Combined comparative molecular field analysis,comparative molecular similarity indices analysis,molecular docking and molecular dynamics studies of histone deacetylase 6 inhibitors

Human histone deacetylase isoform 6 (HDAC6) has been shown to have an immense role in cell motility and aggresome formation and is being an attractive selective target for the treatment of multiple tumour types and neurodegenerative conditions. The discovery of selective HDAC6 inhibitors with new chemical functionalities is therefore of utmost interest to researchers. In order to examine the structural requirements for HDAC6‐specific inhibitors and to derive predictive model which can be used for designing new selective HDAC6 inhibitors, a three‐dimensional quantitative structure–activity relationship study was carried out on a diverse set of ligands using common feature‐based pharmacophore alignment followed by employing comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) techniques. The models displayed high correlation of 0.978 and 0.991 for best CoMFA and CoMSIA models, respectively, and a good statistical significance. The model could be used for predicting activities of the test set compounds as well as for deriving useful information regarding steric, electrostatic, hydrophobic properties of the molecules used in this study. Further, the training and test set molecules were docked into the HDAC6 binding site and molecular dynamics was carried out to suggest structural requirements for design of new inhibitors.     

HIV-1整合酶抑制剂体外筛选方法研究进展

整合酶是HIV基因表达和复制所必需的酶,而且宿主细胞内不存在该酶的类似物。因此,HIV-1整合酶已成为设计、筛选抗HIV药物的理想靶点。迄今为止,Raltegravir仍是唯一上市的HIV整合酶抑制剂,而且临床上也已经出现耐药问题。研发新一代整合酶抑制剂非常必要。高通量、高灵敏度、简单易行的筛选方法是研究开发新一代HIV-1整合酶抑制剂的关键。目前,HIV-1整合酶抑制剂筛选方法有多种,各有优缺点,该文将对文献报道的整合酶抑制剂体外筛选方法的最新进展做一介绍。     

3D-QSAR and molecular docking studies on substituted isothiazole analogs as inhibitors against MEK-1 kinase

MEK-1 and MEK-2 are dual-specificity kinases and important components in the mitogen-activated protein kinase pathway. These enzymes are crucial for normal cell survival and are also expressed in several types of cancers, making them important targets for drug design. We have applied an integrated in silico approach that combines comparative molecular field analysis, comparative molecular similarity indices analysis, and molecular docking to study the structural determinants for the recognition of substituted isothiazole analogs as allosteric inhibitors against MEK-1 kinase. The best 3D-QSAR models for comparative molecular field analysis and comparative molecular similarity indices analysis were selected based on statistical parameters. 3D contour maps suggested that bulky or long-chain substitutions at the X position on the core part decrease the inhibitory activity, and the presence of a hydrogen bond donor substitution enhances the activity. The bulky and electronegative substitutions at the Y position on the core part enhance the activity of the inhibitors. Molecular docking studies reveal a large and hydrophobic pocket that accommodates the Y substitution and a polar pocket that accommodates substitutions on the X position and forms hydrogen bonding interactions with MEK-1 kinase. The results of the 3D-QSAR analysis corroborate with the molecular docking results, and our findings will serve as a basis for further development of better allosteric inhibitors of MEK-1 kinase against several cancers.     

3D-QSAR studies on chromone derivatives as HIV-1 protease inhibitors: application of molecular field analysis

Three-dimensional quantitative structure-activity relationship (3D-QSAR) models were developed for chromone derivatives against HIV-1 protease using molecular field analysis (MFA) with genetic partial least square algorithms (G/PLS). Three different alignment methods: field fit, pharmacophore-based, and receptor-based were used to derive three MFA models. All models produced good predictive ability with high cross-validated r(2) (r(2) (cv)), conventional r(2), and predictive r(2)(r(2)(pred)) values. The receptor-based MFA showed the best statistical results with r(2) (cv) = 0.789, r(2)= 0.886, and r(2)(pred) = 0.995. The result obtained from the receptor-based model was compared with the docking simulation of the most active compound 21 in this chromone series to the binding pocket of HIV-1 protease (PDB entry 1AJX). It was shown that the MFA model related well with the binding structure of the complex and can provide guidelines to design more potent HIV-1 protease inhibitors.     

Pharmacophore development and docking studies of the hiv-1 integrase inhibitors derived from N-methylpyrimidones, Dihydroxypyrimidines, and bicyclic pyrimidinones

To elucidate the crucial structural features for the HIV-1 integrase inhibitors, a three-dimensional pharmacophore model was developed based on N-methyl pyrimidones, dihydroxypyrimidines, and bicyclic pyrimidinones derivatives using Phase. N-methyl pyrimidone derivative raltegravir, the first US-FDA approved drug by Merck, belongs to this series. The best-fitted common pharmacophore hypothesis was characterized by two acceptor, two hydrophobic, and two ring features having a correlation coefficient of 0.895, cross-validated Q(2) value of 0.631, and survival score of 8.862, suggesting that a highly predictive pharmacophore model was developed. The cross-validation studies using 23 test set molecules and fifteen structurally diverse HIV-integrase inhibitors give extra confidence about the correctness of the pharmacophore model. The cross-validation studies proved that our developed model can successfully differentiate between active and inactive HIV-integrase inhibitors. The docking studies were also carried out wherein the molecules were docked against the active site of HIV integrase to analyze the binding mode and the necessary structural requirement for their respective enzymatic inhibition. The results obtained from our studies provide a valuable tool for designing of new lead molecules with potent activity.     

In silico screening for identification of novel HIV-1 integrase inhibitors using QSAR and docking methodologies

Human immunodeficiency virus-1 integrase (HIV-1 IN) is an important target for HIV-1 infection. Here, shape based screening workflow was designed to discover novel inhibitors against HIV-1 IN protein. The best docked conformation of highly active curcumine molecule 32 (Gupta et al. Mol Diversity 15:733–750, 2011) was used as a template for screening of drug-like databases. The screened molecules were filtered out using toxicity studies. The in silico inhibitory activity of screened molecules against HIV-1 IN was predicted using 2D (Gupta et al. Curr Comput Aided Drug Des 9:141–150, 2013) and 3D (Gupta et al. Mol Diversity 15:733–750, 2011) QSAR models. Subsequently, putative binding modes of these molecules were investigated using different docking algorithms. Some of the molecules exhibited similar poses in both the algorithms and fulfilled the criteria for the best docking pose. Eventually, 11 novel scaffolds were identified from the designed workflow. These screened molecules could be potential hits against HIV-1 IN. These combined techniques were facilitated here to get different scaffolds with good ADMET, QSAR, and docking predictions, which can be further explored for lead optimization purpose. Besides, these scaffolds can be a good starting point for researchers for designing of new molecules against HIV-1 IN.     

Identification of novel HIV-1 integrase inhibitors using shape-based screening, QSAR, and docking approach

The objective of this study is to identify novel HIV‐1 integrase (IN) inhibitors. Here, shape‐based screening and QSAR have been successfully implemented to identify the novel inhibitors for HIV‐1 IN, and in silico validation is performed by docking studies. The 2D QSAR model of benzodithiazine derivatives was built using genetic function approximation (GFA) method with good internal (cross‐validated r² = 0.852) and external prediction (). Best docking pose of highly active molecule of the benzodithiazine derivatives was used as a template for shape‐based screening of ZINC database. Toxicity prediction was also performed using Deductive Estimation of Risk from Existing Knowledge (DEREK) program to filter non‐toxic molecules. Inhibitory activities of screened non‐toxic molecules were predicted using derived QSAR models. Active, non‐toxic screened molecules were also docked into the active site of HIV‐1 IN using Auto Dock and dock program. Some molecules docked similarly as highly active molecule of the benzodithiazine derivatives. These molecules also followed the same docking interactions in both the programs. Finally, four benzodithiazine derivatives were identified as novel HIV‐1 integrase inhibitors based on QSAR predictions and docking interactions. ADME properties of these molecules were also computed using Discovery Studio.     

3D-QSAR studies of JNK1 inhibitors utilizing various alignment methods

We report our three-dimensional quantitative structure activity relationship (3D-QSAR) studies of the series of anilinopyrimidine derivatives of JNK1 inhibitors. The comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were applied using different alignment methods. The ligand-based atom-by-atom matching alignment has produced better values for CoMFA (q(2) = 0.646 and r(2) = 0.983), while in CoMSIA it has achieved only lower statistical values. The pharmacophore-based model has produced (q(2) = 0.568, r(2) = 0.938) and (q(2) = 0.670, r(2) = 0.982) for CoMFA and CoMSIA models, respectively. As the model was based on the receptor-guided alignment, all the compounds were optimized within the receptor, resulting in q(2) = 0.605 and r(2) = 0.944 for CoMFA, and q(2) = 0.587 and r(2) = 0.863 for CoMSIA. Molecular Dynamic simulation studies suggested that the generated models were consistent with the low-energy protein ligand conformation. The CoMFA and CoMSIA contour maps indicated that the substitutions of the electropositive groups in the phenyl ring, and an addition of hydrophobic groups in the pyrimidine ring, are important to enhance the activity of this series. Moreover, the virtual screening analysis against NCI database yields potentials hits, and the results obtained would be useful to synthesize selective and highly potent c-Jun N-terminal kinase 1 analogs.     

Studies of metabolism and disposition of potent human immunodeficiency virus (HIV) integrase inhibitors using 19F-NMR spectroscopy

¹⁹F-nuclear magnetic resonance (NMR) has been extensively used in a drug-discovery programme to support the selection of candidates for further development. Data on an early lead compound, N-(4-fluorobenzyl)-5-hydroxy-1-methyl-2-(4-methylmorpholin-3-yl)-6-oxo-1,6-dihydropyrimidine-4-carboxamide (compound A (+)), and MK-0518 (N-(4-fluorobenzyl)-5-hydroxy-1-methyl-2-(1-methyl-1-{[(5-methyl-1,3,4-oxadiazol-2-yl)carbonyl]amino}ethyl)-6-oxo-1,6-dihydropyrimidine-4-carboxamide), a potent inhibitor of this series currently in phase III clinical trials, are described. The metabolic fate and excretion balance of compound A (+) and MK-0518 were investigated in rats and dogs following intravenous and oral dosing using a combination of ¹⁹F-NMR-monitored enzyme hydrolysis and solid-phase extraction chromatography and NMR spectroscopy (SPEC-NMR). Dosing with the ³H-labelled compound A (+) enabled the comparison of standard radiochemical analysis with ¹⁹F-NMR spectroscopy to obtain quantitative metabolism and excretion data. Both compounds were eliminated mainly by metabolism. The major metabolite identified in rat urine and bile and in dog urine was the 5-O-glucuronide.     

采用药效团模型和分子对接方法筛选新型的组蛋白甲基转移酶G9a抑制剂

目的利用药效团模型和分子对接方法对商业化合物库ChemDiv中的G9afocused-libraries进行筛选,希望发现新骨架结构的G9a抑制剂。方法首先,使用Discovery studio 3.1软件分别构建基于配体的药效团模型和基于配体-受体复合物的药效团模型,并根据构建的2个模型再重新定义2个新的药效团模型。然后,构建测试集并测试药效团模型的预测能力。最后,选取最优药效团模型对G9afocused-libraries进行筛选,对筛选出的化合物使用CDOCKER分子对接进行分析与评价。结果测试结果显示,所构建的药效团模型具有一定的预测能力,通过该药效团筛选得到了2个结构新颖的潜在的G9a抑制剂。结论所构建的药效团模型具有一定的可靠性,虚拟筛选发现的G9a抑制剂还需进一步的实验证明。     

Identification of promising DNA GyrB inhibitors for Tuberculosis using pharmacophore‐based virtual screening,molecular docking and molecular dynamics studies

In this study, we searched for potential DNA GyrB inhibitors using pharmacophore‐based virtual screening followed by molecular docking and molecular dynamics simulation approaches. For this purpose, a set of 248 DNA GyrB inhibitors was collected from the literature and a well‐validated pharmacophore model was generated. The best pharmacophore model explained that two each of hydrogen bond acceptors and hydrophobicity regions were critical for inhibition of DNA GyrB. Good statistical results of the pharmacophore model indicated that the model was robust in nature. Virtual screening of molecular databases revealed three molecules as potential antimycobacterial agents. The final screened promising compounds were evaluated in molecular docking and molecular dynamics simulation studies. In the molecular dynamics studies, RMSD and RMSF values undoubtedly explained that the screened compounds formed stable complexes with DNA GyrB. Therefore, it can be concluded that the compounds identified may have potential for the treatment of TB.     

Computer-aided design of selective COX-2 inhibitors: comparative molecular field analysis,comparative molecular similarity indices analysis,and docking studies of some 1,2-diarylimidazole derivatives

Comparative molecular field analysis and comparative molecular similarity indices analysis were performed on 114 analogues of 1,2-diarylimidazole to optimize their cyclooxygenase-2 (COX-2) selective antiinflammatory activities. These studies produced models with high correlation coefficients and good predictive abilities. Docking studies were also carried out wherein these analogues were docked into the active sites of both COX-1 and COX-2 to analyze the receptor ligand interactions that confer selectivity for COX-2. The most active molecule in the series (53) adopts an orientation similar to that of SC-558 (4-[5-(4-bromophenyl)-3-trifluoromethyl-1H-1-pyrozolyl]-1-benzenesulfonamide) inside the COX-2 active site while the least active molecule (101) optimizes in a different orientation. In the active site, there are some strong hydrogen-bonding interactions observed between residues His90, Arg513, and Phe518 and the ligands. Additionally, a correlation of the quantitative structure-activity relationship data and the docking results is found to validate each other and suggests the importance of the binding step in overall drug action.     

Targeting HIV-1 through molecular modeling and docking studies of CXCR4: leads for therapeutic development

The chemokine receptor CXCR4 is the receptor for several chemokines and major co-receptor for X4 human immunodeficiency virus type-1 strains entry into cell. A three-dimensional model of human CXCR4 was developed by homology modeling using the high-resolution bovine rhodopsin structure as template. Interactions between CXCR4 and flavonoids were investigated using in silico docking studies. The results underscore the potential of these compounds that they may become important new antiviral drugs to combat AIDS. It is worth mentioning also that apart from these existing flavonoids, there are many new compounds that may also be useful as topical agents to inactivate virus, or may act as adjuvants with other antiviral drugs.     

Comparative molecular field analysis (CoMFA), topomer CoMFA,and hologram QSAR studies on a series of novel HIV‐1 protease inhibitors

Comparative molecular field analysis (CoMFA), topomer CoMFA, and hologram QSAR as three efficient methods of QSAR have been performed on 40 newly synthesized inhibitors against HIV‐1 protease. Molecular alignment was performed by aid of crystallographic structure of template inhibitor (indirect alignment) and also by the molecular mechanic (MM)‐minimized structure. Both alignment methods produced satisfactory statistics for training set, but indirect alignment had more predictive power. Generated counter maps, especially by topomer CoMFA, give comprehensive information about structural features affecting the inhibitory activities of studied chemicals. Based on the obtained information, some new inhibitors were suggested.     

Synthesis and comparative molecular field analysis (CoMFA) of symmetric and nonsymmetric cyclic sulfamide HIV-1 protease inhibitors

We have previously reported on the unexpected flipped conformation in the cyclic sulfamide class of inhibitors. An attempt to induce a symmetric binding conformation by introducing P2/P2' substituents foreseen to bind preferentially in the S2/S2' subsite was unsuccessful. On the basis of the flipped conformation we anticipated that nonsymmetric sulfamide inhibitors, with P2/P2' side chains modified individually for the S1' and S2 subsites, should be more potent than the corresponding symmetric analogues. To test this hypothesis, a set of 18 cyclic sulfamide inhibitors (11 nonsymmetric and 7 symmetric) with different P2/P2' substituents was prepared and evaluated in an enzyme assay. To rationalize the structure-activity relationship (SAR) and enable the alignment of the nonsymmetric inhibitors, i.e., which of the P2/P2' substituents of the nonsymmetric inhibitors interact with which subsite, a CoMFA study was performed. The CoMFA model, constructed from the 18 inhibitors in this study along with seven inhibitors from previous work by our group, has successfully been used to rationalize the SAR of the cyclic sulfamide inhibitors. Furthermore, from the information presented herein, the SAR of the cyclic sulfamide class of inhibitors seems to differ from the SAR of the related cyclic urea inhibitors reported by DuPont and DuPont-Merck.