Covalent inhibitors: An ambitious approach for the discovery of newer oncotherapeutics.

Covalent inhibitors have been used to treat several diseases for over a century. However, strategic approaches for the rational design of covalent drugs have taken a definitive shape in recent times. Since the first appearance of covalent inhibitors in the late 18th century, the field has grown tremendously and around 30% of marketed drugs are covalent inhibitors especially, for oncology indications. However, the off-target toxicity and safety concerns can be significant issues related to the covalent drugs. Covalent kinase inhibitor (CKI) targeted oncotherapeutics has advanced dramatically over the last two decades since the discovery of afatinib (Gilotrif®), an EGFR inhibitor. Since then, US FDA has approved 10 CKIs for diverse cancer targets. The present review broadly summarizes the ongoing development in the discovery of newer CKIs from 2016 till the end of 2022. We believe that these efforts will assist the modern medicinal chemist actively working in the field of CKI discovery for varied indications.

Hit discovery of novel 2-phenyl-substituted 4-amino-6,7-dihydro-5H-cyclopenta[d]pyrimidines as potential anti-glioblastoma therapeutics: Design, synthesis, biological evaluation, and computational screening.

Glioblastoma multiforme (GBM) is a highly-aggressive, dreadful disease with poor prognosis and disappointing clinical success. There is an unmet medical need of molecularly-targeted therapeutics for GBM treatment. In the present work, a series of novel 2-phenyl-substituted 4-amino-6,7-dihydro-5H-cyclopenta[d]pyrimidines was designed, synthesized, purified, characterized, and evaluated for cytotoxicity against glioblastoma cell line U87-MG. The design process (virtual library enumeration around the core, physicochemical and molecular property prediction/calculation of the designs, filtering the undesirable ones, and the diversity analyses of the lead-like designs), was carefully curated so as to obtain a set of structurally-diverse, novel molecules (total 20), with a particular focus on the relatively unexplored core structure, 6,7-dihydro-5H-cyclopenta[d]pyrimidine. The preliminary screening was done using MTT assay at 10 and 100 µM concentrations of the title compounds F1 -F20 and positive control cisplatin, which yielded six hits (% inhibition at 10 µM: ~50%)-F2 , F3 , F5 , F7 , F15 , and F20 , which were taken up for IC50 determination. The top hits F2 and F7 (IC50 < 10 µM) were further used for computational studies such as target prediction, followed by their molecular docking in the binding sites of the top-3 predicted targets (epidermal growth factor receptor kinase domain, cyclin-dependent kinase 2 [CDK2]) /cyclin E, and anaplastic lymphoma kinase [ALK]). The docking pose analyses revealed interesting trends. The relatively planar core structure, presence of favorable hinge-binding substructures, basic groups, all added up, and culminated in appreciable cytotoxicity against GBM cell line.

Exploration of the inhibitory effect of Cassia fistula on quorum sensing mediated virulence factor production and biofilm activity in Pseudomonas aeruginosa: an in vivo study in model organism Caenorhabditis elegans.

Introduction. Resistance to antibiotics is leading to challenges in the treatment of microbial diseases. One amongst the various approaches to control these pathogens is quorum sensing (QS), which is used to rectify resistance issues. Blocking the bacterial QS circuit is the most reliable anti-virulence therapy to control pathogenicity-associated genes. Pseudomonas aeruginosa is a contagious bacterium that proliferates in the host by using signalling molecules like acyl-homoserine lactones; these molecules generate and disseminate toxins and virulence factors for increasing host infection.Hypothesis. The herb Cassia fistula is known to have antimicrobial, antidiabetic, anti-inflammatory, antitumor medicinal properties amongst others. We hypothesize that its crude extracts will inhibit the QS circuit of Pseudomonas aeruginosa (P. aeruginosa).Aim. The research work was aimed at evaluating anti-quorum sensing and anti-biofilm activity of various crude extracts from Cassia fistula against P. aeruginosa.Methodology. Various extraction methods and solvents were availed for maximum separation, and the extracts were screened for anti-quorum sensing activity. The most potent Fruit Ethyl acetate (FEE) extract at non-inhibitory concentrations was found to interrupt both short-chain (RhlI/R) and long-chain (LasI/R) QS circuits and other virulence factors (P<0.05) such as elastase, protease, rhamnolipids and pyocyanin levels in P. aeruginosa. Biofilm inhibitory properties of FEE were demonstrated using atomic force microscopy, scanning electron microscope and confocal laser microscope. Caenorhabditis elegans infection model (Paralytic assay) was developed to determine the protective role of FEE by reducing the pathogenicity of P. aeruginosa.Results. The study results suggest that hot crude FEE extract interfered in the QS circuit, leading to comprehensive debilitation of QS-controlled virulence factors. The extract reduced virulence factor production in P. aeruginosa at 4 mg ml-1 concentration whilst paradoxically promoting biofilm formation. Possibly, higher sugar content in the extract promoted clump formation of biofilm architecture by increasing exopolysaccharide production. Moreover, in vivo analysis of bacterial pathogenesis on Caenorhabditis elegans reveals a drastic increase in survival rates in FEE treated worms compared to untreated control.Conclusions. FEE showed promising QS inhibitory activity against P. aeruginosa. In the future, additional purification of crude FEE is required to remove carbohydrates, and pure isolated phytochemicals from FEE could be used as therapeutic agents to control QS-mediated infections in P. aeruginosa.

Molecular Insights into Coumarin Analogues as Antimicrobial Agents: Recent Developments in Drug Discovery.

A major global health risk has been witnessed with the development of drug-resistant bacteria and multidrug-resistant pathogens linked to significant mortality. Coumarins are heterocyclic compounds belonging to the benzophenone class enriched in different plants. Coumarins and their derivatives have a wide range of biological activity, including antibacterial, anticoagulant, antioxidant, anti-inflammatory, antiviral, antitumour, and enzyme inhibitory effects. In the past few years, attempts have been reported towards the optimization, synthesis, and evaluation of novel coumarin analogues as antimicrobial agents. Several coumarin-based antibiotic hybrids have been developed, and the majority of them were reported to exhibit potential antibacterial effects. In the present work, studies reported from 2016 to 2020 about antimicrobial coumarin analogues are the focus. The diverse biological spectrum of coumarins can be attributed to their free radical scavenging abilities. In addition to various synthetic strategies developed, some of the structural features include a heterocyclic ring with electron-withdrawing/donating groups conjugated with the coumarin nucleus. The suggested structure-activity relationship (SAR) can provide insight into how coumarin hybrids can be rationally improved against multidrug-resistant bacteria. The present work demonstrates molecular insights for coumarin derivatives having antimicrobial properties from the recent past. The detailed SAR outcomes will benefit towards leading optimization during the discovery and development of novel antimicrobial therapeutics.

Crocetin and related oxygen diffusion-enhancing compounds: Review of chemical synthesis, pharmacology, clinical development, and novel therapeutic applications.

The current pandemic forced us to introspect and revisit our armamentarium of medicinal agents which could be life-saving in emergency situations. Oxygen diffusion-enhancing compounds represent one such class of potential therapeutic agents, particularly in ischemic conditions. As rewarding as the name suggests, these agents, represented by the most advanced and first-in-class molecule, trans-sodium crocetinate (TSC), are the subject of intense clinical investigation, including Phase 1b/2b clinical trials for COVID-19. Being a successor of a natural product, crocetin, TSC is being investigated for various cancers as a radiosensitizer owing to its oxygen diffusion enhancement capability. The unique properties of TSC make it a promising therapeutic agent for various ailments such as hemorrhagic shock, stroke, heart attack, among others. The present review outlines various (bio)synthetic strategies, pharmacological aspects, clinical overview and potential therapeutic benefits of crocetin and related compounds including TSC. The recent literature focusing on the delivery aspects of these compounds is covered as well to paint the complete picture to the curious reader. Given the potential TSC holds as a first-in-class agent, small- and/or macromolecular therapeutics based on the core concept of improved oxygen diffusion from blood to the surrounding tissues where it is needed the most, will be developed in future and satisfy the unmet medical need for many diseases and disorders.

A novel series of substituted 1,2,3-triazoles as cancer stem cell inhibitors: Synthesis and biological evaluation.

An alarming increase in global death toll resulting from cancer incidents, particularly due to multidrug resistance and reduced efficacy as a consequence of target mutations, has compelled us to look for novel anticancer agents. Cancer stem cells (CSCs), contributing majorly to the chemoresistance and tumor relapse, seem to the main culprits. In the present investigation, new chemical entities (NCEs) belonging to four novel chemical series (A: 4'-allyl-2'-methoxyphenoxymethyl-1,2,3-triazoles; B: 4'-acetamidophenoxymethyl-1,2,3-triazoles; C: naphthalene-1'-yloxymethyl-1,2,3-triazoles, and D: naphthalene-2'-yloxymethyl-1,2,3-triazoles) were synthesized via Copper (I)-catalyzed alkyne-azide cycloaddition reaction and evaluated for in vitro anticancer activity. A total of 30 NCEs (39-68) were screened at 10 µM concentration in cell viability assay against cancer cell lines such as breast (MDA-MB-231), prostate (PC-3), glioma (U87 MG), along with cervical (SiHa) and lung (A549). The NCEs from Series C (56-60) and D (61-68) were more potent than those in Series A (39-45) and Series B (46-55) at the tested concentration. Furthermore, NCEs with >80% inhibition at 10 µM were evaluated for dose response. A total of five NCEs, 48, 56, 61, 65 and 66, were further assessed in soft-agar assay and found to be relatively potent (IC50 < 10 µM). Finally, the hits were screened in sphere assay to identify potential CSC inhibitors against mammospheres (MDA-MB-231) and prostatospheres (PC-3). More so, the hits were also evaluated to understand in vitro cytotoxicity against normal cells using mouse embryonic fibroblast cell line (NIH/3T3) and human peripheral blood mononuclear cells (hPBMCs). Overall, hits 56 and 61 exhibited potent anticancer as well as CSC inhibitory activities with notably less toxicity toward NIH/3T3 and hPBMCs. On the whole, our arduous study led to the identification of potential hits with anticancer and CSC inhibitory activities, with minimal or no toxicity to normal cells.

Cancer Stem Cell (CSC) Inhibitors in Oncology-A Promise for a Better Therapeutic Outcome: State of the Art and Future Perspectives.

Cancer stem cells (CSCs), a subpopulation of cancer cells endowed with self-renewal, tumorigenicity, pluripotency, chemoresistance, differentiation, invasive ability, and plasticity, reside in specialized tumor niches and are responsible for tumor maintenance, metastasis, therapy resistance, and tumor relapse. The new-age "hierarchical or CSC" model of tumor heterogeneity is based on the concept of eradicating CSCs to prevent tumor relapse and therapy resistance. Small-molecular entities and biologics acting on various stemness signaling pathways, surface markers, efflux transporters, or components of complex tumor microenvironment are under intense investigation as potential anti-CSC agents. In addition, smart nanotherapeutic tools have proved their utility in achieving CSC targeting. Several CSC inhibitors in clinical development have shown promise, either as mono- or combination therapy, in refractory and difficult-to-treat cancers. Clinical investigations with CSC marker follow-up as a measure of clinical efficacy are needed to turn the "hype" into the "hope" these new-age oncology therapeutics have to offer.

An outlook on procedures of conjugating folate to (co)polymers and drugs for effective cancer targeting.

Folate receptors (FRs) are expressed in vast majority of cancers. Selective targeting of the FRs is, therefore, one of the most popular and sought-after strategies for improving the efficacy of cancer therapeutics. Variety of approaches involving folate conjugation to several well-known and novel, nontoxic, biodegradable, and biocompatible (co)polymers have been attempted and successfully applied to a large number of nanoparticulate drug delivery systems (micelles, liposomes, nanoparticles, quantum dots, mesoporous silica-based materials, and others) in the last decade-and-a-half. Standard and novel synthetic approaches were utilized for the conjugation, followed by the formulation of the drug delivery modality. In most of the cases, the targeted system lived up to its reputation, validating its usefulness in targeted cancer therapeutics. The present review summarizes the progress and state-of-the-art synthetic methodologies for folate conjugation to (co)polymers, drugs, and nucleic acids. The limitations of the FR targeting are discussed in brief to give the reader the other side of the story. Finally, the information on marketed folic acid conjugates highlight their industrial applications.

Computational Approaches for the Design of (Mutant-)Selective Tyrosine Kinase Inhibitors: State-of-the-Art and Future Prospects.

Kinases remain one of the major attractive therapeutic targets for a large number of indications such as cancer, rheumatoid arthritis, cardiac failure and many others. Design and development of kinase inhibitors (ATP-competitive, allosteric or covalent) is a clinically validated and successful strategy in the pharmaceutical industry. The perks come with limitations, particularly the development of resistance to highly potent and selective inhibitors. When this happens, the cycle needs to be repeated, i.e., the design and development of kinase inhibitors active against the mutated forms. The complexity of tumor milieu makes it awfully difficult for these molecularly-targeted therapies to work. Every year newer and better versions of these agents are introduced in the clinic. Several computational approaches such as structure-, ligand-based or hybrid ones continue to live up to their potential in discovering novel kinase inhibitors. New schools of thought in this area continue to emerge, e.g., development of dual-target kinase inhibitors. But there are fundamental issues with this approach. It is indeed difficult to selectively optimize binding at two entirely different or related kinases. In addition to the conventional strategies, modern technologies (machine learning, deep learning, artificial intelligence, etc.) started yielding the results and building success stories. Computational tools invariably played a critical role in catalysing the phenomenal progress in kinase drug discovery field. The present review summarized the progress in utilizing computational methods and tools for discovering (mutant-)selective tyrosine kinase inhibitor drugs in the last three years (2017-2019). Representative investigations have been discussed, while others are merely listed. The author believes that the enthusiastic reader will be inspired to dig out the cited literature extensively to appreciate the progress made so far and the future prospects of the field.

Substituted chloroacetamides as potential cancer stem cell inhibitors: Synthesis and biological evaluation.

Cancer kills, irrespective of geographical and cultural origin. Novel modalities for treating cancer are desperately needed. Cancer stem cells (CSCs), main culprits behind chemoresistance and tumor relapse, are one of the few logical choices. Herein, we report the synthesis and biological evaluation of small molecules with chloroacetamide war-head. These molecules were screened for viability against various breast, prostate, and oral cancer cell lines using MTT and soft-agar assays. Further, promising hits were screened in sphere-forming assay with the aim of discovering potential anti-CSC agents. Our optimism yielded four hits inhibiting self-renewal of cancer cells with stem-like characters in vitro. Finally, the hits were evaluated for in vitro toxicity against human peripheral blood mononuclear cells and mouse embryonic fibroblast cell line. Overall, these preliminary investigations yielded three hits exhibiting promising anti-CSC potential with little or no toxicity against normal cells.

Novel analogs of sulfasalazine as system xc- antiporter inhibitors: Insights from the molecular modeling studies.

System xc- (Sxc- ), a cystine-glutamate antiporter, is established as an interesting target for the treatment of several pathologies including epileptic seizures, glioma, neurodegenerative diseases, and multiple sclerosis. Erastin, sorafenib, and sulfasalazine (SSZ) are a few of the established inhibitors of Sxc- . However, its pharmacological inhibition with novel and potent agents is still very much required due to potential issues, for example, potency, bioavailability, and blood-brain barrier (BBB) permeability, with the current lead molecules such as SSZ. Therefore, in this study, we report the synthesis and structure-activity relationships (SAR) of SSZ derivatives along with molecular docking and dynamics simulations using the developed homology model of xCT chain of Sxc- antiporter. The generated homology model attempted to address the limitations of previously reported comparative protein models, thereby increasing the confidence in the computational modeling studies. The main objective of the present study was to derive a suitable lead structure from SSZ eliminating its potential issues for the treatment of glioblastoma multiforme (GBM), a deadly and malignant grade IV astrocytoma. The designed compounds with favorable Sxc- inhibitory activity following in vitro Sxc- inhibition studies, showed moderately potent cytotoxicity in patient-derived human glioblastoma cells, thereby generating potential interest in these compounds. The xCT-ligand model can be further optimized in search of potent lead molecules for novel drug discovery and development studies.

Design, synthesis, and biological evaluation of Helicobacter pylori inosine 5'-monophosphate dehydrogenase (HpIMPDH) inhibitors.

Inosine 5'-monophosphate dehydrogenase (IMPDH) catalyzes a crucial step in the biosynthesis of guanine nucleotides. Being a validated target for immunosuppressive, antiviral, and anticancer drug development, lately it has been exploited as a promising target for antimicrobial therapy. Extending our previous work on Mycobacterium tuberculosis IMPDH, GuaB2, inhibitor development, we screened a set of 23 new chemical entities (NCEs) with substituted flavone (Series 1) and 1,2,3-triazole (Series 2) core structures for their in vitro Helicobacter pylori IMPDH (HpIMPDH) and human IMPDH2 (hIMPDH2) inhibitory activities. All the NCEs possessed acceptable molecular, physicochemical, and toxicity property profiles. The ranges for HpIMPDH and hIMPDH2 inhibition were 9-99.9% and 16-57%, respectively, at 10 µM concentration. The most potent HpIMPDH inhibitor, 25c, exhibited IC50 value of 1.27 µM with no hIMPDH2 inhibitory activity. The moderately potent, structurally novel hit molecule, 25c, may serve as a lead for further design and development of highly potent HpIMPDH inhibitors.

Novel chalcone and flavone derivatives as selective and dual inhibitors of the transport proteins ABCB1 and ABCG2.

During cancer chemotherapy, certain cancers may become cross-resistant to structurally diverse antineoplastic agents. This so-called multidrug resistance (MDR) is highly associated with the overexpression of ATP-binding cassette (ABC) transport proteins. These membrane-bound efflux pumps export a broad range of structurally diverse endo- and xenobiotics, including chemically unrelated anticancer agents. This translocation of drugs from the inside to the outside of cancer cells is mediated at the expense of ATP. In the last 40 years, three ABC transporters - ABCB1 (P-gp), ABCC1 (MRP1), and ABCG2 (BCRP) - have mainly been attributed to the occurrence of MDR in cancer cells. One of the strategies to overcome MDR is to inhibit the efflux transporter function by small-molecule inhibitors. In this work, we investigated new chalcone- and flavone-based compounds for selective as well as broad-spectrum inhibition of the stated transport proteins. These include substituted chalcones with variations at rings A and B, and flavones with acetamido linker at position 3. The synthesized molecules were evaluated for their inhibitory potential against ABCB1, ABCC1, and ABCG2 in calcein AM and pheophorbide A assays. In further investigations with the most promising candidates from each class, we proved that ABCB1- and ABCG2-mediated MDR could be reversed by the compounds. Moreover, their intrinsic toxicity was found to be negligible in most cases. Altogether, our findings contribute to the understanding of ABC transport proteins and reveal new compounds for ongoing evaluation in the field of ABC transporter-mediated MDR.

Discovery of novel human inosine 5'-monophosphate dehydrogenase 2 (hIMPDH2) inhibitors as potential anticancer agents.

The enzyme inosine 5'-monophosphate dehydrogenase (IMPDH) catalyzes an essential step in the de novo biosynthesis of guanine nucleotides, and thus regulates the guanine nucleotide pool required for cell proliferation. Of the two isoforms, human IMPDH type 2 (hIMPDH2) is a validated molecular target for potential immunosuppressive, antiviral and anticancer chemotherapy. In search of newer hIMPDH2 inhibitors as potential anticancer agents, three novel series (A: 5-aminoisobenzofuran-1(3H)-one, B: 3,4-dimethoxyaniline and C: benzo[d]-[1,3]dioxol-5-ylmethanamine) were synthesized and evaluated for in vitro and cell-based activities. A total of 37 molecules (29-65) were screened for their in vitro hIMPDH2 inhibition, with particular emphasis on establishing their structure-activity relationship (SAR) trends. Eight compounds (hits, 30, 31, 33-35, 37, 41 and 43) demonstrated significant enzyme inhibition (>70% @ 10 µM); especially the A series molecules were more potent than B series (<70% inhibition @ 10 µM), while C series members were found to be inactive. The hIMPDH2 IC50 values for the hits ranged from 0.36 to 7.38 µM. The hits displaying >80% hIMPDH2 inhibition (30, 33, 35, 41 and 43) were further assessed for their cytotoxic activity against cancer cell lines such as MDA-MB-231 (breast adenocarcinoma), DU145 (prostate carcinoma), U87 MG (glioblastoma astrocytoma) and a normal cell line, NIH-3T3 (mouse embryonic fibroblast) using MTT assay. Most of the compounds exhibited higher cellular potency against cancer cell lines and notably lower toxicity towards NIH-3T3 cells compared to mycophenolic acid (MPA), a prototypical hIMPDH2 inhibitor. Two of the series A hits (30 and 35) were evaluated in human peripheral blood mononuclear cells (hPBMC) assay and found to be better tolerated than MPA. The calculated/predicted molecular and physicochemical properties were satisfactory with reference to drug-likeness. The molecular docking studies clearly demonstrated crucial interactions of the hits with the cofactor-binding site of hIMPDH2, further providing critical information for refining the design strategy. The present study reports the design and discovery of structurally novel hIMPDH2 inhibitors as potential anticancer agents and provides a guide for further research on the development of safe and effective anticancer agents, especially against glioblastoma.

Newer human inosine 5'-monophosphate dehydrogenase 2 (hIMPDH2) inhibitors as potential anticancer agents.

Human inosine 5'-monophosphate dehydrogenase 2 (hIMPDH2), being an age-old target, has attracted attention recently for anticancer drug development. Mycophenolic acid (MPA), a well-known immunosuppressant drug, was used a lead structure to design and develop modestly potent and selective analogues. The steep structure-activity relationship (SAR) requirements of the lead molecule left little scope to synthesise newer analogues. Here, newer MPA amides were designed, synthesised and evaluated for hIMPDH2 inhibition and cellular efficacy in breast, prostate and glioblastoma cell lines. Few title compounds exhibited cellular activity profile better than MPA itself. The observed differences in the overall biological profile could be attributed to improved structural and physicochemical properties of the analogues over MPA. This is the first report of the activity of MPA derivatives in glioblastoma, the most aggressive brain cancer.

Investigation of HSA as a biocompatible coating material for arsenic trioxide nanoparticles.

The anticancer properties of arsenic trioxide (As2O3) are accompanied by highly cytotoxic effects on normal cells. This necessitates developing modalities towards the targeted delivery of As2O3. Albumins, on account of their large structure and presence of several interacting groups, are ideal for encapsulating or carrying various drugs. In the present study, human serum albumin (HSA) was chosen as a coating agent to increase the biocompatibility of As2O3. An in situ chemical precipitation method was adopted for the synthesis of HSA-coated As2O3 nanoparticles (HSA-As2O3NPs) that were further characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), ultraviolet-visible (UV-vis) spectroscopy, inductively coupled plasma atomic emission spectrometry (ICP-AES), zeta potential and transmission electron microscopy (TEM). HSA-As2O3NPs were assessed for their biocompatibility using mouse fibroblast cells (NIH-3T3) and human dermal fibroblast (HDF) cells by a time- and dose-dependent cytocompatibility MTT assay. The safety of the HSA-As2O3 nanoparticles was assessed using haemolysis and blood cell aggregation studies. Molecular simulation studies provided evidence of interaction between HSA and As2O3. Herein, we report the development of a protein-based delivery system for As2O3 with improved biocompatibility.

Hybrids of Steroid and Nitrogen Mustard as Antiproliferative Agents: Synthesis, In Vitro Evaluation and In Silico Inverse Screening.

Hybrids of 16E-arylidene steroids and nitrogen mustard have been synthesized and evaluated for their in vitro cytotoxic activity to develop tissue specific antineoplastic agents from steroids. These hybrids displayed specificity towards leukemia cell lines, however somewhat reduced potency was observed in comparison with the earlier reported 16E-arylidene steroids. The in silico reverse screening experiments were employed to find out the probable pharmacological mechanism of these hybrids. Molecular docking studies suggested glucocorticoid receptors as a probable target for the antileukemic action of these steroid-nitrogen mustard hybrids.

Molecular docking prediction and in vitro studies elucidate anti-cancer activity of phytoestrogens.

AIM: The study is aimed at evaluating the chemosensitization and apoptotic effect of aglycone rich extracts of dietary phytoestrogens (derived from soybean and flaxseed) on estrogen receptor positive, MCF-7 and estrogen receptor negative, MDA-MB-231 cells. The extracts show potent activity on both the cell lines, hence, in silico studies have been carried out to find the possible reason for their activity. MAIN METHODS: MTT assay was carried to assess chemosensitization effect and activated caspase-3/7 activity was studied using flow-cytometry and western blotting. In silico studies were carried out using PharmMapper and the top hits were taken up for docking using the Schrödinger software. Top molecular targets were subjected to gene expression studies by qPCR and protein expression using Western blot analysis. KEY FINDINGS: This study reports the apoptotic activity and chemosensitization effect of the phytoestrogens. Molecular docking studies predict AKR1B1 (aldose reductase), HRAS (Harvey rat sarcoma) and GSTP1 (glutathione s-transferase pi) as potential molecular targets for genistein, daidzein and secoisolariciresinol, respectively. Gene and protein expression studies show down-regulation of AKR1BI, HRAS and GSTP1 by the extracts. SIGNIFICANCE: The qPCR and western blot analysis results support the computational analyses, and hence genistein, daidzein and secoisolariciresinol may be considered as good candidates for future development into potent inhibitors of the respective protein targets through medicinal chemistry optimization.

Cancer stem cell (CSC) inhibitors: a review of recent patents (2012-2015).

INTRODUCTION: Cancer stem cells (CSCs) mediate tumor initiation and maintenance. These cells are chemoresistant and possess characteristics such as self-renewal, pluripotency, plasticity and differentiation. They have aberrant or altered signaling pathways depending on tumor microenvironment, tumor type, etc. CSCs are responsible for highly aggressive and invasive form of the disease following chemo- and/or radiotherapy. Eliminating CSCs is likely to improve the survival rate in patients. Several anti-CSC strategies and associated targets have been proposed and validated till date. Areas covered: The main emphasis is on the patent applications/patents filed/granted in the last few years (2012-2015). The anti-CSC agents are discussed under two broad headings - small- and macromolecules. Different subclasses are further elaborated, e.g., kinase inhibitors, polypeptides, etc. Expert opinion: Clinical development of small- and macromolecular anti-CSC therapeutics is underway. Few of these agents act on validated targets such as kinases. Potential problems with these agents can be envisaged based on our understanding of target biology. Other issues governing the choice of small- versus macromolecules include druggability of the target, ease of its modulation and the presence of compensatory mechanisms. Drug repurposing can be attempted to discover newer anti-CSC drugs quickly.

Discovery of tetrahydrocarbazoles as dual pERK and pRb inhibitors.

The extracellular signal-regulated kinase (ERK) is one of the most important molecular targets for cancer that controls diverse cellular processes such as proliferation, survival, differentiation and motility. Similarly, the Rb (retinoblastoma protein) is a tumor suppressor protein and its function is to prevent excessive cell growth by inhibiting cell cycle progression. When the cell is ready to divide, pRb is phosphorylated, becomes inactive and allows cell cycle progression. Herein, we discovered a new series of tetrahydrocarbazoles as dual inhibitors of pERK and pRb phosphorylation. The in-house small molecule library was screened for inhibition of pERK and pRb phosphorylation, which led to the discovery of tetrahydrocarbazole series of compounds as potential leads. N-(3-methylcyclopentyl)-6-nitro-2,3,4,4a,9,9a-hexahydro-1H-carbazol-2-amine (1) is the dual inhibitor lead identified through screening, displaying inhibition of pERK and pRb phosphorylation with IC50 values of 5.5 and 4.8 µM, respectively. A short structure-activity relationship (SAR) study has been performed, which identified another dual inhibitor 9-methyl-N-(4-methylbenzyl)-2,3,4,4a,9,9a-hexahydro-1H-carbazol-2-amine (16) with IC50 values 4.4 and 3.5 µM for inhibition of pERK and pRb phosphorylation, respectively. This compound has a potential for further lead optimization to discover promising molecularly-targeted anticancer agents.