Cytotoxic activities of substituted 3-(3,4,5-trimethoxybenzylidene)-1,3-dihydroindol-2-ones and studies on their mechanisms of action

The synthesis of new trimethoxybenzylidene-indolinones is reported. Their cytotoxic activity was evaluated according to Developmental Therapeutics Program, National Cancer Institute, Bethesda, MD, drug screen protocols. The study of the mechanism of action suggests that inhibition of Nox4 in B1647 cells (acute myeloid leukemia) could contribute to the antiproliferative effect of some compounds. Moreover, inhibition of tubulin assembly was observed for the most cytotoxic compound, and the structural basis for this activity was delineated by binding models.

Substituted 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones and analogues: synthesis, cytotoxic activity, and study of the mechanism of action

The synthesis of substituted 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones and analogues is reported. Their cytotoxic activity was evaluated according to protocols available at the National Cancer Institute (NCI), Bethesda, MD. The action of selected compounds was examined for potential inhibition of tubulin assembly in comparison with the potent colchicine site agent combretastatin A-4. The most potent compounds also strongly and selectively inhibited the phosphorylation of the oncoprotein kinase Akt in cancer cells. The effect of the most interesting compounds was examined on the growth of HT-29 colon cancer cells. These compounds caused the cells to arrest in the G2/M phase of the cell cycle, as would be expected for inhibitors of tubulin assembly.

Substituted E-3-(3-indolylmethylene)-1,3-dihydroindol-2-ones with antitumor activity. In depth study of the effect on growth of breast cancer cells

The synthesis of new substituted E-3-(3-indolylmethylene)-1,3-dihydroindol-2-ones is reported. The antitumor activity was evaluated according to protocols available at the National Cancer Institute (NCI), Bethesda, MD. Structure-activity relationships are discussed. The action of selected compounds was investigated in MCF-7 breast cancer cells. The ability of these derivatives to inhibit cellular proliferation was accompanied by increased level of p53 and its transcriptional targets p21 and Bax, interference in the cell cycle progression with cell accumulation in the G2/M phase, and activation of apoptosis.

Antitumor activity of new substituted 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones and 3-(5-imidazo[2,1-b]thiadiazolylmethylene)-2-indolinones: selectivity against colon tumor cells and effect on cell cycle-related events

The synthesis of new 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones and 3-(5-imidazo[2,1-b]thiadiazolylmethylene)-2-indolinones is reported. The antitumor activity was evaluated according to the protocols available at the National Cancer Institute (NCI), Bethesda, MD. To investigate the mechanism of action of the most potent antitumor agent of this series, its effect on growth of HT-29 colon carcinoma cells was studied. Its ability to inhibit cellular proliferation was mediated by cell cycle arrest at the G2/M phase, accompanied by inhibition of ornithine decarboxylase (ODC), the limiting enzyme of polyamine synthesis, and followed by induction of apoptosis.

Antitumor activity of bis-indole derivatives

This paper reports the synthesis of compounds formed by two indole systems separated by a heterocycle (pyridine or piperazine). As a primary screening, the new compounds were submitted to the National Cancer Institute for evaluation of antitumor activity in the human cell line screen. The pyridine derivatives were far more active than the piperazine derivatives. For the study of the mechanism of action, the most active compounds were subjected to COMPARE analysis and to further biological tests including proteasome inhibition and inhibition of plasma membrane electron transport. The compound bearing the 5-methoxy-2-indolinone moiety was subjected to the first in vivo experiment (hollow fiber assay) and was active. It was therefore selected for the second in vivo experiment (human tumor xenograft in mice). In conclusion we demonstrated that this approach was successful, since some of the compounds described are much more active than the numerous, so far prepared and tested 3-indolylmethylene-2-indolinones.

Diphenidol-related diamines as novel muscarinic M4 receptor antagonists

A series of hydrochloride derivatives 2a-9a and quaternary ammonium derivatives 3b-9b of diphenidol have been synthesized and characterized in receptor binding and cellular functional assays versus human muscarinic M(1)-M(5) receptors expressed in CHO cells. Compound 8b, a methiodide derivative with a bipiperidinyl moiety and a second diphenidol framework, showed a potent and selective M(4) activity as competitive antagonist. Moreover 8b, acting as an allosteric modulator, was able to retard the dissociation rate of [(3)H]-N-methylscopolamine from CHO-M(4) cell membranes exposed to atropine. Taken together, these data suggest that 8b might open new avenues to the discovery of novel multivalent antagonists for the muscarinic receptors.

Chemiluminescent high-throughput microassay applied to imidazo[2,1-b]thiazole derivatives as potential acetylcholinesterase and butyrylcholinesterase inhibitors

The synthesis of a new series of imidazo[2,1-b]thiazole derivatives is described. They were tested as potential acetylcholinesterase and butyrylcholinesterase inhibitors by means of a chemiluminescent microassay. Although most of the new compounds did not show significant cholinesterase inhibition potency, three of them displayed selective antiacetylcholinesterase activity in the micromolar range.

Substituted E-3-(2-chloro-3-indolylmethylene)1,3-dihydroindol-2-ones with antitumor activity. Effect on the cell cycle and apoptosis

The synthesis and antitumor activity of new E-3-(2-chloro-3-indolylmethylene)1,3-dihydroindol-2-ones is described. They were studied at the National Cancer Institute, taking into consideration the 50% growth inhibitory power (pGI50), the cytostatic effect (pTGI = total growth inhibition), and the cytotoxic effect (pLC50). All the compounds were potent growth inhibitors, with mean pGI50 ranging from 5.26 to 7.72. They were also analyzed with NCI COMPARE algorithm. Further studies were dedicated to the effects on the cell cycle and apoptosis.

Synthesis and Antitumor Activity of Guanylhydrazones from 6-(2,4-Dichloro-5-nitrophenyl)imidazo[2,1-b]thiazoles and 6-Pyridylimidazo[2,1-b]thiazoles

The design and synthesis of antitumor imidazothiazole guanylhydrazones are reported. The compounds were submitted to NCI for testing. All but one were more active than methyl-GAG. A few compounds were selected for further studies in search of a possible mechanism of action. The results from these studies and a final search with the NCI COMPARE algorithm suggest that the guanylhydrazones described in this paper are acting through a novel mechanism of action.

Antitumor Activity of Substituted E-3-(3,4,5-Trimethoxybenzylidene)-1,3-dihydroindol-2-ones

The design and synthesis of anticancer E-3-(3,4,5-trimethoxybenzylidene)-1,3-dihydroindol-2-ones is reported. Strong COMPARE correlations among the cell line responses suggest that these compounds may be acting similarly through a combination of different mechanisms of action. The 5-methoxy derivative (2h) was the most active compound with a mean pGI50 of 6.34, and it is now under review by Biological Evaluation Committee of the National Cancer Institute for possible further studies.

Synthesis and chemiluminescent high throughput screening for inhibition of acetylcholinesterase activity by imidazo[2,1-b]thiazole derivatives

The synthesis of a new series of imidazo[2,1-b]thiazole derivatives is described. They were tested as acetylcholinesterase inhibitors by means of a chemiluminescent method suitable for high throughput screening. The compounds without quaternization had no appreciable inhibitory potency probably because they are poorly soluble in water. The corresponding quaternized compounds were good inhibitors with activity related to the spacer employed.

Antitumor Activity of New Substituted 3-(5-Imidazo[2,1-b]thiazolylmethylene)-2-indolinones and Study of Their Effect on the Cell Cycle

This paper reports the synthesis of a new series of 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones which were tested as potential antitumor agents at the National Cancer Institute. Two derivatives are now under review by BEC (Biological Evaluation Committee of NCI). To investigate the mechanism of action, the effect on cell cycle progression was studied by monitoring them in colon adenocarcinoma HT-29: both were able to block HT-29 in mitosis. 3-[(2,6-Dimethylimidazo[2,1-b]thiazol-5-yl)methylene]-5-chloro-2-indolinone was the most active compound.

Potential Antitumor Agents. 37. Synthesis and Antitumor Activity of Guanylhydrazones from Imidazo[2,1-b]thiazoles and from the New Heterocyclic System Thiazolo[2‘,3‘:2,3]imidazo[4,5-c]quinoline

This paper reports synthesis and antitumor activity of new guanylhydrazones from imidazo[2,1-b]thiazoles and from the new heterocyclic system thiazolo[2',3':2,3]imidazo[4,5-c]quinoline. The compounds were tested as potential antitumor agents at the National Cancer Institute. The effect of the guanylhydrazone of 2-chloro-6-(2,5-dimethoxy-4-nitrophenyl)imidazo[2,1-b]thiazole-5-carbaldehyde (41) was investigated, and it was found to be an inhibitor of Complex III of the mitochondrial respiratory chain and is able to induce apoptosis in the cell lines HT29 and HL60.

Effects of new ubiquinone-imidazo[2,1-b]thiazoles on mitochondrial complex I (NADH-ubiquinone reductase) and on mitochondrial permeability transition pore

In this work we describe the synthesis of a series of imidazo[2,1-b]thiazoles and 2,3-dihydroimidazo[2,1-b]thiazoles connected by means of a methylene bridge to CoQ(0). These compounds were tested as specific inhibitors of the NADH:ubiquinone reductase activity in mitochondrial membranes. The imidazothiazole system when bound to the quinone ring in place of the isoprenoid lateral side chain, may increase the inhibitory effect (with an IC(50) for NADH-Q(1) activity ranging between 0.25 and 0.96 microM) whereas the benzoquinone moiety seems to lose the capability to accept electrons from complex I as indicated by very low maximal velocity elicited by the compounds tested. Moreover the low rotenone sensitivity for almost all of these compounds suggests that they are only partially able to interact with the physiological ubiquinone-reduction site. The compounds were investigated for the capability of increasing the permeability transition of the inner mitochondrial membrane in isolated mitochondria. Unlike CoQ(0), which is considered a mitochondrial membrane permeability transition inhibitor, the new compounds were inducers.

N-Benzyl-2-chloroindole-3-carboxylic acids as potential anti-inflammatory agents. Synthesis and screening for the effects on human neutrophil functions and on COX1/COX2 activity

The synthesis of N-benzyl-2-chloroindole-3-carboxylic acids related to indomethacin is reported. These compounds were tested on in vitro human neutrophil activation. Some of them, more soluble in water, were tested to define the influence on prostaglandin biosynthesis via inhibition of cyclooxygenases (COX1 and COX2) by a chemiluminescent method suitable for fast screening. Several derivatives showed inhibitory effects and in some cases were more active than the parent compound.

Substituted E -3-(2-Chloro-3-indolylmethylene)1,3-dihydroindol-2-ones with antitumor activity

The synthesis and antitumor activity of a new series of E-3-(2-chloro-3-indolylmethylene)1,3-dihydroindol-2-ones is described. Several compounds were active on the primary test (three human cell lines) and entered the second level (60 human cell lines). All of them were potent growth inhibitors with GI(50) ranging from -5.32 to -7.27. Four are now under review by BEC (Biological Evaluation Committee of the NCI). The most potent antitumor derivatives were also evaluated as cardiotonic agents (in view of a possible coanthracyclinic activity). In order to find a possible mechanism of action their effects on cell cycle progression in an adenocarcinoma cell line (HT29) were tested, evidencing that these molecules are able to block HT29 in mitosis. The introduction of new substituents in the indolinone moiety while maintaining the same chloroindole portion generated interesting derivatives. 3-(2-Chloro-5-methoxy-6-methyl-3-indolylmethylene)5-hydroxy-1,3-dihydroindol-2-one was the most active of the whole series. It was more potent than vincristine against seven of the nine tumors considered. Moreover it was selective towards some cell lines such as MDA-MB-435 (breast), OVCAR-3 (ovarian) and SK-MEL-28 (melanoma). Even the introduction of a benzyl ring at the nitrogen of the chloroindole portion, gave rise to potent compounds.

Potential antitumor agents. 34.(1) Synthesis and antitumor activity of guanylhydrazones from imidazo[2,1-b]thiazoles and from diimidazo[1,2-a: 1,2-c] pyrimidine

We report the synthesis of new guanylhydrazones from imidazo[2,1-b]thiazoles and of a bis-guanylhydrazone from diimidazo[1,2-a:1,2-c]pyrimidine. The compounds were tested as potential antitumor agents at the National Cancer Institute. Two derivatives are now under review by BEC: one of these was also subjected to a test for positive inotropic activity in view of a possible coanthracyclinic activity. Tyrosine kinase receptors may be involved as molecular targets in the mechanism of action of the guanylhydrazones described.

Synthesis and antitumor activity of 1,5,6-substituted E-3-(2-chloro-3-indolylmethylene)-1,3-dihydroindol-2-ones

Synthesis and antitumor activity of new E-3-(2-chloro-3-indolylmethylene)-1,3-dihydroindol-2-ones are described. All compounds prepared were active in the primary test (three human cell lines) and entered the second level (60 human cell lines). The most active antitumor derivatives bear the same substituents in the chloroindole ring and are not CDK1 inhibitors. A COMPARE analysis showed that they could act as tubulin binders. In most cell lines, E-3-(2-chloro-5-methoxy-6-methyl-3-indolylmethylene)-1,3-dihydroindol-2-one was a growth inhibitor more potent than vincristine.

Synthesis and screening for antiacetylcholinesterase activity of (1-benzyl-4-oxopiperidin-3-ylidene)methylindoles and -pyrroles related to donepezil

The design, synthesis, and rapid evaluation of a new class of acetylcholinesterase (AChE) inhibitors related to donepezil are reported. A molecular dynamics simulation of the complex between AChE and one representative compound of the series showed a possible inhibitor binding mode in which favorable interactions are formed between the benzylpiperidinone moiety and some active-site residues. The biochemical evaluation of this newly synthesized series was performed using a chemiluminescent method suitable for high-throughput screening.

Synthesis and antitubercular activity of imidazo[2,1-b]thiazoles

A number of selected imidazo[2,1-b]thiazoles entered the screening at the Tuberculosis Antimicrobial Acquisition and Coordinating Facility (TAACF) and one of these compounds, 2-chloro-6-phenylimidazo[2,1-b]thiazole, showed antitubercular activity. On this basis we planned the synthesis of new analogues bearing a substituted ring at the 6 position. For one compound only (2-chloro-6-p-chlorophenylimidazo[2,1-b]thiazole) the 5-nitroso derivative was also prepared. The antitubercular activity of these compounds was compared with the known analogues lacking the chlorine at the 2 position. 5-Nitroso-6-p-chlorophenylimidazo[2,1-b]thiazole showed potent antitubercular activity.

Synthesis and antitumor activity of substituted 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones

The synthesis of 3-(5-imidazo]2,1-blthiazolylmethylene)-2-indolinones, analogs of compounds recently published, is described. The EIZ isomerism was studied by means of nuclear Overhauser effect experiments and X-ray crystallography. All the compounds were tested as potential antitumor agents. They were also tested as potential inhibitors of cyclin-dependent kinase 1 (CDK1), in order to determine if the antitumor activity was related to this mechanism of action. The results showed that under certain substitution conditions (5-methoxy group for the indole benzene ring and 2-methyl group for the imidazothiazole system), an interesting antitumor activity was found for some compounds. From the analysis of the antitumor data, 3-1(2,6-dimethylimidazo[2,1-bJ-thiazol-5-yl)methylenel-5-methoxy-2-indolinone was the most active of the whole series.

Imidazo[2,1 -b]thiazolylmethylene- and indolylmethylene-2-indolinones: a new class of cyclin-dependent kinase inhibitors. Design, synthesis, and CDK1/cyclin B inhibition

Compounds containing a 2-indolinone moiety linked to imidazothiazole and indole fragments were studied as cyclin-dependent kinase inhibitors. The activity of all the new derivatives was tested in vitro against CDK1/cyclinB and the selectivity towards two other kinases was determined for the most promising compounds. The binding mode of one representative compound was investigated by means of a three-dimensional model of the inhibitor-CDK1 complex. The work allowed us to identify (2-chloroindolyl)methylene-2-indolinone as a new lead of a class of CDK1/cyclinB inhibitors, whose potency can be improved by the introduction of suitable variations on the basic molecular skeleton.