Targeting telomerase for its advent in cancer therapeutics.

Telomerase has emerged as an important primary target in anticancer therapy. It is a distinctive reverse transcriptase enzyme, which extends the length of telomere at the 3' chromosomal end, and uses telomerase reverse transcriptase (TERT) and telomerase RNA template-containing domains. Telomerase has a vital role and is a contributing factor in human health, mainly affecting cell aging and cell proliferation. Due to its unique feature, it ensures unrestricted cell proliferation in malignancy and plays a major role in cancer disease. The development of telomerase inhibitors with increased specificity and better pharmacokinetics is being considered to design and develop newer potent anticancer agents. Use of natural and synthetic compounds for the inhibition of telomerase activity can lead to an opening of new vistas in cancer treatment. This review details about the telomerase biochemistry, use of natural and synthetic compounds; vaccines and oncolytic virus in therapy that suppress the telomerase activity. We have discussed structure-activity relationships of various natural and synthetic telomerase inhibitors to help medicinal chemists and chemical biology researchers with a ready reference and updated status of their clinical trials. Suppression of human TERT (hTERT) activity through inhibition of hTERT promoter is an important approach for telomerase inhibition.

Ligand based design and synthesis of pyrazole based derivatives as selective COX-2 inhibitors.

The design and synthesis of novel pyrazole based derivatives has been carried out using the ligand based approach like pharmacophore and QSAR modelling of reported pyrazoles from the available literature to investigate the chemical features that are essential for the design of selective and potent COX-2 inhibitors. Both pharmacophore and QSAR models with good statistical parameters were selected for the design of the lead molecule. Also by exploiting the chemical structures of selective and marketed COX-2 inhibitors, celecoxib and SC-558 were used in designing the molecules which are used in the treatment of inflammation and related disorders. The therapeutic action of the Non-Steroidal Anti-inflammatory Agents (NSAIDs) is based primarily on the COX-2 inhibition. With this background we have synthesized some azomethine derivatives of 3-methyl-1-substituted-4-phenyl-6-[{(1E)-phenylmethylene}amino]-1,4-dihydro pyrano[2,3-c]pyrazole-5-carbonitrile 6(a-o) and were characterized by 1HNMR, 13CNMR and Mass spectral techniques. All the synthesized pyrazole derivatives were tested for in vitro membrane stability property in both COX-1 & COX-2 inhibition studies and in vivo anti-inflammatory activity by carrageenan induced rat paw edema model. Among them, compound 6k showed very good activity by in vivo anti-inflammatory activity with 0.8575 mmol/kg as ED50. Similarly compounds 6m, 6o, 6i and 6h exhibited comparable anti-inflammatory activity to standard drugs. Also the active compounds were further screened for ulcerogenic activity and were found be safer with less ulcer index compared to the marketed drugs like aspirin, ibuprofen and celecoxib.

Synthesis of novel gefitinib-based derivatives and their anticancer activity.

Drug latentiation is a process of modifying a drug molecule structurally to improve its binding affinity as well as increasing the drug-receptor interactions and potentiate its therapeutic potential. In the quest for discovering more potent epidermal growth factor receptor (EGFR) inhibitors, gefitinib-based derivatives were designed by simple structural modification at the secondary amine of gefitinib by N-alkylation. Three gefitinib derivatives (gefitinib-NB, -NP, and -NIP) were synthesized by N-alkylation and phase transfer catalysis. Structural characterization, physicochemical parameters such as solubility, log P, and p K a were determined. Molecular docking studies were carried out to investigate the binding interactions at the active site. Further drug-bovine serum albumin (BSA) protein and drug-calf thymus (CT) DNA interactions were performed to understand the pharmacokinetics of the synthesized derivatives. All the compounds were screened for preliminary in vitro cytotoxic activity against A549, A431 lung, and MDA-MB-231 breast cancer cell lines by MTT assay. The gefitinib-NP and gefitinib-NB derivatives exhibited strong cytotoxic activity compared with gefitinib. They also showed higher drug-BSA and drug-DNA interactions. Molecular docking studies showed the orientation and binding interactions with the EGFR as well as with BSA and CT DNA. The results establish a strong correlation between the experimental and molecular docking studies. EGFR inhibition studies were also carried out for the derivatives and we identified the NP derivative of gefitinib as a potential lead compound. The gefitinib-based derivatives reported herein are cytotoxic agents and can be tested for further pharmacokinetic profiles and toxicity studies which might be helpful for designing more potent gefitinib-based derivatives in the future.

Study of Combinatorial Drug Synergy of Novel Acridone Derivatives With Temozolomide Using in-silico and in-vitro Methods in the Treatment of Drug-Resistant Glioma.

Drug resistance is one of the critical challenges faced in the treatment of Glioma. There are only limited drugs available in the treatment of Glioma and among them Temozolomide (TMZ) has shown some effectiveness in treating Glioma patients, however, the rate of recovery remains poor due to the inability of this drug to act on the drug resistant tumor sub-populations. Hence, in this study three novel Acridone derivative drugs AC2, AC7, and AC26 have been proposed. These molecules when combined with TMZ show major tumor cytotoxicity that is effective in suppressing growth of cancer cells in both drug sensitive and resistant sub-populations of a tumor. In this study a novel mathematical model has been developed to explore the various drug combinations that may be useful for the treatment of resistant Glioma and show that the combinations of TMZ and Acridone derivatives have a synergistic effect. Also, acute toxicity studies of all three acridone derivatives were carried out for 14 days and were found safe for oral administration of 400 mg/kg body weight on albino Wistar rats. Molecular Docking studies of acridone derivatives with P-glycoprotein (P-gp), multiple resistant protein (MRP), and O6-methylguanine-DNA methyltransferase (MGMT) revealed different binding affinities to the transporters contributing to drug resistance. It is observed that while the Acridone derivatives bind with these drug resistance causing proteins, the TMZ can produce its cytotoxicity at a much lower concentration leading to the synergistic effect. The in silico analysis corroborate well with our experimental findings using TMZ resistant (T-98) and drug sensitive (U-87) Glioma cell lines and we propose three novel drug combinations (TMZ with AC2, AC7, and AC26) and dosages that show high synergy, high selectivity and low collateral toxicity for the use in the treatment of drug resistant Glioma, which could be future drugs in the treatment of Glioblastoma.

E-drug delivery: a futuristic approach.

Drug delivery systems are undergoing technology changes to enhance patient comfort and compliance. Electronic drug delivery (E-drug delivery) systems are being developed to regulate drug dose delivery by easy monitoring of doses, especially in chronic and age-related diseases. E-drug delivery can monitor the correct dose of anesthesia, could be used in GI tracking by E-capsules, in epilepsy, insulin drug delivery, cardiac ailments and cancer therapy. Wearable E-drug delivery systems and Smartphone apps are the new additions. In this review, the authors attempt to highlight how technology is changing for improved patient comfort and treatment. Personalized drug delivery systems will be the future treatment process in healthcare.

Synthesis of 2-methyl N10-substituted acridones as selective inhibitors of multidrug resistance (MDR) associated protein in cancer cells.

A series of N10-substituted-2-methyl acridone derivatives are synthesized and are examined for its ability to reverse P-glycoprotein (P-gp) mediated multidrug resistance (MDR) in breast cancer cell lines MCF-7 and MCF-7/Adr. The structural requirement of in-vitro anti-cancer and reversal of drug resistance are studied. The results showed that compound 16 with four carbon spacer exhibited promising in-vitro anti-cancer and reversal of drug resistance in comparison to the other analogues.

Design, synthesis, biological evaluation, molecular docking and QSAR studies of 2,4-dimethylacridones as anticancer agents.

Drug resistance in cancer is an unmet medical challenge and a major drawback for the failure of many chemotherapeutic drugs. Search for targeted, effective drug with minimum toxicity is an urgent need. Acridone which is an alkaloid derivative has been attributed as molecule in reversing drug resistance in cancer cells for a long time now. In the present investigation, an attempt has been made to explore the chemosensitizing ability of 2,4-dimethylacridones with alkyl side chain containing terminally substituted tertiary amino groups. Considering the structural features required for the MDR reversal activity, acridone derivatives have been synthesized with propyl and butyl side chain containing morpholinyl, piperidinyl, N-methylpiperazinyl, N,N-diethylamino, N-diethanolamino, N-[(ß-hydroxylethyl)]piperazino at the terminus of the alkyl side chain. cLogP values for the synthesized compounds ranged from 2.96 to 4.72 for the propyl derivatives and 3.41 to 5.15 for the butyl derivatives. All the compounds were screened against breast cancer sensitive MCF7 and resistant MCF7/ADR cell lines. Compounds 12e and 12f have shown better cytotoxicity profiles with IC50 of 4 ± 0.05 and 2 ± 0.03 µM against MCF7 cells, 5.21 ± 0.13 and 2.56 ± 0.05 µM against MCF7/ADR cells. Photolabelling studies with [3H]-azidopine and molecular docking studies have identified that 2,4-dimethylacridones have potential to modulate the P-gp mediated multidrug resistance. Docking studies identified that compounds have shown favorable interactions with P-gp. QSAR equation was derived for cytotoxicity vs molecular descriptors of acridone derivatives. Best models with good predictive ability have been generated with very high square correlation coefficient (R2) values of 0.889, 0.964 and 0.983.

Acridone-pyrimidine hybrids- design, synthesis, cytotoxicity studies in resistant and sensitive cancer cells and molecular docking studies.

Hybrid systems of acridones with substituted pyrimidines were designed with an objective of discovering next generation anticancer agents targeting multiple mechanisms in the cancer cell. Hybrid compounds were synthesized by simple and convenient methods in the lab, characterized by NMR and Mass spectral methods and screened for cytotoxicity against A549 (lung), Hela (cervical), MCF7 (breast) and MDA-MB-231 (breast) cancer cell lines respectively. Evaluation of compounds for cell proliferation identified active compounds 11b, 11d and 11h against MCF7, MDA-MB-231 and A549 cell lines. Further absorption titrations with CT-DNA and gel electrophoresis identified that hybrid molecules displayed anticancer activity partly by DNA intercalation. Also further results of western blotting assay with Akt kinase identified that hybrid compounds have the ability to inhibit the Akt kinase activity and induce apoptosis, with ABCC1 suggests that active compounds too have the ability to modulate multidrug resistance (MDR) associated with ABCC1/MRP1. Selective Akt1 kinase assay have identified 11a, 11b, 11d and 11h as potential inhibitors. Molecular docking studies identified the orientation and binding interactions at the active site of Akt1 and DNA. Compounds 12e and 12f have shown good cytotoxicity profile against lung cancer cell lines of sensitive and resistant type. Acute toxicity study of compound 12f at the dose of 5000 mg/kg has identified no signs of clinical toxicity. Prediction of ADMET properties and oral toxicity of the drug likeness features of new hybrid systems were carried out using software's. This experimental data suggests that hybrid systems of acridone with substituted pyrimidines can be taken as a lead for the design of efficient inhibitors and active compounds which can be taken up for further studies.

Targeting calmodulin in reversing multi drug resistance in cancer cells.

Calmodulin is a Ca2+ binding protein found in many eukaryotic cells. It is one of the most important intracellular mediators of Ca2+-dependant signaling in eukaryotic cells. It regulates diverse processes including mitosis, muscle contraction and nucleotide metabolism by modulating the activity of at least 30 different target enzymes in a calcium-dependant manner. Calmodulin plays an important role in the regulation of processes, such as the assembly and disassembly of microtubules by controlling protein kinase activities, by exerting an indirect influence upon a wide variety of cellular processes. It is observed that multi-drug resistant cells have a greater intracellular concentration of calcium than non-resistant cells which contributes to their increased sensitivity to calmodulin antagonism compared with that of non resistant cells. Calmodulin mediated processes can be effectively inhibited by a variety of pharmacological agents of different chemical structures, eg:The calcium channel blocker verapamil and antipsychotic drugs like the Phenothiazines. Many bioisosteres of phenothiazines like phenoxazines and acridones have been prepared and these have also shown very good calmodulin antagonism. These calmodulin antagonists have been shown to modulate multi-drug resistance (MDR) in cancer cells. This review highlights concepts of identification and optimization of new inhibitors of calmodulin in reversing MDR in cancer cells.

Sensitization of multidrug resistant (MDR) cancer cells to vinblastine by novel acridones: correlation between anti-calmodulin activity and anti-MDR activity.

Multidrug resistance (MDR) of cancer cells remains to be an important cause of chemotherapy failure. Search for the new MDR reversal agents is still an unceasing challenge for the scientists. In an attempt to find clinically useful modulators of MDR, a series of 19 N(10)-substituted-2-bromoacridones has been synthesized. Parent compound 1, prepared by the Ullmann condensation of o-chlorobenzoic acid and p-bromoaniline, undergoes N-alkylation in the presence of a phase transfer catalyst. N-(omega-Chloroalkyl) analogues were subjected to iodide catalyzed nucleophilic substitution reaction with various secondary amines to get the products 3-10 and 12-19, which increased the uptake of vinblastine (VLB) in MDR KBCh(R)-8-5 cells to a greater extent (1.25 to 1.9-fold) than did a similar concentration of the standard modulator, verapamil (VRP). Results of the efflux experiment showed that each modulator significantly inhibited the efflux of VLB, suggesting that they may be competitors for P-gp. All the compounds effectively compete with [(3)H] azidopine for binding to P-gp, pointed out this transport membrane protein as their likely site of action. Compounds at IC(10) were evaluated for their efficacy to modulate the cytotoxicity of VLB in KBCh(R)-8-5 cells and found that the modulators enhanced the cytotoxicity of VLB by 3.8 to 34-fold. The study on the structure-activity relationship revealed that substitution of hydrogen atom at position C-2 in acridone nucleus by a bromine atom increased the cytotoxic and anti-MDR activities. The ability of acridones to inhibit calmodulin-dependent cyclic AMP phosphodiesterase has been determined and the results have shown a strong positive correlation between anti-calmodulin activity and cytotoxicity in KBCh(R)-8-5 cells or anti-MDR activity.

Chemosensitizing acridones: in vitro calmodulin dependent cAMP phosphodiesterase inhibition, docking, pharmacophore modeling and 3D QSAR studies.

Calmodulin inhibitors have proved to play a significant role in sensitizing MDR cancer cells by interfering with cellular drug accumulation. The present investigation focuses on the evaluation of in vitro inhibitory efficacy of chloro acridones against calmodulin dependent cAMP phosphodiesterase (PDE1c). Moreover, molecular docking of acridones was performed with PDE1c in order to identify the possible protein ligand interactions and results thus obtained were compared with in vitro data. In addition an efficient pharmacophore model was developed from a set of 38 chemosensitizing acridones effective against doxorubicin resistant (HL-60/DX) cancer cell lines. Pharmacophoric features such as one hydrogen bond acceptor, one hydrophobic region, a positive ion group and three aromatic rings i.e., AHPRRR have been identified. Ligand based 3D-QSAR was also performed by employing partial least square regression analysis.

Cytotoxicity studies of some novel fluoro acridone derivatives against sensitive and resistant cancer cell lines and their mechanistic studies.

A series of novel N(10)-substituted acridone derivatives bearing alkyl side-chain with tertiary amine groups at the terminal position were evaluated for their in vitro cytotoxic effects against drug sensitive and resistant cancer cell lines. All the molecules were designed on the basis of hydrogen bond acceptors, carbonyl, fluoro groups with precise spatial separation and structural features of lipophilicity, positive charge at neutral pH and presence of aromatic rings. The in vitro cytotoxic effects in comparison with reference drugs doxorubicin (DX) and C(1311) against cancer cell lines SW 1573, SW 1573 2R 160 (Pg-P expressing) which are non-small cell lung cancer cells, human embryo kidney cells HEK 293, HEK 293 MRP4, HEK 293 MRP5i, human promyelocytic leukemia sensitive cell line HL-60, including its multidrug cross-resistant of two main (P-gp and MRP) phenotype sublines vincristine resistant HL-60/VINC and doxorubicin resistant HL-60/DX cancer cell lines are presented. Compounds 14, 15 and 16 exhibited highest cytotoxicity among the derivatives. On the other hand, the in vitro cytotoxic activity of compound 14 (with butyl side-chain and tertiary amino group ß-hydroxy ethyl piperizine) against resistant cancer cell lines indicate that it might be a promising new hit for further development as an anti-MDR agent. The non-covalent interaction of these molecules with DNA duplexes have been investigated by ESI-MS technique. The results indicate, these acridone derivatives interact with duplex DNA by intercalation, possesses higher affinity to GC than AT base pairs of the DNA and they could not interact non-covalently with the minor grooves of the DNA. The ability of acridones to inhibit calmodulin dependent cAMP phosphodiesterase has been determined. The results suggest that acridones inhibit the Ca(2+)/calmodulin stimulated cAMP-phosphodiesterase activity and have no direct effects on the enzyme itself and a strong correlation between calmodulin inhibition and cytotoxicity against HL-60/VINC and HL-60/DX MDR cancer cell lines.

Design of new drug molecules to be used in reversing multidrug resistance in cancer cells.

Over the past two decades, a number of chemical entities have been investigated in the continuing quest to reverse P-glycoprotein (P-gp) mediated multidrug resistance (MDR) in cancer cells and some have undergone clinical trials, but currently none are in clinical use. Unfortunately, most of these agents suffer clinically from their intrinsic toxicity or from undesired effects on the pharmacokinetics of the accompanying anti-cancer drugs. An acridonecarboxamide (GF120918), Imidazo acridone (C(1311)) and timethylene acridone derivative 1,3-bis(9-oxoacridin-10-yl)-propane (PBA) have already been shown to be among the group of compounds known to modify P-gp mediated MDR in cancer. In the recent past it has been identified that various N(10)-substituted acridones can reverse the multidrug resistance (MDR) in cancer by selectively inhibiting the multidrug resistance associated protein (MRP) and calmodulin dependent cyclic AMP phosphodiesterase. This article envisages the various drugs being developed for treating MDR in cancer cells and especially the acridone derivatives which are being developed by the author.

Chloro acridone derivatives as cytotoxic agents active on multidrug-resistant cell lines and their duplex DNA complex studies by electrospray ionization mass spectrometry.

We report herein in vitro anti-proliferative activity and duplex DNA complex studies of a series of N10-substituted acridone derivatives. All the molecules have been designed on the basis of the presence of specific recognition patterns consisting of hydrogen bond acceptors (or electron donors), carbonyl, chloro groups with precise spatial separation and structural features (lipophilicity, positive charge at neutral pH and presence of aromatic rings). The in vitro cytotoxic effects have been demonstrated against human promyelocytic leukemia sensitive cell line (HL-60), including its multidrug cross-resistance of two main (P-gp and MRP) phenotype sublines vincristine-resistant (HL-60/VINC) and doxorubicin-resistant (HL-60/DX) cancer cell lines. Compound 4 showed very good activity against sensitive and resistant cell lines. The noncovalent complexes of these molecules with DNA duplex has been investigated in gas phase by using a fast, robust and sensitive electrospray ionization mass spectrometry (ESI-MS) technique. Equilibrium association constants (K1) and percentage of intact complexes were determined. The combined results show that these acridone derivatives interact with DNA duplex by intercalation between the base pairs, possess higher affinity to GC than AT base pairs of the DNA and they could not interact noncovalently with the minor grooves of the DNA in solution-free gas phase. Examination of the relationship between lipophilicity and cytotoxic properties of acridone derivatives showed a poor correlation. The in vitro cytotoxic studies in resistant cancer cell lines of compound 4 showed that it might be a promising new hit for further development of anti-MDR agent.