Synthesis and Biological Evaluation of Novel Multi-target-Directed Benzazepines Against Excitotoxicity.

Excitotoxicty, a key pathogenic event is characteristic of the onset and development of neurodegeneration. The glutamatergic neurotransmission mediated through different glutamate receptor subtypes plays a pivotal role in the onset of excitotoxicity. The role of NMDA receptor (NMDAR), a glutamate receptor subtype, has been well established in the excitotoxicity pathogenesis. NMDAR overactivation triggers excessive calcium influx resulting in excitotoxic neuronal cell death. In the present study, a series of benzazepine derivatives, with the core structure of 3-methyltetrahydro-3H-benzazepin-2-one, were synthesised in our laboratory and their NMDAR antagonist activity was determined against NMDA-induced excitotoxicity using SH-SY5Y cells. In order to assess the multi-target-directed potential of the synthesised compounds, Aß1-42 aggregation inhibitory activity of the most potent benzazepines was evaluated using thioflavin T (ThT) and Congo red (CR) binding assays as Aß also imparts toxicity, at least in part, through NMDAR overactivation. Furthermore, neuroprotective, free radical scavenging, anti-oxidant and anti-apoptotic activities of the two potential test compounds (7 and 14) were evaluated using primary rat hippocampal neuronal culture against Aß1-42-induced toxicity. Finally, in vivo neuroprotective potential of 7 and 14 was assessed using intracerebroventricular (ICV) rat model of Aß1-42-induced toxicity. All of the synthesised benzazepines have shown significant neuroprotection against NMDA-induced excitotoxicity. The most potent compound (14) showed relatively higher affinity for the glycine binding site as compared with the glutamate binding site of NMDAR in the molecular docking studies. 7 and 14 have been shown experimentally to abrogate Aß1-42 aggregation efficiently. Additionally, 7 and 14 showed significant neuroprotective, free radical scavenging, anti-oxidant and anti-apoptotic properties in different in vitro and in vivo experimental models. Finally, 7 and 14 attenuated Aß1-42-induced tau phosphorylation by abrogating activation of tau kinases, i.e. MAPK and GSK-3ß. Thus, the results revealed multi-target-directed potential of some of the synthesised novel benzazepines against excitotoxicity.

Benzo[e]pyrimido[5,4-b][1,4]diazepin-6(11H)-one derivatives as Aurora A kinase inhibitors: LQTA-QSAR analysis and detailed systematic validation of the developed model.

Aurora kinases are sub-divided into Aurora A, Aurora B, and Aurora C kinases that are considered as prospective targets for a new class of anticancer drugs. In this work, a 4-D-QSAR model using an LQTA-QSAR approach with previously reported 31 derivatives of benzo[e]pyrimido[5,4 -b][1,4]diazepin -6(11H)-one as potent Aurora kinase A inhibitors has been created. Instead of single conformation, the conformational ensemble profile generated for each ligand by using trajectories and topology information retrieved from molecular dynamics simulations from GROMACS package were aligned and used for the calculation of intermolecular interaction energies at each grid point. The descriptors generated on the basis of these Coulomb and Lennard-Jones potentials as independent variables were used to perform a PLS analysis using biological activity as dependent variable. A good predictive model was generated with nine field descriptors and five latent variables. The model showed [Formula: see text]; [Formula: see text] and [Formula: see text]. This model was further validated systematically by using different validation parameters. This 4D-QSAR model gave valuable information to recognize features essential to adapt and develop novel potential Aurora kinase inhibitors.

Discovery of isoalloxazine derivatives as a new class of potential anti-Alzheimer agents and their synthesis.

This article describes discovery of a novel and new class of cholinesterase inhibitors as potential therapeutics for Alzheimer's disease. A series of novel isoalloxazine derivatives were synthesized and biologically evaluated for their potential inhibitory outcome for both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). These compounds exhibited high activity against both the enzymes AChE as well as BuChE. Of the synthesized compounds, the most potent isoalloxazine derivatives (7m and 7q) showed IC50 values of 4.72 µM and 5.22 µM respectively against AChE; and, 6.98 µM and 5.29 µM respectively against BuChE. These two compounds were further evaluated for their anti-aggregatory activity for ß-amyloid (Aß) in presence and absence of AChE by performing Thioflavin-T (ThT) assay and Congo red (CR) binding assay. In order to evaluate cytotoxic profile of these two potential compounds, cell viability assay of SH-SY5Y human neuroblastoma cells was performed. Further, to understand the binding behavior of these two compounds with AChE and BuChE enzymes, docking studies have been reported.

Synthesis and biological evaluation of some novel pyrido[1,2-a]pyrimidin-4-ones as antimalarial agents.

Novel pyrido[1,2-a]pyrimidin-4-ones have been synthesized and evaluated for their antimalarial activity by SYBR Green I assay against erythrocytic stages of chloroquine (CQ) sensitive Pf 3D7 strain. The antimalarial screening of 42 different compounds revealed that 3-Fluorobenzyl(4-oxo-4H-pyrido [1,2-a]pyrimidin-3-yl)carbamate (21, IC50 value 33 µM) and 4-Oxo-N-[4-(trifluoromethyl)benzyl]-4H-pyrido[1,2-a]pyrimidine-3-carboxamide (37, IC50 value 37 µM) showed moderate antimalarial activity. Cytotoxicity study was performed against mammalian cell line (Huh-7) by using the MTT assay for the moderately active compounds. Structural activity relationship (SAR) studies displayed that B-ring unsubstituted pyrido[1,2-a]pyrimidine scaffold is responsible for the antimalarial activities of the evaluated derivatives. This SAR based antimalarial screening supported that pyrido[1,2-a]pyrimidin-4-one can be considered as a lead heterocyclic structure for further development of more potent derivatives for antimalarial activity.

Novel methods and strategies in the discovery of TACE inhibitors.

INTRODUCTION: Tumor necrosis factor-α (TNF-α) is a key player in inflammation and joint damage in rheumatoid arthritis (RA). One treatment approach to exclude TNF-α from the biological system is by inhibiting tumor necrosis factor-alpha converting enzyme (TACE), the enzyme responsible for the production of its active form. To date, a number of TACE inhibitors have been reported in the literature from various strategies and methods. AREAS COVERED: The following article presents the design and development strategies for the discovery of novel TACE inhibitors which could be of therapeutic utility for the alleviation of inflammatory conditions. The review is based on literature of the subject from 2005 onward. EXPERT OPINION: Discovery of a selective TACE inhibitor has remained a major goal for many academic and pharmaceutical industrial research laboratories for quite some time. Identification of selective TACE inhibitors has proved elusive until recently due to structural similarities between TACE and MMPs. The differences in the shape and size of the S1' pocket of TACE and MMPs could be exploited to design selective TACE inhibitors devoid of any MMP inhibitory activity in the near future. It would be a Herculean task to develop a specific TACE inhibitor for clinical treatment of RA because binding subsites of TACE and MMPs are quite similar. However, developments taking place currently in the field as well as in the application of molecular modeling techniques at a wider scale could yet provide clinically useful selective TACE inhibitors in the not too distant future.

Falcipain inhibitors as potential therapeutics for resistant strains of malaria: a patent review.

INTRODUCTION: There is an urgent need to discover new antimalarial drugs due to emergence of resistance in the parasite to the existing drugs. Malarial cysteine proteases falcipin-2 (FP-2) and falcipain-3 (FP-3) are attractive targets for antimalarial chemotherapy. The structures and functions of FP-2/3, their binding domains and their interactions with small- and macro-molecules are well studied. These studies could provide important insight into rational designing of FP inhibitors as potential antimalarial drugs. AREAS COVERED: This review is focused on a selection of interesting patents published during 1999 - 2011 on peptidic and nonpeptidic chemotypes of the FP-2/FP-3 inhibitors. EXPERT OPINION: It is a known fact that malaria is a serious health problem worldwide due to the emergence of resistant strains. Hence, development of novel, potent and affordable antimalarial drugs devoid of side effects is of great significance and in great demand. FPs, the malarial cysteine proteases are potential targets for development of new antimalarial drugs. Assessing the available literature on FP-2/3 and their inhibitors it could be speculated that these inhibitors have the potential to enter the clinical stages of development for the treatment of malaria in the years to come.

Steroidal carbonitriles as potential aromatase inhibitors.

Estrogens, responsible for the growth of hormone-dependant breast cancer are biosynthesized from androgens involving aromatase enzyme in the last rate limiting step. Inhibition of aromatase is an efficient approach for the prevention and treatment of breast cancer. Novel 4-phenylthia derivatives (2, 3 and 7) have been synthesized as aromatase inhibitors. The synthesized compounds (2, 3 and 7) exhibited noticeable enzyme inhibiting activity. Kinetics study of these compounds (2, 3, and 7) showed negligible inhibition of the enzyme under conditions conducive for irreversible inhibition of the enzyme. Introduction of unsaturation at C-4, C-1 & 4 or C-4 & 6 (compounds 5, 9 and 11) was observed to not be an effective strategy for entrancing aromatase inhibiting activity in 17-oxo-16ß-carbonitrile derivatives. The D-seco derivatives (13-15 and 17) having unsaturation at C-4, C-1 & 4 or C-4 & 6 along with carbonitrile function in ring-D showed complete loss of aromatase inhibiting activity.

Cytotoxic potential of novel 6,7-dimethoxyquinazolines.

Herein, we report the synthesis and cytotoxicity of a series of substituted 6,7-dimethoxyquinazoline derivatives. The cytotoxic activity of all synthesized compounds has been evaluated against HCT116p53(+/+) and HCT116p53(-/-) colon cancer cells and a HEY ovarian cancer cell line naturally resistant to cisplatin. Nine of the tested compounds showed significant cytotoxicity in all cell lines at 10µM. The most promising derivative (7c) showed IC(50)values of 0.7 and 1.7µM in the two colon cancer cell lines.

Development of highly predictive 3D-QSAR CoMSIA models for anthraquinone and acridone derivatives as telomerase inhibitors targeting G-quadruplex DNA telomere.

G-quadruplex structures of DNA represent a potentially useful target for anticancer drugs. Telomerase enzyme, involved in immortalization of cancer cells is inhibited by stabilization of G-quadruplex at the ends of chromosomes. Anthraquinone and acridone derivatives are promising G-quadruplex ligands as telomerase inhibitors. So far, optimization of these ligands remained hampered due to the lack of creditable quantitative structure-activity relationships. To understand the structural basis of anthraquinone and acridone derivatives, a predictive 3D-QSAR model has been developed for the first time for telomerase inhibitory activity of G4 ligands, employing comparative molecular similarity indices analysis (CoMSIA). Considering the proposition that the basic nitrogens in these compounds should exist in protonated form at physiological pH the protonated forms of the reported compounds were analyzed and investigated. The QSAR model from conformational template Conf1 exhibited best correlative and predictive properties. The actual predictive abilities of the QSAR model were thoroughly validated through an external validation test set of compounds. The statistics indicate a significantly high prediction power of the best model (r(2), 0.721), supporting the proposed molecular mechanism of DNA G-quadruplex ligands.

Novel TACE inhibitors in drug discovery: a review of patented compounds.

TNF-alpha converting enzyme (TACE), a pro-inflammatory cytokine, catalyzes the formation of TNF-alpha from membrane bound TNF-alpha precursor protein. TNF-alpha is believed to play pathophysiological roles in inflammation, anorexia, cachexia, septic shock, viral replication and so on. TNF-alpha is a key player in inflammation and joint damage in rheumatoid arthritis. While a variety of TACE inhibitors have been reported in the literature, a vast majority of these compounds are peptidic and peptide-like compounds that are expected to have bioavailability and pharmacokinetic problems, common to such compounds, limiting their clinical effectiveness. Low molecular mass, long acting, orally bioavailable inhibitors of TACE are, therefore, highly desirable for the treatment of potential chronic diseases mentioned above. A review of patented compounds as TACE inhibitors in drug discovery is given. A selection of interesting patents recorded from 2001 to 2009 is presented. Various novel TACE inhibitors developed by different companies have been discussed.

Synthesis and anti-HIV-1 integrase activity of cyano pyrimidinones.

A series of 2-phenethyl/benzylthio-6-oxo-4-phenyl-1,6-dihydropyrimidine-5-carbonitrile were synthesized and tested against recombinant HIV-1 integrase in an enzyme assay. 2-(Phenethylthio)-4-(4-chlorophenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile 4m and 2-(phenethylthio)-4-(3-chlorophenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile 4o showed significant inhibition against integrase in the assay (strand transfer: IC(50) values of 16 and 17 microM, respectively).

Structural investigations of acridine derivatives by CoMFA and CoMSIA reveal novel insight into their structures toward DNA G-quadruplex mediated telomerase inhibition and offer a highly predictive 3D-model for substituted acridines.

Stabilization of G-quadruplex structures formed from telomeric DNA, by means of G-quadruplex selective ligands, is a means of inhibiting the telomerase enzyme. This makes G-quadruplex an emerging target for cancer therapy. The objective of the current 3D QSAR study is to uncover structural requirements for acridine derivatives, which would eventually assist and complement the rational drug-design attempts. Various protonation strategies were investigated to check in situ protonation sites present on ligands when they bind to G-quadruplex, and predictive 3D-QSAR CoMFA and CoMSIA models have been developed. Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) studies were carried out on substituted acridines as telomerase inhibitors. Molecular models with good predictive power were derived using steric, electrostatic, hydrophobic, and H-bond donor fields of the compounds. The CoMSIA coefficient contour plots identified several key features explaining the wide range in activities. The present study not only offers a highly significant predictive CoMSIA model for trisubstituted acridine derivatives as telomerase inhibitors but also throws more light on the molecular structure of these compounds at physiological pH.

Studies on novel 2-imidazolidinones and tetrahydropyrimidin-2(1H)-ones as potential TACE inhibitors: design, synthesis, molecular modeling, and preliminary biological evaluation.

Compounds belonging to the class of 2-imidazolidinones and tetrahydropyrimidin-2(1H)-ones were synthesized and evaluated for their TACE inhibitory activity. Most of the compounds showed very good TACE inhibitory activity. Docking study clearly indicates importance of the P1' group of the inhibitor for the TACE inhibitory activity. This work proves that these two classes of molecules could be used as potential leads for the development of TACE inhibitors.

Development of predictive 3D-QSAR CoMFA and CoMSIA models for beta-aminohydroxamic acid-derived tumor necrosis factor-alpha converting enzyme inhibitors.

A three-dimensional quantitative structure-activity relationship study was performed on a series of beta-aminohydroxamic acid-derived tumor necrosis factor-alpha converting enzyme inhibitors employing comparative molecular field analysis and comparative molecular similarity indices analysis techniques to investigate the structural requirements for the inhibitors, and derive a predictive model that could be used for the design of novel tumor necrosis factor-alpha converting enzyme inhibitors. log P was used as an additional descriptor in the comparative molecular field analysis analysis to study the effects of lipophilic parameters on activity. Inclusion of log P did not improve the models significantly. The statistically significant model was established with 45 molecules, which were validated by a test set of 11 compounds. Ligand molecular superimposition on the template structure was performed by the atom-/shape-based root mean square fit and database alignment methods. Docked conformer based alignment (V) yielded the best predictive comparative molecular field analysis model = 0.673, = 0.860, F-value = 86.073, predictive r (2) = 0.642, with two components, standard error of prediction = 0.394 and standard error of estimates = 0.243 while the comparative molecular similarity indices analysis model yielded = 0.635, = 0.858, F-value = 84.451, predictive r (2) = 0.441 with three components, standard error of prediction = 0.393 and standard error of estimates = 0.245. The contour maps obtained from three-dimensional quantitative structure-activity relationship studies were appraised for activity trends for the molecules analyzed. The comparative molecular field analysis models exhibited good external predictivity as compared with that of comparative molecular similarity indices analysis models. The model generated through comparative molecular field analysis was validated with the IK-682. The data generated from this study may guide our efforts in designing and predicting the tumor necrosis factor-alpha converting enzyme inhibitory activity of novel molecules.

Current perspective of TACE inhibitors: a review.

Rheumatoid Arthritis (RA) is one of the most common autoimmune inflammatory conditions, affecting approximately 1% of the adult population worldwide. TNF-alpha is a pleitropic, pro-inflammatory cytokine which plays a pivotal role in the origin and progression of RA and other immune mediated disorders. The success of anti-TNF-alpha biological agents proved that inhibition of TNF-alpha could result in effective control of RA. Since the discovery of anti-TNF-alpha biologicals, much efforts have gone into developing an orally bioavailable small size TNF-alpha antagonist. One of the ways to block TNF-alpha in biological fluids is to inhibit TNF-alpha converting enzyme (TACE). This target has been validated in preclinical trials using TACE inhibitors. But, even after more than a decade no single TACE inhibitor has passed the Phase II clinical trials. Very recently, it has been shown that TACE inhibitors could also be used for inhibition of pathogenic EGFR signaling in cancer. Hence, TACE inhibitors could perform a dual role, in curing not only RA but also certain cancerous conditions. Developments in the field have prompted us to review the research work on TACE inhibitors, especially their structure activity relationships and molecular modeling studies.

Peptidomimetic 2-cyanopyrrolidines as potent selective cathepsin L inhibitors.

Cathepsins have been found to have important physiological roles. The implication of cathepsin L in various types of cancers is well established. In a search for selective cathepsin L inhibitors as anticancer agents, a series of 2-cyanoprrolidine peptidomimetics, carrying a nitrile group as warhead, were designed. Two series of compounds, one with a benzyl moiety and a second with an isobutyl moiety at P(2) position of the enzyme were synthesized. The synthesized compounds were evaluated for inhibitory activity against human cathepsin L and cathepsin B. Although, none of the compounds showed promising inhibitory activity, (E)N-{(S)1-[(S)2-cyano-1-pyrrolidinecarbonyl]-3-methylbutyl}-2,3-diphenylacrylamide (24) with an isobutyl moiety at P(2) was found to show selectivity as a cathepsin L inhibitor (Ki 5.3 microM for cathepsin L and Ki > 100 microM for cathepsin B). This compound could act as a new lead for the further development of improved inhibitors within this inhibitor type.

3D-quantitative structure-activity relationship studies on benzothiadiazepine hydroxamates as inhibitors of tumor necrosis factor-alpha converting enzyme.

A set of 29 benzothiadiazepine hydroxamates having selective tumor necrosis factor-alpha converting enzyme inhibitory activity were used to compare the quality and predictive power of 3D-quantitative structure-activity relationship, comparative molecular field analysis, and comparative molecular similarity indices models for the atom-based, centroid/atom-based, data-based, and docked conformer-based alignment. Removal of two outliers from the initial training set of molecules improved the predictivity of models. Among the 3D-quantitative structure-activity relationship models developed using the above four alignments, the database alignment provided the optimal predictive comparative molecular field analysis model for the training set with cross-validated r(2) (q(2)) = 0.510, non-cross-validated r(2) = 0.972, standard error of estimates (s) = 0.098, and F = 215.44 and the optimal comparative molecular similarity indices model with cross-validated r(2) (q(2)) = 0.556, non-cross-validated r(2) = 0.946, standard error of estimates (s) = 0.163, and F = 99.785. These models also showed the best test set prediction for six compounds with predictive r(2) values of 0.460 and 0.535, respectively. The contour maps obtained from 3D-quantitative structure-activity relationship studies were appraised for activity trends for the molecules analyzed. The comparative molecular similarity indices models exhibited good external predictivity as compared with that of comparative molecular field analysis models. The data generated from the present study helped us to further design and report some novel and potent tumor necrosis factor-alpha converting enzyme inhibitors.

Synthesis, antileukemic and antiplatelet activities of 2,3-diaryl-6,7-dihydro-5H-1,4-diazepines.

The synthesis, antileukemic and antiplatelet activity evaluation of 2,3-diaryl-6,7-dihydro-5H-1,4-diazepines are described. In general, it was found that compound 17o showed moderate antileukemic activity against MOLT3 human leukemic cancer cell lines. An arachidonic acid induced platelet aggregation effect on washed rat platelets was studied. Compound 17i was found to be the most potent. The antiplatelet properties may be mediated by interference with the arachidonic acid pathway.

Insights into the structural requirements of farnesyltransferase inhibitors as potential anti-tumor agents based on 3D-QSAR CoMFA and CoMSIA models.

A three-dimensional quantitative structure-activity relationship (3D-QSAR) study was performed on three different chemical series reported as selective farnesyltransferase (FTase) inhibitors employing comparative molecular field analysis (CoMFA) and comparative molecular similarity indices (CoMSIA) techniques to investigate the structural requirements for substrates and derive a predictive model that may be used for the design of novel FTase inhibitors. Removal of outliers improved the predictive power of models developed for all three structurally diverse classes of compounds. 3D-QSAR models were derived for 3-aminopyrrolidinone derivatives (training set N=38, test set N=7), 2-amino-nicotinonitriles (training set N=46, test set N=13) and 1-aryl-1'-imidazolyl methyl ethers (training set N=35, test set N=5). The CoMFA models with steric and electrostatic fields exhibited r(2)(cv) 0.479-0.803, r(2)(ncv) 0.945-0.993, r(2)(pred) 0.686-0.811. The CoMSIA models displayed r(2)(cv) 0.411-0.814, r(2)(ncv) 0.923-0.984, r(2)(pred) 0.399-0.787. 3D contour maps generated from these models were analyzed individually, which provide the regions in space where interactive fields may influence the activity. The superimposition of contour maps on the active site of farnesyltransferase additionally helps in understanding the structural requirements of these inhibitors. 3D-QSAR models developed may guide our efforts in designing and predicting the FTase inhibitory activity of novel molecules.

Inhibition of farnesyltransferase: a rational approach to treat cancer?

This article presents in brief the development of farnesyltransferase inhibitors (FTIs) and their preclinical and clinical status. In this review the mechanism of action of FTIs is discussed and their selectivity issue towards tumor cells is also addressed. The significant efficacy of FTIs as single or combined agents in preclinical studies stands in contrast with only moderate effects in Clinical Phase II-III studies. This suggests that there is a need to further explore and understand the complex mechanism of action of FTIs and their interaction with cytotoxic agents.