In silico-guided discovery and in vitro validation of novel sugar-tethered lysinated carbon nanotubes for targeted drug delivery of doxorubicin.

CONTEXT: Multiwalled carbon nanotubes (MWCNTs) functionalized with lysine via 1,3-dipolar cycloaddition and conjugated to galactose or mannose are potential nanocarriers that can effectively bind to the lectin receptor in MDA-MB-231 or MCF-7 breast cancer cells. In this work, a method based on molecular dynamics (MD) simulation was used to predict the interaction of these functionalized MWCNTs with doxorubicin and obtain structural evidence that allows a better understanding of the drug loading and release process. The MD simulations showed that while doxorubicin only interacted with pristine MWCNTs through π-π stacking interactions, functionalized MWCNTs were also able to establish hydrogen bonds, suggesting that the functionalized groups improve doxorubicin loading. Moreover, the elevated adsorption levels observed for functionalized nanotubes further support this enhancement in loading efficiency. MD simulations also shed light on the intratumoral pH-specific release of doxorubicin from functionalized MWCNTs, which is induced by protonation of the daunosamine moiety. The simulations show that this change in protonation leads to a lower absorption of doxorubicin to the MWCNTs. The MD studies were then experimentally validated, where functionalized MWCNTs showed improved dispersion in aqueous medium compared to pristine MWCNTs and, in agreement with the computational predictions, increased drug loading capacity. Doxorubicin-loaded functionalized MWCNTs demonstrated specific release of doxorubicin in tumor microenvironment (pH = 5.0) with negligible release in the physiological pH (pH = 7.4). Furthermore, doxorubicin-free MWNCT nanoformulations exhibited insignificant cytotoxicity. The experimental studies yielded nearly identical results to the MD studies, underlining the usefulness of the method. Our functionalized MWCNTs represent promising non-toxic nanoplatforms with enhanced aqueous dispersibility and the potential for conjugation with ligands for targeted delivery of anti-cancer drugs to breast cancer cells. METHODS: The computational model of a pristine carbon nanotube was created with the buildCstruct 1.2 Python script. The lysinated functionalized groups were added with PyMOL and VMD. The carbon nanotubes and doxorubicin molecules were parameterized using the general AMBER force field, and RESP charges were determined using Gaussian 09. Molecular dynamics simulations were carried out with the AMBER 20 software package. Adsorption levels were calculated using the water-shell function of cpptraj. Cytotoxicity was evaluated via a MTT assay using MDA-MB-231 and MCF-7 breast cancer cells. Drug uptake of doxorubicin and doxorubicin-loaded MWCNTs was measured by fluorescence microscopy.

Curcumin coating: a novel solution to mitigate inherent carbon nanotube toxicity.

Multi-walled Carbon Nanotubes (MWCNTs) are inert structures with high aspect ratios that are widely used as vehicles for targeted drug delivery in cancer and many other diseases. They are largely non-toxic in nature however, when cells are exposed to these nanotubes for prolonged durations or at high concentrations, they show certain adverse effects. These include cytotoxicity, inflammation, generation of oxidative stress, and genotoxicity among others. To combat such adverse effects, various moieties can be attached to the surface of these nanotubes. Curcumin is a known anti-inflammatory, antioxidant and cytoprotective compound derived from a medicinal plant called Curcuma longa. In this study, we have synthesized and characterized Curcumin coated-lysine functionalized MWCNTs and further evaluated the cytoprotective, anti-inflammatory, antioxidant and antiapoptotic effect of Curcumin coating on the surface of MWCNTs. The results show a significant decrease in the level of inflammatory molecules like IL-6, IL-8, IL-1ß, TNFα and NFκB in cells exposed to Curcumin-coated MWCNTs as compared to the uncoated ones at both transcript and protein levels. Further, compared to the uncoated samples, there is a reduction in ROS production and upregulation of antioxidant enzyme-Catalase in the cells treated with Curcumin-coated MWCNTs. Curcumin coating also helped in recovery of mitochondrial membrane potential in the cells exposed to MWCNTs. Lastly, cells exposed to Curcumin-coated MWCNTs showed reduced cell death as compared to the ones exposed to uncoated MWCNTs. Our findings suggest that coating of Curcumin on the surface of MWCNTs reduces its ability to cause inflammation, oxidative stress, and cell death.

Design, synthesis, and anticancer activity of some novel 1H-benzo[d]imidazole-5-carboxamide derivatives as fatty acid synthase inhibitors.

Multiple malignancies exhibit aberrant FASN expression, associated with enhanced de novo lipogenesis to meet the metabolic demands of rapidly proliferating tumour cells. Furthermore, elevated FASN expression has been linked to tumour aggressiveness and poor prognosis in a variety of malignant tumours, making FASN is an attractive target for anticancer drug discovery. Herein, we report the de novo design and synthesis of (2-(2-hydroxyphenyl)-1H-benzo[d]imidazol-5-yl)(piperazin-1-yl)methanone derivatives as novel FASN inhibitors with potential therapeutic applications in breast and colorectal cancers. Twelve (2-(2-hydroxyphenyl)-1H-benzo[d]imidazol-5-yl)(piperazin-1-yl)methanone derivatives (CTL) were synthesized and evaluated for FASN inhibition and cytotoxicity against colon cancer (HCT-116, Caco-2 cell lines), breast cancer (MCF-7 cell line) and normal cell line (HEK-293). Compounds CTL-06 and CTL-12 were chosen as the most promising lead molecules based on FASN inhibition and selective cytotoxicity profiles against colon and breast cancer cell lines. Compounds CTL-06 and CTL-12 demonstrate promising FASN inhibitory activity at IC50 of 3 ± 0.25 µM and 2.5 ± 0.25 µM when compared to the FASN inhibitor orlistat, which has an IC50 of 13.5 ± 1.0 µM. Mechanistic investigations on HCT-116 revealed that CTL-06 and CTL-12 treatment led to cell cycle arrest in Sub-G1/S phase along with apoptosis induction. Western blot studies indicated that CTL-06 and CTL-12 inhibited FASN expression in a dose-dependent manner. CTL-06 and CTL-12 treatment of HCT-116 cells enhanced caspase-9 expression in a dose-dependent manner, while upregulating proapoptotic marker Bax and downregulating antiapoptotic Bcl-xL. Molecular docking experiments of CTL-06 and CTL-12 with FASN enzyme revealed the mode of binding of these analogues in the KR domain of the enzyme.

Fatty Acid Synthase (FASN): A Patent Review Since 2016-Present.

INTRODUCTION: Fatty acid synthase (FASN), is a key metabolic enzyme involved in fatty acid biosynthesis and is an essential target for multiple disease progressions like cancer, obesity, NAFLD, etc. Aberrant expression of FASN is associated with deregulated energy metabolism of cells in these diseases. AREA COVERED: This article provides a summary of the most recent developments in the discovery of novel FASN inhibitors with potential therapeutic uses in cancer, obesity, and other metabolic disorders such as nonalcoholic fatty liver disease from 2016 to the present. The recently published patent applications and forthcoming clinical data of FASN inhibitors from both academia and the pharma industries are also highlighted in this study. EXPERT OPINION: The implication of FASN in multiple diseases has provided an impetus for developing novel inhibitors by both pharma companies and academia. Critical analysis of the patent literature reveals the exploration of diverse molecular scaffolds to identify potential FASN inhibitors that target the different catalytic domains of the enzyme. In spite of these multifaceted efforts, only one molecule, TVB-2640, has reached phase II trials for nonalcoholic steatohepatitis (NASH) and many malignancies. However, thecombined efforts of pharma companies to produce several FASN inhibitors might facilitate the clinical translation of this unique class of inhibitors. Nevertheless, concerted efforts towards developing multiple FASN inhibitors by pharma companies might facilitate the clinical translation of this novel class of inhibitors.

Repaglinide-laden hydrogel particles of xanthan gum derivatives for the management of diabetes.

Herein, the repaglinide-loaded hydrogel particles of carboxyethyl xanthan gum (CEXG) and carboxymethyl xanthan gum (CMXG) were fabricated, and controlled drug delivery performance was assessed. The XG derivatives were characterized by FTIR analyses, degree of substitution, and cytotoxicity assay. CEXG: CMXG (1:2) hydrogel particles had maximum drug entrapment efficiency of 92%. The hydrogel particles swelled a maximum of about 2.25 times in phosphate buffer (pH 6.8) than that in acidic medium (pH 1.2) in 2 h. The particles discharged 97% drug in simulated gastrointestinal pH in 4 h. The acetylation of hydrogel particles reduced the drug entrapment efficiency to 78%; however, it extended drug release up to 8 h, obeying anomalous diffusion. DSC and X-ray diffraction analyses suggested amorphous dispersion of repaglinide after entrapment. Preclinically, the acetylated hydrogels caused a maximum 52.8% reduction in blood glucose level and effectively lowered blood glucose up to 8 h. Hence, the acetylated CEXG: CMXG hydrogel particles could help control diabetes.

Plant derived active compounds as potential anti SARS-CoV-2 agents: an in-silico study.

Plants are a valued potential source of drugs for a variety of diseases and are often considered less toxic to humans. We investigated antiviral compounds that may potentially target SARS-CoV-2 antigenic spike (S) and host proteins; angiotensin-converting enzyme2 (ACE2), and transmembrane serine protease2 (TMPRSS2). We scrutinized 36 phytochemicals from 15 Indian medicinal plants known to be effective against RNA viruses via molecular docking. Besides, the TMPRSS2 structure was modeled and validated using the SWISS-MODEL. Docking was performed using Autodock Vina and 4.2 followed by visualization of the docking poses on Pymol version 2.4.0 and Discovery Studio Visualizer. Molecular docking showed that 12 out of 36 active compounds interacted efficiently with S, ACE2, and TMPRSS2 proteins. The ADMET profile generated using the swissADME and pkCSM server revealed that these compounds were possessed druggable properties. The Amber 12 simulation package was used to carry out energy minimizations and molecular dynamics (MD) simulations. The total simulation time for both S protein: WFA and S protein: WND complexes was 300 ns (100 ns per replica). A total of 120 structures were extracted from the last 60 ns of each MD simulation for further analysis. MM-PBSA and MM-GBSA were employed to assess the binding energy of each ligand and the receptor-binding domain of the viral S-protein. The methods suggested that WND and WFA showed thermodynamically favorable binding energies, and the S protein had a higher affinity with WND. Interestingly, Leu455 hotspot residue in the S protein, also predicted to participate in binding with ACE2, was engaged by WND and WFA. HighlightsPlants' natural active compounds may aid in the development of COVID-19 therapeutics.MD simulation study revealed stable binding of withanolide D and withaferin A with spike proteinWithanolide D and withaferin A could be effective against SARS-CoV-2 spike protein.Discovery of druggable agents that have less or lack of binding affinity with ACE2 to avoid the organs associated with comorbidities.According to ADMET selected phytochemicals may be used as druggable compounds.Communicated by Ramaswamy H. Sarma.

Structure based virtual screening of natural product molecules as glycosidase inhibitors.

Objective of the present investigation comprised of the application of in silico methods to discover novel natural product (NP) based potential inhibitors for carbohydrate mediated diseases. Structure based drug design studies (molecular docking and structure based pharmacophore analysis)  were carried out on a series of natural product compounds to identify significant bioactive molecules to inhibit α-mannosidase (I and II) and ß-galactosidase enzymes. Furthermore, protein ligand interaction fingerprint analysis, molecular dynamics simulations and molecular access system (MACCS) fingerprint analysis were performed to understand the binding behaviors of the studied molecules. The results derived from these analyses showed that the identified compounds exhibit significant binding interactions with the active site residues. The compounds, NP-51, NP-81 and NP-165 have shown significant docking score against the studied enzymes (α-mannosidases-I, α-mannosidases-II and ß-galactosidases). The fingerprint studies showed that the presence of rings (aromatic or aliphatic) with sulfur atoms, nitrogen atoms, methyl groups, etc. have favorable effects on the α-mannosidase II inhibitory activity. However, the presence of halogen atoms substituted in the molecules have reduced inhibitory ability against α-mannosidase II. The compound, NP-165 has significant activity against both enzymes (α-mannosidases and ß-galactosidases). These studies accomplished that the compounds identified through in silico methodologies can be used to develop semisynthetic derivatives of the glycosidase inhibitors and can be screened for the treatment of different carbohydrate mediated diseases. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40203-021-00115-9.

Antiproliferative Efficacy of N-(3-chloro-4-fluorophenyl)-6,7-dimethoxyquinazolin-4-amine, DW-8, in Colon Cancer Cells Is Mediated by Intrinsic Apoptosis.

A novel series of 4-anilinoquinazoline analogues, DW (1-10), were evaluated for anticancer efficacy in human breast cancer (BT-20) and human colorectal cancer (CRC) cell lines (HCT116, HT29, and SW620). The compound, DW-8, had the highest anticancer efficacy and selectivity in the colorectal cancer cell lines, HCT116, HT29, and SW620, with IC50 values of 8.50 ± 2.53 µM, 5.80 ± 0.92 µM, and 6.15 ± 0.37 µM, respectively, compared to the non-cancerous colon cell line, CRL1459, with an IC50 of 14.05 ± 0.37 µM. The selectivity index of DW-8 was >2-fold in colon cancer cells incubated with vehicle. We further determined the mechanisms of cell death induced by DW-8 in SW620 CRC cancer cells. DW-8 (10 and 30 µM) induced apoptosis by (1) producing cell cycle arrest at the G2 phase; (2) activating the intrinsic apoptotic pathway, as indicated by the activation of caspase-9 and the executioner caspases-3 and 7; (3) nuclear fragmentation and (4) increasing the levels of reactive oxygen species (ROS). Overall, our results suggest that DW-8 may represent a suitable lead for developing novel compounds to treat CRC.

A Novel Dialkylamino-Functionalized Chalcone, DML6, Inhibits Cervical Cancer Cell Proliferation, In Vitro, via Induction of Oxidative Stress, Intrinsic Apoptosis and Mitotic Catastrophe.

In this study, we designed, synthesized and evaluated, in vitro, novel chalcone analogs containing dialkylamino pharmacophores in the cervical cancer cell line, OV2008. The compound, DML6 was selective and significantly decreased the proliferation of OV2008 and HeLa cells in sub-micromolar concentrations, compared to prostate, lung, colon, breast or human embryonic kidney cell line (HEK293). DML6, at 5 µM, arrested the OV2008 cells in the G2 phase. Furthermore, DML6, at 5 µM, increased the levels of reactive oxygen species and induced a collapse in the mitochondrial membrane potential, compared to OV2008 cells incubated with a vehicle. DML6, at 5 µM, induced intrinsic apoptosis by significantly (1) increasing the levels of the pro-apoptotic proteins, Bak and Bax, and (2) decreasing the levels of l the anti-apoptotic protein, Bcl-2, compared to cell incubated with a vehicle. Furthermore, DML6, at 5 and 20 µM, induced the cleavage of caspase-9, followed by subsequent cleavage of the executioner caspases, caspase-3 and caspase-7, which produced OV2008 cell death. Overall, our data suggest that DML6 is an apoptosis-inducing compound that should undergo further evaluation as a potential treatment for cervical cancer.

The Rise and Fall of Chloroquine/Hydroxychloroquine as Compassionate Therapy of COVID-19.

The emergence and rapid spread of novel coronavirus disease (COVID-19) has posed a serious challenge to global public health in 2020. The speed of this viral spread together with the high mortality rate has caused an unprecedented public health crisis. With no antivirals or vaccines available for the treatment of COVID-19, the medical community is presently exploring repositioning of clinically approved drugs for COVID-19. Chloroquine (CQ) and hydroxychloroquine (HCQ) have emerged as potential candidates for repositioning as anti-COVID-19 therapeutics and have received FDA authorization for compassionate use in COVID-19 patients. On March 28, 2020, the U.S. Food and Drug Administration (FDA) issued an Emergency Use Authorization (EUA) for HCQ in the treatment of COVID-19. However, it was later revoked by the FDA on June 15, 2020, after analyzing the emerging scientific data from ongoing clinical trials. Similarly, the World Health Organization (WHO) also conducted a Solidarity trial of chloroquine, hydroxychloroquine, remdesivir, lopinavir, and ritonavir. However, on May 23, 2020, the executive body of the "Solidarity trial" decided to put a temporary hold on the HCQ trial. On June 17, 2020, the WHO abruptly stopped the Solidarity trial of HCQ. The current review strives to examine the basis of compassionate use of CQ and HCQ for the treatment of COVID-19 in terms of literature evidence, establishing the antiviral efficacy of these drugs against corona and related viruses. Furthermore, the review presents a critical analysis of the clinical trial findings and also provides an insight into the dynamically changing decision on the authorization and withdrawal of HCQ as anti-COVID-19 therapy by the U.S. FDA and the WHO. Ultimately, our study necessitates an evidenced-based treatment protocol to confront the ongoing COVID-19 pandemic and not the mere observational study that mislead the public healthcare system, which paralyzes the entire world.

Recent Advances in the Development of Fatty Acid Synthase Inhibitors as Anticancer Agents.

Fatty acid synthase (FASN) is a multifunctional enzyme involved in the production of fatty acids for lipid biosynthesis. FASN is overexpressed in multiple diseases like cancer, viral, nonalcoholic fatty liver disease, and metabolic disorders, making it an attractive target for new drug discovery for these diseases. In cancer, FASN affects the structure and function of the cellular membrane by channelizing with signaling pathways along with the post-translational palmitoylation of proteins. There are several natural and synthetic FASN inhibitors reported in the literature, a few examples are GSK 2194069 (7.7 nM), imidazopyridine (16 nM), epigallocatechin-3-gallate (42.0 µg/ml) and platensimycin (300 nM) but except for TVB-2640, none of the aforementioned inhibitors have made into clinical trials. The present review summarizes the recent advancements made in anticancer drug discovery targeting FASN. Furthermore, the review also provides insights into the medicinal chemistry of small molecule inhibitors targeting different FASN enzyme domains, and also critically analyzes the structural requirements for FASN inhibition with an objective to support rational design and development of new generation FASN inhibitors with clinical potential in diseases like cancer.

Xanthan gum derivatives: review of synthesis, properties and diverse applications.

Natural polysaccharides are well known for their biocompatibility, non-toxicity and biodegradability. These properties are also inherent to xanthan gum (XG), a microbial polysaccharide. This biomaterial has been extensively investigated as matrices for tablets, nanoparticles, microparticles, hydrogels, buccal/transdermal patches, tissue engineering scaffolds with different degrees of success. However, the native XG has its own limitations with regards to its susceptibility to microbial contamination, unusable viscosity, poor thermal and mechanical stability, and inadequate water solubility. Chemical modification can circumvent these limitations and tailor the properties of virgin XG to fulfill the unmet needs of drug delivery, tissue engineering, oil drilling and other applications. This review illustrates the process of chemical modification and/crosslinking of XG via etherification, esterification, acetalation, amidation, and oxidation. This review further describes the tailor-made properties of novel XG derivatives and their potential application in diverse fields. The physicomechanical modification and its impact on the properties of XG are also discussed. Overall, the recent developments on XG derivatives are very promising to progress further with polysaccharide research.

Design, synthesis and biological evaluation of some tetrazole acetamide derivatives as novel non-carboxylic PTP1B inhibitors.

A series of ten N-(3-(1H-tetrazole-5-yl)phenyl)acetamide derivatives (NM-07 to NM-16) designed from a lead molecule identified previously in our laboratory were synthesized and evaluated for protein tyrosine phosphatase 1B (PTP1B) inhibitory activity. Among the synthesized molecules, NM-14, a 5-Cl substituted benzothiazole analogue elicited significant PTP1B inhibition with an IC50 of 1.88 µM against reference standard suramin (IC50 ≥ 10 µM). Furthermore, this molecule also showed good in vivo antidiabetic activity which was comparable to that of standard antidiabetic drugs metformin and glimepiride. Overall, the results of the study clearly reveal that the reported tetrazole derivatives especially NM-14 are valuable prototypes for the development of novel non-carboxylic inhibitors of PTP1B with antidiabetic potential.

lH-Pyrazolo[3,4-b]quinolin-3-amine derivatives inhibit growth of colon cancer cells via apoptosis and sub G1 cell cycle arrest.

A series of lH-pyrazolo[3,4-b]quinolin-3-amine derivatives were synthesized and evaluated for anticancer efficacy in a panel of ten cancer cell lines, including breast (MDAMB-231 and MCF-7), colon (HCT-116, HCT-15, HT-29 and LOVO), prostate (DU-145 and PC3), brain (LN-229), ovarian (A2780), and human embryonic kidney (HEK293) cells, a non-cancerous cell line. Among the eight derivatives screened, compound QTZ05 had the most potent and selective antitumor efficacy in the four colon cancer cell lines, with IC50 values ranging from 2.3 to 10.2 µM. Furthermore, QTZ05 inhibited colony formation in HCT-116 cells in a concentration-dependent manner. Cell cycle analysis data indicated that QTZ05 caused an arrest in the sub G1 cell cycle in HCT-116 cells. QTZ05 induced apoptosis in HCT-116 cells in a concentration-dependent manner that was characterized by chromatin condensation and increase in the fluorescence of fluorochrome-conjugated Annexin V. The findings from our study suggest that QTZ05 may be a valuable prototype for the development of chemotherapeutics targeting apoptotic pathways in colorectal cancer cells.

Recent Advances in Protein Tyrosine Phosphatase 1B Targeted Drug Discovery for Type II Diabetes and Obesity.

BACKGROUND: Protein tyrosine phosphatase 1B (PTP1B) is an important therapeutic target for type II diabetes and obesity because of its pivotal role as a negative modulator in both insulin and leptin signalling pathways. OBJECTIVE: The discovery of PTP1B inhibitors has been the focus of researchers in both academia and pharmaceutical industry over the last two decades. RESULTS AND CONCLUSION: Though, intense pharmaceutical research in this area has resulted in many potent PTP1B inhibitors, a vast majority of them possessed pTyr mimetic group such as phosphonates, carboxylic acids and sulphamic acids, which led to poor PTP1B selectivity and insufficient in vivo efficacy due to low cell permeability and bioavailability. The availability of X-ray crystallographic structures of PTP1B together with the application of molecular modelling and other innovative strategies led to the development of many potent and selective PTP1B inhibitors with desirable physicochemical properties. This review traces the development of PTP1B inhibitors over the last decade and also records novel PTP1B inhibitors developed recently with greater emphasis on their selectivity and cell permeability.

Molecular dynamic simulations and structure-based pharmacophore development for farnesyltransferase inhibitors discovery.

Farnesyltransferase is one of the enzyme targets for the development of drugs for diseases, including cancer, malaria, progeria, etc. In the present study, the structure-based pharmacophore models have been developed from five complex structures (1LD7, 1NI1, 2IEJ, 2ZIR and 2ZIS) obtained from the protein data bank. Initially, molecular dynamic (MD) simulations were performed for the complexes for 10 ns using AMBER 12 software. The conformers of the complexes (75) generated from the equilibrated protein were undergone protein-ligand interaction fingerprint (PLIF) analysis. The results showed that some important residues, such as LeuB96, TrpB102, TrpB106, ArgB202, TyrB300, AspB359 and TyrB361, are predominantly present in most of the complexes for interactions. These residues form side chain acceptor and surface (hydrophobic or π-π) kind of interactions with the ligands present in the complexes. The structure-based pharmacophore models were generated from the fingerprint bits obtained from PLIF analysis. The pharmacophore models have 3-4 pharmacophore contours consist of acceptor and metal ligation (Acc & ML), hydrophobic (HydA) and extended acceptor (Acc2) features with the radius ranging between 1-3 Å for Acc & ML and 1-2 Å for HydA. The excluded volumes of the pharmacophore contours radius are between 1-2 Å. Further, the distance between the interacting groups, root mean square deviation (RMSD), root mean square fluctuation (RMSF) and radial distribution function (RDF) analysis were performed for the MD-simulated proteins using PTRAJ module. The generated pharmacophore models were used to screen a set of natural compounds and database compounds to select significant HITs. We conclude that the developed pharmacophore model can be a significant model for the identification of HITs as FTase inhibitors.

Viral M2 ion channel protein: a promising target for anti-influenza drug discovery.

Influenza virus is an important RNA virus causing pandemics (Spanish Flu (1918), Asian Flu (1957), Hong Kong Flu (1968) and Swine Flu (2009)) over the last decades. Due to the spontaneous mutations of these viral proteins, currently available antiviral and anti-influenza drugs quickly develop resistance. To account this, only limited antiinfluenza drugs have been approved for the therapeutic use. These include amantadine and rimantadine (M2 proton channel blockers), zanamivir, oseltamivir and peramivir (neuraminidase inhibitors), favipravir (polymerase inhibitor) and laninamivir. This review provides an outline on the strategies to develop novel, potent chemotherapeutic agents against M2 proton channel. Primarily, the M2 proton channel blockers elicit pharmacological activity through destabilizing the helices by blocking the proton transport across the transmembrane. The biologically important compounds discovered using the scaffolds such as bisnoradmantane, noradamantane, triazine, spiroadamantane, isoxazole, amino alcohol, azaspiro, spirene, pinanamine, etc are reported to exhibit anti-influenza activity against wild or mutant type (S31N and V27A) of M2 proton channel protein. The reported studies explained that the adamantane based compounds (amantadine and rimantadine) strongly interact with His37 (through hydrogen bonding) and Ala30, Ile33 and Gly34 residues (hydrophobic interactions). The adamantane and the non-adamantane scaffolds fit perfectly in the active site pocket present in the wild type and the charged amino groups (ammonium) create positive electrostatic potential, which blocks the transport of protons across the pore. In the mutated proteins, larger or smaller binding pocket are created by small or large mutant residues, which do not allow the molecules fit in the active site. This causes the channel to be unblocked and the protons are allowed to transfer inside the pore. The structural analysis of the M2 proton channel blockers illustrated that the adamantane derivatives have action against both influenza A and B, but have no effect on the mutants.

Human CDC2-like kinase 1 (CLK1): a novel target for Alzheimer's disease.

The cdc2-like kinases (CLKs) are an evolutionarily conserved group of dual specificity kinases belonging to the CMGC (cyclin-dependent kinases (CDKs), mitogen-activated protein kinases (MAP kinases), glycogen synthase kinases (GSK) and CDK-like kinases). The CLK family consists of four isoforms namely CLK1, CLK2, CLK3 and CLK4. The human CLK1 encoded protein comprises 454 amino acids and the catalytic domain of CLK1 exhibits the typical protein kinase fold. CLK1 has been shown to autophosphorylate on serine, threonine and tyrosine residues and phosphorylate exogenous substrates on serine and threonine residues. CLK1 plays an important role in the regulation of RNA splicing through phosphorylation of members of the serine and arginine-rich (SR) family of splicing factors. CLK1 is involved in the pathophysiology of Alzheimer's disease by phosphorylating the serine residue in SR proteins. Nuclear speckles of the nucleoplasm contain the stored form of SR proteins and are moderately responsible for the choice of splicing sites during pre-mRNA splicing. Hence, the inhibition of CLK1 can be used as a therapeutic strategy for Alzheimer's disease. Many natural and synthetic molecules are reported to possess CLK1 inhibitory activity. Some specific examples are Marine alkaloid Leucettamine B and KH-CB19. Leucettamine B is a potent inhibitor of CLK1 (15 nM), Dyrk1A (40 nM), and Dyrk2 (35 nM) and a moderate inhibitor of CLK3 (4.5 µM) whereas KH-CB19 is a highly specific and potent inhibitor of the CLK1/CLK4. X-ray crystallographic studies have revealed the binding mode of marine sponge metabolite hymenialdisine and a dichloroindolyl enamino nitrile (KH-CB19) to CLK1. This review focuses on the role of CLKs in the pathophysiology of Alzheimer's disease and therapeutic potential of targeting CLK1 in Alzheimer's disease drug discovery and development. In addition, the recent developments in drug discovery efforts targeting human CLK1 are also highlighted.

Fused aryl-phenazines: scaffold for the development of bioactive molecules.

Fused aryl phenazine derivatives (benzo[a]phenazine, pyrido[a]phenazine, benzo[a]phenazine diones, tetrahydropyrido[a]phenazine (dermacozines), etc) are important heterocyclic compounds, which exhibit various pharmacological activities, prominently in cancer cell lines. These compounds significantly intercalate between DNA base pairs and inhibit the activities of topoisomerase I and II enzymes (Topo I and II). XR11576, XR5944, NC-190 and NC-182 belong to phenazine/fused aryl phenazine category and are under clinical studies. Several fused aryl phenazine dione compounds such as pyridazino[4,5-b]phenazine-5,12-diones, 6,11-dihydro-pyrido[2,3-b]phenazine-6,11-diones, 6,11-dihydrobenzo[2,3-b]phenazine-6,11-diones, tetrahydropyrido[a]phenazine, etc possessed anticancer activities on various cancer cell lines. Benzo[a]phenazine diimine and various other fused aryl phenazine compounds form coordination complex with the metal ions (Ru, Rh, Zn and Pt) that intercalate with the DNA and are used for the treatment of cancer. These molecules have influence on MDR cancer cells and serve as anticancer agents in MDR cancer cells. The structure activity relationship of the fused aryl phenazine derivatives revealed that the occurrence of four or more nitrogen atoms in the compounds has better anticancer activity than those molecules with less number of nitrogen atoms. Phenazine antibiotics derived from marine microbes are used for the treatment of microbial and worm diseases. Recent patents on these scaffolds showed that the benzo[a]phenazine derivatives have inhibitory activity on topoisomerase enzymes (Topo I and II) and that act as anticancer agents.

Predictive QSAR models development and validation for human ether-a-go-go related gene (hERG) blockers using newer tools.

In the present computational analysis, pharmacophore-based active conformer selection method was used to derive active conformers for the physicochemical descriptors calculation. The significant regression models were validated using different validation methods, which provided significant Q(2) values. The distance-based approaches were also used to analyze the discriminant property of the molecules contributed in the models. The Mahalanobis distance (MD) values obtained from these studies revealed that the compounds with very high and very low acting human ether-a-go-go-related gene blockers possessed high MD values, while the predicted activity of those compounds exhibited less residual errors. The results obtained in the studies suggest that the distance-based approaches can be used to validate the quantitative structure-activity relationship models significantly. The descriptors contributed in the models explain that the flexibility of the bonds connected to the aromatic rings or non-polar region of the molecules make π-π interaction with the aromatic residues of the protein.