Simulated human digestion of N1-aryl-2-arylthioacetamidobenzimidazoles and their activity against Herpes-simplex virus 1 in vitro.

Drug performance in the gastrointestinal tract (GIT) plays a crucial role in determining release and absorption. In the present work, we assessed the in vitro digestion of two synthetic N1-aryl-2-arylthioacetamidobenzimidazoles (NAABs), NAAB-496 and NAAB-503, using bio-relevant models of the human stomach and small intestine. The activity of NAAB-496 and NAAB-503 against herpes simplex virus (HSV-1) replication was also investigated. NAAB-496 was resistant to pepsin in the gastric environment, with a virtual 100% recovery, which decreased to 43.2% in the small intestine. NAAB-503 was sensitive to pepsin, with 65.7% degradation after 120 min gastric phase. 1H Nuclear magnetic resonance (NMR) post in vitro digestion highlighted an alteration of NAAB-496 after the gastric phase, whereas NAAB-503 appeared comparable to the original spectral data. Both NAAB-496 and NAAB-503 revealed some antiviral activity anti-HSV-1. The 50% effective concentration (EC50) of the compounds was 0.058 mg/mL for NAAB-496 and 0.066 for NAAB-503. Future studies will evaluate the behavior of NAAB-496 within pharmaceutical formulations.

Graphene Quantum Dots Based Systems As HIV Inhibitors.

Graphene quantum dots (GQD) are the next generation of nanomaterials with great potential in drug delivery and target-specific HIV inhibition. In this study we investigated the antiviral activity of graphene based nanomaterials by using water-soluble GQD synthesized from multiwalled carbon nanotubes (MWCNT) through prolonged acidic oxidation and exfoliation and compared their anti-HIV activity with that exerted by reverse transcriptase inhibitors (RTI) conjugated with the same nanomaterial. The antiretroviral agents chosen in this study, CHI499 and CDF119, belong to the class of non-nucleoside reverse transcriptase inhibitors (NNRTI). From this study emerged the RTI-conjugated compound GQD-CHI499 as a good potential candidate for HIV treatment, showing an IC50 of 0.09 µg/mL and an EC50 value in cell of 0.066 µg/mL. The target of action in the replicative cycle of HIV of the drug conjugated samples GQD-CHI499 and GQD-CDF119 was also investigated by a time of addition (TOA) method, showing for both conjugated samples a mechanism of action similar to that exerted by NNRTI drugs.

Discovery of benzimidazole-based Leishmania mexicana cysteine protease CPB2.8ΔCTE inhibitors as potential therapeutics for leishmaniasis.

Chemotherapy is currently the only effective approach to treat all forms of leishmaniasis. However, its effectiveness is severely limited due to high toxicity, long treatment length, drug resistance, or inadequate mode of administration. As a consequence, there is a need to identify new molecular scaffolds and targets as potential therapeutics for the treatment of this disease. We report a small series of 1,2-substituted-1H-benzo[d]imidazole derivatives (9a-d) showing affinity in the submicromolar range (Ki  = 0.15-0.69 µM) toward Leishmania mexicanaCPB2.8ΔCTE, one of the more promising targets for antileishmanial drug design. The compounds confirmed activity in vitro against intracellular amastigotes of Leishmania infantum with the best result being obtained with derivative 9d (IC50  = 6.8 µM), although with some degree of cytotoxicity (CC50  = 8.0 µM on PMM and CC50  = 32.0 µM on MCR-5). In silico molecular docking studies and ADME-Tox properties prediction were performed to validate the hypothesis of the interaction with the intended target and to assess the drug-likeness of these derivatives.

Structural optimization of N1-aryl-benzimidazoles for the discovery of new non-nucleoside reverse transcriptase inhibitors active against wild-type and mutant HIV-1 strains.

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are recommended components of preferred combination antiretroviral therapies used for the treatment of human immunodeficiency virus (HIV) infection. These regimens are extremely effective in suppressing virus replication. Recently, our research group identified some N1-aryl-2-arylthioacetamido-benzimidazoles as a novel class of NNRTIs. In this research work we report the design, the synthesis and the structure-activity relationship studies of new compounds (20-34) in which some structural modifications have been introduced in order to investigate their effects on reverse transcriptase (RT) inhibition and to better define the features needed to increase the antiviral activity. Most of the new compounds proved to be highly effective in inhibiting both RT enzyme at nanomolar concentrations and HIV-1 replication in MT4 cells with minimal cytotoxicity. Among them, the most promising N1-aryl-2-arylthioacetamido-benzimidazoles and N1-aryl-2-aryloxyacetamido-benzimidazoles were also tested toward a panel of single- and double-mutants strain responsible for resistance to NNRTIs, showing in vitro antiviral activity toward single mutants L100I, K103N, Y181C, Y188L and E138K. The best results were observed for derivatives 29 and 33 active also against the double mutants F227L and V106A. Computational approaches were applied in order to rationalize the potency of the new synthesized inhibitors.

Searching for novel N1-substituted benzimidazol-2-ones as non-nucleoside HIV-1 RT inhibitors.

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) represent an integral part of the currently available combination antiretroviral therapy (cART) contributing to reduce the AIDS-mortality and turned the disease from lethal to chronic. In this context we recently reported a series of 6-chloro-1-(3-methylphenylsulfonyl)-1,3-dihydro-2H-benzimidazol-2-ones as potent non-nucleoside HIV-1 reverse transcriptase inhibitors. In this paper, we describe the design and the synthesis of two novel series of benzimidazolone analogues in which the linker moiety between the phenyl ring and the sulfonyl group was modified and new small lipophilic groups on the benzyl sulfonyl pendant were introduced. All the new obtained compounds were evaluated as RT inhibitors and were also tested against RTs containing single amino acid mutations. Finally, molecular docking studies were performed in order to rationalize the observed activity of the most promising compound.

In†Vivo Evaluation of Selective Carbonic Anhydrase Inhibitors as Potential Anticonvulsant Agents.

Epilepsy is a common neurological disorder caused by an imbalance between inhibitory and excitatory neurotransmission. It is well known that neuronal excitability is related to γ-aminobutyric acid (GABA)ergic depolarization. HCO3 (-) -dependent depolarization can be suppressed by membrane-permeable inhibitors of carbonic anhydrase. We previously identified some isoquinoline sulfonamides as potent and selective inhibitors of the human carbonic anhydrase II and VII (hCA II and hCA VII) isoforms. Given that hCA II and hCA VII are specific isoforms involved in GABA-mediated neuronal excitation, we hypothesized that they could represent the biological target for the development of new anticonvulsant agents. Therefore, for selected isoquinoline sulfonamides, we preliminarily tested their ability to prevent audiogenic seizures in DBA/2 mice. All compounds were evaluated after intraperitoneal administration, and some of them proved to protect the mice against convulsions. Among this series of compounds, several derivatives showed combined in vivo efficacy with inhibitory effects toward the targeted carbonic anhydrases (i.e., hCA II and hCA VII). Specifically, the most interesting molecule was 1-(4-aminophenyl)-6,7-dimethoxy-3,4-dihydroisoquinoline-2(1H)-sulfonamide (6), which proved to be a more active and selective hCA VII inhibitor than the reference compound topiramate. Further studies to explore the in vivo pharmacokinetic profile of the most active compounds may help to provide insight into the future design of selective hCA VII inhibitors.

A thiazepino[4,5-a]benzimidazole derivative hampers the RNA replication of Eurasian serotypes of foot-and-mouth disease virus.

The stamping-out policy for the control of foot-and-mouth disease virus (FMDV) in countries that are free from FMD without vaccination has a dramatic socio-economic impact, huge animal welfare issues and may result in the loss of farm animal genetic resources. As an alternative to pre-emptive culling or emergency vaccination we further explore the possibility to use antiviral drugs in the event of an FMD outbreak. In the present study, we tested the in vitro cytotoxicity and anti-FMDV activity of 1,2,4,5-tetrahydro-[1,4]thiazepino[4,5-a]benzimidazole. The molecule was shown to inhibit the replication of reference strains of the Eurasian FMDV serotypes O, A, C and Asia but not the FMDV serotypes from the South African Territories (SAT) neither a related picornavirus, i.e. swine vesicular disease virus. The molecule can be added until 2h post inoculation in a 'single replication cycle experiment' without losing its antiviral activity. The genetic characterization of progressively selected resistant FMD viruses shows that the molecule presumably interacts with the non-structural 2C protein of FMDV. Further studies are required on the use of this molecule in vivo.

Design and synthesis of N1-aryl-benzimidazoles 2-substituted as novel HIV-1 non-nucleoside reverse transcriptase inhibitors.

A series of novel N1-aryl-2-arylthioacetamido-benzimidazoles were synthesized and evaluated as inhibitors of human immunodeficiency virus type-1 (HIV-1). Some of them proved to be effective in inhibiting HIV-1 replication at submicromolar and nanomolar concentration acting as HIV-1 non-nucleoside RT inhibitors (NNRTIs), with low cytotoxicity. The preliminary structure-activity relationship (SAR) of these new derivatives was discussed and rationalized by docking studies.

3-[2-(1H-1,3-Benzodiazol-2-yl)eth-yl]-1,3-oxazolidin-2-one.

In the title compound, C(12)H(13)N(3)O(2), the dihedral angle between the oxazolone ring and the benzimidazole unit is 45.0 (5)°, exhibiting a staggered conformation at the Cα-Cß bond. In the crystal, a strong N-H⋯N hydrogen bond links the mol-ecules into a C(4) chain along the c axis while a C-H⋯O hydrogen-bonding inter-action generates a C(5) chain along the a axis, i.e. perpendicular to the other chain.

Slow binding-tight binding interaction between benzimidazol-2-one inhibitors and HIV-1 reverse transcriptase containing the lysine 103 to asparagine mutation.

Novel benzimidazol-2-one non-nucleoside reverse transcriptase inhibitors (NNRTIs) have been recently identified, through rational structure-based molecular modeling and docking approaches, as highly effective inhibitors of the wild type and drug-resistant HIV-1 reverse transcriptase (RT). These compounds also showed potent anti-HIV activities against viral strains, superior to the clinically approved NNRTI efavirenz. However, they were still of limited efficacy towards the K103N mutant. Here we report a detailed enzymatic analysis elucidating the molecular mechanism of interaction between benzimidazol-2-one derivatives and the K103N mutant RT. The loss of potency of these molecules towards the K103N RT was specifically due to a reduction of their association rate to the enzyme. Unexpectedly, these compounds showed a strongly reduced dissociation rate from the K103N mutant, as compared to the wild type enzyme, suggesting that, once occupied by the drug, the mutated binding site could achieve a more stable interaction with these molecules. The characterization of this slow binding-tight binding mutant-specific mechanism of interaction may pave the way to the design of more effective new generation benzimidazol-2-one NNRTIs with promising drug resistant profile and minimal toxicity.

Novel 1,3-dihydro-benzimidazol-2-ones and their analogues as potent non-nucleoside HIV-1 reverse transcriptase inhibitors.

A series of novel benzimidazolones and their analogues, characterized by the presence of one or more methyl groups or other bioisosteric moieties at different positions of the phenyl ring at N-1, were synthesized and evaluated as inhibitors of human immunodeficiency virus type-1 (HIV-1). Most of the new compounds proved to be highly effective in inhibiting both HIV-1 replication in MT4 cells with minimal cytotoxicity and RT enzyme at nanomolar concentrations. Some derivatives were also tested against RTs containing single amino acid mutations responsible for resistance to non-nucleoside reverse transcriptase inhibitors (NNRTIs). The different potencies displayed by the new compounds were studied using molecular modeling.

Design, synthesis, and structure-activity relationships of 1,3-dihydrobenzimidazol-2-one analogues as anti-HIV agents.

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) have become very important components in the antiretroviral combination therapies used to treat HIV. Recently, our group identified some 1,3-dihydrobenzimidazol-2-one derivatives and their sulfones as a potent and novel class of NNRTIs. We herein report the synthesis and biological evaluation of the new compounds in which different structural modifications have been introduced in order to investigate their effects on RT inhibition.

Pharmacophore-based discovery of small-molecule inhibitors of protein-protein interactions between HIV-1 integrase and cellular cofactor LEDGF/p75.

The cellular protein lens epithelium-derived growth factor, or transcriptional coactivator p75 (LEDGF/p75), plays a crucial role in HIV integration. The protein-protein interactions (PPIs) between HIV-1 integrase (IN) and its cellular cofactor LEDGF/p75 may therefore serve as targets for the development of new anti-HIV drugs. In this work, a structure-based pharmacophore model for potential small-molecule inhibitors of HIV-1 IN-LEDGF/p75 interaction was developed using the LigandScout software. The 3D model obtained was used for virtual screening of our in-house chemical database, CHIME, leading to the identification of compound CHIBA-3002 as an interesting hit for further optimization. The rational design, synthesis and biological evaluation of four derivatives were then carried out. Our studies resulted in the discovery of a new and more potent small molecule (7, CHIBA-3003) that is able to interfere with the HIV-1 IN-LEDGF/p75 interaction at micromolar concentration, representing one of the first compounds to show activity against these specific PPIs. Docking simulations were subsequently performed in order to investigate the possible binding mode of our new lead compound to HIV-1 IN. This study is a valid starting point for the identification of anti-HIV agents with a different mechanism of action from currently available antiviral drugs.

Novel N1-substituted 1,3-dihydro-2H-benzimidazol-2-ones as potent non-nucleoside reverse transcriptase inhibitors.

Several N(1)-substituted 1,3-dihydro-2H-benzimidazol-2-ones were synthesized and evaluated as anti-HIV agents. Some of them proved to be highly effective in inhibiting HIV-1 replication at nanomolar concentration as potent non-nucleoside HIV-1 RT inhibitors (NNRTIs) with low cytotoxicity. SAR studies highlighted that the nature of the substituents at N(1) and on the benzene ring of benzimidazolone moiety significantly influenced the anti-HIV activity of this class of potent antiretroviral agents.

The thiazolobenzimidazole TBZE-029 inhibits enterovirus replication by targeting a short region immediately downstream from motif C in the nonstructural protein 2C.

TBZE-029 {1-(2,6-difluorophenyl)-6-trifluoromethyl-1H,3H-thiazolo[3,4-a]benzimidazole} is a novel selective inhibitor of the replication of several enteroviruses. We show that TBZE-029 exerts its antiviral activity through inhibition of viral RNA replication, without affecting polyprotein processing. To identify the viral target of TBZE-029, drug-resistant coxsackievirus B3 (CVB3) was selected. Genotyping of resistant clones led to the identification of three amino acid mutations in nonstructural protein 2C, clustered at amino acid positions 224, 227, and 229, immediately downstream of NTPase/helicase motif C. The mutations were reintroduced, either alone or combined, into an infectious full-length CVB3 clone. In particular the mutations at positions 227 and 229 proved essential for the altered sensitivity of CVB3 to TBZE-029. Resistant virus exhibited cross-resistance to the earlier-reported antienterovirus agents targeting 2C, namely, guanidine hydrochloride, HBB [2-(alpha-hydroxybenzyl)-benzimidazole], and MRL-1237 {1-(4-fluorophenyl)-2-[(4-imino-1,4-dihydropyridin-1-yl)methyl]benzimidazole hydrochloride}. The ATPase activity of 2C, however, remained unaltered in the presence of TBZE-029.

New 4-[(1-benzyl-1H-indol-3-yl)carbonyl]-3-hydroxyfuran-2(5H)-ones, beta-diketo acid analogs as HIV-1 integrase inhibitors.

In addition to our recent report on a series of rationally designed benzylindolyldiketo acids acting as potent HIV-1 integrase strand transfer inhibitors, we disclose the results obtained with novel compounds chemically modified on the diketo acid moiety in order to investigate its influence on the biological activity and cytotoxicity. The activity of designed and synthesized 4-[(1-benzyl-1H-indol-3-yl)carbonyl]-3-hydroxyfuran-2(5H)-one derivatives lies in the micromolar range with regard to HIV IN enzymatic activity. The microwave-assisted synthesis was employed in some steps of the chemical procedures.

Discovery of novel benzimidazolones as potent non-nucleoside reverse transcriptase inhibitors active against wild-type and mutant HIV-1 strains.

Molecular modeling studies led to the rational discovery of N(1)-arylsulfonyl-1,3-dihydro-2H-benzimidazol-2-one as a novel template for the design of new non-nucleoside reverse transcriptase inhibitors (NNRTIs) that are active against wild-type and mutant strains of HIV-1. It is worth noting that compound 3 proved to have antiretroviral activity similar to that of efavirenz and greater than that of nevirapine, two of the three NNRTIs currently available in antiretroviral therapy.

Anti-enterovirus activity and structure-activity relationship of a series of 2,6-dihalophenyl-substituted 1H,3H-thiazolo[3,4-a]benzimidazoles.

Despite the fact that enteroviruses are implicated in a variety of human diseases, there is no approved therapy for the treatment of enteroviral infections. Here, a series of 2,6-dihalophenyl-substituted 1H,3H-thiazolo[3,4-a]benzimidazoles with anti-enterovirus activity is reported. The compounds elicit potent activity against coxsackievirus A9, echovirus 9 and 11 and all six strains of coxsackievirus B. A structure-activity relationship analysis revealed that the presence of substituents at position 6 of the tricyclic system positively influences the antiviral activity, whereas substitutions at position 7 are less favorable. In particular a 6-trifluoromethyl substitution leads to a substantial improvement of the antiviral activity as compared to the unsubstituted structure. Furthermore, an additional introduction of a 2-Cl, 6-F substitution on the phenyl at C-1 results in a further increase of the antiviral activity. Hence, 1-(2-chloro-6-fluorophenyl)-6-trifluoromethyl-1H,3H-thiazolo[3,4-a]benzimidazole results in a dose-dependent inhibition of viral replication with a 50% effective concentration (EC50) of 0.41 microg/ml without any detectable cytotoxicity at the highest concentration (100 microg/ml) tested.

Pharmacophore-based design of HIV-1 integrase strand-transfer inhibitors.

Using a training set of diketo-like acid HIV-1 integrase (IN) strand-transfer inhibitors, a 3D pharmacophore model was derived having quantitative predictive ability in terms of activity. The best statistical hypothesis consisted of four features (one hydrophobic aromatic region, two hydrogen-bond acceptors, and one hydrogen-bond donor) with r of 0.96. The resulting pharmacophore model guided the rational design of benzylindoles as new potent IN inhibitors, whose microwave-assisted synthesis and biological evaluation are reported.

Computational strategies in discovering novel non-nucleoside inhibitors of HIV-1 RT.

A three-dimensional common feature pharmacophore model was developed using the X-ray structure of RT/non-nucleoside inhibitor (NNRTI) complexes. Starting from the pharmacophore hypothesis and the structure of the lead compound TBZ, new NNRTIs were designed and synthesized, having the benzimidazol-2-one system as a scaffold. Docking experiments showed that these molecules docked in a position and orientation similar to that of known inhibitors. Biological testing confirmed that our strategy was successful in searching for new leads as NNRTIs.