Pharmacokinetic, metabolic profiling and elimination of brusatol in rats.

Brusatol, a quassinoid isolated from the traditional Chinese medicine Brucea javanica, has been reported to be an inhibitor of Nrf2 pathway and has great potential to be developed into a novel chemotherapeutic adjuvant. However, the in vivo process of brusatol has not been comprehensively explained yet. Therefore, this paper focused on the pharmacokinetic metabolism and excretion of brusatol in rats using a simple and reproducible LC-MS/MS method. The results indicated that the plasma concentration of brusatol decreased rapidly; the average cumulative excretion rate in urine was 5.82% during 24 h, and 0.71% in bile during 12 h. High-resolution mass spectrometry was applied for the identification of metabolites; as a result, four metabolites were detected and the structure was tentatively deduced on the base of the MS2 data, Compound Discoverer 2.0 and Mass Frontier 7.0 software. Hydroxylation, hydrolysis and glucuronidation were suggested as major metabolic pathways in vivo. The in vivo process and detection of metabolites of brusatol might improve the understanding of the mechanism of its anticancer effect and provide valuable information for its safety estimation, which will be essential to the new drug development.

Design, synthesis and preliminary SAR studies of novel N-arylmethyl substituted piperidine-linked aniline derivatives as potent HIV-1 NNRTIs.

A series of novel N-arylmethyl substituted piperidine-linked aniline derivatives were designed, synthesized and evaluated for their anti-HIV activity in MT-4 cells. All the new compounds showed moderate to potent activities against wild-type (wt) HIV-1 with an EC50 range from 0.022 to 2.1 µM. Among them, compound 5a6 (EC50=0.022 ± 0.0091 µM, SI >10,770) was confirmed to be the most potent and selective inhibitor, which proved more potent than DDI and DLV in a cell-based assay against wt HIV-1, and more efficient than NVP in an RT (reverse transcriptase) assay. Besides, it is worth noting that compound 7a1 retained moderate inhibitory activity (EC50=4.8 ± 0.95 µM) against the HIV-1 double RT mutant strain (K103N/Y181C). The preliminary structure-activity relationship was discussed and rationalized by molecular simulation.

HIV-1 NNRTIs: structural diversity, pharmacophore similarity, and implications for drug design.

Nonnucleoside reverse transcriptase inhibitors (NNRTIs) nowadays represent very potent and most promising anti-AIDS agents that specifically target the HIV-1 reverse transcriptase (RT). However, the effectiveness of NNRTI drugs can be hampered by rapid emergence of drug-resistant viruses and severe side effects upon long-term use. Therefore, there is an urgent need to develop novel, highly potent NNRTIs with broad spectrum antiviral activity and improved pharmacokinetic properties, and more efficient strategies that facilitate and shorten the drug discovery process would be extremely beneficial. Fortunately, the structural diversity of NNRTIs provided a wide space for novel lead discovery, and the pharmacophore similarity of NNRTIs gave valuable hints for lead discovery and optimization. More importantly, with the continued efforts in the development of computational tools and increased crystallographic information on RT/NNRTI complexes, structure-based approaches using a combination of traditional medicinal chemistry, structural biology, and computational chemistry are being used increasingly in the design of NNRTIs. First, this review covers two decades of research and development for various NNRTI families based on their chemical scaffolds, and then describes the structural similarity of NNRTIs. We have attempted to assemble a comprehensive overview of the general approaches in NNRTI lead discovery and optimization reported in the literature during the last decade. The successful applications of medicinal chemistry strategies, crystallography, and computational tools for designing novel NNRTIs are highlighted. Future directions for research are also outlined.

Novel piperidinylamino-diarylpyrimidine derivatives with dual structural conformations as potent HIV-1 non-nucleoside reverse transcriptase inhibitors.

A series of novel piperidinylamino-diarylpyrimidine (pDAPY) derivatives with dual structural conformations was designed through a molecular hybridization strategy and expected to bind into the non-nucleoside inhibitor binding pocket (NNIBP) of HIV-1 RT in a flexible manner. A cell-based antiviral screening assay showed that some compounds were active against both wild-type and drug-resistant mutant virus strains (K103N+Y181C RT) of HIV-1 (compound 10b3 with EC50 = 0.047 and 4.6 µM, selectivity index = 2145 and 22, respectively). Molecular simulation studies indicated that compound 10b3 could maintain the key hydrophobic interaction and hydrogen bonds with the NNIBP of two RT/ligand complexes. In particular, it could simultaneously occupy the protein/solvent interface and the entrance channel. Exploring these hybrid molecules with dual binding conformations might provide optional chemical scaffolds as novel HIV-1 reverse transcriptase inhibitors (HIV-1 NNRTIs).

Design, synthesis and biological evaluation of 3-benzyloxy-linked pyrimidinylphenylamine derivatives as potent HIV-1 NNRTIs.

A novel series of 3-benzyloxy-linked pyrimidinylphenylamine derivatives (8a-8s) was designed, synthesized and evaluated for their in vitro anti-HIV activity in MT-4 cell cultures. Most of the compounds inhibited wild-type (wt) HIV-1 replication in the lower micromolar concentration range (EC(50)=0.05-35 µM) with high selectivity index (SI) values (ranged from 10 to >4870). In particular, 8h and 8g displayed excellent antiretroviral activity against wt HIV-1 with low cytotoxicity (EC(50)=0.07 µM, CC(50) >347 µM, SI >4870; EC50=0.05 µM, CC(50)=42 µM, SI=777, respectively), comparable to that of the marked drug nevirapine (EC(50)=0.113 µM, CC(50) >15 µM, SI >133). In order to confirm the binding target, 8h was selected to perform the anti-HIV-1 RT assay. Additionally, preliminary structure activity relationship (SAR) analysis and molecular docking studies of newly synthesized compounds were also discussed, as well as the predicted physicochemical properties.

Structure-based bioisosterism design, synthesis and biological evaluation of novel 1,2,4-triazin-6-ylthioacetamides as potent HIV-1 NNRTIs.

The development of new HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs) offers the possibility of generating novel chemical entities of increased potency. Previous investigations in our laboratory resulted in the discovery of several novel series of arylazolylthioacetanilides as potent NNRTIs. In this study, based on the structure-based bioisosterism strategy, novel 1,2,4-triazin-6-yl thioacetamide derivatives were designed, synthesized and evaluated for their anti-HIV activity in MT-4 cells. Among them, the most promising compound was 8b15 with double-digit nanomolar activity against wild-type HIV-1 (EC(50)=0.018±0.007 µM) and moderate activity against the double mutant strain RES056 (EC(50)=3.3±0.1 µM), which indicated that 1,2,4-triazin-6-yl thioacetamide can be used as a novel scaffold to develop a new class of potent NNRTIs active against both wild-type and drug-resistant HIV-1 strains. In addition, preliminary structure-activity relationship (SAR) and molecular modeling results are also briefly discussed, which provide some useful information for the further design of novel NNRTIs.

Discovery of novel 2-(3-(2-chlorophenyl)pyrazin-2-ylthio)-N-arylacetamides as potent HIV-1 inhibitors using a structure-based bioisosterism approach.

The present work is an extension of our ongoing efforts towards the development and identification of new molecules with anti-HIV activity which have previously led to the discovery of arylazolylthioacetanilides as highly active NNRTIs. In this article, a series of 2-2-(3-(2-chlorophenyl)pyrazin-2-ylthio)-N-arylacetamide derivatives were synthesized and evaluated for in vitro anti-HIV activity. Most of the tested compounds exhibited moderate activities against wild-type HIV-1. Among them, compound 6k showed significant activity against wild-type HIV-1 with an EC(50) value of 1.7µM, along with moderate activity against wild-type reverse transcriptase (RT). The preliminary structure-activity relationship (SAR) and docking calculations of this new series of compounds were also investigated, which may help designing more potent molecules.

Arylazolyl(azinyl)thioacetanilides. Part 10: design, synthesis and biological evaluation of novel substituted imidazopyridinylthioacetanilides as potent HIV-1 inhibitors.

In continuation of our efforts toward the discovery of potent HIV-1 NNRTIs with novel structures, we have employed a scaffold hopping strategy to explore the chemically diversed space of bioactive compounds. The original arylazolylthioacetanilide platform was replaced with different imidazopyridinylthioacetanilide scaffolds to yield the optimal pharmacophore moieties in order to generate novel NNRTIs with desirable potency. Some of the new compounds proved able to inhibit HIV-1 replication in the low micromolar range. In particular, compound 5b16 displayed the most potent anti-HIV-1 activity (EC(50) = 0.21 ± 0.06 µM), inhibiting HIV-1 IIIB replication in MT-4 cells more effectively than dideoxycytidine (EC(50) = 1.4 ± 0.1 µM) and similarly with nevirapine (EC(50) = 0.20 ± 0.10 µM). Preliminary structure-activity relationship (SAR) of the newly synthesized congeners is discussed, and molecular modeling study is performed to rationalize the SAR conclusions.

Design, synthesis, anti-HIV evaluation and molecular modeling of piperidine-linked amino-triazine derivatives as potent non-nucleoside reverse transcriptase inhibitors.

A novel series of piperidine-linked amino-triazine derivatives were designed, synthesized and evaluated for in vitro anti-HIV activity as non-nucleoside reverse transcriptase inhibitors on the basis of our previous work. Screening results indicated that most compounds showed excellent activity against wild-type HIV-1 with EC(50) values in low nanomolar concentration range (especially compound 6b3, EC(50) = 4.61 nM, SI = 5945) and high activity against K103N/Y181C resistant mutant strain of HIV-1 with EC(50) values in low micromolar concentration range. In addition, preliminary structure-activity relationship and molecular modeling of these new analogs were detailed in this manuscript.

Selective MMP-13 Inhibitors: Promising Agents for the Therapy of Osteoarthritis.

Osteoarthritis (OA) is an age-related degenerative disease, which is characterized by chronic joint pain, inflammation and the damage of joint cartilage. At present, steroidal drugs and nonsteroidal anti-inflammatory drugs (NSAIDS), selective cyclooxygenase-2 (COX-2) inhibitors, are the first-line drugs for the treatment of OA. However, these drugs could lead to some cardiovascular side effects. Therefore, it is urgent to develop novel agents for the treatment of OA. Matrix metalloproteinase-13 (MMP-13), an important member of matrix metalloproteinases (MMPs) family, plays a vital role by degrading type II collagen in articular cartilage and bone in OA. It is noted that MMP-13 is specially expressed in the OA patients, and not in normal adults. In addition, broadspectrum MMP inhibitors could result in some painful and joint-stiffening side effects, called musculoskeletal syndrome (MSS) in the clinical trials. Thus, developing selective MMP-13 inhibitors is a potential strategy for the therapy of OA. In this review, we summarize the recent progress of selective MMP-13 inhibitors including two subfamilies, namely zinc-binding and non-zinc-binding selective MMP-13 inhibitors.

A simple and economical method of gas chromatography-mass spectrometry to determine the presence of 6 pesticides in human plasma and its clinical application in patients with acute poisoning.

An economical, rapid, and sensitive method of gas chromatography-mass spectrometry (GC-MS) was developed and validated to determine the presence of six pesticides (dichlorvos, acetochlor, atrazine, chlorpyrifos, α-endosulfan, and ß-endosulfan) in human plasma. The pesticides were extracted with acetonitrile and concentrated using anhydrous sodium sulfate. Then, the target compounds were analyzed and quantified with GC-MS using borneol as an internal standard. Separation was performed on a HP-5MS capillary column (30 m × 0.25 mm × 0.25 µm) with temperature programming. Detection was accomplished under electro-spray ionization (ESI) in selected ion monitoring (SIM) mode. Under optimized conditions, satisfactory linear ranges of 0.05-10 µg/mL were obtained for all of the analyzed pesticides. The linear correlation coefficients were greater than 0.99. The average recovery was between 86.8 and 106.5%. The inter- and intra-day precision ranged from 1.7-14.5% and 4.2-13.8%, respectively. Dichlorvos was unstable in plasma both at room temperature and when frozen. The other five pesticides were stable after storage at - 20°C for 17 days and two freeze-thaw cycles. Thirty-five plasma samples from 15 patients with acute self-poisoning were analyzed using this method. Dichlorvos was found in 13 plasma samples with a mean concentration of 0.289 µg/mL, and atrazine was found in 6 with a mean concentration of 0.261 µg/mL. Acetochlor was found in one plasma sample (0.153 µg/mL). This method is simple, reliable and cost-effective. It takes little time and does not waste solvents, and it can be used to routinely detect six pesticides in patients with acute poisoning.

Comparison of the docetaxel concentration in human plasma measured with liquid chromatography-tandem mass spectrometry (LC-MS/MS) and a nanoparticle immunoassay and clinical applications of that assay.

To determine the feasibility of using a nanoparticle immunoassay for clinical therapeutic drug monitoring (TDM) of docetaxel concentrations, a sensitive and simple method of liquid chromatography-tandem mass spectrometry (LC-MS/MS) was established to measure the docetaxel concentration in human plasma and the results of LC-MS/MS and the immunoassay were compared. Docetaxel and paclitaxel (the internal standard, or IS) in human plasma were extracted through protein precipitation, separated on a Diamonsil C18 column (150 mm × 4.6 mm, 5 µm), ionized with positive ions, and detected with LC-MS/MS in multi-reaction monitoring (MRM) mode. Plasma samples from 248 cancer patients were assayed with LC-MS/MS and a nanoparticle immunoassay. Data from the samples were analyzed with the statistical software SPSS and the software MedCalc. Results indicated that the calibration curve of the validated method of LC-MS/MS was linear over the range of 10-2,000 ng/mL, with an lowest limit of quantitation (LLOQ) of 10 ng/mL, and the intra- and inter- day precision and accuracy were both < ± 15%. Comparison of the two methods indicated that results of the LC-MS/MS were closely related to those of the nanoparticle immunoassay, with a correlation coefficient (R) of 0.965 and acceptable 95% confidence intervals (CI) of ‒ 231.7-331.1 ng/mL. Overall, the established method of LC-MC/MS and the nanoparticle immunoassay were both suitable for measurement of the docetaxel concentration in human plasma, and the immunoassay was far more cost-effective and better at clinical TDM of docetaxel in clinical practice.

Design, synthesis and evaluation of novel HIV-1 NNRTIs with dual structural conformations targeting the entrance channel of the NNRTI binding pocket.

On the basis of structure-based bioisosteric replacement and molecular hybridization strategy, a series of novel dual structural-conformation inhibitors targeting the "entrance channel" of HIV-1 NNRTIs binding pocket (NNIBP) were designed and synthesized. All of the new compounds were evaluated for their anti-HIV activities in MT-4 cells using the MTT method. Five compounds exhibited moderate to excellent potencies inhibiting wild-type (wt) HIV-1 replication with EC50 values ranging from 31.36 µM to 0.11 µM. Among them, compound 15b was identified as the most potent inhibitor with EC50 values of 0.11 µM and 2.18 µM against wt and K103N/Y181C double mutant HIV-1 strain (RES056), respectively. In addition, preliminary structure-activity relationships (SARs) and molecular simulation studies were discussed, which may provide valuable insights for further optimization.

Recent advance of the hepatitis B virus inhibitors: a medicinal chemistry overview.

Hepatitis B Virus (HBV) is one of the most prevalent viral infections of human worldwide. The therapies are limited in the clinical context because of negative side effects of interferons and the development of viral resistance to the nucleoside/nucleotide inhibitors. In this review, we summarize the recent advances in design and development of potent anti-HBV inhibitors from natural sources and synthetic compounds, targeting different steps in the life cycle of HBV. We attempt to emphasize the major structural modifications, mechanisms of action and computer-aided docking analysis of novel potent inhibitors that need to be addressed in the future to design potent anti-HBV molecules.

Design, Synthesis, and Anti-HIV Evaluation of Novel Triazine Derivatives Targeting the Entrance Channel of the NNRTI Binding Pocket.

A novel series of triazine derivatives targeting the entrance channel of the HIV-1 non-nucleoside reverse transcriptase inhibitor binding pocket (NNIBP) were designed and synthesized on the basis of our previous work. The results of a cell-based antiviral screening assay indicated that most compounds showed good-to-moderate activity against wild-type HIV-1 with EC50 values within the concentration range of 0.0078-0.16 µm (compound DCS-a4, EC50  = 7.8 nm). Some compounds displayed submicromolar activity against the K103N/Y181C resistant mutant strain (such as compound DCS-a4, EC50  = 0.65 µm). Molecular modeling studies confirmed that the new compounds could bind into the NNIBP similarly as the lead compound, and the newly introduced flexible heterocycles could occupy the entrance channel effectively. In addition, the preliminary structure-activity relationship and the RT inhibitory assay are presented in this study.

Recent advances of diaryl ether family as HIV-1 non-nucleoside reverse transcriptase inhibitors.

Diaryl ether family as one of the promising second generation HIV-1 non-nucleoside reverse transcriptase inhibitors has attracted considerable attention over the past few years, among which clinical candidate MK-4965 has been advanced into phase II clinical trials. The successful development of diaryl ether family provides valuable avenues in traditional medicinal chemistry, crystallography and computer-aided drug design fields for the design of other novel anti-HIV drug candidates. In this review, the development of diaryl ether family is present including the evolutionary history, design strategies, extensive structural modifications, structure-activity relationship studies and computer-aided molecular simulation of the binding mode in detail.

Discovery of piperidine-linked pyridine analogues as potent non-nucleoside HIV-1 reverse transcriptase inhibitors.

In our continued efforts to discover more active and less toxic HIV-1 non-nucleoside reverse transcriptase inhibitors, we recently designed a novel series of piperidine-linked pyridine analogues on the basis of diarylpyrimidine derivatives, among which two drugs-etravirine and rilpivirine-are approved for use by the US FDA. The title compounds were evaluated for activity against wild-type and resistant mutant strains of HIV-1 as well as HIV-2 in MT-4 cells. The highly potent compound BD-c1 (EC50 =10 nM, CC50 ≥146 µM, SI≥14 126) displays lower cytotoxicity and higher selectivity than etravirine (EC50 =2.2 nM, CC50 =28 µM, SI=12 884) against wild-type HIV-1. Compound BD-e2 (EC50 =5.1 nM) shows greater antiviral efficacy against wild-type HIV-1 than do the four reference drugs nevirapine, delavirdine, efavirenz, and zidovudine. Many compounds were also found to be active against the frequently observed drug-resistant double mutant (K103N+Y181C) HIV-1 strain. Herein we report the design, synthesis, anti-HIV evaluation, preliminary structure-activity relationships, and molecular simulations of novel piperidine-linked pyridine analogues.

Synthesis and biological evaluation of piperidine-substituted triazine derivatives as HIV-1 non-nucleoside reverse transcriptase inhibitors.

A novel series of piperidine-substituted triazine derivatives have been synthesized and evaluated for anti-HIV activities in MT-4 cells. Most compounds displayed extremely promising activity against wild-type HIV-1 with EC(50) values in low nanomolar concentration, better than that of Nevirapine, Delavirdine, Zidovudine and Dideoxycitidine, and higher potency towards the resistant mutant strain K103N/Y181C than that of Nevirapine and Delavirdine. Selected compounds were also assayed against reverse transcriptase with lower IC(50) values than that of Nevirapine. The structure-activity relationship (SAR) of these novel structural congeners was also discussed.

Arylazolyl(azinyl)thioacetanilide. Part 9: Synthesis and biological investigation of thiazolylthioacetamides derivatives as a novel class of potential antiviral agents.

In continuation of our endeavor to develop new, potent, selective and less toxic antiviral agents, a novel series of 2-(2-amino/chloro-4-(2,4-dibromophenyl) thiazol-5-ylthio)acetamide derivatives was synthesized via an expeditious route and evaluated for their anti-HIV activities against wild-type virus and clinically relevant mutant strains, and for their anti-influenza virus activities against influenza A (H1N1 and H3N2) and influenza B in cellular assays. The selected active compounds were also assayed for their enzymic inhibitory activities. The results showed that some 2-chloro substituted thiazolylthioacetamide derivatives possessed potent activity against wild type HIV-1 and several key mutant strains (E138K, K103N, L100I) of HIV-1 in MT-4 cells with EC(50) values in micromolar range. Two 2-amino substituted thiazole derivatives 8a7 and 8a8 displayed significant potency against influenza A/H1N1 in MDCK cells with EC(50) values much lower than that of oseltamivir carboxylate, ribavirin, amantadine and rimantadine. Though the mechanism of actions is still unclear, these novel thiazolylthioacetamides might serve as original leads for further pharmacological investigations as potential therapeutic agents against HIV-1 or influenza virus.

Functional roles of azoles motif in anti-HIV agents.

Currently, there has been considerable interest in the discovery of original molecules with broad-spectrum anti-HIV activity and favourable pharmacokinetic profiles, to be used as an alternative to the approved anti-HIV/AIDS drugs, should they fail as therapeutics. Five-membered azole heterocycles represent an important class of lead structures for novel anti-HIV drug development. They can serve as versatile building blocks to introduce different new functional groups, (i) as scaffolds to anchor these groups into the optimal space for interactions with the target, (ii) as basic pharmacophore elements to make hydrogen bonds or hydrophobic interaction for facilitating the spatial filling at the binding site, (iii) as ester surrogates to improve metabolic stability, or (iv) as pharmacophoric motif of metal coordination to coordinate metal ions (i.e. magnesium) within the active site of target (i.e. integrase). This article will summarize recent progress in the development of some azoles derivatives that inhibit the replication of HIV-1 and will illustrate the possible functional role(s) of the azole motif in the search for new anti-HIV drugs.