserpine were found to be the most potent alkaloids, with docking scores of -123.776 and - 114.956, respectively.

CONCLUSION

The authors concluded that tubocurarine and reserpine could be further promoted as potential lead molecules for the development of new anti-HIV drugs.

Beyond darunavir: recent development of next generation HIV-1 protease inhibitors to combat drug resistance

We report our recent development of a conceptually new generation of exceptionally potent non-peptidic HIV-1 protease inhibitors that displayed excellent pharmacological and drug-resistance profiles. Our X-ray structural studies of darunavir and other designed inhibitors from our laboratories led us to create a variety of inhibitors incorporating fused ring polycyclic ethers and aromatic heterocycles to promote hydrogen bonding interactions with the backbone atoms of HIV-1 protease as well as van der Waals interactions with residues in the S2 and S2' subsites. We have also incorporated specific functionalities to enhance van der Waals interactions in the S1 and S1' subsites. The combined effects of these structural templates are critical to the inhibitors' exceptional potency and drug-like properties. We highlight here our molecular design strategies to promote backbone hydrogen bonding interactions to combat drug-resistance and specific design of polycyclic ether templates to mimic peptide-like bonds in the HIV-1 protease active site. Our medicinal chemistry and drug development efforts led to the development of new generation inhibitors significantly improved over darunavir and displaying unprecedented antiviral activity against multidrug-resistant HIV-1 variants.

Fluorine Modifications Contribute to Potent Antiviral Activity against Highly Drug-Resistant HIV-1 and Favorable Blood-Brain Barrier Penetration Property of Novel Central Nervous System-Targeting HIV-1 Protease Inhibitors In Vitro

To date, there are no specific treatment regimens for HIV-1-related central nervous system (CNS) complications, such as HIV-1-associated neurocognitive disorders (HAND). Here, we report that two newly generated CNS-targeting HIV-1 protease (PR) inhibitors (PIs), GRL-08513 and GRL-08613, which have a P1-3,5-bis-fluorophenyl or P1-para-monofluorophenyl ring and P2-tetrahydropyrano-tetrahydrofuran (Tp-THF) with a sulfonamide isostere, are potent against wild-type HIV-1 strains and multiple clinically isolated HIV-1 strains (50% effective concentration [EC50]: 0.0001 to ∼0.0032 μM). As assessed with HIV-1 variants that had been selected in vitro to propagate at a 5 μM concentration of each HIV-1 PI (atazanavir, lopinavir, or amprenavir), GRL-08513 and GRL-08613 efficiently inhibited the replication of these highly PI-resistant variants (EC50: 0.003 to ∼0.006 μM). GRL-08513 and GRL-08613 also maintained their antiviral activities against HIV-2ROD as well as severely multidrug-resistant clinical HIV-1 variants. Additionally, when we assessed with the in vitro blood-brain barrier (BBB) reconstruction system, GRL-08513 and GRL-08613 showed the most promising properties of CNS penetration among the evaluated compounds, including the majority of FDA-approved combination antiretroviral therapy (cART) drugs. In the crystallographic analysis of compound-PR complexes, it was demonstrated that the Tp-THF rings at the P2 moiety of GRL-08513 and GRL-08613 form robust hydrogen bond interactions with the active site of HIV-1 PR. Furthermore, both the P1-3,5-bis-fluorophenyl- and P1-para-monofluorophenyl rings sustain greater contact surfaces and form stronger van der Waals interactions with PR than is the case with darunavir-PR complex. Taken together, these results strongly suggest that GRL-08513 and GRL-08613 have favorable features for patients infected with wild-type/multidrug-resistant HIV-1 strains and might serve as candidates for a preventive and/or therapeutic agent for HAND and other CNS complications.

Decoding molecular mechanism underlying binding of drugs to HIV-1 protease with molecular dynamics simulations and MM-GBSA calculations

HIV-1 protease (PR) is thought to be efficient targets of anti-AIDS drug design. Molecular dynamics (MD) simulations and multiple post-processing analysis technologies were applied to decipher molecular mechanism underlying binding of three drugs Lopinavir (LPV), Nelfinavir (NFV) and Atazanavir (ATV) to the PR. Binding free energies calculated by molecular mechanics generalized Born surface area (MM-GBSA) suggest that compensation between binding enthalpy and entropy plays a vital role in binding of drugs to PR. Dynamics analyses show that binding of LPV, NFV and ATV highly affects structural flexibility, motion modes and dynamics behaviour of the PR, especially for two flaps. Computational alanine scanning and interaction network analysis verify that although three drugs have structural difference, they share similar binding modes to the PR and common interaction clusters with the PR. The current findings also confirm that residues located interaction clusters, such as Asp25/Asp25', Gly27/Gly27', Ala28/Ala28', Asp29, Ile47/Ile47', Gly49/Gly49', Ile50/Ile50', Val82/Val82' and Ile84/Ile84, can be used as efficient targets of clinically available inhibitors towards the PR.

A Small Molecule, ACAi-028, with Anti-HIV-1 Activity Targets a Novel Hydrophobic Pocket on HIV-1 Capsid

The human immunodeficiency virus type 1 (HIV-1) capsid (CA) is an essential viral component of HIV-1 infection and an attractive therapeutic target for antivirals. Here, we report that a small molecule, ACAi-028, inhibits HIV-1 replication by targeting a hydrophobic pocket in the N-terminal domain of CA (CA-NTD). ACAi-028 is 1 of more than 40 candidate anti-HIV-1 compounds identified by in silico screening and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Our binding model showed that ACAi-028 interacts with the Q13, S16, and T19 amino acid residues, via hydrogen bonds, in the targeting pocket of CA-NTD. Using recombinant fusion methods, TZM-bl, time-of-addition, and colorimetric reverse transcriptase (RT) assays, the compound was found to exert anti-HIV-1 activity in the early stage between reverse transcription and proviral DNA integration, without any effect on RT activity in vitro, suggesting that this compound may affect HIV-1 core disassembly (uncoating) as well as a CA inhibitor, PF74. Moreover, electrospray ionization mass spectrometry (ESI-MS) also showed that the compound binds directly and noncovalently to the CA monomer. CA multimerization and thermal stability assays showed that ACAi-028 decreased CA multimerization and thermal stability via S16 or T19 residues. These results indicate that ACAi-028 is a new CA inhibitor by binding to the novel hydrophobic pocket in CA-NTD. This study demonstrates that a compound, ACAi-028, targeting the hydrophobic pocket should be a promising anti-HIV-1 inhibitor.

Structural and molecular basis of the interaction mechanism of selected drugs towards multiple targets of SARS-CoV-2 by molecular docking and dynamic simulation studies- deciphering the scope of repurposed drugs

The repurposing of FDA approved drugs is presently receiving attention for COVID-19 drug discovery. Previous studies revealed the binding potential of several FDA-approved drugs towards specific targets of SARS-CoV-2; however, limited studies are focused on the structural and molecular basis of interaction of these drugs towards multiple targets of SARS-CoV-2. The present study aimed to predict the binding potential of six FDA drugs towards fifteen protein targets of SARS-CoV-2 and propose the structural and molecular basis of the interaction by molecular docking and dynamic simulation. Based on the literature survey, fifteen potential targets of SARS-CoV-2, and six FDA drugs (Chloroquine, Hydroxychloroquine, Favipiravir, Lopinavir, Remdesivir, and Ritonavir) were selected. The binding potential of individual drug towards the selected targets was predicted by molecular docking in comparison with the binding of the same drugs with their usual targets. The stabilities of the best-docked conformations were confirmed by molecular dynamic simulation and energy calculations. Among the selected drugs, Ritonavir and Lopinavir showed better binding towards the prioritized targets with minimum binding energy (kcal/mol), cluster-RMS, number of interacting residues, and stabilizing forces when compared with the binding of Chloroquine, Favipiravir, and Hydroxychloroquine, later drugs demonstrated better binding when compared to the binding with their usual targets. Remdesvir showed better binding to the prioritized targets in comparison with the binding of Chloroquine, Favipiravir, and Hydroxychloroquine, but showed lesser binding potential when compared to the interaction between Ritonavir and Lopinavir and the prioritized targets. The structural and molecular basis of interactions suggest that the FDA drugs can be repurposed towards multiple targets of SARS-CoV-2, and the present computational models provide insights on the scope of repurposed drugs against COVID-19.

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Molecular mechanism of the binding of six drugs to multiple targets of SARS-CoV-2.

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Highlight the scope of repurposing of six drugs towards 15 targets of SARS-CoV-2.

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Ritonavir and Lopinavir possessed significant binding potential towards multiple targets.

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MD studies showed that the repurposing of these drugs to selected targets provide future insights.

Novel Protease Inhibitors Containing C-5-Modified bis-Tetrahydrofuranylurethane and Aminobenzothiazole as P2 and P2' Ligands That Exert Potent Antiviral Activity against Highly Multidrug-Resistant HIV-1 with a High Genetic Barrier against the Emergence of Drug Resistance

Combination antiretroviral therapy has achieved dramatic reductions in the mortality and morbidity in people with HIV-1 infection. Darunavir (DRV) represents a most efficacious and well-tolerated protease inhibitor (PI) with a high genetic barrier to the emergence of drug-resistant HIV-1. However, highly DRV-resistant variants have been reported in patients receiving long-term DRV-containing regimens. Here, we report three novel HIV-1 PIs (GRL-057-14, GRL-058-14, and GRL-059-14), all of which contain a P2-amino-substituted-bis-tetrahydrofuranylurethane (bis-THF) and a P2'-cyclopropyl-amino-benzothiazole (Cp-Abt). These PIs not only potently inhibit the replication of wild-type HIV-1 (50% effective concentration [EC₅₀], 0.22 nM to 10.4 nM) but also inhibit multi-PI-resistant HIV-1 variants, including highly DRV-resistant HIV_DRV ^R _P51 (EC₅₀, 1.6 nM to 30.7 nM). The emergence of HIV-1 variants resistant to the three compounds was much delayed in selection experiments compared to resistance to DRV, using a mixture of 11 highly multi-PI-resistant HIV-1 isolates as a starting HIV-1 population. GRL-057-14 showed the most potent anti-HIV-1 activity and greatest thermal stability with wild-type protease, and potently inhibited HIV-1 protease's proteolytic activity (K_i value, 0.10 nM) among the three PIs. Structural models indicate that the C-5-isopropylamino-bis-THF moiety of GRL-057-14 forms additional polar interactions with the active site of HIV-1 protease. Moreover, GRL-057-14's P1-bis-fluoro-methylbenzene forms strong hydrogen bonding and effective van der Waals interactions. The present data suggest that the combination of C-5-aminoalkyl-bis-THF, P1-bis-fluoro-methylbenzene, and P2'-Cp-Abt confers highly potent activity against wild-type and multi-PI-resistant HIV strains and warrant further development of the three PIs, in particular, that of GRL-057-14, as potential therapeutic for HIV-1 infection and AIDS.

Novel Central Nervous System (CNS)-Targeting Protease Inhibitors for Drug-Resistant HIV Infection and HIV-Associated CNS Complications

There is currently no specific therapeutics for the HIV-1-related central nervous system (CNS) complications. Here we report that three newly designed CNS-targeting HIV-1 protease inhibitors (PIs), GRL-083-13, GRL-084-13, and GRL-087-13, which contain a P1-3,5-bis-fluorophenyl or P1-para-monofluorophenyl ring, and P2-bis-tetrahydrofuran (bis-THF) or P2-tetrahydropyrano-tetrahydrofuran (Tp-THF), with a sulfonamide isostere, are highly active against wild-type HIV-1 strains and primary clinical isolates (50% effective concentration [EC₅₀], 0.0002 to ∼0.003 μM), with minimal cytotoxicity. These CNS-targeting PIs efficiently suppressed the replication of HIV-1 variants (EC₅₀, 0.002 to ∼0.047 μM) that had been selected to propagate at high concentrations of conventional HIV-1 PIs. Such CNS-targeting PIs maintained their antiviral activity against HIV-2_ROD as well as multidrug-resistant clinical HIV-1 variants isolated from AIDS patients who no longer responded to existing antiviral regimens after long-term therapy. Long-term drug selection experiments revealed that the emergence of resistant-HIV-1 against these CNS-targeting PIs was substantially delayed. In addition, the CNS-targeting PIs showed the most favorable CNS penetration properties among the tested compounds, including various FDA-approved anti-HIV-1 drugs, as assessed with the in vitro blood-brain barrier reconstruction system. Crystallographic analysis demonstrated that the bicyclic rings at the P2 moiety of the CNS-targeting PIs form strong hydrogen-bond interactions with HIV-1 protease (PR) active site. Moreover, both the P1-3,5-bis-fluorophenyl and P1-para-monofluorophenyl rings sustain greater van der Waals contacts with PR than in the case of darunavir (DRV). The data suggest that the present CNS-targeting PIs have desirable features for treating patients infected with wild-type and/or multidrug-resistant HIV-1 strains and might serve as promising preventive and/or therapeutic candidates for HIV-1-associated neurocognitive disorders (HAND) and other CNS complications.

Halogen Bond Interactions of Novel HIV-1 Protease Inhibitors (PI) (GRL-001-15 and GRL-003-15) with the Flap of Protease Are Critical for Their Potent Activity against Wild-Type HIV-1 and Multi-PI-Resistant Variants

We generated two novel nonpeptidic HIV-1 protease inhibitors (PIs), GRL-001-15 and GRL-003-15, which contain unique crown-like tetrahydropyranofuran (Crn-THF) and P2'-cyclopropyl-aminobenzothiazole (Cp-Abt) moieties as P2 and P2' ligands, respectively. GRL-001-15 and GRL-003-15 have meta-monofluorophenyl and para-monofluorophenyl at the P1 site, respectively, exert highly potent activity against wild-type HIV-1 with 50% effective concentrations (EC50s) of 57 and 50 pM, respectively, and have favorable cytotoxicity profiles with 50% cytotoxic concentrations (CC50s) of 38 and 11 μM, respectively. The activity of GRL-001-15 against multi-PI-resistant HIV-1 variants was generally greater than that of GRL-003-15. The EC50 of GRL-001-15 against an HIV-1 variant that was highly resistant to multiple PIs, including darunavir (DRV) (HIV-1DRVRP30), was 0.17 nM, and that of GRL-003-15 was 3.3 nM, while DRV was much less active, with an EC50 of 216 nM. The emergence of HIV-1 variants resistant to GRL-001-15 and GRL-003-15 was significantly delayed compared to that of variants resistant to selected PIs, including DRV. Structural analyses of wild-type protease (PRWT) complexed with the novel PIs revealed that GRL-001-15's meta-fluorine atom forms halogen bond interactions (2.9 and 3.0 Å) with Gly49 and Ile50, respectively, of the protease flap region and with Pro81' (2.7 and 3.2 Å), which is located close to the protease active site, and that two fluorine atoms of GRL-142-13 form multiple halogen bond interactions with Gly49, Ile50, Pro81', Ile82', and Arg8'. In contrast, GRL-003-15 forms halogen bond interactions with Pro81' alone, suggesting that the reduced antiviral activity of GRL-003-15 is due to the loss of the interactions with the flap region.

Design and Synthesis of Highly Potent HIV-1 Protease Inhibitors Containing Tricyclic Fused Ring Systems as Novel P2 Ligands: Structure-Activity Studies, Biological and X-ray Structural Analysis

The design, synthesis, and biological evaluation of a new class of HIV-1 protease inhibitors containing stereochemically defined fused tricyclic polyethers as the P2 ligands and a variety of sulfonamide derivatives as the P2' ligands are described. A number of ring sizes and various substituent effects were investigated to enhance the ligand-backbone interactions in the protease active site. Inhibitors 5c and 5d containing this unprecedented fused 6-5-5 ring system as the P2 ligand, an aminobenzothiazole as the P2' ligand, and a difluorophenylmethyl as the P1 ligand exhibited exceptional enzyme inhibitory potency and maintained excellent antiviral activity against a panel of highly multidrug-resistant HIV-1 variants. The umbrella-like P2 ligand for these inhibitors has been synthesized efficiently in an optically active form using a Pauson-Khand cyclization reaction as the key step. The racemic alcohols were resolved efficiently using a lipase catalyzed enzymatic resolution. Two high resolution X-ray structures of inhibitor-bound HIV-1 protease revealed extensive interactions with the backbone atoms of HIV-1 protease and provided molecular insight into the binding properties of these new inhibitors.